Effects of hypothermia on hemodynamic responses to dopamine and dobutamine.

Hemodynamic characteristics, arrhythmogenicity, and dose-related hemodynamic responses to intravenous dopamine (group I) and dobutamine (group II) were examined in 16 swine at three different core body temperatures (38.5 degrees C, 35 degrees C, and 30 degrees C). The animals were anesthetized with isoflurane and mechanically ventilated. Cooling and re-warming were accomplished by a femoral-jugular A-V shunt. The animals were cooled down to 30 degrees C and stabilized for 1 hour before intravenous infusion of dopamine (group I, n = 8) or dobutamine (group II, n = 8) was started at 2, 5, 10, 15, 20, and 30 micrograms/kg/min. Hemodynamic responses to the two inotropes were continuously monitored with a bedside monitor equipped with a PC mode for customized data collection and analysis. Computerized arrhythmia detection was performed. Our findings were: (1) profound hypothermia (30 degrees C) causes significant depression of hemodynamic functions; (2) IV infusion of dopamine and dobutamine can be used safely and effectively for inotropic support during profound hypothermia, and the optimal dosage for improving cardiac output is 10-20 micrograms/kg/min; (3) no risk of inducing arrhythmia was noted with IV infusion of both inotropes up to a maximum dosage of 30 micrograms/kg/min, even though significant sinus tachycardia was consistently seen at 30 micrograms/kg/min.