Ultrasound Blocks for the Anterior Abdominal Wall

62 | Ultrasound Blocks for the Anterior Abdominal Wall
rectus sheath is thin - if the peritoneum is inadvertently pierced,
bowel perforation may occur.
The advantages of ultrasound guidance for RSB are similar to
those for TAPB. A 100% success rate has been reported in the
ability to visualize the spread of anesthetic between the RAM
and the posterior sheath (Willschke 2006 (2)). In a study, the
anesthetic was placed in the correct plane in only 45% of cases
using a loss of resistance technique by trainees with no previous
experience and in 89% of cases using ultrasound guidance (Dolan
2009). The difference became more pronounced as patient body
mass index increased. 21% of injections performed using the loss
of resistance technique were intraperitoneal and 35% too
superficial.
Ultrasound-guided RSB is carried out with the transducer
placed in the longitudinal plane near the lateral edge of the
rectus sheath (Figure 6.3). The distribution of the local
anesthetic can be monitored under real-time imaging. The local
anesthetic is injected between the RAM and the posterior sheath
(Figure 6.1). Skin incision can be performed 15 minutes or later
after placement of the block.
Figure 6.3 – Rectus sheath under ultrasound guidance.