Transcranial magnetic-evoked potentials under total intravenous anaesthesia and nitrous oxide

Abstract

Magnetic stimulation of the cortex and recording of the motor-evoked potentials (MEPs) by electromyography (EMG) is a well proven method to assess the descending pathways of the spinal cord and detect neurological impairment. We have assessed, in 33 adult patients undergoing spinal surgery, the influence of four total i.v. anaesthesia regimens (TIVA) on this recording technique. In 20 patients, the effect of 50% nitrous oxide was also studied. MEP amplitudes, latencies and success rates of stimulation were obtained in the steady-state after induction of anaesthesia. Combinations of midazolam and ketamine, and alfentanil and etomidate had the least effect on MEPs. Propofol (in combination with alfentanil or ketamine) showed marked depression of the MEP amplitude and the lowest success rates of stimulation. The latencies did not change at all. The addition of nitrous oxide significantly depressed the registered MEPs and lowered the success rates.

Spatial–temporal patterns of electrocorticographic spectral changes during midazolam sedation

“…This is in line with the general notion that early evoked responses in the primary somatosensory region are often preserved during anesthesia, deep sleep, and vegetative state (Sloan et al, 1989; Alkire et al, 2008), when the association neocortex is deactivated (Laureys, 2005). A study of adult patients undergoing spinal surgery using transcranial magnetic stimulator reported that administration of midazolam had the least effect on motor-evoked potentials (Sihle-Wissel et al, 2000). Low-delta augmentation in the somatosensory-motor region might reflect the inhibition of the underlying cortical function as the result of sedation; low-delta activity during slow-wave sleep is generally associated with long-lasting neuronal hyperpolarization and cellular silence at the level of intracellular recording (Timofeev et al, 2001).…”

TMS and drugs revisited 2014

“…However, even among the intravenous anesthetics, there were differences with respect to the suppressive effect on MEP amplitude. MEP amplitudes were more profoundly depressed by propofol as compared to etomidate, although both drugs are thought to act mainly by activation of GABAARs (Sihle-Wissel et al, 2000). On the other hand, combining ketamine with propofol seemed to diminish the depressant effect of propofol (Sihle-Wissel et al, 2000).…”

“…MEP amplitudes were more profoundly depressed by propofol as compared to etomidate, although both drugs are thought to act mainly by activation of GABAARs (Sihle-Wissel et al, 2000). On the other hand, combining ketamine with propofol seemed to diminish the depressant effect of propofol (Sihle-Wissel et al, 2000). This might be explained by the fact that the intravenous anesthetic ketamine alone did not suppress MEP amplitude, but even led to MEP facilitation (Di Lazzaro et al, 2003).…”

High-frequency Stimulation Restored Motor-evoked Potentials to the Baseline Level in the Upper Extremities but Not in the Lower Extremities Under Sevoflurane Anesthesia in Spine Surgery

“…[1][2][3][4] However, MEPs are not widely utilized in the operating room because they are considerably affected by general anesthesia, especially with volatile anesthetics, including halothane, enflurane, isoflurane, sevoflurane, and desflurane. [10][11][12][13] In contrast, modulations in the stimulation pattern alter MEPs. [10][11][12][13] In contrast, modulations in the stimulation pattern alter MEPs.…”