THE EFFECTS OF HYPOTHERMIC AND NORMOTHERMIC CARDIOPULMONARY BYPASS ONGLYCERYL TRINITRATE ACTIVITY

Glyceryl trinitrate (GTN) is used to control arterial blood pressure d uring cardiopulmonary bypass (CPB) procedures, but its effects are oft en decreased during the period of extracorporeal support. The plasma a nd urine concentrations of GTN and glyceryl-1,2-dinitrate (1,2-GDN) an d glyceryl-1,3-dinitrate (1,3-GDN) for male and female patients who re ceived GTN during hypothermic CPB, and male and female patients who we re given GTN during normothermic CPB, were measured by gas-liquid chro matography. During hypothermic CPB, the male and female subjects exper ienced significant decreases in GTN clearance (P < 0.05), 66% and 52%, respectively. Neither the males nor the females who underwent normoth ermic CPB experienced any significant change in GTN clearance. These r esults suggest that the lower core temperature during hypothermic CPB may decrease the biotransformation of GTN to GDNs and nitric oxide, th ereby resulting in less dilation of blood vessels. Furthermore, the ma les in the hypothermic CPB group had significantly greater urinary con centrations of 1,3-GDN and 1,2-GDN than the females (P < 0.05), and th e normothermic CPB males had a significantly greater urinary concentra tion of 1,2-GDN than the females in that group. The normothermic CPB m ales also had significantly higher plasma concentration of GTN at two time points, and 1,3-GDN at one time point, than the females. These da ta suggest that there may be a gender difference in GTN biotransformat ion.