Lack of nonshivering thermogenesis in infants anesthetized with fentanyl and propofol

摘要: Background: Sweating, vasoconstriction, and shivering have been observed during general anesthesia. Among these, vasoconstriction is especially important because-once triggered-it minimizes further hypothermia. Surprisingly, the core-temperature plateau associated with appears to preserve core temperature better in infants children than adults. This observation suggests that anesthetized may be accompanied by hypermetabolism. Consistent this theory, unanesthetized rely on nonshivering thermogenesis double heat production when alone insufficient. Accordingly, authors tested hypothesis intraoperative hypothermia triggers infants. Methods: With Ethics Committee approval written parental consent, studied six undergoing abdominal surgery. All were aged 1 day 9 months weighed 2.4–9 kg. Anesthesia was maintained propofol fentanyl. The mechanically ventilated allowed cool passively until (distal esophageal) temperatures reached 34–34.5 degrees Celsius. Oxygen consumption-the authors' index of metabolic rate- recorded throughout cooling. Because triples circulating norepinephrine concentrations, arterial blood analyzed for plasma catecholamines at [nearly equal] 0.5 Celsius intervals. Thermoregulatory evaluated using forearm - fingertip, skin-surface gradients, gradients exceeding 4 Celsius, indicating intense vasoconstriction. patients subsequently rapidly rewarmed 37 Regression analysis used correlate changes oxygen consumption catecholamine concentrations temperature. Results: vasoconstricted time 36 Further reduction did not increase consumption. Instead, decreased linearly. Hypothermia also failed concentrations. Conclusions: Even 2 below threshold, there no evidence thermogenesis. finding surprising because all other major thermoregulatory responses detected Infants thus appear similar adults being unable rate response mild