What is the risk of ischemia with local anesthetic and 5 micrograms/milliliter (mcg/ml) adrenaline in digital nerve blocks and sound/nail infiltration?

From the Guidelines

The use of local anesthetics with 5 micrograms/milliliter (mcg/ml) adrenaline in digital nerve blocks and nail bed infiltration is generally considered safe with minimal risk of ischemia. Contrary to traditional teaching, modern evidence indicates that properly diluted adrenaline (1:200,000 or 5 mcg/ml) can be safely used in fingers and toes. The historical concern about digital ischemia and necrosis was largely based on case reports from the early 1900s when much higher concentrations were used and when the anesthetics themselves contained toxic additives.

The vasoconstrictive effect of adrenaline at this concentration is temporary and reversible, typically lasting 1-2 hours. The benefit of adding adrenaline includes prolonged anesthesia duration (up to 4-6 hours compared to 1-2 hours without), reduced bleeding in the surgical field, and decreased systemic absorption of the local anesthetic. When performing these blocks, it's essential to use the appropriate concentration, avoid excessive volume, and ensure the patient doesn't have severe peripheral vascular disease, Raynaud's phenomenon, or other conditions that significantly compromise digital blood flow.

Some key considerations for the use of local anesthetics include:

• The maximum safe dose of local infiltrated anesthesia is unknown, but guidelines suggest no more than 4.5 mg/kg of lidocaine and 7.0 mg/kg of lidocaine with epinephrine for adults, and no more than 1.5-2.0 mg/kg of lidocaine and 3.0-4.5 mg/kg of lidocaine with epinephrine for children, as noted in guidelines for the use of local anesthesia in office-based dermatologic surgery 1.
• If concerns about circulation arise after administration, phentolamine can be used as a reversal agent.
• Infiltrative anesthesia may be combined with other forms of local anesthesia for larger or more complex cutaneous procedures, including but not limited to full-face ablative laser resurfacing, combined with topical and nerve block anesthesia, and follicular unit hair transplantation, combined with tumescent local anesthesia, as suggested by guidelines for the use of local anesthesia in office-based dermatologic surgery 1.

It is crucial to follow established guidelines and consider individual patient factors to minimize risks and ensure safe and effective use of local anesthetics with adrenaline in digital nerve blocks and nail bed infiltration.

From the Research

Evidence of Ischaemia with Local Anaesthetic and Adrenaline

• The risk of ischemia with local anesthetic and 5 micrograms/milliliter (mcg/ml) adrenaline in digital nerve blocks and sound/nail infiltration has been studied in several research papers 2, 3, 4, 5, 6.
• A case study published in 2015 reported digital necrosis after local anaesthesia with epinephrine in a 70-year-old woman with a medical history of diabetes mellitus and an ischemic cerebral infarct 2.
• However, a systematic review with meta-analysis published in 2020 found that the use of vasoconstrictors associated with local anesthetics in digital block proved to be a safe and effective technique, with no observed occurrence of ischemia 3.
• Another study published in 1994 found that phentolamine reversal of epinephrine-induced digital vasospasm can be an effective treatment for ischemia caused by accidental injection of epinephrine 4.
• A literature review published in 2015 found that epinephrine 1:100,000-200,000 (5-10 μg/mL) is safe to use in digital nerve blocks in healthy patients, with no reported cases of digital necrosis or gangrene attributable to epinephrine 5.
• A case report published in 2017 described delayed-onset digital ischemia after local anesthetic with epinephrine injection, which was successfully treated with phentolamine reversal 6.

Key Findings

• The use of local anesthetics with epinephrine in digital nerve blocks may pose a risk of ischemic complications, particularly in patients with risk factors for poor peripheral circulation 2, 5.
• However, the majority of studies suggest that the use of vasoconstrictors associated with local anesthetics in digital block is safe and effective, with no observed occurrence of ischemia 3, 5.
• Phentolamine reversal can be an effective treatment for ischemia caused by epinephrine-induced digital vasospasm 4, 6.