thoracentesis

The

illustration shows a person having thoracentesis. The person sits upright and leans on a table. Excess fluid from the pleural space is drained into a bag.

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Thoracentesis, commonly known as a pleural tap 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.

Indications

symptomatic pleural effusions
investigation of cause of pleural fluid collection, e.g. malignancy, infection, etc

Contraindications

coagulopathy/thrombocytopenia, 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

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
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 anesthetic 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

Postprocedural care

volume to be drained varied depending on the number of prior taps
- ~1500 mL or until symptoms such as vague chest pain commence is recommended to reduce the occurrence of re-expansion pulmonary edema
- some authors believe it is safe to drain larger volumes
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
patient should be advised of the risk of pneumothorax and not to fly for one week

Complications

Common complications from thoracentesis include :

pain (~20%)
cough
vasovagal reaction
re-expansion pulmonary edema (~7.5%)

Serious, but less common, complications from thoracentesis include :

pneumothorax (<5%) including tension pneumothorax and hydropneumothorax
- may require treatment with an intercostal catheter (~20%)
hemothorax (1%) or chest wall hemorrhage
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