Percentages of Cases in Operating Rooms of Sufficient Duration to Accommodate a 30-Minute Breast Milk Pumping Session by Anesthesia Residents or Nurse Anesthetists

Abstract

Introduction: Accommodating breast milk pumping sessions is required by US federal statute, but fulfillment is challenging for US anesthesia providers (e.g., anesthesia residents and nurse anesthetists). Considerations of good anesthesia practices (e.g., being present for critical portions of cases, including induction and emergence) create limits on which procedures are suitable for such relief. Our objective was to quantify the minimum percentages of cases for which there could reliably (≥ 95%) be at least 30 minutes during the surgical time when the anesthesia provider could receive such breaks.

Methods: We studied all surgical cases performed at an anesthesia department over four years, including its inpatient surgical suite, pediatric hospital, and ambulatory surgery center. The 5% lower prediction bounds of surgical times (surgery or procedure start to end) were calculated from three years of historical data (October 1, 2016, to September 30, 2019) based on two-parameter lognormal distributions. The prediction bounds were compared to actual surgical start times during the next one year (October 1, 2019, to September 30, 2020). We considered the interval available for a breast milk pumping session during a case to be from 15 minutes after the start of the surgical time (to allow completion of initial documentation, other activities, and hand-off to the relieving anesthesia provider) until the end of the surgical time.

Results: The lower prediction bounds were accurate, with 4.9% (4.6% - 5.2%) of future cases' surgical times being briefer, matching the nominal 5.0% rate. Applying these bounds, approximately 39% of cases (99% confidence interval 39% - 40%) were reliably of sufficient duration for the anesthesia provider delivering care in that one operating room to receive a 30-minute break for breast milk pumping session between 15 minutes after the start of surgery and procedure end. This percentage (39%) was substantially less than the 72% of the surgical times that were observed, in retrospect, to be sufficiently long because the lower 5% prediction bounds accounted correctly for the uncertainty in the duration of each case. The observed 39% prevalence was significantly fewer than half the cases (P < 0.0001 vs. 50%) suitable for such relief.

Conclusions: Individuals making operating room assignments for anesthesia providers need to consider the 5% lower prediction bounds of surgical times for cases in the room when making such assignments for women who require time for breast milk pumping sessions. Such considerations will generally result in assignments to rooms with one or more long-duration cases. Such a strategy may involve changes in preferred assignments for the anesthesia providers and alteration in the order of rotations for anesthesia residents (e.g., palliative care rotation rather than transition to practice at a pediatric ambulatory surgery center). When making room assignments for anesthesia providers who are breastfeeding, our results show that the 5% lower prediction bounds of surgical times need to be calculated; relying on the average surgical times for procedures is insufficient. Our paper also shows how to perform the mathematics using a spreadsheet program or equivalent.

Keywords: academic medical centers/organization and administration; breastfeeding; lactation; postnatal care.

Figure 1. Cumulative Distribution Functions for Surgical Times

Cumulative distribution functions for surgical times of Healthcare Common Procedure Coding System 55866, “Laparoscopy, surgical prostatectomy, retropubic radical, including nerve sparing, includes robotic assistance.” The blue line shows the left side of the fitted lognormal distribution curve from Figure 2. The red line shows the exponential of the Student t-distribution curve based on N = 3 cases, using the same parameter estimates (mean and standard deviation in the log scale) as for the blue line. Among the 2596 procedures during the 1-year contemporaneous period, there were N ≤ 3 cases from the 3-year historical period for 26% (673/2596) of the procedures. Both lines have the same median of 274 minutes (i.e., the lines intersect at the cumulative percentage of 50%), because the median in the arithmetic time scale is the exponential of the mean in the log scale. Whereas the 5th percentile of the lognormal distribution is 176 minutes, the 5% lower prediction bound calculated using the Student t-distribution is 175 minutes for N = 99 historical data versus 124 minutes for N = 3 historical data. The 5% lower prediction bound with only N = 3 historical cases is much less because there is considerable uncertainty in the estimated mean and standard deviation.

Figure 2. Distribution of Surgical Times

Surgical times of the most recent 99 cases comprising the historical period for Healthcare Common Procedure Coding System 55866, “Laparoscopy, surgical prostatectomy, retropubic radical, including nerve sparing, includes robotic assistance.” From the 3-year historical period, there were 3478 other procedures performed among the 95,146 cases. The Shapiro-Wilk test applied to the logarithm of duration shows an excellent fit to a normal distribution, P = 0.84. (A) Histogram in log scale, along with a superimposed normal density plot. (B) Normal quantile plot, along with the reference line.