LUMBAR PUNCTUREPractical Procedures 483(ii) Ask the patient to flex the hips, knees and neck as much as they
can (i.e. fetal position).
(iii) Keep the back straight with the vertebral column parallel to the
edge of the bed, the shoulders square to the hips, and vertical.
Place a pillow between the knees to prevent rotation of the pelvis
by the upper leg.3 Determine the site of needle insertion:
(i) Palpate the iliac crest and locate the vertebra lying on an
imaginary line dropped from it (L4 vertebra).
(ii) Mark the two spaces above (L 3–4 space) and (L 2–3 space) with a
pen cap, or fingernail indent.
4 Use a no-touch, sterile gown-and-glove technique to prepare and drape the
site.
5 Anaesthetize the skin using the 25-gauge needle and s.c. infiltration. Then
use a 21-gauge needle for deeper infiltration down to the interspinous
ligament. Wait 2–3 min for full local anaesthetic effect.
6 Confirm that the stylet releases freely from within the LP needle, then orien-
tate bevel up and at 90° to the skin in all planes, and 5–10° cephalad (i.e.
needle tip pointing up to the head). Enter just above the lower vertebral
process in the intervertebral space (see Fig. 18.5).
Figure 18.5 Lumbar puncture.