What are the guidelines for administering a bupivicaine (local anesthetic) ring block to adult and pediatric patients with various medical conditions, such as bleeding disorders or cardiovascular disease, undergoing surgical procedures on the extremities?

Bupivacaine Ring Block Administration

Bupivacaine ring blocks are safe and effective for digital and extremity procedures when administered at appropriate concentrations and doses, with the addition of epinephrine now considered safe even in digits, contrary to historical teaching.

Adult Dosing and Concentration

For adult ring blocks, use bupivacaine 0.25% at a maximum dose of 2.5 mg/kg (equivalent to 1 ml/kg of 0.25% solution) without epinephrine, or up to 225 mg total with epinephrine 1:200,000. 1

• The FDA recommends fractional (incremental) dosing when feasible, avoiding rapid injection of large volumes 1
• For dental ring blocks specifically, the average dose is 1.8 mL (9 mg) per injection site, with a maximum total of 90 mg (ten 1.8 mL injections) for a healthy adult in a single sitting 1
• Always calculate total dose in mg/kg to ensure it remains below toxic threshold 2

Concentration Selection

• 0.25% bupivacaine produces incomplete motor block, making it ideal for procedures not requiring muscle relaxation 1
• 0.5% provides motor blockade but may have inadequate muscle relaxation for operations requiring complete relaxation 1
• The lowest effective concentration should be employed to minimize toxicity risk 1

Pediatric Dosing

For pediatric patients, use bupivacaine 0.25% at 1.0 ml/kg for peripheral nerve blocks and wound infiltration, with a maximum dose of 2.5 mg/kg. 3

• Bupivacaine is not recommended for pediatric patients younger than 12 years in dental applications 1
• For other peripheral nerve blocks in children, the European Society for Paediatric Anaesthesiology supports doses of 0.2-0.5 ml/kg of 0.25% bupivacaine 3

Epinephrine Use: Debunking Historical Dogma

The addition of epinephrine to local anesthesia is safe and recommended for use on digits, hands, feet, ear, and nose, with Level I and II evidence refuting the historical contraindication. 3

• Multiple systematic reviews and randomized controlled trials found no cases of digital necrosis with epinephrine use 3
• Benefits include longer duration of anesthesia, faster onset, reduced need for tourniquet, and decreased peak blood levels 3
• Use the lowest effective concentration of epinephrine (typically 1:100,000 to 1:200,000) 3

Epinephrine in Special Populations

Patients with stable cardiac disease may receive local anesthesia with epinephrine; consult cardiology if uncertain of the patient's ability to tolerate epinephrine. 3

• For pregnant women, epinephrine-containing local anesthesia may be used in small amounts 3
• Elective procedures should be postponed until after delivery 3
• Urgent procedures should be delayed until the second trimester when possible 3
• Consult with the patient's obstetrician when in doubt 3

Bleeding Disorders Considerations

While the provided evidence does not specifically address bleeding disorders for ring blocks, general principles apply:

• Ring blocks are infiltrative techniques with minimal bleeding risk compared to deep nerve blocks
• The addition of epinephrine provides hemostasis, which may be particularly beneficial in patients with mild bleeding disorders 3
• For patients with significant coagulopathy, consultation with hematology is prudent before any invasive procedure

Pain Reduction Strategies

Pre-injection of buffered lidocaine solution is recommended to reduce the pain of bupivacaine infiltration. 3

• The addition of sodium bicarbonate to local anesthetic (particularly lidocaine with epinephrine) is strongly recommended (Level A) to decrease injection pain 3
• This buffering technique has Level I and II evidence supporting its use 3

Safety Protocols and Common Pitfalls

Always aspirate before injection to avoid intravascular administration. 2

Critical Safety Measures:

• Reduce doses for elderly, debilitated patients, and those with cardiac or liver disease 1
• Elderly patients with hypertension are at increased risk for hypotension 1
• Monitor for signs of local anesthetic systemic toxicity (LAST), particularly in pediatric patients where continuous infusions have been reported to cause seizures and cardiovascular abnormalities 1
• Consider using a test dose with epinephrine to detect intravascular injection 2

Maximum Dose Calculations:

• Without epinephrine: 175 mg total or 2.5 mg/kg 1
• With epinephrine 1:200,000: 225 mg total 1
• These doses may be repeated up to once every three hours 1
• Total daily dose should not exceed 400 mg until further experience is gained 1

Duration and Efficacy

• Bupivacaine provides prolonged anesthesia compared to shorter-acting agents 1
• The addition of epinephrine further prolongs the anesthetic effect 3
• Research demonstrates that continuous infusions of 0.25% bupivacaine at 5 mL/h can provide effective postoperative analgesia for up to 48 hours after extremity surgery 4

Contraindications

Bupivacaine 0.75% is contraindicated for obstetrical anesthesia. 1

• Bupivacaine is contraindicated for obstetrical paracervical blocks 1
• Not recommended for intravenous regional anesthesia (Bier Block) 1
• The 0.75% concentration should not be used for ring blocks as it provides unnecessary motor blockade 1