Ultrasound Blocks for the Anterior Abdominal Wall

4. Iliohypogastric and Ilioinguinal Nerve Block | 47
experienced hands or when multiple punctures are performed
because of the high anatomical and landmark variability
(Randhawa 2010). The failure rate may be as high as 6 to 40%
especially in infants and children, even when the nerve is
exposed at surgery (Weintraud 2008, Lim 2002). Correct
administration of local anesthetic around the target nerves
occurred in only 14% and 57% of cases in two studies when using
a landmark method with a fascial click (Weintraud 2008,
Randhawa 2010). The remainder of the injections were deposited
in adjacent anatomical structures (iliac muscle 18%, TAM 26%,
IOM 29%, EOM 9%, subcutaneous tissue 2%, and peritoneum 2%)
(Weintraud 2008).
The data in Table 4.1 show the distances from the skin and the
ASIS to the nerves and from the nerves to the peritoneum in
children. Table 4.2 show the abdominal muscle size in adults.
Table 4.2 – Adult distances in centimeters (modified from
Eichenberger 2006 and Rankin 2006).
Adults
Absolute abdominal muscle size at the
mid-axillary line
Males 3.86 (right: 0.64, 95% range 2.58–5.14) 0.4–1.1
3.88 (left: 0.67, 95% range 2.54–5.22)
Females 2.96 (right: 0.46, 95% range 2.04–3.88) 0.4–1.1
2.94 (left: 0.43, 95% range 2.08–3.80)
IIN to bone distance
at the ASIS
These data highlight the fact that blind techniques may be
imprecise and carry a high risk of bowel, liver or spleen
puncture, especially in children. Needle depth should be
confirmed by the fascial click, since the risk increases if the
needle is introduced too deep when the ‘pop’ is not identified
(Hong 2010).
There is a weak correlation between weight and the depth of
the IIN (Willschke 2005). These findings emphasize the
usefulness of ultrasounds for this block technique and the fact
that needle tip visualization is mandatory (Weintraud 2008).