Healthcare and Medicine Reference
Figure 7.7 Step-by-step guide: lumbar puncture. (a) Sterilising the area
with 2% chlorhexidine solution. (b) Palpating the iliac crests to identify
landmarks. (c) Using a blue needle to infi ltrate local anaesthetic.
(d) Inserting an introducer needle. (e) Inserting the spinal needle through
the introducer. (f) CSF fl ashback through spinal needle. (g) Assistant
Identify the L3/L4 interspace (Figure 7.8) and raise a subcuta-
Insert the needle (or introducer if narrow-gauge needle used) at
neous wheal with 1% lidocaine using an orange (25G) or blue
(23G) needle. Inject a further 1-2 mL into the subcutaneous
space (Figure 7.7c). Allow time for the lidocaine to work.
With your non-dominant hand grip the spinous process of L3
90° to the skin in the midline at the middle to the cephalad end
of the interspace (Figure 7.7d,e). If a non-pencil point needle is
used insert with the bevel facing laterally (in the same direction
as the fi bres of the dura) so as to encourage parting of the dural
fi bres rather than cutting them. This decreases the risk of post-
dural puncture headache.
between thumb and index or middle fi nger. This anchors the
skin and allows easier identifi cation of the midline.