High and low surgical rates: risk factors for area residents.

Patterns of surgical practice, the type of operations performed, and risk characteristics of elderly patients brought to surgery are examined in areas with differing surgical rates. This population-based analysis covering Manitoba's 56 rural hospital areas uses discharge claims filed routinely with the provincial Health Services Commission. One and a half times as much surgery was performed in high rate areas (115.2 procedures per 1,000 elderly) as in low rate areas (74.7 procedures/1,000). Since surgical case mix varied little between high and low rate areas, the rate variation means that place of residence strongly influences exposure to major surgical procedures. In similar fashion, the proportion of surgical cases classified as high-risk does not vary with the surgical rate. High risk patients resident in high surgical rate areas are more likely to come to surgery than are their counterparts in low rate areas. Further analyses of nonsurgical hospitalization, of three common elective procedures, and of area characteristics were carried out. The surgical selection process, not characteristics of the population residing in the area, appears to determine the rate at which high and low risk patients come to surgery. Our research clearly suggests that high surgical rates carry with them the risk of excess surgical deaths.