Pleural aspiration and chest drain
Ultrasound-guided, in the safe triangle, above the rib. Send protein, LDH, pH, glucose, cytology and culture. Don't drain more than 1.5 litres at once.
A 68-year-old ex-smoker has a large left pleural effusion and is breathless at rest. Ultrasound shows a large free-flowing collection. A diagnostic and therapeutic tap is planned.
A 24-year-old tall, thin man has a large right pneumothorax and is breathless after a failed aspiration.
Where do you go in, what do you send, and how much fluid can you take?
- Ultrasound guidedStrongly recommended for all pleural fluid procedures.
- Safe triangleLateral edge of pectoralis major, anterior edge of latissimus dorsi, line above the nipple (5th space). Apex below the axilla.
- Just above the rib belowThe neurovascular bundle runs under each rib.
- Diagnostic tap50 mL: send for protein, LDH, pH, glucose, Gram stain, culture, AFB, cytology.
- TherapeuticUp to about 1.5 L at a time. Stop if chest tightness, coughing or pain.
- AfterwardsObservations, chest X-ray if complications suspected.
- Pleural pH below 7.2 or pus
- Breathlessness, coughing or chest tightness during drainage (re-expansion oedema)
- Low BP or rising heart rate
- Blood in the drain over 200 mL an hour
- Surgical emphysema spreading
- Empyema
- Malignancy
- Iatrogenic pneumothorax
- Re-expansion pulmonary oedema
- Intercostal artery injury
- Organ puncture (liver, spleen) going too low
| Light's criteria (exudate if any) | Fluid/serum protein above 0.5, Fluid/serum LDH above 0.6, Fluid LDH above two-thirds of upper normal serum LDH |
| Pleural pH below 7.2 | Infected effusion: needs a drain |
| Therapeutic aspiration | Up to about 1.5 L at one time |
| Drain size | Small-bore (12–14 Fr) for most fluid and pneumothorax |
| Cytology | At least 25–50 mL |
| Site | Safe triangle, mid-axillary line, 4th–5th space |
Check every dose against a current drug reference and your hospital protocol.
On this page
Indications
- Diagnostic: any new unexplained effusion.
- Therapeutic aspiration: breathless with a large effusion.
- Chest drain: empyema or pH below 7.2, large or recurrent malignant effusion (for pleurodesis), pneumothorax after failed aspiration, tension after decompression, haemothorax.
The safe triangle
- Front: lateral border of pectoralis major.
- Back: anterior border of latissimus dorsi.
- Bottom: a horizontal line at the level of the nipple (5th intercostal space).
- Apex: just below the axilla.
Enter just above the upper border of the rib below, because the intercostal vein, artery and nerve run in the groove under each rib.
Diagnostic and therapeutic aspiration
- PrepareUltrasound, consent, sterile field, lidocaine, green needle, 50 mL syringe, three-way tap, drainage set, sample bottles.
- PositionSitting forward over a table with arms folded, or lateral position for the safe triangle.
- Mark with ultrasoundDeepest pocket away from the diaphragm, liver and spleen.
- AnaestheticLidocaine down to the pleura; aspirate fluid with the anaesthetic needle to confirm.
- Diagnostic50 mL in a syringe: protein, LDH, pH (in a blood gas syringe), glucose, Gram stain and culture (and blood culture bottles), AFB and TB culture, cytology.
- TherapeuticVia three-way tap, drain up to about 1.5 L. Stop if coughing, chest tightness or pain.
Interpreting the fluid
| Test | Result | Meaning |
|---|---|---|
| Light's criteria | Any one positive | Exudate |
| Protein below 25 g/L (2.5 g/dL), Light's negative | Transudate | Heart failure, cirrhosis, nephrotic syndrome |
| pH below 7.2 | Infected | Chest drain |
| Glucose low | Infection, rheumatoid, malignancy, TB | |
| LDH very high | Empyema, malignancy | |
| Lymphocytes high | TB, malignancy, lymphoma | |
| Milky | Chylothorax (triglycerides) | |
| Frank pus | Empyema | Chest drain |
| Blood-stained | Malignancy, PE, trauma (haematocrit over 50% of blood = haemothorax) |
Pakistan: TB is a common cause of lymphocytic exudates. Send AFB and TB culture, and ask for ADA if available.
Chest drain
- Indication confirmed, consent, clotting checkedUltrasound for fluid.
- Safe triangle, local anaestheticAspirate air or fluid to confirm.
- Needle and guidewireOver the rib below.
- Dilate, then insert the drain over the wireSmall-bore 12–14 Fr for most.
- Connect to underwater sealCheck swinging and bubbling. Suture and dress.
- Chest X-rayPosition and lung expansion.
Swinging (fluid moving with breathing) means the drain is in the pleural space. Bubbling means an ongoing air leak. Never clamp a bubbling drain.
