Effects of dobutamine and phenylephrine on cerebral perfusion in patients undergoing cerebral bypass surgery: a randomised crossover trial

Background: Patients undergoing cerebral bypass surgery are prone to cerebral hypoperfusion. Currently, arterial blood pressure is often increased with vasopressors to prevent cerebral ischaemia. However, this might cause vasoconstriction of the graft and cerebral vasculature and decrease perfusion. We hypothesised that cardiac output, rather than arterial blood pressure, is essential for adequate perfusion and aimed to determine whether dobutamine administration resulted in greater graft perfusion than phenylephrine administration. Methods: This randomised crossover study included 10 adult patients undergoing cerebral bypass surgery. Intraoperatively, patients randomly and sequentially received dobutamine to increase cardiac index or phenylephrine to increase mean arterial pressure (MAP). An increase of >10% in cardiac index or >10% in MAP was targeted, respectively. Before both interventions, a reference phase was implemented. The primary outcome was the absolute difference in graft flow between the reference and intervention phase. We compared the absolute flow difference between each intervention and constructed a random-effect linear regression model to explore treatment and carry-over effects. Results: Graft flow increased with a median of 4.1 (inter-quartile range [IQR], 1.7-12.0] ml min(-1)) after dobutamine administration and 3.6 [IQR, 1.3-7.8] ml min(-1) after phenylephrine administration (difference e0.6 ml min-1; 95% confidence interval [CI], -14.5 to 5.3; P=0.441). There was no treatment effect (0.9 ml min(-1); 95% CI, 0.0-20.1; P= 0.944) and no carry-over effect. Conclusions: Both dobutamine and phenylephrine increased graft flow during cerebral bypass surgery, without a preference for one method over the other.