Thoracentesis
Thoracentesis, commonly known as a pleural or chest tap, is a procedure where excess pleural fluid is drained from the pleural space for diagnostic and/or therapeutic reasons. Ultrasound-guided thoracentesis performed by radiologists has been shown to have fewer complications than blind thoracentesis. A success rate of up to 90% has been demonstrated after failed blind thoracentesis.
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Indications
- symptomatic pleural effusions
- investigation of cause of pleural fluid collection, e.g. malignancy, infection, etc
Contraindications
- coagulopathy/thrombocytopaenia, anticoagulation or other bleeding disorders
- respiratory disease such as severe respiratory failure, intractable coughing, contralateral pneumonectomy, emphysema, suspected echinococcal disease or the inability to hold one's breath 7
Procedure
Thoracentesis can be performed blind, partially imaged-guided or image-guided (usually ultrasound but may be CT). Below the technique for an ultrasound-guided therapeutic thoracentesis with a trocar technique is outlined as this is the most commonly performed in radiology. Seldinger technique is an alternative method.
Preprocedural evaluation
- review history, pathology results and prior imaging
- e.g. 75% of pleural effusions secondary to congestive cardiac failure will resolve with two days of diuresis and thoracentesis should be reserved for refractory cases 3
- obtain informed written consent
- completion of a "time-out" with nursing staff
Positioning/room set up
- patient sitting on edge of bed, leaning forward with arms on a table
- monitoring (BP, pulse rate, SpO2)
- access from behind the patient
Equipment
- ultrasound with CH-4 probe
- sterile pack including wash, gown and gloves, drape, ultrasound cover and sterile gel
- long hypodermic needle, syringe and lignocaine
- scalpel
- thoracentesis/paracentesis catheter-over-needle set
- three-way tap and drainage bag
- dressings
Technique
- pre-procedure ultrasound to confirm presence of drainable pleural effusion
- sterile glove and gown followed by sterile preparation and drape
- subcutaneous and deep infiltration to pleura of local anaesthetic under ultrasound guidance
- small skin nick with scalpel
- under ultrasound guidance, introduction of thoracentesis needle along the superior margin of the rib, aspirating while advancing until pleural fluid is aspirated; catheter is then slid off needle
- connection of three-way tap and drainage bag and airtight dressing applied
- for diagnostic thoracentesis 50 mL of fluid is usually required 3
Postprocedural care
- volume to be drained varied depending on number of prior taps
- for first-time taps ~1500 mL (or until symptoms such as chest pain commence) is recommended to reduce the occurrence of re-expansion pulmonary oedema 4,5
- requirement for post-thoracentesis chest x-ray to assess for pneumothorax is debated; literature has demonstrated there is a very low risk of pneumothorax in asymptomatic patients 1
- patient should be advised of the risk of pneumothorax and not to fly for one week 6
Complications
Common complications from thoracentesis include 1,4:
- pain (~20%)
- cough
- vasovagal reaction
- re-expansion pulmonary oedema (~7.5%)
Serious, but less common, complications from thoracentesis include 1,3,4:
-
pneumothorax (<5%) including tension pneumothorax and hydropneumothorax
- may require treatment with an intercostal catheter (~20%)
- haemothorax (1%) or chest wall haemorrhage
- intercostal nerve, artery or vein damage
- trapped lung
- non-diagnostic or non-therapeutic procedure
- liver and splenic trauma from inadvertent puncture
- pleural infection or empyema (rare; <1 in 2000)
- air embolism
Outcomes
- in malignant pleural effusions the average duration of symptom relief is 4 days and 99% of patients will reaccumulate pleural fluid 5
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