Intraoperative neurophysiologic monitoring and anaesthetic implications

Diagnostic Accuracy of Somatosensory Evoked Potential and Transcranial Motor Evoked Potential in Detection of Neurological Injury in Intradural Extramedullary Spinal Cord Tumor Surgeries: A Short-Term Follow-Up Prospective Interventional Study Experience from Tertiary Care Center of India

Objective  Intraoperative neuromonitoring (IONM) is an acknowledged tool for real-time neuraxis assessment during surgery. Somatosensory evoked potential (SSEP) and transcranial motor evoked potential (MEP) are commonest deployed modalities of IONM. Role of SSEP and MEP in intradural extramedullary spinal cord tumor (IDEMSCT) surgery is not well established. The aim of this study was to evaluate sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of SSEP and transcranial MEP, in detection of intraoperative neurological injury in IDEMSCT patients as well as their postoperative limb-specific neurological improvement assessment at fixed intervals till 30 days. Materials and Methods  Symptomatic patients with IDEMSCTs were selected according to the inclusion criteria of study protocol. On modified McCormick (mMC) scale, their sensory-motor deficit was assessed both preoperatively and postoperatively. Surgery was done under SSEP and MEP (transcranial) monitoring using appropriate anesthetic agents. Gross total/subtotal resection of tumor was achieved as per IONM warning alarms. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of SSEP and MEP were calculated considering postoperative neurological changes as "reference standard." Patients were followed up at postoperative day (POD) 0, 1, 7, and 30 for convalescence. Statistical Analysis  With appropriate tests of significance, statistical analysis was carried out. Receiver-operating characteristic curve was used to find cutoff point of mMC for SSEP being recordable in patients with higher neurological deficit along with calculation of sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of SSEP and MEP for prediction of intraoperative neurological injury. Results  Study included 32 patients. Baseline mean mMC value was 2.59. Under neuromonitoring, gross total resection of IDEMSCT was achieved in 87.5% patients. SSEP was recordable in subset of patients with mMC value less than or equal to 2 with diagnostic accuracy of 100%. MEP was recordable in all patients and it had 96.88% diagnostic accuracy. Statistically significant neurological improvement was noted at POD-7 and POD-30 follow-up. Conclusion  SSEP and MEP individually carry high diagnostic accuracy in detection of intraoperative neurological injuries in patients undergoing IDEMSCT surgery. MEP continues to monitor the neuraxis, even in those subsets of patients where SSEP fails to record.

The effect of dexmedetomidine on wake-up test quality when muscle relaxants are not used: A randomized control trial

Background and Aims

Stagnara wake-up test is a simple reproducible neuromonitoring method during spinal surgery which replaces the evoked potential monitoring in the absence of neuromonitoring facilities. Dexmedetomidine (DEX) effect on the intraoperative wake-up test is still unclear. The present study was conducted to evaluate the effectiveness of DEX on the quality of wake-up test during spinal correction surgery.

Methods

A randomized controlled study was carried out over 62 patients randomized into two equal groups planned for elective minimally invasive corrective spine surgery. Instead of atracurium administration in the control group, patients in the experimental group were administered titrated continuous intravenous infusion of DEX at a dose of 0.2-0.7 μg/kg/hour. Lidocaine 2% spray around the vocal cords was done in both the groups to facilitate toleration of the endotracheal tube.

Results

The DEX group showed statistically significant longer duration and better quality of the wake-up test. Statistically significant better haemodynamic state, a lower amount of intraoperative sedatives and higher amount of intraoperative analgesics were also evident in the DEX group. The postoperative Ramsay sedation scale was significantly lower in the DEX group just after extubation.

Conclusion

The DEX use has shown an improving effect on the wake-up test quality, with slightly prolonged wake-up time. The present work supports the use of DEX as an adjuvant drug alleviating the need for the neuromuscular blockade, inducing a better haemodynamic profile, exhibiting better sedation and improving the awakening condition.

Implementation and adherence to a speciality-specific checklist for neurosurgery and its influence on patient safety

Background and Aims

Neurosurgery involves a high level of expertise coupled with enduring and long duration of working hours. There is a paucity of published literature about the experience with a speciality-specific checklist in neurosurgery. We conducted a cross-sectional observational study to identify the adherence to various elements of the Modified World Health Organization Surgical Safety Checklist (WHO SSC) for neurosurgery by the operating room (OR) team.

Methods

We implemented an intra-operative Modified WHO SSC consisting of 40 tools for neurosurgery, in 200 consecutive elective cases. Trained anaesthesiologists assumed the role of checklist co-ordinator. The checklist divided the surgery into 5 phases, each corresponding to a specific time-period. The adherence rates to various tools were evaluated and areas where the checklist prompted a corrective measure were analysed.

Results

A total of 131 cases undergoing craniotomy and 69 cases undergoing spine surgery were studied. With the 40-point modified SSC applied in 200 cases, we analysed a total of 8000 observations. The modified checklist prompted the OR team to adhere to speciality-specific safety practices about application of compression stockings (9.5%); airway precautions in unstable cervical spine (2.5%); precautions for treatment of raised intracranial pressure (10.5%); and intraoperative neuro-monitoring (5%).

Conclusion

The implementation of Modified WHO SSC for Neurosurgery, by a designated checklist co-ordinator, can rectify anaesthetic and surgical facets promptly, without increasing the OR time. The anaesthesiologist as SSC coordinator can effectively implement an intraoperative checklist ensuring excellent participation of operating room team members.