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ANESTHESIA ALERT
cal landmarks to locate the proper needle insertion site on the lateral
abdominal wall — then inserting a needle through it and advancing it
until 2 pops were felt, indicating the needle had passed through the
fascial layers of the external and internal oblique muscles. Ideally, the
needle was then within the TAP and could deposit local anesthetic.
But the landmark technique was challenging and the results were
variable and unpredictable. By using ultrasound, which shows in real
time the needle advancing through the muscle layers, we can improve
the safety and effectiveness of needle placement. And we can confirm
that the needle tip has reached the TAP by injecting l to 2ml of normal
saline or local anesthetic. This appears on ultrasound as a hypoechoic
or dark area between the fascial layers, as you can see in the ultrasound image. We can also see the remaining local anesthetic as it's
administered.
3 common injection sites
The distribution of the block depends on the injection site and the volume of local anesthetic. The 3 most common methods for accessing
the TAP are the subcostal, mid-axillary and ilioinguinal-iliohypogastric
(II/IH) approaches.
• Subcostal. The subcostal injection site is inferior to the costal margin near the linea semilunaris. This approach targets nerves T7-12, and
is best for upper abdominal surgeries.
• Mid-axillary. The mid-axillary injection site is near the mid-axillary
line between the costal margin and iliac crest. This approach is ideal
for abdominal surgeries below the umbilicus, because it targets
nerves T10-L1.
• Ilioinguinal-iliohypogastric. The II/IH injection site is medial and
superior to the anterior superior iliac spine, which more reliably
blocks the 2 branches of L1 (ilioinguinal and iliohypogastric nerves),
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O U T PAT I E N T S U R G E R Y M A G A Z I N E O N L I N E | A U G U S T 2013