Levels of Circulating Norepinephrine and Epinephrine Before, During, and After Cardiopulmonary Bypass in Man

Little information is available on the levels of circulating catecholamines during cardiac surgery. A study was undertaken to measure the serum levels of epinephrine and norepinephrine before, during, and after cardiopulmonary bypass in 16 patients. Sampling were drawn before induction, after intubation, before bypass, 2 and 8 minutes after initiation of the bypass, and 20 minutes after bypass. The findings of this study show that the initiation of cardiopulmonary bypass was associated with a significant but transient fall in mean blood pressure accompanied by an increased secretion of adrenal epinephrine and norepinephrine. The cause of the observed hypotension may be due to an initial hemodilution of the circulating catecholamines by the 2 L. pump-priming solution. The secretion of adrenal catecholamines appears to be a compensatory response to the lowered blood pressure as indicated by the rapid return of the blood pressure in the ensuing minutes. Twenty minutes after bypass, both the blood pressure and serum catecholamine levels were observed to have returned to preinduction levels.