Can a peripheral nerve block be performed for analgesia in a patient with known radial nerve palsy undergoing Open Reduction Internal Fixation (ORIF) of the humerus, and if so, at what dose of local anesthetic, such as ropivacaine (amino amide local anesthetic) or bupivacaine (amino amide local anesthetic)?

Peripheral Nerve Block in Radial Nerve Palsy for Humerus ORIF

Yes, peripheral nerve blocks can and should be performed for analgesia in patients with known radial nerve palsy undergoing humerus ORIF, using ultrasound-guided technique with lower concentrations of local anesthetic (ropivacaine 0.25-0.5% or bupivacaine 0.25-0.5%) without adjuncts, as pre-existing nerve injury is not a contraindication to regional anesthesia when appropriate monitoring is in place. 1

Key Principle: Pre-existing Neuropathy is Not a Contraindication

The concern about performing nerve blocks in patients with existing nerve injury stems from medicolegal anxiety rather than evidence-based contraindications. The critical distinction is between dense, long-duration blocks versus lower-concentration blocks that preserve some sensory and motor function. 1

Recommended Technique and Dosing

Block Selection

• Perform an interscalene or supraclavicular brachial plexus block to provide analgesia for humerus ORIF, as these approaches effectively cover the surgical site 1
• Use ultrasound guidance to reduce the risk of local anesthetic systemic toxicity, improve accuracy, and allow for reduced volumes 1

Specific Dosing Recommendations

For Ropivacaine:

• Use 0.25-0.5% concentration at volumes of 20-40 mL depending on the specific block approach 2, 3
• Ropivacaine 0.5% provides effective surgical anesthesia with potentially less motor block than bupivacaine 2, 4
• Maximum safe dose: Calculate based on 3 mg/kg without epinephrine (approximately 225 mg for a 75 kg patient) 2

For Bupivacaine:

• Use 0.25-0.5% concentration (avoid 0.75% for peripheral blocks in this context) 5
• Volume of 20-40 mL for brachial plexus approaches 5
• Maximum dose: 175 mg without epinephrine, 225 mg with epinephrine 1:200,000 5
• Administer in incremental doses of 3-5 mL with frequent aspiration to avoid intravascular injection 5

Critical Safety Considerations

Avoid Dense, Long-Duration Blocks

• Do not use high concentrations (bupivacaine 0.75%) or adjuncts (dexamethasone, clonidine) that would create dense blocks significantly exceeding surgical duration 1
• Dense blocks may theoretically worsen nerve injury or complicate postoperative neurological assessment 1

Documentation and Consent

• Document the pre-existing radial nerve palsy thoroughly before performing the block, including specific motor and sensory deficits 1
• Obtain and document verbal consent after explaining that the block will not affect the radial nerve territory (which is already compromised) and discussing the analgesic benefits 1

Monitoring Requirements

• Have resuscitation equipment immediately available with continuous monitoring of vital signs during and after block placement 5
• Test block success thoroughly before proceeding with surgery to minimize risk of conversion to general anesthesia 1

Advantages Over Alternative Techniques

• Peripheral nerve blocks produce fewer physiological consequences and hemodynamic side-effects compared to neuraxial techniques 1
• No sympathectomy-induced hypotension occurs with most peripheral blocks 1
• Opioid-sparing effect is particularly beneficial for reducing respiratory complications and delirium in high-risk patients 1

Common Pitfalls to Avoid

• Do not refuse regional anesthesia solely based on pre-existing neuropathy - this represents outdated practice not supported by evidence 1
• Avoid allowing surgical veto of appropriate analgesia - the anesthesiologist is the expert on pain relief and has the right to offer acceptable analgesic techniques 1
• Do not use continuous catheter techniques with dense concentrations in this setting, as they may complicate neurological assessment 1
• Never perform the block without ultrasound guidance in modern practice, as this increases safety and reduces required volumes 1

Practical Algorithm

1. Document baseline radial nerve function (motor and sensory deficits) 1
2. Calculate maximum safe dose based on patient weight and comorbidities 5
3. Position patient appropriately and prepare ultrasound equipment 6
4. Use ultrasound-guided technique with in-plane needling for visualization 6
5. Inject incrementally (3-5 mL aliquots) with frequent aspiration 5
6. Test block adequacy before surgical incision 1
7. Monitor postoperatively for any changes in neurological status beyond the pre-existing deficit 1