Supratentorial Neurosurgery Research Articles

Spectral entropy assessment with auditory evoked potential in neuroanesthesia

Objective The assessment of the level of anesthesia is a very hard task, since no gold standard has stood out in the past three decades. Middle Latency Auditory Evoked Potential (MLAEP) is one of the most popular neurophysiological tools for anesthesia monitoring. Recently, Spectral Entropy (SpEn) has been introduced: it provides two different parameters, State Entropy (SE) and Response Entropy (RE). The aim of this prospective study is to check SpEn end-point, comparing it to MLAEPs in neurosurgical anesthesia. Methods Twenty patients submitted to elective supratentorial neurosurgery for removal of a temporal–parietal meningioma were included in the study. SpEn and MLAEPs were simultaneously monitored using the M-entropy module S/5™ ( GE Health Care, Helsinki, Finland) and Alaris Medical System AEP-ARX index monitor™ (AAI) (Kidemosevej, Denmark), respectively. Results Four thousand and sixty four data points of SE, RE and AAI were recorded and ROC curves comparing AAI to RE and SE showed a highly significant ( p < 0.0001) area under the curve. The RE and SE cut-off values (showing maximal sensitivity with maximal specificity) to discriminate anesthesia from awake or consciousness sedation were 61 and 58, respectively. However, in a group of data points, low AAI was associated to high SpEn (577 data points for RE and 770 for SE) and vice versa (31 data points for RE and 43 for SE). The prediction probability for SE was 0.977 and for RE was 0.968. Conclusions Our results suggest that SpEn is as effective as AAI. Significance Our results show that SpEn is able to discriminate between the levels of wakefulness and surgical anesthesia. However, the meaning of data showing a discrepancy between AAI and SpEn is not yet clear and calls for further study.

Bispectral Index and Spectral Entropy in Neuroanesthesia

Spectral Entropy (SpEn) is an alternative tool to the bispectral index (BIS) for monitoring depth of hypnosis. SpEn measures response entropy (RE) and state entropy (SE). This open-label prospective study was designed to evaluate SpEn and BIS in 20 patients undergoing elective supratentorial neurosurgery with craniotomy and resection of brain tumors. SpEn and BIS were obtained continuously by Datex Ohmeda M-entropy module S/5 (Helsinki, Finland) and Aspect Medical System BIS (Newton), respectively. Total intravenous anesthesia was performed in all patients by Fresenius Vial infusion system (Brezins, France) to maintain a plasma concentration of propofol of 2.5 to 5 microg mL(-1) and sufentanil of 0.2 to 0.4 etag mL(-1). SpEn, BIS, the estimated propofol effect-site concentrations (Ce), the mean arterial pressure (MAP), and the heart rate (HR) were recorded during 12 specific events: induction of anesthesia, patient stop counting, loss of blinking reflex, intubation, mayfield pinning, craniotomy, termination of propofol infusion, recovery of blinking reflex, coughing, limb movement, order execution, and extubation. Stated that prediction probability or P(K) represents an indicator probability to predict correctly the rank order of an arbitrary pair of distinct observed indices of depth of hypnosis (ie, clinical settings and SpEn indices, or BIS, Ce, MAP, HR), PK of BIS, SE, RE, and Ce provided a better depth of hypnosis than MAP and HR; RE being the best for rapidity, SE for sensitivity, and BIS for specificity. There is good correlation between the 3 hypnosis indices and Ce. This study demonstrates that SpEn provides a reproducible hypnosis index for patients undergoing supratentorial neurosurgical procedures.

Cerebellar haemorrhage after non-traumatic evacuation of supratentorial chronic subdural haematoma: report of two cases

Cerebellar haemorrhage is an unusual complication of supratentorial neurosurgery. Several causative pre-operative factors and medical risk factors may predispose patients to cerebellar haemorrhage, however its etiology remains still unclear. Only two case reports have previously described the occurrence of cerebellar haemorrhage after subdural haematoma evacuation by burr-hole trepanation. We present two patients with this rare postoperative complication of minor supratentorial neurosurgery and possible underlying pathophysiological mechanisms are discussed. Our two cases support the post- rather than per-operative pathogenetic hypothesis. Although the complication is associated with a significant morbidity and mortality, most cases follow a benign course.

Postoperative Pain Management After Supratentorial Craniotomy

The aim of this study was to compare the analgesic efficacy of three different postoperative treatments after supratentorial craniotomy. Sixty-four patients were allocated prospectively and randomly into three groups: paracetamol (the P group, n = 8), paracetamol and tramadol (the PT group, n = 29), and paracetamol and nalbuphine (the PN group, n = 27). General anesthesia was standardized with propofol and remifentanil using atracurium as the muscle relaxant. One hour before the end of surgery, all patients received 30 mg/kg propacetamol intravenously then 30 mg/kg every 6 hours. Patients in the PT group received 1.5 mg/kg tramadol 1 hour before the end of surgery. For patients in the PN group, 0.15 mg/kg nalbuphine was injected after discontinuation of remifentanil, because of its mu-antagonist effect. Postoperative pain was assessed in the fully awake patient after extubation (hour 0) and at 1, 2, 4, 8, and 24 hours using a visual analog scale (VAS). Additional tramadol (1.5 mg/kg) or 0.15 mg/kg nalbuphine was administered when the VAS score was > or = 30 mm. Analgesia was compared using the Mantha and Kaplan-Meier methods. Adverse effects of the drugs were also measured. The three groups were similar with respect to the total dose of remifentanil received (0.27 +/- 0.1 mircog/kg/min). In all patients, extubation was obtained within 6 +/- 3 minutes after remifentanil administration. Postoperative analgesia was ineffective in the P group; therefore, inclusions in this group were stopped after the eighth patient. Postoperative analgesia was effective in the two remaining groups because VAS scores were similar, except at hour 1, when nalbuphine was more effective (P = .001). Nevertheless, acquiring such a result demanded significantly more tramadol than nalbuphine (P < .05). More cases of nausea and vomiting were observed in the PT group but the difference was not significant (P < .06). In conclusion, pain after supratentorial neurosurgery must be taken into account, and paracetamol alone is insufficient in bringing relief to the patient. Addition of either tramadol or nalbuphine to paracetamol seems necessary to achieve adequate analgesia, with, nevertheless, a larger dose of tramadol to fulfill this objective.

General anaesthesia for supratentorial neurosurgery.

Anaesthesia for the surgical treatment of supratentorial tumours requires an understanding of: the pathophysiology of a localised or generalised increase in intracranial pressure (ICP), the regulation and maintenance of intracerebral perfusion, avoidance of secondary systemic insults to the brain, and the effects of anaesthetic drugs on ICP, cerebral perfusion and cerebral metabolism. Knowledge of the therapeutic options available for decreasing ICP, brain bulk and brain tension perioperatively is also essential. Potential complications which may present during supratentorial neurosurgery include massive intraoperative haemorrhage and seizures. The fact that the surgeon is operating on a tensed brain is also a potential source of difficulty. The need to monitor brain function and environment during surgery poses a challenge to the anaesthesiologist, as does the achievement of rapid emergence from anaesthesia with the adequate use of anaesthetic drugs.

Epilepsy after Craniotomy and the Place of Prophylactic Anticonvulsant Drugs: Discussion Paper

A retrospective study of 1000 patients who had undergone supratentorial neurosurgery and with prolonged follow-up revealed an overall postoperative incidence of epilepsy of 17%. The incidence varied with different pathologies but anticonvulsants given prophylactically in a randomized trial did not significantly alter the incidence. Routine anticonvulsant prophylaxis cannot be recommended.