Residency · Residency · Oral Maxillofacial Surgery
General Anesthesia for the OMFS Surgeon
Introduction
General anesthesia is a cornerstone competency for oral and maxillofacial surgery (OMFS) residents. OMFS is unique among dental specialties in that practitioners administer deep sedation and general anesthesia in both office-based and hospital settings. Mastery of pharmacology, monitoring, and airway management is essential for safe patient care.
Pharmacology of General Anesthetic Agents
Intravenous Induction Agents
| Agent | Onset | Key Advantage | Key Risk | Notes |
|---|---|---|---|---|
| Propofol | 30-45 sec | Rapid onset/offset, antiemetic | Respiratory depression, hypotension | No analgesic effect |
| Etomidate | 30-60 sec | Hemodynamic stability | Adrenal suppression (repeated dosing) | Ideal for cardiovascularly compromised |
| Ketamine | 1-2 min | Preserves airway reflexes, analgesic | Emergence delirium, increased secretions | Dissociative anesthetic |
| Midazolam | 1-2 min | Anxiolysis, amnesia | Respiratory depression (synergistic with opioids) | Co-induction agent |
Propofol has a rapid onset (30-45 seconds) and short duration, causes dose-dependent respiratory depression and hypotension, and has antiemetic properties. Etomidate is a hemodynamically stable induction agent with minimal cardiovascular depression, though it carries risk of adrenal suppression with repeated dosing. Ketamine is a dissociative anesthetic with analgesic properties that preserves airway reflexes and spontaneous ventilation but increases secretions and may cause emergence delirium. Midazolam is a benzodiazepine used for anxiolysis and co-induction that provides amnesia with minimal analgesic effect.
Inhalational Agents
Sevoflurane is the most commonly used volatile agent, offering smooth induction with minimal airway irritation and suitability for mask induction. Nitrous oxide is an adjunctive analgesic and anxiolytic with rapid onset and offset that reduces the MAC of other agents by 20 to 30%. Desflurane provides rapid emergence but has a pungent odor that limits its use for inhalation induction and may cause airway irritation.
Neuromuscular Blocking Agents
| Agent | Type | Onset | Duration | Reversal | Key Concern |
|---|---|---|---|---|---|
| Succinylcholine | Depolarizing | 60 sec | 5-10 min | None (plasma cholinesterase) | Malignant hyperthermia, hyperkalemia |
| Rocuronium | Non-depolarizing | 60-90 sec | 30-45 min | Sugammadex | Most commonly used in OMFS |
| Cisatracurium | Non-depolarizing | 2-3 min | 30-40 min | Neostigmine | Hofmann elimination (organ-independent) |
Succinylcholine is a depolarizing agent with rapid onset (60 seconds) and ultra-short duration (5-10 minutes), carrying risk of malignant hyperthermia and hyperkalemia. Rocuronium is a non-depolarizing agent with an onset of 60 to 90 seconds that is reversible with sugammadex. Cisatracurium undergoes organ-independent Hofmann elimination, making it preferred in patients with hepatic or renal impairment.
Stages and Phases of General Anesthesia
Stage I (Analgesia) is characterized by consciousness with diminished pain perception. Stage II (Excitement) involves loss of consciousness with irregular respirations and risk of laryngospasm. Stage III (Surgical Anesthesia) features regular respirations, muscle relaxation, and loss of reflexes. Stage IV (Medullary Depression) represents overdose with cardiovascular and respiratory collapse.
Monitoring Standards
ASA Standard Monitors
The standard monitors include pulse oximetry (SpO2), capnography (end-tidal CO2, mandatory for general anesthesia), electrocardiography (ECG), non-invasive blood pressure (NIBP), temperature monitoring, and inspired oxygen concentration (FiO2).
Advanced Monitoring
The bispectral index (BIS) is a processed EEG measure used to assess depth of anesthesia, with a target of 40 to 60 for general anesthesia. Invasive arterial blood pressure monitoring is used for complex cases. A peripheral nerve stimulator assesses neuromuscular blockade using the train-of-four response.
Office-Based General Anesthesia
OMFS offices must comply with state dental board regulations and AAOMS Office Anesthesia Evaluation standards. Minimum equipment includes an emergency cart, defibrillator, suction, backup oxygen supply, and emergency airway devices. Personnel requirements include a minimum of one dedicated anesthesia team member separate from the surgeon. The recovery area provides continuous monitoring until discharge criteria are met, with a Modified Aldrete score of 9 or above required.
Anesthetic Considerations Specific to OMFS
The shared airway is a defining feature of OMFS anesthesia, as the surgical field and anesthesia circuit occupy the same anatomical space. Nasal intubation is the standard approach for most OMFS procedures to allow intraoral access. Throat pack placement and documentation prevent aspiration of surgical debris. There is risk of accidental extubation during mandibular manipulation. When intermaxillary fixation is used, wire cutters must be at the bedside and clear communication with the anesthesia team is essential.
Malignant Hyperthermia
Malignant hyperthermia is a rare but life-threatening hypermetabolic reaction to volatile anesthetics and succinylcholine. Signs include rapidly rising temperature, muscle rigidity, tachycardia, hypercarbia, and metabolic acidosis. Treatment involves immediate discontinuation of triggering agents, dantrolene 2.5 mg/kg IV, active cooling, and supportive care. Every OMFS office providing general anesthesia must stock dantrolene.
Emergence and Recovery
Smooth emergence minimizes the risk of bleeding, laryngospasm, and agitation. Antiemetic prophylaxis with ondansetron and dexamethasone is critical in OMFS patients at risk of aspiration with IMF. Discharge criteria include stable vitals, adequate pain control, no active bleeding, and ambulation without assistance.
Clinical Pearls
A dedicated anesthesia provider who is not involved in the surgical procedure should always be present. Nasal intubation is the workhorse airway for OMFS but requires assessment for septal deviation and coagulopathy. Capnography is the earliest indicator of airway compromise and should never be omitted. Throat pack placement and removal must be documented on the surgical checklist. Malignant hyperthermia preparedness, including dantrolene stocking, is required in every anesthetizing location.
References
- Haug RH, Perrott DH. "Anesthesia for Oral and Maxillofacial Surgery." In: Miloro M, et al., eds. Peterson's Principles of Oral and Maxillofacial Surgery. 4th ed. Springer; 2022.
- American Association of Oral and Maxillofacial Surgeons. AAOMS Parameters of Care: Office-Based Anesthesia. 2024.
- Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail's Clinical Anesthesiology. 7th ed. McGraw-Hill; 2022.
- Rosenberg MB, Phero JC. "Anesthesia and Pain Control in Dentistry." Anesthesiology Clinics. 2019;37(3):455-470.