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Abstract
The transversus abdominis plane (TAP) block is a new regional anaesthesia technique
that provides analgesia after abdominal surgery. It involves injection of local anaesthetic
into the plane between the transversus abdominis and the internal oblique muscles.
The TAP block can be performed using a landmark technique through the lumbar triangle
or with ultrasound guidance. The goal of this anatomical study with dye injection
into the TAP and subsequent cadaver dissections was to establish the likely spread
of local anaesthesia in vivo and the segmental nerve involvement resulting from ultrasound-guided
TAP block.
An ultrasound-guided injection of aniline dye into the TAP was performed for each
hemi-abdominal wall of 10 unembalmed human cadavers and this was followed by dissection
to determine the extent of dye spread and nerve involvement in the dye injection.
After excluding one pilot specimen and one with advanced tissue decomposition, 16
hemi-abdominal walls were successfully injected and dissected. The lower thoracic
nerves (T10-T12) and first lumbar nerve (L1) were found emerging from posterior to
anterior between the costal margin and the iliac crest. Segmental nerves T10, T11,
T12, and L1 were involved in the dye in 50%, 100%, 100%, and 93% of cases, respectively.
This anatomical study shows that an ultrasound-guided TAP injection cephalad to the
iliac crest is likely to involve the T10-L1 nerve roots, and implies that the technique
may be limited to use in lower abdominal surgery.