GasGasGas - The FRCA Primary Exam Podcast GasGasGas - Comparing Opioids - Viva Style!
Jun 17, 2025
Dive into the world of opioids and their essential role in anaesthesia! Explore comparisons between morphine, fentanyl, alfentanil, and remifentanil, uncovering their unique properties for various clinical scenarios. Learn about dosing strategies for intubation, the significance of context-sensitive half-times, and optimal choices for ICU sedation. Plus, a deep dive into intrathecal morphine and the caution necessary for its use. Get practical tips for exam preparation while staying informed about opioid risks and benefits!
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No One-Size-Fits-All Opioid
- Opioids differ widely in pharmacokinetics and pharmacodynamics, so no single drug suits every scenario.
- Choose an opioid by matching its onset, duration, and side-effect profile to the clinical need.
Match RSI Opioid To Onset And Familiarity
- For RSI consider onset and offset: alfentanil or remifentanil reach peak effect faster than fentanyl.
- Use remifentanil TCI (Minto) targeting 4–5 ng/mL for controlled intubating conditions if familiar with the model.
Context-Sensitive Half-Time Drives Infusion Choice
- Context-sensitive half-time matters for infusions: fentanyl accumulates, alfentanil is shorter, and remifentanil is context-insensitive.
- Remifentanil's half-life (~9 minutes) stays constant regardless of infusion duration.