What has happened to evidence-based medicine?

To the Editor:—We read with great interest the article by Petersen et al., which demonstrated the expected clinical response to the three anesthetic agents studied. An increase in arterial pressure may result in an increase in the cerebral perfusion pressure and reduce reflex cerebral vasodilatation, potentially resulting in reduced intracranial pressure. We note that the mean arterial pressures in the propofol group were substantially higher than in the two inhalation groups, both before and after hyperventilation. The propofol group was shown to have both a lower measured intracranial pressure and subjective surgical estimation of brain swelling at craniotomy. The influence of the potentially higher perfusion pressure on these findings in this group cannot be estimated from the study. Was this relationship between mean arterial pressure and intracranial pressure examined by the authors, and if so, could they comment on its possible significance? Robert A. Fry, M.B., Ch.B.* Nigel N. Robertson, M.B., Ch.B. *Auckland Hospital, Auckland New Zealand. [email protected]