Intravenous regional anesthesia with clonidine in the management of complex regional pain syndrome of the knee

STUDY OBJECTIVE: To evaluate the safety and efficacy of administering intravenous regional anesthesia (IVRA) with clonidine in the management of complex regional pain syndrome (CRPS) of the knee. DESIGN: Prospective, non-blinded study. SETTING: University-affiliated pain management center. PATIENTS: 7 patients with the diagnosis of CRPS of the knee. The diagnosis of CRPS was made if a) patients had at least four of these symptoms: allodynia, hyperesthesia, edema, vasomotor changes, pain with a burning quality, sudomotor changes, joint stiffness, or temperature differences between extremities; b) patients had significant pain relief (>75%) after a lumbar sympathetic block. INTERVENTIONS: Each patient received IVRA with a solution containing clonidine 1 microg/kg in a total volume of 50 mL 0.5% lidocaine. IVRA clonidine (IVRA-C) was performed on each patient up to six times (maximum of once a week for six weeks). MEASUREMETNS: Pain was assessed using a verbal pain scale (VPS) between 0 and 10 before each IVRA-C treatment. Duration of pain relief was defined as the time during which the patients experienced no pain (VPS = 0). Continuous electrocardiogram (ECG) and pulse oximetry (SpO2) were monitored and blood pressure was recorded every 5 minutes for the first 60 minutes after tourniquet deflation. MAIN RESULTS: Five patients received complete pain relief with 4 to 6 IVRA-C blocks. The two remaining patients reached a therapeutic plateau from IVRA-C, but had persistent anatomic lesions contributing to the recurrence of their CRPS. No patient experienced hypotension (mean arterial pressure < or = 20% baseline), hypoxemia (SpO2 < or = 90%), bradycardia (heart rate < or =H 60 beats/min), or excessive sedation. CONCLUSIONS: IVRA-C is a useful treatment modality in the management of CRPS of the knee. Clonidine doses of 1 microg/kg appear to be well tolerated without significant side effects.