Pneumothorax After Regional Block

Pneumothorax after regional block is air in the pleural space caused by needle penetration of the pleura during supraclavicular, interscalene, paravertebral, intercostal, serratus or infraclavicular blocks, or trigger point injection.

Epidemiology. Supraclavicular block: about 0.2% to 6% without ultrasound and under 0.2% with ultrasound. Paravertebral: about 0.5%. Intercostal: about 0.1% to 0.5%. Delay of 6 to 24 hours is possible.

Risk factors. Low body mass index, chronic obstructive pulmonary disease, blebs, landmark technique, inexperience, deep needle insertion, positive pressure ventilation and nitrous oxide.

Pathophysiology.

Needle puncture of the visceral pleura creates an air leak into the pleural space. Positive pressure ventilation and nitrous oxide expand the air collection and can cause tension.

Pleuritic chest pain, dyspnoea, cough, reduced breath sounds, hyper-resonance, desaturation, tachycardia and, with tension, hypotension, tracheal deviation and distended neck veins. Symptoms may be delayed.

Red flags.

• Haemodynamic instability.
• Tracheal deviation.
• Saturation under 90%.
• Positive pressure ventilation with new hypotension.

Lung ultrasound (absent lung sliding, lung point) is fast and sensitive. Erect chest radiograph confirms. CT for small pneumothoraces (rarely needed). Tension pneumothorax is a clinical diagnosis requiring immediate decompression.

Differential diagnosis.

• Phrenic nerve palsy.
• Pulmonary embolism.
• Myocardial infarction.
• Pleural effusion or haemothorax.
• Pneumonia.
• Local anaesthetic toxicity.

Oxygen at high flow to saturation 94% to 98%.

• Small (under 2 cm), stable, asymptomatic: observe with oxygen, repeat chest radiograph at 4 to 6 hours, and discharge with advice only when stable.
• Symptomatic or larger: aspiration (needle or catheter, second intercostal space mid-clavicular line or fifth space in the safe triangle) or small bore chest drain.
• Tension: immediate needle decompression (14 gauge cannula, fifth intercostal space anterior axillary line, or second intercostal space mid-clavicular line, with a longer cannula in obesity), then chest drain.
• Avoid nitrous oxide and monitor closely if positive pressure ventilation is needed (prophylactic drain if ventilated).
• Analgesia: paracetamol 1 g orally or IV every 6 hours (maximum 4 g daily; reduce in hepatic impairment or under 50 kg) and ibuprofen 400 mg every 8 hours (maximum 1.2 g daily; avoid in renal impairment and peptic ulcer).

Prevention. Ultrasound direction with needle tip in view, shallow needle path, and careful technique with high risk patients. Warn patients to report breathlessness for 24 hours.

Monitoring. Saturation, respiratory rate and chest radiograph at 4 to 6 hours for high risk blocks.

Referral and escalation. Respiratory or thoracic team for drain management. Critical care for tension.