Ultrasound Blocks for the Anterior Abdominal Wall

42 | Ultrasound Blocks for the Anterior Abdominal Wall
difference between the subcostal TAPB and the classical TAPB is
the different extent of block.
Spread
The dermatomeric extent of the TAPB and its indications are
currently under discussion. It is not clear if the local anesthetic
blocks somatic nerves alone or if it also spreads to block
autonomic nerves. Radiological computerized tomography and
magnetic resonance imaging have evidenced the spread of local
anesthetic beyond the TAM plane to the quadratus lumborum
and to the intrathoracic paravertebral regions (Carney 2008,
McDonnell 2004).
The classical TAPB may not reliably provide analgesia for
procedures above the level of the umbilicus that is innervated by
T10 endings (Barrington 2009, Tran 2009). The extension is
generally from L1 to T10 (Carney 2008, McDonnell 2007 (2)).
However, a T7 to L1 extension has been also reported
(McDonnell 2007). The subcostal TAPB may produce a T9 to 11
block extent in more than 60% of cases (Lee 2008). In children,
ultrasound-guided supra-iliac TAPB with 0,2 ml/kg of anesthetic
performed by novice operators, produced lower abdominal
sensory blockade of only 3 to 4 dermatomes (Palmer 2011). Only
25% of TAP blocks may have upper abdominal block extension.
Thus, the optimal local anesthetic concentration, the duration of
effect and utility of these blocks in relation to peripheral and
neuraxial blockade in children needs clarification (Palmer 2011).
The clinical application of the transverse abdominal plexus
block may be divided between lower abdominal surgery, where
the classical posterior approach guarantees an adequate
analgesic coverage, and surgery in the upper quadrants of the
abdomen, where the subcostal TAPB is preferable to ensure an
adequate analgesia (McDonnell 2007 (3), Niraj 2009 (2), Hebbard
2010). A combination of the classical and subcostal approach
have been also described.