A 52-year-old man with alcoholic cirrhosis is admitted for worsening abdominal distension. He claims to have been compliant with his medications, which include spironolactone, furosemide, lactulose, propranolol, folic acid, and thiamine. He has no fever, chills, or abdominal pain. The patient has had no gastrointestinal bleeding in the past, but upper gastrointestinal endoscopy performed 6 months ago was consistent with grade 2 esophageal varices.
His temperature is 36.3 C (97.4 F), blood pressure is 115/70 mm Hg, and pulse is 90/min and regular. Tense ascites is present. His abdomen is nontender. There is 3+ pitting edema to the thighs bilaterally.
Laboratory results are as follows:

Which of the following is the most likely cause of this patient's acid-base disorder?

Question

A 52-year-old man with alcoholic cirrhosis is admitted for worsening abdominal distension.  He claims to have been compliant with his medications, which include spironolactone, furosemide, lactulose, propranolol, folic acid, and thiamine.  He has no fever, chills, or abdominal pain.  The patient has had no gastrointestinal bleeding in the past, but upper gastrointestinal endoscopy performed 6 months ago was consistent with grade 2 esophageal varices.
His temperature is 36.3 C (97.4 F), blood pressure is 115/70 mm Hg, and pulse is 90/min and regular.  Tense ascites is present.  His abdomen is nontender.  There is 3+ pitting edema to the thighs bilaterally.
Laboratory results are as follows:

Which of the following is the most likely cause of this patient's acid-base disorder?

Quizplus · Accepted Answer

This patient has a low serum bicarbonate concentration, the 2 main causes of which are metabolic acidosis and respiratory alkalosis. Determining the type of acid-base disturbance in this patient requires an arterial blood pH measurement. The patient has respiratory alkalosis (alkaline pH and low pCO₂), a common acid-base disturbance seen in hepatic cirrhosis caused by increased minute ventilation. The cause is unknown but may be related to increased progesterone and estradiol, which stimulate ventilation. Some patients with cirrhosis have hepatopulmonary syndrome, in which hypoxemia drives ventilation and produces respiratory alkalosis. This patient has chronic respiratory alkalosis, and the serum bicarbonate usually falls by 4 mEq/L for every 10 mm Hg reduction in the pCO₂. (Choice B) Liver metabolism of lactate is diminished in cirrhosis and can lead to an anion gap (Na - [HCO3 + Cl] = 129 - [18 + 100] =11) metabolic acidosis, which is not present in this patient. (Choice C) Gram-negative sepsis can be associated with respiratory alkalosis, but this patient has no symptoms or signs suggesting sepsis (eg, hypotension, tachycardia). (Choice D) Lactulose-induced diarrhea usually leads to a non-anion gap metabolic acidosis (due to intestinal bicarbonate loss). Although this patient has a normal anion gap and a serum bicarbonate of 18 mEq/L, the serum pH indicates alkalemia and makes this option less likely. (Choice E) Spironolactone inhibits renal tubular effects of aldosterone and usually causes a non-anion gap metabolic acidosis, which is not present in this patient. Furosemide generally causes increased distal delivery of sodium, increased aldosterone secretion, and a metabolic alkalosis. Educational objective: Patients with cirrhosis can have chronic respiratory alkalosis due to increased minute ventilation. The cause is unknown but may be the result of the hormonal effects of increased progesterone and estrogen or possibly due to hepatopulmonary syndrome in some patients. __________ References: Alterations in arterial blood parameters in patients with liver cirrhosis and ascites. (http://www.ncbi.nlm.nih.gov/pubmed/17396160) The hyperventilation of cirrhosis: Progesterone and estradiol effects. (http://www.ncbi.nlm.nih.gov/pubmed/8985264) Abnormal hyperventilation in patients with hepatic cirrhosis: role of enhanced chemosensitivity to carbon dioxide. (http://www.ncbi.nlm.nih.gov/pubmed/20851482)

A 52-Year-Old Man with Alcoholic Cirrhosis Is Admitted for Worsening