Dexmedetomidine added to an opioid-based analgesic regimen for the prevention of postoperative nausea and vomiting in highly susceptible patients

BACKGROUND Dexmedetomidine, an α2 adrenergic receptor agonist, has analgesic, sedative and sympatholytic properties, with a lack of respiratory depression. It is licensed only for intensive care sedation. OBJECTIVE The objective of this study is to investigate whether intravenous (i.v.) patient-controlled analgesia (PCA) with dexmedetomidine added to a fentanyl-based drug mixture could reduce postoperative nausea and vomiting (PONV) in highly susceptible patients undergoing lumbar spinal surgery. DESIGN A randomised, double-blinded study. SETTING At a tertiary university hospital between September 2012 and September 2013. PATIENTS One hundred and eight patients undergoing level 1 or 2 posterior lumbar spinal fusion who had at least three risk factors for PONV (female, nonsmoker, use of postoperative opioids) were randomised into two groups. Three patients were excluded from analysis and 105 patients completed the study. METHODS Patients received either dexmedetomidine 0.5μgkg-1 i.v. (dexmedetomidine group) or 0.9% normal saline (control group) 30min before the completion of surgery followed by fentanyl 0.5μgkg-1 and 4mg ondansetron. Postoperatively, the PCA (fentanyl 10μgkg-1 with 120mg ketorolac, with or without dexmedetomidine 10μgkg-1 made up to a total volume of 100ml) was programmed to deliver 1ml bolus (lockout 15min) with a continuous background infusion of 2mlh-1. The PCA was used for the first 48h postoperatively. MAIN OUTCOME MEASURES The incidence and severity of PONV, cumulative dose of PCA fentanyl consumed and pain scores were assessed for 48h. RESULTS The dexmedetomidine group experienced less nausea during the time interval 1 to 3h postoperatively compared with the control group [odds ratio (OR) 0.32; 95% confidence interval (CI) 0.13 to 0.77; P=0.019]. The intensity of nausea between the groups during the first 48h was comparable, but the dexmedetomidine group had a lower incidence of moderate to severe nausea (OR 0.28; 95% CI 0.12 to 0.67; P< 0.003). Pain scores were not significantly different between the groups, but patients in the dexmedetomidine group required less fentanyl and less rescue analgesia in the first 12h. Compared with the control group, patients in the dexmedetomidine group experienced almost twice as many episodes of hypotension and bradycardia, but this failed to reach statistical significance. CONCLUSION Adding dexmedetomidine to a fentanyl-based PCA drug mixture reduces the frequency and severity of acute postoperative nausea in highly susceptible patients. TRIAL REGISTRATION Clinicaltrials.gov identifier: NCT01840254.