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Peripheral nerve blocks
Each block of the brachial plexus or the leg covers a defined area and brings a defined complication: the closer the block is to the neck, the better it covers the shoulder but the more it affects the phrenic nerve.
Why it matters in the exam
Exam questions describe an operation (shoulder, elbow, hand, knee, foot) and ask which block fits — or describe a complication after a block and ask what happened: breathlessness after an interscalene block (diaphragmatic paralysis), hoarseness, Horner syndrome, a pneumothorax after a supraclavicular block, or a fall after a femoral block. They also ask about intravenous regional anaesthesia (Bier block) and the drug forbidden in it.
The brachial plexus (C5–T1) is blocked at four main levels. The interscalene block covers the shoulder and upper arm but often misses the ulnar territory (C8–T1), and almost always blocks the phrenic nerve on the same side. Ultrasound guidance reduces the volume needed and the risk of LAST and vascular puncture. Sharp pain or high resistance on injection means stop — injection into the nerve can damage it.
Nerve blocks serve both as anaesthesia for surgery and as analgesia afterwards, so they reduce the need for opioids, nausea and delirium in older patients. Before every block breathing, clotting and the sensation and movement of the limb are checked, and existing deficits are documented. In exam questions identify the deciding word — "shoulder", "severe lung disease", "a fall after knee surgery" — and match the block level and the complication to it. After a block that paralyses the leg or the arm the limb is protected from pressure and falls, and the patient is told how long the block is expected to last and what to do when the pain returns.
Key points
- Interscalene → shoulder; price: diaphragmatic paralysis.
- Supraclavicular → the whole arm; price: pneumothorax.
- Axillary → forearm and hand; the musculocutaneous nerve may be missed.
- Knee → adductor canal, which preserves muscle strength.
- Bier → lidocaine; never bupivacaine.
Summary table
| Block | Suits | Main complication or drawback |
|---|---|---|
| Interscalene | Shoulder and upper arm | Same-side diaphragmatic paralysis almost always; Horner, hoarseness |
| Supraclavicular | Arm, elbow, forearm and hand | Pneumothorax; diaphragmatic paralysis less common |
| Infraclavicular and axillary | Elbow, forearm and hand | The musculocutaneous nerve may be missed with the axillary block |
| Femoral / adductor canal | Knee and anterior thigh | Quadriceps weakness and falls; the adductor canal spares strength |
| Popliteal (sciatic) | Ankle and foot | Motor block of the foot |
Free exam questions
באיזה מהחסמים העצביים אין קונטרה אינדיקציה לשימוש באפינפרין במיהול- 1:200,000 1:400,000 ?כתוסף למאלחש (the question as examined, in Hebrew)
- א. Penile Block
- ב. Ankle Block
- ג. Femoral block
- ד. Digital block
איזה מהבאים הוא סיבוך נפוץ הקשור לחסם Interscalene nerve block ? (the question as examined, in Hebrew)
- א. Superior laryngeal nerve neuropathy
- ב. Supraclavicular hematoma
- ג. Horner’s syndrome
- ד. Tracheal puncture
In the full version for subscribers
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Sources
- Miller's Anesthesia, 9th edition (2020) — Peripheral Nerve Blocks and Ultrasound Guidance for Regional Anesthesia
- Morgan & Mikhail's Clinical Anesthesiology, 7th edition (2022) — Peripheral Nerve Blocks
- ASRA Practice Advisory on Local Anesthetic Systemic Toxicity, 2020 — Prevention with ultrasound guidance
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.