This study aims to evaluate whether adding dexmedetomidine to ropivacaine-based periarticular infiltration (PAI) improves postoperative pain control in patients undergoing total knee replacement (TKR). Despite standard pain management, many patients continue to experience moderate-to-severe pain after surgery. Dexmedetomidine, a sedative and analgesic agent, may help prolong the effect of local anaesthetics. A total of 60 patients will be randomly assigned to receive either ropivacaine alone or ropivacaine with dexmedetomidine. Pain scores, opioid use, side effects, and recovery time will be monitored for 24 hours. The goal is to determine if this method is more effective and safer for improving recovery after knee surgery.
Aged ≥18 years
Undergoing elective unilateral total knee replacement
ASA physical status I-III
No known allergy to local anaesthetics or dexmedetomidine
Known allergy to study drugs
Chronic pain or neurological conditions
Bilateral or revision TKR
Significant deformity affecting function
Single group
Ropivacaine + saline solution
Drug0.5% ropivacaine (19 mL) + 1 mL normal saline administered intraoperatively via periarticular injection.
Ropivacaine + Dexmedetomidine
Drug0.5% ropivacaine (19 mL) + dexmedetomidine 100 µg in 1 mL administered intraoperatively via periarticular injection.
24-hour postoperative pain score (NRS 0-10) at rest and during movement
Pain intensity will be assessed using the Numerical Rating Scale (NRS), where 0 indicates no pain and 10 indicates worst possible pain. Measurements will be taken at rest and during passive knee flexion to 90°, at 1, 6, 12, and 24 hours postoperatively. The primary endpoint is the NRS score at 24 hours.
Total postoperative opioid consumption (MME)
Total opioid use in the first 24 hours postoperatively will be recorded from the PCA pump. All opioids will be converted into morphine milligram equivalents (MME) for standardisation.
Patient satisfaction with pain management
Patient satisfaction will be measured on postoperative day 1 using a 5-point Likert scale, ranging from "very dissatisfied" to "very satisfied."
Incidence of adverse effects (sedation, bradycardia, hypotension, PONV)
Adverse effects will be monitored and recorded within 24 hours postoperatively: Sedation (RASS ≤ -2) Bradycardia (HR \< 50 bpm) Hypotension (MAP \< 65 mmHg or SBP \< 90 mmHg) PONV (score ≥1 on 0-4 scale)
Time to first ambulation
Time from skin closure to the patient's first unsupported ambulation (\>5 metres) will be recorded in hours.
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