What is a digital nerve block?
A digital nerve block is a procedure to anesthetize the fingers or toes (digits) by injecting an anesthetic solution at the base of the digit. The injection is widely used for local anesthesia, especially in the emergency department, where people often come in with digital injuries.
Several approaches are used for a digital nerve block, depending on the treatment performed.
- Web space block: Injection in the web space between the fingers.
- Transthecal block: Injection in the palm, just below the fingers.
- Three-sided digital block: Injection at the base of the toe, on the top and both sides of the toe.
- Four-sided ring block: Along with the three-sided digital block, one more injection under the toe.
- Wing block: injection below the nail base for anesthetizing only the fingertip and nail.
Why is a digital nerve block performed?
Digital nerve block has several advantages over a local anesthetic injection, for digital injuries and treatment. The merits include
- Rapid anesthetic effect
- Lower volume of anesthetic solution used
- A single injection is usually enough except in the case of the big toe, where several injections to the injury site are necessary and may cause more trauma
- No risk of direct trauma to blood vessels and nerves (neurovascular bundles)
Digital nerve block is administered for
- Providing immediate pain relief
- Treatment of
- Removal of the nail plate
- Drainage of blood out of a hematoma under the nail (subungual)
- Removal of an entrapped ring or other jewelry
Removal of foreign bodies
Digital nerve block is not administered when
Digital blood circulation is impaired
There is infection in the injection site
There is known allergy to the anesthetic
How is a digital nerve block performed?
For digital nerve blocks, the doctors usually avoid using anesthetic agents with epinephrine, which is the norm for local anesthesia. This is to reduce the risk of restriction of blood supply (ischemia) to the tissues, because epinephrine constricts the blood vessels and may cause tissue death (infarction).
The doctor may choose one of the following anesthetic agents depending on the length of time that the anesthesia is required:
- The patient lies on a bed with the hand or foot appropriately positioned for treatment.
- The injection site is cleaned with antiseptic solution and made sterile.
- Inserts the needle into the skin at the injection site.
- Aspirates the needle to ensure that it is not inside a blood vessel.
- Injects approximately 1ml of the anesthetic, forming a small bump (wheal) to block the digital nerve.
- Withdraws the needle.
- Repeats the procedure if more injections are required.
- Waits for up to 10 minutes for the nerve block to take effect.
- Administers one more injection if anesthesia is inadequate.
The patient may feel brief pain during needle insertion. The intensity of pain may vary depending on the condition treated and the area where the injection is administered. Web space block is probably the least painful, while transthecal block is more painful as it is injected on the sensitive surface of the palm.
What are the risks and complications of a digital nerve block?
Risks are minimal with a digital nerve block. Potential complications include the following:
- Pain at injection site
- Infection at injection site, more likely with transthecal block
- Undiagnosed wound infection, because presence of the anesthetic agent may lead to false-negative culture results
- Slower wound healing
- Injection into a blood vessel leading to systemic toxicity
- Nerve injury or neurotoxicity
- Persistent tingling sensation (paresthesia)
- Allergic reaction to the anesthetic agent
- Sudden drop in blood pressure and heart rate (vasovagal syncope)