Renal effects of norepinephrine-induced variations in mean arterial pressure after liver transplantation: A randomized cross-over trial.

Abstract

Acute kidney injury is commonly seen after liver transplantation. The optimal perioperative target mean arterial pressure (MAP) for renal filtration, perfusion and oxygenation in liver recipients is not known. The effects of norepinephrine-induced changes in MAP on renal blood flow (RBF), oxygen delivery (RDO2 ), glomerular filtration rate (GFR) and renal oxygenation (=renal oxygen extraction, RO2 Ex) were therefore studied early after liver transplantation. Ten patients with an intra- and post-operative vasopressor-dependent systemic vasodilation were studied early after liver transplantation during sedation and mechanical ventilation. To achieve target MAP levels of 60, 75 and 90mmHg, the norepinephrine infusion rate was randomly and sequentially titrated. At each target MAP, data on cardiac index (CI), RBF and GFR were obtained by transpulmonary thermodilution (PiCCO), the renal vein thermodilution technique and renal extraction of chromium ethylenediaminetetraaceticacid (51 Cr-EDTA), respectively. Renal oxygen consumption (RVO2 ) and extraction (RO2 Ex) were calculated according to standard formulas. At a target MAP of 75mmHg, CI (13%), RBF (18%), RDO2 (24%), GFR (31%) and RVO2 (20%) were higher while RO2 Ex was unchanged compared to a target MAP of 60mmHg. Increasing MAP from 75 up to 90mmHg increased RVR by 38% but had no further effects on CI, RBF, RDO2 or GFR. In patients undergoing liver transplantation, RBF and GFR are pressure-dependent at MAP levels below 75mmHg. Our results suggest that MAP should probably be targeted to approximately 75mmHg for optimal perioperative renal filtration, perfusion and oxygenation in patients undergoing liver transplantation.