Pattern of Breathing | Propofol

We assessed change of the pattern of breathing as a marker of induction of anaesthesia, using a method of maintaining spontaneous breathing throughout the induction period. We compared this index with a measure used clinically, the lash re¯ex, and measures used for drug investigations such as loss of grip of an object, cessation of ®nger tapping, and loss of arm tone. Ninety female patients (mean age 32 (17±63) yr, mean weight 63 (10) kg) were randomly allocated to induction of anaesthesia using propofol, methohexital, or sevo¯urane. The i.v. agents were given by slow injection estimated to give an induction dose (for weight drop end point) in 90 s.Sevo¯urane was given by progressively increasing the inhaled concentration to 8% so that induction should occur within 90±120 s. We measured time to change in breathing pattern, loss of voluntary ®nger tapping, loss of the lash re¯ex (tested at 15 s intervals), loss of postural tone in an...