Thermogenic effect of amino acids not demonstrated in heart surgery with cardiopulmonary bypass.
BACKGROUND
In 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.


METHODS
Thirty-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.


RESULTS
Demographic 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.


CONCLUSIONS
The 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.
Selldén
E
E
Department of Surgical Sciences, Karolinska Institute, Division of Anaesthesia and Intensive Care, Karolinska University Hospital, Solna, Stockholm, Sweden. eva.sellden@ks.se
Rimeika
D
D
Settergren
G
G
D000596:Amino Acids / Q000009:adverse effects / Q000494:pharmacology*; D001021:Aortic Valve / Q000601:surgery; D001831:Body Temperature / Q000187:drug effects*; D006348:Cardiac Surgical Procedures; D002315:Cardiopulmonary Bypass; D004311:Double-Blind Method; D004562:Electrocardiography; D004798:Enzymes / Q000097:blood; D005112:Extracorporeal Circulation; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D010092:Oximetry; D010101:Oxygen Consumption / Q000187:drug effects; D011182:Postoperative Care; D017694:Rewarming
D000596:Amino Acids; D004798:Enzymes