Blood cardioplegia (BCP) has been reported as a superior method of myocardial protection, because of its oxygenating and buffering potential, but it is unknown which temperature is most effective. This study was performed to investigate the efficacy of continuous warm blood cardioplegia (CWBCP) versus continuous cold blood cardioplegia (CCBCP) in regard to metabolism, serum enzyme release, cardiac function and edema. Fourteen adult mongrel dogs were subjected to total cardiopulmonary bypass and cross-clamp of the aorta for 120 minutes, and followed by 60 minutes' reperfusion. The dogs were divided into two groups according to the differences of BCP temperature: Group W, 33 degrees C warm BCP, and Group C, 16 degrees C cold BCP with topical cooling. Myocardial oxygen extraction during aortic cross-clamping was significantly higher in group W than in group C. Changes in excess lactate (delta XL) and redox potential (delta Eh) of lactate and pyruvate showed that aerobic metabolism could be maintained in group W and could not in group C. Lipid peroxides (LPO) were measured in coronary artery and sinus blood at the same time, so generations of LPO (A-Cs difference) at 5 minutes after reperfusion were significantly lower in group C than in group W (-0.140 +/- 0.125 nmol/ml V.S. 0.019 +/- 0.093). The incidence of ventricular fibrillation after reperfusion was significantly lower in group W than in group C (1/7 V.S. 7/7). CPK-MB and HBDH releases were significantly lower in group W than in group C during aortic clamp and 60 minutes' reperfusion (47 +/- 15 IU/l, 138 +/- 72 V.S. 94 +/- 24, 229 +/- 71).(ABSTRACT TRUNCATED AT 250 WORDS)