Needle insertion forces and fluid injection pressures during targeting of nerves in a soft embalmed cadaver model.

Pressure was greater at epineurium and within subepineurium than perineural tissue, geometric ratio (95% CI) 4.7 (3.0-7.3) kPa and 3.8 (2.5-5.7) kPa, respectively, both P < 0.0001. Force on nerve contact and on nerve penetration was greater than force in perineural tissue, geometric ratios (95% CI) 3.0 (1.9-4.7) N and 3.6 (2.2-7.5) N, respectively, both P < 0.0001. On nerve contact, 1 in 6 insertions were ≥ 5 N CONCLUSIONS: Despite valid infusion pressures, anaesthetists exerted excessive force on nerves.