VSR 421: Regional Veterinary Surgery (2+1)

THORACOCENTESIS

• Thoracentesis is an invasive procedure to remove fluid or air from the pleural space 

Pleurisy

• for diagnostic or therapeutic purposes.
• A cannula, or hollow needle, is carefully introduced into the thorax, generally after administration of local anesthesia .

Indications

• The most common causes of pleural effusions are cancer, congestive heart failure, pneumonia and recent surgery. In countries where tuberculosis is common, this is also a common cause of pleural effusions.
• When cardiopulmonary status is compromised (i.e. when the fluid or air has its repercussions on the function of heart and lungs), due to air (significant pneumothorax), fluid (pleural fluid) or blood (hemothorax) outside the lung, then this procedure is usually replaced with tube thoracostomy, the placement of a large tube in the pleural space.
• Supplies needed for thoracocentesis depend on the size of the pet.
• In most cats and small dogs, a butterfly catheter is of sufficient length to reach the thoracic cavity.
• In obese or big cats, and in larger dogs, a 37–50 (1.5–2 inch) needle may be used instead. The needle is connected to an extension set. A threeway stopcock is placed between the end of the butterfly catheter or extension set and a syringe. Usually a 10 or 20 ml syringe is adequate.
• In animals with very large volume of effusion (e.g. >1500 ml), it is often worthwhile to place a local block to permit the use of a larger gauge catheter (e.g. 14 or 16 ga) to remove the fluid more rapidly.
• The midventral aspect of the thorax is clipped and prepared for thoracocentesis. The intercostal vessels run caudal to the ribs.
• The preferred site of thoracocentesis is between the seventh and ninth rib spaces.
• The needle is advanced carefully into the thoracic cavity. Upon entry of the thoracic cavity, a gentle ‘pop’ is often felt by the experienced operator.
• A second operator should aspirate the fluid and provide feedback as to if the fluid is still flowing adequately.
• An aliquot of the fluid should be retained for cytological examination and, if warranted, bacterial culture and sensitivity testing.

Complications

• Major complications are pneumothorax (3-30%), hemopneumothorax, hemorrhage, hypotension (low blood pressure due to a vasovagal response) and reexpansion pulmonary edema .
• Minor complications include a dry tap (no fluid return), subcutaneous hematoma or seroma, anxiety, dyspnea and cough (after removing large volume of fluid).
• The use of ultrasound for needle guidance can minimize the complication rate.

Contraindications

• An uncooperative patient or a coagulation disorder that can not be corrected are absolute contraindications.
• Relative contraindications include cases in which the site of insertion has known bullous disease (e.g. emphysema), use of positive end-expiratory pressure (PEEP, see mechanical ventilation) and only one functioning lung (due to diminished reserve).
• The aspiration should not exceed 1L as there is a risk of development of pulmonary edema.