Overview
Definition:
A digital nerve block is a regional anesthetic technique used to provide analgesia to a digit (finger or toe) by injecting local anesthetic solution around the digital nerves
This method is crucial for managing painful procedures such as laceration repair, foreign body removal, or fracture reduction in the digits, particularly in pediatric patients where cooperation can be challenging.
Epidemiology:
Finger lacerations are common pediatric emergencies
While precise incidence of requiring digital blocks is difficult to ascertain, it is a frequently encountered procedure in pediatric emergency departments and urgent care centers
Age is a significant factor, with younger children often requiring more robust pain control strategies.
Clinical Significance:
Effective pain management in pediatric patients undergoing digital procedures is paramount for patient comfort, cooperation, and successful treatment
A well-performed digital nerve block offers superior and longer-lasting analgesia compared to local infiltration, minimizing the need for systemic analgesics and reducing patient distress
This technique is a fundamental skill for pediatric residents preparing for DNB and NEET SS examinations.
Age Considerations
Neonates Infants:
Younger infants may require parental presence and distraction techniques
Local anesthetic toxicity is a concern due to lower metabolic capacity
hence, careful dosing is essential.
Toddlers Preschoolers:
This age group may exhibit anxiety and fear
Effective distraction, child life specialists, and swift procedure execution are vital
Lidocaine with or without epinephrine (depending on location and duration) is commonly used.
School Aged Adolescents:
Older children can often understand explanations and may cooperate more readily
They may prefer less dramatic injections
The choice of anesthetic and potential for epinephrine can be discussed.
Anxiety Management:
Regardless of age, a calm environment, clear explanations (age-appropriate), distraction methods (e.g., toys, videos), and a quick, confident approach are key to minimizing fear and maximizing success.
Clinical Presentation
Chief Complaint:
Parental report of finger injury, pain, bleeding, or inability to move the finger
Child's vocalization of pain or distress related to the finger.
Associated Symptoms:
Visible laceration, foreign body, deformity, swelling, or hematoma
Possible signs of underlying fracture or tendon/nerve injury.
History Of Present Illness:
Mechanism of injury (e.g., cut by sharp object, crush injury)
Time since injury
Previous tetanus immunization status
Any allergies, particularly to local anesthetics.
Diagnostic Approach
History Taking:
Detailed history of injury mechanism, time of onset, severity of pain, and any associated symptoms
Assess tetanus status
Inquire about prior procedures or injuries to the affected digit.
Physical Examination:
Inspect the digit for laceration depth and length, contamination, foreign bodies, and associated swelling or deformity
Assess capillary refill, sensation (light touch, pinprick), and motor function (finger extension/flexion) distal to the laceration
Palpate for crepitus, suggesting fracture.
Investigations:
X-rays of the affected digit are indicated if there is suspicion of fracture, dislocation, or retained radio-opaque foreign body
Ultrasound may be useful for non-radiopaque foreign bodies or assessing soft tissue injury
No routine lab investigations are typically needed unless systemic illness is suspected.
Differential Diagnosis:
Simple contusion, subungual hematoma, tendon injury (extensor or flexor), digital nerve laceration, digital artery laceration, fracture, or dislocation
The need for a nerve block is primarily for pain control during repair, regardless of the specific underlying injury, provided it is a superficial laceration.
Management
Initial Management:
Gentle cleansing of the wound with sterile saline
Application of a sterile dressing to control bleeding while preparing for the block
Ensure adequate lighting and necessary equipment are readily available.
Anesthetic Choice:
Lidocaine 1% or 2% without epinephrine is commonly used for its rapid onset and moderate duration of action (approx
1-2 hours)
Bupivacaine 0.25% or 0.5% can be used for longer duration (4-8 hours) if needed, often in combination with lidocaine
Maximum safe pediatric doses must be calculated based on weight.
Procedure Steps:
Identify the digital nerves located dorsolaterally to the digital arteries on each side of the finger, typically at the base of the proximal phalanx
Using a 25-30 gauge needle, enter the subcutaneous tissue and slowly aspirate to ensure no intravascular injection
Inject 1-2 mL of local anesthetic solution circumferentially around the neurovascular bundle
Wait 5-10 minutes for onset of anesthesia before proceeding with the laceration repair.
Wound Management:
After successful anesthesia, the laceration can be thoroughly cleaned, explored, and repaired using appropriate suturing techniques
Assess for any underlying tendon or nerve injury requiring further intervention
Ensure the wound is closed without tension.
Pain Control Post Procedure:
Oral analgesics (acetaminophen or ibuprofen) should be offered for post-procedure pain
Monitor for signs of local anesthetic toxicity (rare with correct dosing)
Tetanus prophylaxis should be administered if indicated.
Complications
Early Complications:
Hematoma formation at the injection site
Transient paresthesia or nerve injury (usually temporary)
Local anesthetic toxicity (seizures, CNS depression, cardiovascular compromise) if excessive dose is used or rapid IV injection occurs
Infection at the injection site (rare).
Late Complications:
Chronic pain or dysesthesia (very rare)
Scarring at the injection site
Persistent nerve injury (extremely rare).
Prevention Strategies:
Strict aseptic technique during injection
Aspiration before injection to prevent intravascular administration
Careful calculation of anesthetic dose based on patient weight
Slow injection of the anesthetic solution
Adequate waiting period for anesthetic onset to avoid painful manipulation.
Prognosis
Factors Affecting Prognosis:
The prognosis for a digital nerve block itself is excellent with no long-term sequelae when performed correctly
Prognosis for the finger laceration depends on the depth, involvement of vital structures (tendons, nerves, vessels), and timely, appropriate repair
Prompt and effective pain relief during repair contributes to a less traumatic experience.
Outcomes:
Successful and complete analgesia for the duration of the procedure
Reduced patient distress and improved cooperation
Facilitates thorough wound assessment and repair.
Follow Up:
Follow-up is primarily for wound healing and removal of sutures
Advise parents on signs of infection to watch for
If nerve or tendon repair was performed, specific follow-up protocols for those injuries will apply.
Key Points
Exam Focus:
Understanding the anatomy of the digital nerves and their location
Knowing the maximum safe doses of common local anesthetics (lidocaine, bupivacaine) in pediatric patients
Recognizing the signs and management of local anesthetic toxicity
Differentiating between digital nerve block and digital artery injection.
Clinical Pearls:
Use a small gauge needle (25-30g) for pediatric patients to minimize pain and anxiety
Always aspirate before injecting
Inject slowly
Have a second person assist with distraction if possible
A digital block provides anesthesia to the entire finger distal to the block.
Common Mistakes:
Injecting into the digital artery
Using an excessive dose of local anesthetic
Failing to wait for anesthetic onset before starting the procedure
Inadequate aseptic technique
Incorrect landmark identification.