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CRNAs just as Safe as Anesthesiologists

Quality Summary of Pertinent Quality of Care Studies and Data

Pine Study in the AANA Journal [Pine, M, Holt, KD, Lou, YB. "Surgical Mortality and Type of Anesthesia Provider." AANA Journal. 2003;71:109-116.]

In the April 2003 AANA Journal, Dr. Michael Pine, a board-certified cardiologist widely recognized for his expertise in analyzing clinical data to evaluate healthcare outcomes, and a team of researchers published the results of a groundbreaking study titled "Surgical Mortality and Type of Anesthesia Provider." The study analyzed the effect of different types of anesthesia providers—specifically Certified Registered Nurse Anesthetists (CRNAs) and physician anesthesiologists—on the death rates of Medicare patients undergoing surgery

The results revealed that patients are just as safe receiving their anesthesia care from CRNAs or anesthesiologists working individually, or from CRNAs and anesthesiologists working together.

A. Rationale for Undertaking Study

According to the researchers, the study was undertaken:

  • To attempt to answer lingering questions about surgical patients' safety related to types of anesthesia providers, even though estimates of anesthesia-related deaths today are as low as 1 in 200,000 to 300,000 cases. [To Err is Human: Building a Safer Health System. Kohn, LT, Corrigan, JM, Donaldson, MS. Washington, DC: National Academy Press. 1999.]
  • To provide state governors with valid scientific data to help them decide whether their respective states should opt out of the federal physician supervision requirement for nurse anesthetists. [Federal Register. Vol. 66, No. 219, pp. 56762-56769.] Without such data, governors must rely on older studies (see analyses of Bechtoldt and Forrest studies, pp. 6-9 in this booklet) or seriously flawed studies (see analysis of Silber/Pennsylvania study, pp. 21-28 in this booklet).

B. Background

The researchers studied 404,194 Medicare cases that took place from 1995-1997 in 22 states. Only cases with clear documentation of type of anesthesia provider were studied, and adjustments were made for differences in case mix, clinical risk factors, hospital characteristics, and geographic location. The types of surgical procedures included carotid endarterectomies, cholecystectomies, herniorrhaphies, mastectomies, hysterectomies, laminectomies, prostatectomies, and knee replacements.

Groundbreaking Results. The Pine study yielded the following important findings:

  • Mortality rates were similar for CRNAs and anesthesiologists working individually.
  • There was no statistically significant difference in the mortality rate for CRNAs and anesthesiologists working together versus CRNAs or anesthesiologists working individually.
  • There was no statistically significant difference in the mortality rate for hospitals without anesthesiologists versus hospitals where anesthesiologists provided or directed anesthesia care.

C. Conclusions

Pine et al. concluded the following:

  • That while their findings differed from those of Silber et al. (see analysis of Silber/Pennsylvania study, pp. 21-28 in this booklet), they were consistent with earlier research and with current data which estimate that anesthesia-related deaths today are as low as 1 in 200,000 to 300,000 cases. [To Err is Human: Building a Safer Health System. Kohn, LT, Corrigan, JM, Donaldson, MS. Washington, DC: National Academy Press. 1999.]
  • That based on the surgical procedures included in the study, inpatient surgical mortality is not affected by whether the anesthesia provider is a CRNA or an anesthesiologist.

Pine Versus Silber. The Silber/Pennsylvania study (see analysis on pp. 21-28 in this booklet), which was published nearly three years before the Pine study, contained glaring methodological deficiencies that Pine et al. endeavored to avoid. Specifically, approximately two- thirds of the cases which Silber et al. classified as not involving an anesthesiologist in the patient care either A) actually did have an anesthesiologist involved in some, but not all, of a patient's procedures, or B) had no bill for the anesthesia care (making it impossible to confirm whether an anesthesiologist was or was not involved).

Further, cases in which anesthesiologists worked alone were not distinguished from those in which CRNAs and anesthesiologists worked together. Finally, only cases in one state—Pennsylvania—were included in the Silber study.

This failure by Silber et al. to more accurately quantify the cases in which anesthesiologists were involved led the researchers to conclude that there was an increase of 2.5 deaths per 1,000 patients when an anesthesiologist was not involved in the case. This inflated ratio was alarmingly out of sync with the Institute of Medicine's (IOM's) published report that anesthesia mortality rates today are approximately 1 death per 200,000 to 300,000 anesthetics administered, a ratio also routinely cited by the American Society of Anesthesiologists (ASA). [To Err is Human: Building a Safer Health System. Kohn, LT, Corrigan, JM, Donaldson, MS. Washington, DC: National Academy Press. 1999.] Had Silber et al. identified a more accurate (i.e., larger) number of cases as involving anesthesiologists, the ratio obviously would have been much different.

Pine et al. sought to avoid the limitations that marred the Silber study by taking the following steps:

  • Studying cases from 22 states, instead of just a single state.
  • Using only cases that clearly identified the type(s) of anesthesia provider involved in the patient care.
  • Distinguishing between care provided by CRNAs and anesthesiologists working together and care provided by anesthesiologists or CRNAs working individually.

The results of the efforts by Pine et al. to attribute anesthesia care to the correct providers) was twofold: 1) The researchers attained data that is more consistent with current overall anesthesia-related mortality rates cited by the IOM, the ASA, and the American Association of Nurse Anesthetists, and 2) they found no statistically significant difference in mortality rates when anesthesia is given by a CRNA working individually, an anesthesiologist working individually, or CRNAs and anesthesiologists working together.

Pine Rebuttal to ASA Comments on Pine Study. In May 2003, the "ASA Preliminary Comment on Pine Study" was released. In a gross misinterpretation of the Pine study results, the ASA claimed that Pine et al. found 38 deaths per 10,000 cases in hospitals where anesthesiologists administered or directed all anesthetics, and 45 deaths per 10,000 cases when an anesthesiologist was not involved. From this, ASA suggested that "the Pine study data support what most recent studies have found—that anesthesiologists improve anesthesia outcomes." [ASA Preliminary Comment on Pine Study. Lobbying day handout. May 2003.]

That same month, Dr. Pine wrote "Response to 'ASA Preliminary Comment.'" He stated that for the ASA to suggest that his study's data supports "the conclusion 'that anesthesiologists improve anesthesia outcomes'" is evidence of "either a woeful ignorance of the basics of data analysis or a cynical contempt for the intelligence of the intended audience." Defending his study, Dr. Pine wrote that his data actually found 34 deaths per 10,000 cases when CRNAs administered anesthesia while working together with anesthesiologists, and 45 deaths per 10,000 cases when anesthesiologists worked without a CRNA. He pointed out that this difference of 11 deaths per 10,000 cases was "even more impressive than the 7 deaths per 10,000 cases" difference cited by the ASA (see paragraph above), and that based on this data, "the AANA could claim that anesthesiologists should not be permitted to administer anesthesia unless a CRNA is present to prevent the excess mortality associated with physicians attempting to engage in the practice of nursing. However, unlike the ASA, the AANA has enough respect for its audience to avoid making such unwarranted claims."

Dr. Pine reiterated his study's findings that after risk adjustment there is no statistically significant difference between CRNAs working individually, anesthesiologists working individually, or CRNAs and anesthesiologists working together. He added that his study's data support the conclusion that even when there are two anesthesia providers working together, substituting an anesthesiologist for a CRNA does nothing to lower the mortality rate. [Pine, M. Response to "ASA Preliminary Comment."www.aana.com. May 2003.]
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