Transcript
CHAPTER 26
Clinical Reasoning Checkpoint Answers
Mr. T, a 52-year-old long-distance trucker with a history of hypertension and peptic ulcer disease, presents to the ED with a 7-day history of severe vomiting and abdominal pain. Mr. T’s weight is 80 kg. He states that during the previous week he has been able to eat very little food and tolerates only occasional sips of water. He has become progressively weaker and is dizzy as he tries to stand. He has not taken his antihypertensive medication (hydrochlorothiazide and metoprolol) for the past 3 days.
On physical exam, Mr. T. appears acutely ill, very weak, and pale. He has tenting of the skin over the clavicles, dry mucous membranes, weak peripheral pulses, flat jugular veins, and bilateral upper quadrant tenderness with palpation.
Parameter
Vital Signs (supine)
Vital Signs (sitting)
BP
96/50 mm Hg
72/38 mm Hg
HR
110/min/regular
140 min/regular
RR
24 bpm
Temp
99°F
An IV catheter was inserted 2 hours after his arrival in the ED, and a Foley catheter is inserted with a urine output of 150 mL. He last remembers voiding about 8 hours ago. His labs, drawn upon arrival in the ED, are as follows: Na 133 mEq/L, K 2.8 mEq/L, Cl 70 mEq/L, CO2 42 mEq/L, glucose 72 mg/dL, creatinine 4.2 mg/dL, BUN 108 mg/dL, hematocrit 51%, hemoglobin 17 gm/dL, WBC 10.2 103.
What do Mr. T.’s lab work and presenting features indicate?
Answer: Mr. T.’s lab work and presenting features indicate prerenal azotemia. His sodium (Na) is low, and creatinine (Cr) and blood urea nitrogen (BUN) are elevated.
Clinical Update: Mr. T was resuscitated with intravenous fluid and was taken to the operating room for surgical repair of a bleeding gastric ulcer. On post-op day 1, Mr. T.’s urine output has decreased to 250 mL over the preceding 12 hours, and his lab results are:
Electrolyte
ED admission # 1
Post-op day 1
Na
133 mEq/L
138 mEq/L
K
2.8 mEq/L
5.1 mEq/L
Cr
4.2 mg/dL
3.8 mg/dL
BUN
108 mg/dL
92 mg/dL
Hct
51%
31%
Hb
17 gm/dL
8.5 gm/dL
WBC
10.2 103
11 103
The nephrologist is called in for consult and recommends a fluid challenge.
2. What would be the purpose of administering fluids at this point?
Answer: He has signs and symptoms of decreased cardiac output and a shock state (orthostatic hypotension, tachycardia; history of dehydration over the past week, flat neck veins, dry mucous membranes). A fluid challenge will increase his overall fluid volume, and if his kidneys are still able to respond, his urine output will increase.
3. What is your interpretation of Mr. T’s BUN and creatinine?
Answer: Both BUN and creatinine are elevated, which could be due to dehydration. However, because urea is readily reabsorbed back into the blood from the renal tubules but creatinine is not, a ratio of BUN to creatinine greater than 20:1 indicates that there is still tubular reabsorption. Once the creatinine begins to rise significantly, the dysfunction is more severe.
Clinical Update: On post-op day 3, Mr. T. develops a temperature of 101.8°F and his urine output remains low, at 20–25 mL/hour. A diuretic challenge was done after fluids were administered. He does not respond to diuretics. His weight is 8 kg above his pre-op weight. Some labs are indicated below.
Values
Post-op day 1
Post-op day 3
Na
138 mEq/L
135 mEq/L
K
5.1 mEq/L
5.3 mEq/L
Cr
3.8 mg/dL
4.7 mg/dL
BUN
92 mg/dL
102 mg/dL
Hct
31%
28%
Hb
8.5 gm/dL
7.8 gm/dL
WBC
11 103
14.6 103
A chest x-ray and physical exam indicate right lower lobe (RLL) pneumonia.
4. Why is Mr. T at increased risk of pulmonary complications?
Answer: Respiratory complications, especially pneumonia, are a particular problem for the AKI patient. He has gained weight and therefore fluid volume, which can cause respiratory complications. In addition, his increasing uremia makes him susceptible to infection, due to a decrease in pulmonary macrophage activity. Kayexalate may be ordered.
5. You are concerned about Mr. T.’s potassium level. What treatment might you expect the health care provider to prescribe?
Answer: Mr T.’s potassium, BUN, and creatinine are elevated and his fluid overloaded. He would require dialysis or continuous renal replacement therapy. If he is hemodynamically stable, he might tolerate intermittent hemodialysis (IHD).
Clinical update: By postoperative day 6, Mr. T.’s respiratory infection and azotemia have worsened and his weight is now 14 kg above his pre-operative weight. He is transferred to the critical care unit, intubated, and placed on mechanical ventilation. The nephrologist recommends RRT.
6. Would intermittent hemodialysis (IHD) or continuous RRT (CRRT) be most helpful to Mr. T.?
Answer: If Mr. T.’s hemodynamic status could not tolerate IHD, then CRRT therapy would be the treatment of choice. Both therapies allow for removal of waste products, electrolytes, and fluid volume.
