British Journal of Anaesthesia Pentazocine and Tremor following Halothane Anaesthesia

Sir,—Muscular spasticity and tremor occurs during recovery from general anaesthesia, especially following halothane (Dawkins, 1961), and may be associated with hypoxaemia (Jones and McLaren, 1965). This condition may be prevented or controlled by methylphenidate (Brichard and Johnstone, 1970). However, this drug is an unreliable analgesic, may provoke adrenergic overactivity (Brichard and Johnstone, 1970), causes amphetamine-like drug dependence (Willis, 1974) and is usually included in the D.D.A. drug schedule. To test the hypothesis that pentazocine might be an effective substitute for methylphenidate in controlling muscular spasticity and tremor following halothane we studied 100 consecutive patients who developed this condition. Fifty-four patients were given pentazocine 30 mg i.v., and 46 received methylphenidate 20 mg i.v. The patients were allocated randomly to the groups which were comparable in terms of age of the patient and type of operation. The same anaesthetic technique was used although this was not standardized and the duration of anaesthesia was not recorded. The patients were observed in the recovery room for 30 min by a trained nurse who did not know which drug had been given. The nurse was asked to record only the presence of tremor, which was regarded as a more objective assessment to make than spasticity. In all except one of the patients given methylphenidate tremors stopped within a few minutes of the drug being administered and they did not recur. In the one exception, tremor ceased immediately after administration of methylphenidate but recurred slightly. With pentazocine the tremors stopped quickly and did not recur in 46 of the patients, but recurred slightly in seven and were not affected in three. Pentazocine does not control tremor following halothane anaesthesia as well as methylphenidate, but, where hypoxia is not a serious problem and pain is present, pentazocine 30 mg i.v. reduces both ridigity and tremor and provides useful analgesia with less book-keeping for the nursing staff. E. N. S. FRY S. DESHPANDE Stockton-onTees