Background
Digital nerve blocks are important tools for the emergency medicine clinician. Injuries or infections of the digits are extremely common. Adequate analgesia is essential to properly address the presenting condition and to minimize the patient's discomfort. Digital blocks are useful in many scenarios in which local infiltration of an anesthetic would require several injections into the already painful site of injury. Furthermore, local infiltration around the wound may create increased swelling, making the repair more difficult. Several techniques are available for performing digital blocks.
Relevant anatomy
Each digit is innervated by 4 digital nerves. In the upper extremity, the digital nerves arise from the median, ulnar, and radial nerves. The 2 palmar digital nerves innervate the palmar aspect of the digit and the nail bed, whereas the dorsal nerves innervate the dorsum of the digit (see images below). The tibial and peroneal nerves branch off into the digital nerves of the lower extremities, which follow a pattern of distribution analogous to those of the upper extremity. [1]
Indications
Digital blocks are indicated for any minor surgery or procedure of the digits. These include, but are not limited to, the following:
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Large irregular lacerations
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Felon or paronychia
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Digit dislocations or fractures [2]
Contraindications
Contraindications to digital nerve block include:
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Compromised digit circulation
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Infected injection site
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Known allergy to anesthetic
Best Practices
Best practices for digital nerve block include:
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Avoid epinephrine use in the digits; a clamped Penrose drain can be used to limit bleeding.
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Limit the patient’s discomfort by using a smaller needle, injecting slowly, and using small amounts of anesthetics.
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Anesthesia of the great toe is more difficult to achieve and requires 3-sided/4-sided ring blocks.
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Use of sterile technique is essential to limit the risk of introducing infections (especially with the transthecal block).
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Palmar digital nerves.
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Dorsal digital nerves.
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Needle position for web-space block.
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Needle position for transthecal block.
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Modified transthecal block.
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Medial injection for 3-sided digital block.
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Medial to lateral injection for 3-sided digital block.
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Lateral injection for 3-sided digital block.
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Wing block technique.
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Web-space block technique.
Tables
Agent |
Maximum Adult Dose (mg)/Procedure* |
Onset (min) |
Duration |
Lidocaine |
300 |
2-5 |
1-2 h |
Procaine |
500 |
2-5 |
15-45 min |
Bupivacaine |
175 |
2-5 |
4-8 h |
*Administer by small incremental doses. |
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