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Measuring the Influence of Anesthesiologists’ Medical Direction

Orkin, Fredrick K. M.D.

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To the Editor:—
Despite an Herculean analysis, Silber et al.1 are challenged when exploring the influence of the anesthesiologist’s medical direction on clinical outcome of surgical anesthesia. After adjusting for patient and hospital characteristics, they found “statistically significant” relations between absence of medical direction and both death and failure to rescue, but significance testing and related P values convey nothing about the magnitude of an intervention’s effect or clinical importance. Indeed, small differences of little clinical importance can be found to be statistically significant with very large study populations because P values are sensitive to sample size. More indicative of the importance of a factor in such a logistic regression analysis are the odds ratios. However, with odds ratios of 1.08 and 1.10, respectively, the influence of absence of medical direction seems very small, at least for an unselected patient population. By comparison, the odds ratios for relations between customary health risks and specific outcomes (e.g., cigarette smoking and lung cancer, asbestos exposure and mesothelioma, chronic alcoholism and hepatic cirrhosis) are in the range of 5 to 20, making inferences about the importance of these risk factors relatively easy.
Table 1
Table 1
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Trying to extract greater meaning from their analyses, Silber et al.1 note that absence of medical direction corresponds to 2.5 excess deaths per 1,000 anesthetic procedures. Given that there are an infinite number of “excess deaths” that might be avoided generally in health care with different interventions, one might wonder how the benefit of medical direction compares with those of other health care interventions. A handy way to compare interventions involves estimating the number of patients needed to be treated to prevent one negative outcome, 2 which in the Silber example would be 400 (i.e., 1,000 anesthetic procedures per 2.5 deaths). Compared with many other interventions (table 1), medical direction is much less effective but still within the spectrum of interventions that are widely thought to be beneficial.
Fredrick K. Orkin M.D.
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1. Silber JH, Kennedy SK, Even-Shoshan O, Chen W, Koziol LF, Showan AM, Longnecker DE: Anesthesiologist direction and patient outcomes. A nesthesiology 2000; 93: 152–63

2. Laupacis A, Sackett DL, Roberts RS: An assessment of clinically useful measures of the consequences of treatment. N Engl J Med 1988; 318: 1728–33

3. European Coronary Study Group: Long-term results of prospective randomised study of coronary artery bypass surgery in stable angina pectoris. Lancet 1982; 2: 1173–80

4. The Eclampsia Trial Collaborative Group: Which anticonvulsant for women with eclampsia? Evidence from the Collaborative Eclampsia Trial. Lancet 1995; 345: 1455–63

5. Veterans Administration Cooperative Study Group on Antihypertensive Agents: Effects of treatment on morbidity in hypertension: Results in patients with diastolic blood pressures averaging 115 through 129 mmHg. JAMA 1967; 202: 1028–34

6. Crowley PA: Antenatal corticosteroid therapy: Meta-analysis of the randomized trials, 1972 to 1994. Am J Obstet Gynecol 1995; 173: 322–35

7. The Canadian Cooperative Study Group: A randomized trial of aspirin and sulfinpyrazone in threatened stroke. N Engl J Med 1978; 299: 53–9

8. International Union Against Tuberculosis Committee on Prophylaxis: Efficacy of various durations of isoniazid preventive therapy for tuberculosis: Five years of follow-up in the IUAT trial. Bull World Health Organ 1982; 60: 555–64

9. Medical Research Council Working Party: MRC trial of treatment of mild hypertension: Principal results. Br Med J 1985; 291: 97–104

10. Nyström L, Rutqvist LR, Wall S, Lindgren A, Lindqvist M, Rydén S, Andersson I, Bjurstam N, Fagerberg G, Frisell J, Tabár L, Larsson L-G: Breast cancer screening with mammography: Overview of Swedish randomised trials. Lancet 1993; 341: 973–8

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Smith, AF; Kane, M; Milne, R
British Journal of Anaesthesia, 93(4): 540-545.
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