Alterations in response to somatic pain associated with anaesthesia. VIII. The effects of atropine and hyosine.

IN previous papers from this department, the effects of various premedicants on the response to somatic pain have been reported (Dundee and Moore, 1960; Moore and Dundee, 1961a, b). While opinions vary as to the best form of pre-anaesthetic medication, there is unanimous agreement on the need for an antisialogogue drug before general anaesthesia. Although a large number of these preparations are available, the majority of anaesthetists use atropine or hyoscine. In view of this, it was felt that the effects of these two drugs on the appreciation of pain warranted detailed study. This paper reports the results of such an investigation. The clinical significance of the findings is discussed with particular reference to the action of methohexitone and the relevant literature concerning the mechanisms involved in the effects of these drugs on pain threshold is reviewed. It has been shown by Mushin, Galloon and Lewis-Faning (1953) that the 0.6 mg dose of atropine leaves much to be desired as an effective pre-anaesthetic drying agent. This finding was confirmed by Galloon (1956) and Wyant and Dobkin (1957) although Diamant and Feinmesser (1959) found 0.5 mg of this drug to be satisfactory. However, there is no reliable information on the comparative potency of atropine and hyoscine other than the work of Wyant and Dobkin (1957) who gave 0.2 mg of each drug to volunteers and found hyoscine to be the more effective and reliable antisialogogue.