Cardiac metabolism and performance following cold potassium cardioplegia

The ability of cold potassium cardioplegia (CPC) to preserve cardiac metabolism and performance was evaluated in 68 patients undergoing anoxic arrest for aortocoronary bypass. Forty-five patients (group I) had a single dose of CPC inducing a mean myocardial temperature (MMT) of 32 degrees C/min. Twenty-three patients had multiple doses of CPC and systemic hypothermia to achieve a MMT of 22 degrees C/min. Arterial and coronary sinus sampling 38 minutes after aortic clamp removal permitted calculation of cardiac oxygen extraction, lactate production, CPK and CPK-MB release. Group I patients extracted less oxygen, produced more lactate, and released more CPK and CPK-MB. These indices of cardiac metabolism were found to correlate with anoxic times exceeding 30 minutes, and demonstrated more cardiac damage in group I patients at longer anoxic times. Serial measurements of cardiac output (thermodilution) and left atrial pressure during volume loading permitted construction of myocardial performance curves. Group I patients had a diminished response to volume loading postoperatively. Both the upslope and the highest stroke work attained were lower in group I and inversely related to the anoxic time. All patients made an uneventful recovery, indicating the insensitivity of clinical parameters of myocardial protection. Coronary sinus sampling and hemodynamic monitoring during volume loading permit an objective assessment of myocardial preservation.