NIRS: So near yet so far (From the brain).

Cerebral oximetry is touted as a magic wand to detect cerebral hypoperfusion. Inability to completely exclude extracranial oxygen however is a limitation. Variation in scalp vascularity can magnify the limitations of relatively short emitter-detector distances. The combination of brain ischemia and cutaneous hyperemia, as is the situation during anaphylaxis and anaphylactoid reactions, can be associated with a paradoxical increase in cerebral oximetry values. This could compromise the quality and accuracy of care delivered. We report the association of red man syndrome with exaggerated cerebral oximetry values.