Blog | Monday, April 22, 2019

Confusion after gastric bypass with Roux-en-Y

At a recent case conference, we discussed a woman who had had a gastric bypass 20 years previously, and now had confusion. To remind you of the details of a gastric bypass:
First, a small stomach pouch, approximately one ounce or 30 milliliters in volume, is created by dividing the top of the stomach from the rest of the stomach. Next, the first portion of the small intestine is divided, and the bottom end of the divided small intestine is brought up and connected to the newly created small stomach pouch. The procedure is completed by connecting the top portion of the divided small intestine to the small intestine further down so that the stomach acids and digestive enzymes from the bypassed stomach and first portion of small intestine will eventually mix with the food.

I posed this question on Twitter, but unfortunately did not give enough specification of the problem. Restated, a patient with progression confusion presents years after the procedure (very successful at weight loss) and no apparent infection.

Our leading differential included hyperammonemic encephalopathy, thiamine deficiency, B12 deficiency and d-Lactic acidosis.

We excluded d-Lactic acidosis become the symptoms were not episodic and the electrolyte panel did not have a moderately increased anion gap (usually around 18). A B12 level was normal, excluding that possibility.

The patient did have both hyperammonemia and thiamine deficiency. She also had several vitamin B deficiencies and low levels of copper, zinc and selenium.

After adequate replacement, her confusion eventually improved.

The problem of hyperammonemia is very dangerous. This paragraph from a recent article explains it well:
Patients presenting with hyperammonemic encephalopathy after Roux-en-Y gastric bypass surgery presented with overlapping clinical and laboratory findings. Common features included: (1) weight loss following successful Roux-en-Y gastric bypass for obesity; (2) hyperammonemic encephalopathy accompanied by elevated plasma glutamine levels; (3) absence of cirrhosis; (4) hypoalbuminemia; and (5) low plasma zinc levels. The mortality rate was 50%. Ninety-five percent of patients were women.

Likely the zinc deficiency is a major culprit here. Studies of the ornithine transcarbamylase cycle show that zinc is an important co-factor. Like to many patients with successful bypass surgery the patient presented was not taking supplementary vitamins with trace metals. Several companies make vitamins labeled as bariatric vitamins that have adequate trace metal supplementation.

The patient presented at our conference eventually did well after receiving supplementation that included zinc.

db is the nickname for Robert M. Centor, MD, MACP. db stands both for Dr. Bob and da boss. He is an academic general internist at the University of Alabama School of Medicine, and the former Regional Dean for the Huntsville Regional Medical Campus of UASOM. He still makes inpatient rounds regularly at the Birmingham VA and Huntsville Hospital. His current titles are Professor-Emeritus and Chair-Emeritus of the ACP Board of Regents. This post originally appeared at his blog, db's Medical Rants.