Timing and Presentation of Pneumothorax After Interscalene Nerve Block
Pneumothorax after interscalene nerve block most commonly occurs within the first hour of the procedure, with 98% of cases detectable on chest radiographs taken either immediately or at 1 hour post-procedure, and the most common presenting symptom is ipsilateral chest pain accompanied by dyspnea. 1
Timing of Onset
- The vast majority (98%) of pneumothoraces are visible on chest radiographs within the first hour after the procedure, whether taken immediately or at the 1-hour mark 1
- Delayed presentations occurring more than 24 hours after the procedure are documented but remain exceptional, even in higher-risk procedures like lung biopsies 1
- When pneumothorax does occur, it typically presents acutely during or immediately after the block procedure 1
Clinical Presentation
The characteristic symptom pattern includes:
- Ipsilateral chest pain as the primary presenting complaint 1
- Dyspnea (shortness of breath) accompanying the chest pain 1
- Diminished breath sounds on the affected side upon physical examination 1
- In severe cases, patients may develop panic and feel as if their life is in jeopardy, particularly if tension pneumothorax develops 2, 3
Critical Monitoring Period
- Patients must remain in a monitored setting for at least the first hour after the block, as this captures the vast majority of potential pneumothorax complications 1
- Staff should be immediately available to respond if new symptoms develop during this critical window 1
- Chest radiographs should be obtained at least 1 hour post-procedure if pneumothorax is suspected 4
Post-Discharge Instructions
Even after the initial monitoring period:
- Patients must receive explicit instructions to return immediately for any new-onset breathlessness or chest pain 1
- While delayed presentations beyond 24 hours are rare, they have been documented in procedural literature and warrant patient education 1
- This counseling should be part of the informed consent process, though the absolute risk remains very low 1
Clinical Context
The risk of pneumothorax with interscalene blocks is substantially lower than with procedures like transbronchial biopsy (which carries approximately 3.5% risk) 4, making it a rare but recognized complication that requires vigilance primarily in the immediate post-procedure period.