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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.

Concentrations of atracurium and laudanosine in cerebrospinal fluid (CSF) and plasma were assayed in nine patients receiving atracurium infusions of 111-251 min duration to maintain neuromuscular block during intracranial surgery. The total dose of atracurium was 1.57-2.60 mg kg-1 and the plasma concentration of atracurium was 1.27-5.44 micrograms ml-1. Concentrations of laudanosine in CSF and plasma increased during the infusion period, and after 125-140 min reached means of 202.5 ng ml-1 and 1448.7 ng ml-1, respectively. The highest recorded concentration of laudanosine in CSF was 570 ng ml-1, in one of two CSF samples found to contain atracurium. After operation, two patients had fits, but these were not thought to be related to laudanosine. It is concluded that during infusion of atracurium, laudanosine accumulates in both plasma and CSF.