The effects of open heart surgery on growth hormone, cortisol and insulin levels in man. Hormone levels during open heart surgery.

Plasma growth hormone, cortisol, insulin and blood glucose concentrations were measured intra- and postoperatively in ten patients who underwent open heart surgery with moderate hypothermia. Diazepam-ketamine anaesthesia for 10-20 min failed to precipitate any significant alterations in the levels of measured hormones and blood glucose. In the pre-bypass period of surgery, an increase in cortisol and a slight elevation in growth hormone levels was observed; insulin level showed no change in spite of marked hyperglycaemia. The bypass period, including hypothermia and haemodilution, was accompanied by unchanged cortisol and elevated growth hormone levels, while insulin demonstrated a slight rise which did not correspond with the degree of hyperglycaemia. The post-bypass period with rewarming the restoring spontaneous circulation was characterized by further marked increase in cortisol and growth hormone levels and, in spite of decreasing levels of blood glucose, by a paradoxical elevation in plasma insulin. It is suggested that hypothermia, haemodilution, reduced tissue perfusion affecting endocrine glands, as well as denaturation of some hormones in the oxygenator, participate in the moderate endocrine response, disproportionate to the stress of cardiopulmonary bypass surgery. The rise in hormone levels on terminating bypass seems to be dependent on the improved blood flow to endocrine glands due to recovered spontaneous circulation, rewarming and, as for insulin, presumably even on the reduced inhibitory effect of catecholamines.