Ch40 Management and Resuscitation of the Critical Patient.docx

Chapter 40 Management and Resuscitation of the Critical Patient Unit Summary Expertise in critical thinking and decision making are essential tools to use when you are confronted with a critical patient. This process involves conducting a rapid assessment, providing lifesaving treatment, and developing a differential field diagnosis. This chapter discusses the approach that you should take when you are confronted with a critical patient. National EMS Education Standard Competencies Shock and Resuscitation Integrates a comprehensive knowledge of the causes and pathophysiology into the management of shock, respiratory failure or arrest with an emphasis on early intervention to prevent arrest. Knowledge Objectives List examples of peri-arrest conditions that critical patients can present within the field. (p 1882) Describe the process of determining a differential diagnosis in the field assessment of a critical patient. (pp 1882–1883) Discuss the rapid decision making involved in the assessment and management of a critical patient. (p 1883) List examples of bias that can affect your critical decision making. (pp 1883–1884) Describe the body’s physiologic response to changes in perfusion. (pp 1886–1889) Discuss the pathophysiology of shock and peri-arrest situations. (pp 1889–1895) Describe the effects of decreased perfusion at the capillary level. (pp 1892–1893) Define shock based on aerobic and anaerobic metabolism. (pp 1890–1892) Relate pulse pressure changes to perfusion status. (pp 1886–1889, 1896) Relate orthostatic vital sign changes to perfusion status. (p 1896) Predict shock based on mechanism of injury. (p 1895) Discuss the progression of shock. (pp 1895–1897) Discuss the pathophysiologic changes associated with compensated shock. (p 1896) Discuss the assessment findings associated with compensated shock. (pp 1897–1899) Identify the need for intervention and transport of the patient with compensated shock. (p 1898) Discuss the treatment plan and management of compensated shock. (pp 1900–1903) Discuss the pathophysiologic changes associated with decompensated shock. (p 1896) Discuss the assessment findings associated with decompensated shock. (pp 1897–1899) Identify the need for intervention and transport of the patient with decompensated shock. (p 1898) Discuss the treatment plan and management of the patient with decompensated shock. (pp 1900–1903) Differentiate between compensated and decompensated shock. (pp 1895–1897) Discuss the assessment findings associated with shock and the peri-arrest situations. (pp 1897–1899) Identify the need for intervention and transport of the patient with shock or other peri-arrest situations. (pp 1903–1911) Discuss the treatment plan and management of shock and other peri-arrest situations. (pp 1903–1911) Describe the pathophysiology, assessment, and management of specific types of shock, including cardiogenic, obstructive, distributive, and hypovolemic shock. (pp 1903–1911) Skills Objectives Defend the importance of teamwork, experience, and practice in preparation to manage the critical patient. (p 1881) Demonstrate rapid decision making based on differential field diagnosis of the critical patient with a peri-arrest condition. (pp 1884–1885) Demonstrate the management of shock. (pp 1901–1902, Skill Drill 1) Readings and Preparation Review all instructional materials including Chapter 40 of Nancy Caroline’s Emergency Care in the Streets, Seventh Edition, and all related presentation support materials. Support Materials • Lecture PowerPoint presentation • Case Study PowerPoint presentation Enhancements • Direct students to visit the companion website to Nancy Caroline’s Emergency Care in the Streets, Seventh Edition, at http://www.paramedic.emszone.com for online activities. Content connections: Nearly every chapter contains significant information of management of critical patients. Review as many as possible or at a minimum have notes available. Teaching Tips Reinforcing the use of the five step process for communicating intutive decision as proposed by Karl Weick will help students in their decision-making process. Use this process during your presentation of this material as much as possible to demonstrate the importance. Unit Activities Writing activities: Assign students to prepare a written report on communication bias, to include all items found in this chapter. Student presentations: Have students present their written reports. Alternatively, have students present the results of their group project. Group activities: Divide students into groups. Give each group a somewhat vague scenario involving a critical patient. Using the five step process for communicating intutive decision as proposed by Karl Weick, allow the students to communicate their findings and intuitive sense. Visual thinking: Have students prepare a drawing of the shock cycle to differentiate between compensated and decompensated shock. Pre-Lecture You are the Medic “You are the Medic” is a progressive case study that encourages critical-thinking skills. Instructor Directions Direct students to read the “You are the Medic” scenario found throughout Chapter 40. • You may wish to assign students to a partner or a group. Direct them to review the discussion questions at the end of the scenario and prepare a response to each question. Facilitate a class dialogue centered on the discussion questions and the Patient Care Report. • You may also use this as an individual activity and ask students to turn in their comments on a separate piece of paper. Lecture I. Introduction A. Expertise in critical thinking and decision making are essential when working with a critical patient. 1. This involves: a. Conducting a rapid assessment b. Providing lifesaving treatment c. Developing a differential field diagnosis i. Short list of the potential causes 2. If a patient is in critical condition, you must be well trained to make the right decision, use time appropriately, and provide the right care. a. Patient may need to be transported for appropriate care. b. May also involve: i. Having the right equipment ii. Using the right resources iii. Crew management iv. Leadership skills v. Prioritization vi. Compliance with protocols vii. Working with public safety personnel and family members 3. Managing critical patients may involve being confronted with premorbid or periarrest conditions. II. Developing Critical Thinking and Decision-Making Abilities A. Excellent decision making comes with experience. 1. Students must acquire entry-level knowledge and skills with guided experience. a. Training is developed to create entry-level paramedics b. Internships help pull together: i. Didactic ii. Lab skills iii. Clinical experiences 2. State and national certification/registration/licensure follows. B. Critical patients 1. While caring for critical patients you will be confronted with: a. Premorbid conditions b. Major trauma c. Patients in the periarrest period 2. Periarrest period: Period just before or just after cardiac arrest a. Care must be taken to prevent progression or regression into cardiac arrest. b. Examples include: i. Unstable dysrhythmias ii. Shock iii. Syncope iv. Myocardial ischemia v. Heart failure 3. Premorbid conditions: Conditions that precede the onset of a disease a. Disease: Life-threatening trauma or medical condition that need to be rapidly identified and managed b. Sorted into: i. Those occurring in presumed to be healthy adults ii. Those occurring in unhealthy adults 4. Many adult patients have preexisting conditions putting them in the critical patient category. a. Patients with trauma such as: i. Full-thickness burn over 15-20% of the total body surface area ii. Head, chest, or abdomen involved with hemorrhage leading to shock b. Acute coronary syndrome (ACS) c. Congestive heart failure (CHF) d. Renal failure e. Uncontrolled hypertension f. Uncontrolled diabetes g. Obesity h. Electrolyte imbalance i. Electrocution j. Drowning or submersion k. Hypothermia l. Drug toxicity m. Stroke n. Near-fatal asthma o. Anaphylaxis p. Pulmonary embolism C. The EMS approach to diagnosis 1. Critical patients often complain about altered mental status, difficulty breathing, severe pain, and chest pain. a. Follow a standard approach to determine a field diagnosis. b. Consider and rule out different conditions. i. Leads to a differential diagnosis 2. To consider the differential diagnosis for a patient with an altered mental status, you may use the “M-T SHIP” acronym. a. M: Medication overdose/noncompliance, metabolic causes b. T: Tumor, trauma, toxins c. S: Seizures, stroke d. H: Hypoxia, hyperthermia/hypothermia, hyperglycemia/hypoglycemia, hypertensive crisis, hypovolemia, hyperkalemia/hypokalemia e. I: Infection and uremia f. P: Psychiatric or behavioral disorders 3. To consider the differential diagnosis for a patient with chest pain, consider: a. Ischemic chest pain indicating a possible cardiac condition b. Gastrointestinal (GI) system causes i. Heartburn ii. Esophageal spasm iii. Hiatal hernia iv. Gallbladder or pancreas problems c. Musculoskeletal problems i. Costochondritis ii. Sore muscles iii. Injured ribs iv. Pinched nerve d. Respiratory causes i. Pulmonary embolism ii. Pleurisy iii. Pneumothorax iv. Asthma e. Panic attack f. Shingles g. Cancer in the chest 4. Your experience will be your guide in determining serious problems. D. The role of intuition in critical decision making 1. Intuition comes with experience and is hard to teach. a. Described as pattern recognition and matching based on previous experience b. Can be used to “up-triage” the patient rather than “down-triage” i. If instinct tells you the patient is more serious than he or she seems, treat as such. ii. If instinct tells you otherwise, investigate the complaint. 2. Pattern recognition in one field doesn’t mean you are equally as good in other fields. a. Don’t misuse analogies and make decisions based on intuition that draws on incorrect experiences. 3. Decisions based on intuition can make communication difficult. a. Team members may have a hard time staying on board with the thought process. b. Organizational scholar Karl Weick came up with a five-step process for communicating intuitive decisions. i. Here is what I think we are dealing with. ii. Here is what I think we should do. iii. Here is why. iv. Here is what we should keep our eyes on. v. Now talk to me. Are there any other concerns? E. Bias to decision making 1. Biases can lead to faulty decision making. a. Confrontation bias: Tendency to gather and rely on information that confirms your views and avoids or downplays information that does not confirm your preexisting hypotheses b. Anchoring bias: Allowing an initial reference point to distort your estimates i. Brain allows you to begin at a reference point and adjust from there. ii Often seen in financial negotiations and price setting 2. Be mindful about making a misjudgment based on overconfidence. a. Search for information refuting the differential diagnosis. b. Look at all angles of the problem. 