Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, USA.
Anesth Analg. 2013 Aug;117(2):487-93. doi: 10.1213/ANE.0b013e31829772e9. Epub 2013 Jun 18.
Consider a case that has been ongoing for longer than the scheduled duration. The anesthesiologist estimates that there is 1 hour remaining. Forty-five minutes later the case has not yet finished, and closure has not yet started. We showed previously that the mean (expected) time remaining is approximately 1 hour, not 15 minutes. The relationship is a direct mathematical consequence of the log-normal probability distributions of operating room (OR) case durations. We test the hypothesis that, with an accurate probabilistic model, until closure begins the estimated mean time remaining would be the mean time from the start of closure to OR exit.
Among the 311,940 OR cases in a 7-year time series from 1 hospital, there were 3962 cases for which (1) there had been previously at least 30 cases of the same combination of scheduled procedure(s), surgeon, and type of anesthetic and (2) the actual OR time exceeded the 0.9 quantile of case duration before the case started. A Bayesian statistical method was used to calculate the mean (expected) minutes remaining in the case at the 0.9 quantile. The estimate was compared with the actual minutes from the time of the start of closure until the patient exited the OR.
The mean ± standard error of the pairwise difference was 0.2 ± 0.4 minutes. The Bayesian estimate for the 0.9 quantile was exceeded by 10.2% ± 0.01% of cases (i.e., very close to the desired 10.0% rate).
If a case is taking longer than the expected (scheduled) duration, closure has not yet started, and someone in the OR is asked how much time the case likely has remaining, the value recorded on a clipboard for viewing later should be the estimated time remaining (e.g., "1 hour") not an end time (e.g., "5:15 pm"). Electronic whiteboard displays should not show that the estimated time remaining in the case is less than the mean time from start of closure to OR exit. Similarly, if closure has started, the expected time remaining that is displayed should not be longer than the mean time from closure to OR exit. Finally, our results match previous reports that, before a case starts, statistical methods can reliably be used to assist in decisions involving the longest amount of time that cases may take (e.g., conflict checking for resources, filling holes in the OR schedule, and preventing holes in the schedule).
考虑一个持续时间超过预定时间的病例。麻醉师估计还剩 1 小时。45 分钟后，手术仍未结束，也尚未开始关闭。我们之前曾表明，剩余的平均（预期）时间约为 1 小时，而不是 15 分钟。这种关系是手术室（OR）手术持续时间的对数正态概率分布的直接数学结果。我们检验了以下假设：使用准确的概率模型，在开始关闭之前，估计的平均剩余时间将是从关闭开始到 OR 退出的平均时间。
在一家医院 7 年的时间序列中，有 311940 例 OR 病例，其中有 3962 例符合以下条件：（1）之前至少有 30 例相同的预定手术、外科医生和麻醉类型组合；（2）实际 OR 时间超过病例开始前病例持续时间的 0.9 分位数。使用贝叶斯统计方法计算病例在 0.9 分位数时的剩余平均（预期）分钟数。将估计值与从关闭开始到患者离开 OR 的实际分钟数进行比较。
配对差异的平均值±标准误差为 0.2±0.4 分钟。0.9 分位数的贝叶斯估计值超过了 10.2%±0.01%的病例（即非常接近所需的 10.0%率）。
如果一个病例的持续时间超过预期（预定）时间，关闭尚未开始，并且有人在 OR 中被问到该病例可能还剩下多少时间，稍后查看的剪贴板上记录的值应该是估计剩余时间（例如，“1 小时”），而不是结束时间（例如，“下午 5:15”）。电子白板显示不应显示该病例的剩余估计时间少于从关闭开始到 OR 退出的平均时间。同样，如果已经开始关闭，显示的预期剩余时间不应超过从关闭到 OR 退出的平均时间。最后，我们的结果与之前的报告一致，即在病例开始之前，可以使用统计方法可靠地协助做出涉及病例可能持续时间最长的决策（例如，资源冲突检查、填补 OR 时间表中的空白、以及防止时间表中的空白）。
