DISCUSSION:
Our patient has undergone a renal transplant for stage 5 chronic kidney
disease and was already on hemodialysis for the past 1 year. The
preoperative, intraoperative course was fair with no significant
concerns. The early postoperative course of the patient was
satisfactory. As a part of prophylaxis to Pneumocystis jiroveci and
Cytomegalovirus in solid organ transplant, we have started Cotrimoxazole
(TMP-SMX) and Valganciclovir respectively from postoperative day-5. On
day-10, the serum Potassium was 6.0 mEq/L and increased to 6.2 mEq/L by
day 11. The serum creatinine was 2.86 mg/dl on day-0 and 2.11 mg/dl on
day-1 which returned to the normal range by day-3. On day-10 and 11,
levels of serum creatinine were 0.54 mg/dl and 0.66 mg/dl respectively
which were in the normal range, signifying normal renal function. Though
the serum urea levels of the patient were consistently higher than the
normal range (6-24 mg/dl), the BUN/Cr ratio was consistently higher than
20. We attributed it to inadequate hydration as the creatinine was
normal. We gave intravenous fluids judiciously as he is a known patient
of ischemic heart disease. He is not on any other drugs that could cause
hyperkalemia except Cotrimoxazole (TMP-SMX). Trimethoprim inhibits
sodium transport in the apical membrane of the distal nephron, reducing
the transepithelial voltage causing decreased potassium secretion,
similar to amiloride.2 A study conducted by
Rana
M Al AdAwi et al about the incidence of cotrimoxazole-induced
hyperkalemia in tertiary care showed 28% regardless of interacting
drugs and 33% without interacting drugs. 3 Though
hyperkalemia by TMP-SMX is common in patients with renal insufficiency,
it can even occur in patients with normal renal
function4 and with standard dose5.
Similarly, More AS et al presented a case of TMP-SMX induced
hyperkalemia in renal transplant6. Serum potassium
levels are monitored regularly in patients receiving TMP-SMX in the long
term, especially in at-risk patients because the serum levels may rise
even higher than 6.5 mEq/L6. Following the observation
of hyperkalemia in this patient, Cotrimoxazole has been withheld from
day 11 as well as the Potassium chloride syrup that he has been
receiving since day 6. The effect of potassium chloride syrup on
hyperkalemia in this patient was ruled out since he is receiving a
standard dose from 4 days prior to the observation with a normal range
of daily serum potassium levels. The study of R Alagappan et al showed a
statistically significant increase in serum potassium levels in patients
after 5 days of treatment with TMP-SMX.7 The patient
was treated with intravenous fluids and potassium binders in the
hospital from day 11-13 in addition to withholding TMP-SMX and potassium
chloride syrup. In addition to routine discharge medications, he was
discharged with potassium binders twice daily until the next follow-up.
The follow-up serum potassium levels showed 4.2 mEq/L.