ELECTROLYTE QUIZ

The answers to the electrolyte quiz for June 14, 2012 are 1. A, 2. D, 3. C, 4. B, 

The Questions

For each patient with hyperkalemia described below, select the best option (A-E) for treatment of their serum potassium.

A. Thiazide diuretic

B. Hydrocortisone

C. Insulin

D. Hemodialysis

E. Sodium polystyrene sulfonate

1. 43-year-old man with Type II diabetes mellitus, hypertension, congestive cardiac failure, nephrotic-range proteinuria, and a serum creatinine of 1.6 mg/dL. His serum potassium has been in the range of 5.6-5.9 mEq/L since starting captopril, despite adhering to a potassiumrestricted diet.

2. 88-year-old woman who had partial colectomy for perforated diverticular abscess and septicemia two days previously, and has been anuric since the operation. Her serum potassium is 6 mg/dL.

3. 18-year-old man with no prior medical history who presents with one week of polyuria and polydipsia.

Laboratory Studies

Serum sodium 132 mEq/L

Serum potassium 5.9 mEq/L

Serum chloride 91 mEq/L

Serum bicarbonate 16 mEq/L

Blood urea nitrogen 56 mg/dL

Serum creatinine 2.2 mg/dL

Serum glucose 330 mg/dL

4. 26-year-old woman with acquired immune deficiency syndrome, fatigue, weight loss, lowgrade fever, and orthostatic hypotension.

Serum cortisol level:

Baseline at 8 AM7 mcg/dL 

(nL 5-24 mcg/dL)

30 minutes after 250 10 mcg/dL mcg cosyntropin i.m.

60 minutes after 250.11 mcg/dL mcg cosyntropin i.m.

Explanation

The 43-year-old man likely has diabetic nephropathy and hyporeninemic hypoaldosteronism. He is volume-expanded and loop or thiazide diuretics are a useful way to correct his potassium and volume simultaneously. The 88-year-old with postoperative anuric acute renal failure requires dialysis. Enteral administration of a potassium-binding resin is contraindicated, and no other measure will remove potassium from her body. The 18-year-old man has newly-diagnosed diabetes and diabetic ketoacidosis. The hyperkalemia is due to shift of potassium from the intracellular to extracellular space, which can be readily reversed with insulin, and his renal failure is largely due to hypovolemia and may be reversible with fluid replacement. His whole body potassium content is actually reduced and any measures that remove potassium from the body would risk subsequent development of hypokalemia once insulin therapy is initiated. The 26-year-old woman has primary adrenal insufficiency, which can occur in patients with acquired immunodeficiency syndrome due to infectious agents such as cytomegalovirus or mycobacteria, and drugs such as ketoconazole and rifampin. Although her baseline serum cortisol level is normal, it fails to rise appropriately (increment from baseline > 7 mcg/dL, or 30 minute level > 15 mcg/dL) after administration of cosyntropin. Replacement with hydrocortisone is therefore indicated.

(Courtesy of Dr. Alan Yu, Professor of Medicine, University of Kansas Medical Center)