Insulin, growth hormone and catecholamines as regulators of energy metabolism in the course of surgery

Abstract

Six patients subjected to major surgery (esophageal resection, group I) and eight patients undergoing moderate surgery (exploratory laparotomy, group II) were investigated in order to study the effects of surgery and glucose infusion on the blood glucose, plasma FFA, serum insulin and growth hormone concentrations as well as on the urinary excretion of adrenaline, noradrenaline and nitrogen. In the patients undergoing esophageal resection, blood samples were taken at short intervals during five 24-hour periods, covering a time span from the second preoperative to the tenth postoperative day. In the case of exploratory laparotomy four such periods up to fifth postoperative day were similarly investigated. For adrenaline, noradrenaline and nitrogen, urine was collected in two 12-hour samples for each 24-hour period in order to roughly estimate the "day" and "night" excretions. The results and conclusions can be summarized as follows: A rapid rise in blood glucose and plasma FFA concentrations occurred after the beginning surgery. The zeniths of the curves were recorded about 4--6 hours after the skin incision in both patient groups, despite the different duration of the operations. This suggests that the regulatory mechanism is spontaneously active for a certain time after being initially triggered. Insulin secretion was usually suppressed 4--5 hours after the beginning of surgery. A marked increase of insulin secretion occurred after this time, the rise of IRI being associated with a fall of BG and FFA. Maximum insulin secretion was recorded during the night after surgery. Because excretion of noradrenaline was maximal during this time in group I, noradrenaline activity is perhaps a less likely explanation of the suppression of insulin. The response of growth hormone secretion to surgery and anesthesia was not uniform. Trauma apparently causes no constant rise, whereas a rather regular elevation of serum GH levels follows the fall in BG and plasma FFA concentrations, In group I there was a decrease of insulin and GH secretion and the number of insulin and GH "peaks" in the postoperative period, possibly reflecting a weakening of central stimuli after major surgery. The same was not always noted in group II, in which the mean secretion of insulin was postoperatively somewhat elevated compared to the preoperative values. Urine analyses revealed no day--night rhythmicity in catecholamine excretion except possibly on the day of operation, when the "day" samples contained absolutely and proportionately more adrenaline than the "night" samples.