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Math Made Simple

Zvara, David A. MD

doi: 10.1213/00000539-200002000-00061
Letters to the Editor

Department of Anesthesiology Wake Forest University School of Medicine Winston-Salem, NC 27157-1009

I applaud Dr. Dexter et al. (1) for their study on deciding operating room assignments for second-shift anesthetists. Their study uses a statistical method that analyzes several operating room and surgeon variables with the intention of reducing “overtime hours” of first-shift anesthetists and thereby reducing anesthetist staffing costs. In their mathematical model, the authors use X to represent case duration for a specified scheduled procedure type and surgeon. The initial period of time for which the case has been ongoing is represented by d. Then, the expected value for the time remaining equals E[X − d]X > d] (1). I suggest a much simpler mathematical formula which has worked well for me in estimating the time remaining in a surgical case in a university-based practice: 2X + 30 = min until the surgeon (i.e., intern closing the wound) is actually finished, where X equals the surgeon’s answer in minutes to the question, “How much longer you gonna be?”

David A. Zvara MD

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1. Dexter F, Macario A, O’Neill L. A strategy for deciding operating room assignments for second-shift anesthetists. Anesth Analg 1999; 89:920–4.
© 2000 International Anesthesia Research Society