BB and K

Q: Beta Blockers (BB) tend to cause? (select one)

A) Hypokalemia 

B) Hyperkalemia

Answer: B

This question emphasizes the concept that catecholamines with beta-2 receptors, like epinephrine, promote the movement of extracellular potassium into the cells. Similarly, beta-adrenergic blockers impair potassium entry into the cells. Although total body potassium stays the same, high serum potassium levels lead to hyperkalemia (so it is not real hyperkalemia).

This effect is most pronounced with nonselective beta-blockers, such as propranolol or labetalol, and less with beta-1 selective, such as atenolol or metoprolol.

On an average, it increases potassium by about 0.5 meq/L . It is usually not significant, but it can become life-threatening in patients with underlying hypoaldosteronism, heart failure exacerbation, renal insufficiency, and a history of renal transplant.

#electrolytes

#pharmacology

References:

1. Reid JL, Whyte KF, Struthers AD. Epinephrine-induced hypokalemia: the role of beta adrenoceptors. Am J Cardiol 1986; 57:23F.

2. Nowicki M, Miszczak-Kuban J. Nonselective Beta-adrenergic blockade augments fasting hyperkalemia in hemodialysis patients. Nephron 2002; 91:222.

3. McCauley J, Murray J, Jordan M, et al. Labetalol-induced hyperkalemia in renal transplant recipients. Am J Nephrol 2002; 22:347.