The Incidence of Postoperative Respiratory Compromise May Not Be Reduced by Spinal Anesthesia

SESSION TITLE: Process Improvement in Obstructive Lung Disease Education, Pneumonia Readmissions and Rapid Response Systems II SESSION TYPE: Original Investigation Poster PRESENTED ON: Wednesday, October 28, 2015 at 01:30 PM - 02:30 PM PURPOSE: Respiratory complications during post-operative patient care pose significant risk. Surgical insult, residual effects of anesthesia and airway obstruction may potentially increase the risk for post-operative respiratory depression (PORD). Administration of opioids for pain management has been shown to decrease the respiratory drive and trigger opioid-induced respiratory depression (OIRD) in some patients. Traditionally, spinal anesthesia (SA) is associated with improved patient outcome and reduced post-operative complications, when compared to general anesthesia (GA). Here we used a non-invasive Respiratory Volume Monitor (RVM) to compare and contrast the incidence of PORD and OIRD in patients recovering from orthopedic surgery after GA versus SA. METHODS: Using a bio-impedance RVM (ExSpiron, Respiratory Motion, Waltham, MA) we collected respiratory data from 173 patients (mean age: 67.3, 44-89 years; mean BMI: 30, 19-49 kg/m2) undergoing elective joint replacement surgery with either GA (n=43) or SA (n=130). Respiratory depression was defined as sustained low minute ventilation (LMV) below 40% MVPRED, based on a standard Body Surface Area nomogram. PORD was defined as LMV sustained for at least 5 minutes at any point in the PACU and OIRD was defined as LMV sustained for at least two minutes within the 15 minutes following an initial opioid dose in the PACU. The incidences of PORD and OIRD were quantified and compared across GA and SA cohorts using two-sided Fisher exact tests. RESULTS: Patients were subdivided by whether they received opioids in the PACU. In the opioid sub-groups, the incidence of OIRD in the SA+opioid patients was marginally higher than in the GA+opioid (p=0.098). In the non-opioid sub-groups, the incidence of PORD was also significantly higher in the SA-opioid than GA-opioid patients (p=0.008). Overall, the incidence of respiratory depression was found to be significantly higher in SA patients (p=0.004). CONCLUSIONS: Our results show an increase in the relative risk for OIRD in patients receiving SA when compared to GA. This result is in direct contrast to the traditionally held notion that patients receiving SA generally have a decreased risk for respiratory complications. CLINICAL IMPLICATIONS: Our findings suggest that stratifying patients based on generalized assumptions can be potentially dangerous. Instead, clinicians could use the RVM technology, which provides objective respiratory monitoring, to develop individualized treatment plans and improve patient safety. DISCLOSURE: Christopher Voscopoulos: Shareholder: Small investor (<0.25%) in Respiratory Motion, Inc. Daniel Eversole: Employee: Employee of Respiratory Motion, Inc. The following authors have nothing to disclose: Davide Cattano, Edward George No Product/Research Disclosure Information