Jejunal luminal microdialysate lactate in cardiac tamponade--effect of low systemic blood flow on gut mucosa.

Abstract

To assess gut mucosal metabolic response and susceptibility to dysoxia during low systemic blood flow induced by cardiac tamponade. A randomized, controlled animal experiment. National laboratory animal center. Cardiac tamponade was induced in six pigs, while six additional pigs served as controls. In the tamponade group, fluid was injected into the pericardial space to reduce aortic flow, aiming first at a flow of 50 ml/kg per min and then at 30 ml/kg per min. Each step lasted for 60 min. We measured luminal lactate by microdialysis and mucosal PCO(2) by tonometry in the mid-jejunum. Aortic and superior mesenteric artery blood flow, arterial and mesenteric venous lactate, pyruvate and ketone bodies and regional lactate exchange were measured. The distribution of aortic blood flow to superior mesenteric artery remained unchanged (baseline 14 (12-16)%; median (interquartile range), stepwise flow reduction 11 (10-17)% and 13 (12-19)%, NS) during reduction of aortic blood flow from 81 (61-95) ml/kg per min to 49 (47-49) ml/kg per min and 23 (21-27) ml/kg per min. Systemic hyperlactatemia developed early, whereas gut luminal lactate increased only after 60 min of hypoperfusion and could be largely explained by arterial hyperlactatemia. Mesenteric venous lactate-to-pyruvate (L/P) ratio increased after 30 min of tamponade, but both venous-arterial lactate and pyruvate gradients turned negative (gut lactate and pyruvate uptake). Mesenteric venous ss-hydroxybutyrate to acetoacetate ratio increased after 60 min. No changes were observed in the controls. Jejunal mucosal dysoxia and anaerobic metabolism occurs late during low systemic blood flow induced by experimental cardiac tamponade.