Definition
Thoracentesis (Pleural Tapping) is the percutaneous aspiration of fluid from the pleural space for diagnostic or therapeutic purposes. It is one of the most commonly performed bedside procedures in internal medicine and critical care.
🔬 Diagnostic
- • New-onset pleural effusion
- • Undiagnosed effusion persisting >3 days
- • Suspected empyema or malignant effusion
- • Fever with pleural effusion
- • Differentiation: Transudate vs Exudate
💊 Therapeutic
- • Large symptomatic effusion (dyspnea)
- • Massive effusion with mediastinal shift
- • Empyema drainage
- • Instillation of sclerosing agents
- • Relief before definitive surgery
⛔ Absolute
- • Uncooperative patient
- • Uncorrected bleeding diathesis (INR >1.5, Platelets <50,000)
- • Skin infection at puncture site
- • Mechanical ventilation (relative — needs expert)
⚠️ Relative
- • Small effusion (<1 cm on USG)
- • Altered coagulation (use USG guidance)
- • Bullous emphysema
- • Single functioning lung on contralateral side
- • Anticoagulant therapy
Sterile Kit
- • Sterile gloves & gown
- • Sterile drapes
- • Antiseptic (Povidone-iodine / Chlorhexidine)
- • Gauze pads
Needles & Syringes
- • 18G & 20G needles
- • 16G/18G IV cannula
- • 20 mL & 50 mL syringes
- • 3-way stopcock
- • Connecting tubing
Anesthesia & Misc
- • 2% Lignocaine (Lidocaine)
- • 5 mL syringe + 25G needle
- • Sterile collection bottles
- • Adhesive dressing
- • USG machine (if available)
Step-by-Step Procedure
Patient Preparation & Consent
Explain the procedure, risks, benefits, and alternatives. Obtain written informed consent. Verify identity, check coagulation profile (INR, platelet count). Review imaging (CXR / USG) to confirm effusion side and estimate volume.
Positioning
Patient sits upright, leaning forward on a bedside table with arms supported. If unable to sit: lateral decubitus with affected side down. Mark the site using USG guidance (preferred) or percussion (dullness).
Site Selection
Landmark: 1–2 intercostal spaces below the upper border of percussion dullness. Typically 7th–9th intercostal space, in the mid-scapular or posterior axillary line. Always insert at the upper border of the lower rib (to avoid the neurovascular bundle running under each rib).
Aseptic Technique
Perform hand hygiene. Don sterile gloves and gown. Clean the area with antiseptic in concentric circles (inside → out). Apply sterile drapes around the puncture site. Maintain sterile field throughout.
Local Anesthesia
Infiltrate 2% Lignocaine (5–10 mL) using a 25G needle. Anesthetize: skin → subcutaneous tissue → intercostal muscles → parietal pleura. Aspirate before injecting at each layer. Walk the needle over the superior border of the rib.
Needle Insertion & Aspiration
Insert the aspiration needle (16–18G cannula) attached to a syringe via a 3-way stopcock. Advance perpendicular to the chest wall at the upper border of the lower rib. Apply gentle negative pressure. A "give" is felt as the needle enters the pleural space and fluid is aspirated.
Fluid Collection
Diagnostic: Aspirate 50–100 mL into sterile containers. Send for: biochemistry (protein, LDH, glucose), cell count & differential, Gram stain & culture, cytology, ADA, and pH. Therapeutic: Drain slowly, maximum 1–1.5 L in one sitting to prevent re-expansion pulmonary edema.
Needle Removal & Dressing
Ask the patient to hold breath in expiration or hum. Remove the needle swiftly. Apply firm pressure with gauze, then adhesive occlusive dressing. Ensure no air entry occurs during removal.
Post-Procedure Care
Monitor vitals for 1 hour. Obtain a post-procedure CXR (erect PA) within 1–2 hours to rule out pneumothorax. Document: volume aspirated, fluid appearance, samples sent, patient tolerance. Watch for: dyspnea, chest pain, cough, hypotension.
Light's Criteria — Exudate vs Transudate
An effusion is an Exudate if it meets any ONE of the following:
| Parameter | Exudate | Transudate |
|---|---|---|
| Pleural Protein / Serum Protein | > 0.5 | ≤ 0.5 |
| Pleural LDH / Serum LDH | > 0.6 | ≤ 0.6 |
| Pleural LDH | > ⅔ upper limit of normal serum LDH | ≤ ⅔ upper limit |
Common Transudates
CCF, Cirrhosis, Nephrotic syndrome, Hypothyroidism, Meigs' syndrome
Common Exudates
Pneumonia (parapneumonic), TB, Malignancy, Pulmonary embolism, Rheumatoid, Pancreatitis