Myocardial respiration and edema following hypothermic cardioplegia and anoxic arrest

The effects of 1 and 2 hours of hypothermic anoxic arrest and cardioplegia induced by Mg-lidocaine, K-Mg, or K on left ventricular mitochondrial respiratory function, blood flow, and edema were studied in 41 mongrel dogs. Mitochondrial respiration was assessed by the indices of oxidative phosphorylation. Myocardial temperature recorded in ventricular septum was kept at 20 degrees C during ischemic arrest and 10 minutes of reperfusion. Cardioplegic solutions did not influence noncoronary blood flow during cross-clamping of the aorta. Mitochondrial respiratory function remained at control levels after 1 hour of ischemia induced by hypothermic anoxic arrest or by Mg-lidocaine or K-Mg hypothermic cardioplegia. Mitochondrial state 3 respiration after 2 hours of anoxic arrest was significantly higher in Mg-lidocaine cardioplegia than in anoxic arrest (p less than 0.05), but myocardial edema was equivalent in both groups. Mg in the cardioplegic solution suppressed mitochondrial nonphosphorylating oxygen consumption. These data suggest that mitochondrial function after 1 hour of ischemic arrest at 20 degrees C and 10 minutes of reperfusion is not significantly depressed, but at 2 hours of ischemic arrest, mitochondrial respiration is significantly impaired. However, hypothermic Mg-lidocaine cardioplegia appears to be more effective in sustaining myocardial respiration than does simple hypothermic anoxic arrest when the anoxic period is extended to 2 hours.