Blog | Friday, October 19, 2012

Guess the diagnosis of an acid-base problem-part 2


To recap, recently I heard about this patient: A man with a history of ulcerative colitis and PSC who had had both a colectomy with end ileostomy and liver transplant in the past. Now he presents with dyspnea and fatigue and increased stool output.

Your job is to let me know how to evaluate the patient further and define the acid-base problem.

VS P 90 R 20 BP 95/70 T afebrile, otherwise the exam is normal:
129,103,82,140
6.2,11,6.2,7.6
albumin 2.7

pH:7.27

pCO2: 26

pO2: 105

calc HCO3: 12

Have fun! Part 3 will come out next Friday.

My thoughts at morning report are:
Pure metabolic acidosis with perfect compensation,
Anion gap = 15, but should be around 8 (rough rule of thumb alb * 3),0
Therefore delta gap is 7.

If we add back the delta gap to the observed bicarbonate, I concluded that the patient had a mild AG acidosis superimposed on a normal gap acidosis.

I could not decide between a renal acidosis (type IV with elevated K) or a diarrhea acidosis, therefore I asked for urine lytes.

I asked for the medications of prednisone 5mg daily, tacriiimus, a PPI and Immodium.

Your next job is to guess the urine lytes and tell me how this added information influences your thinking.

db is the nickname for Robert M. Centor, MD, FACP. db stands both for Dr. Bob and da boss. He is an academic general internist at the University of Alabama School of Medicine, and is the Associate Dean for the Huntsville Regional Medical Campus of UASOM. He also serves as a frequent ward attending at the Birmingham VA Hospital. This post originally appeared at his blog, db's Medical Rants.