In vitro study of hormone degradation by heart-lung machine with bubble oxygenator

In the present experiment with heart-lung machine set in a closed system in vitro, the blood containing increased levels of hormones was circulated at 30 degrees C for 90 min and at 37 degrees C for 30 min; a fraction of the priming perfusate was studied in parallel at the same temperatures in an incubator. The level of growth hormone decreased gradually to a mean of 76% at 30 degrees C and no further decrease was found at 37 degrees C. The mean insulin level fell within 30 min to 32% and no substantial further changes were observed during the remaining period of study; re-warming failed to produce significant additional changes. Cortisol did not change appreciably. However, the oxygenator altered the level of catecholamines markedly. At 30 degrees C the initial level of noradrenaline fell precipitously to 9% within 30 min and this excessively low level was sustained throughout the study. Adrenaline showed even more pronounced changes. Denaturation of dopamine was less marked falling to about 70% within 30 min. The present experiment revealed that the levels of hormones respond differently to artificial oxygenation during extracorporeal circulation. Cortisol resisted degradation by the oxygenator, while growth hormone and insulin were denatured significantly. The moderate degradation of growth hormone by the machine may not play an important role during open heart surgery. However, a marked oxidation denaturation of catecholamines by 90% and 70% and denaturation of insulin by 70%, might prove relevant during surgery.