3. When treating a patient with classic presentations of a specific condition, don’t assume the patient has the condition before obtaining information. a. Same principle applies in patients who don’t present with classic signs and symptoms b. Don’t prematurely jump to conclusions when assessing a critical patient. III. A Snapshot of Critical Decision Making A. Scenario: You have been dispatched to the home of a 62-year-old woman complaining of pressure in the center of her chest. 1. Scene appears safe but you pay attention to the environment you are entering. 2. You introduce yourself to the patient and ask about chief complaint. a. The patient states her physician determined that her chest pain was caused by stress and acid reflux. i. Antacids have not alleviated crushing sensation beneath her breastbone. (a) Pain is accompanied by nausea and tingling in her right arm. 3. Your partner places her on oxygen using a non-rebreathing mask and obtains her vital signs. 4. You give her four baby aspirin to chew once you determine she has no cardiac history, no allergies, and is not taking an anticoagulant. 5. You go through the OPQRST mnemonic to help elaborate on chest pain. 6. It is determined that she is tachycardic and has slight hypertension. a. You listen to her lung sounds, and your partner obtains a 12-lead ECG. i. There is a slight crackling in the bases of her lungs. b. Your partner transmits the results to the nearest hospital with a coronary catheterization lab. 7. The patient has ST-segment elevations in three contiguous leads (II, III, AVF). a. She fits the STEMI protocol for an inferior wall myocardial infarction. b. Criterion for percutaneous coronary intervention is within a 90-minute window. c. Your partner starts an IV line to start morphine sulfate and metoprolol. d. You determine that it is best to take her to the hospital 2 miles beyond closest hospital because it has a coronary catheterization lab. 8. When the patient is lifted from the couch to the stairchair, she passes out. a. The ECG changes from a sinus tachycardia to ventricular fibrillation. b. You and your partner move the patient to the floor. c. You begin chest compressions while the defibrillator pads are placed on the patient. d. An oropharyngeal airway is inserted and bag-mask ventilations are started with supplemental oxygen. e. With the pads in place, compressions are stopped and the first shock at 200 joules is delivered. i. CPR compressions resume. 9. You need to make sure personnel perform specific tasks at the right time, which includes: a. Getting the mechanical CPR device ready to deploy with no interruption for more than 10 seconds b. Ensuring BLS ventilations are effective, and switching to the automatic transport ventilator with the impedance threshold device c. Starting an IV line to administer 1 mg of epinephrine 1:10,000 every 3 minutes until pulse returns. d. Ensuring a fresh person will supply chest compressions for the second 2 minutes e. Drawing up 300 mg of amiodarone because an antidysrhythmic will need to be administered f. Reanalyzing and reshocking the patient at 2-minute intervals 10. After the third shock, the patient has rhythm but no pulse. a. CPR continues b. Antidysrhythmic is administered. 11. You take a moment to consider causes of cardiac arrest. a. You consider reversible causes. i. No signs of trauma or symptoms of GI bleeding ii. Systolic blood pressure was slightly high. (a) Not likely hemorrhaging iii. Not a diabetic and initially was alert (a) Low levels of glucose are unlikely. iv. No signs of respiratory distress and not cold to the touch (a) Pulmonary embolus and hypothermia not likely. v. ST elevation MI (STEMI) and vague presentation in elderly women (a) Likely a massive AMI or coronary thrombosis 12. After the fourth shock, the patient wakes up. a. You assure her all her needs are taken care of b. Crew members are assigned to package and carry the patient. c. One medic starts an amidarone drop and prepares a mild sedative. 13. Once en route, you contact the ED to update staff and another 12-lead ECG is transmitted. a. You reassess vital signs, document the incident, and discuss the situation with the patient. 14. Because the ECG was initially transmitted, the patient is admitted directly to the catheterization lab. IV. Shock: The Critical Patient Evolving in Front of You A. Shock is a state of collapse and failure of the cardiovascular system where blood circulation slows and eventually ceases. 1. Leads to insufficient perfusion of organs and tissues 2. Normal compensatory mechanism to maintain systolic blood pressure and brain perfusion during distress a. Can accompany a broad spectrum of events 3. If not treated promptly, shock will injure the body’s vital organs and lead to death. V. Anatomy and Physiology of Perfusion A. Perfusion is the circulation of blood within an organ or tissue in adequate amounts to meet the cells’ needs for oxygen, nutrients, and waste removal. 1. Requires having a working cardiovascular system 2. Requires adequate gas exchange in the lungs, glucose in the blood, and waste removal 3. The cardiovascular system requires three components to keep the blood moving: a. Functioning pump (heart) b. Adequate fluid volume (blood and body fluids) c. Intact system of tubing capable of reflex adjustments in response to changes in pump output and fluid volume (blood vessels) 4. The heart’s contractility allows it to increase or decrease the volume of blood pumped with each contraction (stroke volume [SV]). a. The heart can vary the speed at which it contracts by raising or lowering the pulse rate. b. Cardiac output (CO): Volume of blood that the heart can pump per minute i. Heart must have adequate strength (a) Determined by heart muscle’s ability to contract (myocardial contractility) ii. Heart must receive adequate blood to pump (a) As volume of blood increases, precontraction pressure (preload) builds up. (b) Preload: Stretching of the cardiac muscles prior to contraction (1) As preload increases, the heart muscles stretch. (2) When muscles are stretched, myocardial contractility increases and cardiac output increases. iii. The resistance to flow (afterload) must be appropriate. 5. Blood pressure is generated by the contractions of the heart and dilation and constrictions of blood vessels. a. Carefully controlled by the body to ensure adequate circulation in various tissues and organs b. Considered a rough measure of perfusion c. Varies directly with cardiac output, systemic vascular resistance, and blood volume d. Systemic vascular resistance (SVR): Resistance to blood flow within all of the blood vessels except the pulmonary vessels e. Systolic pressure: Pressure generated every time the heart contracts f. Diastolic pressure: Pressure maintained within the arteries while the heart rests between heartbeats 6. Perfusion depends on cardiac output, SVR, and transport of oxygen. a. Cardiac output = heart rate x stroke volume b. Blood pressure = cardiac output x systemic vascular resistance 7. Mean arterial pressure (MAP) is the patient’s blood pressure. a. Takes into consideration the systolic blood pressure (SBP) and diastolic blood pressure (SBP) b. Blood pressure required to sustain organ perfusion c. Roughly 60 mm Hg in the average person i. If MAP falls below normal for an appreciable amount of time, result will be ischemia of the organs from lack of perfusion. d. MAP = DBP + 1/3 (SBP – DBP) 8. Pulse pressure: Difference between systolic and diastolic pressures 9. The body is perfused via the cardiovascular system. a. Controlled by the autonomic nervous system, which is composed of competing systems i. The sympathetic nervous system prepares the body for physical activity during a stressful situation (a) Increases pulse rate, blood pressure, respiratory rate (1) Dilates blood vessels in areas needed for physical activity (2) Constricts blood vessels in areas involved with reproduction and restoration (b) Nerve signals travel between the brain and the body via nerves traveling through the spinal cord. (1) Nerves leave spinal cord and spread out to affect tissues in those areas. (c) Epinephrine and norepinephrine are released from the adrenal glands into the bloodstream to activate a sympathetic response in those areas. ii. The parasympathetic nervous system is responsible for rest and regeneration. (a) Opposes every action of the sympathetic nervous system (b) Decreases pulse rate, blood pressure, respiratory rate (c) Constricts blood vessels in muscular tissue (d) Dilates blood vessels in the digestive system B. Respiration and oxygenation 1. When you breathe, alveoli (thin-walled air sacs) receive oxygen-rich air. a. Oxygen dissolves in the blood stream and attaches to the blood’s hemoglobin. b. Oxygen molecules from the oxygenated blood pass through alveolar wall into pulmonary capillaries. c. If blood is not properly circulated, some cells and organs will not receive proper nutrients. 2. Oxygen and carbon dioxide pass across thin tissue layers through diffusion. a. Diffusion is a passive process. b. Molecules move from an area of higher concentration of molecules to an area with a lower concentration i. There are more oxygen molecules in alveoli than in the blood. (a) Oxygen moves from the alveoli into the blood. ii. There are more carbon dioxide molecules in the blood than in the inhaled air. (a) Carbon dioxide moves from the blood into alveoli. 3. Carbon dioxide is dissolved in plasma and attaches to the blood’s hemoglobin. a. Carbon dioxide combines with water to create carbonic acid. i. Carbonic acid concentrations are high just as the blood is moving toward the lungs. ii. At the lungs, carbonic acid breaks down and carbon dioxide is exhaled. C. Regulation of blood flow 1. Blood flow through the capillary beds is regulated by the capillary sphincters. a. Sphincters constrict and dilate to increase or decrease blood flow. i. Under control of the autonomic nervous system (a) Regulates involuntary functions like sweating and digestion (b) Respond to other stimuli like heat, cold, need for oxygen, and waste removal ii. Not all cells have the same needs at the same time. 2. Regulation of blood flow is determined by cellular need. a. Accomplished by vessel constriction or dilation with sphincter constriction or dilation b. Perfusion is accomplished by heart, blood vessels, and blood working together. VI. Pathophysiology of Shock A. Shock can result from inadequate cardiac output, decreased SVR, or the inability of red blood cells (RBCs) to deliver oxygen to tissues. 