What is the most appropriate regional nerve block for a large laceration to the superior lateral lip?

Regional Nerve Block for Superior Lateral Lip Laceration

The infraorbital nerve block is the most appropriate regional anesthesia technique for a large laceration to the superior lateral lip, as it provides complete sensory blockade to this anatomic region. 1, 2

Anatomic Rationale

The superior lateral lip receives its sensory innervation from the infraorbital nerve, which is a terminal branch of the maxillary division of the trigeminal nerve (V2). 3 This makes the infraorbital nerve block the definitive choice for anesthetizing this region. 1, 2

Technique Selection: Intraoral vs. Percutaneous Approach

The intraoral approach is preferred over the percutaneous technique based on the following evidence:

• Superior anesthetic efficacy: The intraoral approach achieved upper lip anesthesia in 100% of subjects (12/12) compared to 75% (9/12) with the percutaneous approach. 1

• Longer duration of anesthesia: The intraoral technique provided significantly longer anesthesia (1.6 ± 0.8 hours vs. 0.9 ± 0.4 hours, p = 0.04). 1

• Patient preference: Nine of 12 subjects considered the intraoral technique less painful, though this did not reach statistical significance. 1

• Consistent anatomic landmark: The superior lateral labial frenum serves as a reliable intraoral reference point that remains constant regardless of dentition status. 4

Procedural Steps for Intraoral Infraorbital Block

Preparation:

• Apply topical anesthetic (viscous lidocaine) to the oral mucosa for 1 minute prior to injection. 1
• Prepare the injection site with antiseptic solution. 5
• Use a 27-gauge needle for patient comfort. 1

Injection Technique:

• Locate the infraorbital foramen by palpating at the intersection of a vertical line through the pupil (neutral gaze) and a horizontal line through the ala of the nose. 2
• Insert the needle intraorally at the superior lateral labial frenum, directing it medially and cephalad toward the infraorbital foramen. 2, 4
• Aspirate before injection to ensure the needle is not intravascular—this is critical to avoid systemic toxicity. 5, 6
• Inject 2 mL at the foramen, then redirect medially toward the ala (1 mL), and finally caudally into the lip (2 mL). 2
• Inject slowly over 20 seconds to minimize discomfort and tissue trauma. 5, 1

Local Anesthetic Selection

Use 2.5 mL of 2% buffered lidocaine for laceration repair in the emergency/office setting. 1 For surgical procedures requiring longer anesthesia:

• Combination approach: Mix equal volumes of 2% lidocaine with 1:200,000 epinephrine and 0.5% bupivacaine (total 10 mL for bilateral block). 2
• This provides immediate onset from lidocaine and prolonged analgesia (6-24 hours, mean 16.5 hours) from bupivacaine. 2

Critical Safety Considerations

Aspiration is mandatory before every injection to prevent intravascular administration, which can cause severe systemic toxicity including seizures, cardiovascular collapse, and respiratory arrest. 5, 6

Head and neck blocks carry specific risks: Small doses of local anesthetics injected in the head and neck area can produce adverse reactions similar to systemic toxicity seen with unintentional intravascular injections, including confusion, convulsions, respiratory depression, and cardiovascular instability. 6 This may occur due to intra-arterial injection with retrograde cerebral flow. 6

Avoid in patients with:

• Severe hepatic disease (impaired metabolism of amide local anesthetics). 6
• Active oral or facial infection. 1
• Known lidocaine allergy. 1

Expected Outcomes

• Onset time: Similar between intraoral and percutaneous approaches, typically within minutes. 1
• Success rate: 100% anesthetic efficacy with proper intraoral technique. 1
• Duration: 1.6 hours with lidocaine alone; up to 24 hours with bupivacaine combination. 1, 2
• Complications: Minimal when performed correctly; no major complications reported in clinical studies. 2, 7

Post-Procedure Patient Counseling

Warn patients about inadvertent trauma: Patients should be cautioned not to chew solid foods or test the anesthetized area by biting or probing until sensation returns (up to 7 hours with bupivacaine), as they may inadvertently injure the tongue, lips, or buccal mucosa. 6