What is the most appropriate regional nerve block for a patient presenting with a lip laceration?

Regional Nerve Block for Lip Laceration

For a lip laceration, the infraorbital nerve block is the most appropriate regional anesthetic technique, as the infraorbital nerve provides sensory innervation to the superior lateral lip. 1

Anatomic Rationale

• The infraorbital nerve, a terminal branch of the maxillary division of the trigeminal nerve, supplies sensory innervation to the upper lip, making infraorbital nerve blockade the definitive choice for upper lip anesthesia 1, 2
• For lower lip lacerations, the mental nerve block is the appropriate alternative, as the mental nerve provides sensory innervation to the lower lip 3, 4
• Without visualization of the specific laceration location in the provided image, the infraorbital block (option C) represents the most commonly indicated nerve block for lip lacerations presenting to emergency departments 5

Technical Approach: Intraoral vs Percutaneous

The intraoral approach is preferred over the percutaneous technique for several evidence-based reasons:

• The intraoral technique produces successful upper lip anesthesia in 100% of patients compared to 75% success with the percutaneous approach 5
• Duration of anesthesia is significantly longer with the intraoral approach (1.6 ± 0.8 hours) versus the percutaneous technique (0.9 ± 0.4 hours, p = 0.04) 5
• Patients subjectively prefer the intraoral approach, with lower pain scores during administration, though this difference did not reach statistical significance 5
• Application of topical anesthetic (viscous lidocaine for 1 minute) to the oral mucosa before injection further reduces discomfort 5

Procedural Technique

For intraoral infraorbital block:

• Apply topical anesthetic to the injection site and prepare with antiseptic solution 1
• The injection point is located at the intersection of a vertical line through the pupil (neutral gaze) and a horizontal line through the ala of the nose 6
• Use a 27-gauge needle with 2-2.5 mL of 2% lidocaine (buffered, at room temperature) 5
• Aspirate before injection to ensure the needle is not intravascular—this is mandatory to prevent systemic toxicity including seizures, cardiovascular collapse, and respiratory arrest 1
• Inject slowly over 20 seconds to minimize discomfort and tissue trauma 1, 5

Alternative Nerve Blocks by Location

If the laceration involves the lower lip specifically:

• Mental nerve block is the appropriate choice (option D) 3, 4
• The mental nerve block is performed intraorally after everting the lip and identifying the lower canine 3
• Inject 2 mL of lidocaine 2% with epinephrine 1:100,000 near the mental foramen 3
• This technique is particularly advantageous in elderly or high-risk patients as a safe alternative to general anesthesia 3

Why Other Options Are Incorrect

• Buccal nerve block (option A): The buccal nerve supplies the buccal mucosa and cheek, not the lip itself 2
• Inferior alveolar nerve block (option B): This block anesthetizes the lower teeth and mandibular structures but does not reliably anesthetize the lower lip soft tissue for laceration repair 2
• Mental nerve block (option D): Only appropriate for lower lip lacerations, not upper lip 3, 4

Critical Safety Considerations

• Regional nerve blocks for facial procedures should be performed with ultrasound guidance when available to reduce the risk of local anesthetic systemic toxicity 7
• Calculate and use a safe dose of local anesthetic—for lidocaine without epinephrine, the maximum is 4.5 mg/kg; with epinephrine, 7.0 mg/kg (total maximum 500 mg) 8
• Amide-type local anesthetics (lidocaine, bupivacaine) are preferred over ester-type agents for nerve blocks 7
• The addition of epinephrine prolongs the duration of anesthesia and enhances vasoconstriction 2

Common Pitfalls to Avoid

• Failure to aspirate before injection risks intravascular administration with potentially catastrophic consequences 1
• Injecting too rapidly increases patient discomfort and tissue trauma 1, 5
• Omitting topical anesthesia before intraoral injection increases procedural pain 5
• Using room temperature rather than warmed anesthetic solution increases discomfort 7
• Inadequate time allowed for block onset may lead to perceived block failure—allow sufficient onset time before proceeding 7