| Objective To establish a mongrel model to observe the perioperative effects of intraoperative amino acid administration on glycometabolism,protein metabolism,lipid metabolism and dose-effect relationship.Methods Thirty-six healthy adult mongrels were randomly allocated to one of four groups(n=9),received ileectomy with anastomosis under general anaesthesia.Every mongrel was infused intraoperatively with 0.9%sodium chloride solution(NS group), amino acid 6 kJ·kg-1·h-1(6 kJ group),amino acid 12 kJ·kg-1·h-1(12 kJ group),or amino acid 24 kJ·kg-1·h-1(24 kJ group).The mongrels were monitored and studied until 24h after surgery,under sedation,muscle relaxation,analgesia and mechanical ventilation. The vital signs were stable during the experiment.The esophagus core temperature were assessed every 10 rain during surgery and hourly after surgery.The selected 11 results of plasma insulin,glucagons,glucose,lactate,free fatty acids,triglyceride and ketobodies were compared before anaesthesia,after induction,after 15 min,30 min,60 min into surgery,at the end of surgery and 1h,2h,4h,8h,24h after surgery.Homa Index was used to estimate the degree of insulin resistance.Muscle biopsies were taken from the lateral portion of the vastus lateralis from the left leg after anaesthesia,at the end of surgery and 24h after surgery,liver biopsies were taken just before close the abdomina and 24h after surgery.Muscle glycogen,hepatic glycogen and muscle amino acid pattern were measured.The urine was collected respectively before,during and after surgery and the urinary urea and urinary 3-methylhistidine excretion were measured.The nitrogen balances were calculated.SPSS 15.0 was used to analyze the differences among and within groups for repeated measurement during experiment(core temperature,plasma concentrations of hormones and metabolic substrates,glycogen of muscle and liver, nitrogen balance,urinary 3-methylhistidine excretion and muscle amino acid pattern). Changes of temperature,plasma insulin,glucose,free fatty acids,and the nitrogen balance,3-methylhistidine excretion after surgery were related to the dose of amino acid in order to calculate the dose-effect relationship by regression analysis.Results(1) The gender,weight,surgery duration,bleeding,fluid replacement during and after surgery were not different significantly in all the groups(P＞0.05).(2) The perioperative esophagus core temperature in all the groups were significantly lower than basal until 9h after surgery(P＜0.05),while the core temperature were higher in 12 kJ group and 24 kJ group than in NS group(P＜0.05).(3) Compared with NS group,the plasma insulin concentrations increased in 24 kJ group(36.27±23.40μIU/ml in NS group,130.96±57.26μIU/ml in 6 kJ group,196.34±84.46μIU/ml in 12 kJ group and 539.62±108.15μIU/ml in 24 kJ group at the end of surgery,P＜0.05),whereas plasma glucagons concentrations did not change(P＞0.05).Homa Index increased in every group(P＜0.05) and most significantly in 24 kJ group(P＜0.05).(4) Plasma glucose increased significantly during and after surgery(P＜0.05),which was most in 24 kJ group with quickest reversion(6.29±1.27 mmol/l in NS group,7.66±2.47 mmol/l in 6 kJ group,8.71±1.96 mmol/l in 12 kJ group and 10.32±3.01 mmol/1 in 24 kJ group at the end of surgery;7.29±2.02 mmol/l in NS group,6.69±2.13 mmol/l in 6 kJ group, 7.27±2.27 mmol/l in 12 kJ group and 5.13±1.16 mmol/l in 24 kJ group 2h after surgery),while lactate was not significant different among groups(P＞0.05).Muscle glycogens and hepatic glycogens decreased 24h after surgery(P＜0.05) and were not different significantly among groups.(5) Negative nitrogen balance was most serious after surgery than preoperative in NS group(P＜0.05),while alleviation was found in other three groups(-8.33±2.14 g/24h in NS group,-5.51±0.92 g/24h in 6 kJ group, -4.42±0.84 g/24h in 12 kJ group and -0.73±1.04 g/24h in 24 kJ group,P＜0.05).The urinary excretion of 3-methylhistidine was increased significantly after surgery in NS group(30.11±10.94μg/24h versus 85.76±26.75μg/24h,P＜0.05) and 6 kJ group (25.62±12.74μg/24h versus 68.73±34.56μg/24h,P＜0.05),unchanged in 12 kJ group (26.32±12.78μg/24h versus 44.04±20.48μg/24h,P＞0.05) and decreased significantly in 24 kJ group(23.40±9.86μg/24h versus 7.44±3.08μg/24h,P＜0.05).The muscle branched-chain amino acids and aromatic amino acids were increased significantly 24h after surgery than basal in NS group(P＜0.05),while unchanged in all other three groups. (6) Plasma free fatty acids decreased significantly during and after surgery,and significant lower in 12 kJ and 24 kJ group than NS group at the end of surgery(0.253±0.066 mmol/l in NS group,0.223±0.160 mmol/l in 6 kJ group,0.089±0.064 mmol/l in 12 kJ group and 0.129±0.054 mmol/l in 24 kJ group,P＜0.05).Plasma triglyceride concentrations were increased significantly after induction(P＜0.05),but not different significantly among all groups(P＞0.05).Ketobodies were all negative.(7) The dose-effect relationship between the dose of amino acid with the decrease of temperature at the end of and 2h after surgery were negative correlation and quadratic regression;with the increase of plasma insulin were positive correlation and quadratic regression;with the increase of blood glucose,the nitrogen balance after surgery and the decrease of plasma free fatty acids were positive correlation and linear regression;with the 3-methylhistidine excretion after surgery were negative correlation and linear regression.Conelusions(1) Intraoperative low dose of amino acid administration can't prevent hypothermia after surgery,while medium to high dose of amino acid have similar effect of preventing hypothermia.(2) Intraoperative amino acid administration increases insulin secretion,however does not prevent the glycogenolysis.Low to medium dose of amino acid does not increase the plasma glucose concentration.High dose of amino acid increases the plasma glucose concentration significantly,while decreasing to the base level quickly.(3) Intraoperative amino acid administration doesn't increase urinary urea excretion,can alleviate the negative nitrogen balance,decrease urinary 3-methylhistidine excretion and the catabolism of skeletal muscles 24h after surgery.(4) Intraoperative amino acid administration has no effect of lipid synthesis.Medium to high dose of amino acid can inhibit fat mobilization without creating excess ketobodies or causing ketonemia. (5) The preferred dose of intraoperative amino acid administration on heathy adult mongrel is about 12 kJ·kg-1·h-1.
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