Effect of Physiotherapy on the Auditory Evoked Response of Paralysed, Sedated Patients in the Intensive Care Unit

Abstract

Auditory evoked response (AER) was recorded before, during and after physiotherapy in 11 paralysed (atracurium 0.56 (SD) 0.13 mg kg-1 h-1), sedated (propofol 2.2 (1.0) mg kg-1 h-1; fentanyl 4.4 (2.3) micrograms kg-1 h-1) and critically ill patients undergoing ventilation in the intensive care unit (ICU). The latency of the negative wave, NB, was reduced by physiotherapy (mean 44.8 (SD) 7.9 ms before, 41.0 (6.8) ms during (P less than 0.01, non-parametric Friedman test) and 45.6 (6.3) ms after physiotherapy); NB amplitude showed no consistent change (-0.81 (1.4) microV, -0.81 (1.5) microV and -0.71 (1.3) microV, respectively). NB latency responded to patient arousal at constant levels of sedation and this requires further evaluation as a means of monitoring sedation in paralysed patients in the ICU.

Cortical arousal in critically ill patients: an evoked response study

“…We set out to recreate the definitive experiment of Sneyd and colleagues [9], who demonstrated cortical arousal in paralysed ICU patients during physiotherapy by changes in Nb latency of mid-latency AER. In contrast to the patients in the study of Sneyd et al, our patients did not require muscle relaxants, therefore a clinical sedation score including muscle responses could be used in parallel with the electrophysiological recordings.…”

“…Sedation scoring is useful but cannot be applied in all patients in whom responses to potent stimuli such as tracheal suction may be absent due to the use of muscle relaxants or muscle paralyses. Sneyd and colleagues [9] recorded AER in 11 ICU patients and documented that Nb latency responded to patient arousal at constant levels of sedation. Moreover, the latency Nb decreased markedly during physiotherapy in survivors, while those patients who died showed a smaller response.…”

Evoked responses in anaesthesia

“…Several other workers found Nb latency to be the best correlate, out of a group of EEG variables, with loss of eyelash reflex 88 after propofol sedation and subsequent arousal after physiotherapy. 76 From reports of intraoperative awareness, using a variety of anaesthetic techniques, it is often noted that the auditory input is the last sensory modality to be abolished 23 39 48 and the first to return at light levels of anaesthesia. Patients anaesthetized for cardiac surgery are often studied, as a high incidence of awareness has been reported.…”

Responsiveness to stimuli of bispectral index, middle latency auditory evoked potentials and clinical scales in critically ill children

“…Other studies have evaluated the response of BIS and MLAEP to different stimuli in critically ill patients. Changes in MLAEP in critically ill adults after physiotherapy and tracheal suction were analysed in two studies [13,14]. A significant reduction in the latency of the negative wave Nb was observed in both studies after the stimuli, indicating a decrease in the level of sedation.…”

“…However, there are very few studies that have performed this evaluation in critically ill adults [13][14][15], and only one that has studied the use of BIS and the COMFORT scale following tracheal suctioning in critically ill children [16].…”