Comparative studies of pulsatile and nonpulsatile flow during cardiopulmonary bypass. III. Response of anterior pituitary gland to thyrotropin-releasing hormone.

Previous studies have indicated that, during nonpulsatile cardiopulmonary bypass, the anterior pituitary gland fails to respond to the tropic stimulus of thyrotropin-releasing hormone (TRH). This is in contrast to the normal response seen during closed cardiac and general surgical procedures. The Stöckert pulsatile pump system described in Part I has been employed in a comparative study of TRH responses in 20 patients subjected to pulsatile or nonpulsatile perfusion during open-heart surgery. In the nonpulsatile group, a consistently subnormal response to TRH injection was again found. In the pulsatile group, however, the pituitary response to TRH was normal in nine patients out of 10. The quantitative difference between the groups was statistically highly significant (p less than 0.005). These results indicate that the subnormal pituitary function seen with nonpulsatile bypass may be prevented by the use of pulsatile perfusion.

Adrenocortical hormone concentrations in children during cardiopulmonary bypass with and without pulsatile flow.

Plasma cortisol and ACTH concentrations were measured in two groups of children (aged 1-16 yr). Ten children underwent routine (non-pulsatile) cardiopulmonary bypass and 10 underwent pulsatile bypass under moderate hypothermia (28-32 degrees C). Comparable increases in cortisol and ACTH concentrations were demonstrated at the onset of bypass and the concentrations of both hormones increased during bypass. In the post-bypass period plasma cortisol concentration increased sharply; there was no further increase in the plasma ACTH concentration. By 24 h the concentrations of both hormones had declined towards baseline values. There were no significant differences between the groups.