RISKS RELATED TO THE ANESTHESIA PROVIDER

The added risk associated with the provider of anesthesia is an emotionally charged issue, particularly in the United States. Over the history of the specialty, various individuals have provided anesthesia, including anesthesiologists, general medical officers, residents, and CRNAs.

The importance of the anesthesiologist to outcome is best illustrated by the work of Slogoff and Keats.^[196] They studied the association of perioperative myocardial ischemia and cardiac morbidity in patients undergoing coronary artery bypass grafting. They found that perioperative myocardial infarction occurred significantly more frequently in patients with ischemia before the bypass operation. They then reported the rate of ischemia and infarction by anesthesiologist (identified by number). Anesthesiologist no. 7 had a significantly higher rate of complications than the average for the rest of the group. Operator technique or experience may affect risk. This observation parallels similar findings that surgical volume (and presumably experience) is associated with outcome.

Several studies have attempted to evaluate the complication rates and risks associated with various care provider models. Bechtoldt,^[197] as a member of the North Carolina Anesthesia Study Committee, evaluated 900 perioperative deaths from an estimated 2 million anesthesia procedures performed in North Carolina between 1969 and 1976. Data were obtained from the medical examiner's report, the routine death certificate, and a questionnaire completed by the person who administered the anesthetic.

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The Stanford Center for Health Care Research^[198] also evaluated the impact of provider on outcome of care. They prospectively collected data from 8593 patients undergoing 15 surgical procedures over a 10-month period (May 1973 through February 1974). Using a risk-adjustment methodology, the actual patient outcome was compared with that predicted by the patient's health status and operative procedure. The investigators reported that death plus severe morbidity was 11% higher than predicted for patients who received their care in a nurse anesthetist-only setting, 3% lower than predicted for physician-only care, and 20% lower than predicted for an anesthesia care team environment. Because of the small sample size, these

Figure 24-8 Relationship between anesthesia provider and anesthesia-related deaths in North Carolina. The number of cases performed by each group was estimated from a survey of hospitals. The certified registered nurse anesthetist (CRNA) and the anesthesiologist care team were associated with the best outcomes, whereas the surgeon or dentist practicing anesthesia was associated with the worst. (From Bechtoldt AA: Committee on anesthesia study. Anesthetic-related deaths: 1969–1976. N C Med J 42:253, 1981.)

The differences in outcome among anesthesia providers are extremely difficult to study from a methodologic standpoint. The impact of specific provider types may be greatest in specific situations. For example, there may be no difference in outcome for healthy individuals, particularly if no complications occur. In contrast, patients with significant comorbidities and those who sustain perioperative complications may benefit from having providers with specific skill sets. One way to study such issues is to evaluate the rate of survival after complications. Silber and colleagues ^[199] at the University of Pennsylvania advocated such an approach. They studied the medical records of 5972 surgical patients randomly selected from 531 hospitals. They evaluated patient and hospital characteristics, including the number and type of physicians, board-certification status, and ratio of care providers. The 30-day mortality rate correlated with patient characteristics. Failure to rescue (i.e., prevent death) after an adverse event was inversely associated with the proportion of board-certified anesthesiologists on staff in each facility. Improved perioperative survival was significantly associated with the presence of an increased number of board-certified anesthesiologists.

As a follow-up to this study, Silber and colleagues^[200] compared the outcomes of surgical patients for whom anesthesia care was or was not personally performed or medically directed by an anesthesiologist. Medicare claims records were analyzed for all elderly patients in Pennsylvania who underwent general surgical or orthopedic procedures between 1991 and 1994. The 30-day mortality rate and the mortality rate after complications (i.e., failure to rescue) were lower when anesthesiologists directed anesthesia care, even after adjustment for patient and hospital characteristics.

Silber and colleagues^[201] employed similar methodology to determine the importance of board certification in perioperative risk. Adjusted odds ratios for death (1.13; 95% CI: 1.00–1.26; P < .04) and for failure to rescue (1.13; 95% CI: 1.01–1.27; P < .04) were greater when care was delivered by noncertified, midcareer anesthesiologists.

The marked increase in the number of anesthesiologists has been paralleled by a dramatic decrease in malpractice insurance premiums for anesthesiologists. ^[202] Because these premiums are based on the number and severity of claims, these data suggest that anesthesia is getting safer. The issue remains unresolved, and further research into the importance of anesthesia provider to outcome is required.