Complex effects of continuous vasopressor infusion on fluid responsiveness during liver resection: A randomised controlled trial.

Background: Fluid responsiveness is an important factor to consider for fluid volume loading during major surgery. The effect of continuous vasopressor infusion on fluid responsiveness during prolonged major surgery is a concern.

Objective: We hypothesised that continuous vasopressor infusion during major surgery might not exert significant effects on changes in stroke volume variation (SVV) following fluid bolus infusion, and thereby on fluid responsiveness.

Design: Randomised controlled trial.

Setting: University hospital from April 2014 to August 2016.

Patients: Patients undergoing liver resection who were randomised to receive continuous intravenous infusion of phenylephrine (P group), norepinephrine (N group), or no vasopressor (C group) (n=17/group). Exclusion criteria were cardiac arrhythmia and severe cardiac, pulmonary or renal dysfunction.

Intervention: Patients received 4 ml kg fluid boluses of 6% hydroxyethyl starch solution when SVV was at least 12%. Vasopressors were administered continuously to maintain the systemic vascular resistance index at more than 1900 dyn s cm m.

Main Outcome Measures: Cardiac index and SVV were measured using the FloTrac/Vigileo system (Version 4.00). The number of fluid boluses with fluid responsiveness (i.e. >15% increase in cardiac index) was compared between groups using multilevel logistic regression analysis.

Results: Numbers of fluid responsive boluses in the C, P and N groups were 12 (14%), 22 (34%) and 19 (27%), respectively. Odds ratios on fluid responsiveness for phenylephrine and norepinephrine compared with the control were 3.65 (97.5% confidence interval, 1.15 to 11.6; P = 0.012) and 2.56 (97.5% confidence interval, 0.82 to 8.00; P = 0.064), respectively. Decreases in SVV after fluid bolus infusion for the P and N groups were comparable with the C group (P = 0.23 and 0.53, respectively).

Conclusion: Continuous administration of phenylephrine increased fluid responsiveness during liver resection, suggesting complex effects of continuous vasopressor infusion involving changes in cardiac preload and afterload.

Trial Registration: UMIN000011024.