Infraorbital nerve block: anatomy, indication and risks

The infraorbital nerve block is one of the regional anesthesia techniques that appear in HOF courses, especially for procedures on the upper lip and the nasolabial fold. It reduces pain in sensitive areas, but it carries its own risks and requires specific training. This page covers anatomy, indication and risks at a review level, without describing the technique step by step. Preparation, dose, route and authorization follow the anesthetic's package insert, the training and the rules of each professional's council in Brazil.

What anatomy is involved?

The infraorbital nerve is the continuation of the maxillary nerve (V2, a branch of the trigeminal). It runs along the floor of the orbit and exits through the infraorbital foramen, below the orbital rim, where it divides into palpebral, nasal and superior labial branches. These branches supply sensation to the lower eyelid, the side of the nose, the anterior cheek and the upper lip. The foramen is usually aligned with the pupil when the gaze is straight ahead, but variations exist.

The infraorbital artery and vein accompany the nerve, and the area neighbors vessels such as the angular and facial arteries. For the overall reasoning, see supraorbital and supratrochlear block and periorbital anatomy for injectables.

When is the block considered?

The block may be considered in painful procedures on the upper lip, the nasolabial fold or the malar area, in patients with low pain tolerance, or when topical anesthetic is not enough. There are alternatives that many professionals prefer: topical anesthetics, hyaluronic acid with lidocaine, ice and distraction techniques. The overview of options is in local anesthesia in HOF: overview.

What are the risks of the infraorbital block?

• Bruising, because of the course of vessels near the foramen.
• Intravascular injection of the anesthetic, with local and systemic risk. See systemic toxicity from local anesthetic.
• Nerve injury, with paresthesia or neuropathic pain, usually transient. See paresthesia after an HOF procedure and nerve injury with injectables.
• Swelling and distortion of the field, which make it harder to assess lip and fold symmetry.
• Vasoconstrictor effect, when present, with pallor that can be mistaken for a sign of ischemia. See vascular occlusion vs anesthesia pallor.
• Allergic reaction to the anesthetic. See local anesthetic allergy in HOF.
• Patient discomfort, as the lip and cheek feel "numb," and the patient may bite the mucosa without noticing.

How to proceed safely, at the level of principles

Without describing technique, some principles apply to any regional anesthesia in HOF:

1. Medical history: allergies, use of anticoagulants, heart disease, pregnancy, medications. See medical history in HOF and heart disease and anesthetics with vasoconstrictor.
2. Dose of the anesthetic according to the package insert and the patient's weight, with a record.
3. Proper antisepsis. See chlorhexidine in facial antisepsis.
4. Equipment and emergency: kit and team prepared. See HOF office emergency kit.
5. Specific informed consent for regional anesthesia.
6. Record of the anesthetic, dose and area in the patient record.

Does the block change the assessment of the result?

Yes, and it matters. The anesthetic causes local swelling and loss of sensation, and the assessment of lip and fold symmetry during the procedure may be distorted. In procedures where symmetry is critical, some professionals prefer to avoid the block or wait for the effect to wear off before deciding on add-ons. Record when the block was done and always reassess at follow-up, because the impression on the day may not reflect the final result. The logic is in clinical follow-up consultation.

Authorization, regulation and responsibility

Regional anesthesia is not a technique that every HOF professional is automatically authorized to perform. Permission depends on training, on the professional council and on the rules in force, and those rules change. So the first step in any decision about a block is checking the regulation that applies to your council, not reading a tutorial. If in doubt, consult the council and record the guidance received. See HOF regulation at the CFO, facial harmonization and the CFM and aesthetics in nursing and Cofen as a starting point for the regulatory debate in Brazil, without treating any of them as a definitive answer for your case.

Part of the responsibility is also knowing when not to block. Patients with a known allergy to anesthetics, with heart disease in which the vasoconstrictor is a problem, taking anticoagulants or with a local infection are at higher risk. Choosing a less invasive alternative, when one exists, is usually the most prudent. The reasoning on systemic effects is in systemic toxicity from local anesthetic.

What to record

In the patient record, note the anesthetic, the concentration, the total dose, the side, the route, the time, any complications and the guidance given. If there was bruising, photograph and follow up. If the patient reported a change in sensation, record the start date and the progression. This record protects the patient and the professional. See patient records and documentation in HOF.

Patient guidance

The patient should know what they will feel, for how long and what precautions to take. Numbness of the lip, nose and lower eyelid is expected, and accidentally biting the mucosa is a real risk. Hot foods should be avoided while the numbness lasts. Warning signs should be explained and written down.

Where does Harmy come in?