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The Effect of Erector Spinae Plane Blockade on Prevention of Postherpetic Neuralgia in Elderly Patients: A Randomized Double-blind Placebo-controlled Trial.

BACKGROUND
Postherpetic neuralgia (PHN) is the most common chronic complication following the onset of herpes zoster (HZ). Both the incidence of HZ and the proportion of patients with HZ who develop PHN rise with age. Ultrasound-guided erector spinae plane blockade (ESPB) has been reported to relieve neuropathic pain and PHN in elderly patients, but no randomized controlled trials have been conducted regarding the effect of ESPB on elderly patients with HZ in the acute or subacute phases.


OBJECTIVES
To evaluate the effect of repeated ESPB on the occurrence of PHN in elderly patients with acute or  subacute HZ.


STUDY DESIGN
A randomized double blind placebo-controlled trial with 2 parallel groups.


SETTING
A university hospital in China.


METHODS
Patients diagnosed with acute or subacute HZ were randomized to receive either ultrasound-guided ESPB (the ESPB group) or placebo subcutaneous injection (the control group) every 24 hours for 3 days. Patients were followed up at 12 weeks after the final treatment. The primary end point was the incidence of PHN at 12 weeks.


RESULTS
A total of 52 patients were enrolled and randomized; 50 completed 12 weeks of follow-up. The incidence of PHN at 12 weeks was significantly lower in the ESPB group (15.4% [4/26]) than in the control group (41.7% [10/24]); relative risk 0.37, 95% confidence interval 0.13-1.02, P = 0.039. At 12 weeks, the VAS scores at rest and the total scores from the Short-Form McGill Pain Questionnaire-2 were significantly decreased in the ESPB group (P = 0.046 and P = 0.001, respectively). The incidence of neuropathic pain, sleep disturbance, and anxiety/depression were significantly reduced in the ESPB group (P = 0.002, P = 0.002, and P = 0.025, respectively). Patients using tramadol and hypnotics as well as total complications with oral medicines were remarkably decreased in the ESPB group (P = 0.008, P = 0.002, and P = 0.042 respectively). The adverse events during or after the procedure were comparable between the groups.


LIMITATIONS
This trial was carried out in a single center with a 12-week follow-up. Nearly 8% of patients in the control group were lost to follow-up.


CONCLUSIONS
For elderly patients suffering acute or subacute HZ, ESPB reduces the incidence of PHN at 12 weeks after treatment; it also decreases the occurrence of neuropathic pain, sleep disturbance, and anxiety/depression.