Infraorbital Nerve Block

Anatomy and Physiology

The infraorbital nerve is a branch of the maxillary nerve, the second division of the trigeminal nerve. The maxillary nerve exits the pterygopalatine fossa through the inferior orbital fissure and then traverses the orbital floor as the infraorbital nerve. The infraorbital nerve provides sensory innervation to the lower eyelid, lateral aspect of the nose, upper lip, upper incisor, canine, premolars, and the mesiobuccal root of the first molar on the same side of the face.

The infraorbital nerve block anesthetizes the anterior and middle maxillary alveolar nerves, inferior palpebral, lateral nasal, and superior labial nerves. This also includes the maxillary incisors, canines, and premolars, as well as their vestibular osseous support and the soft tissues that cover them. Additionally, it covers the mesiobuccal root of the maxillary first molar, part of the maxillary sinus, and the nose.[2] However, the posterior superior alveolar nerve, which provides sensory innervation to the maxillary molars, is not affected by this block, as it branches from the maxillary nerve proximal to the infraorbital foramen.

A useful landmark-based approach for both adult and pediatric patients involves using the nasospinale and jugale cranial landmarks.[3][4] The nasospinale is located at the intersection of the midsagittal plane with the lowest point of the nasal opening. The jugale is found at the intersection of the temporal and frontal processes of the zygomatic bone. Once these points are identified, the infraorbital foramen can be located at the midpoint between them.

Variations in nerve supply can impact the effectiveness of nerve blocks. Notably, it has been reported that up to 54% of the population has a middle superior alveolar nerve that exits the infraorbital groove. In the same study, 18% of cases showed no evidence of a middle superior alveolar nerve, while the remaining 28% exhibited a variant.[5] Due to the significance of this anatomical variability, Bali et al. proposed a molar approach for the infraorbital block.[6]

In summary, the infraorbital nerve block anesthetizes the nerves mentioned below.

• Infraorbital nerve and its terminal branches, including:
  • Inferior palpebral branch
  • Lateral nasal branch
  • Superior labial branch
• Anterior superior alveolar nerve
• Middle superior alveolar nerve

Notably, the infraorbital artery and vein are located near the nerve, so caution should be exercised to avoid intravascular injections of local anesthetics.

Indications

Nerve blocks are effective for achieving partial or complete analgesia in a targeted area supplied by a specific nerve or nerve bundle, with applications in both surgical and office settings. Infraorbital nerve blocks are indicated for surgeries in the operating room, which involve the upper lip (eg, cleft lip repair), nasal septum, orbital floor, and lower eyelid. In an office setting, they are commonly used for procedures such as wound debridement, abscess incision and drainage, facial wound suturing, management of pain syndromes involving the infraorbital nerve, and various dental and cosmetic procedures.[7][8][9]

Regional anesthesia has been shown to offer significant postoperative analgesia benefits. For example, infraorbital nerve blocks have been demonstrated to reduce opioid consumption and shorten the time from surgery to oral intake in neonates and children undergoing cleft lip reconstruction.[10][11]

Contraindications

Contraindications for an infraorbital nerve block include infection at the intended injection site, patient refusal, allergy to anesthetic agents, distortion of anatomical landmarks, coagulopathy, chronic pain syndromes in the injection area, and wounds involving regions innervated by multiple nerves. Caution is also advised for patients with facial trauma, as distorted anatomy can complicate the procedure and increase the risk of complications.

Equipment

Several anesthetic agents can be used for nerve blocks, with amino amides and amino esters differing in their chemical structure, specifically the intermediate chain between the aromatic and hydrophilic segments. Amides are metabolized in the liver and undergo hydrolysis to produce para-aminobenzoic acid (PABA), making them more likely to cause allergic reactions than amino esters. In contrast, amino esters are metabolized in the plasma by pseudocholinesterases. A simple way to remember which drugs belong to each group is that amino amides generally have 2 "I's" in their spelling. Common amides include lidocaine and bupivacaine, while common esters include tetracaine, benzocaine, procaine, and cocaine.

