Hyperkalemia in an AIDS Patient with PCP
Case Report
Synopsis: An AIDS patient suffered a potentially lethal complication of therapy for Pneumocystis carinii pneumonia.
A 39-year-old hiv-infected male with a histo-ry of alcoholism was admitted to the hospital with fever, cough, and interstitial infiltrates on chest radiograph. He was remarkably noncompliant with his antiretroviral medication and prophylactic dapsone, and his CD4 cell count had fallen to 86/mm3. Serum electrolytes on admission were remarkable—for a sodium, 136 meq/mL; potassium, 3.2 meq/mL; and creatinine, 0.6 mg/dL. Because of a history of sulpha allergy, he was started on trimethoprim (320 mg every 8 hours) plus dapsone (100 mg/d) for presumed Pneumocystis carinii pneumonia (PCP), as well as oral potassium supplements 20 meq twice daily.
By the sixth day of therapy, he was much improved, but his serum potassium level had increased to 6.4 meq/mL. His serum creatinine was unchanged. He was given intravenous fluids and the potassium supplements were held. The next morning his potassium was even higher, at 6.7 meq/mL, with evidence of peaked T waves on electrocardiogram requiring intravenous fluid bolus, an ampule of D50, and kayexalate. Within four hours, a repeat serum potassium was decreased to 5.4 meq/mL. However, the next morning, his serum potassium was again elevated at 6.6 meq/mL. What was going on?
Comment by Carol A. Kemper, MD
Trimethoprim-sulfamethoxazole (TMP-SMX), even at standard dosages, is known to cause hyperkalemia, especially in patients with renal insufficiency, but this is the first time I’ve ever seen such a dramatic example of this potential complication. Up to 62.5% of hospitalized patients receiving standard-dose TMP-SMX (320 mg/day TMP) developed peak serum concentrations of potassium greater than 5.7 meq/mL, and severe hyperkalemia (> 6.2 meq/mL) occurred in 21%.1 Patients with serum creatinine more than 1.2 mg/dL were at particular risk. One randomized, controlled study comparing patients receiving standard dose, orally administered TMP-SMX vs. other antibiotics as outpatient therapy for a variety of infections found a statistically significant increase in serum potassium levels after five days of TMP-SMX therapy.2 Only 6% of the patients in this study developed severe hyperkalemia (> 6.2 meq/mL). Patients older than 50 years of age were at significant risk for hyperkalemia, and there was also a trend toward elevated potassium levels in those with renal insufficiency or diabetes.
AIDS patients receiving TMP-SMX may also be at risk for hyperkalemia, especially those with renal impairment or aldosterone insufficiency. This may be due to the higher doses required for PCP treatment, as well as the fact that serum creatinine levels do not adequately reflect the degree of renal impairment in HIV-infected patients with wasting. The exact nature of the mechanism of action is not clear, but may be due to renal tubular acidosis.3 And, as this case suggests, it may be due to the antifolate antagonist and not the sulpha moiety.
In this case, the patient’s anti-PCP treatment was changed to primaquine plus clindamycin, and his hyperkalemia promptly resolved within two days.
References
1. Alappan R, et al. Hyperkalemia in hospitalized patients treated with trimethoprim-sulfamethoxazole. Ann Intern Med 1996;124:316-320.
2. Alappan R, et al. Trimethoprim-sulfamethoxazole therapy in outpatients: Is hyperkalemia a significant problem? Am J Nephrol 1999;19:389-394.
3. Sheehan MT, Wen SF. Hyperkalemic renal tubular acidosis induced by trimethoprim-sulfamethoxazole in an AIDS patient. Clin Nephrol 1998;50:188-193.
The hyperkalemia in an AIDS patient with PCP was resolved with administration of which of the following treatments?
a. Prednisone
b. Trimethoprim plus dapsone
c. Primaquine plus clindamycin
d. Pentamidine
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