Opioid-First Administration Protocol – Alberta
The implementation of the Minto pharmacokinetic model for remifentanil and the Marsh model for propofol (ke0 = 0.26 min⁻¹) with Target-Controlled Infusion (TCI) pump technology allows for precise administration of sedation. This protocol starts with remifentanil to provide analgesia, followed by titration of propofol to achieve moderate sedation.
- Ke0: The rate constant for equilibration between plasma and effect-site concentrations.
- Model Comparison: The original Marsh model (ke0 = 0.26 min⁻¹) aligns closely with the Eleveld model’s t₁/₂ke0 (3.5 minutes). Once approved by Health Canada, the Eleveld model incorporated within newer TCI pumps will become the standard for intravenous sedation practice.
- Current Status: Propofol, remifentanil, and TCI pumps are Health Canada-approved for dental sedation.
Step-by-Step Administration: Opioid-First Protocol
1. Preparation
Equipment:
- TCI pump compatible with the Minto (remifentanil) and Marsh (propofol) models.
- Monitoring devices: ECG, pulse oximeter, non-invasive blood pressure (NIBP), capnography, and modified EEG for brain function monitoring.
- Emergency airway management and oxygen supplementation equipment.
Patient Assessment:
- Conduct a thorough history and physical examination, documenting patient age, gender, height, weight, and comorbidities.
- Input patient data into the TCI pump algorithm.
- Complete an i.v. sedation and airway assessment.
- Obtain informed consent after explaining the procedure, associated risks, and benefits.
2. Induction Phase: Start with Remifentanil (Minto Model)
- Initial target (effect-site concentration): 0.5–1 ng/mL.
- Begin at 0.5 ng/mL to assess response.
- The Minto model incorporates covariates like age, gender, weight, and height to optimize infusion rates.
- Observe:
- Onset of analgesia (reduced response to stimuli).
- Respiratory rate and oxygenation (monitor for early signs of respiratory depression).
- Hemodynamic stability (e.g., bradycardia or hypotension).
- Titrate:
- Slowly increase to a maximum of 1 ng/mL as needed based on procedural pain and patient response.
3. Add Propofol for Sedation (Marsh Model)
- Initial target (plasma concentration): 0.5 μg/mL.
- Start propofol infusion after remifentanil achieves effective analgesia.
- Use total body weight (TBW) for dosing calculations; ensure accurate weight input.
- Observe the sedation over a 3–5 minute period as the propofol stabilizes at the effect-site. Assess if this sedation level is appropriate for moderate sedation for the patient, if not then titrate in small doses to increase the level.
- Gradual titration:
- Increase by 0.2–0.3 μg/mL increments to achieve moderate sedation.
- Typical plasma concentration range: 1.0–1.5 μg/mL.
- Monitor sedation depth:
- Ensure patient responsiveness to verbal commands or light tactile stimulation.
- Maintain spontaneous breathing and airway reflexes.
- Administer the local anesthesia
4. Maintenance Phase
- Maintain target concentrations based on clinical response:
- Remifentanil (Minto): 0.5–1.5 ng/mL.
- Propofol (Marsh): 0.5–1.5 μg/mL.
- Adjust doses dynamically to manage:
- Patient movement or discomfort indicating insufficient sedation.
- Hemodynamic changes (e.g., hypotension from propofol, bradycardia from remifentanil).
- Use local anesthesia (e.g., articaine) to reduce the need for higher sedative doses.
5. Monitoring During the Procedure
- Oxygenation and ventilation: Pulse oximetry and capnography to detect early respiratory depression.
- Hemodynamics: Regular monitoring of blood pressure and heart rate.
- Sedation level: Use a clinical sedation scale (e.g., MOAA/S) alongside brain function monitoring to confirm moderate sedation.
6. Recovery Phase
- Gradually reduce remifentanil and propofol, allowing for equilibration time to ensure smooth recovery.
- Ensure the patient is fully alert, able to maintain their airway, and meets discharge criteria (e.g., Modified Aldrete score).
Key Considerations
- Initial Analgesia with Remifentanil: This approach allows lower propofol doses, minimizing the risk of deep sedation.
- Model Limitations:
- The Marsh model does not account for lean body mass or age; use caution with elderly, obese, or hemodynamically compromised patients.
- These patients may need longer equilibration times or smaller dose adjustments to avoid over-sedation. Go Low, Go Slow Approach
- Effect-Site Titration: Always wait for equilibration before adjusting doses to avoid over-sedation or delayed response correction.
- Airway Safety: Closely monitor for respiratory depression. Keep airway management tools and supplemental oxygen readily available.
Time to Equilibration with the Marsh Model for Propofol
1. Initial Dose (0.5 μg/mL)
- Time to effect-site equilibration (T₁/₂ke0): Ke0 = 0.26 min⁻¹ implies a T₁/₂ke0 of ~2.67 minutes.
- Clinical effects typically stabilize within 3–5 minutes.
- Time-to-Peak Effect (TTPE): Approximately 5–6 minutes.
2. Subsequent Dose Adjustments (0.2–0.3 μg/mL)
- Equilibration Time: Remains 3–5 minutes per adjustment.
- Smaller increments may require the full 5 minutes to observe subtle changes, especially at lower sedation levels.
3. Practical Recommendations
- Reassess sedation depth (e.g., using MOAA/S) after each adjustment.
- Monitor respiratory and hemodynamic parameters to ensure safe titration.
- In elderly or compromised patients, allow extra time for equilibration to avoid over-sedation.
Summary
- Initial dose (0.5 μg/mL): Wait 3–5 minutes for stabilization.
- Incremental adjustments (0.2–0.3 μg/mL): Wait 3–5 minutes for full effect assessment.
By adhering to these guidelines, dentists can achieve stable, moderate sedation tailored to procedural requirements, ensuring patient safety and comfort throughout the dental procedure.