3. An intraoperative intercostal block in a dog after lateral thoracotomy. The surgeon has visualized and palpated both the
dorsal and ventral branches of the intercostal nerves on the caudal aspect of the ribs near the intervertebral foramen and
is depositing a mixture of lidocaine and bupivacaine near the nerves.
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Conscious patients that require an intercostal nerve block for analgesia of rib fractures will likely require sedation with
appropriate systemic drugs, such as opioid and benzodiazepine combinations. The block is performed as dorsally as possible,
near the intervertebral foramen. With the patient in lateral recumbency and the needle perpendicular to the lateral aspect
of the body, advance the needle onto the rib, and then walk it caudally until it enters the tissues behind the rib's caudal
border. After aspirating the syringe to avoid intravascular administration, inject the local anesthetic. Repeat this procedure
to block three intercostal nerves in front of the incision (or fractured ribs) and three caudal to it, in addition to the
site of interest.1,2,8,9
INTRAPLEURAL ANALGESIA
Local anesthetics can be administered into the pleural cavity (between the visceral and parietal pleura) to provide analgesia
after a lateral or sternal thoracotomy, in patients with thoracic trauma, and in patients with cranial abdominal pain, such
as that associated with acute pancreatitis.1,8-10 The mechanism of analgesia has been suggested to be due to diffusion of local anesthetic through the parietal pleura, causing
intercostal nerve block, blockade of the thoracic sympathetic chain and splanchnic nerves, and diffusion of the anesthetic
into the ipsilateral brachial plexus, resulting in blockade of the parietal peritoneum.8-11 Because cranial abdominal nerves enter the spinal cord at the level of the thorax, intrapleural administration of a local
anesthetic blocks the cranial abdominal nerves, and this technique may be useful for acute pancreatitis or cranial abdominal
surgical procedures.9
Local anesthetics and adjunctive agents can be administered through a chest tube, if present. Follow the anesthetic drugs
with 3 to 5 ml of sterile saline solution to flush the tube. If a chest tube is not in place, a hypodermic needle, butterfly
catheter, or intravenous catheter can be used. Systemic analgesics and sedatives should be considered for conscious patients.
After sterile preparation and infiltration of the site of interest with 0.2 to 0.5 ml of 2% lidocaine, penetrate the chest
wall between the ribs with the stylet and catheter. Once the pleural space has been reached, advance the catheter off the
end of the stylet to avoid lung laceration. Attach a three-way stopcock and syringe to the catheter as soon as the stylet
is removed to avoid inducing a significant pneumothorax, and make sure the catheter is never left open to the environment.
A hypodermic needle or butterfly catheter should have the stopcock attached, closed to the needle, before penetration of the
chest wall.
Local anesthetic administered intrapleurally is rapidly and extensively absorbed systemically, so be sure to avoid using toxic
doses. Inflammation and the resulting tissue acidity may reduce the efficacy of local anesthetics and result in increased
systemic absorption. If possible, place the patient with the incision site down, and maintain the patient in that position
during needle placement and drug injection and for at least 10 minutes afterward, as this may facilitate local anesthetic
pooling over the incision and blocking of the adjacent intercostal nerves.9 This position may be uncomfortable for the patient, so it is best performed after systemic administration of an analgesic,
such as an opioid, to improve patient tolerance.
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