BACKGROUND The aim of this study was to investigate the oxygen consumption of explanted aerobically-perfused cardioplegic porcine hearts at different temperatures. MATERIAL AND METHODS Explanted hearts from 30 pigs weighing 50 kg were randomized into 5 groups. The hearts received continuous antegrade perfusion within a temperature-controlled sealed system. The perfusate consisted of an albumin-containing hyperoncotic cardioplegic nutrition solution with erythrocytes to a hematocrit of 10%. Five temperatures were studied: 37, 30, 22, 15, and 8°C. When the erythrocytes in the perfusate were fully saturated, the oxygenator was excluded from the circuit and blood gases were analyzed periodically until the erythrocytes had desaturated to less than 20%. Between 80% and 60% saturation the desaturation curves were linear in all groups and the oxygen consumption was calculated from this part of the curves. RESULTS The weight of the hearts was 208±4 g (mean ±SEM, n=30). The oxygen consumption in mL/min/100 g heart tissue was (mean ±SEM, n=6 in each group) 37°C: 1.10±0.04; 30°C: 0.58±0.02; 22°C: 0.33±0.01; 15°C: 0.21±0.01; and 8°C: 0.16±0.02. CONCLUSIONS The oxygen consumption of the cardioplegic perfused pig heart at normothermia was 1.1 mL/min/100 g and was reduced by 85% to 0.16 mL/min/100 g at 8°C.