Neuromonitoring and anesthesia in surgery of the spine

The authors report the main effects of anaesthetic drugs that are used alone or in association with anaesthetic protocols on somatosensory evoked potentials (SEP) and on motor evoked potentials (MEP). In the first part of the article, the effects are analysed on SEPs and MEPs that are obtained from non-invasive methods; in the second part, the effects of anaesthesia are analysed with respect to invasive methods of EP recordings. The current increase of invasive techniques of neuromonitoring by SEPs and MEPs is in relation with the weak effect of anaesthetics on evoked responses. Total intravenous anaesthesia (TIVA) provides stable anaesthesia for non-invasive SEP neuromonitoring only if bolus is avoided. With TIVA and other anaesthetic techniques, the introduction of repetitive stimulation provides new possibilities for non-invasive MEP neuromonitoring.