Transcript
Chapter 16: Sensory Motor Complications of Acute Illness
Chapter Summary
Decreased LOC, abnormal mentation, and sleep disturbances are common problems in high-acuity patients. These complications increase length of hospital and ICU stay, time on mechanical ventilation, and mortality. There are two components of consciousness: arousal (wakefulness) and awareness (responsiveness).
The presence of anxiety and insomnia contributes to development of cognitive dysfunction and altered mentation. Treatment may consist of low doses of benzodiazepines; however, these drugs are used with caution to prevent oversedation and accumulation of active metabolites.
Delirium is an acute-onset confusional cognitive disorder characterized by attention deficits, fluctuating mental status, and either disordered thinking or altered LOC. There are many potential causes of delirium (e.g., drug-induced, infectious, toxins). It is differentiated from dementia, which has a slower insidious onset and causes long-term memory impairment.
Delirium can clinically present as a change in patient behaviors that is hyperactive, hypoactive, or a combination of the two. Delirium may result from imbalances in neurotransmitters that modulate cognition, behavior, and mood. Septic encephalopathy is a particular type of delirium that can be an early sign of sepsis (systemic infection).
Assessment and monitoring of delirium should include use of a valid assessment tool, such as the CAM-ICU. Prevention of delirium begins with identifying patients who are at risk. Interventions to prevent delirium may include early correction of abnormalities in metabolic parameters and oxygenation, correction of fluid and electrolyte imbalances, ensuring adequate rest, and providing appropriate stimulation. Pharmacologic interventions should begin with a review of all current medications and may include use of antipsychotic agents, benzodiazepines, or dexmedetomidine for symptom management.
Coma is a persistent state of unresponsiveness from which the patient cannot be aroused. It is often reversible. Common causes are brain injuries (e.g., stroke, hemorrhage) and cardiac arrest. Drug-induced coma, a therapy occasionally used in critical care units, uses deep sedation to reduce oxygen consumption when moderate therapies are inadequate. Two severe forms of coma are persistent vegetative state (PVS), where the patient maintains arousal but has lost awareness components of consciousness, and brain death, the irreversible loss of all brain and brainstem functions.
Bedside assessment of a patient with coma includes a focused neurological assessment and the Glasgow Coma Scale. Eliciting a response from a comatose patient usually requires use of noxious (painful) stimuli. Major goals of treatment are to prevent further neurologic deterioration and to correct the underlying problem.
Critical illness polyneuropathy (CIP) and critical illness myopathy (CIM) are complications of acute and critical illness that result in neuromuscular weakness. CIP is an acute axonal sensorimotor polyneuropathy that affects the lower limbs. It is characterized by sensory abnormalities in pain, temperature, and vibration. Critical illness myopathy (CIM) is a spectrum of muscle disorders characterized by diffuse weakness, depressed DTRs, and mildly elevated CK enzyme levels.
Neuromuscular blockade agents (NMBAs) produce skeletal muscle paralysis. In critical care, NMBA use is reserved for life-threatening conditions where there is a need to eliminate skeletal muscle movement (e.g., decrease oxygen consumption, control mechanical ventilation). NMBAs do not reduce pain or decrease anxiety; therefore, patients who are placed on NMBAs are also placed on a sedative/hypnotic (e.g., propofol) and analgesia (e.g., fentanyl). The paralyzed patient is unable to breathe spontaneously and must be intubated and placed on mechanical ventilation, using a full breathing support mode such as Assist/Control. Train of four (TOF) testing should be performed to monitor level of paralysis to prevent under- and overdosing.
New-onset seizures refer to seizures that occur in patients with no previous history of seizure disorder. Common causes are drug intoxication or withdrawal, infection, brain trauma or lesions, and systemic metabolic derangements. Tonic–clonic seizures are a type of generalized event involving the entire cerebral cortex.
Status epilepticus refers to seizures that are continuous for more than 5 minutes or seizures that recur without a recovery of consciousness. The most common cause of status epilepticus is subtherapeutic anticonvulsant drug levels. Status epilepticus is considered a medical emergency and requires rapid drug interventions to prevent permanent brain injury. Drugs that may be used include benzodiazepines, hydantoins, and possibly a barbiturate.
