Propofol-Fentanyl-Dexmedetomidine and Propofol-Fentanyl-Sevoflurane Anesthesia for Major Spine Surgery Under Somato Sensory- and Motor- Evoked Potential Monitoring

A catastrophic complication of spinal surgery is nerve and spinal cord injury. The incidence of neurological defects after spinal surgery can be reduced from 3.7%-6.9% to less than 1% with proper electrophysiological monitoring. Somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) are currently used as adjunct diagnostic methods in spinal surgery, such as scoliosis surgery and spinal stenosis decompression. Total intravenous anesthesia (TIVA) with propofol and opioids is commonly used in SEPs and MEPs monitoring as it causes increase in latency in comparison to inhalational anesthetics that cause decrease in amplitude . The amplitudes of MEPs and SEPs are reduced by halogenated volatile anesthetics, limiting their use in spinal surgery that requires electrophysiological monitoring. When volatile anesthetics did not exceed 0.3MAC, they had little effect on MEPs and SEPs . Martin et al. discovered that volatile agent-based anesthesia has application value during neurophysiological monitoring, such as faster awakening and rapid wake-up tests. As well, volatile anesthetics can reduce the dosage of propofol. As a result, spinal surgery benefits from combined intravenous inhalation anesthesia. As an adjuvant, dexmedetomidine may be useful in reducing the need for propofol. Dexmedetomidine is a potent and highly selective alpha-2 agonist. It has the effect of sedation, analgesia, sympatholytic, minimal respiratory depression and possible neuroprotection. Its addition to the anesthetic regimen is believed to have the potential of sparing other hypnotics requirement, especially propofol, thus facilitating MEP and SSEP monitoring while providing the beneficial effects it has.