1. Disturbances will create the buildup of dangerous waste products that could lead to death of the organ a. Inadequate perfusion will cause damage to the cells as well as the body b. If shock persists, death will ultimately occur. c. The body compensates by shunting blood flow from organs that are more tolerant of low flow (skin and intestines) to vital organs that cannot tolerate hypoperfusion (heart, brain, lungs). 2. The cardiovascular system consists of the heart, blood vessels/arteries, and the fluid/blood. a. Known as the “perfusion triangle” b Shock means one part is not working properly. 3. Blood carries oxygen and nutrients through vessels to the capillary beds to tissue cells. a. Supplies are exchanged for waste products created during metabolism. b. Blood contains: i. RBCs: Responsible for transporting oxygen to cells and carbon dioxide away from cells ii. White blood cells: Help the body fight infection iii. Platelets: Responsible for forming clots iv. Plasma 4. Blood clots control blood loss. a. Form depending on one of the following: i. Retention of blood because of blockage in circulation (blood stasis) ii. Changes in a vessel wall iii. Blood’s ability to clot b. Injury causes platelets to aggregate at the injury site. i. RBCs become sticky and clump together. ii. Fibrinogen reinforces RBCs. iii. Clots are prone to rupture because blood is always moving due to blood pressure. 5. When the body senses that pressure in the system is failing, neural and hormonal mechanisms are triggered. a. Sympathetic nervous system will assume control of the body’s functions during shock b. Parasympathetic system controls involuntary functions by sending signals to the cardiac, smooth, and glandular muscles c. Epinephrine and norepinephrine causes changes in pulse rate, strength of cardiac contractions, and vasoconstriction in nonessential areas. i. Actions maintain pressure in the system, sustaining perfusion of the vital organs. 6. Body fluids shift to maintain pressure. a. Response occurs within seconds, causing signs and symptoms of shock. B. Compensation for decreased perfusion 1. The body responds to any event that leads to decreased profusion in order to preserve vital organs a. Baroreceptors located in the aortic arch and carotid sinuses sense decreased blood flow. i. Activate vasomotor center in medulla oblongata to begin constriction of the vessels. (a) Increases blood pressure b. Chemoreceptors measure shifts in carbon dioxide in the arterial blood. i. Regulates respiratory rate ii. Controls acid/base balance in the body 2. Stimulation normally occurs when the systolic pressure is between 60-80 mm Hg in adults, or lower in children. a. Vasomotor center increases the arterial pressure by constricting blood vessels b. Drop in pressure causes the artery walls to not stretch as much. i. Baroreceptor stimulation is decreased. c. Normally baroreceptor stimulation prevents vasoconstrictor center from constricting vessels. i. Leads to vasodilatation in the peripheral circulatory system ii. Decreases pulse rate and contractility iii. Causes a concomitant decrease in arterial pressure iv. With dropping pressure, baroreceptors are not stimulated for vasodilation. (a) Vessels constrict to raise blood pressure. d. Sympathetic nervous system is stimulated as the body recognizes a potential catastrophic event. i. Adrenal glands release epinephrine and norepinephrine into the bloodstream. (a) Causes tachycardia and increases contractility of the heart (b) Causes venous and arteriolar constriction, decreasing blood flow to skin, muscles, GI tract, kidneys (1) Blood is redistributed to the brain and the heart. e. Capillary hydrostatic pressure decreases in compensated phase of shock. i. Allows fluid from interstitial compartment to flow into vessels. 3. The renin-angiotensin-aldosterone system in the kidneys is activated, and antidiuretic hormone is released from pituitary gland. a. Triggers salt and water retention and peripheral vasoconstriction i. Increases blood pressure and cardiac output b. Fluid shifts from interstitial tissues into the vascular compartment. c. The spleen releases RBCs to augment blood’s oxygen-carrying capacity. 4. The overall response of the initial compensatory mechanisms is to increase preload, stroke volume, and pulse rate. a. Allows the body to compensate for a volume loss of up to 25% 5. Myocardial oxygen demand increases if hypoperfusion persists. a. Eventually the compensatory mechanisms cannot keep up with the demand. i. Cardiac output and ejection fraction decreases. ii. Tissue perfusion decreases, leading to impaired cell metabolism. iii. Systolic blood pressure decreases. iv. Fluid leaks from blood vessels. (a) Causes systemic and pulmonary edema b. Perfusion to the brain and coronary arteries decreases. i. Cells switch from aerobic metabolism (cellular processes occurring with adequate oxygen supply) to anaerobic metabolism (cellular processes occurring in the absence of oxygen). (a) Shifts oxygen-hemoglobin dissociation curve to the right to increase tissue oxygen delivery (1) Decreases cardiac function, making the heart susceptible to circulating catecholamines c. Other signs of hypoperfusion include: i. Dusky skin color ii. Oliguria iii. Impaired mentation 6. The release of epinephrine improves cardiac output by increasing the pulse rate and strength. a. Alpha-1 response includes: i. Vasoconstriction ii. Increased peripheral vascular resistance iii. Increased afterload b. Alpha-2 effects ensure regulated release of alpha-1. c. Beta responses affect the heart and lungs. i. Bronchodilation increases pulse rate, contractility, and conductivity. 7. Norepinephrine effects are mostly alpha-1 and -2 in nature. a. Centers on vasoconstriction and increasing peripheral vascular resistance i. Allows body to shunt blood from areas of lesser need to areas of greater need ii. To maintain circulation to the brain, the body will shunt blood away from the following tissues in this order: (a) Placenta (b) Skin (c) Muscles (d) Gut (e) Kidneys (f) Liver (g) Heart (h) Lungs b. Skin and muscles can survive with minimal blood flow for a longer period than major organs. c. If blood supply is inadequate to major organs for more than 60 minutes, they will develop complications. i. Referred to as the “Golden Period” 8. Failure of compensatory mechanisms to preserve perfusion leads to decreases in preload and cardiac output. a. Myocardial blood supply and oxygenation decrease, reducing myocardial perfusion. b. Coronary artery perfusion decreases. i. Leads to myocardial ischemia c. Normal functions of liver and pancreas are impacted. i. Inhibits insulin release d. Gastrointestinal motility is decreased. i. Causes stress ulcers to develop e. Diminished kidney perfusion decreases urine production. i. Leads to kidney failure if not reperfused within 45 minutes to 1 hour ii. Normal urine output is 30-40 mL/h iii. An output less than 500 mL per day is considered oliguria and can lead to acute kidney insufficiency. C. Shock-related events at the capillary and microcirculatory levels 1. Decreased perfusion leads to cellular ischemia. a. Minimal blood flow passes through the capillaries. i. Causes cells to switch from aerobic metabolism to anaerobic metabolism b. Decreased circulation leads to blood stagnation in the capillaries. i. The precapillary sphincter relaxes. ii. Postcapillary sphincters remain constricted. (a) Causes capillaries to become engorged with fluid iii. Capillary sphincters regulate blood flow through capillary beds. (a) Under control of autonomic nervous system (b) Blood flow is determined by cellular needs. (c) Blood flow is accomplished by vessel constriction or dilation. 2. The body can tolerate anaerobic metabolism for only a short time. a. Leads to systemic acidosis and depletion of the body’s energy reserves b. Incomplete glucose breakdown leads to an accumulation of pyruvic acid. i. Transformed to lactate and other acid by-products ii. Acidosis develops iii. Hydrogen ions and lactic acid accumulate in the body. 3. Ischemia stimulates increased carbon dioxide by the tissues. a. Excess carbon dioxide combines with intracellular water to produce carbonic acid. i. Reacts with other buffers to form more intracellular acidic substances b. Acidosis serves as an indirect measure of tissue perfusion. c. Acidic blood inhibits hemoglobin in the RBCs from binding with and carrying oxygen. i. Adds to cellular oxygen debt 4. Sodium is inclined to diffuse into the cells. a. Sodium-potassium pump normally sends sodium back out against the concentration gradient. i. Involves active transport and an ample supply of ATP ii. Reduced ATP results in dysfunctional sodium-potassium pump. (a) Excessive sodium diffuses into the cells, depleting the interstitial compartment. 5. Intracellular enzymes that usually help digest and neutralize bacteria are bound in an impermeable membrane. a. Cellular flooding explodes the membrane and releases the enzymes. i. Auto-digest the cell ii. Leads to last phase of shock (irreversible or terminal shock) 6. Accumulating acids and waste products act as potent vasodilators. a. Decreases venous return and diminishes blood flow to vital organs and tissues b. When aortic pressure falls below MAP of 60 mm Hg: i. Coronary arteries no longer fill. ii. The heart is weakened. iii. Cardiac output falls. c. Myocardial depressant factor is released from ischemic pancreas. i. Further decreases the pumping action of the heart 7. Reduced blood supply results in slowing and stopping of sympathetic nervous system activity. a. Metabolic wastes are released into slow-flowing blood. b. Leads to platelet agglutination and formation of microthrombi c. Stretched capillary walls lose their ability to retain large molecules. i. Leak into surrounding interstitial spaces ii. Oxygen transport decreases. (a) Increases cellular hypoxia 8. The buildup of lactic acid and carbon dioxide acts as a potent vasodilator. a. Leads to the relaxation of the postcapillary sphincters b. Accumulation washes into the venous circulation. i. Increases metabolic acidosis ii. Referred to as the capillary washout phase c. Ischemia and necrosis lead to multiple-organ dysfunction syndrome. 