Digital Nerve Block

Article Author:
Andrew Napier
Article Editor:
Alan Taylor
Updated:
3/17/2019 10:14:58 AM
PubMed Link:
Digital Nerve Block

Introduction

The digital nerve block is a simple procedure that can be performed to provide immediate anesthesia for a multitude of injuries 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[1]. The digital nerve block is generally superior to local infiltration as a reduced amount of anesthetic is required for this procedure compared to local infiltration, which is of importance as only a limited volume of anesthetic is tolerated in the digits due to restricted space.[2]

Anatomy

Healthcare providers must recognize the specific nerves that originate from the deep branches of the median, radial and ulnar nerves which innervate the hands. The dorsal set of nerves run alongside the digit at the 10- and 2-o'clock positions, while the volar (or palmer) set of nerves travel at the 4- and 8-o'clock positions such as seen in the attached image. The volar set of nerves provide sensory input for the entire digit at the volar surface including the distal ends and nailbeds for digits 2, 3, and 4. The nerves originate from the deep volar branches of the median and ulnar nerves at the area of the wrist. These nerves are known as the palmar digital nerves. The dorsal nerves provide sensory input for the entire dorsal aspect of the digit, including the nailbed, of digits 1 and 5. These nerves also provide sensory input of the proximal areas of digits 2, 3, and 4. These nerves originate from the radial and ulnar nerves. Anatomical knowledge of digital nerve innervations is of clinical relevance because if anesthesia is needed to the distal portion of digits 2 top 4 then only the volar nerves need to be blocked, but digits 1 and 5 would require a block of both volar and dorsal nerves.[3]

Indications

Indications for digital nerve block include:

  • Immediate relief of pain to the digit
  • Repair of complex lacerations to the digit
  • Reduction of phalangeal dislocation
  • Reduction of phalangeal fracture
  • Drainage of digital infections such as felon or paronychia
  • Removal of the nail plate
  • Ring entrapment and removal

Contraindications

Contraindications to the digital nerve block include:

  • Patient refusal
  • Overlying infection of the site of injection
  • Distortion of landmarks
  • Allergy to local anesthetics

Equipment

Required equipment for this procedure include:

  • Anesthetic agent: Selection depends on the intended duration of the block and patient's reported allergies. 
  • Lidocaine for a 30- to 90-minute duration of anesthesia, bupivacaine for 6- to 8-hour duration of anesthesia, tetracaine for up to 3 hours of local anesthesia
  • Consider local diphenhydramine if the patient is allergic to both amides and esters local anesthetics.
  • 27- to 30-gauge needle
  • Five to 10-mL syringe
  • Skin cleansing agents such as alcohol pads or chlorhexidine 2% 
  • Access to lipid emulsion solution in case of local anesthetic systemic toxicity

Preparation

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 as well.

Technique

A dorsal approach is preferred due to the thinness of the skin in this location and decreased sensitivity.[4]

The procedure is performed in the following steps:

  1. Using aseptic technique, identify landmarks and clean area using an alcohol wipe
  2. Insert a 27-gauge needle into the dorsal aspect of the web space on one side of the digit to be anesthetized slightly distal to the knuckle. 
  3. Advance the needle slightly
  4. Inject 0.5 to 1 mL of local anesthetic solution forming a wheal to block the dorsal digital nerve
  5. Advance the needle further toward the palmar surface.
  6. Inject another 0.5 to 1 mL of local anesthetic forming a wheel to block the volar digital nerve.
  7. Firm massage for approximately 30 seconds will enhance diffusion of the anesthetic.
  8. Repeat the procedure on the other side of the digit to be blocked. 

An alternative to this technique is to leave the needle in place after step 6 and redirect the needle tip across the surface of the digit to inject the dorsal surface and reduce pain from the second injection required for each digit that is to be blocked.

Complications

Complications include:

  • Infection
  • Bleeding
  • Vascular injection of anesthetic
  • Nerve injury including neurapraxia or neurolysis
  • Local anesthetic systemic toxicity (LAST)
  • Allergic reaction to the local anesthetic

Clinical Significance

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.[5]

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.[6]

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.

Enhancing Healthcare Team Outcomes

The digital nerve block procedure is one that requires an interprofessional team of professionals in the healthcare field which includes a clinician, 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[7] (Level III)
  • Availability of ACLS trained staff in the event of cardiovascular symptoms


  • (Move Mouse on Image to Enlarge)
    • Image 6794 Not availableImage 6794 Not available
      Gray's Anatomy Plates, Fig. 817

References

[1] Knoop K,Trott A,Syverud S, Comparison of digital versus metacarpal blocks for repair of finger injuries. Annals of emergency medicine. 1994 Jun     [PubMed PMID: 8198304]
[2] De Buck F,Devroe S,Missant C,Van de Velde M, Regional anesthesia outside the operating room: indications and techniques. Current opinion in anaesthesiology. 2012 Aug     [PubMed PMID: 22673788]
[3] Kim J,Lee YH,Kim MB,Rhee SH,Baek GH, Anatomy of the direct small branches of the proper digital nerve of the fingers: a cadaveric study. Journal of plastic, reconstructive     [PubMed PMID: 24908546]
[4] Yin ZG,Zhang JB,Kan SL,Wang P, A comparison of traditional digital blocks and single subcutaneous palmar injection blocks at the base of the finger and a meta-analysis of the digital block trials. Journal of hand surgery (Edinburgh, Scotland). 2006 Oct     [PubMed PMID: 16930788]
[5] Al-Chalabi M,Gupta S, Neuroanatomy, Spinal Cord, Tract, Spinothalamic null. 2018 Jan     [PubMed PMID: 29939601]
[6] Kehlet H,Dahl JB, The value of     [PubMed PMID: 8105724]
[7] Fencl JL, Local anesthetic systemic toxicity: perioperative implications. AORN journal. 2015 Jun     [PubMed PMID: 26025745]