In Reply:—
Thank you for your interest in our study on intracranial pressure and cerebral hemodynamic in patients with cerebral tumors. We performed an analysis of the relationship between mean arterial blood pressure and intracranial pressure (ICP) both before and during hyperventilation but found no significant correlation. The correlation coefficients, however, was negative in the propofol/fentanyl group but positive in the isoflurane/fentanyl and sevoflurane/fentanyl groups. These differences might be caused by difference in autoregulatory capacity between propofol/fentanyl and the other two groups, suggesting that cerebral autoregulation was better preserved in the propofol/fentanyl group compared with isoflurane/fentanyl and sevoflurane/fentanyl anesthetized patients, but this does not explain that ICP was significantly lower during propofol/fentanyl anesthesia. On the contrary, one would expect a low ICP in the isoflurane and sevoflurane groups, because the mean arterial blood pressures were significant lower. We also analyzed the correlation coefficients for the relationship between cerebral perfusion pressure and ICP. In all groups, the correlation coefficients were negative but insignificant. The negative correlations were not surprising, considering that cerebral perfusion pressure was calculated as the difference between mean arterial blood pressure and ICP. Because cerebral perfusion pressure and ICP are not independent variables, we did not include these data in the results.
