Ankle Block Volume Recommendations
For ankle blocks in foot and ankle surgery, use 10-15 mL total volume of local anesthetic distributed across the five nerves, with 2-3 mL per nerve being sufficient for effective blockade.
Volume Distribution Strategy
The ankle block targets five sensory nerves supplying the foot, and the total volume should be distributed strategically:
- Deep nerves (tibial and deep fibular): 2-3 mL per nerve for perineural injection 1
- Superficial nerves (superficial fibular, saphenous, sural): 2-3 mL per nerve for subcutaneous infiltration 1
- Total volume: 10-15 mL is adequate for complete foot anesthesia 2, 1
Local Anesthetic Selection and Concentration
Bupivacaine 0.25-0.5% is the most commonly used single long-acting local anesthetic for ankle blocks, providing excellent surgical anesthesia and prolonged postoperative analgesia 2.
Alternative options include:
- Ropivacaine 0.75%: Effective at lower volumes (6-9 mL for popliteal sciatic block) 3
- Levobupivacaine 0.25%: Similar efficacy to bupivacaine with potentially improved safety profile 4, 5
Maximum Safe Dosing
When calculating total volume, always verify you remain below toxic thresholds:
- Bupivacaine without epinephrine: Maximum 1.3 mg/kg 4
- Bupivacaine with epinephrine: Maximum 3.0 mg/kg 4
- For 0.25% bupivacaine: This equals 2.5 mg/mL, so 15 mL = 37.5 mg total dose 4
Technical Approach Considerations
Ultrasound-guided ankle blocks demonstrate superior efficacy compared to anatomic landmark-guided techniques, particularly when performed by less-experienced practitioners 6.
Key performance metrics:
- USG technique success rate: 84% surgical anesthesia 6
- ALG technique success rate: 66% surgical anesthesia 6
- Overall success rates: 88-94% across techniques 1
- Patient satisfaction: 66-95.8% 2
The ultrasound-guided approach reduces the need for:
- Supplemental local anesthesia (5% vs 10% with ALG) 6
- Unplanned general anesthesia (7% vs 17% with ALG) 6
- Postoperative opioid requirements 6
Clinical Outcomes
Ankle blocks provide excellent postoperative analgesia with low VAS pain scores at 24 hours postoperatively 2. The analgesic effect continues well into the postoperative period, minimizing immediate pain scores 2.
Common Pitfalls to Avoid
- Excessive volume: Using more than 15-20 mL total increases risk of local anesthetic systemic toxicity without improving block success 3, 2
- Inadequate distribution: Failing to block all five nerves leads to incomplete anesthesia requiring supplementation 6, 1
- Wrong concentration: Using concentrations below 0.25% may result in inadequate surgical anesthesia 2
Safety Monitoring
Major complications are rare but include:
- Block failure requiring conversion to general anesthesia 2
- Transient nerve injuries (uncommon) 2
- Local anesthetic systemic toxicity (rare with appropriate dosing) 4
Always have lipid emulsion and resuscitation equipment immediately available when performing any peripheral nerve block 7.