Effect of suxamethonium on the auditory evoked response in humans

Abstract

We have studied the arousal effect of suxamethonium on the auditory evoked response (AER) of the electroencephalogram (EEG) in 40 ASA I and II patients during isoflurane anaesthesia. After induction of anaesthesia, the patient's lungs were ventilated for 20 min with 0.6 MAC end-expiratory isoflurane (0.59-0.77% depending on the age of the patient), and 50% nitrous oxide in oxygen. The patients were then allocated randomly to one of two groups: 21 received suxamethonium 1 mg kg-1, while 19 were given saline. The AER before and after administration of suxamethonium or saline was compared to determine the changes in Pa and Nb amplitudes and latencies. Pa amplitude after suxamethonium increased by 53% (95% confidence interval (CI) 15, 104%) compared with a reduction in Pa amplitude in the saline group of 19% (95% CI, -41, 12%) (P = 0.004) suggesting an arousal effect. Similarly, Nb amplitude increased in the suxamethonium group by 47% (95% CI, 3, 110%) and decreased in the saline group by 11% (95% CI, -33, 19%) (P = 0.03). We conclude that suxamethonium caused arousal according to the AER and postulate that this may have been caused by increased muscle afferent activity after stimulation of muscle spindles, although further studies are required to confirm this.

Intraoperative dreams reported after general anaesthesia are not early interpretations of delayed awareness

“…In this study, U-dreams were significantly more prevalent if NMB [suxamethonium (SUX) and/or non-depolarising muscle relaxant (NDMR)] was used, in a univariate analysis. SUX, but not NDMR, causes arousal as indicated by auditory-evoked responses (14,15). This arousing effect is probably due to SUX-induced muscle contraction (16), because pre-treatment with tubocurarin reduced the incidence of dreams from 16.7% to 2.8% (17).…”

Does the A-line ARX-Index provide a reasonable assessment of anaesthetic depth in dogs undergoing routine surgery?

“…Auditory stimuli have been used to assess anaesthetic depth 16,31 . The auditory-evoked response has been found to have a predictable and consistent dose-dependent response with various anaesthetic agents 5,14,26,30,37 . Volatile anaesthetic agents have been shown to exert similar effects on the auditory-evoked response based on comparison of minimum alveolar concentration multiples in humans 14 .…”

“…Traditionally, awareness during anaesthesia has been based on sympathetic, haemodynamic, respiratory, ocular (mydriasis, myosis, 'fish eye') and neurological reflex (palpebral, pedal and corneal reflex) responses. Objective criteria for the assessment of anaesthetic depth are lacking 5 . Anaesthetic agent requirements vary between patients dependent on age, gender, cardiac output, clinical condition, serum proteins, preanaesthetic drug administered and mass 15 .…”

“…Volatile anaesthetic agents have been shown to exert similar effects on the auditory-evoked response based on comparison of minimum alveolar concentration multiples in humans 14 . The auditory-evoked response has also been used to show that neuromuscular blocking agents do not decrease a patient's requirement for anaesthesia in humans 5,29 . The auditory-evoked response consists of a set of electrical impulses (brain waves) that are formed when a sound is delivered at the external auditory meatus.…”