Changes in whole body and tissue oxygen consumption during recovery from hypothermia: effect of amino acid infusion.

Objective: To study the effects of amino acids on whole body and peripheral energy metabolism during recovery from post-operative hypothermia.

Design: Clinical study using three randomly assigned patient groups.

Setting: ICU of a university hospital.

Patients: Nineteen elective coronary bypass operation patients.

Interventions: Postoperatively, either glucose alone, glucose and a conventional amino acid solution, or glucose and a branch-chain amino acid enriched solution was infused. After ICU arrival (period 1) both conventional amino acid solution and branch-chain amino acid enriched solution groups received 0.15 g/kg-day of nitrogen as a conventional amino acid mixture (20% branch-chain amino acids). After rewarming (period 2), both groups received 0.18 g of nitrogen/kg-day for 2 hrs (branch-chain amino acid content 20% in the conventional amino acid solution and 35% in the branch-chain amino acid enriched solution), and for the following 2 hrs (period 3), 0.22 g of nitrogen/kg-day (branch-chain amino acid content 20% in the conventional amino acid solution and 50% in the branch-chain amino acid enriched solution).

Measurements And Main Results: Whole body oxygen consumption (VO2) increased during period 1 and continued to increase during period 2 (baseline, 133 +/- 20 mL/min.m2; period 1, 152 +/- 12 mL/min.m2; period 2, 158 +/- 21 mL/min.m2; period 3, 153 +/- 15 mL/min.m2; p less than .05, period 1 vs. baseline). VO2 in the leg increased during period 1 but remained constant thereafter (baseline, 16 +/- 8 mL/min.m2; period 1, 26 +/- 14 mL/min.m2; period 2, 23 +/- 6 mL/min.m2; period 3, 24 +/- 10 mL/min.m2; p less than .05, period 1 vs. baseline). Amino acid infusions had no thermogenic effect. A two-phase redistribution of VO2 and leg VO2 suggested increased visceral VO2 after rewarming.

Conclusion: The amino acid infusions had no effect on the leg uptake of glucose, ketone bodies, and pyruvate and the leg release of lactate, free fatty acids, and triglycerides, which remained constant during the study.