Effect of Repeated Paravertebral Injections with Local Anesthetics and Steroids on Prevention of Post-herpetic Neuralgia

Abstract

Background The usefulness of early sympathetic blockade in the prevention of postherpetic neuralgia (PHN) has been reported. However, the optimal duration and frequency of paravertebral blocks that prevent or maximally reduce the incidence of PHN need to be clarified. Objectives To assess the impact of weekly separated 2 versus 3 paravertebral injections using local anesthetic and steroids, early in the course of acute thoracic herpes zoster, on the incidence of postherpetic neuralgia. Study design Randomized single-blind study. Setting University hospitals. Methods Eighty patients suffering from acute thoracic herpes zoster eruption were randomly allocated into 2 groups. Group I received paravertebral block using 25 mg bupivacaine plus 8 mg dexamethasone in a total volume of 10 mL twice one week apart. Group II received paravertebral block using 25 mg bupivacaine plus 8 mg dexamethasone in a total volume of 10 mL 3 times one week apart. All patients received daily 300 mg pregabalin in divided doses (150 mg/12 hours). Pain scores were evaluated during each visit. Once the patient reported mild pain, the trial for reducing the pregabalin dose was done. Acetaminophen was available as a rescue analgesia. At each assessment visit, the total analgesic consumption was recorded. The times of the complete resolution of the pain and the skin eruption were recorded. The incidence of PHN after 3, 6, and 12 months was also reported. Results Pre-eruptive pain severity and duration were comparable between both groups. There was no statistically significant difference between both groups with respect to the day of the block, the total duration of pain until the first block, and eruptive and herpetic pain duration parameters. The severity of skin lesions was comparable among both groups. Four patients (10.5%) had PHN in group I versus 3 patients (8.1%) in group II after 3 months of follow-up. Meanwhile, these numbers were 3 patients (7.9%) and 2 patients (5.4%) at 6 and 12 months in both groups, respectively. Compared with basal parameters, effective pain control was noticed in both groups with no significant difference between groups. Limitations Small size, lack of complete blindness, and the use of fluoroscopy in block performance in the era of performing this block under ultrasound. Conclusions Repeated paravertebral blocks using local anesthetic and steroids weekly over 2 or 3 weeks in the management of acute thoracic herpes zoster can provide safe and effective pain relief and minimize the incidence of PHN. However, no added benefit was detected from repeated blocks more than twice.