HDCN Mini Grand Rounds

An unusual cause of metabolic alkalosis in a chronic hemodialysis patient

From: John Brennan, M.D., David J. Leehey, M.D., and Todd S. Ing, M.D.
Renal and Hypertension Section, Hines Veterans Affairs Hospital, Hines, IL

Case Report

A 64-year-old hemodialysis patient presented to the emergency department with a complaint of cough with sputum production over the previous three days. In addition he had a marked exacerbation of his longstanding chronic hiccups. For these he only found relief with an over-the-counter preparation of BromoseltzerTM, of which he had consumed an entire bottle during the previous 48 hours.

(Each bottle of Bromoseltzer contains 120 grams of medication. Each dose (3/4 capful) contains 0.325 g of acetaminophen, 2.781 g sodium bicarbonate, 2.224 g of citric acid, and a small unquantified amount of sugar.)

He denied any history of vomiting. His past medical history was significant for hypertension for many years, diabetes mellitus with diabetic retinopathy and nephropathy. He was on hemodialysis for two years, three times per week using a standard bicarbonate bath of 35mM. His last dialysis had been two days prior to his admission.

Other medications at the time of admission were lisinopril 20mg po bid, metoclopramide 10mg po bid, diltiazem SR 240mg qd, calcium acetate 338 mg po tid, clonidine 0.2 mg po bid, iron, and vitamins.

Physical examination
This revealed a 64-year-old alert and oriented man distressed secondary to frequent hiccups. Blood pressure was 170/100mm Hg, temperature 100.2 F, pulse 108/min, and respirations 24/min. He weighed 86.4kg. His usual postdialytic "dry" weight was 83kg. There were mild bibasilar lung crackles. The apical impulse was displaced to the anterior axillary line, and 2/6 systolic ejection murmur was heard. The abdomen was mildly distended but soft, nontender, and without evidence of organomegaly; bowel sounds were normal. There was 1+ edema noted in his left lower extremity and a prosthesis on his right. He had a functioning left forearm arteriovenous graft. His neurological exam was normal except for decreased sensation noted in a stocking pattern in the left lower extremity.

Laboratory values:
Initial serum values (in mM) were as follows:

sodium 143
potassium 3.5
chloride 89
total CO2 36
glucose 11.3
BUN 16
creatinine 1.0

The serum calcium and phosphorus levels were normal. WBC was 8.1, Hgb 9.6, Hct 32.0, and platelets 230K.

On admission his arterial blood gas on room air showed:

pH 7.53
PCO2 47 mmHg
PO2 59 mm Hg
HCO3 40 mmol/L

On 3L oxygen by nasal cannula, repeat ABG yielded:

pH 7.48
PCO2 51
PO2 75
HCO3 38

Questions

1. Assuming the 120 oz bottle of Bromoseltzer contained 23 doses of 3/4 capfuls of product, with each capful containing 2.781 grams of sodium bicarbonate, what would be the expected serum bicarbonate be in a 85 kg anephric patient who consumed an entire bottle abruptly? Assume a serum bicarbonate level of 20 mmol/L which corresponds to the approximate predialysis total CO2 measured for our patient on his monthly dialysis labs for the previous five months.

a. 25 mM
b. 32 mM
c. 38 mM
d. 45 mM

2.Of what additional concern are over the counter medications containing citric acid in the dialysis population?

a. Metabolic alkalosis from citrate
b. Enhanced stomach acidity
c. Increased absorption of aluminum
d. Chelation of calcium with resultant hypocalcemia

3.What bicarbonate bath concentration is appropriate in this patient?

a. 35 mM
b. 28 mM
c. 0 mM

CONTINUE

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