Electrophysiological evaluation of spinal reflexes during epidural anesthesia in an experimental model

Abstract

We assessed the effects of epidural anesthesia with bupivacaine in the rat by serial recordings of spinal reflexes. The H wave from plantar muscles after electrical stimulation of the sciatic nerve evaluates a large nerve fiber spinal reflex arch. The extensor reflex response recorded from quadriceps muscle after stimulation of the contralateral tibial nerve assesses a reflex arch with small fiber afferents. After epidural injection of 0.2 mL of bupivacaine (0.25%, 0.5%, and 1.0% solutions) at the L5‐L6 vertebral space, nociceptive, H, and extensor reflex responses were abolished within 1–3 min. Duration of complete blockade lasted 20–80 min, increasing with the anesthetic concentration, and complete recovery occurred after an additional period of 30–40 min. The responses recovered to amplitudes similar to preanesthesia controls, indicating that there was no damage to the nervous system. This study shows that electrophysiological recording and quantitation of nerve reflex responses is a useful and accurate method to evaluate the efficacy of local anesthetic agents. © 1996 John Wiley & Sons, Inc.

On the use of fast blue, fluoro-gold and diamidino yellow for retrograde tracing after peripheral nerve injury: uptake, fading, dye interactions, and toxicity

“…The sciatic nerve was stimulated by two needle electrodes percutaneously inserted at the sciatic notch, applying single rectangular pulses of 0.05 msec duration up to the voltage required to obtain a maximal evoked response. Compound muscle action potentials (CMAP), evoked by stimulation of motor nerve fibres, were recorded from the medial gastrocnemius (GM), anterior tibialis (TA), and plantar (PL, from the 3rd metacarpal space) muscles using monopolar needles (Navarro et al, 1994(Navarro et al, , 1996. Compound nerve action potentials (CNAP), elicited by stimulation of large sensory nerve fibres, were recorded with small needle electrodes inserted near the digital nerves in the proximal (active electrode) and distal (reference electrode) phalanges of the second, fourth and fifth toes.…”

Prolongation of Epidural Analgesia Using Solid Lipid Nanoparticles as Drug Carrier for Lidocaine

“…Electromyographic recordings have been used to evaluate the motor function of spinal reflex responses associated with different types of afferent and efferent nerve fibers after bupivacaine epidural injection. 22 They include maximal amplitude, latency to onset, and duration of the evoked MUAPs of H responses and extensor reflex responses (both are spinal reflex responses). These methods can provide a more reliable and quantitative evaluation of epidural anesthesia than subjectively assessed responses to painful electrical stimuli.…”

“…The measurements were then used to assess the effectiveness of epidural anesthesia through the lumbar segments. 22 Briefly, the extensor reflex response was elicited with electrical pulses from 2 needle electrodes, applying single squared pulses (1 mV, 0.2 millisecond, 1 Hz) to obtain compound muscle action potentials. The cathode was placed adjacent to the tibia1 nerve at the ankle, and the anode was inserted in the skin of the dorsum of the paw.…”

Prolongation of Nerve and Epidural Anesthetic Blockade by Bupivacaine in a Lipid Emulsion

“…After aspiration for evidence of blood or cerebrospinal fluid proved negative, 0.2 mL of the bupivacaine preparation was slowly injected over 20 s (21). The injection point is equidistant between the knee and the L6 spinal process, and it corresponds to the space around the sciatic nerve above its trifurcation.…”

“…Neurophysiological techniques designed to quantitatively assess the function of lumbar spinal reflex arches were used to evaluate the epidural blockade (21). The myotatic stretch reflex was evaluated by the H wave, which was recorded by using motor nerve conduction tests set as above.…”