The effect of various cardioplegic procedures on myocardial oxygen consumption in normo- and hypothermia.

The effect of various cardioplegic procedures on the myocardial oxygen consumption was investigated by the direct method of Warburg. Potassium citrate and Young's solution markedly enhanced the oxygen consumption of the heart muscle of both normal and low temperature groups. Acetylcholine and adenosine triphosphate in a low concentration slightly increased the oxygen consumption, but higher concentrations of adenosine triphosphate markedly inhibited the respiration of the heart muscle. Potassium chloride had an inhibitory action on the myocardial oxygen consumption. The heart muscle under hypothermic cardioplegia showed a very close relationship between oxygen consumption and endogenous myocardial respiration.