Abstract

Sub-neurolytic dose of phenol for popliteal-sciatic nerve block under ultrasound guidance for the relief of ischemic leg pain

Author(s):Vergheese Davies C., Valiaveedan S., Thomas Mariam K., Aftab S. and Thomas T.

Ischemic leg pain is often intractable. Pain relief with conventional analgesics, opioids and non-opioids is often unsatisfactory. It provides only a sub-optimal pain relief in spite of the grievous side effects it causes with the heavy dose required. Interventional procedures like surgical or chemical lumbar sympathectomy also not rewarding. Sciatic nerve can be easily visualized and blocked under ultrasound guidance in the popliteal fossa. Phenol causes temporary axonal demyelination and disruption interrupting nerve conduction. At a low concentration of less than 4% Phenol is reported to have a differential effect disrupting predominantly the pain fibers, retaining the other sensory functions and motor power. This provides sufficient analgesia for 3-6 months. To assess the analgesic efficacy of sub-neurolytic dose of phenol in chronic ischemic leg pain. 43 patients who had chronic leg pain due to ischemic etiology were included in the study after obtaining informed and written consent. Pre-procedural pain was rated using Numerical Rating Scale (NRS). Sciatic nerve in the popliteal fossa was blocked under ultrasound guidance with 3% Phenol in 0.5% Ropivacaine. Pain was rated everyday for first seven days and weekly thereafter for the next 6 months using NRS. Rescue analgesia was offered in the form of oral Paracetamol and Tramadol combination tablets on an ‘as and when required’ basis. Oral Pregabalin was specially planned to be prescribed to control unbearable or neuropathic pain. Post-procedural pain scores were significantly lower as compared to preprocedural score in all patients for the entire study period (p < 0.01). Sub-neurolytic dose of phenol causes significant reduction in pain scores in an ischemic limb for 6 months, the period of study.

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