• E Selldén, D Rimeika, and G Settergren.
• Department of Surgical Sciences, Karolinska Institute, Division of Anaesthesia and Intensive Care, Karolinska University Hospital, Solna, Stockholm, Sweden. eva.sellden@ks.se
• Acta Anaesthesiol Scand. 2005 Jan 1;49(1):35-40.

BackgroundIn abdominal surgery and in healthy volunteers, amino acids increased thermogenesis. In this double-blind study we investigated if a similar effect would ensue in heart surgery and accelerate the rewarming process postoperatively.MethodsThirty-four patients undergoing coronary artery bypass grafting or aortic valve replacement were randomized into two groups, and received either 500 ml of amino acids or Ringer's solution intravenously during 4 h. The infusion was started approximately 30 min before the end of a cardiopulmonary bypass (CPB), performed at a temperature of 34 degrees C with rewarming to 36-37 degrees C. The lowest pulmonary artery (PA) temperature after the CPB and the time interval until the temperature reached 37 degrees C were recorded. Oxygen uptake was calculated from cardiac output (thermodilution) and the pulmonary av-difference of oxygen after induction of anaesthesia, at the end of surgery, and 1 and 2 h after the CPB.ResultsDemographic data, medication including beta-blockers, CPB data and case mix were similar. The lowest temperature after the CPB was 35.9 +/- 0.1 degrees C in the amino acid group and 35.6 +/- 0.2 degrees C in the control group, and the increase per hour was 0.6 +/- 0.1 degrees C and 0.6 +/- 0.0 degrees C, respectively, with no differences between the groups. During the infusion, oxygen uptake was higher in the amino acid group, 115 +/- 4 ml m(-2), than in the controls, 102 +/- 3 ml m(-2) (P < 0.05). No adverse effects of the infusions were noted.ConclusionThe lack of a thermal effect of the amino acids in the heart surgery was most probably due to the temperature gradients between the different body compartments, and also may have been due to the use of beta-blockers.

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