Peripheral Vascular Response to Potassium Administration during Cardiopulmonary Bypass

Potassium (K+) is often administered to patients during cardiopulmonary bypass (CPB). The effects of rapid K+ administration during CPB were studied in 30 adult patients. Each patient received one bolus dose (2, 4, 8, 12, or 16 mEq) of potassium chloride (KCl) (2 mEq/ml) during CPB. Serum K+ was significantly increased from baseline values at KCl doses of 8 mEq and larger (p less than 0.05). All increases in serum K+ returned to clinically acceptable levels within 5 minutes after the bolus. Mean arterial pressure (MAP) (torr) and total peripheral resistance (TPR) (dynes sec cm-5) changes were biphasic; after an initial transient decrease, maximal with the 16 mEq K+ bolus (MAP -21 +/- 6, TPR - 315 +/- 135), these parameters increased (8 mEq K+ bolus, MAP + 15 +/- 16, TPR + 301 +/- 90; 12 mEq K+ bolus, MAP + 43 +/- 9, TPR + 998 +/- 250; 16 mEq bolus, MAP + 51 +/- 9, TPR + 1,216 +/- 120) with a peak at 3 minutes after the bolus. Hypertension, in nine of 18 patients receiving a KCl bolus of 8 mEq or larger, was of such magnitude (range 132 to 196 torr) as to require rapid therapeutic intervention to lower blood pressure. When KCl supplementation is required on CPB and slow infusion rates seem unreasonable, bolus doses of less than 8 mEq may be administered without vascular effect.