Metabolic aspects of postoperative care

Foster, Kenneth John (1979) Metabolic aspects of postoperative care. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

In a survey of 167 patients undergoing abdominal surgery it was noted that 70% of patients with a low measure of muscle protein,before gastric, pancreatic or colonic operations, developed postoperative complications. The metabolic disturbances arising from operation and measures to diminish nitrogen excretion were therefore evaluated. Compared with fasting volunteers, patients had modestly increased nitrogen excretion, but marked increase in urine 3 methyl-histidine excretion, suggesting increases in both muscle protein catabolism and protein resynthesis. Glucose infusion (1.5 g/kg body weight/day) profoundly altered blood metabolite concentrations but had little effect on nitrogen excretion, perhaps because of increased gluconeogenesis after operation. Infusion of mixed 1 amino acids, at the same rate, decreased circulating concentrations of ketone bodies,but diminished nitrogen excretion from 12.7 mmol/kg/day (SEM ± 1.4) in saline treated controls to a net balance of -1.7 mmol/kg/day (SEM ± 1.7). In patients with peritonitis amino acid infusions also decreased 3 methyl-histidine excretion.Total parenteral nutrition diminished net nitrogen loss after total cystectomy, but there was no improvement in recovery. It is concluded that although low preoperative protein reserves are associated with postoperative complications, postoperative measures to decrease nitrogen loss do not improve prognosis. The protein sparing effects of glucose and amino acids are least effective in the most severely catabolic patients. Infusion of amino acids alone markedly decreases nitrogen loss by various mehhanisms, but the effect of modest ketonaemia is relatively unimportant in this respect. The clinical use of amino acid infusions alone currently has no satisfactory foundation.

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