A 40-year-old woman comes to the clinic for routine follow-up. She currently feels well. The patient has a history of Henoch-Schönlein purpura since childhood, resulting in stable chronic kidney disease with a baseline creatinine of 2.2-2.4 mg/dL and low-grade proteinuria (

Question

A 40-year-old woman comes to the clinic for routine follow-up.  She currently feels well.  The patient has a history of Henoch-Schönlein purpura since childhood, resulting in stable chronic kidney disease with a baseline creatinine of 2.2-2.4 mg/dL and low-grade proteinuria (<1 g/day).  She has hypertension, which is managed well with lisinopril and hydrochlorothiazide.  Blood pressure is 126/84 mm Hg and pulse is 80/min.  Examination shows no evidence of volume overload.  Laboratory results are as follows:  Her potassium level 4 weeks ago was 5.3 mEq/L.  Urine albuminuria is unchanged from that time.  In addition to dietary counseling, what is the best next step in management of this patient's current condition?

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Explanation: 11ec25c8_d4e3_fa3d_bc81_e7dcdb161b01_MD0003_00 Patients with chronic kidney disease (CKD) are usually treated with a renin-angiotensin system inhibitor (eg, lisinopril) to slow progression to end-stage renal disease. However, a common complication of this class of medication, particularly in the setting of CKD, is chronic mild or moderate hyperkalemia. Although medication-induced hyperkalemia is generally treated with discontinuation of the offending medication, the benefit of renin-angiotensin system inhibitors in patients with CKD generally outweigh the risk of chronic hyperkalemia; therefore, the medication is usually continued and the hyperkalemia is treated separately. Urgent treatment (eg, calcium gluconate, insulin plus glucose) of hyperkalemia is indicated in the setting of hyperkalemic emergency, which is marked by serum potassium >6.5 mEq/L, rapid escalation in serum potassium during tissue breakdown, or symptomatic hyperkalemia (eg, ECG changes, cardiac arrhythmia). Patients who do not have hyperkalemic emergency, as in this patient with a moderate, chronic elevation of potassium and a creatinine level that is at baseline, do not require urgent treatment (unless they have concomitant oliguria or endstage renal disease). They are generally managed with a low-potassium diet (eg, <40-70 mEq/day) and avoidance of other medications (eg, nonsteroidal anti-inflammatory drugs) that raise serum potassium. Patients also frequently receive an oral cation exchange agent (eg, patiromer, zirconium cyclosilicate). These insoluble compounds bind potassium in the colon in exchange for calcium or sodium and are then excreted in the stool, thereby eliminating potassium from the body. Patients with CKD who are hypervolemic also sometimes receive a thiazide (eg, hydrochlorothiazide) or loop diuretic (eg, furosemide), which increase potassium excretion in the urine. (Choice A) Losartan, a renin-angiotensin system inhibitor, is likely to cause a degree of hyperkalemia similar to that of lisinopril. (Choice B) Hemodialysis is indicated for patients with end-stage CKD who have severe hyperkalemia and require urgent removal of potassium. This patient has moderate CKD and mild hyperkalemia; she can be managed with outpatient therapies such as diet modification and oral patiromer. (Choice C) Intravenous calcium (eg, calcium gluconate) is used in patients with hyperkalemic emergency to rapidly stabilize muscle membranes while longer-term therapies (eg, patiromer) take hold. Oral calcium is not generally used for chronic hyperkalemia. (Choice E) Sodium bicarbonate can lower serum potassium by moving hydrogen out of cells, thereby generating an electrochemical gradient for potassium to move intracellularly. However, it has limited efficacy in lowering the serum potassium, even in patients with metabolic acidosis. Educational objective: Patients with chronic kidney disease taking renin-angiotensin system inhibitors often develop chronic mild or moderate hyperkalemia. This is typically managed with a low-potassium diet and an oral cation exchange agent (eg, patiromer, zirconium cyclosilicate), which binds to potassium in the colon and is subsequently excreted in feces.

A 40-Year-Old Woman Comes to the Clinic for Routine Follow-Up