Ovid: Peripheral Nerve Blocks: A Color Atlas

Continuous Interpleural Block

Bruce Ben-David

Patient Position: Lateral decubitus with the arm dangling anteriorly and cephalad so as to rotate the scapula forward and expose the posterolateral chest wall.

Indications: Postoperative analgesia following mastectomy, nephrectomy, and cholecystectomy. Analgesia for rib fractures, pancreatitis, neuralgia, and invasive tumor of the chest wall, flank, and retroperitoneum.

Needle Size and Catheter: 18-gauge epidural needle and 20- or 21-gauge catheter.

Volume and Infusion Rate: Initial bolus of 20 to 30 mL 1% lidocaine followed by continuous infusion of 6 to 8 mL/hour 1% lidocaine.

Anatomic Landmarks: The seventh or eighth intercostal space, the scapula, and the posterior axillary line (Fig. 30-1A).

Approach and Technique: The site of needle insertion is at the seventh or eighth intercostal space at the level of the tip of the scapula and the cephalad border of the rib in a vertical direction perpendicular to the chest wall. Once inserted to a depth of 1 cm into the intercostal muscles, a syringe (with its plunger removed) is attached to the needle. The open syringe barrel is filled with saline. The needle is then slowly advanced while observing for both a “clicking” sensation and a downward movement (the “falling column”) of the saline as it is drawn into the chest by the negative pleural pressure. The syringe is removed (Fig. 30-1B) and the epidural catheter threaded 6 to 10 cm into the interpleural space. The Tuohy needle is removed, and the catheter is secured with 12 mm × 100 mm Steri-Strip (3M, St. Paul, MN) and covered with a transparent dressing (Fig. 30-1C).

Tips

An alternative site is 8 to 10 cm lateral from the posterior midline.

Interpleural blockade routinely causes pneumothorax due to the entrance of air through the needle. This is typically of small degree (<10%) and asymptomatic. The risk of lung injury is reduced by the use of proper technique and by avoiding percutaneous

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placement in patients with pulmonary bullae or those likely to have pleural adhesions. Proper technique includes (a) the use of a visual end point such as the “falling column” technique as opposed to a “loss-of-resistance” technique, and (b) placement during spontaneous ventilation as opposed to controlled ventilation or apnea.

Figure 30-1. A: Anatomic landmarks. B: The syringe is removed and the epidural catheter threaded 6 to 10 cm into the interpleural space. C: The Tuohy needle is removed, and the catheter is secured and covered with a transparent dressing.

As a result of drug sequestration, uneven distribution, and drug loss through chest tubes, interpleural block has not proven particularly useful after thoracotomy. However, satisfactory blockade can, at times, be achieved in the presence of a chest tube (e.g., rib fractures) by clamping the chest tube for 30 minutes following intermittent bolus of local anesthetic.
Placement at too low an intercostal space can lead to intraperitoneal placement of the needle and catheter.
The catheter should thread freely without resistance, which may indicate improper placement, lung penetration, or the presence of pleural adhesions.
Epinephrine should be added to any bolus to reduce peak systemic levels of local anesthetic.
Patient positioning will determine where the local anesthetic pools are, where it traverses the parietal pleura, and which nerves are affected. Lateral position (blocked side up) will promote blockade of the sympathetic chain while a supine or lateral position (blocked side down) will promote blockade of the intercostal nerves. A
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Trendelenburg position will promote upper thoracic and cervical sympathetic blockade (producing Horner syndrome) and even, at times, blockade of inferior roots of the ipsilateral brachial plexus.
Interpleural block is most useful when combined with multimodal analgesic therapies which may include nonsteroidal antiinflammatory drugs (NSAIDs) or a COX-2 inhibitor (celecoxib), NMDA blockade, alpha-2 agonists, A-2 delta calcium channel blockade (pregabalin), and opiates.
To minimize risk of systemic toxicity from the rapid reabsorption of local anesthetic solution in the interpleural space, lidocaine may be the preferred local anesthetic for infusion. While this author has typically used a 1% solution, a lower concentration may prove adequate.
Interpleural block will not usually provide the degree of neural blockade seen with thoracic paravertebral block (TPVB), but its simplicity is especially useful in certain patients, for example, the ventilated ICU patient with multiple rib fractures who is receiving low molecular weight heparin anticoagulation.