GasGasGas - The FRCA Primary Exam Podcast Gas Gas Gas - Compartmentalised Volatiles and a brief jaunt with Sevoflurane
Sep 27, 2024
Dive into the fascinating world of volatile anaesthetics and discover how they interact within the breathing circuit and patient. Explore the differences between sevoflurane, isoflurane, and desflurane, including their clinical nuances and washout times. Unpack the importance of the blood-gas partition coefficient and its role in anaesthetic uptake. Learn about strategies for speeding emergence and the impact of fat stores on recovery. This engaging discussion combines pharmacology with practical insights, perfect for those in the field!
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Volatile Properties Determine Clinical Behaviour
- Volatile agents differ by physical properties like boiling point, saturated vapour pressure, blood-gas and oil-gas coefficients which shape onset, potency and offset.
- Learning relative values (e.g., desflurane vs sevoflurane) helps predict clinical behaviour and choice.
Optimize Circuit And Ventilation For Faster Onset
- Consider circuit size, fresh gas flow, leaks, FRC, alveolar minute ventilation and cardiac output when aiming for rapid onset.
- Optimise mask seal, increase fresh gas flow and minimise dead space to speed induction.
How Partition Coefficients Predict Effect
- Blood-gas and oil-gas partition coefficients together explain onset and potency: low blood-gas speeds onset; high oil-gas increases potency but can prolong emergence.
- Extremely lipid-soluble agents may act potently yet persist in tissues, delaying recovery.