To the Editor:
We read with great interest the study by Koch et al.,1 which concluded that “ephedrine results in better brain microcirculation and oxygen delivery than phenylephrine” and raised “concerns regarding phenylephrine for blood pressure augmentation in patients with cerebral pathology.” The results of this prospective, randomized trial are similar to those of a network meta-analysis2 of 399 patients from nine randomized trials comparing various inotropes/vasopressors used to treat intraoperative hypotension in patients mostly without cerebral pathology. That analysis found that dopamine, ephedrine, and norepinephrine had the lowest probability of adversely affecting cerebral oxygen saturation as measured by cerebral oximetry and that phenylephrine, compared with the other inotropes/vasopressors, decreased cerebral oxygen saturation. Koch et al.’s findings on the deterioration of microcirculation after phenylephrine administration on the side of the brain not affected by brain pathology highlight the importance of considering the cerebrovascular effect of vasopressors in every patient, not only the ones with cerebral pathologies. Phenylephrine is very effective in restoring systemic blood pressure to normal values. Clinicians tend to favor what has been described by Thiele et al.3 as the “tangible bias,” which is our tendency to fix what we can see and understand, that is, systemic blood pressure, over what we cannot: macro- and microscopic cerebral perfusion. Koch et al.’s results should prompt clinicians to choose the appropriate vasopressor to maintain optimal cerebral microcirculation.