Page 166 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

Chapter 12
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Pleural drainage techniques

Victoria Lipscomb, David E. Holt and Lori S. Waddell

Anatomy and physiology Thoracocentesis
The simplest and quickest way to remove fluid or air from
A thin serous membrane, the pleura, lines all surfaces within the pleural cavity is by needle thoracocentesis (see
the thoracic cavity.
Operative Technique 12.1). Thoracocentesis helps rapid
• The parietal pleura covers the chest wall, diaphragm stabilization of an animal in immediate respiratory distress
and mediastinal structures. due to pleural space disease and enables diagnostic eval-
• The visceral pleura covers the lungs, including the uation of pleural fluid. Butterfly cannulae are well suited for
interlobar fissures. thoracocentesis because they are available in a variety of
• The pleural cavity is the potential space between the needle sizes and lengths, are easy to hold and manipulate,
parietal and visceral pleura, which are normally directly and come with pre-attached extension tubing. Over-the-
apposed. needle catheters may also be used; once the inner stylet is
removed, the tip (residing in the pleural cavity) is relatively
The vascular supply to the parietal pleura is via the inter- atraumatic compared with a needle. However, catheters
costal, pericardial and diaphragmatic vessels, whereas the are very flexible and often kink, obstructing drainage.
visceral pleura is supplied by the pulmonary vasculature. If possible, a dorsoventral (DV) radiograph or quick
A small amount of fluid is normally present within thoracic ultrasound examination is recommended prior to
the pleural space and lubricates the pleural surfaces, thoracocentesis to document the presence of fluid or air
enabling frictionless lung movement. The overall balance
and to determine which side might be the most suitable to
of hydrostatic and colloid osmotic pressures in the pleural aspirate first. The stress of radiography can be life-threat-
space under normal physiological conditions results in
pleural fluid being produced by the systemic capillaries of ening in animals with significant respiratory compromise
and in such cases a decision should be made to perform
the parietal pleura and absorbed by the pulmonary capil-
laries of the visceral pleura. An important route for pleural thoracocentesis first on the basis of the clinical findings. A
fluid removal is via cellular transport mechanisms asso- ventrodorsal (VD) position for radiography should not be
attempted in these animals as it dramatically reduces the
ciated with metabolically active mesothelial cells. The
other major drainage route for the pleural cavity is via ability to cope with respiratory compromise.
the rich lymphatic network in the parietal pleura, which Radiographs are taken after thoracocentesis to docu-
empties into the thoracic duct system (TDS). ment successful aspiration of the pleural cavity and to try
Inflammation, infection or neoplasia affecting the pleura to identify an underlying cause, which may have been
tends to result in increased pleural fluid production. obscured by the presence of fluid and collapse of the
Drainage of the pleural cavity via the lymphatics is inhibited lung lobes.
by thickening of the pleura by neoplastic lymphatic Complications of thoracocentesis include lung lacera-
obstruction and by lymphatic hypertension associated with tion, iatrogenic pneumothorax and haemorrhage, but with
increased venous pressures. attention to careful technique the risks are small (especially
The pressure within the pleural space is approximately when compared with the substantial respiratory relief
4–6 mmHg below atmospheric pressure. This relatively afforded to the animal). If an animal remains dyspnoeic
small pressure difference is sufficient to maintain adequate after successful aspiration of pleural fluid, concurrent lung
lung expansion throughout the respiratory cycle. The pres- disease (e.g. neoplasia, pulmonary contusions, pulmonary
sure gradient is greatest during inspiration. oedema, pneumonia) or development of a pneumothorax
must be suspected.

Pleural drainage techniques Chest drains

Indications for pleural drainage include any situation Placement of a chest drain is indicated when frequent or
where fluid or air has accumulated, or is likely to accumu- repeated drainage is required because of ongoing accu-
late, in the pleural cavity. The amount of fluid and/or air mulation of fluid or air in the pleural cavity. A chest drain
retrieved is always recorded. The pleural fluid is submitted may form part of the definitive treatment plan for a condi-
for laboratory analysis and culture, and this is repeated as tion such as simple pyothorax. Alternatively, a chest drain
required during treatment of the underlying condition. may be used for stabilization of an animal prior to definitive

BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, second edition. Edited by Daniel J. Brockman, David E. Holt and Gert ter Haar. ©BSAVA 2018 157

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