Effects of Intravenous Dexmedetomidine Versus Lidocaine on Postoperative Pain, Analgesic Consumption and Functional Recovery After Abdominal Gynecological Surgery: A Randomized Placebo-controlled Double Blind Study.

BACKGROUND The management of acute postoperative pain remains challenging, and the search for adjuvants to reduce opioid use continues. OBJECTIVES We studied the effect of intravenous dexmedetomidine and lidocaine on postoperative pain, opioid consumption, and functional recovery. STUDY DESIGN A randomized controlled trial was performed. SETTING The trial was conducted at Aretaieio University Hospital, Athens, Greece. METHODS In this double-blind study, 91 women, 30-70 years old, with an American Society of Anesthesiologists Physical Status of I or II, scheduled for abdominal hysterectomy or myomectomy, were randomized to receive either dexmedetomidine (DEX group), lidocaine (LIDO group), or placebo (CONTROL group). Before anesthesia induction, a loading intravenous dose of one of the aforementioned drugs was given to all patients (0.9mL/kg/h for 10 minutes), followed by 0.15mL/kg/h infusion until the last suture. Identical 50 mL syringes containing dexmedetomidine 4 mg/mL (bolus: 0.6 µg/kg, infusion: 0.6 µg/kg/h), or lidocaine 10 mg/mL (bolus: 1.5 mg/kg, infusion: 1.5 mg/kg/ h), or NaCl 0.9% were used. The main outcomes were cumulative morphine consumption and postoperative pain at rest and cough (Numeric Rating Scale, [NRS]: 0-10). Other measurements included anesthetic (sevoflurane) consumption, nausea/vomiting, postoperative sedation, time to first passage of flatus/stool, mobilization, sleep quality, satisfaction, discharge time, and drug side effects. Measurements were performed at Post-anesthesia Care Unit (PACU), 2 hours, 4 hours, 8 hours, 24 hours, and 48 hours. RESULTS Data from 81 patients were analyzed (DEX group:26, LIDO group:29, CONTROL group:26). Cumulative morphine consumption (mg) was significantly lower in the LIDO group versus the CONTROL group in the PACU (LIDO group: 8.41 ± 1.45, CONTROL group: 10.4 ± 3.29, P = 0.017); at 24 hours (LIDO group: 16.86 ± 5.85, CONTROL group: 23.4 ± 9.54, P = 0.036); and 48 hours (LIDO group: 20.45 ± 6.58, CONTROL group: 28.87 ± 12.55, P = 0.022). The DEX group experienced significantly less nausea compared to the CONTROL group in the PACU (P = 0.041). Finally, the use of vasoconstrictors was higher in the treatment groups, especially in the DEX group compared to the CONTROL group (P = 0.012). The rest of the measurements regarding NRS scores, sevoflurane consumption, bowel function, and other recovery characteristics, satisfaction, discharge time, and drug side effects did not differ significantly among the groups. LIMITATIONS Different doses of the studied medications were not assessed, drugs were administered only pre- and intraoperatively, and pain was not managed according to the World Health Organization (WHO) pain relief ladder. However, all patients were adequately covered with patient-controlled anesthesia morphine and acetaminophen; parecoxib (not approved for use in the United States) was preserved as a rescue analgesic. CONCLUSIONS Dexmedetomidine and lidocaine could be useful adjuvants for analgesia after abdominal surgery. Lidocaine significantly reduced postoperative opioid consumption, while dexmedetomidine prevented early postoperative nausea. However, hypotension and the need for vasopressors was common with both agents, especially with dexmedetomidine.