To the Editor:
An introducer needle is often used as a means of stabilizing subsequent placement of a small-gauge needle during spinal anesthesia. Commercially available kits that include 25-gauge needles (or smaller) usually include an 18- or 20-gauge short (1–1.5 in) needle that is placed into the interspinous space before placement of the spinal needle through it in an attempt to guide the smaller-gauge needle, which is likely to bend during insertion through soft tissue.
Obese patients can have a large amount of soft tissue overlying their interspinous ligaments, and the short introducer needle does not provide the desired level of stability and guidance for the subsequent placement of the very long (5.5–6.0 in) spinal needles that are often required to reach the dural sac.
We have found that in these cases, a standard 3.5-in, 20-gauge spinal needle (Quincke tip) can be used as an introducer for subsequent placement of longer 25- and 26-gauge needles, in effect steering the smaller gauge spinal needles through the supraspinous and interspinous ligaments.
Because risk of post–dural puncture headache increases with increased needle bore, care should be taken to avoid dural puncture with the 3.5-in, 20-gauge spinal needle. We use this technique when we are unable to identify the space with the shorter introducer and spinal needle because of insufficient needle length; therefore, the dural sac should be well past the tip of the 20-gauge needle.