In an HIV‑positive adult patient, how should the local‑anesthetic dose and technique for a peripheral nerve block be adjusted, considering hepatic dysfunction, protease‑inhibitor therapy, low body weight, coagulopathy, infection risk, and pre‑existing peripheral neuropathy?

Peripheral Nerve Block Dosing and Technique Adjustments for HIV-Positive Patients

In HIV-positive adults requiring peripheral nerve blocks, use ultrasound-guided technique with calculated safe doses based on ideal body weight, avoid deep/non-compressible blocks if coagulopathy is present, and carefully assess for pre-existing peripheral neuropathy before proceeding—but HIV status alone does not mandate dose reduction of local anesthetics. 1, 2

Pre-Procedure Assessment: Critical Factors

Baseline Neurological Examination

• Document a complete baseline neurological examination before any block, including motor function (Bromage scale), sensory distribution, and presence of pre-existing neuropathy 3
• HIV-associated distal symmetric polyneuropathy (DSP) occurs in up to 57% of HIV-infected individuals, with 38% experiencing neuropathic pain 4
• Pre-existing neuropathy is a relative contraindication requiring careful risk-benefit assessment, as distinguishing new nerve injury from progression of HIV-related neuropathy becomes difficult 5, 4

Coagulation Status

• Obtain platelet count, INR, and detailed antiplatelet/anticoagulant medication history 2
• Active P2Y12 inhibitor therapy (clopidogrel, prasugrel, ticagrelor) is an absolute contraindication for deep/non-compressible blocks unless discontinued 5-7 days prior 2
• Coagulopathy that cannot be corrected is an absolute contraindication 2
• Aspirin monotherapy is a relative contraindication for deep blocks but may proceed for superficial blocks with favorable risk-benefit ratio 2

Hepatic Function and Body Weight

• Assess liver function tests in all HIV patients, particularly those on protease inhibitors 1
• Calculate ideal body weight for local anesthetic dosing—do not use actual body weight in cachectic or obese patients 1, 6
• Reduce doses for patients with hepatic dysfunction, as local anesthetic metabolism is impaired 6

Infection Risk

• Active infection at the injection site is an absolute contraindication 2, 7
• HIV status alone does not increase infection risk from nerve blocks when proper aseptic technique is used 1

Local Anesthetic Dosing Strategy

Dose Calculation Principles

• Use ideal body weight, not actual body weight, for all dose calculations 1, 6
• Calculate and document the maximum safe dose before starting the procedure 1, 2
• For lidocaine without epinephrine: maximum 4.5 mg/kg ideal body weight 6
• For lidocaine with epinephrine: maximum 7 mg/kg ideal body weight 6
• No specific dose reduction is required for HIV status alone—adjust only for hepatic dysfunction, low body weight, or elderly/debilitated status 6, 8, 9

Volume vs. Concentration Considerations

• Mass of local anesthetic (total mg), not volume or concentration, primarily determines block success and duration 10
• Use lower concentrations with larger volumes for sensory-predominant blocks 10
• Use higher concentrations with smaller volumes for motor blockade 10

Drug Interactions with Protease Inhibitors

• Protease inhibitors do not significantly alter local anesthetic pharmacokinetics 8
• Calcium channel blockers should be avoided in patients on protease inhibitors due to hypotension risk, but this does not affect local anesthetic choice 1

Technique Selection Algorithm

Step 1: Assess Respiratory Function

• Avoid blocks that impair respiratory function (interscalene, supraclavicular) in patients with pre-existing respiratory compromise 1, 2
• Choose axillary or infraclavicular approaches over supraclavicular for brachial plexus blocks 1
• Superior trunk block or alternatives are preferred over interscalene block 1

Step 2: Evaluate Coagulation and Choose Block Depth

• If coagulopathy or active antiplatelet therapy: perform only superficial, compressible blocks 2
• If normal coagulation: deep blocks are acceptable with ultrasound guidance 2
• Deep blocks carry similar but lower risk than neuraxial techniques for compressive hematoma 1

Step 3: Ultrasound Guidance is Mandatory

• All peripheral nerve blocks in HIV patients must be performed with ultrasound guidance to reduce local anesthetic systemic toxicity (LAST) risk 1, 2, 7
• Ultrasound allows visualization of needle placement and real-time injection, reducing required doses 10

Step 4: Avoid Concurrent Local Anesthetic Techniques

• Do not perform a peripheral nerve block within 4 hours of neuraxial anesthesia or another nerve block 1
• Do not start intravenous lidocaine within 4 hours after any nerve block 1
• Cumulative local anesthetic doses from multiple sites increase LAST risk 1

Perineural Adjuvants: Risk-Benefit Assessment

Dexamethasone

• Avoid dexamethasone as a perineural adjuvant in HIV patients due to immunosuppression risk 1
• The opioid-sparing benefit does not outweigh the risk of further immune compromise 1

Alpha-2 Agonists (Clonidine, Dexmedetomidine)

• Use with extreme caution due to risks of sedation, bradycardia, and hypotension 1
• These effects may be exacerbated in patients with autonomic neuropathy (common in HIV) 5

Post-Procedure Monitoring Requirements

Motor and Sensory Function

• Assess motor function every 1-2 hours until complete resolution using the Bromage scale 3
• Document expected dermatomal sensory distribution immediately post-block and track resolution 3
• If motor or sensory block persists >12 hours for standard agents or >24 hours for long-acting agents, arrange urgent imaging (MRI or ultrasound) to exclude compressive hematoma 3

Warning Signs Requiring Urgent Evaluation

• Progressive motor weakness rather than gradual improvement 3
• Expansion of sensory deficit beyond expected distribution 3
• Severe pain or new paresthesias outside the blocked area 3
• Do not attribute prolonged block to "individual variation" without investigating for complications 3

Patient Education

• Provide written discharge instructions with anticipated block duration, activity restrictions, warning signs, and 24-hour contact number 3
• Inform patients that sensation typically returns within 4-12 hours for standard agents and up to 24 hours for long-acting agents 3

Critical Safety Requirements

Immediate Resuscitation Preparedness

• Lipid emulsion 20% must be readily available wherever peripheral nerve blocks are performed 1, 2
• All staff must know the location of lipid emulsion and LAST treatment protocols 1
• Immediate resuscitation equipment (airway, oxygen, vasopressors) must be available 2

Operator Experience

• An experienced operator must perform all nerve blocks in HIV patients, given the complexity of assessing pre-existing neuropathy and increased medicolegal risk 2, 7

Common Pitfalls to Avoid

• Do not assume HIV-related neuropathy is a contraindication—it is a relative contraindication requiring documentation and informed consent 5, 4
• Do not use actual body weight for dose calculations in cachectic HIV patients—this leads to overdosing 1, 6
• Do not perform deep blocks in patients on antiplatelet therapy without appropriate discontinuation periods 2
• Do not combine multiple local anesthetic techniques within 4 hours of each other 1
• Do not use immunosuppressive adjuvants (dexamethasone) in immunocompromised patients 1