Comparison of dexmedetomidine and ketamine for the analgesic effect using intravenous patient-controlled analgesia after gynecological abdominal surgery

provided the original work is properly cited. CC Intravenous patient-controlled analgesia (IV-PCA) using opioids allows the patient to control the amount of analgesic according to the degree of pain. For effective pain reduction and avoidance of opioid-related complications, studies have investigated methods of combining opioid use with drugs such as NSAIDs, ketamine, clonidine, and dexmedetomidine [1]. The highly selective α2-agonist dexmedetomidine is effective in sedating and reducing anxiety. In addition, because it retains a simultaneous analgesic effect, it is expected to be helpful in postoperative pain management [2]. The authors compared ketamine and dexmedetomidine, each in combination with fentanyl, in postoperative IV-PCA for patients scheduled for gynecological abdominal surgery. For each method, we examined the reduction in pain score and opioid consumption as well as whether it was effective in reducing opioid-related complications. After obtaining approval from the Institutional Review Board, and informed consent was obtained. Ninety patients (20 to 60 years, American Society of Anesthesiologists [ASA] physical status I-II) scheduled for gynecological abdominal surgery were divided into three groups: a control group (Group C: n = 30), a ketamine group (Group K: n = 30), and a dexmedetomidine group (Group D: n = 30). Near the end of surgery, all three groups were injected with fentanyl 0.5 μg/kg, ketorolac 30 mg, and ramosetron 0.3 mg for postoperative pain management. PCA was performed using IV-PCA equipment (AutoMed 3000, Ace Medical, Seoul, Korea). The pharmacological combinations for the three groups were as follows: fentanyl 20 μg/kg, ketorolac 180 mg, and ramosetron 0.6 mg for all three groups; normal saline for Group C; normal saline plus ketamine 40 mg for Group K; and normal saline plus dexmedetomidine (Precedex, Hospira, Rocky Mount, NC, USA) 500 μg for Group D. Each mixture was made in 100 ml solutions. The basal infusion rate was set at 2 ml/hr, the bolus at 2 ml, and the lockout time at 10 minutes. After the completion of surgery, patients were transferred to the ward. The IV-PCA consumption volume, pain score (VAS; visual analogue scale) and side effects were assessed at postoperative hours 1, 6, 12, 24, 36, and 48. When the patients required pain control, ketorolac 30 mg or tramadol 50 mg was administered. To treat nausea and vomiting, an IV injection of macperan 10 mg or ondansetron 4 mg was administered. If nausea and vomiting continued despite the administration of antiemetics or if the sedation score was more than 2, the IV-PCA background infusion rate and bolus were reduced by 0.4 ml, respectively. If respiration was inhibited (fewer than 8 breaths/ min), naloxone 0.1-0.4 mg was administered, and IV-PCA was discontinued until the respiration rate reached 9 breaths/min or higher. Data were analyzed using SAS 9.2 (SAS Institute Inc, Cary, NC, USA). One-way ANOVA was performed for the demographic data, and repeated measures ANOVA was performed for the between-group comparison of VAS pain scores, accumulated consumption of IV-PCA, accumulated consumption using bolus, and patient information. A P value of 0.05 or lower was considered statistically significant.