This study used a mathematical simulation model to estimate the risk of adverse events due to unavailability of an anesthesiologist to attend to urgent problems. The risk of system failure was significantly higher when one anesthesiologist was required to cover more than two operating rooms and was also increased when multiple lengthy operations took place simultaneously. An Agency for Healthcare Research and Quality (AHRQ) WebM&M commentary discusses a devastating error that occurred when no anesthesiologist was available for an urgent cesarean section.