Aspiration and Drainage

Anatomy

Figure 3. The “Triangle of Safety”

The preferred site for aspiration or drain insertion is usually within the triangle of safety (see Figure 2). It is bordered:

• Anteriorly by the lateral edge of pectoralis major
• Laterally by the lateral edge of latissimus dorsi
• Inferiorly by the line of the fifth intercostal space
• Superiorly by the base of the axilla

Sometimes a posterior lying effusion will be best approached with imaging guidance from the back with the patient sitting forward.

Diagnostic aspiration

A 21 G (green) needle attached to a 50ml syringe should be directed along the top of a rib to avoid damaging the neurovascular bundle. Medial sites (less than 5cm from the thoracic spine) should be avoided as the intercostal artery is in the middle of the intercostal space in this region. Local anaesthetic is not required if landmarks can be easily felt.

A chest x-ray after a simple pleural aspiration is not required unless air is withdrawn, the procedure is difficult, multiple attempts are required or the patient becomes symptomatic

Therapeutic aspiration

1% lignocaine is infiltrated to the skin and particularly the pleura (fluid aspiration confirms the depth of the chest wall). A cannula should be attached to three way tap and tubing/syringe. It is recommended to use a cannula of 20G or smaller where feasible as there is weak evidence that a large bore needle is more likely to cause a pneumothorax. However, in some patients with thick chest walls a larger needle may be required.

The procedure should be stopped when no more fluid or air can be aspirated, the patient develops symptoms of cough or chest discomfort or 1.5 litres has been withdrawn. After the cannula is removed a simple dressing should be applied.

When the cause is unclear and the effusion large, a post-procedure chest radiograph may be requested to view the underlying lung.

Chest drainage

• Antibiotic prophylaxis is not recommended for non-trauma patients requiring a chest drain.
• Local anaesthetic should be used and analgesia given
• Procedural sedation should be considered
• Needle aspiration (following local anaesthetic infiltration) should confirm the presence of fluid before proceeding to drain insertion
• Drains should never be inserted using substantial force
• The dilator should not be inserted further than 1cm beyond the depth from the skin to the pleural space
• Small drains (8-14 Fr) should be inserted for free flowing effusions or infections
• The drain should be secured using sutures and an omental tag of tape (see Figure 3)
• The chest drain should be connected to an underwater drainage system and no more than 1.5 litres of fluid allowed to drain in the first hour after insertion
• A repeat chest radiograph should be requested post procedure.
• A chest drain may be withdrawn to correct a malposition, but should never be pushed further in due to the risk of infection.