Miscellaneous blocks

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CHAPTER 10 Miscellaneous blocks

Intercostal nerve block

This technique may be used to ease the pain of rib fractures, to allow the insertion of an intercostal drain or for other thoracic procedures. It can be a very easy procedure in relatively thin patients, but in patients with a muscular chest well and obese patients it can be challenging with a high risk of pneumothorax. It should be avoided in patients with poor underlying respiratory function and those with coagulopathies.

Preparation

• Position the patient prone, in the lateral decubitus position (with the side to be blocked uppermost) or in a sitting position. Position the patient’s arms in such a way as to pull the scapulae laterally.

• Mark the inferior margins of the ribs to be blocked just lateral to the paraspinal muscles (about 60 to 80 mm lateral to the midline for the inferior ribs and 40 to 70 mm for the superior ribs).

• The ribs can be counted from the 12^th rib, or from the 7^th rib, which is the most inferior rib covered by the inferior angle of the scapula.

Technique

• Prepare the field by cleaning the skin with an antiseptic solution and positioning sterile drapes.

• Identify the target points for needle insertion – the inferior margin of the rib, just lateral to the paraspinal muscles.

• Raise a weal of local anaesthetic at each anticipated needle insertion point with a 25G needle.

• Pull the skin about 10 mm superiorly and puncture the skin with the needle parallel to the sagittal plane.

• Angle the needle 20° to 30° superiorly. The needle may be grasped with an artery forceps or a needle holder for better control (be careful not to crush the needle).

• Advance the needle until the rib is contacted (about 10 mm in the average patient, more in muscular or obese patients).

• Release the retracted skin and ‘walk’ the needle inferiorly while maintaining the superior angulation of the needle (Fig. 10.1).

• Once the inferior edge of the rib has been reached, advance the needle about 3 mm – you might feel a ‘pop’ as the fascia is penetrated. The average distance from the posterior aspect of the rib to the pleura is 8 mm, so be careful not to advance the needle too far.

• Aspirate. If no flashback of blood is obtained, inject 3 to 5 mL of local anaesthetic slowly with intermittent aspiration to rule out intravascular injection.

• Repeat the procedure with the other ribs to be blocked and one rib above and one rib below these levels.

• Local anaesthetic is rapidly absorbed after these blocks because of the high vascularity, so the toxic potential is high. Do not use more than 30 mL of bupivacaine for all the blocks combined.

Fig. 10.1 Insert the needle at the top of the rib to be blocked. Carefully ‘walk’ the needle inferiorly until the inferior margin of the rib is passed. Maintain the superior angulation of the needle in order to place the needle close to the intercostal nerve.

Ultrasound technique

Preparation

• Position the patient prone, in the lateral decubitus position (with the side to be blocked uppermost) or in a sitting position.

• Position the patient’s arms in such a way as to pull the scapulae laterally.

• Use a linear high-frequency probe (10 to 15 MHz is ideal) and select an appropriate pre-set application.

• Identify the area to begin the scan – the appropriate ribs to be blocked plus one rib above and one rib below.

• Perform a preliminary non-sterile survey scan to identify the relevant anatomy and optimise the image by adjusting depth of field (about 20 to 30 mm), focus point, and gain (Fig. 10.2). Mark the best probe position on the skin with a pen, if required.

• Place the probe between the posterior axillary line and the paraspinal muscles in the longitudinal plane in a suitable position to obtain a transverse view of the rib to be blocked, the intercostal space and the rib below. Position the probe with the index marker superiorly so that the needle will be seen coming from right to left on the screen.

• Prepare the field by cleaning the skin with an antiseptic solution and positioning sterile drapes. Cover the probe with a sterile probe-sheath and apply sterile ultrasound gel to the appropriate area.

Fig. 10.2 Place the probe in the longitudinal plane over the region to be blocked. Optimise the image prior to sterile preparation.

Technique

This block should only be performed using the in-plane approach so that the movement of the needle can be visualised in real time in order to avoid accidental pleural puncture.

In-plane approach

• Identify the rib to be blocked in its transverse section, along with the rib below and the intercostal space in an area convenient to block.

• Ensure that the pleura is clearly visible (look for pleural sliding and comet tails).

• Identify the target point for needle insertion – the superior border of the rib inferior to the one to be blocked. Position the inferior edge of the probe at the superior edge of the rib below the one to be blocked (Fig. 10.3).

• Raise a weal of local anaesthetic at the needle insertion target with a 27G needle.

• Insert a 25 mm to 50 mm 22G nerve-block needle at the inferior end of the ultrasound probe.

• Visualise the movement of the needle as it is advanced superiorly towards the intercostal groove (the nerve itself is not visible) (Fig. 10.4A&B). Ensure that the tip of the needle is visible at all times in order to avoid penetrating the pleura.

• Once the tip of the needle is in the costal groove, aspirate. If no flashback of blood is obtained, inject 3 to 5 mL of local anaesthetic slowly with intermittent aspiration to rule out intravascular injection.

• After the procedure is complete, confirm the absence of pneumothorax on the side of the procedure with standard ultrasound techniques.