Supraclavicular, infraclavicular and axillary blocks
Stem
A 63-year-old man, 92 kg, with severe COPD (FEV1 42% of predicted, home oxygen at night) needs open reduction and internal fixation of a distal radius and ulna fracture. The surgeon plans an upper-arm tourniquet for about 2 hours. He is anxious about "being put to sleep" after a prolonged ICU stay with a COPD exacerbation last winter.
Question
How would you anesthetize this patient, and which brachial plexus block would you choose?
Ideal answer
HeadlineAn ultrasound-guided infraclavicular block with light sedation, avoiding a general anesthetic and a paralyzed hemidiaphragm: he has little reserve.
- No interscalene or supraclavicular block: supraclavicular still blocks the phrenic nerve in roughly a third to two-thirds of patients;1 below-elbow surgery lets me go distal.
- Infraclavicular: 20 to 30 mL posterior to the axillary artery. The three cords surround it under pectoralis minor; I watch for U-shaped spread, probe lateral to the pleura.2
- Axillary is equally good: median, ulnar and radial nerves around the artery, the musculocutaneous injected separately in the coracobrachialis.3
- Subcutaneous ring across the medial upper arm, because the intercostobrachial nerve (T2) lies outside the plexus, so neither block covers the tourniquet.1
- Within the maximum dose for 92 kg, small aspirated increments, against intravascular toxicity; lipid emulsion in the room, supplemental oxygen, watching his work of breathing and CO2.
Breaking down the answer
- Lead with the lung — interscalene block causes hemidiaphragmatic paresis in 68–88%;4 supraclavicular block still causes it in 36–67%.1 Matching the block to the patient, not just the surgery, is the judgment examiners grade.
- Infraclavicular for cords and catheters — the chest wall muscles stabilize a catheter, so it is the approach for prolonged infusions; the target is usually 3–5 cm deep.2 Pneumothorax remains possible, which is why the probe stays lateral to the pleura.
- Axillary for the safest geometry — it is superficial and compressible and avoids pneumothorax and diaphragmatic paresis,2 but it misses the musculocutaneous nerve unless I inject it separately.3
- Supraclavicular when the lungs are normal — reliable anesthesia of the whole arm with 20–30 mL; pneumothorax under 1 in 1000 and Horner syndrome about 1%.1 I would choose it in a healthy patient for speed.
Follow-up question
Ninety seconds after you finish the infraclavicular injection, he becomes agitated, says his mouth tastes of metal, and then has a generalized seizure. His heart rate is 48 with wide QRS complexes. What do you do?
Follow-up answer
HeadlineLocal anesthetic systemic toxicity, CNS and cardiac. I stop injecting, call for help and the LAST kit, and tell the surgeon we are not starting.
I give 100% oxygen and ventilate, because hypoxia and acidosis worsen toxicity, and stop the seizure with a benzodiazepine. 20% lipid emulsion now: for 92 kg, about 100 mL over 2–3 minutes, then about 250 mL over 15–20 minutes, under 12 mL/kg in total.5 If he arrests, CPR with small epinephrine doses under 1 mcg/kg, and no vasopressin, calcium-channel blockers, beta-blockers or more local anesthetic.5 I alert the nearest bypass team early, reassess rhythm and pressure continuously, and monitor him for several hours after recovery.
Pitfalls that cost points
- Treating LAST like ordinary cardiac arrest with standard epinephrine doses and no lipid.
- Doing an axillary block and leaving the musculocutaneous nerve unblocked.
Rapid-fire
Q: Where are the cords relative to the axillary artery? A: Lateral, posterior and medial, named for that relationship, with injection aimed posterior to the artery.2
Q: Where does the musculocutaneous nerve lie in the axilla? A: Between biceps and coracobrachialis or within coracobrachialis, lateral to the artery.3
Q: What is the axillary block good for? A: Elbow, forearm, wrist and hand surgery; it is unreliable above the elbow.3
Q: Where is the pleura in a supraclavicular block? A: Medial to the first rib; the trunks and divisions lie on the rib lateral to the subclavian artery.1
Numbers to know
| Item | Value |
|---|---|
| Phrenic block, supraclavicular | 36–67%1 |
| Hemidiaphragmatic paresis, interscalene | 68–88%4 |
| Pneumothorax, supraclavicular | <1 in 10001 |
| Infraclavicular volume, depth | 20–30 mL; 3–5 cm2 |
| Axillary perivascular volume | 20–30 mL total3 |
| Lipid bolus, >70 kg | ~100 mL over 2–3 min, then ~250 mL over 15–20 min5 |
Links
- Interscalene, supraclavicular, infraclavicular, axillary, Interscalene block and its complications, Local anesthetic systemic toxicity, COPD and reactive airway disease
- Atlas: Interscalene, supraclavicular, infraclavicular, axillary
- ASRA Checklist for Treatment of Local Anesthetic Systemic Toxicity (2020)
Sources
- 1.Ultrasound-Guided Supraclavicular Brachial Plexus Block (Anaesthesia Tutorial of the Week) · WFSA · resources.wfsahq.orgPhrenic block 36-67%; pneumothorax <1:1000; intercostobrachial (T2) usually spared; 20-30 mL.
- 2.Ultrasound-Guided Infraclavicular Brachial Plexus Nerve Block · NYSORA · nysora.com
- 3.Axillary Block · OpenAnesthesia · openanesthesia.org
- 4.Phrenic-sparing alternatives to interscalene block · NYSORA · nysora.comHemidiaphragmatic paresis 68-88% with interscalene block; supraclavicular approaches may preserve pulmonary function better.
- 5.Checklist for Treatment of Local Anesthetic Systemic Toxicity · ASRA, 2020 · asra.com
Facts on this page were checked against these sources on Oct 15, 2026. Guidelines change; confirm doses against current institutional protocols.