Neurosurgery for the treatment of epilepsy.

PURPOSE OF REVIEW: Epilepsy is a common condition that is estimated to afflict 0.5-1.0% of the world's population. Frequently commencing in childhood, it is often associated with life-long disability. Approximately one-third of patients with epilepsy are refractory to antiepileptic drug therapy and many of these patients are candidates for surgical treatment. A growing body of evidence supports the safety and efficacy of surgery for the treatment of selected patients with epilepsy. Little information is available in the anesthesia literature regarding the presurgical assessment of candidates for surgical treatment. RECENT FINDINGS: The presurgical identification of suitable candidates involves a multidisciplinary approach to assessment. Recent advances, particularly in neuroimaging techniques, are dramatically enhancing the capacity to accurately identify patients who are most likely to benefit from surgery. Epilepsy surgery is underused worldwide and in developed countries. In view of current efforts to increase opportunities to provide surgical treatment to more patients and to offer surgery earlier in the course of the disorder, the number of patients requiring specialized perioperative anesthetic care is expected to increase. SUMMARY: This article provides anesthesiologists with an overview of the assessment process, investigation techniques and current rationale that influence the selection of appropriate candidates for surgical treatment and the associated need for specialized anesthetic care.

Cerebrovascular disease.

PURPOSE OF REVIEW: Carotid endarterectomy remains the preferred surgical intervention for the prevention of stroke among patients with extracranial cerebrovascular disease. Subgroup analyses of the results of several multicentre trials have contributed substantially to our understanding of the appropriate selection of patients and the perioperative risk associated with this procedure. RECENT FINDINGS: This review describes recent advances in our understanding of the appropriate use of carotid endarterectomy, and outlines recent developments and strategies that are likely to influence the perioperative care of these patients. SUMMARY: As current clinical guidelines for the use of carotid endarterectomy unfold, anaesthesiologists can expect to care more frequently for older patients and those at increased risk of complications. The perioperative management of co-existing diseases, particularly the control of hypertension and the strategies aimed at reducing the risk of cardiac complications, will contribute substantially to reducing perioperative morbidity and mortality.

Sedative doses of remifentanil have minimal effect on ECoG spike activity during awake epilepsy surgery.

The use of remifentanil for sedation during awake epilepsy surgery has been described in a case report. However, little information is available regarding the effect of remifentanil on the quality of intraoperative electrocorticography (ECoG). This study was designed to investigate the effect of sedative doses of remifentanil on ECoG interictal spike activity among patients undergoing awake anterior temporal lobectomy for refractory epilepsy. Ten adult patients were studied prospectively. After baseline EcoG recordings were obtained, remifentanil was administered as a continuous infusion at 0.1 microg/kg/min and the ECoG recorded continuously for 15 minutes. Recordings obtained before and during the administration of remifentanil were compared with respect to spike frequency and location. A trend toward a small decrease in spike frequency was observed as patients became increasingly somnolescent and background ECoG activity slowed. The difference was not statistically significant. Blood pressure and heart rate were not adversely affected by the administration of remifentanil. Respiratory rates decreased in all patients (mean decrease, 8 breaths/min) and one patient transiently developed a respiratory rate of 4 breaths per minute that elicited a decrease in the rate of remifentanil administration. Remifentanil administered at sedation doses does not adversely affect intraoperatively recorded interictal spike activity. Further investigation of the use of this drug during awake epilepsy surgery is warranted.

The septohippocampal system participates in general anesthesia.

How the brain mediates general anesthesia is not known. We report that two interconnected structures in the forebrain, the medial septum and the hippocampus, participate in maintaining awareness and movements during general anesthesia. In the awake, freely behaving rat, inactivation of the medial septum or the hippocampus by local injection of a GABA(A) receptor agonist, muscimol, decreased the dose of a general anesthetic needed to induce a loss of the tail-pinch response or a loss of righting reflex. Septohippocampal inactivation also suppressed the behavioral hyperactivity or the delirium stage associated with general anesthesia. An increase and decrease of 30-50 Hz (gamma) waves in the hippocampus correlated with an increase and decrease in behavioral activity, respectively. Similar results were found for both volatile (halothane and isoflurane) and nonvolatile (propofol and pentobarbital) anesthetics. We conclude that the behavioral hyperactivity induced by a general anesthetic is mediated in part by the septohippocampal system, and that depression of the septohippocampal system increases the potency of a general anesthetic. It is suggested that more potent general anesthetics or adjuvants may be developed by maximizing the pharmacological depression of the septohippocampal system.