Ultrasound predictors of peripheral nerve block failure after blast injury: a prospective cohort study

To determine the incidence and independent predictors of PNB failure in patients with blast-related limb trauma.

Study Design: Prospective observational cohort study conducted at a tertiary war trauma center from March 2023 to February 2026.
Participants: Adult patients undergoing ultrasound-guided PNB for blast-related limb injuries were included.
Primary Outcome: Primary block failure defined as failure to achieve ≥50% reduction in NRS pain score within 30 min and incomplete sensory blockade.
Secondary Outcome: Rescue opioid requirement within 6 h analyzed as a secondary indicator of analgesic burden.
Data Analysis: Multivariable logistic regression identified independent predictors of failure.

Overall block failure rate was 27.8%.
Anatomical distortion was present in 64% of cases.
Independent predictors of failure included vascular reconstruction (aOR 2.43, 95% CI 1.65–3.58), large hematoma (aOR 1.91, 95% CI 1.43–2.55), scar tissue/adhesions (aOR 1.74, 95% CI 1.29–2.33), fracture displacement (aOR 1.68, 95% CI 1.25–2.24), and Injury Severity Score > 25 (aOR 1.56, 95% CI 1.14–2.13).

Anatomical distortion following blast injury significantly increases the risk of PNB failure.

Study conducted in a single center, which may limit generalizability.
Exclusion of patients with pre-existing peripheral neuropathy or coagulopathy may affect results.