Objective: We compared the metabolic effects of postoperative total parenteral nutrition (TPN) and hypocaloric glucose after treatment with oral carbohydrates preoperatively and epidural anesthesia to proactively minimize postoperative insulin resistance.
Methods: Thirteen patients undergoing colorectal resections were given oral carbohydrates preoperatively and epidural anesthesia and randomized to TPN or hypocaloric glucose during and after surgery. Insulin sensitivity (hyperinsulinemic clamp [0.8 mU x kg(-1) x min(-1)], normoglycemic clamps [4.5 mM]), and glucose kinetics (6,6(2)H2-D-glucose), were studied before and on postoperative day 3. Indirect calorimetry was performed and nitrogen excretion in urine was measured. Values are presented as mean +/- standard deviation. Analysis of variance, planned comparison, and Bonferroni's correction were used for statistical analysis.
Results: Three days after surgery insulin-stimulated whole-body glucose disposal decreased by 24 +/- 11% versus 28 +/- 23% in patients receiving TPN and hypocaloric glucose, respectively (P < 0.05 for both, not significant between groups). Endogenous glucose production during insulin stimulation was increased only in the glucose group after surgery (P < 0.05 versus before). After surgery, insulin-stimulated glucose oxidation was higher after treatment with TPN, whereas fat oxidation was lower (P < 0.05 for both versus glucose treatment). Fat oxidation increased in the glucose group at basal after surgery (P < 0.05 versus before). Nitrogen balance was less negative after treatment with TPN (P < 0.01).
Conclusions: Treatment with TPN does not seem to improve postoperative peripheral insulin sensitivity in patients with minor insulin resistance after pretreatment with preoperative carbohydrates and perioperative epidural anesthesia. Hypocaloric nutrition results in changes in substrate utilization and nitrogen balance resembling starvation, whereas TPN attenuates these changes.