Peripheral nerve block injection pressure monitoring: A systematic review

To determine whether injection pressure and pressure-time characteristics can discriminate potentially hazardous needle-tip locations during peripheral nerve injection.

Systematic review of experimental preclinical studies with narrative synthesis.

Animal, ex vivo biological nerve, and human cadaver models of peripheral nerve injection.

Needle placement and injection at intraneural, intrafascicular, perineural, or extraneural locations.

CENTRAL, PubMed, Embase, and Web of Science were searched from inception to April 28, 2026 and updated on September 19, 2026. Studies reporting opening, peak, or plateau pressure or pressure-time characteristics in relation to anatomically defined needle-tip location were eligible. Human clinical studies and non-biological bench models were excluded. Risk of bias was evaluated using SYRCLE for animal studies and a domain-based framework for cadaveric studies. Because of substantial heterogeneity in experimental models, injection techniques, and pressure definitions, meta-analysis was not considered appropriate.

Twenty-eight studies met the inclusion criteria: 12 animal or animal ex vivo studies and 16 human cadaver studies. Intraneural injection was generally associated with higher peak and plateau pressures than perineural injection, but substantial overlap occurred across needle locations. Importantly, low pressure did not reliably rule out intraneural injection, while elevated pressure was also observed during needle-nerve contact and fascial injection. Consequently, the commonly proposed 15-psi threshold showed inconsistent sensitivity across experimental settings. Lower thresholds, including 12 psi, appeared more sensitive in some models but have not been clinically validated. Beyond absolute pressure values, the rate of pressure rise and pressure-time curve morphology showed potential for differentiating needle-tip locations.

Injection pressure monitoring may provide a nonspecific warning of needle placement within or against a poorly compliant structure. However, preclinical evidence alone cannot establish whether it should be used routinely or whether it reduces nerve injury. No universal pressure threshold or clinically recommended injection rate can currently be defined.