I. Definition
Thoracentesis is the procedure used to aspirate pleural fluid from the pleural space for diagnostic or therapeutic purposes.
II. Indications
- Diagnostic:
- Suspected pleural effusion of unknown cause
- Fever + unilateral effusion (to rule out empyema, TB, malignancy)
- Exudate vs transudate differentiation
- Therapeutic:
- Relief of dyspnea due to large effusion
- Drainage of empyema or malignant effusions
IV. Procedure Steps (Thoracentesis)
- 1. Position:
- Patient sits upright, leaning slightly forward.
- Arm on affected side rests on a table.
- 2. Site:
- 7th or 8th intercostal space, midaxillary line.
- Go above the rib to avoid intercostal neurovascular bundle.
- 3. Preparation:
- Aseptic technique, local anesthesia (lidocaine)
- Insert needle attached to syringe or catheter
- Aspirate fluid slowly
- 4. Post-procedure:
- Send samples for analysis
- Obtain chest X-ray to rule out pneumothorax
V. Pleural Fluid Analysis
➤ 1. Physical Appearance
➤ 2. Biochemical Tests
Use Light’s Criteria to differentiate exudate vs transudate:
- Pleural fluid protein / serum protein > 0.5
- Pleural fluid LDH / serum LDH > 0.6
- Pleural fluid LDH > 2/3 upper limit of normal for serum LDH → If any of these are true → Exudate
➤ 3. Microscopy and Cytology
- Cell count: Neutrophils (infection), lymphocytes (TB, malignancy)
- Gram stain & culture: Bacterial cause
- AFB stain: Suspect TB
- Cytology: Suspect malignancy