Abstract
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.
Keywords
Anaesthetics - neurophysiologic monitoring - non-anaesthetic factors
