Vasopressor Effects on Cerebral Microcirculation: Reply

We thank Bombardieri and Tsui¹  for their excellent comments and interest in our study.²  We agree with Bombardieri and Tsui that the deterioration of microperfusion and possibly tissue oxygenation after phenylephrine administration in the “healthy” brain hemisphere²  indicates that different vasopressors may also have a different influence on microperfusion and tissue oxygenation in the healthy anesthetized brain and should be further explored.³  In our opinion, future studies on the effects of different vasopressors on the cerebral macro- and microcirculation should be considered in the context of their different effects on the systemic circulation to provide a fully integrated picture of their influence on organ perfusion and oxygenation.⁴  Due to current difficulties in monitoring brain microcirculation and cerebral tissue oxygenation, we tend to rely on systemic parameters such as heart rate and blood pressure when treating patients with inotropes/vasopressors. However, a recent publication suggests that brain tissue oxygen saturation, as measured by near-infrared spectroscopy, may reflect cerebral metabolic supply–demand balance during vasopressor therapy.⁴  Although the use of near-infrared spectroscopy is associated with limitations, such as extracranial signal contamination, it may currently be the only way to provide a continuous indicium of brain microperfusion and tissue oxygenation.

Dr. Rasmussen declares a financial relationship with the Health Research Foundation of the Central Denmark Region (Aarhus, Denmark). Dr. Koch declares no competing interests.