Ultrasound guided intercostal nerve block using pulsed radiofrequency in management of thoracic postherpetic neuralgia

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This randomized blind clinical trial will be carried out at Mansoura University Hospital. Sample size calculation will be based on the previous studies which reported the mean VAS for PHN patients was 65 and the assumed standard deviation (SD) was 20 and reduction of VAS by 20 will be a clinically significant improvement with a power of study 90% (alpha equal 0.05, Beta equal 0.1). The calculated sample size of 21 patients in each group.The total number of the calculated sample size will be 42 patients. The number will increase by 20% to compensate for possible dropouts. Therefore, the total sample size will be 50 patients (25 patient in each group). In the first visit to pain clinic, after taking medical history and thorough clinical examination, the severity of pain will be evaluated using VAS. Patient quality of life will be assessed using self-evaluation questionnaires (SF-36) Inclusion criteria: Adult patients who had chest wall PHN at T2-T11 of more than 6 months duration, who had moderate and severe pain (VAS more than 30 mm). Exclusion Criteria: patient refusal, patients with mild pain,Presence of psychiatric illness. and infection at site of injection. Patients with history of renal, hepatic diseases, coagulopathy, diabetes, steroid therapy, malignancies and patients taking chemo and/or radiotherapy will be excluded Randomization will be performed using sealed envelopes indicating the group to which patients will be assigned. A blinded chief nurse who will not be involved in the study or in the data collection will read the number contained in the envelope and make group assignment. The affected thoracic dermatome first will be determined. In addition to the affected dermatome, one dermatome above and below will be the therapeutic targets of this study. Ultrasound guided localization of targets (ICN at the angulus costae) then sensory stimulation of the nerve roots with paraasthesia response in the dermatome distribution of the affected nerve root using (Neurotherm Rediofrequancy machine 1100 at 50 HZ using a 22-gauge 10 cm radiofrequency needle with 5 mm active tip) for both group. Group 1(25 patients): after sensory stimulation patients will receive 1 ml xylocaine 2%locally for each nerve root and wait for one minute. Then the patients will receive 2 cycles PRF 42 C for 120 second for ICN at the angulus costae for the affected thoracic nerves. Group 2(25 patients): after sensory stimulation patients will receive 1 ml xylocaine 2%locally for each nerve root and we will spend same time taken for pulsed radiofrequency cycles to occure at the angulus costae for each affected thoracic nerves. These therapeutic modalities will be applied to the affected dermatome and to adjacent upper and lower one in all patients in both groups. All patients will receive pregabalin in a dose of 150 mg twice daily. Their pain score will be evaluated in each visit. Once patients reported mild pain (VAS less than 30), the pregabalin dose will be reduced by 75 mg every 3 days provided that pain score remained less than 30 with each reduction. If the VAS value will increase to more than 30, the patient will be returned to the last controllable pregabalin dose and the result will be recorded in the patient diary. Acetaminophen will be available as rescue analgesia in a dose of 1,000 mg on request. For those with persistent pain more than 30, a maximum daily dose of 4,000 mg will be allowed. Blinding (masking) Patients preparation for interventional procedures and ensure fulfillment of inclusion and exclusion criteria will be performed by Dr. Salma El Sayed. The same investigator (Dr. Salma El Sayed under supervision of Dr. Mohamed Makharita and Dr. Mahmoud Abdel Latif) will perform all interventional procedures for all patients. Follow ups and reporting of the data will be performed by an investigator from the pain clinic who will be unaware of the randomization procedure and the type of intervention to which the patients was subjected. Data collection from the patient files will be by Dr. Salma El Sayed. Evaluation Parameters: Patients will be evaluated for pain severity using Visual Analogue Scale (VAS), (100 mm unmarked line in which 0 equal no pain and 100 mm means worst pain imaginable) before the block (basal), , every 2 weeks after the procedure for 6 months and every 1 month for another 6 months. If VAS less than 30 mm gradual reduction of medication will be allowed. Follow up At each assessment visit, VAS, duration of pain relief and the total analgesic consumption will be recorded. Quality of life will be evaluated using self-evaluation questionnaires (SF-36) at 1, 3, 6 and 12 months. Adverse effects include vasovagal attack, pneumothorax, neuritis and any sensory or motor deficits will be also reported. Telephone consultations were allowed if any increase in pain occurred during follow up.

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