Isotopic studies during surgical convalescence

We have performed paired isotopic studies in four patients undergoing resection of early colorectal cancer and four having removal of parathyroid adenomas. Kinetic measurements of protein and glucose metabolism were made before resection and at home 10 weeks after surgery. During convalescence there were major changes in both groups in glucose metabolism and the hormonal milieu despite no alterations in protein kinetics or metabolic rate. In particular, the rate of glucose production doubled from (mean +/- s.e.m.) 14.8 +/- 1.3 to 28.1 +/- 2.5 mumol kg-1 min-1 (P less than 0.01), the percentage of available glucose undergoing oxidation decreased from 35.5 +/- 3.9 to 21.5 +/- 2.9 per cent (P less than 0.05) and the percentage of glucose undergoing recycling to lactate increased from 20.1 +/- 10.0 to 52.9 +/- 2.3 per cent (P less than 0.05). During convalescence the basal plasma insulin concentration was significantly higher (P less than 0.05) and there was a proportionately smaller response to glucose infusion. The convalescent state was also associated with an elevation in serum cortisol from 291 +/- 54 to 496 +/- 75 nmol litre-1 (P less than 0.05). The values for resting energy expenditure were not significantly different from the predicted energy expenditure in either the preoperative or the convalescent groups. We conclude that (a) there is a marked increase in both glucose production and glucose recycling to lactate in convalescence from clean uncomplicated surgery, and this is associated with a decrease in the percentage of glucose uptake oxidised; (b) a relative hyperinsulinaemia is seen in convalescent patients and is associated with decreased responsiveness to a glucose load; (c) the plasma cortisol level is significantly elevated after 10 weeks of convalescence; and (d) convalescent patients do not have elevated rates of protein catabolism or energy expenditure.