ABSTRACT: This article discusses the indications, placement and post-operative management of chest drains for use in cats and dogs. It will cover various points which are important to avoid the development of complications. Patients with chest drains in place require careful monitoring and management to avoid the complication of drain interference and iatrogenic pneumothorax, and to reduce the risk of hospital-acquired infection.

A chest drain is a tube placed temporarily into the chest cavity to allow drainage of the pleural space. Chest drains are also known as: thoracic drain, chest tube or thoracostomy tube.

The pleural cavity contains the heart and lungs and structures running within the cranial and caudal mediastinum. It is lined by a thin membrane on both the inner surface of the chest wall (parietal pleura) and the surface of the organs within the chest (visceral pleura).

The pleural space is the potential space between the edge of the lungs and the chest wall. Normally the space is empty, apart from a very small volume of normal pleural fluid which lubricates the movement of the lungs against the chest wall. The lungs are, therefore, able to expand and deflate freely in the pleural cavity.

Pathology

A number of pathological conditions can lead to accumulation of fluid or air in the pleural space. Also, any thoracic surgery in which the chest cavity is opened allows air to enter the chest cavity, and the presence of air or fluid in the pleural space prevents the lung from expanding and can, progressively, cause exercise intolerance, respiratory distress, decrease in cardiac output and death.

Drainage of the pleural space can be achieved by use of a needle and syringe (needle thoracocentesis) and is the most appropriate technique to use in an emergency, or if repeated drainage is not anticipated. The use of extension tubing and a three-way tap will facilitate needle thoracocentesis and reduce the risk of trauma to thoracic structures and accidental air leakage into the chest.

In certain conditions, repeated drainage of the pleural space may be required and post-operative drainage is always required following a thoracotomy (Figure 1). In these circumstances, a chest drain will be placed to facilitate repeated drainage.

Figure 1: Indications for placement of a chest drain

Chest drains may also be used as a route to deliver treatment – lavage fluids in cases of pyothorax, and delivery of local anaesthetic following thoracotomy, for example. They are available in various designs and different sizes. Choice of size is based upon patient size and intended use.

The chest drain must fit comfortably between the ribs within an intercostal space to ensure straightforward placement and optimal patient comfort. As a rough guide, the outer diameter of the chest drain should be approximately the width of the main stem bronchus, as seen on a lateral thoracic radiograph. In patients where thick pleural fluid is anticipated, a larger chest drain should be chosen to ensure adequate drainage.

Chest drain placement

Chest drain placement is painful and the patient must receive either sedation and local anaesthesia or a general anaesthetic. It has been suggested that the use of sedation and local anaesthesia is beneficial in higher risk patients owing to the avoidance of general anaesthesia.

In the majority of patients, the author prefers that they are under general anaesthesia for chest drain placement because there is improved control of the airway via endotracheal intubation, with the potential to provide intermittent positive pressure ventilation, if required. Patients must be carefully assessed and stabilised prior to general anaesthesia.

There are a number of techniques by which chest drains can be placed (Figure 2). The choice of technique will depend upon the patients condition and each veterinary surgeons choice.

Figure 2: Options for chest drain placement

Regardless of the technique used for placement, the intended positioning of the chest drain remains the same. The drain must be tunnelled under the skin for several centimetres before being passed through an intercostal space and into the pleural cavity. This is done to ensure air leakage cannot occur through the entry wound of the chest drain.

In general, the chest drain enters the skin at the level of the 10th to 12th intercostal space in the upper third of the chest wall. It is then tunnelled over a distance of 2 to 3 intercostal spaces and enters the chest cavity at the 7th to 8th intercostal space. The tip of the chest drain should sit in the lower third of the chest cavity. The chest drain is secured at the site of skin insertion by placement of a ‘finger trap’ or ‘friction’ suture.

The chest drain may be used intermittently or continuously. Intermittent drainage is the most common technique used. Following a thoracotomy, the chest drain will initially be drained by gentle aspiration of the chest drain every hour for the first four hours and may then be drained less frequently – for instance, every four hours over the following 12 hours.

The frequent drainage is important in the first few hours following a thoracotomy because it provides an important means of monitoring the patient for evidence of bleeding or air leakage. The frequency of drainage is determined by the rate at which fluid or air accumulates and the patients particular condition.

Continuous chest drainage is of benefit if the pleural space should be emptied very gradually – following surgery for chronic diaphragmatic rupture, for example – when gentle re-expansion of the lungs is required, or if on-going large volumes of air are leaking in a patient with pneumothorax.

The chest drain is connected to a chest drainage unit that, in turn, is connected to a suction machine. The apparatus allows regulation of the pressure used for drainage, a bottle for collection of fluid and a water trap to ensure a one-way flow of drainage (Figure 3). This technique requires that the patient be constantly monitored and it is most commonly seen in specialist referral centres.

