[Study of hypothermic anesthesia--cardiac contractility during hypothermia]

We studied cardiac function during hypothermia, and effects of various methods of anesthesia on hearts taken from guinea pigs which received extracorporeal circulation by Langendorff method. Morphine, fentanyl citrate and halothane were used as anesthetics. Morphine and fentanyl citrate were added to the infusate at the dose of 3 mg.kg-1 or 50 micrograms.kg-1. Halothane 1% was introduced into the infusate by bubbling. Left ventricular peak dp/dt was measured as an index of cardiac contractility. Halothane depressed cardiac contractility most at normal temperature, and this was changed by cooling. Cardiac contractility with both morphine and fentanyl citrate was similar, and showed significant advantage over halothane at 30 degrees C, 25 degrees C and 20 degrees C. Coronary arterial blood flows at 30 degrees C, 25 degrees C and 20 degrees C were in the order of halothane greater than fentanyl citrate greater than morphine. The result suggests that oxygen consumption of myocardium under halothane anesthesia, even during hypothermia is high.