Quantitative surface electromyography in anesthesia and critical care

Abstract

The frontalis muscle spontaneous (SEMG) and electrically evoked (EEMG) electromyograms were recorded in 4 different clinical settings. Using a standardized isoflurane-based anesthetic protocol. Study 1 examined the SEMG response to both surgical and acoustic stimuli. The acoustic SEMG response was also examined in comatose head-injured patients. Study 2 used the EEMG to compare the extent of vecuronium-induced neuromuscular blockade on the frontalis and hypothenar muscles in both anesthetized and comatose patients. In Study 3 head-injured comatose patients were used to investigate the relationship between SEMG changes and transient elevations in intracranial pressure (ICP). The effect of opiate analgesics on the pain-activated SEMG in conscious post-operative patients was investigated in Study 4. These studies illustrate the following phenomena. First, in conscious, unparalyzed or lightly anesthetized patients, painful (stressful) stimuli are associated with increases in SEMG amplitude. Thus, the SEMG may indicate periods of inadequate analgesia, not only post-operatively (Study 4) but also intra-operatively (Study 1), since we found the frontalis to be relatively insensitive to a non-depolarizing neuromuscular blocker (Study 2). However, the interpretation of intra-operative SEMG changes may be confounded by opiates (Study 4) and perhaps other agents capable of influencing the frontalis through either non-nociceptive central or peripheral mechanisms. Second, the opiate analgesics consistently decreased SEMG amplitude in non-tolerant conscious patients (Study 4. Although this opiate-induced decrease is not necessarily indicative of opiate analgesia, it may provide an objective, quantifiable measure of a central opiate effect. The SEMG is particularly well-suited to determine the precise timecourse of this effect. Third, in deeply anesthetized or comatose patients, unresponsive to either surgical or electrical stimulation. SEMG amplitude may increase in response to elevated ICP or certain sounds (Study 3). The stress (pain) and auditory-evoked SEMGs may thus provide measures of brainstem function that are independent of the level of consciousness.

Entropia espectral: um novo método para adequação anestésica

“…AEMGs da musculatura frontal fornece uma simples e não invasiva medida de um aspecto do tônus autonômico. Contrações voluntárias e involuntárias da musculatura frontal são respostas representadas por inervações através de vias distintas, assim como a atividade tônica (basal) e a atividade fá-sica (abruptamente aumentada) na EMGs podem ser diferentemente afetadas por níveis alterados de vigilância ou agentes bloqueadores neuromusculares [23][24][25] . A diminuição da vigilância que acompanha a indução da anestesia geral é tipicamente associada com dramática diminuição na atividade frontal tônica.…”

“…Frontal muscles EMGs provides a simple and noninvasive measure of an autonomic tone aspect. Voluntary and involuntary frontal muscles contractions are responses brought by different pathways innervation, as well as tonic activity (basal) and phase activity (abruptly increased) may be differently affected by abnormal levels of vigilance or neuromuscular blockers [23][24][25] . Decreased vigilance following general anesthesia is typically associated to dramatic decrease in tonic frontal activity.…”

“…Lennon 31 has concluded that moderate neuromuscular block levels may be achieved without impairing electromyographic monitoring of the facial nerve. Edmonds 25 has shown that EMGs in response to stress (pain) may assess brainstem function, which is independent of consciousness level (cortex). Dutton 32 in a recent study has concluded that electromyographic response may be used to estimate anesthetic depth.…”

Entropia: um novo método de mensuração da profundidade da anestesia. Estudo comparativo com o índice bispectral na avaliação clínica da intubação traqueal com sevoflurano

“…AEMGs da musculatura frontal fornece uma simples e não invasiva medida de um aspecto do tônus autonômico. Contrações voluntárias e involuntárias da musculatura frontal são respostas representadas por inervações através de vias distintas, já que a atividade tônica(basal) e a atividade fásica (abruptamente aumentada) na EMGs podem ser diferentemente afetadas por níveis alterados de vigilância ou agentes bloqueadores neuromusculares [13][14][15] . A diminuição da vigilância que acompanha a indução da anestesia geral é tipicamente associada com a dramática diminuição na atividade frontal tônica.…”

“…Frontal muscles EMG S provides a simple and noninvasive measurement of an autonomic tone aspect. Voluntary and involuntary frontal muscles contractions are responses represented by innervations through different pathways, since EMG S tone activity (baseline) and phase activity (abruptly increased) may be differently affected by abnormal alertness levels or by neuromuscular blockers [13][14][15] . Decreased alertness following general anesthetic induction is typically associated to dramatic frontal tone activity decrease.…”