Intraoperative neurophysiological monitoring by anesthesiologists.

N intraoperative neurophysiological monitoring (IONM) is routinely carried out during various surgeries on spinal cord, vertebral column, and aortic/cerebral aneurysms. Critical neurological structures may easily be damaged by operative manipulations during these procedures. The aim of such monitoring is to identify changes in neuronal function prior to irreversible damage. The technology used is relatively sophisticated and requires neurophysiologists to interpret the signals and convey it to the operative team. However, the evoked potentials are rather simple in concept with regard to their clinical application for diagnostic testing and intra-operative monitoring.1 Evoked potential monitoring includes somatosensory evoked potentials (SSEP), brainstem auditory evoked potentials (BAEP), motor evoked potentials (MEP), and visual evoked potentials (VEP). SSEPs reflect conduction in dorsal columns whereas transcranial MEPs represent anterior horn motor neuron function. Electrophysiological monitoring in the operative milieu may pose several specific challenges. These include 1) presence of electromagnetic interference from use of various equipments in the operating room (OR); and 2) use of anesthetic agents that can alter recordings. Anesthetics exert their effects on the brain by depressing cerebral metabolism which may result in alteration of signals of evoked potentials in the form of decreased amplitude and increased latency. In the article published on this issue of Minerva Anestesiologica, Fudickar et al.2 highlighted on electrophysiologic neuromonitoring during repair of thoracoabdominal aorta by anesthesiologists. This article brings out two relevant points to the forefront. Important one being the fact that neurophysiological monitoring is essential to prevent spinal cord ischemia resulting in paraparesis or paraplegia.3 Twenty consecutive patients undergoing thoracic/thoracoabdominal aortic aneurysm repair were monitored successfully with SSEP and MEP during the cardiopulmonary bypass (CPB) phase by certified anesthesiologists. One patient who was not monitored with MEP developed postoperative paraplegia. The result was consistent with the results of a survey on practice of evoked potential monitoring by Legatt.4 Timely corrective action by the surgical team in reperfusing the spinal cord, when alerted to by the anesthesiologist monitoring the combined SSEP and MEP signals, prevented any long-term damage potential to these patients. Secondly, the anesthesiologist has taken over the role of neurophysiologists who are traditionally involved with such monitoring, in the OR apart from carrying out the primary role. This becomes a necessity where neurophysiologists are not available either due to a resource crunch or lack of adequate number of neurophsyiologists. The need to train anesthesiologists for interpretation of electrophysiologic neuromonitoring methods has been carried out by the German Society of Anaesthesiology and Intensive Medicine (DGAI) proIntraoperative neurophysiological monitoring by anesthesiologists