Cerebral Oximetric Monitoring of the Posterior Circulation

The INVOS Cerebral Oximeter utilizes two electrodes to monitor cerebral oxygenation. The recommended placement of these electrodes is on the forehead to monitor the frontal cortex. In this study, one electrode will be placed in the normal position on the forehead, and the other will be placed at the base of the skull. The stickers will be placed on the patient at the beginning of surgery and removed at the end. The maximum amount of time that they will be on the patient's skin is approximately six hours. Application of the stickers and the data they provide will not alter the provider's treatment plan. This procedure will be used for all enrolled patients, whether they are enrolled in Part I or Part II.