Additional References on the Epidemiology of Anesthesia Complications in Labor and Delivery

To the Editor: Readers who found the article by Cheesman et al.1 on the epidemiology of anesthesia-related complications in labor and delivery of interest may also be interested in 2 additional studies using very similar data and methods encompassing an additional 1.3 million patients that were not cited in the references of the article. The first2 describes the incidence of anesthesia complications among 135,000 cesarean deliveries in Washington state in the years 1993 to 2004, whereas the second3 addresses 1.1 million obstetrical patients in 6 states for the year 2002. Although these 2 studies show a similar incidence of anesthetic complications as that reported by Cheesman et al., neither article supports the conclusion that rural patients experience a greater incidence of anesthetic complications. This may be because the authors of the 2 articles were able to look at patients by hospital, whereas Cheesman et al. only identified rural patients by zip code. In addition to the problem of rural patients potentially going to urban hospitals for delivery, and thus confounding the analysis, Simonson et al.2 found that because of the far smaller numbers of deliveries for rural hospitals, it is important to apply appropriate statistical methods (such as hierarchical data modeling) when comparing rural with urban hospitals. These methods are unavailable if you do not have the ability to identify patients by hospital as well as zip code. Daniel C. Simonson, CRNA, MHPA The Spokane Eye Surgery Center Spokane, Washington [email protected]