Statistical Analysis of PACU Fast-Tracking Bypass

LETTERS TO THE EDITOR Statistical Analysis of PACU Fast-Tracking Bypass To the Editor: Rice et al1 state that ‘‘the financial advantages of fast-tracking patients have not been fully studied.’’ There is a list of peer-reviewed articles in the economics of the postanesthesia care unit (PACU) at http://www.FranklinDexter.net/bibliography_ PACUStaffing.htm. Our 1999 article has bypass in the title.2 What search protocol(s) did the authors use to find prior financial studies? The authors’ cost analysis on page 131 assumes that PACU labor costs are variable.1 It was 20 years ago that we showed that generally this is not so.3 The necessary data are known.2,3 During the authors’ reference and implementation periods,1 what were the percentages of all patients who bypassed the phase I PACU, the mean daily numbers of all PACU patients, and the numbers of full-time equivalent PACU nurses for phase I and II PACUs? The authors’ page 128 reports a comparison of incidences of PACU hold using the Mann-Whitney test.1 How was this test of ordinal variables used to compare incidences? The authors use the Mann-Whitney and Fisher’s exact tests,1 which assume that if one patient on a day holds in an operating room (OR), no other patient has a greater probability of holding in an OR. As we reviewed in the Journal of PeriAnesthesia Nursing, this assumption of statistical independence often is not satisfied.4 Studies of PACU hold generally should compare the percentages of days with at least one event of PACU hold.5 What conditions for the authors’ study resulted in assurances of statistical independence among patients? The authors used a convenience sample of 150 patients.1 Studies of PACU hold can use a sample size of days not patients because of statistical correlation between successive patients’ chance of PACU hold.6 For example, when we tested the effect of a decision support system on patients held in the OR, the analysis was by day.7 Being as the authors also performed a cohort study, following the STrengthening the Reporting of

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OBservational studies in Epidemiology (STROBE) checklist, how was their sample size chosen? Franklin Dexter, PhD, MD Division of Management Consulting Department of Anesthesia University of Iowa Iowa City, IA

References 1. Rice AN, Muckler VC, Miller WR, Vacchiano CA. Fasttracking ambulatory surgery patients following anesthesia. J Perianesth Nurs. 2015;30:124-133. 2. Dexter F, Macario A, Manberg PJ, Lubarsky DA. Computer simulation to determine how rapid anesthetic recovery protocols to decrease the time for emergence or increase the phase I post anesthesia care unit bypass rate affect staffing of an ambulatory surgery center. Anesth Analg. 1999;88:1053-1063. 3. Dexter F, Tinker JH. Analysis of strategies to decrease post anesthesia care unit costs. Anesthesiology. 1995;82:94-101. 4. Dexter F, Epstein RH, de Matta R, Marcon E. Strategies to reduce delays in admission into a postanesthesia care unit from operating rooms. J Perianesth Nurs. 2005;20:92-102. 5. Dexter F, Wachtel RE, Epstein RH. Impact of average patient acuity on staffing of the phase I PACU. J Perianesth Nurs. 2006;21:303-310. 6. Epstein RH, Dexter F, Traub RD. Statistical power analysis to estimate how many months of data are required to identify post anesthesia care unit staffing to minimize delays in admission from operating rooms. J Perianesth Nurs. 2002; 17:84-88. 7. Ehrenfeld JM, Dexter F, Rothman BS, et al. Lack of utility of a decision support system to mitigate delays in admission from the operating room to the post anesthesia care unit. Anesth Analg. 2013;117:1444-1452. http://dx.doi.org/10.1016/j.jopan.2015.05.009

Response to Letter to the Editor We appreciate Dr Dexter’s interest in our recent article, ‘‘Fast-Tracking Ambulatory Surgery Patients Following Anesthesia.’’ While his points are well taken, we believe they are out of context with respect to our approach to this work. This was not a randomized controlled trial; rather, it was a single institutional evaluation of a potential process improvement measure, ie, fast-tracking. The goal of this project was to examine a mechanism to improve the efficiency of our institution’s postoperative recovery process. As such, we were at liberty to select a convenience group of 75 patients in both the ‘‘reference’’ and ‘‘implementation’’ periods who were undergoing monitored

Journal of PeriAnesthesia Nursing, Vol 30, No 4 (August), 2015: pp 268-271