What is the recommended anesthesia technique for an adult patient with no significant medical history undergoing upper limb surgery using an ultrasound-guided supraclavicular brachial plexus block?

Ultrasound-Guided Supraclavicular Brachial Plexus Block: Step-by-Step Technique

Ultrasound guidance is mandatory for supraclavicular brachial plexus blocks to reduce local anesthetic systemic toxicity risk and improve block success rates. 1, 2

Pre-Procedure Assessment and Contraindications

Absolute Contraindications

• Active P2Y12 inhibitor therapy without 5-7 day discontinuation 2
• Therapeutic anticoagulation unless appropriately reversed 2
• Uncorrectable coagulopathy or bleeding disorders 2
• Patient refusal 2
• Active infection at injection site 2

High-Risk Features to Screen

• Body habitus (obesity increases failure risk) 3
• Preexisting neurologic symptoms 2
• Diabetes mellitus 2, 3
• Peripheral vascular disease 2
• Alcohol dependency 2
• Arthritis 2
• Preoperative systolic blood pressure >170 mmHg (predicts need for supplemental anesthesia with 89% specificity) 3

Note: Aspirin monotherapy may proceed only if benefit/risk ratio is favorable; dual antiplatelet therapy requires careful assessment. 2

Equipment Preparation

Required Equipment

• High-frequency linear ultrasound probe (13 MHz or higher recommended) 4
• 22-gauge needle (2 3/8 inch or 8.89 cm) 1
• Immediate resuscitation equipment including lipid emulsion for local anesthetic systemic toxicity 2
• Sterile ultrasound gel and probe cover 5
• Local anesthetic solution 6

Local Anesthetic Dosing

• Ropivacaine 0.5% (5 mg/mL): Use up to 275 mg total dose 6
• Ropivacaine 0.75% (7.5 mg/mL): 30 mL (225 mg) for supraclavicular approach provides median anesthesia duration of 11.4-14.4 hours 6
• Calculate safe dose based on patient weight (ropivacaine 2 mg/kg maximum) 5
• Supraclavicular blocks consistently show higher success rates (92%) compared to axillary blocks (56-86%) 6

Patient Positioning

Optimal Position

• Supine or semi-sitting position 5
• Head turned away from the side to be blocked 5
• Arm at side or slightly abducted (limit to ≤90° to prevent brachial plexus injury) 2
• Use padded armboards to decrease upper extremity neuropathy risk 2

Critical Safety Point: Periodically assess upper extremity position during procedures and avoid shoulder braces in steep head-down positioning. 2

Ultrasound Scanning and Anatomical Identification

Probe Placement

• Position high-frequency linear probe in supraclavicular fossa 5
• Place probe parallel and superior to clavicle 5
• Identify subclavian artery as primary landmark 5

Key Anatomical Structures to Identify

• Subclavian artery (pulsatile, anechoic structure) 5
• Brachial plexus (cluster of hypoechoic circles lateral and superficial to artery, appearing as "grapes") 5
• First rib (hyperechoic line deep to plexus) 5
• Pleura (hyperechoic line moving with respiration, deep to first rib) 5

Ultrasound provides real-time visualization of underlying structures and spread of local anesthetic, significantly reducing complications. 5

Needle Insertion Technique

In-Plane Approach

• Use in-plane lateral-to-medial approach for optimal needle visualization 1
• Insert needle lateral to probe 5
• Advance needle through middle scalene muscle toward brachial plexus 1
• Maintain continuous visualization of needle tip throughout advancement 5

Target Position

• Position needle tip at corner pocket (junction of first rib and subclavian artery) or within the neural cluster 5
• Avoid direct contact with individual nerve structures 5
• Ensure needle tip is not intravascular by aspirating before injection 5

Local Anesthetic Injection

Injection Technique

• Aspirate before injection to rule out intravascular placement 5
• Inject 1-2 mL test dose and observe for spread pattern 5
• For ropivacaine 0.75%: inject 30 mL (225 mg) total volume 6
• For ropivacaine 0.5%: inject 20-40 mL depending on approach 7, 5
• Inject slowly with intermittent aspiration 5
• Observe real-time spread of local anesthetic surrounding the plexus (should appear as hypoechoic fluid) 5

Optimal Spread Pattern

• Local anesthetic should surround brachial plexus in crescent or circumferential pattern 5
• If spread is inadequate, reposition needle and inject additional aliquots 5

Supplemental Coverage

Medial Arm Coverage

• For procedures involving medial arm: infiltrate additional 10 mL local anesthetic along subcutaneous fascia of proximal medial aspect of arm (covers intercostobrachial nerve not blocked by supraclavicular approach) 7

Block Assessment and Onset Time

Expected Onset

• Median onset of sensory block ranges from 10-45 minutes depending on nerve distribution 6
• Allow extra onset time (minimum 20-30 minutes) before surgical incision to reduce risk of conversion to general anesthesia 1
• Ultrasound guidance significantly improves onset time compared to landmark techniques 4

Testing Block Success

• Thoroughly test block success before proceeding with surgery to minimize risk of emergent conversion to general anesthesia 1
• Test all nerve distributions: radial, median, ulnar, musculocutaneous 6
• Assess both sensory (pinprick, cold sensation) and motor function 5, 4
• Median duration of sensory blockade: 3.7-8.7 hours with ropivacaine 0.5% 6
• Median duration of anesthesia: 11.4-14.4 hours with ropivacaine 0.75% 6

Monitoring and Safety

Intraoperative Monitoring

• Avoid excessive or deep sedation to reduce need for airway manipulation 1
• Monitor respiratory function (supraclavicular blocks have lower risk of phrenic nerve palsy compared to interscalene blocks, but still possible) 1
• Have patient wear surgical facemask if performing under sedation 1

Common Complications to Monitor

• Horner's syndrome (transient, 10% incidence) 8
• Phrenic nerve block (60% incidence with some approaches) 8
• Pneumothorax (rare with ultrasound guidance) 5, 8
• Vascular puncture (reduced with ultrasound visualization) 5
• Local anesthetic systemic toxicity (have lipid emulsion immediately available) 2

Critical Safety Point: Supraclavicular blocks are classified as deep/non-compressible blocks with elevated bleeding risk; patient harm includes airway obstruction from hematoma compression and vascular occlusion. 2

Special Considerations

High-Risk Scenarios

• Elbow surgery shows highest prevalence (41%) of requiring supplemental local anesthesia 3
• Obese patients have higher failure rates 3
• Patients with preoperative systolic BP >170 mmHg require additional anesthesia in 36% of cases 3
• Consider alternative approaches (axillary or infraclavicular) in patients with respiratory compromise to avoid phrenic nerve involvement 1

Adjuvants

• Single dose of intravenous dexamethasone increases analgesic duration of block and provides anti-emetic effects 1
• Balance risks of perineural adjuvants (immunosuppression with dexamethasone, sedation/bradycardia with clonidine) against benefits 1