[Risk factors for postoperative hypoxemia during transport to the postanesthesia care unit and influence of transport monitoring : A retrospective propensity score-matched databank analysis]

Abstract

Background: Within a central operating room area, after general anesthesia (GA) patients are at risk of hypoxemia during transport to the postanesthesia care unit (PACU); however, specific risk factors have not been conclusively clarified and uniform recommendations for monitoring vital signs during transport within a central operating room area complex do not exist. The purpose of this retrospective database analysis was to identify risk factors for hypoxemia during this transport and to determine whether the use of transport monitoring (TM) affects the initial value of peripheral venous oxygen saturation (S_pO₂) in the PACU.

Material and methods: This analysis was performed on a retrospectively extracted dataset of procedures in GA within a central operating room area of a tertiary care hospital from 2015 to 2020. The emergence from GA was conducted in the operating room with subsequent transport to the PACU. The transport distance was between 31 and 72 m. Risk factors for initial hypoxemia in the PACU, defined as peripheral oxygen saturation (S_pO₂) below 90%, were determined using multivariate analysis. After splitting the dataset into patients without TM (group OM) and with TM (group MM) and propensity score matching, the influence of TM on initial S_pO₂ and the Aldrete score after arrival in the PACU were examined.

Results and discussion: From a total of 22,638 complete datasets included in the analysis, 8 risk factors for initial hypoxemia in PACU were identified: age > 65 years, body mass index (BMI) > 30 kg/m², chronic obstructive pulmonary disease (COPD), intraoperative airway driving pressure (∆p) > 15 mbar and positive endexpiratory pressure (PEEP) > 5 mbar, intraoperative administration of a long-acting opioids, first preoperative S_pO₂ < 97%, and last S_pO₂ < 97% measured after emergence from anesthesia before transport. At least 1 risk factor for postoperative hypoxemia was present in 90% of all patients. After propensity score matching, 3362 datasets per group remained for analysis of the influence of TM. Patients transported with TM revealed a higher S_pO₂ at PACU arrival (MM 97% [94; 99%], OM 96% [94; 99%], p < 0.001). In a subgroup analysis, this difference between groups remained in the presence of one or more risk factors (MM 97% [94; 99%], OM 96% [94; 98%], p < 0.001, n = 6044) but was not detectable in the absence of risk factors for hypoxemia (MM 97% [97; 100%], OM 99% [97; 100%], p < 0.393, n = 680). Furthermore, the goal of an Aldrete score > 8 at PACU arrival was achieved significantly more often in monitored patients (MM 2830 [83%], OM: 2665 [81%], p = 0.004). Critical hypoxemia (S_pO₂ < 90%) at PACU arrival had an overall low occurrence within propensity matched datasets and showed no difference between groups (MM: 161 [5%], OM 150 [5%], p = 0.755). According to these results, consistent use of TM leads to a higher S_pO₂ and Aldrete score at PACU arrival, even after a short transport distance within an operating room area. Consequently, it appears to be reasonable to avoid unmonitored transport after general anesthesia, even for short distances.

Keywords: Oxygen; Patient safety; Perioperative risk management; Postoperative complications; Pulse oximetry.