9. White blood cells and blood clotting systems are impaired. a. Decreased resistance to infection and disseminated intravascular coagulation (DIC) may occur. b. DIC: Proteins that control clotting become active under abnormal circumstances. i. 97% of patients who die from hemorrhagic shock have evidence of coagulation defects ii. Frequent abnormalities are: (a) Elevated prothrombin (97%) (b) Depressed platelet counts (72%) (c) Elevated partial thromboplastin time (70%) iii. Complicates septic shock D. Multiple-organ dysfunction syndrome 1. Multiple-organ dysfunction syndrome (MODS): Progressive condition characterized by failure of two or more organs or organ systems that were initially unharmed by the acute disorder or injury. a. Six organ systems are surveyed during diagnosis: i. Respiratory ii. Hepatic iii. Renal iv. Hematologic v. Neurologic vi. Cardiovascular systems b. Each system is assigned a score to determine risk. i. Example: Glasgow Coma Scale for neurologic system 2. Each type of tissue has its own time that it can be deprived of oxygenated blood before it will die (warm ischemic time). a. Effects of poor perfusion depends on how much time transpires prior to adequate reperfusion. i. Brain and central nervous system tissue: 4-10 minutes ii. Skin and muscles: 2 hours b. When poor perfusion is not restored in the first hour, blood is diverted in the order of: i. Skin and muscles ii. Gut iii. Liver iv. Kidneys c. A single injury can have devastating impacts on multiple organs and organ systems. 3. Patients have a mortality rate of 60-90%. a. Leading cause of death following septic, traumatic, and burn injuries b. Classified as primary or secondary i. Primary: Direct result of an insult ii. Secondary: Encompasses the organ dysfunction that occurs as an integral component to the patient’s response 4. Occurs when injury or infection triggers a massive systemic immune, inflammatory, and coagulation response. a. Results in the release of inflammatory mediators and activation of the following systems: i. Complement system (a) Overactive system activates phagocytes (b) Introduces further inflammation and damage to cells ii. Coagulation system (a) Endothelial damage and coagulation becomes uncontrolled. (b) Results in microvascular thrombus formation and tissue ischemia. iii. Kallikren-kinnin system (a) Release of bradykinin leads to tissue hypoperfusion. b. Overactivity results in a maldistribution of systemic and organ blood flow. c. Body attempts to compensate by accelerating tissue metabolism, which leads to: i. Tissue hypoxia ii. Tissue hypoperfusion iii. Exhaustion of the cells fuel supply (ATP) iv. Metabolic failure v. Lysosome breakdown vi. Anaerobic metabolism vii. Acidosis viii. Impaired cellular function d. Progression causes various organs to malfunction. 5. Typically develops within hours or days after resuscitation. a. Signs and symptoms: i. Hypotension ii. Insufficient tissue perfusion iii. Uncontrollable bleeding iv. Multisystem organ failure v. Possible low-grade fever may from inflammatory response, tachycardia, dyspnea vi. Possible difficulty oxygenating patients due to lung injury and respiratory distress 6. From 14-21 days, renal and liver failure can develop. a. The GI and immune systems may collapse. b. Patient may undergo cardiovascular collapse. c. Death is typical within days to weeks of the insult. 7. Affects specific organs and organ systems: a. Heart i. May result in dysrhythmias, muscle ischemia, infarction, pump failure ii. Peripheral pulses are weak or absent. iii. Extremities are cyanotic and cold. b. Lungs i. Failure is seen by respiratory distress syndrome or noncardiogenic pulmonary edema. ii. Pulmonary arterial pressures increase, producing pulmonary hypertension. iii. Pulmonary capillary blood flow reduction results in: (a) Impaired gas exchange (b) Reduced Pao2 level (c) Increased Paco2 level iv. Alveolar cells are ischemic. v. Interstitial and intra-alveolar edema at low wedge pressures occur. vi. Results are: (a) Respiratory failure (b) Hypoxemia (c) Respiratory acidosis c. Central nervous system i. Decrease in cerebral perfusion pressure and blood flow result in: (a) Confusion (b) Reduced responses to verbal and painful stimuli (c) Unresponsiveness d. Kidneys i. Reduced renal blood flow results in acute tubular necrosis, which leads to: (a) Oliguria (urine output of greater than 20 mL/h) (b) Retention of toxic waste in the blood (c) Worsened metabolic acidosis e. Liver i. Coagulopathies are produced (clotting and bleeding occur at the same time). ii. Failure to filter bacteria leads to vulnerability to infection. iii. Inability to metabolize waste products leads to increased level of toxins in the blood. iv. Cell death increases enzyme levels in the blood. v. Results in: (a) Ischemic or hypoxic hepatitis (b) Shock liver f. GI tract i. Ischemic gut syndrome occurs. ii. Gut leaks and contributes to progression of shock. VII Causes of Shock A. Normal tissue perfusion requires an intact heart, fluid volume, and tubing capable of reflex adjustments to pump output and fluid volume. 1. Damage to any of these mechanisms disrupts tissue perfusion, causing shock to ensue. 2. Shock results from many conditions. a. Damage occurs because of insufficient perfusion of organs and tissues. i. Tissues start to die, affecting all local body processes. b. If shock is not promptly arrested or reversed, the patient will die. 3. Have a high index of suspicion for shock in emergency medical situations. a. Expect shock to accompany: i. Massive external or internal bleeding ii. Multiple severe fractures iii. Abdominal or chest injury iv. Spinal injury v. Severe infection vi. Major heart attack vii. Anaphylaxis 4. There are three basic causes of shock. a. Pump failure b. Low fluid volume c. Poor vessel function 5. Certain categories of patients are more at risk to shock. a. Patients with trauma or bleeding b. Patients with massive MI c. Pregnant women d. Patients with septic shock e. Elderly patients (especially men) i. These patients often have decreased cardiac output and cardiac reserves, as well as atherosclerosis affecting vasoconstriction. VIII The Progression of Shock A. Shock occurs in three phases: Compensated, decompensated, and irreversible. 1. These phases are also called the four grades of hemorrhage or four classes of shock. a. Class I and II = compensated shock b. Class III = decompensated shock c. Class IV = irreversible shock, or terminal shock 2. You need to be able to recognize the signs and symptoms early on and begin immediate treatment before damage occurs. a. Be aware of subtle body signs exhibited while the body is compensating b. Anticipate potential for shock from scene size-up and evaluation of MOI. c. Do not rely on any one sign or symptom to determine the phase of shock. d. Provide rapid assessment and immediate transportation. e. An altered mental status change is a late indicator of shock. B. Compensated shock 1. This is the earliest stage of shock where the body can still compensate for blood loss. 2. Level of responsiveness is the best indication of tissue perfusion. a. Release of chemical mediators causes arterial blood pressure to remain normal or elevated. b. Rate and depth of respirations increase. c. Blood pressure is maintained. i. Blood loss in hemorrhagic shock is about 15-30% at this point. ii. Pulse pressure narrows. iii. Patients have a positive orthostatic tilt test result. C. Decompensated shock 1. Result of blood volume drop of more than 30% 2. Compensatory mechanisms begin to fail. a. Signs and symptoms become obvious. b. Cardiac output falls dramatically. i. Reduces blood pressure and cardiac function c. Blood shunts to the brain, heart, and kidneys. d. Cells within nonperfused tissue become hypoxic, leading to anaerobic metabolism. 3. Sometimes treatment will result in recovery. 4. Once blood pressure drop is detected, shock is well developed. a. Especially true in children and infants i. Blood pressure may be maintained until a loss of 35-45% of blood volume. b. Consider an emergency, and start transport in less than 10 minutes. i. Provide fluid resuscitation en route. D. Irreversible (terminal) shock 1. Last phase of shock when the condition has progressed to a terminal stage a. Arterial blood pressure is abnormally low. b. Rapid, irreversible deterioration of cardiovascular system occurs. c. Life-threatening reductions in cardiac output, blood pressure, and tissue perfusion. d. Blood is shunted away from liver, kidneys, and lungs. e. Cells begin to die. f. Vital organ damage cannot be repaired. 2. Aggressive treatment does not usually result in recovery. a. You should still provide aggressive treatment en route to the trauma center. IX Patient Assessment of Shock A. Scene size-up 1. Size up the scene for hazards. 2. Follow standard precautions. 3. Determine the number of patients and the need for additional or specialized resources. 4. Quickly assess the MOI or nature of illness (NOI). a. Can give you clues about: i. Causes of nonhemorrhagic shock ii. Extent of bleeding B. Primary assessment 1. Form a general impression. a. How does the patient look? i. Some do not pass the look test and will need to be fast tracked based on MOI/NOI. ii. A blue or sweaty pale look will need immediate attention. b. Patients who do not greet you may be concentrating on breathing, injuries, or in severe pain. c. Assess the patients mental status using AVPU. d. Introduce yourself and ask their name, location, and the day of the week. 2. Airway and breathing a. If you suspect cardiac arrest, use the CAB approach. i. CAB = circulation/compressions, airway, breathing b. Otherwise, asses the ABCs. i. ABCs = airway, breathing, circulation c. Patients with life-threatening airway problems cannot speak or speak in one- or two-word sentences. d. Manage immediate threats to the patient’s airway or breathing. i. Position the patient’s airway. ii. Clear the airway of secretions, blood, or vomitus. iii. Administer oxygen. e. If difficulty breathing is suspected, examine the chest for: i. Flail segments ii. Impaled objects iii. Holes that need to be sealed with an occlusive dressing f. Assess the adequacy of the patient’s ventilation in respect to volume and rate. i. Decide if it will be necessary to assist the patient with bag-mask ventilation and high-concentration oxygen. 3. Circulation a. Take CAB approach and perform chest compressions if you suspect the patient does not have a pulse. b. In patients with a pulse, determine if it is adequate to sustain life. i. Perform a rapid exam to check for external blood loss that can be controlled. c. In conscious patients, assess the pulse at the radius. i. In unconscious patients, check the carotid pulse in the neck. ii. Is the radial pulse weak and thready, or irregular? (a) If the radial pulse is barely palpable, it is an indicator that systolic blood pressure is dropping fast. d. If you know the patient is hypotensive, provide immediate transport to the ED. e. The rapid exam is meant to detect injuries that are life threatening and need immediate attention. f. Also note the patient’s skin color, temperature, and condition. 