Brain protection during neurosurgery

Protecting the brain from ischemia during neurosurgery is one of the most important concerns for anesthesiologists. It is amazing that, to my knowledge, there is a paucity of prospective randomized controlled clinical trials comparing different treatments upon which to base cerebral protectant therapy. However, there is a wealth of laboratory research, both in vivo and in vitro, which supply the neuroanesthesiologist with theories that guide the management of patients at risk for cerebral ischemia. There are three major themes to this chapter. The first section reviews the research that led to the establishment of barbiturates as the gold standard for cerebral protection. The second discusses current methods of providing intraoperative cerebral protection. The third examines new and exciting possibilities regarding therapy/drugs that may become important tools in the future for cerebral protection. The past: the development of barbiturates as the gold standard for cerebral protection A brief examination of the historical sequence of barbiturate use for cerebral protection provides insight into not only the choice of this drug category but also the proposed mechanisms of ischemia. The classic theory of cerebral protection is based on the concept that by decreasing cerebral metabolic demand, the neuronal survival will improve during periods of inadequate cerebral blood flow (CBF). Because barbiturates decrease cerebral metabolism, it was the first drug group to be considered as a potential cerebral protectant. In the 1970s Michenfelder demonstrated that barbiturates decreased cerebral metabolic activity in a dose-dependent manner, which produced a progressive decrease in EEG activity, a reduction in the rate of ATP depletion, and protection 0889-8537/02/$ -see front matter D 2002, Elsevier Science (USA). All rights reserved. PII: S 0 8 8 9 -8 5 3 7 ( 0 1 ) 0 0 0 0 4 -

The cientificWorldJOURNAL Clinical Study Signal Persistence of Bispectral Index and State Entropy during Surgical Procedure under Sedation

Introduction. Bispectral index (BIS) and state entropy (SE) are prone to artifacts, especially due to electrocautery (EC). We compared the incidence of artifacts in BIS and SE during surgery under local anesthesia and sedation. Methods. 28 females undergoing breast surgery under local anesthesia and sedation were studied. Simultaneous BIS and SE measurements were recorded every 10 seconds. Artifact was defined as a failure of the device to display a numerical value while the electrodes remained appropriately attached to the patient's forehead. Ratio of artifact to good signal was compared between BIS and SE in the presence or absence of EC use. Results. 7679 data points were collected from 28 patients. Overall, artifact incidence was similar in BIS and SE (6.2% and 6.3%, resp.). In the presence of EC (1370 data points), BIS had significantly more artifact compared to SE (18.6% versus 6.4%, P < 0.0001). Without EC (6309 data points), BIS had significantly less artifact compared to SE (4.1% versus 7.3%, P < 0.0001). Discussion. BIS and SE were comparable for incidence of artifacts in patients under sedation. Use of EC lead to more artifact in BIS than SE. Conversely, BIS had fewer artifacts than SE when there was no EC use

Signal Persistence of Bispectral Index and State Entropy during Surgical Procedure under Sedation

Introduction. Bispectral index (BIS) and state entropy (SE) are prone to artifacts, especially due to electrocautery (EC). We compared the incidence of artifacts in BIS and SE during surgery under local anesthesia and sedation. Methods. 28 females undergoing breast surgery under local anesthesia and sedation were studied. Simultaneous BIS and SE measurements were recorded every 10 seconds. Artifact was defined as a failure of the device to display a numerical value while the electrodes remained appropriately attached to the patient’s forehead. Ratio of artifact to good signal was compared between BIS and SE in the presence or absence of EC use. Results. 7679 data points were collected from 28 patients. Overall, artifact incidence was similar in BIS and SE (6.2% and 6.3%, resp.). In the presence of EC (1370 data points), BIS had significantly more artifact compared to SE (18.6% versus 6.4%, <0.0001). Without EC (6309 data points), BIS had significantly less artifact compared to SE (4.1% versus 7.3%, <0.0001). Discussion. BIS and SE were comparable for incidence of artifacts in patients under sedation. Use of EC lead to more artifact in BIS than SE. Conversely, BIS had fewer artifacts than SE when there was no EC use