Digital nerve block is a simple procedure that can be performed to provide immediate anesthesia for a multitude of injuries and procedures, such as fractures, dislocations, laceration repair, fingernail removal, or drainage of infections. It is one the most commonly performed nerve blocks performed in the emergency department due to its wide variety of use and efficacy. The digital nerve block is generally superior to local infiltration due to the reduced amount of anesthetic required. This is of importance as only a limited volume of anesthetic is tolerated in the restricted space of the digits. It is also considered to be superior to intravenous and oral medications as it acts locally and therefore has a lower liklihood of systemic adverse effects.
In order to properly perform this procedure, healthcare providers must have thorough knowledge of the regional anatomy. Digital nerve blocks are intended to anesthetize specific nerves that originate at the wrist from the deep branches of the median, radial, and ulnar nerves. If holding the palm downward and looking down the fingertip toward the hand, there are both dorsal and palmar nerves. The dorsal set of nerves run alongside the digit at the 10- and 2-o'clock positions, while the palmar set of nerves travel at the 4- and 8-o'clock positions (see attached image). The palmar cutaneous branch of the median nerve supplies the palmar surface of digits 1-3, the palmar radial surface of digit 4, and the dorsal nailbed of these same digits to approximately the DIP joint. The palmar cutaneous branch of the ulnar nerve supplies the ulnar half of digit 4 on both the palmar and dorsal surfaces, as well as the entirety of digit 5. These nerves are known as the palmar digital nerves. The superficial branch of the radial nerve supplies the dorsal surface of digits 1-3 to approximately the DIP and the dorsal radial surface of digit 4. Anatomical knowledge of digital nerve innervations is of clinical relevance due to multiple nerves providing sensation to each finger, in some instances requiring multiple sites of anesthetic to provide adequate analgesia.
Indications for digital nerve block include:
Contraindications to digital nerve block include, but are not limited to: patient refusal, overlying infection at the site of injection which could result in innoculation of a deeper or intravascular infection, distortion of landmarks, or allergy to local anesthetics. Digital blocks are commonly taught to be performed without Epinephrine due to risk of vasoconstriction leading to distal necrosis, however, recent studies provide no evidence of this occurrance.
Required equipment for this procedure include:
The anesthetic choice should be tailored to the length of desired analgesia. The most commonly used anesthetics are: Lidocaine (1.5-2 hours), Lidocaine with Epinephrine (2-6 hours), Bupivicaine (2-4 hours), and Mepivacaine (3-5 hours).
Digital blocks only require one provider in a cooperative patient. For uncooperative or pediatric patients, providers should consider an assistant to help stabilize.
The patient should be educated about the procedure and informed about risks and benefits. Informed consent should be obtained before the start of the procedure. Required equipment should be brought to the bedside.
A dorsal approach is preferred due to the thinness of the skin in this location and decreased sensitivity.
The procedure is performed in the following steps:
Complications of digital nerve block include, but are not limited to: infection, bleeding, increased pain, vascular injection of anesthetic, nerve injury including neuropraxia or neurolysis, local anesthetic systemic toxicity (LAST), and allergic reaction.
Clinicians have a multitude of ways to provide anesthesia to patients in pain so they may perform maneuvers or procedures effectively while allowing for minimal discomfort to the patient. Anesthesia may be approached in a multimodal manner as there are multiple areas that one may target the transmission of pain as it propagates from the site of injury to the cerebral cortex. One such modality of pain relief is by targeting the peripheral nerve, which serves to transmit pain signaling from tissues. The tissue in which the injury occurred may be targeted by anesthetics to limit the transduction of pain as can the peripheral nerves which innervate the tissue and serves to transmit pain signals to the cerebral cortex.
Targeting the transduction of pain from the level of the tissue may be accomplished by use of drugs that impede the pain signaling pathway, for example, opioids, NSAIDs, or local infiltration of the injured tissue with an anesthetic. A disadvantage of using local infiltration is that the anesthetic is injected directly and/or indirectly to tissues and distorts the anatomy that the clinician needs to visualize to perform repairs. This technique is also associated with decreased patient comfort due to the amount of pain experienced during this procedure as a large amount of anesthetic is required for therapeutic effect.
The peripheral nerve may also be targeted by systemic analgesic agents such as opioids, TCAs, or other dissociative drugs, but the nerve may also be directly targeted by use of anesthetic agents in a technique known as a nerve block. Nerve blocks may be utilized proximal to the area of injury to provide a larger region of anesthesia, or it may be used regionally for targeted anesthesia closer to the injured tissue. A regional nerve block, and in particular the digital nerve block, is one such technique that allows for targeted anesthesia and is typically tolerated better by patients than local wound infiltration and allows for a large area of anesthesia in relation to the amount of anesthetic required.
The digital nerve block can be considered for use in repair of various injuries such as repair of a complex laceration to a digit, reduction of phalangeal dislocation or fracture, drainage of digital infections such as felon or paronychia, the removal of the nail plate, or for ring entrapment and removal. Once a clinician becomes familiar with the anatomy and technique of this procedure, then it may be utilized extensively in practice.
The digital nerve block procedure is one that requires an interprofessional team of professionals in the healthcare field which includes: clinicians, nursing staff, and a pharmacist. It is critical for these patients to receive a full history and physical before the procedure including a history of adverse drug reactions. In particular, this will include a history of local anesthetic use to identify alternatives, if required. A team-based approach to this procedure will limit deleterious events and should include the following before the start of the procedure: assessment of adverse events to local anesthetics and availability of alternative agents, calculation of maximum weight-based dosage of local anesthetic, consult with the pharmacist about the availability of a lipid emulsifying agent in the event of LAST, monitoring the patient for signs and symptoms of LAST such as AMS, metallic taste, seizures, respiratory distress, tachycardia, dysrhythmia, AV block, or cardiovascular collapse (Level III), and availability of ACLS trained staff in the event of cardiovascular symptom.
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