4. Transport decision a. All patients need to be prioritized. i. If patient has shock from a medical problem, fast track to an assessment based on body systems involved. ii. If patient has shock from trauma, let the MOI guide your assessment of the major body cavities and regions. C. History taking 1. History taking, secondary assessment, and reassessment can be done en route to the ED in a high-priority patient. a. Keep on-scene care to essential items that must be done before moving the patient. b. Unless patient is pinned, and you suspect a delay in extrication, delay establishing IV/IO access until you are en route. D. Secondary assessment 1. Shock is considered hypovolemic or hemorrhagic until proven otherwise. a. Phases of shock relate to percentage of blood loss. i. Compensated ii. Decompensated iii. Terminal/irreversible b. Drop in systolic blood pressure or altered mental status indicates the body can no longer compensate. 2. Other indicators include end-tidal carbon dioxide and lactic acid buildup. a. Lactate is a sign of metabolic distress and an early indicator of severe sepsis. b. Portable lactate monitors are similar to glucometers. i. Incorporated into sepsis alert programs in some major cities E. Reassessment 1. Revisit the primary assessment, vital signs, chief complaint, and any treatment performed on the patient. a. Determine the effectiveness of treatment on the patient. b. Prepares you to present the patient at the hospital with complete, concise account 2. Determine what interventions are needed for your patient. a. Focus on supporting the cardiovascular system. b. Treat for shock early and aggressively. i. Provide oxygen. ii. Put patient in position dictated by local protocol. iii. Provide warmth, gain IV access, and administer fluid as needed. 3. Patients in decompensated shock will need rapid intervention. a. Most shock interventions do not require a physician’s order, but some do. b. Determine if the patient is in compensated or decompensated shock. i. Document your findings. F. Special considerations for assessing shock 1. Healthy, fit, young adults are equipped to combat life-threatening blood loss. a. Aerobic exercise results in a resilient cardiovascular system. b. A healthy weight along with a diet of low salt, low fat, and low cholesterol prepare the body to handle effects of epinephrine and norepinephrine released during shock. c. Blood vessels can handle vasoconstriction without developing clots. d. Arteries are generally free of plaque. e. Not smoking increases oxygenation. G. Pediatric considerations 1. Pediatric patients can compensate until a 30-35% blood loss. a. Compensation ability relies on increasing their pulse rate and systemic vascular resistance. i. Causes body to burn glucose rapidly (a) Pediatric patients have little glucose in storage. b. Compensate through vasoconstriction 2. Treat aggressively and early with significant MOI or indication of shock. a. Never wait to see a drop in systolic blood pressure. b. Provide oxygen. c. Manage body temperature. d. Place patient in appropriate position. e. Initiate IV access en route. H. Geriatric considerations 1. Their ability to manage a loss of blood volume is diminished. a. Vasoconstriction is less effective. b. Renal and vascular systems cannot handle infusion of large volumes of fluid. c. Thermoregulation is less effective. 2. Manage fluid therapy carefully. a. Administer fluid boluses and reassess patient, including lungs. b. Anemic patients have a disadvantage. 3. Cardiovascular disorders or diabetes affect ability to compensate. 4. Blood thinning medications may prevent clot formations. a. Even minor nose bleeds may present a serious issue. X Emergency Medical Care of a Patient with Suspected Shock A. Airway and ventilatory support take top priority when treating shock. 1. Maintain an open airway and suction as needed. 2. Administer high-flow supplemental oxygen with a non-rebreathing mask or assist ventilation with a bag-mask device. 3. Control external hemorrhage. a. Estimate the amount of blood lost. 4. Look for signs of internal hemorrhage. a. Consider potential for loss in area of hemorrhage. b. Consider MOI, maintain high suspicion 5. IV therapy can be helpful in supplementing initial therapies. a. Perform en route to ED b. Establish IV access with two large-bore catheters (14 or 16 gauge). c. Administer IV volume expanders to replace lost blood. i. Isotonic crystalloids should be used d. Maintain perfusion without increasing internal or uncontrollable external hemorrhage. i. Most protocols advise IV fluid in boluses of 20 mL/kg until radial pulses return. ii. Radial pulses equate to a systolic blood pressure of 80-90 mm Hg. (a) Sufficient to perfuse the brain and other vital organs e. Some studies suggest maintaining systolic blood pressure at 80 mm Hg. i. Thought to be safer for the patient ii. Restoration of normotension may aggravate ongoing bleeding. 6. If signs of tension pneumothorax, perform the needle chest decompression. a. Improves cardiac output b. Allows mediastinum to shift back into normal location 7. With suspected cardiac tamponade, recognize the need for expeditious transport for pericardiocentesis at the ED. a. Follow your local ALS protocols. 8. Nonpharmacologic interventions include proper positioning of the patient, prevention of hypothermia, and rapid transport. a. Apply the cardiac monitor. b. Consider need for regional trauma center. c. Air medical transport may be the best option. d. Provide psychological support en route. 9. To properly treat suspected shock, refer to Skill Drill 40-1. B. IV therapy 1. IV lines are inserted for one of three purposes: a. Provide a route for immediate replacement of fluids. b. Provide a route for potential replacement c. Provide a route for the administration of medication. i. IV fluid of choice is normal saline or lactated Ringer’s. 2. All patients in hypovolemic shock need IV fluid replacement. a. IV access should also be obtained in patients who are likely to develop hypovolemic shock due to one or more of these conditions: i. Profuse external bleeding ii. Internal bleeding iii Ulcer iv. Vaginal bleeding v. Blunt trauma to abdomen vi. Fracture of pelvis or femur vii. Severe or widespread burns viii. Heat exhaustion ix. Intractable vomiting or diarrhea x. Neurogenic shock xi. Septic shock 3. IV lines should be inserted to keep a vein open in case of need for emergency administration of drugs. a. Patients with poor cardiac output have blood shunted away from the skin and skeletal muscles. i. Drugs administered subcutaneously or intramuscularly are absorbed at a low and unpredictable rate. b. Traditional use of D5W has been discontinued and replaced with normal saline. c. Patients who need a vein kept open include: i. Those at risk of cardiac arrest ii. Those needing parenteral medication 4. IV flow rate is determined by local protocol. a. Reflects the patient’s presumptive diagnosis and condition of his or her lungs (wet or dry) 5. Volume expanders and plasma substitutes a. Hypovolemic shock should be treated with volume expanders to replace what was lost. i. Cardiac inotropic drugs may be administered to increase strength of concentrations. ii. Rate-altering medications may be administered to enhance perfusion. b. Also indicated for obstructive shock and spinal shock c. A variety of solutions have properties similar to those of plasma. i. Used to maintain circulatory volume ii. Cannot replace RBCs, platelets, or plasma proteins iii. More readily available than whole blood or plasma (a) Do not require typing (b) Can be carried in the ambulance iv. Do not carry the risk of hepatitis or AIDS d. Plasma substitutes and volume expanders include: i. Dextran (a) High-molecular-weight glucose polymer (b) Stays in the vascular space due to its large size (c) Tends to coat RBCs and may cause clotting problems in large quantities (d) Can interfere with cross-matching of blood (1) Blood type and cross-matching should be drawn prior to administration. (e) Interferes with platelet function and may increase bleeding ii. Plasma protein fraction (Plasmanate) (a) Contains albumin and serum globulin (b) Expensive (c) Reported to produce hypotensive reactions in some patients iii. Polygeline, hetastarch, and other starch solutions (a) Resemble osmotic and electrolyte composition of the plasma (b) Do not interfere with clotting or blood typing. 6. Crystalloids a. Solutions that do not contain proteins or other large molecules (noncolloids) b. Rapidly equilibrates across the capillary walls into tissues i. You must administer two to three times volume of blood lost. c. Fluids of choice when only salt and water have been lost d. Current debate about their role vs. colloids in the treatment of shock i. Practical considerations favor using these in the field for initial fluid resuscitation. e. Commonly used crystalloids are: i. Normal saline (a) Sodium chloride in water at a concentration isotonic with extracellular fluid ii. Lactated Ringer’s solution (a) Includes small amounts of potassium and calcium (b) Contains 28 mEq of lactate, added as a buffer (c) Preferred by trauma surgeons because of the belief that it decreases acidosis in patients with severe hemorrhagic hypovolemia f. Crystalloids do not carry oxygen, change the viscosity of the blood by thinning it, and dissolve clotting factors. i. Most ALS protocols limit the number of liters administered to the patient. XI Pathophysiology, Assessment, and Management of Specific Types of Shock A. The three primary classifications of shock coincide with the conditions that cause them: Cardiogenic, distributive, and hypovolemic. 1. Cardiogenic shock results from a weakening pumping action of the heart. 2. Distributive shock is broken down into chemical and neural causes. a. Septic shock is caused by fluid shifts associated with massive infections and poisons resulting in vasodilation. b. Neurogenic shock is caused by blood vessel dilation caused by a brain or spinal/nerve injury. 3. Other conditions decrease tissue perfusion, including: a. Conditions that obstruct the flow of oxygen into the bloodstream and starving tissue i. Leads to obstructive shock ii. May include: (a) Tension pneumothorax (b) Cardiac tamponade (c) Pulmonary embolism (d) Airway obstruction (e) Carbon monoxide poisoning 4. Nonhemorrhagic causes of hypovolemic shock are grouped by how they reduce perfusion. a. Weakening of the pump b. Increase in the size of the container c. Direct mechanical interference with the circulation 5. Initial management is the same for each type of shock. a. Manage the airway. b. Administer supplemental oxygen. c. Put the patient in a position of comfort. d. Obtain vital signs. e. Obtain IV access. f. Maintain body heat. B. Cardiogenic shock 1. Occurs when the heart cannot circulate sufficient blood to maintain adequate peripheral oxygen delivery. a. Many diseases can cause destruction or inflammation of the heart. i. Too much muscle damage means the heart cannot function effectively. (a) Filling is impaired or outflow is obstructed. b. The shock is caused by direct pump failure. 