Anaesthetic considerations for evoked potentials monitoring

• Main Author: Parmod Kumar Bithal
• Format: Article
• Language: English
• Published: Thieme Medical and Scientific Publishers Pvt. Ltd. 2014-04-01
• Series: Journal of Neuroanaesthesiology and Critical Care
• Subjects: anaesthetics; neurophysiologic monitoring; non-anaesthetic factors
• Online Access: http://www.thieme-connect.de/DOI/DOI?10.4103/2348-0548.124832
• ISSN: 2348-0548; 2348-926X

Intra-operative neurophysiologic monitoring (IONM) under anaesthesia has achieved popularity because it helps prevent/ minimize neurologic morbidity from surgical manipulations of various neurologic structures. Neurologic functions in an anaesthetised patient can be monitored either by electroencephalography (EEG) or by evoked potentials. Whereas, EEG is difficult to analyse, evoked potentials, in contrast, are easy to interpret, they are either present or absent, delayed or not delayed, with normal or abnormal wave. The goal of IONM is to identify changes in nervous system function prior to irreversible damage. Many factors need consideration when selecting an anaesthetic regimen for intra-operative monitoring of evoked potentials. The very pathophysiological condition or the potential risks of the contemplated surgical procedure, which require evoked potentials monitoring, may place constraints on anaesthetic management as well. With the availability of numerous anaesthetic techniques, an appropriate plan for managing both anaesthesia and IONM in a patient should be organised. It is extremely essential not to alter the pharmacological state of the patient to avoid any changes in the recording of evoked responses. While an anaesthesiologist may alter plans for a patient in order to facilitate IONM, monitoring team too, sometimes may be required to modify plans for monitoring when a particular anaesthetic agent or technique is strongly indicated or contraindicated. At times, compromise may be required between an anaesthesia technique and a monitoring technique. To serve patients’ best interest, it is critical to have a team approach and good communication among the neurophysiologist, anaesthesiologist and surgeon.