Phenylephrine,treating hypotension and injure Brain

The importance of arterial pressure management in patients undergoing anesthesia has been substantiated by the significant relationship between intraoperative hypotension and postoperative neurocognitive impairment.

Despite the fact that arterial pressure monitoring is a standard practice, consensus in terms of when and how to treat intraoperative hypotension is still lacking. Among all options, phenylephrine and ephedrine belong to the set of typical sympathomimetic agents routinely chosen to increase arterial pressure.

However, little is known about the impacts of these agents on cerebral oxygenation and the relationship between global and regional haemodynamics. If treating hypotension is an attempt to avoid organ ischaemia and hypoxia, we are actually achieving the opposite result (decreased cerebral oxygenation) by administering phenylephrine, as demonstrated in study( published in BJA November Issue) using a quantitative NIRS device and in previous studies using a trend NIRS device.

Another study also demonstrated the negative impact of norepinephrine infusion on cerebral oxygenation. Thus, the routine and indiscriminate use of vasopressors might be less beneficial than previously thought.

Nissen P, Brassard P, Jørgensen TB, et al. Phenylephrine but not ephedrine reduces frontal lobe oxygenation following anesthesia-induced hypotension. Neurocrit Care 2010;12:17–23.
Brassard P, Seifert T, Wissenberg M, et al. Phenylephrine decreases frontal lobe oxygenation at rest but not during moderately intense exercise. J Appl Physiol 2010;108:1472–8.

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