2. Most commonly caused by an AMI accompanied by 40% dysfunction of the left ventricle. a. Other intrinsic causes of shock include: i. Right ventricular failure ii. Valvular disorders iii. Cardiomyopathies iv. Ventricular septal defects v. Papillary muscle rupture vi. Myocardial insufficiency vii. Sustained dysrhythmias b. Some experts consider ventricular fibrillation as the ultimate form of cardiogenic shock. c. Manifests with poor contractility, decreased cardiac output, impaired ventricular filling d. Extrinsic causes include: i. Pericardial tamponade ii. Effusion iii. Pulmonary emboli iv. Tension pneumothorax 3. Populations at the greatest risk include: a. The elderly b. Patients with a history of diabetes mellitus c. Those with a history of AMI with an ejection fraction of less than 35% i. Ejection fraction: Portion of blood ejected from the ventricle during systole ii. Normal ejection fraction is 55-70% . iii. Measured with an echocardiogram, MRI, CT of the heart, or during cardiac catheterization 4. Diagnosis may be difficult to make in the field. a. Once a diagnosis has been made, newer treatment modalities have greatly improved long-term prognosis. 5. Prolonged efforts to stabilize the condition of the patient in the field are not recommended. a. Expedite transport as quickly as possible. b. Place the patient in a position of comfort. c. Secure the airway. d. Monitor the Spo2 e. Administer supplemental oxygen via a non-rebreathing mask at 12-15 L/min. f. Consider CPAP/BiPAP. g. Apply electrodes, document rhythm, and obtain a 12-lead ECG. h. Administer crystalloid solution via IV. i. Auscultate the lungs i. If clear, try a fluid challenge of 200 mL. 6. Some EMS systems use dopamine at low doses in the beta range if the patient has a MAP of less than 60 mm Hg. a. Using a high-dose of dopamine may be temporarily ordered at the expense of other organs. i. Anticipate rapid tachycardia. 7. Combination drug therapy is often needed at the hospital while awaiting: a. Cardiac catheterization b. Hemodynamic monitoring catheters c. Insertion of an intra-aortic balloon pump C. Obstructive shock 1. Causes are not directly associated with loss of fluid, pump failure, or vessel dilation. a. Occurs when blood flow in the heart or great vessels becomes blocked b. Common causes in trauma are: i. Tension pneumothorax ii. Cardiac tamponade iii. Pulmonary embolus iv. Carbon monoxide poisoning 2. Tension pneumothorax a. Caused by damage to the lung tissue i. Allows air held within the lung to escape the chest cavity ii. If untreated, a sufficient amount of air will accumulate within the chest cavity and apply pressure to the structures of the mediastinum. iii. Shifting of trapped air moves chest organs toward the uninjured side. b. Life-threatening condition due to the kinking of the vena cava that occurs as the mediastinum shifts. c. Only action that can prevent death is the decompression of the injured side of the chest. i. Needle chest compression is a skill many providers are allowed to perform. 3. Cardiac tamponade a. Caused by blunt or penetrating trauma, tumors, or pericarditis b. Can progress quickly c. Occurs when blood leaks into the tough fibrous membrane (pericardium) i. Causes an accumulation of blood within the pericardial sac ii. Leads to compression of the heart iii. Continued pressure obstructs the flow of blood into the heart. (a) Results in decreased outflow from the heart (b) Electrical alternans and small QRS may appear on the ECG. d. The ultimate treatment for cardiac tamponade is pericardiocentesis. i. Inserting a needle attached to a syringe into the chest to penetrate the pericardium and withdraw fluid ii. Technique is risky and rarely performed by paramedics. iii. Early recognition and rapid transport is key in treatment. iv. Follow local ALS protocols. e. Signs include: i. Muffled heart sounds ii. Systolic and diastolic blood pressure merging D. Distributive shock 1. Occurs when there is widespread dilation of the resistance vessels (small arterioles), the capacitance vessels (small venules), or both a. Circulating blood volume pools in vascular beds. b. Tissue perfusion decreases. c. Most common types of distributive shock are: i. Septic ii. Neurogenic iii. Anaphylactic iv. Psychogenic 2. Septic shock a. Presence of sepsis syndrome and a systolic blood pressure less than 90 mm Hg or a decrease from the baseline blood pressure of more than 40 mm Hg b. Occurs from a widespread infection i. Usually caused by gram-negative bacterial organisms ii. May also be caused by: (a) Gram-positive bacteria (b) Fungi (c) Viruses (d) Rickettsia c. Infection activates inflammatory-immune response, resulting in: i. Increased microvascular permeability ii. Vasodilation iii. Third-space fluid shifts iv. Microthrombi formation d. An uncontrolled and unregulated response results in hypoperfusion to the cells. i. Left untreated, this will result in: (a) Multiple-organ dysfunction (b) Death e. Septic shock is a complex problem. i. Insufficient volume of fluid in the container ii. Fluid leaks out and collects in the respiratory system. iii. Larger-than-normal vascular bed must contain the smaller-than-normal volume of intravascular fluid. f. Presents similarly to hemorrhagic shock. i. The difference is that patients usually have warm or hot skin from elevated core body temperature. g. Treatment requires complex hospital management. i. Transport as quickly as possible. (a) Use high-flow oxygen during transport. (b) Ventilatory support may be necessary. ii. Give normotensive patients dopamine to maintain blood pressure and renal perfusion. iii. Give norepinephrine to a patient who remains in “warm” shock. iv. Give epinephrine to a patient who remains in “cold” shock. v. Use blankets to conserve body heat. vi. Administer fluid boluses to maintain radial pulse. 3. Neurogenic shock a. Usually results from spinal cord injury i. May also derive from medical causes ii. Results in loss of normal sympathetic nervous system tone and vasodilation b. Muscles in the walls of the blood vessels are cut off from the nerve impulses that cause them to contract. i. All vessels below the level of the spinal injury dilate widely. (a) Increases size and capacity of the vascular system, causing blood to pool (b) Perfusion of organs and tissues becomes inadequate. ii. Patient experiences relative hypovolemia, leading to hypotension. iii. Relative bradycardia occurs. iv. Skin is pink, warm, and dry because of cutaneous vasodilatation. v. Epinephrine and norepinephrine are not released. (a) Patient will not sweat below the level of injury. c. Spinal shock: Local neurologic condition that occurs after a spinal injury produces motor and sensory losses i. Damage to the spinal cord may cause injury to the autonomic nervous system. (a) Swelling and edema of the cord begin within 30 minutes after an insult. ii. Secondary cord injury develops over the first few days. iii. Severe pain may be present about the level of injury. iv. Spinal shock is characterized by: (a) Flaccid paralysis (b) Flaccid sphincters (c) Absent reflexes v. Level of injury to the cord is related to the severity of neurogenic shock development. (a) Injury above the T-1 level can disrupt all the spinal tracts that control the entire sympathetic system. (b) Injuries from T-1 to L-3 may partially interrupt sympathetic outflow. (c) The higher the injury, the more likely spinal shock development. d. Care is similar to the general management approach for any patient with shock. i. The patient should also be immobilized. ii. Keep the patient warm. (a) Spinal injuries can disrupt thermoregulatory mechanisms. e. Determine the necessity for IV fluids based on hemodynamic status. i. Keep systolic blood pressure at 90 mm Hg or higher. ii. General hemodynamic resuscitation includes volume loading with normal saline. (a) Boluses of 20 mL/kg increments up to 2 L via large-bore IV catheter (b) Use warm fluid to prevent hypothermia. f. With pure neurogenic shock, vagal blockers and vasopressor agents may be used to better advantage than overhydrating the patient. i. Monitor the patient’s response. g. Consider steroid use per local protocols. 4. Anaphylactic shock a. Occurs when a person reacts violently to a substance to which he or she has been sensitized i. Sensitization: Developing a heightened reaction to a substance (a) Subsequent exposure after sensitization produces a more severe reaction. b. No loss of blood, no vascular damage, only slight possibility of direct cardiac muscular injury i. Patient experiences widespread vascular dilation instead. ii. While the container is larger, the blood volume is less. (a) Poor oxygenation and perfusion may prove fatal. c. Immune system chemicals are released when exposed to an allergen. i. Causes severe bronchoconstriction, as well as urticaria (hives) ii. Results in widespread vasodilatation (a) Causes distributive shock (b) Fluid leaks out of the blood vessels and into interstitial space, resulting in: (1) Hypovolemia (2) Significant swelling d. Angiodema: Recurrent large areas of subcutaneous edema of sudden onset i. Usually disappear within 24 hours ii. Mainly seen in young women iii. Frequently result of food or drug allergy e. Management needs to occur quickly. i. Remove the inciting cause if possible. ii. Resolve any immediate life threats to the ABCs. iii. Evaluate the patient’s ventilatory status and the need for bag-mask ventilation. iv. Provide cardiovascular support with IV fluid challenges of crystalloid solution. v. Administer epinephrine or vasopressor in high doses to reverse the target-organ effect. vi. Consider need for bronchodilator. vii. Impede further mediator release with antihistamine. 