[Experimental study of coronary reactive hyperemia--effects of hypothermia and potassium cardioplegia].

A hyperemic response on dog hearts following myocardial ischemia for 10 minutes has been studied in reference to myocardial protection with cardioplegia and hypothermia. Experimental animals were divided into four groups according to the difference in temperature and with or without cardioplegia during ischemia of the hearts. Group I (n = 7) succumbed to a normothermic ischemia. Group II (n = 6) had normothermic ischemia following infusion of 8 ml/kg of a normothermic cardioplegic solution. Group III (n = 7) had ischemia under moderate hypothermia (28 degrees C). Group IV [n = 7) had hypothermic ischemia following infusion of 8 ml/kg of hypothermic cardioplegic solution. A percent repayment of the flow debts in groups I, II, III, and IV were 234.6 +/- 38.3%, 101.5 +/- 40.8%, 134.5 +/- 50.0% and 112.8 +/- 36.5%, respectively. There was significant difference between group I and group II and IV (p less than 0.001) and group III (p less than 0.02). Peak flow in reactive hyperemia compared with control flow were 605.4 +/- 131.1%, 328.3 +/- 60.2%, 288.8 +/- 79.7% and 282.2 +/- 65.4% in each group I, II, III, and IV, respectively. The value in group I was significantly high in comparison with others (p less than 0.005). Depression of oxygen consumption was observed in groups with hypothermia as well as with cardioplegia. A hyperemic response was low in cardioplegia and/or hypothermia group. These data are suggestive of a beneficial use of cardioplegia and hypothermia on cardiac surgery through the observation of coronary reactive hyperemia after myocardial ischemia.