Propofol Impairs the Central but Not the Peripheral Part of the Motor System

Abstract

Propofol provides some degree of muscle relaxation. Previous studies have investigated the effects of propofol on either the central or peripheral parts of the motor system. In this study, we simultaneously assessed both central (spinal) and peripheral effects. In 15 patients, general anesthesia was induced and maintained with fentanyl and midazolam. Neuromuscular blocking drugs were not administered. To investigate the central portion of the motor system, we monitored spinal F waves, an electrophysiologic variable of alpha-motoneuron excitability. Direct electrophysiologic muscle responses (M waves) and mechanomyography were studied to detect the peripheral effects of propofol on neuromuscular transmission or muscle contraction strength. After baseline recordings, 3 IV boluses of propofol (2 times 1 mg/kg followed by 2 mg/kg) were administered at 5-min intervals. Mean F-wave amplitudes were significantly reduced compared with baseline measurements (mean +/- SD, 0.22 +/- 0.13 mV) after the first (0.13 +/- 0.08 mV; P < 0.05), second (0.08 +/- 0.09 mV; P < 0.05), and third (0.03 +/- 0.04 mV; P < 0.01) propofol injections. M-wave amplitudes and mechanomyography signals remained unchanged. Our data suggest that the central part, but not the peripheral part, of the motor system is impaired after bolus administration of propofol.

L’anesthésie intraveineuse totale avec le propofol augmente la puissance du mivacurium

“…25,26 Lebeda et al 27 showed, in an isolated rat hemidiaphragm model, that propofol potentiates the neuromuscular blocking effect of vecuronium, only at higher drug concentrations. Fujii et al 28 determined that, in subhypnotic and anesthetic doses, propofol decreases the contractility of canine dia- 31 in a study in humans, confirmed the theory of propofol impairing the central portion, and not the peripheral portion, of the motor system. in patients under general anesthesia, using fentanyl and midazolam without neuromuscular blockade, he investigated the central portion of the motor system, by determining spinal F waves; and he recorded peripheral signals, by determining M waves and mechanomyography of the thumb.…”

Intraoperative Thresholds for Capsular Stimulation Are Reliable for Chronic Pallidal Deep Brain Stimulation in Dystonia

“…The sedative effect of propofol has been attributed to the tubero-mammillary nucleus of the hypothalamus [16], and the motor immobility effect may be caused due to a GABA A receptor agonism at the ventral horn of the spinal cord [17]. Studies in humans using intravenous bolus applications of propofol have demonstrated a decrease in spinal F-wave amplitudes, suggesting reduced excitability of spinal cord α-motoneurons [18]. In addition to this direct pharmacological influence, it is well known that voluntary muscular pre-innervation facilitates motor neuron excitability as demonstrated by motor-evoked potentials induced by transcranial magnetic stimulation [19].…”

Comparing the effects of three different additional doses of propofol infusion on intubation condition and hemodynamic changes during general anesthesia under elective surgery: A randomized, placebo-controlled, double blind clinical trial

“…The muscle relaxing mechanisms of intravenous anesthetics, especially propofol, have been investigated in several studies. [15161718] Some authors have demonstrated a central (cortical and spinal cord) mechanisms to describe muscle relaxing properties of propofol. Dueck et al .…”