Critical Care Medicine-Renal, Electrolyte and Acid Base Disorders>>>>>Potassium
Question 5#

A 30-year-old male with history of alcohol abuse presents with nausea and vomiting. He is jaundiced, agitated, and endorsing visual hallucinations. Vital signs are as follows:

• BP 105/100 mm Hg
• RR 22/min
• HR 110/min
• Temperature 38°C

Labs and ABG values are shown below:

Which of the following best describes the acid-base disorder?

A. Metabolic acidosis/respiratory alkalosis
B. Respiratory alkalosis
C. Combined respiratory alkalosis, metabolic acidosis, and metabolic alkalosis
D. Metabolic alkalosis and respiratory alkalosis

Correct Answer is C

Comment:

Correct Answer: C

The patient has a significant anion gap of 36 [138−(22 + 80) = 36], which makes high anion gap metabolic acidosis as one of the acid-base derangements even though the pH is alkalotic. Using Winters formula, the patient’s CO2 to compensate for the acidosis should be

This value is more than the pCO₂ of the patient which is 28, suggesting more CO₂ washout, thus adding respiratory alkalosis as a component of the acid-base disorder. Additionally, the patient’s albumin is 4, making the normal anion gap for this patient as 12; the difference between the normal anion gap and patient’s anion gap is 36 − 12 = 24. This means the acid-base disorder has caused the original bicarbonate level to decrease by 24. So, by adding 24 to the patient’s current bicarbonate level of 22, we can get the original bicarbonate level this patient started out with, which would be 22 + 24 = 46, thus making the patient’s original acid-base problem as metabolic alkalosis. The patient has a combined respiratory alkalosis, metabolic acidosis, and metabolic alkalosis.

Reference:

1. Berend K, De Vries APJ, Gans ROB. Physiological approach to assessment of acid–base disturbances. N Engl J Med. 2014;371:1434- 1445.