Figure 3: A chest drainage system [Thoraco-Seal III! for continuous pleural drainage. The chamber with graduations on the left allows fluid to be collected and the volume monitored, the middle chamber is a water seal and the chamber on the right is connected to the suction apparatus and provides the suction control

Monitoring of the patient

Careful records must be made in the clinical notes each time the chest drain is used and the volumes of air and fluid removed must be recorded. The nature of the fluid should also be noted and for post-surgical patients it is useful to measure the packed cell volume of the fluid if it appears blood-tinged, in order to provide an early detection of post-operative bleeding.

The rate of fluid production should be calculated routinely and recorded. The
rate (ml/kg/hr) is calculated by dividing the amount of fluid (ml) by the time since the chest was last drained (hours) and the patient’s body weight (kg).

The patient should be carefully monitored by means of serial physical examination, including respiratory rate and effort, thoracic auscultation, pulse rate and quality and mucous membrane colour. The patient must also be monitored for comfort.

The presence of a chest drain alone does cause some degree of discomfort and the patient should receive appropriate analgesia, which may include a combination of an opioid (morphine, methadone, buprenorphine), non steroidal anti-inflammatory drug and local intrapleural analgesia.

Possible complications and how to prevent them

Patients with chest drains require very careful monitoring to ensure that serious complications do not occur. Life- threatening complications of uncontrolled pneumothorax, or ascending bacterial infection leading to pyothorax, can occur as a consequence of chest drain placement. Pneumothorax will occur if the airtight seal on the chest drain is lost, thereby allowing air to be drawn into the chest. This may happen if the chest drain is inadvertently left open, if a bite hole is created in the chest drain by the patient or if the chest drain has not been tunnelled under the skin adequately when placed.

Great care must be made to ensure that the chest drain has an airtight seal and will not allow air to be sucked into the pleural space. This is achieved by securely closing off the end of the chest drain with a syringe adaptor and bung or spigot, in addition to occlusion of the tube using a plastic C-clamp or metallic Gate-clamp (Figures 4 & 5).

Figure 4: A chest drain placed using a closed technique (a) has been secured in place using a Chinese finger trap tension suture and pre-placed purse string suture is now being placed. The chest drain is sealed using a specific adaptor with a push-fit connector, a plastic C-clamp and a bung (b). Image courtesy of Dr Stephen Baines

Figure 5: This chest drain is again secured using a Chinese finger trap suture and a preplaced purse string suture has been placed. The chest drain is closed using a metal gate clamp and a spigot. Image courtesy of Dr Stephen Baines

The chest drain must also be protected to ensure that it is does not become damaged, dirty or is accidentally removed. An adhesive sterile dressing should be applied over the wound entry site. The options for protecting the chest drain include a bandage around the chest, a stockinette dressing or a post-operative coat (Figures 6a, 6b, 6c).

When the patient is not directly supervised, an Elizabethan collar must be used to prevent patient interference. Every possible care must be taken to ensure that the risk of ascending bacterial infection is minimised. Careful hand hygiene is a ‘must’ and hand washing should be performed before handling the outside of the chest drain and, as always, when moving from one patient to another.

When the chest is drained, aseptic technique must be performed when attaching a syringe to the adaptor at the end of the chest drain. The end of the adaptor should be cleaned with surgical spirit and a new sterile syringe should be attached ensuring that the tip does not become contaminated.

The author advocates the use of sterile gloves when draining the chest, to ensure aseptic drainage.

When to remove the chest drain

Once there are indications that it is no longer required, the chest drain should be removed as soon as possible to avoid the potentially serious complications that can occur while it is in place. Guidelines for appropriate timing of removal include:

•   reduction in the level of fluid production to a constant steady rate (0.5 to 2 ml/kg/hr)

•   radiographic assessment which demonstrates resolution of the problem.

It is important to note that even if resolution of the condition has occurred, the fluid collected from a chest drain is likely to continue at a steady low level, since the presence of the chest drain stimulates some inflammation and fluid production.

Removal is achieved by cutting the Chinese finger trap tension suture securing the drain and gently withdrawing it. The pre-placed purse string suture – used to ensure that the wound is securely closed – is then tied and a sterile dressing is placed over the chest drain entry wound.

The patient should be monitored following chest drain removal for signs of increased respiratory rate and effort, which may indicate a recurrence of problems with fluid or air accumulation in the pleural space. Removal of the chest drain should not require the patient to be sedated but can be slightly uncomfortable and is ideally performed following administration of opioid analgesia. 

Author

Zoe Halfacree

Vet MB BA CertVDI CertSAS MRCVS

Zoe Halfacree is a lecturer in small animal surgery at the Royal Veterinary College, London. Zoe holds RCVS Certificates in Veterinary Diagnostic Imaging and Small Animal Surgery, and is a Diplomate of the European College of Veterinary Surgeon.

To cite this article use either

D0I: 10.1111/j.2045-0648.2011.00049.x or Veterinary Nursing Journal Vol 26 pp 195-198

Further reading

LIPSCOMB. V.. WADDELL. L. and HOLT, D. E. 120051 The pleural cavity and its drainage. In: BSAVA Manual of Canine and Feline Head. Neck and Thoracic Surgery. Ed Brockman. D. J. & Holt D. E. pp 148- 165. BSAVA, Gloucester.

• VOL 26 • June 2011 • Veterinary Nursing Journal