Open heart surgery; pump prime effects and cerebral arteriovenous differences in glucose, lactate and ketones

This study included 17 young children, who were operated with cardioplumona ry bypass for congenital heart defects and were cooled to 20 degrees C or 2 5 degrees C. No glucose, except for the pump prime solution, was administer ed during surgery. Samples of arterial blood, cerebral venous blood. from t he jugular bulb and mixed venous blood from the bypass circuit were obtaine d and analysed for concentrations of glucose, lactate and ketones as well a s oxygen saturation. The prime content of lactate significantly contributed to the arterial lactate concentrations, which together with the cerebral a rteriovenous (A-V) lactate differences remained elevated throughout the byp ass period. The prime content of glucose had less influence on the arterial concentrations and these did not increase until the rewarming period, when indications of gluconeogenesis from lactate were found. Arterial ketone co ncentrations also increased during rewarming in parallel with significant c erebral uptake of ketones. The lowest cerebral A-V glucose, lactate and oxy gen saturation differences were found at the target minimum temperature and this effect was significantly more pronounced in the patients cooled to 20 degrees C.