Complications
| Complication | Features | Action |
|---|---|---|
| Pneumothorax | Breathless, air on aspiration | Chest X-ray, drain if large |
| Re-expansion oedema | Coughing, breathless, hypoxic after large drainage | Stop draining, oxygen, supportive care |
| Bleeding | Blood in drain, falling Hb | Senior, surgeons |
| Organ injury | Going too low (liver, spleen) | Ultrasound guidance prevents |
| Infection | Fever, pus at site | Culture, antibiotics |
| Vasovagal | Faint, slow pulse | Lie flat, stop |
Treatment
See pleural effusion and pneumothorax.
Common mistakes
- Tapping without ultrasound.
- Going below the rib (neurovascular bundle).
- Going too low (liver, spleen).
- Draining 3 litres in one go.
- Sending pH in a plain pot or after air exposure (falsely high).
- Clamping a bubbling drain.
Frequently asked questions
Where is the safe triangle?
Bounded by the lateral edge of pectoralis major, the anterior edge of latissimus dorsi and a line at the level of the nipple, with the apex below the axilla.
What are Light's criteria?
An effusion is an exudate if fluid/serum protein is above 0.5, fluid/serum LDH is above 0.6, or fluid LDH is above two-thirds of the upper normal serum LDH.
How much fluid can be drained in one go?
Up to about 1.5 litres at one time to reduce the risk of re-expansion pulmonary oedema.
Why is the needle inserted above the rib?
The intercostal vein, artery and nerve run in the groove under each rib.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. Why is a pleural needle inserted just above the upper border of a rib?
Answer: Vessels run under the rib. Intercostal vessels and nerve run in the costal groove.
- The lung is further away: No.
- It avoids the diaphragm: No.
- The rib is weaker there: No.
- It is less painful in all cases: Not the main reason.
2. What is the usual maximum volume drained in one therapeutic pleural tap?
Answer: 1.5 litres. Stop at 1.5 L or earlier with cough or chest tightness.
- 5 litres: Risk of re-expansion oedema.
- 3 litres: Usually too much.
- As much as possible: Unsafe.
- 500 mL: Too little.
3. Which is a border of the safe triangle?
Answer: Lateral border of pectoralis major. Pectoralis major, latissimus dorsi and the 5th intercostal space.
- Medial border of the scapula: No.
- Clavicle: No.
- Sternum: No.
- Costal margin: No.
4. A pleural tap shows fluid protein 38 g/L (serum 60), fluid LDH 400 U/L (serum upper limit 250), lymphocyte-rich, ADA 70 U/L. What is the most likely cause in Pakistan?
Answer: Tuberculous effusion. Light’s criteria (exudate if any): fluid:serum protein > 0.5, fluid:serum LDH > 0.6, fluid LDH > ⅔ of upper limit of normal serum LDH. Here protein ratio 0.63 and LDH > 167 → exudate. Lymphocytic exudate with high ADA (> 40) strongly suggests TB; pleural biopsy confirms. Causes of exudate: TB, parapneumonic, malignancy, PE, RA. Transudates: heart failure, cirrhosis, nephrotic syndrome, hypothyroidism.
- Congestive heart failure: Heart failure causes a transudate.
- Hepatic hydrothorax: Hepatic hydrothorax is a transudate.
- Nephrotic syndrome: Nephrotic syndrome causes a transudate.
5. At which rib level does the lower border of the parietal pleura cross the mid-axillary line?
Answer: 10th rib. Remember 6–8–10–12: the lungs' lower border lies at the 6th rib (mid-clavicular), 8th (mid-axillary) and 10th (posteriorly); the pleura is two ribs lower: 8th, 10th and 12th. The space between them is the costodiaphragmatic recess, where fluid collects and where pleural taps are done.
- 6th rib: Lung at the mid-clavicular line.
- 8th rib: Lung border at the mid-axillary line.
- 12th rib: Pleura posteriorly near the vertebrae.
- 4th rib: Not correct.
6. Pleural fluid has protein 45 g/L (serum 60 g/L) and LDH 400 IU/L (serum 300). How is it classified?
Answer: Exudate. Light's criteria: exudate if any of fluid/serum protein > 0.5, fluid/serum LDH > 0.6, or fluid LDH > ⅔ upper limit of normal serum LDH. Here 45/60 = 0.75 and 400/300 = 1.3. Exudates: infection, malignancy, PE, inflammation. Transudates: heart failure, cirrhosis, nephrotic syndrome.
- Transudate: Ratios exceed thresholds.
- Chylous effusion only: Needs triglycerides; not suggested.
- Normal pleural fluid: Abnormal.
- Haemothorax: Needs haematocrit.
References and dose sources
- Lidocaine (lignocaine) dosing: Drugs.com: Lidocaine dosage (see also our lidocaine (lignocaine) dose page)
- Co-amoxiclav (amoxicillin with clavulanic acid) dosing: Drugs.com: Amoxicillin/clavulanate dosage (see also our co-amoxiclav (amoxicillin with clavulanic acid) dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.