Rhomboid Intercostal and Subserratus Plane Block Versus Paravertebral Block for Thoracic Herpes Zoster: a Randomized Comparative Trial

This is a prospective, randomized, comparative, double-blinded (patient and clinician), superiority and non-inferiority clinical trial. This study compares the superiority and non-inferiority of RISS block versus PVB block for analgesia in the context of PHN. Patients were recruited from Baogang Hospital, Inner Mongolia. This study was approved by the Medical Ethics Committee of Baogang Hospital, Inner Mongolia (2023-MER-301) on December 19, 2023, and adhered to the Declaration of Helsinki and the Consolidated Standards of Reporting Trials (CONSORT) guidelines. All participants provided informed consent voluntarily.

Thirty patients with PHN, classified as ASA I-III, aged 44-82 years, and scheduled to receive either a RISS block or a PVB block between January 2024 and November 2024, were selected, with 15 patients per group. Inclusion criteria: Patients with typical manifestations of herpes zoster (HZ) , such as vesicular and painful rash; herpes zoster neuralgia lasting more than one month and unresponsive to conventional treatment; a VAS score ≥ 4; and thoracic nerve root involvement. Exclusion criteria: Patients who refused to provide written informed consent; were unable to cooperate with assessments; had a history of systemic autoimmune disease, organ transplantation, or cancer; had received other invasive treatments (e.g., spinal cord stimulation); had a central nervous system disorder; had coagulopathy; had a skin infection at the puncture site; or were pregnant/lactating.

Patients with PHN refractory to pharmacological treatment were considered for either RISS block or PVB block. All patients received famciclovir and gabapentin. Patients received standard antiviral treatment with famciclovir 500 mg three times daily for 7 days. Gabapentin was initiated at a dose of 300 mg/day, typically divided into three administrations. The dose was gradually increased to a maximum of 1800 mg/day as needed and tolerated. All procedures were performed in an outpatient operating room, and all participating physicians had undergone standardized training. Upon entry, electrocardiogram (ECG), blood pressure, and oxygen saturation were monitored. The patient is placed in the prone position with their arms abducted and internally rotated. Ultrasound equipment (SonoSite Edge II; Fujifilm SonoSite, Bothell, WA, USA) with a linear 13-6 MHz transducer (HFL50x; Fujifilm SonoSite, Bothell, WA, USA) was used. Each nerve block was performed by initially injecting a 5 mL test dose, observing for clinical signs of pain relief in the affected thoracic dermatome, and then injecting the remaining volume of medication after confirmation of the injection site. Patients received ultrasound-guided nerve blocks every 48 hours, for a total of three treatments.

Follow-up assessments were conducted at the pain clinic by two specially trained nurses who were blinded to patient allocation, at baseline (before therapy), on the day of treatment (Day 1), and at 7 days (Day 7), 30 days (Day 30), and 90 days (Day 90) post-treatment, either in person or via telephone.

Primary outcomes