The 2 most common anesthetic agents for an infraorbital nerve block are lidocaine and bupivacaine. Lidocaine has a faster onset and shorter duration compared to bupivacaine. Lidocaine typically starts to take effect within 2 to 3 minutes after infiltration, whereas bupivacaine may take 10 to 20 minutes to become effective. Generally, only 1 to 3 mL of the agent is required, making toxicity rare. The total dose of lidocaine with epinephrine should not exceed 7 mg/kg (0.7 mL/kg of 1% lidocaine) and 5 mg/kg without epinephrine. Bupivacaine offers the advantage of longer analgesia, lasting over 12 hours, with studies reporting excellent pain control using 0.25% and 0.5% formulations.[12]

Necessary equipment for the procedure includes a 27-gauge needle, a blunt fill needle, gauze, a 5- to 10-mL syringe (preferably with a Luer-lock for better control and administration), a local anesthetic agent, and both sterile and nonsterile gloves.

Personnel

An infraorbital nerve block requires a skilled clinician, such as an anesthesiologist, dentist, or trained physician, proficient in regional anesthesia techniques. Although the procedure can be performed by a single clinician, support staff, such as a nurse or medical assistant, can be invaluable for patient monitoring, preparation, and assistance with equipment. In some cases, an additional staff member may be needed for patient stabilization, extra support during the procedure, or to obtain supplies. The team must ensure proper aseptic techniques, patient safety, and readiness to manage any potential complications.

Preparation

Preparation for an infraorbital nerve block involves several key steps to ensure patient safety and procedural success. The patient should be educated about the procedure, including its risks and benefits, and informed consent must be obtained. The patient’s medical history, including allergies and contraindications, should be reviewed. The clinician then identifies and marks the anatomical landmarks for the block, if necessary. The area is cleaned with an antiseptic solution to minimize the risk of infection. Equipment, including a syringe, appropriate gauge needle, and local anesthetic, should be prepared and checked. Additionally, emergency equipment should be readily available to manage any adverse reactions or complications.

Technique or Treatment

The infraorbital nerve block can be performed by either an extraoral or intraoral method.

Intraoral Methods

Conventional bicuspid approach: The patient is seated, ensuring that the maxillary occlusal plane forms a 45° angle with the floor. A cotton-tipped applicator is used to apply a topical anesthetic to the oral mucosa along the gum line above the maxillary canine. The infraorbital foramen is approximated by instructing the patient to look straight ahead and visualizing a line extending from the pupil down to the inferior border of the infraorbital ridge, bicuspid teeth, and mental foramen. The inferior orbital rim is then located using the index and middle fingers of the non-injecting hand.

Once the inferior orbital rim is located, the palpating finger should remain in place to maintain the landmark and prevent the needle from entering the orbit. The cheek is retracted with the thumb of the non-injecting hand, and the needle is then inserted into the mucosa above the upper second bicuspid, approximately 0.5 cm from the buccal surface. The needle should be directed superiorly, remaining parallel to the second bicuspid until it is palpated near the infraorbital foramen. 

Before injecting the anesthetic, aspirating is crucial to ensure the needle is not within a vessel. The anesthetic should be injected into the space, avoiding the foramen by maintaining firm pressure on the inferior orbital rim with the palpating finger.

Molar approach: For the molar approach, the needle is inserted at the buccal vestibule near the first molar, just medial to the zygomatic buttress. The needle should be angled at 65º to the maxillary occlusal plane, directing it superiorly, posteriorly, and medially toward the infraorbital foramen. This approach is reported to be less painful than the palatal approach.[6]

Alar base approach: The alar base approach is particularly useful for patients with missing or absent teeth. The index finger of the non-injecting hand is placed on the ipsilateral alar base while the thumb lifts the upper lip and applies tension. A 27-gauge needle is then inserted intraorally, just posterior to the alar base. The needle is carefully advanced toward the infraorbital foramen. Once the needle contacts the bone, aspiration is performed in multiple planes before injecting 1 to 2 mL of local anesthetic.[13]

Extraoral Methods

Anatomic approach: The infraorbital foramen can be located by having the patient look straight ahead while the clinician imagines a line descending from the pupil to the inferior border of the infraorbital ridge, passing through the bicuspid teeth and mental foramen. The clinician should identify the inferior border of the infraorbital rim. The skin over the infraorbital foramen is then cleansed with an antiseptic agent and sterile gauze. The needle is inserted through the skin, subcutaneous tissue, and muscle. Before injecting the anesthetic, the clinician should aspirate to ensure the needle is not within a vessel, then proceed with the injection. Due to the proximity of the facial nerve when using the extraoral approach, it is advisable to select an anesthetic agent without added vasoconstrictors. The overlying tissues should appear edematous after injection, and the area should be massaged for 10 to 15 seconds after removing the needle.

