What are the appropriate remifentanil and propofol dosing regimens for coronary angiography in a 70‑kg adult with normal cardiac function?

Remifentanil and Propofol Dosing for Coronary Angiography

For coronary angiography in a 70-kg adult, start with remifentanil 0.05 µg/kg/min continuous infusion combined with propofol boluses of 10-20 mg every 20-30 seconds until adequate sedation is achieved, avoiding bolus dosing of remifentanil entirely. 1

Initial Dosing Regimen

Remifentanil

• Begin with 0.05 µg/kg/min (3.5 µg/min for 70 kg) as a continuous infusion 1
• The Difficult Airway Society explicitly warns to "avoid bolus dosing" due to respiratory depression risk 2
• Target effect-site concentration of 1-3 ng/mL when using target-controlled infusion 2
• Never use the higher starting dose of 0.125 µg/kg/min recommended for some procedures—this is too aggressive for coronary angiography 1

Propofol

• Administer 10-20 mg boluses every 20-30 seconds until target sedation level is reached 1, 3
• Target effect-site concentration of 0.5-1 µg/mL if using target-controlled infusion 2
• For a 70-kg patient, total cumulative dose typically ranges 35-100 mg over the procedure 4
• Avoid bolus dosing >20 mg to prevent hypotension and respiratory depression 1

Critical Titration Principles

Allow sufficient time between each propofol dose (minimum 20-30 seconds) to assess peak effect before administering additional drug 1. This is the single most important safety measure to prevent over-sedation.

Dose Adjustments During Procedure

• If inadequate sedation: increase remifentanil infusion by 25-50% every 2-5 minutes 1
• If respiratory depression occurs: reduce remifentanil by 50% immediately 5
• The combination produces synergistic respiratory depression beyond either agent alone 1

Mandatory Monitoring Requirements

You must have all of the following in place before starting:

• Continuous pulse oximetry, blood pressure, heart rate, and capnography 1
• A dedicated healthcare provider performing no other tasks during sedation 1
• Supplemental oxygen administration (mandatory, not optional) 1, 4
• Patent IV access maintained throughout and until cardiorespiratory depression risk resolves 1
• Immediate availability of naloxone and airway management equipment 1

Pharmacokinetic Interaction

Propofol increases remifentanil blood concentrations by approximately 46% compared to remifentanil alone 6. This pharmacokinetic interaction explains why lower doses of both agents are required when used together. The interaction is synergistic, not merely additive 7.

Age-Related Dosing Modifications

For patients >65 years:

• Reduce initial remifentanil infusion rate by 50% to 0.025 µg/kg/min 5
• Reduce propofol boluses to 10-15 mg 4
• Elderly patients experience higher peak propofol concentrations due to decreased volume of distribution, predisposing them to hypotension, apnea, and oxygen desaturation 8

Common Pitfalls to Avoid

1. Using remifentanil bolus doses: This causes transient apnea and muscle rigidity 9. Always use continuous infusion only.

2. Starting remifentanil at 0.1-0.2 µg/kg/min: This rate is appropriate for general anesthesia with intubation 5, 10, not conscious sedation for angiography. Start at 0.05 µg/kg/min.

3. Rapid propofol administration: Boluses >20 mg or administration faster than every 20-30 seconds cause dose-stacking and over-sedation 1.

4. Inadequate monitoring: Capnography is essential for early detection of hypoventilation before oxygen desaturation occurs 1.

5. Forgetting that propofol has zero analgesic properties: Remifentanil provides all analgesia; propofol provides only sedation 1, 4.

Expected Adverse Events

• Respiratory depression occurs in 21-46% of patients receiving remifentanil 5, 10, but resolves within minutes of stopping the infusion
• Nausea/vomiting occurs in 27-60% during remifentanil infusion 5, 10 but decreases to 6-21% post-procedure
• Transient hypotension (10-15 mmHg decrease) is common but rarely requires intervention 3
• 5-10% experience oxygen desaturation <90%, typically responding to jaw thrust 3

Recovery Profile

Patients recover rapidly after stopping both drugs, with return of consciousness typically within 5-10 minutes 8. This rapid offset occurs regardless of infusion duration for procedures lasting <2 hours 8.