Hypoventilation in the PACU is associated with hypoventilation in the surgical ward: Post-hoc analysis of a randomized clinical trial

Abstract

ObjectiveTo evaluate the association between early postoperative hypoventilation in the last hour of the post-anesthesia care unit (PACU) stay and hypoventilation during the rest of the first 48 postoperative hours in the surgical ward. DesignSub-analysis of a clinical trial. SettingPACU and surgical wards of a single medical center. PatientsAdults having abdominal surgery under general anesthesia. InterventionsMonitoring with a respiratory volume monitor from admission to PACU until the earlier of 48 h after surgery or discharge. MeasurementsThe exposure was having at least one low minute-ventilation (MV) event during the last hour of PACU stay, defined as MV lower than 40% the predicted value lasting at least 1 min. The primary outcome was low MV events lasting at least 2 min during the rest of the first 48 postoperative hours, while in the surgical ward. The secondary outcome was the rate of low MV events per monitored hour. Main resultsData of 292 patients were analyzed, of which 20 (6.8%) patients had a low MV event in PACU. Low MV events in the surgical ward were found in 81 (28%) patients. All patients who had low MV events in PACU had events again in the ward, while 61/272 (22%) had an event in the ward but not in PACU. The incidence rate of low MV events per hour was 24 (95% CI: 13, 46) among patients having an event in the PACU, and 2 (1, 4) among those who did not. ConclusionsIn adults recovering from abdominal surgery, events of hypoventilation during the first postoperative hour are associated with similar events during the rest of the first 48 postoperative hours, with positive predictive value approaching 100%. Sixty-one patients had ward hypoventilation that was not preceded by hypoventilation in PACU.