To the Editor:—
Talke et al. 1recently reported that sevoflurane increases lumbar cerebrospinal fluid pressure (LCSFP) in normocapnic patients undergoing transsphenoidal hypophysectomy. The authors should be congratulated for simply reporting their observations without speculating on the cause of the increase in LCSFP. The authors correctly pointed out that this increase in LCSFP is significant but clinically irrelevant and observed that the increase in LCSFP is at variance to previously reported results from our group. 2They also pointed out that our baseline results were obtained during 70% nitrous oxide; therefore, the lack of increase in intracranial pressure with sevoflurane that we observed could be reinterpreted as sevoflurane having the same effect as 70% nitrous oxide. We would like to point out that there are two other interpretations that the authors might have missed: (1) In our study, the intracranial pressure is measured using an intraparenchymal fiberoptic catheter. This is generally considered to be more accurate than LCSFP. Although changes in the latter are valid, factors other than cerebral physiology may be involved. (2) The authors measured baseline LCSFP values during propofol–nitrous oxide anesthesia. Because propofol is a cerebral vasoconstricting agent, whereas sevoflurane is not, a more appropriate interpretation of the authors’ data is that LCSFP is higher during sevoflurane anesthesia compared with propofol–nitrous oxide anesthesia.
As published, the title of the article is misleading because it implies that sevoflurane anesthesia increases LCSFP compared with unanesthetized patients. With all studies, the choice of the control group is critically important and affects the interpretation of the observations.