Is it safe to administer 3 mL of lidocaine (1% local anesthetic) with epinephrine (adrenergic receptor agonist) for a digital block of a first toe?

Safety of Lidocaine with Epinephrine in Digital Block of the First Toe

Using 3 mL of lidocaine 1% with epinephrine for a digital block of the first toe is safe and does not pose a risk of digital necrosis. 1

Evidence Supporting Safety of Epinephrine in Digital Blocks

• Multiple systematic reviews and randomized controlled trials have demonstrated that adding epinephrine to local infiltrative anesthesia is safe for use in digits, hands, and feet 1
• The historical concern about digital necrosis with epinephrine use has been thoroughly refuted by extensive research 1
• No cases of necrosis were reported in studies examining epinephrine use in digits, and its use resulted in less need for tourniquets plus faster onset and longer duration of anesthesia 1
• The American Academy of Dermatology guidelines specifically recommend adding epinephrine to local anesthesia when cutaneous surgery is performed on digits 1

Benefits of Using Epinephrine in Digital Blocks

• Epinephrine extends the duration of anesthesia (90-200 minutes vs. 30-60 minutes without) 2
• Reduces the volume of anesthetic needed (2.2 ± 0.4 mL with epinephrine vs. 3.1 ± 0.6 mL without) 3
• Decreases postoperative drainage period (11.1 ± 2.5 days with epinephrine vs. 19.0 ± 3.8 days without) 3
• Provides better hemostasis during the procedure 1

Dosage Considerations

• The maximum safe dose of lidocaine with epinephrine for adults is 7.0 mg/kg 1, 2
• For a 70 kg adult, this would allow up to 490 mg (49 mL of 1% solution)
• 3 mL of 1% lidocaine contains only 30 mg of lidocaine, well below the toxic threshold 4
• Always use the lowest effective concentration and dose that will produce the desired result 4

Important Precautions

• While extremely rare, epinephrine-induced digital vasospasm can occur 5
• Risk factors for vasospasm include Raynaud's syndrome, peripheral vascular disease, and other conditions affecting digital circulation 6, 7
• In patients with these risk factors, consider using plain lidocaine without epinephrine 7
• Phentolamine can be used as a rescue medication if digital ischemia occurs following epinephrine administration 5

Historical Context

• The prohibition against using epinephrine in digits was based on case reports from the early 20th century involving older anesthetic compounds (cocaine, procaine) and non-standardized mixing methods 7, 8
• No cases of digital necrosis have been reported with the use of commercial lidocaine-epinephrine mixtures 7
• A comprehensive review found 48 cases of digital gangrene after anesthetic blocks from 1880 to 2000, but only 21 involved epinephrine, and all had confounding factors such as hot soaks, tight tourniquets, or infection 8

Conclusion

The use of 3 mL of lidocaine 1% with epinephrine for a digital block of the first toe is safe and offers significant advantages over plain lidocaine, including longer duration of anesthesia, better hemostasis, and reduced need for tourniquet use 1, 3.