Fluid flow through dural puncture sites. An in vitro comparison of needle point types.

Leakage of artificial cerebrospinal fluid through human dura was measured in vitro after puncture by spinal needles. Fluid loss tailed off in all cases and ceased within 5 minutes in 10% of punctures made with a 22-gauge needle, 28% made with a 26-gauge and 65% made with a 29-gauge needle (p less than 0.05). The fluid loss was not reduced by alignment of the level of the needle parallel to the longitudinal direction of the fibres. Whitacre point needles of 22 gauge produced lower fluid loss than a 22-gauge Quincke point needle inserted across the fibres (p less than 0.05). Leakage rate was related to needle size, but not related to the alignment of a Quincke point. Little or no leakage occurred with 29-gauge needles.