Risk factors for respiratory depression and its effect on postoperative pulmonary complications in the PACU: A prospective cohort study

Background Respiratory depression (RD) is a frequent postoperative complication in the post-anesthesia care unit (PACU). This prospective cohort study investigated the risk factors for RD and examined its impact on postoperative pulmonary complications (PPCs). Methods Data were collected from June 2022 to August 2023 at a tertiary care Centre. Patients were assigned to RD or non-RD groups based on the occurrence of RD in the PACU, defined as SpO₂ < 90%, respiratory rate < 8/min, apnea ≥ 10 s, or analgesia-sedation mismatch. The primary objective was to identify risk factors for RD in the PACU. Secondary outcomes included the incidence of RD and its effect on PPCs. Results RD was observed in 152 patients (17.4%). Multivariate logistic regression analysis revealed that age ( p  = 0.034), American Society of Anesthesiologists (ASA) III classification (P = 0.006), preoperative lung disease ( p  < 0.001), preoperative hypoxemia (P = 0.044), preoperative hypercapnia ( p  = 0.03), intraoperative hypothermia ( p  < 0.001) and PACU rescue opioid analgesics ( p  < 0.001) were independent risk factors for RD in the PACU. RD in the PACU was significantly associated with an increased incidence of PPCs (OR = 3.81, 95%CI 1.07 to 13.57, p  = 0.044), postoperative pneumonia (OR = 3.00, 95%CI 1.15 to 7.8, p  = 0.024), unplanned transfer to ICU (OR = 3.81, 95%CI 1.07 to 13.57, p  = 0.039) and prolonged hospital stay (OR = 1.04, 95%CI 1.01 to 1.09, p  = 0.033). Conclusion Age, ASA III classification, pre-existing pulmonary disease, hypoxemia, hypercapnia, intraoperative hypothermia, and rescue opioid use in the PACU are independent risk factors for RD. RD in the PACU is associated with increased risk of PPCs and other adverse postoperative outcomes. Trial registry: Chinese Clinical Trial Registry ChiCTR2200061256. Registered on 18 June, 2022.