Effects of central bolus injections of potassium chloride on arterial potassium concentration in patients undergoing cardiopulmonary bypass.

The effects of central venous bolus injections of potassium chloride (KCl) on arterial potassium concentration were studied in patients undergoing cardiopulmonary bypass. Ten subjects were studied, and each received a rapid bolus injection of KCl, 33 microEq/kg, both before and after cardiopulmonary bypass. Injections were delivered through the proximal infusion port of a 7.5F pulmonary artery catheter, which was situated in either the superior vena cava or the right atrium. Monitored variables included the electrocardiogram, mean arterial, central venous, and pulmonary artery pressures, end-tidal carbon dioxide and inspired oxygen concentrations, and temperature. Blood was sampled continuously at either the radial artery alone or both the radial artery and aortic root at 2 mL/4.3 s. The difference in magnitude between the maximal potassium concentration achieved and the prebolus baseline potassium concentration (delta K) was correlated with cardiac output, stroke volume, and prebolus baseline potassium concentration (baseline [K+]), using simple linear regression analysis. Although significant hyperkalemia (eg, 7 to 9 mEq/L) developed in both the aortic root and radial artery, this was of no electrocardiographic or hemodynamic consequence, presumably because of the transient nature of the hyperkalemic response, following bolus injection of KCl. There was no significant correlation between delta K and cardiac output or stroke volume; however, delta K did correlate significantly with the Baseline [K+] in a direct linear relationship. It is concluded that central bolus injections of KCl through the proximal infusion port of the pulmonary artery catheter at 33 microEq/kg are safe. This technique should be used cautiously in patients with extremely low cardiac outputs or where intracardiac shunting of blood may exist, as these situations could potentially result in greater hyperkalemic responses than those observed in the current study.