Canadian Journal of Anesthesia, Vol 29, S7-S10, Copyright © 1982 by Canadian Anesthesiologists' Society

Clinical Evaluation of Isoflurane: Regional Geographic Demography

The most significant geographic differences relate to the incidence of the drugs as premedication and for induction of anaesthesia and the concentration of isoflurane used. Thus narcotic use in premedication was much more common in institutions in the NE and NC regions, whereas narcotic use at induction was more common in the South and in Canada. The effect of these different patterns of prescribing of narcotics had the effect of influencing the isoflurane concentration used. The use of anticholinergics showed a three-fold difference between the NC region and Canada, undoubtedly reflecting different approaches to the need for vagolytic action.

The prevalence of disease and coexisting cardiorespiratory drug therapy was higher in the South and NE in most instances. It is likely that this reflects the older mean age of patients in these regions. However, the proportion of patients over 80 years of age was highest in Canada and least in the Western region where respiratory, circulatory, and CNS disease were rather more frequent. The significant differences for some procedures, for example EENT and intraabdominal, could not be explained on the basis of age differences alone.

Apart from different rates of disease and the influence that has on rates for the various procedures, it seems likely that an important determinant of the latter as well as of the anaesthetic drugs used before, during, and after operation relates to what might be described as "usual practice". The outcome of such differences in terms of morbidity and complications requires detailed and careful analysis which must take account of the many patient factors as well. Although there were differences for reflex activity and complications between regions, these were such that no clear explanation of their occurrence could be made on the basis of regional factors. The later sections on reflex activity by Dr. C. Buffington and complications by Dr. K. Rehder describe, in detail, the results of the analysis of patient and demographic factors related to these outcomes.