Amino acid-induced thermogenesis to prevent hypothermia during anesthesia is not associated with increased stress response.

Abstract

Intraoperative infusion of amino acids stimulates oxygen uptake with a resulting increase in heat production, especially during emergence from anesthesia. To determine whether the increased thermogenesis in response to amino acid infusion during and after anesthesia induces any additional stress in surgical patients, plasma catecholamines were measured. Fourteen patients aged 44+/-15 yr scheduled for gall bladder surgery during isoflurane anesthesia were studied. Seven patients received an IV amino acid infusion at the rate of 126 mL/h throughout anesthesia, and seven control subjects received equal volumes of nutrient-free saline. At five defined times during and after anesthesia, arterial adrenaline and noradrenaline concentrations were determined. Arterial blood pressure and heart rate were recorded simultaneously. There were considerable variations from baseline in levels of plasma adrenaline and noradrenaline, heart rate, and blood pressure during the study period, but there were no significant differences between the two groups at any time throughout anesthesia and surgery. In conclusion, the augmented thermogenic effect of amino acids during and at emergence from anesthesia is suggested to occur without imposing any additional stress in the surgical patient. Amino acid infusion during anesthesia has been demonstrated to markedly increase oxygen consumption and heat production. To determine whether this evokes any stress in the patients, we measured plasma catecholamines during anesthesia. We suggest that temperature preservation during anesthesia by an amino acid infusion occurs without additional sympathoadrenal activity.