Careful Examination Of The "Findings" Reported In The Abstract Reveal Numerous Problems

The study was conducted using data obtained from Health Care Financing Administration (HCFA) claims records. The study group consisted of 65,595 Medicare patients distributed across 219 hospitals in Pennsylvania who underwent general surgical or orthopedic procedures between 1991-94. Jeffrey H. Silber, MD, PhD, headed a research team that included three anesthesiologists. The abstract has been published (Anesthesiology, 1998; 89:A1184); however, no peer-reviewed article about the study results has been published to date. Study Does Not Answer the Question Posed by the Abstract's Title According to David E. Longnecker, MD, one of the anesthesiologist researchers involved in the study:

"The study … does not explore the role of (nurse anesthetists) in anesthesia practice, nor does it compare anesthesiologists versus nurse anesthetists. Rather, it explores whether anesthesiologists provide value to the delivery of anesthesia care." (Source: Memorandum from Dr. Longnecker to Certified Registered Nurse Anesthetists in University of Pennsylvania Health System's Department of Anesthesia, October 5, 1998)
Why, then, was such a misleading title chosen? The answer can only be for political reasons. Consider these facts:

the abstract was published in the midst of the controversy between anesthesiologists and nurse anesthetists over HCFA's proposal to remove the physician supervision requirement for nurse anesthetists in Medicare cases, and 
the study was funded in part by a grant from the American Board of Anesthesiology, which is affiliated with the American Society of Anesthesiologists (ASA). The ASA vehemently opposes HCFA's proposal.
Problems with the Data Glaring Admission: The researchers conclude the abstract by admitting that it "remains to be determined" whether their findings were the result of "a caregiver or hospital effect" (or, in layman terms, whether their findings were due to the actions of the nurse anesthetists/physicians or to the hospital environments). This admission by the researchers seriously limits the application of the data. The significance of a hospital's environmental characteristics on patient outcomes cannot be underestimated given these facts:

Anesthesiologists are heavily concentrated in urban and suburban areas where they typically practice in well-funded, high-tech, appropriately staffed hospitals and surgical centers. 
Nurse anesthetists, on the other hand, often play major roles in rural and inner-city hospitals, facilities where anesthesiologists don't generally work. What this means is: nurse anesthetists often treat sicker patients in facilities that don't have the same caliber resources to which anesthesiologists are accustomed