Pilot alternating treatment design study of the splanchnic metabolic effects of two mean arterial pressure targets during cardiopulmonary bypass

Background. The arterial pressure target for optimal splanchnic function during cardiopulmonary bypass (CPB) is uncertain. Thus, we aimed to compare the effects of two different arterial pressure targets during CPB on trans-splanchnic oxygenation, acid-base regulation, and splanchnic interleukin-6 (IL-6) and interleukin-10 (IL-10) flux. Methods. Sixteen patients undergoing cardiac surgery with CPB in a university affiliated hospital were subjected to a prospective alternating treatment design interventional study. We measured arterial and hepatic vein blood gases, electrolytes, IL-6, and IL-10 while targeting a mean arterial pressure (MAP) of between 60 and 65 mm Hg for 30 min, a MAP of between 80 and 85 mm Hg for 30 min (using norepinephrine infusion), and finally 60-65 mm Hg MAP target for 30 min. Results. The MAP targets were achieved in all patients [65 (4), 84 (4), and 64 (3) mm Hg, respectively; P<0.001] with a greater dose of norepinephrine infusion during the higher MAP target (P<0.001). With longer time on CPB, hepatic vein O-2 saturation decreased, while magnesium, lactate, glucose, IL-6, and IL-10 increased independent of MAP target. The decrease in hepatic vein saturation was greater as the temperature increased (re-warming). Overall, there was trans-splanchnic oxygen, chloride, lactate, and IL-6 removal during CPB (P<0.001) and carbon dioxide, bicarbonate, glucose, and IL-10 release (P<0.001). Such removal or release was not affected by the MAP target. Conclusions. Targeting of a higher MAP during CPB by means of norepinephrine infusion did not affect splanchnic oxygenation, splanchnic acid-base regulation, or splanchnic IL-6 or IL-10 fluxes. Australian and New Zealand Clinical Trial Registry. ACTRN 12611001107910.