Adequacy of the perfusate: Its influence on successful myocardial protection

Abstract

The hypothesis tested was that the composition of the prime and the perfusate at the time of reperfusion had an influence on postischemic cardiac performance. Twelve dogs in two equal groups had long (210 +/- 10 minutes) hypothermic (25 degrees +/- 1 degree C) perfusions. Each had 180 minutes of global ischemia and were given 500 ml of the same cold (4 degrees C) cardioplegic solution (CPS) every 45 minutes and topical hypothermia with a resultant average myocardial temperature of 10 degrees +/- 2 degrees C. Group A had a prime (1,958 ml) consisting of a 50/50 mixture of 5% dextrose in water and 5% dextrose in Ringer's injection to which mannitol (12.5 gm), furosemide (20 mg), and heparin (6,000 units) were added. Group B received a prime (1,868 ml) of 5% dextrose in Ringer's injection (1 L) and 750 ml of 6% helastarch in normal saline to which NaHCO3 (10 mEq), furosemide (20 mg), mannitol (25 gm), and heparin (6,000 units) were added. During perfusion, Group A received lactated Ringer's solution and Group B received a 1 : 2 portions of Ringer's injection and 6% helastarch. Additionally, Group B received additional furosemide and mannitol 5 minutes prior to the reperfusion interval. The results showed a marked difference between groups in postischemic cardiac recovery 120 minutes after cessation of cardiopulmonary bypass. The Group B dogs had statistically (less than 0.02) greater cardiac output, stroke volumes, and stroke work index at equal preloads and lower total peripheral resistances. Arterial systolic, diastolic, and mean pressures and right atrial pressures were not different. The Group A dogs required nearly threefold the volume of fluid additions required during bypass and twice the amount of NaHCO3 as Group B dogs. It is concluded that the composition of the prime and fluids used during bypass and use of agents to counteract tissue water accumulation during the ischemic and reperfusion intervals strongly influences postischemic cardiac performance. Further, these data suggest that the composition of the perfusate may have a greater influence on the functional recovery of the heart than the composition of various CPSs.