Figure 77-13 Glucose concentration and glucose clearance (i.e., glucose uptake/glucose concentration) in postoperative patients on total parenteral nutrition. There is a progressive rise in glucose clearance, and after 6 days of infusion, the glucose concentration is significantly lower than at 2 hours of infusion, even though the infusion rate is much higher at 6 days. Glucose production is suppressed in normal volunteers by exogenous glucose infusion. During the first 2 hours of glucose infusion, suppression of glucose production appears to be of predominant importance in maintaining normal blood glucose concentration. Maximal suppression can be obtained at glucose infusion rates well below rates conventionally administered in total parenteral nutrition. (Adapted from Wolfe RR: Regulation of glucose metabolism. In Burke JF [ed]: Surgical Physiology. Philadelphia, WB Saunders, 1983, p 75.)