Ultrasound-guided approach: A linear ultrasound probe is positioned on the inferior orbital rim in the transverse plane and then swept toward the nasal base until a hypoechoic break is detected, indicating the infraorbital foramen. Doppler imaging can be used to identify and avoid vascular structures. The needle is introduced using an out-of-plane approach, and it is crucial to aspirate before injecting the local anesthetic to prevent intravascular injection.[9]

Complications

Complications from an infraorbital nerve block may include bleeding, hematoma formation, infection, injury to the artery or vein, unintentional injection of anesthetic into the artery or vein, nerve damage, or edema.[14][15] In the event of intravascular injection with a local anesthetic, 20% intravenous fat emulsion should be administered if available, starting with a 1.5-mL/kg bolus over 2 to 3 min, followed by an infusion at 0.25 mL/kg/min.[16]

Special considerations include avoiding injection into the infraorbital foramen, as this could lead to long-term neuropathy due to nerve compression, damage to the orbital floor, or injury to the orbit. If there is any suspicion of orbital damage, immediate consultation with ophthalmology is required.

Allergic reactions to the anesthetic medication can occur during the procedure, and management should be supportive based on the affected organ systems. Other possible reactions to anesthetic medications may include cardiovascular and neurological symptoms. In addition, methemoglobinemia is also a possible complication, depending on the anesthetic agent used.

Clinical Significance

The infraorbital nerve block provides effective analgesia by delivering anesthetic medication to the distribution of the infraorbital nerve. This makes it suitable for injury repair, wound management, dental and cosmetic procedures, and pain relief. This is particularly advantageous for procedures involving the midface, as it minimizes tissue distortion and requires lower anesthetic volumes compared to local infiltration.

Enhancing Healthcare Team Outcomes

The successful administration of an infraorbital nerve block depends on the collaborative efforts of an interprofessional healthcare team. Specialists such as anesthesiologists, dentists, trauma surgeons, facial surgeons, and emergency department physicians may perform the nerve block. A dedicated nurse should be assigned to monitor the patient throughout the procedure. Additionally, resuscitation equipment must be readily available in the operating room before starting the procedure to manage any potential complications, such as intravascular injection.

Although the procedure is relatively straightforward and safe, inadvertent injury to the nerve is a recognized risk. Additionally, due to the proximity of the infraorbital artery and vein, a risk of intravascular injection exists. This issue can be managed by 20% intravenous fat emulsion, which should be readily available, and its location should be confirmed as part of the pre-procedure checklist. After the procedure, the patient must be monitored for 30 to 45 minutes to ensure no complications arise. Collaboration among interprofessional healthcare providers enhances the precision and safety of the procedure, contributing to optimal patient outcomes and a higher standard of care.

Nursing, Allied Health, and Interprofessional Team Interventions

The below-mentioned key interventions should be followed to ensure a successful and safe infraorbital nerve block procedure.

• Informed consent should be obtained from the patient.
• The patient should be educated about the procedure, including its potential risks and benefits.
• The skin site must be thoroughly cleaned before injection.
• The instrument tray should be prepared with all necessary equipment.
• Monitoring and resuscitation equipment must be confirmed as available and functional in the procedure room.

Nursing, Allied Health, and Interprofessional Team Monitoring

Effective monitoring is essential for patient safety during and after an infraorbital nerve block. Therefore, the healthcare team should follow the steps below.

• Continuously monitor the patient’s vital signs throughout and after the procedure.
• Observe for any signs of bleeding, anxiety, or pain at the injection site.
• Watch for signs of allergic reactions or other adverse effects related to the anesthetic agent.