26.2 Dental, Orthodontic, Oral-Maxillofacial & Ophthalmic Anesthesia

Why This Topic Matters on the NCE

Two named sub-topics converge here: orthodontic and dental procedures (IV.A.3.a.vi) and ophthalmologic procedures (IV.A.3.a.ii). They share a physical constraint — the surgeon owns the head — and they share the two most heavily tested reflex and pressure physiologies in the head and neck.

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1. Dental and Oral-Maxillofacial Anesthesia

Who gets general anesthesia for dental work

• Young children with extensive caries requiring full-mouth rehabilitation
• Patients with intellectual or developmental disability, dementia, or severe behavioral needs who cannot cooperate
• Severe dental phobia
• Complex oral surgery: impacted third molars, implants, orthognathic procedures

Setup

• Nasotracheal intubation is standard when the whole mouth must be accessible; an oral RAE tube may suffice for unilateral work.
• Throat pack to prevent aspiration of tooth fragments, irrigation, and blood, documented on the count with removal explicitly verified.
• Blood and debris in the pharynx cause substantial postoperative nausea and vomiting; suction thoroughly and give multimodal antiemetics.
• Long cases with the head turned require eye protection and attention to the neck.

Dental injury: the most common anesthesia claim

Dental damage during laryngoscopy is consistently one of the most frequent anesthesia-related malpractice claims.

• The maxillary incisors, especially the left upper central and lateral incisors, are most commonly damaged, because they are the fulcrum point for a laryngoscope levered rather than lifted.
• Document the preoperative dental examination — existing caries, crowns, bridges, veneers, loose or chipped teeth, and periodontal disease — and discuss risk with high-risk patients.
• Risk factors: prior difficult intubation, limited mouth opening, protruding incisors, periodontal disease, restorations, and children with loose deciduous teeth.
• Protective devices (mouth guards) reduce but do not eliminate risk and can worsen the view.
• If a tooth is dislodged and cannot be found, obtain chest and abdominal radiographs — an aspirated tooth must be located and retrieved bronchoscopically.

Ludwig angina

Bilateral cellulitis of the submandibular, sublingual, and submental spaces, usually from a dental source. It is a true airway emergency.

• Woody induration of the floor of the mouth pushes the tongue upward and backward; trismus is common.
• Mask ventilation and direct laryngoscopy may both be impossible, and the swelling is below the tongue where a supraglottic device cannot help.
• Do not induce general anesthesia or give a neuromuscular blocker. The correct approach is an awake technique — awake flexible bronchoscopic intubation if feasible, or awake tracheostomy under local anesthesia — with the surgeon prepared.

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2. Ophthalmic Anesthesia

Intraocular pressure

Normal intraocular pressure is 10 to 21 mmHg. It is determined by aqueous humor production and drainage, choroidal blood volume, extraocular muscle tone, and external pressure on the globe.

Coughing and bucking raise intraocular pressure far more than succinylcholine does. This single fact resolves the classic open-globe dilemma.

The open globe with a full stomach

The historic teaching was that succinylcholine must never be used in an open globe because the transient pressure rise could extrude intraocular contents. Modern practice recognizes that (1) the risk was likely overstated and no case of extrusion attributable to succinylcholine alone has been convincingly documented, and (2) an inadequately paralyzed patient who coughs on the tube generates a far greater pressure rise.

The current mainstream approach is a rapid sequence induction with high-dose rocuronium 1.2 mg/kg, which produces intubating conditions in about 60 seconds without any pressure rise, with sugammadex immediately available for rescue. Succinylcholine remains acceptable in specific circumstances and is not an absolute contraindication, but rocuronium is the preferred exam answer.

Above all, ensure a deep plane of anesthesia and complete paralysis before laryngoscopy, and a smooth emergence without coughing.

The oculocardiac reflex

• Afferent limb: long and short ciliary nerves to the ciliary ganglion, then the ophthalmic division of the trigeminal nerve (V1) to the gasserian ganglion and the trigeminal nucleus.
• Efferent limb: the vagus nerve (X).
• Mnemonic: "five and dime" — cranial nerve V in, cranial nerve X out.
• Trigger: traction on the extraocular muscles, especially the medial rectus, pressure on the globe, retrobulbar block, and orbital hematoma.
• Manifestation: sinus bradycardia, junctional rhythm, ventricular ectopy, and asystole.
• More common in children, and potentiated by light anesthesia, hypercarbia, and hypoxemia.
• Management, in order:
  1. Tell the surgeon to stop the traction — this alone resolves most episodes
  2. Confirm adequate ventilation and oxygenation, and deepen the anesthetic
  3. Atropine 0.02 mg/kg IV (or glycopyrrolate) if the reflex is persistent or recurrent
  4. Surgical infiltration of the muscle with local anesthetic
• The reflex fatigues with repeated stimulation. A retrobulbar block may prevent it, but the block itself can trigger it.

Retrobulbar and peribulbar blocks

Complications the CRNA must recognize:

• Retrobulbar hemorrhage — tense proptotic globe; a sight-threatening emergency requiring urgent decompression
• Globe perforation — higher risk in the myopic, long axial-length eye
• Optic nerve injury
• Brainstem anesthesia — injection along the optic nerve sheath into the subarachnoid space produces contralateral amaurosis, cranial nerve palsies, altered consciousness, seizures, and apnea requiring immediate airway support. It typically appears within 5 to 10 minutes of injection.
• Oculocardiac reflex from the block itself

Intraocular gas and nitrous oxide

When the surgeon injects an intraocular gas bubble — sulfur hexafluoride (SF6) or perfluoropropane (C3F8) — to tamponade a retinal detachment:

• Discontinue nitrous oxide at least 15 to 20 minutes before the gas is injected. Nitrous oxide diffuses into the bubble far faster than the gas leaves, expanding it and causing a dangerous rise in intraocular pressure with retinal artery occlusion.
• Afterward, nitrous oxide must be avoided for approximately 10 days after SF6 and up to 30 days after C3F8 for any subsequent anesthetic. Patients should carry a wristband.

Strabismus surgery

Combines the two highest-yield ophthalmic topics: it is the classic trigger of the oculocardiac reflex through medial rectus traction, and it has among the highest rates of postoperative nausea and vomiting of any pediatric procedure, warranting multi-agent prophylaxis.

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Exam Traps

• Coughing raises intraocular pressure more than succinylcholine does. Prevent the cough.
• Oculocardiac reflex: V afferent, X efferent, stop the traction first.
• Stop nitrous oxide 15 to 20 minutes before intraocular gas, and avoid it for 10 to 30 days afterward.
• Ludwig angina gets an awake airway. Never induce and paralyze.
• A missing tooth needs a radiograph to exclude aspiration.