The effect of Dexmedetomidine-Remifentanil-combined infusions on perioperative hemodynamics, postoperative pain and cognitive functions in major orthopedic surgery

Total knee and total hip arthroplasties are among the most common orthopedic surgical procedures. With the increasing average age in society, these surgeries are becoming more prevalent. In elderly patients with hip fractures, delirium and cognitive dysfunction are common postoperative complications. Postoperative pain is a significant concern due to its impact on both quality of life and postoperative cognitive function. In today's practice, multimodal analgesia studies are emphasized, avoiding the use of opioid agents. The use of dexmedetomidine has been reported to have some positive effects on postoperative pain and cognitive function. In this study, we aimed to investigate the effects of intraoperative dexmedetomidine infusion alone and in combination with low-dose opioids on postoperative pain and cognitive dysfunction in high-risk patients aged 65 and over undergoing major orthopedic surgery. A total of 72 patients aged 65 and over undergoing major orthopedic surgery were randomized into three equal groups: dexmedetomidine, remifentanil, and a combination of dexmedetomidine and remifentanil. The dexmedetomidine group received an infusion of dexmedetomidine at a rate of 0.5 µg/kg/h, the remifentanil group received an infusion of remifentanil at a rate of 1 µg/kg/h, and the combination group received an infusion of remifentanil at a rate of 0.5 µg/kg/h and dexmedetomidine at a rate of 0.25 µg/kg/h. All patients received sevoflurane inhalation anesthesia, and the anesthetic depth was monitored between BIS 40-60. At the end of the surgery, all patients received 1 gram of paracetamol and 50 mg of dexketoprofen for analgesia. Intraoperative hemodynamics of patients were monitored. Postoperative pain status was evaluated with a numeric pain score at 2, 4, 8, 12, and 24 hours after the surgery. If the numeric pain score of patients was between 4-6, 1 gram of paracetamol was administered initially. If the pain score persisted between 4-6 after one hour, 50 mg of dexketoprofen was administered. Patients with a pain score of 6 and above received 100 mg of tramadol. The cognitive functions of patients were evaluated with a mini-mental test 4 hours before the surgery and 24 hours after the surgery. Demographic data, comorbidities, and hemodynamic parameters were similar among the groups. There was a statistically significant reduction in the need for non-opioid analgesics (P=0.012) and tramadol (P=0.002) in the dexmedetomidine group. Numeric pain scores at the fourth hour showed a significant difference among the groups (P=0.008), with the highest average numeric pain score in the remifentanil group and the lowest score in the dexmedetomidine group. Postoperative cognitive functions were similar among the groups. Mini-mental test scores for all groups were lower postoperatively compared to preoperative scores. In conclusion, the use of dexmedetomidine in the intraoperative period in patients undergoing major orthopedic surgery can reduce postoperative pain without affecting hemodynamics compared to the standard opioid-based anesthetic approach and the combination of low-dose remifentanil and dexmedetomidine, without affecting postoperative cognitive functions. Keywords: Postoperative pain, postoperative cognitive dysfunction, dexmedetomidine, remifentanil, tramadol.