5. Psychogenic shock a. Sudden reaction of the nervous system that produces a temporary, generalized vascular dilation, resulting in syncope b. Blood pools in dilated vessels. i. Brain ceases to function normally. ii. Patient faints. c. Life-threatening causes include: i. Irregular heartbeat ii. Brain aneurysm d. Other causes include: i. Receipt of bad news ii. Fear or unpleasant signs e. Circulation to the brain is usually restored and its normal function continues. f. If the patient has fallen, check for injuries. g. Assess the patient thoroughly for any other abnormality. h. If the patient cannot walk without weakness, dizziness or pain, suspect another problem. i. Transport this patient promptly. i. Record your initial observations of vital signs and level of consciousness. j. Obtain an ECG. k. Learn from your bystanders: i. Whether the patient complained of anything before fainting ii. How long he or she was unresponsive E. Hypovolemic shock 1. Occurs because of inadequate blood volume a. Hemorrhagic and nonhemorrhagic causes i. Blood loss (internal or external hemorrhagic shock) ii. Plasma loss (burns) iii. Electrolyte solution loss (vomiting, diarrhea, sweating) 2. Nonhemorrhagic hypovolemic shock occurs when the fluid loss is contained within the body. 3. Abnormal losses of fluids and electrolytes can occur by: a. GI losses (through vomiting and diarrhea) b. Loss from fever, hyperventilation, high environmental temperatures c. Increased and excessive sweating d. Internal losses i. Peritonitis ii. Pancreatitis iii. Ileus e. Plasma losses from burns, drains, granulating wounds 4. Other causes of body fluid deficits include: a. Ascites b. Diabetes insipidus c. Acute renal failure d. Osmotic diuresis 5. Early signs of shock are restlessness and anxiety. a. Patient may report feeling thirsty. b. Patient may feel nauseated and vomit. c. Skin may become pale, cold and clammy, sometimes mottled. d. Patient may have a rapid, weak pulse. 6. Long-term therapy aims to restore the deficient body chemicals. a. For treatment in the field, all excessive fluid losses can lead to dehydration. 7. Symptoms of dehydration include: a. Loss of appetite b. Nausea c. Vomiting d. Fainting when standing up 8. Physical exam reveals: a. Poor skin turgor b. Shrunken, furrowed tongue c. Sunken eyes d. Weak and rapid pulse i. Rising more than 15 beats/min when patient is raised from recumbent to sitting position 9. Give a dehydrated patient an IV infusion of normal saline or lactated Ringer’s solution. a. Keep the patient flat or in the Trendelenburg position. i. Optimizes circulation to the brain 10. Establish and maintain an open airway. a. Keep suction at hand. b. Assist ventilation as needed. c. Keep the patient warm. 11. On your way to the ED, establish at least one large-bore peripheral IV lines using an over-the-needle catheter. a. If protocol requires, draw blood for ED personnel. 12. Administer saline or lactated Ringer’s solution. a. Run the first 500-mL as fast as it will flow, and then reassess the patient. b. Consider the use of warmed fluids. 13. Do not administer anything orally to the patient. 14. If patient vomits, administer an antiemetic. a. Keep patient at normal temperature. i. Patients in shock are unable to conserve body heat effectively. b. Place the patient with their head and legs elevated on pillows. 15. Monitor the patients’: a. ECG rhythm b. Mental status c. Pulse rate d. Blood pressure e. Spo2 f. ETco2 16. if you can feel a pulse over the femoral artery but not over the radial artery, the systolic blood pressure is between 70 and 80 mm Hg. a. Medical control may order: i. Sodium bicarbonate to treat acidosis ii. Vasopressor to enhance vasoconstriction b. Don’t wait for the blood pressure to fall before suspecting shock and starting treatment. i. Signals collapse of all compensatory mechanisms 17. The goal in treating shock is to save the brain, lungs, and kidneys. a. Best indication of brain perfusion is patient’s state of consciousness. b. Kidney perfusion can be gauged in urine output. i. Adequately perfused kidneys put out 30 mL to 50 mL per hour. c. In the field, you can estimate the patient’s peripheral perfusion by testing for capillary refill. i. Press on a patient’s fingernails until it blanches, then release. ii. If the skin under the nail doesn’t “pink up” within 2 seconds, peripheral perfusion is compromised. d. Rely on the patient’s state of consciousness to tell you how well the vital organs are being perfused. F. Respiratory insufficiency 1. The inability to breathe in adequate amounts of oxygen affects the ventilation process of respiration. 2. Insufficient amounts of oxygen in the blood can produce shock. a. Without oxygen, organs in the body cannot survive. 3. Some poisoning may affect the ability of cells to metabolize or carry oxygen. a. Carbon monoxide binds to the hemoglobin, rather than allowing oxygen to bind. i. Result is a hypoxic state b. Cyanide impairs the ability of cells to metabolize oxygen. i. Cellular asphyxia may occur. 4. An abnormally low amount of RBCs causes anemia. a. RBCs contain hemoglobin, which transports oxygen from the lungs to the tissues. b. May result from: i. Chronic or acute bleeding ii. Deficiency in vitamins or minerals iii. Underlying disease process c. Tissues may become hypoxic i. Pulse oximeter may still indicate adequate saturation. (a) Known as hypoxemic hypoxia 5. When treating a patient in shock from poor respiration, you must: a. Seal the hole in the chest. b. Stabilize impaled objects. c. Secure and maintain airway. d. Clear mouth and throat from obstructions. e. Assess Spo2, ETco2, and vital signs. f. Determine need for assisted ventilations. g. Determine most appropriate transportation destination. XII Transportation of Shock Patients A. When preparing to transport a shock patient, ask yourself when, where, and how. 1. Limit scene time to 10 minutes or less. 2. Know how to access aeromedical transportation. 3. Consider the priority of the patient and availability of a regional trauma center. a. Local transport protocols may deal with these issues. 4. Patients in shock may benefit from early surgical intervention. a. Transport to a facility with appropriate capabilities. i. If specific facility is not available, medical control will help make the transport decision. (a) May involve transport to a local facility and transfer to a tertiary care facility XIII Prevention Strategies A. Prevention of shock begins with your assessment of the MOI, findings, and patient’s clinical picture. 1. Be alert and search for early signs of shock. 2. Don’t rationalize irregularities. a. May become more obvious if patient is in shock i. By then it may be too late. XIV. Summary A. Develop expertise in quickly developing a differential field diagnosis of patients found in periarrest condition or period. B. Work with an experienced paramedic to develop skills in intuition, and become comfortable in making critical decisions when they are needed most. C. Hypoperfusion occurs when the level of tissue perfusion decreases below normal. Early decreased tissue perfusion may result in subtle changes long before a patient’s vital signs appear abnormal. Shock refers to a state of collapse and failure of the cardiovascular system that leads to inadequate circulation, creating inadequate tissue perfusion. D. The body is perfused via the cardiovascular system. Control of the cardiovascular system is a function of the autonomic nervous system, which is composed of competing subsystems. E. Tissue perfusion requires three intact mechanisms: a pump (heart), fluid volume (blood and body fluids), and tubing capable of reflex adjustments (constriction and dilation). If any one of those mechanisms is damaged, tissue perfusion may be disrupted, and shock will ensue. F. Shock occurs in three successive phases (compensated, decompensated, and irreversible). This is also referred to as the four grades of hemorrhage or four classes of shock, with class I and II being compensated shock, class III being decompensated shock, and class IV being irreversible shock, also referred to as terminal shock. G. Airway and ventilatory support are top priority when treating a patient with shock. H. If a patient is in shock, transport is inevitable. Ask when, where, and how. Consider the priority of the patient and the availability of a regional trauma center. Patients in shock will benefit from early surgical intervention. Transport to a facility equipped to handle this. I. Don’t wait for blood pressure to drop. Treat shock patients aggressively. J. Nonhemorrhagic causes of hypovolemic shock are grouped by how they reduce perfusion. These types of shock involve a weakening of the pump, increase of the size of the container, or direct mechanical interference with circulation. K. Prevention of shock and its effects begins with your assessment of the MOI, primary assessment findings, and the patient’s clinical picture. Be alert. Search for early signs. Post-Lecture This section contains various student-centered end-of-chapter activities designed as enhancements to the instructor’s presentation. As time permits, these activities may be presented in class. They are also designed to be used as homework activities. Assessment in Action This activity is designed to assist the student in gaining a further understanding of issues surrounding the provision of prehospital care. The activity incorporates both critical thinking and application of paramedic knowledge. Instructor Directions 1. Direct students to read the “Assessment in Action” scenario located in the Prep Kit at the end of Chapter 40. 2. Direct students to read and individually answer the quiz questions at the end of the scenario. Allow approximately 10 minutes for this part of the activity. Facilitate a class review and dialogue of the answers, allowing students to correct responses as may be needed. Use the quiz question answers noted below to assist in building this review. Allow approximately 10 minutes for this part of the activity. 3. You may wish to ask students to complete the activity on their own and turn in their answers on a separate piece of paper. Answers to Assessment in Action Questions 1. Answer: D. Hypovolemic shock Rationale: Non-hemorrhagic hypovolemic shock occurs when fluid loss is contained within the body. It may result from dehydration, burns, crush injuries, and anaphylaxis. Dehydration, or abnormal losses of fluids and electrolytes, may occur through a variety of mechanisms. There are also other causes of body fluid deficits. 2. Answer: B. 6 Rationale: Adult females have approximately 65 mL of blood per kg of body weight. Males have approximately 70 mL per kg. For an average adult weighing 80 kg, total blood volume would be approximately 6 L. Loss of greater than 1 L in the average adult will result in significant vital sign changes. Blood loss of half of this amount in a short period of time will result in hypovolemic shock. 3. Answer: A. Compensated Rationale: The earliest stage is compensated shock. In this phase the body can still compensate for blood loss. The patient’s level of consciousness is a good indicator of tissue perfusion. Her vital signs demonstrate that her body is compensating for existing fluid loss; however, her mental status is classified as “responsive to verbal stimuli” and her mottled skin color demonstrates that she has sustained some effect. 