Mortality, LOS, and Cost Not Significantly Impacted by Anesthesiology Team Composition

Eric Sun, MD, PhD

New data has shown that regardless of whether the anesthesiologist is assisted by a nurse anesthetist or anesthesiologist assistant, patients undergoing surgery experience no significant differences in mortality, length of stay, or inpatient costs.

In the United States, nurse anesthetists are able to practice nationwide, while anesthesiologist assistants are limited to practice in 16 states. As such, the research team sought to explore if the composition of the anesthesiology team was linked with differences in perioperative outcomes.

Led by Eric Sun, MD, PhD, an assistant professor of anesthesiology, perioperative and pain medicine at the Stanford University Medical Center, the team performed a retrospective analysis of 443,098 elderly patients aged 65 to 89 years, who underwent an inpatient surgical procedure between January 1, 2004, and December 31, 2011. The approach used a quasi-randomization method known as instrumental variables in order to reduce confusion, the authors noted.

The final sample consisted of 421,230 surgical cases in which the anesthesia care team included a nurse anesthetist and an anesthesiologist, and 21,868 cases in which the anesthesia care team was made up of a physician anesthesiologist and an anesthesiologist assistant.

“Arguments against expanding the number of states where anesthesiologist assistants may practice generally focus on the possibility that health outcomes may be worse when anesthesiologist assistants provide anesthesia care,” Sun said in a statement. “Nonetheless, until now, it has not been known whether these concerns are warranted and whether there actually is a difference in outcomes depending on whether a physician anesthesiologist works with a nurse anesthetist or an anesthesiologist assistant.”

“We found that is not the case. Being supervised by a physician anesthesiologist lessens any differences in background and training between nurse anesthetists and anesthesiologist assistants,” he added.

The analysis showed that the adjusted rate of mortality for teams with anesthesiologist assistants was 1.6% (95% CI, 1.4 to 1.8) compared to 1.7% for teams with nurse anesthetists (95% CI, 1.7 to 1.7) for a difference of —0.08 (95% CI, –0.3 to 0.1; P = .47).

Additionally, while both length of stay and spending were slightly lower with anesthesiologist assistants, the differences were not significant. Length of stay was 0.009 days fewer (95% CI, —0.1 to 0.1; P = .89), and spending was $56 less (95% CI, —334 to 223; P = .70) with teams that had anesthesiologist assistants.

"The article shows that anesthesia care provided by an anesthesiologist assistant or nurse anesthetist is equivalent when led by a physician anesthesiologist,” Sun said. “Our results suggest that physician supervision is able to ensure the same outcomes regardless of the team member’s differences in training and background.”

Anesthesiologist assistants provide care under the supervision of a physician anesthesiologist at all times, while nurse anesthetists typically practice with a physician in a team style model. There are some locations where nurse anesthetists can practice in a nurse-only model.

Both providers obtain advanced training in anesthesiology, but there are slight differences. Nurse anesthetists receive additional training in anesthesiology through a nurse anesthetist program, which typically requires candidates to have a Bachelor of Science in Nursing, professional nursing experience, and a valid nursing license. Anesthesiologist assistants receive their training through an anesthesiologist assistant program, which often requires a bachelor’s degree with premedical coursework, including completing a comprehensive graduate school level didactic and clinical program.

The study, “Anesthesia Care Team Composition and Surgical Outcomes,” was published in Anesthesiology.