Effects of norepinephrine alone and norepinephrine plus dopamine on human intestinal mucosal perfusion

Objectives To evaluate the effect of norepinephrine alone and norepinephrine combined with dopamine on jejunal mucosal perfusion, gastric-arterial pCO₂ gradient, and global splanchnic oxygen demand-supply relationship after cardiac surgery.Design A prospective interventional study.Setting A university cardiothoracic intensive care unit.Patients Eighteen patients were studied during propofol sedation and mechanical ventilation after uncomplicated coronary artery bypass surgery.Interventions After control measurements, each patient received norepinephrine (50±26 ng·kg·min) to increase mean arterial blood pressure by 30% followed by addition of low-dose dopamine (2.6±0.3 µg·kg·min). Postdrug control measurements were performed 120 min after discontinuation of the catecholamines.Measurements and results Norepinephrine induced a 32% increase in systemic vascular resistance with no change in cardiac index. Neither jejunal mucosal perfusion, assessed by laser Doppler flowmetry, nor gastric-arterial pCO₂ gradient (tonometry) was affected by norepinephrine. Splanchnic O₂-extraction increased (P<0.05) and this increase was positively correlated to the individual dose of norepinephrine (r = 0.78, P<0.0001). Splanchnic lactate extraction was increased by norepinephrine (P<0.05). None of the patients had splanchnic lactate production during norepinephrine infusion. The addition of dopamine increased cardiac index by 27% (P<0.001) and decreased splanchnic O₂ extraction. Dopamine increased jejunal mucosal perfusion by 32% (P<0.001) while the gastric-arterial pCO₂ gradient remained unchanged.Conclusions Vasopressor therapy with norepinephrine after cardiac surgery did not jeopardize intestinal mucosal perfusion in spite of a dose-dependent increase of the global splanchnic oxygen demand-supply relationship. The addition of dopamine increased intestinal mucosal perfusion.This study was supported by grants from the Swedish Medical Research Council (no. 13156), Medical Faculty of Göteborg (LUA), Scandinavian Heart Center Research Foundations, and Göteborg Medical Society. The study was presented at the Annual Meeting of the European Association of Cardiothoracic Anaesthesiologists May 2002, Dublin, Ireland.