Clinical characteristics of commonly used spinal needles.

The important features which determine the ease of use of spinal needles include rapid detection of cerebrospinal fluid, minimal delay before injection and low resistance to injection of local anaesthetic. We investigated these three parameters among the following 11 spinal needles: Becton-Dickinson 22 G, 25 G and 27 G Whitacre, 25 G and 27 G Quincke; B. Braun Spinocan 22 G, 25 G and 26 G Quincke; Vygon 25 G Whitacre, Portex 26 G Pencil Point and the 24 G Sprotte. Three needles of each type were tested using an artificial cerebrospinal fluid model maintained at body temperature and at two hydrostatic pressures of 12 and 50 cm of water. The Becton Dickinson 27 G Whitacre has an immediate detection time at both pressure heights, a reasonably short 'ready to inject' time and relatively low resistance to injection, which, together with a reported low rate of postdural puncture headache, would indicate that it is the most appropriate for spinal anaesthesia. The 25 G Whitacre types would be the next most suitable to use.