Effect of preoperative amino acid infusion on thermoregulatory response during spinal anaesthesia.
BACKGROUND
Intravenous amino acid infusion during general anaesthesia prevents decreases in core temperature resulting from increased energy expenditure and heat accumulation.


METHODS
We investigated whether such stimulation also occurs during spinal anaesthesia, which blocks sympathetic nervous activity. We examined the effect of i.v. amino acid infusion on changes in core temperature during spinal anaesthesia. Thirty-five patients were divided into two groups: an i.v. amino acid infusion group (4 kJ kg(-1) h(-1) starting 2 h before surgery); and a saline infusion group. Tympanic membrane core temperature, forearm-fingertip temperature gradient (an index of peripheral vasoconstriction) and mean skin temperature were measured for 90 min after the onset of spinal anaesthesia.


RESULTS
Changes in mean arterial pressure and heart rate did not differ significantly between the groups during the study period. Mean final core temperature 90 min after induction of spinal anaesthesia was 35.8 (SEM 0.1) degrees C in the saline group and 36.6 (0.1) degrees C in the amino acid group (P<0.05). The increased level of oxygen consumption in the amino acid group compared with the saline group was preserved even after the onset of spinal anaesthesia. The thermal vasoconstriction threshold, defined as the tympanic membrane temperature that triggered a rapid increase in forearm-fingertip temperature gradient, was increased in the amino acid group [36.8 (0.1) degrees C] compared with the saline group [36.5 (0.1) degrees C] (P<0.05).


CONCLUSIONS
Preoperative infusion of amino acids effectively prevents spinal anaesthesia-induced hypothermia by maintaining a higher metabolic rate and increasing the threshold core temperature for thermal vasoconstriction.
Kasai
T
T
Department of Anaesthesiology, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Nakajima
Y
Y
Matsukawa
T
T
Ueno
H
H
Sunaguchi
M
M
Mizobe
T
T
D000328:Adult; D000368:Aged; D000596:Amino Acids / Q000008:administration & dosage*; D000704:Analysis of Variance; D000775:Anesthesia, Spinal / Q000379:methods*; D001794:Blood Pressure / Q000502:physiology; D001833:Body Temperature Regulation / Q000187:drug effects* / Q000502:physiology; D004734:Energy Metabolism; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007263:Infusions, Parenteral; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D011300:Preoperative Care / Q000379:methods; D011446:Prospective Studies
D000596:Amino Acids