Evaluation of Analgesic Effects of Ketamine versus Dexmedetomidine as an Adjuvant to 0.2% Ropivacaine Infusion in Adductor Canal Block for Postoperative Analgesia following Unilateral Total Knee Replacement Surgery.

BACKGROUND

Postoperative pain management is critical for recovery following total knee replacement (TKR). Significant pain following surgery is linked to TKR, and this discomfort might have a negative impact on the patient's satisfaction, length of stay, and functional recovery. The adductor canal block (ACB) is preferred for its motor-sparing properties. This study compared the analgesic efficacy of ketamine and dexmedetomidine as adjuvants to ropivacaine infusion in ACB for patients undergoing unilateral TKR.

METHODS

In this prospective, randomized, comparative study, 44 patients (American Society of Anesthesiologists I-III) were divided into two equal groups. All received spinal anesthesia followed by an ultrasound-guided ACB with a catheter. Group A received 0.2% ropivacaine with ketamine (1 mg/kg) infusion, and Group B received 0.2% ropivacaine with dexmedetomidine (1 μg/kg) infusion at 8-10 mL/h for 24 h. Primary outcomes included a comparison of the requirement for rescue analgesia, while secondary outcomes included a comparison of pain scores, hemodynamic stability, and motor blockade.

RESULTS

The requirement for rescue analgesia was significantly higher in Group A (54.54%) compared to Group B (18.2%; P = 0.012). While numerical pain scores were generally comparable, Group B showed significantly lower pain at the 8th h (P = 0.045). Both groups maintained hemodynamic stability and demonstrated preserved motor power. Postoperative vomiting was significantly more frequent in Group A (P = 0.035).

CONCLUSION

Dexmedetomidine (1 μg/kg) is a more effective adjuvant than ketamine (1 mg/kg) for ropivacaine-based ACB, offering improved analgesia without adverse hemodynamic or motor effects.