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This in vivo study confirmed impaired hemostasis during hypothermia in a swine model. Group I (normothermic, n = 8) and group II (hypothermic, n = 8) animals were anesthetized and instrumented for continuous peritoneal irrigation and monitoring of heart rate and blood pressure. The effects of hypothermia, hypotension, and inotrope on bleeding time and bleeding from two types of arterial injuries were evaluated. Our findings were that (1) bleeding time was significantly prolonged in hypothermic animals; (2) the differences in blood loss from partially torn artery (PTA) and completely cut artery (CCA) at both normothermic and hypothermic temperatures did not reach statistical significance; and (3) blood loss from PTA was greater than CCA when norepinephrine (Levophed) was infused to elevate blood pressure in hypotensive animals at normal core temperature.

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.