Pleural tap (thoracentesis)

💡 Key Point: Pleural aspiration is performed for diagnosis or symptom relief. Always identify the cause of effusion, use ultrasound guidance if possible, and avoid removing >1–1.5 L in one sitting to prevent re-expansion pulmonary oedema.

🎯 Indications

• 🔍 Diagnostic: To determine the cause of a pleural effusion (infection, malignancy, heart failure, etc.).
• 💨 Therapeutic: To relieve dyspnoea or chest discomfort caused by large effusions.
• 🕊️ Palliative: Recurrent drainage in malignant or end-stage effusions, though recurrence is high without pleurodesis.

⚠️ Precautions

• 👩‍⚕️ Only trained staff or supervised trainees should perform the procedure.
• 📡 Use ultrasound guidance whenever possible — it reduces pneumothorax risk by up to 70 %.

🚫 Cautions

• 🩸 Coagulopathy / Anticoagulants: Check INR and platelet count; hold Warfarin, Heparin, or DOACs where safe.
• 💨 Ventilated patients: Higher risk of tension pneumothorax and bronchopleural fistula — perform only with senior input.
• 🦠 Local infection: Avoid puncturing through cellulitic or infected skin.

🧰 Required Equipment

• 1 % or 2 % Lidocaine (local anaesthetic).
• Basic dressing pack, sterile towels, sterile gloves.
• Iodine / Chlorhexidine solution for skin prep.
• Sterile sample pots (plain, fluoride, and EDTA if required).
• Needles: 27 G (orange) + 21 G (green); cannula: 16 G (grey).
• 10 mL and 20 mL syringes for aspiration.
• Ultrasound probe and sterile cover (if available).

🩺 Procedure Steps

• 🗣️ Consent and Preparation: Explain, obtain written consent, and position the patient sitting upright, leaning forward with arms supported on a pillow or table. Monitor oxygen saturation continuously.
• 📍 Site Selection: Confirm side and level using percussion and chest X-ray; mark 1–2 ribs below the upper border of dullness, usually at the mid-scapular or posterior axillary line. Always insert just above the upper border of a rib to avoid the neurovascular bundle.
• 🧴 Aseptic Prep: Clean the skin and apply sterile drapes.
• 💉 Local Anaesthetic: Infiltrate 5–10 mL Lidocaine using a fine needle superficially, then a green needle deeper to anaesthetise the pleura — aspirate before injecting to avoid intravascular administration.
• 💧 Aspiration: When pleural fluid is reached, attach a syringe to collect diagnostic samples. For larger volumes, use a grey cannula with a 3-way tap and 50 mL syringe or a controlled drainage system.
• 🚫 Drainage Limit: Do not remove >1–1.5 L to prevent re-expansion pulmonary oedema (caused by rapid negative intrathoracic pressure).
• 🩹 Completion: Remove the cannula, apply firm pressure for 1 minute, and dress with a sterile occlusive dressing.

🧪 Laboratory Analysis of Pleural Fluid

🩻 Post-Procedure Care

• 🗑️ Dispose of sharps and contaminated materials safely.
• 📸 Chest X-ray: To exclude pneumothorax and confirm fluid removal. Small pneumothoraces may be observed; large or symptomatic ones → chest drain.
• 🖋️ Documentation: Record side, site, volume, appearance, and any complications.

⚠️ Complications

• 😣 Pain: During puncture or drainage — use adequate local anaesthetic; consider analgesia or opioids if needed.
• 💨 Pneumothorax: Common (up to 30 %), but only < 5 % require a drain.
• 🩸 Bleeding: From intercostal vessel injury or coagulopathy.
• 🦠 Infection: Risk of empyema; use strict asepsis.
• ⚕️ Organ Injury: Liver or spleen puncture if site too low — always check imaging and landmarks.
• 🌫️ Re-expansion Pulmonary Oedema: Rare but serious; prevent by limiting fluid removal and monitoring for cough or chest tightness during aspiration.

📚 References

• BTS Pleural Procedures Guideline (2023)
• NICE CKS: Pleural Effusion
• Light RW. Pleural Diseases. 7th ed. Lippincott Williams & Wilkins, 2020.