4. Answer: D. All of the above Rationale: As the body attempts to compensate for volume loss, the patient may respond with feelings of apprehension. The autonomic nervous system has been activated and body systems respond to this release of chemical mediators. Body fluid deficiency may trigger the thirst receptors. Blood flow is being diverted from peripheral tissues and the skin can become pale, cold, and clammy. 5. Answer: C. Increased external hemorrhage Rationale: Volume replacement in hypovolemic shock must be used with caution in the patient with uncontrolled external hemorrhage. Whereas the goal of maintaining perfusion is desired, attempts to increase the systolic blood pressure can result in prevention of clot formation and increased hemorrhage. Most protocols indicate fluid replacement of 20 mL/kg and titrated until radial pulses are present. Attempting to maintain the systolic blood pressure at 80 mm Hg may be safer and lessen the risk of continued bleeding. 6. Answer: D. Increase urine output Rationale: With the release of chemical mediators by the autonomic nervous system, the body begins to focus on survival of the essential organs including the heart and brain. Efforts to retain normal tissue perfusion results in peripheral vasoconstriction to increase preload and stroke volume while maintaining blood pressure. Catecholamine release may also trigger an elevation in the pulse rate and respiratory rate along with a deepening of respirations. This allows for increased oxygen availability and removal of carbon dioxide. Removal of carbon dioxide can help maintain the body’s acid-base balance. Increasing available oxygen allows for more to be consumed by the tissues under increased stress and need for adenosine triphosphate production. Urine formation decreases to preserve available fluid in the body. 7. Answer: B. Blood pressure Rationale: The body has multiple mechanisms to employ for compensation of blood loss and to maintain blood pressure. The brain is sensitive to perfusion changes and alterations in mental status may be initial indicators of shock. Catecholamine release shunts blood to the heart and brain through vasoconstriction of peripheral vessels so that changes in skin appearance may appear early. As part of the response to the catecholamine release, the pulse rate increases. Prior to the end of the compensated phase of shock, all vital signs have demonstrated some alteration from normal. As the body enters the decompensated phase the patient’s blood pressure may drop precipitously. Additional Questions 8. Rationale: As the paramedic begins to form a differential field diagnosis, underlying causes and contributing factors must be considered. The patient who presents with an obvious traumatic injury may have obtained the injury due to an underlying medical cause. Failure to identify and treat the medical issue can result in inadequate management or may impair treatment effectiveness. Current medications taken by the patient may alter the patient’s vital signs and inhibit response to emergency medications. For example, chronic use of some beta blockers for hypertension may make the patient’s pulse rate lower than normal and the patient may not respond appropriately to medications such as epinephrine. In the critical patient, existence of pre-morbid conditions may influence potential patient outcomes and affect treatment decisions. 9. Rationale: During decreased perfusion associated with shock, cellular metabolism begins to switch from aerobic to anaerobic in the hypoxic environment. Anaerobic metabolism generates increased levels of lactic acid and carbon dioxide. Sustained hypoxia decreases the amounts of adenosine triphosphate (ATP) produced by cells and ATP reserves are depleted. Ischemia occurs at the tissue level and carbon dioxide levels continue to increase. As levels rise, carbonic acid is formed and hypoxia worsens because it affects the affinity of oxygen to the hemoglobin in red blood cells. Reduction in ATP causes dysfunction of the sodium-potassium pump and cell membrane permeability is altered. Lysosomal enzymes are released as cell membranes rupture due to increased accumulation of cellular water. These enzymes will auto-digest the cells. Cardiac output falls and blood flow slows further, worsening perfusion. Ischemia progresses to necrosis of cells and tissues in the organs. Organs begin to fail and MODS can result. Assignments A. Review all materials from this lesson and be prepared for a lesson quiz to be administered (date to be determined by instructor). B. Read Chapter 41, Obstetrics, for the next class session. Unit Assessment Keyed for Instructors Unit Assessment Keyed for Instructors 1. What is the periarrest period? Answer: The periarrest period is the period either just before or just after cardiac arrest, when the patient is critical and care must be taken to prevent progression or regression into cardiac arrest. Examples of periarrest conditions include unstable dysrhythmias (bradycardia, tachycardia, ventricular tachycardia, and complete heart block), shock, syncope, myocardial ischemia, or heart failure. (p 1882) 2. What is a premorbid condition? Answer: Premorbid conditions are conditions that precede the onset of a disease. In the context of emergency medicine, the “disease” is life-threatening trauma or medical conditions that need to be rapidly identified and managed. Typically, premorbid conditions are sorted into those occurring in presumed to be healthy adults and those occurring in unhealthy adults. (p 1882) 3. What does the M-T SHIP acronym stand for? Answer: The M-T SHIP acronym stands for the following: M: Medication overdose/noncompliance (ie, barbiturates, narcotics, alcohol), metabolic causes (ie, B12 or thiamine deficiency) T: Tumor, trauma, toxins (ie, lead, mercury, carbon monoxide, toxidromes) S: Seizures (ie, status epilepticus, postictal state), stroke H: Hypoxia (ie, pulmonary, cardiac, anemia, or carbon dioxide retention), hyperthermia/hypothermia, hyperglycemia/hypoglycemia, hypertensive crisis, hypovolemia, hyperkalemia/hypokalemia (and other electrolyte imbalances) I: Infection and uremia (ie, renal or hepatic dysfunction) P: Psychiatric or behavioral disorders (p 1882) 4. How can you communicate what your intuition tells you to others on your team? Answer: The organizational scholar Karl Weick proposed a simple five-step process for communicating intuitive decisions and obtaining feedback from team members to ensure a clear understanding of all involved: 1. Here is what I think we are dealing with. 2. Here is what I think we should do. 3. Here is why. 4. Here is what we should keep our eyes on. 5. Now talk to me. Are there any other concerns? (p 1883) 5. What are the two types of bias in decision making? Answer: One of the most prevalent biases that you will face is confirmation bias. A confirmation bias is a tendency to gather and rely on information that confirms your existing views and avoids or downplays information that does not confirm your preexisting hypothesis or field differential. Another bias is anchoring bias. In this case, you may sometimes allow an initial reference point to distort your estimates. Your brain allows you to begin at that reference point and adjust from there, even if the initial reference point was arbitrary and may have been incorrect. This is often seen in financial negotiations and price setting. (pp 1883-1884) 6. What is shock? Answer: Shock is a state of collapse and failure of the cardiovascular system in which blood circulation slows and eventually ceases, leading to insufficient perfusion of organs and tissues. Shock is a normal compensatory mechanism used by the body to maintain systolic blood pressure and brain perfusion during times of distress. This response can accompany a broad spectrum of events, ranging from heart attacks, to falls, to allergic reactions, to motor vehicle crashes. If not treated promptly, shock will injure the body’s vital organs and ultimately lead to death. (p 1885) 7. How is the mean arterial pressure (MAP) calculated? Answer: Mean arterial pressure (MAP) is generally considered to be the patient’s blood pressure and takes into consideration the systolic blood pressure (SBP) as well as the diastolic blood pressure (DBP). Using the example of a patient who has a blood pressure of 120/60 mm Hg, the pulse pressure (difference between the systolic and diastolic pressures) would equal 60 mm Hg (120 mm Hg ? 60 mm Hg = 60 mm Hg). To calculate the MAP, take one third of the pulse pressure and add the diastolic pressure to it (20 + 60 = 80 mm Hg). The equation is as follows: MAP = DBP + 1/3 ( SBP ? DBP) (p 1887) 8. What is the difference between aerobic metabolism and anaerobic metabolism? Answer: In aerobic metabolism, all of the cells’ processes occur with adequate oxygen supply. In anaerobic metabolism, all of the cells’ processes occur in the absence of oxygen. Cells switch to anaerobic metabolism when they do not have enough oxygen available to them. The switch causes the production of lactic acidosis and shifts the oxygen-hemoglobin dissociation curve to the right to increase tissue oxygen delivery. This shift in the curve also decreases cardiac function and makes the heart more susceptible to the effect of the circulating catecholamines. (p 1891) 9. What is MODS? Answer: Multiple-organ dysfunction syndrome (MODS) is a progressive condition characterized by combined failure of two or more organs or organ systems that were initially unharmed by the acute disorder or injury that caused the patient’s current illness. Six organ systems are surveyed when you are diagnosing MODS: the respiratory, hepatic, renal, hematologic, neurologic, and cardiovascular systems. Each system is assigned a score to determine the patient’s overall risk. (p 1894) 10. What is obstructive shock and what are two examples of traumatic causes? Answer: Obstructive shock occurs when blood flow in the heart or great vessels becomes blocked. Causes are those not directly associated with loss of fluid, pump failure, or vessel dilation. Two examples of obstructive shock causes in trauma are tension pneumothorax and cardiac tamponade. (p 1906) Unit Assessment 1. What is the periarrest period? 2. What is a premorbid condition? 3. What does the M-T SHIP acronym stand for? 4. How can you communicate what your intuition tells you to others on your team? 5. What are the two types of bias in decision making? 6. What is shock? 7. How is the mean arterial pressure (MAP) calculated? 8. What is the difference between aerobic metabolism and anaerobic metabolism? 9. What is MODS? 10. What is obstructive shock and what are two examples of traumatic causes?