Control chart monitoring of the numbers of cases waiting when anesthesiologists do not bring in members of call team
INTRODUCTION: An anesthesia group staffing agreement with a hospital often specifies the minimum number of operating rooms (ORs) to be covered during evening or weekend hours. Frequently, 1 anesthesiologist works in-house and others take call from home, coming in if multiple cases are waiting to be done. The anesthesiologist in-house sometimes does not bring in colleagues from home when the number of ORs he can supervise is less than the number specified in the agreement with the hospital (i.e., assignment is less than staffing). Queuing occurs even if managers have selected an appropriate number of ORs to be run during evenings and weekends (i.e., the number of cases [jobs] exceeds the number of ORs [identical machines] that are actually run). METHODS: In our study, we used a dataset without trend over 3 years to determine whether we could identify differences among anesthesiologists in queuing behavior. Negative binomial regression was usedto model the number of cases waiting while the numberof ORs running was fewerthan allocated. Multiple variable regressions modeled waiting times among cases. The easy to construct Shewhart chart and the more complicated cumulative sum chart were then compared to test for outliers in the number of cases waiting. RESULTS: Queuing behavior was found to be homogeneous among the 33 anesthesiologists (P> 0.28 among different statistical models). Weekend days differed from evenings. Shewhart and cumulative sum charts were comparable for detecting unusual variations. CONCLUSIONS: Anesthesiologists sometimes do not notify call team members when cases are waiting and the number of ORs running is less than allocated. The number of cases waiting, rather than the amount of waiting, is more appropriate for monitoring trends over time. Simple Shewhart charts can be used for monitoring contractually specified staffing. Copyright © 2010 International Anesthesia Research Society.