Effects of Propofol, Etomidate, Midazolam, and Fentanyl on Motor Evoked Responses to Transcranial Electrical or Magnetic Stimulation in Humans

Propofol block of Ih contributes to the suppression of neuronal excitability and rhythmic burst firing in thalamocortical neurons

“…Anesthetic-induced unconsciousness is associated with lingering changes in electrophysiological activity (Kalkman et al, 1992;Reinsel et al, 1995) and postoperative cognitive function in humans (Moller et al, 1998;Johnson et al, 2002;Rasmussen et al, 2003). Those phenomena may result from longer-term alterations in the I h conductance following anesthetic exposure; this possibility was investigated by comparing I h currents and I h -dependent membrane properties in VB neurons from propofol-and vehicle-injected mice.…”

“…9). Clinical studies have shown that the electrophysiological effects of propofol persisted for several hours longer than the sedative effects in humans (Kalkman et al, 1992;Reinsel et al, 1995); the lingering actions of propofol on neuronal electrical activity may be a form of druginduced plasticity, and this may contribute to the phenomenon of transient postoperative cognitive dysfunction in humans (Moller et al, 1998;Johnson et al, 2002;Rasmussen et al, 2003).…”

“…Currents of the I h type are mediated by a family of hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels (Robinson & Siegelbaum, 2003), and of the four known molecular species, HCN2 is highly expressed in thalamocortical neurons (Notomi & Shigemoto, 2004), and appears to be the predominant functional isoform (Ludwig et al, 2003). Propofol has been reported to induce subtle functional effects in humans that are of longer duration than its clinical sedative effects (Kalkman et al, 1992;Reinsel et al, 1995), suggesting that the drug might also produce longer-term persistent changes in neuronal excitability. The ability of propofol to modulate, acutely or chronically, I h or the oscillatory activity of thalamocortical neurons is presently unknown.…”

Fentanyl‐induced suppression of transcranial Motor Evoked Potentials (tcMEPs)

“…Whereas, 98% amplitude reduction was seen after propofol administration. (5) It is unknown whether our patient's underlying metabolism disorder influenced this unusual tcMEP response to fentanyl. The synthetic opioid fentanyl undergoes extensive metabolism in humans.…”

Does ketamine affect intraoperative electrophysiological monitoring in children undergoing selective posterior rhizotomy?

“…Maintenance of anesthesia was achieved with sufentanil (0.3-0.6 mcgAEkgAEh )1 ) and propofol (4-10 mgAEkgAEh )1 ) infusions, and with N 2 O. Because propofol appears to depress motor evoked responses in a dose-response fashion (11,12) continuous infusion of low dose propofol (4-6 mgAEkgAEh )1 ) was used during the stimulation phase. No muscle relaxants or potent volatile anesthetics were used during the maintenance phase.…”