How is a posterior intercostal block administered for pain management?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

Answer

The posterior intercostal block, as described by Bonica, is carried out easily at the angle of the rib, where it is the most superficial and easiest to palpate. The patient is placed in the lateral position with the target side up if performing a unilateral block or in prone position if performing bilateral blocks. A 3-cm, 25-gauge, short-beveled needle is inserted through a skin wheal at the lower edge of the posterior angle of the rib. The second finger of the left hand is placed over the intercostal space and the skin is pushed gently cephalad so that the lower edge of the rib above can be palpated simultaneously. This technique protects the intercostal space, thus reducing the risk of passing the needle into the lung. See the images below.

Position of patient for posterior intercostal bloc Position of patient for posterior intercostal block technique.
Intercostal block technique. See text for details. Intercostal block technique. See text for details.
A - Posterior intercostal block technique. See tex A - Posterior intercostal block technique. See text for details.
B - Posterior intercostal block technique. See tex B - Posterior intercostal block technique. See text for details.
C - Posterior intercostal block technique. See tex C - Posterior intercostal block technique. See text for details.

The needle is advanced until the lower part of the lateral aspect of the rib is reached. After reaching the rib, the needle is grasped with the thumb and index finger of the left hand about 3-5 mm above the skin surface. The skin is moved caudally with the left index finger to allow the needle to slip just below the lower border of the rib and then the needle is advanced until the left thumb and finger grasping the needle become flush with the skin. Aspiration is attempted; if negative, 3-4 mL of LA solution is injected. This LA solution diffuses several centimeters distally and proximally to involve the sympathetic chain, which may also block visceral nociceptive pathways, thus helping to relieve pain, which arises from painful viscera as well. Injection of larger volumes will result in both paravertebral and epidural spread of the drug, which may cause arterial hypotension if many segments are involved.


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