A randomized cross-over study of the metabolic and hormonal responses following two preoperative conditioning drinks

Preoperative conditioning with carbohydrate-based drinks attenuates postoperative insulin resistance and leads to clinical benefits. The use of metabolic conditioning agents such as glutamine and antioxidants, in addition to carbohydrate, may benefit patients undergoing major surgery, because glutamine and antioxidant supplementation have been shown to improve gastrointestinal perfusion, immune function, morbidity, and gluco-metabolic control in critically ill patients. We investigated the postprandial responses after ingestion of a clear carbohydrate drink (CCD) containing 50 g of carbohydrate (preOp, Nutricia, Trowbridge, UK) and that of another drink containing 50 g of carbohydrate, 15 g of glutamine, and antioxidants (ONS; Fresenius Kabi, Bad Homburg, Germany).

Twelve overnight-fasted healthy male subjects ingested one of the drinks in a randomized, double-blinded, cross-over manner, after which blood was sampled for 360 min for measurement of glucose, insulin, glucagon, non-esterified fatty acids, β-hydroxybutyrate and glutamine.

The means ± standard errors for age and body mass index of participants were 21 ± 0.9 y and 23.2 ± 0.5 kg/m(2). After CCD ingestion, glucose and insulin concentrations peaked within 40 min (8.4 ± 0.4 mmol/L and 43.9 ± 3.8 mIU/L, respectively) and returned to baseline at 80 min (glucose 4.9 ± 0.3 mmol/L) and 140 min (insulin 5.5 ± 0.5 mIU/L). After ONS ingestion, peak glucose and insulin concentrations occurred within 40 min but were of a lower magnitude (6.6 ± 0.1 mmol/L and 29.6 ± 2.9 mIU/L, respectively). Glucose concentrations after ONS were higher than after CCD at 100 min.

Peak insulin and glucose concentrations were higher after CCD ingestion; in contrast, responses after ONS ingestion were "blunted" and prolonged.