| MAC | Blood:gas coefficient | Oil:gas coefficient | Molecular weight | Boiling point | SVP at 20ºC | Safe ppm |
| 1.2% | 1.4 | 98 | 184.5 | 48.5ºC | 33.2kPa | 50 |
- Irritant
- Pungent smell
Isoflurane
Isoflurane
- Isoflurane is a halogenated ethyl methyl ester
- It has a chiral carbon and is a structural isomer of enflurane
Metabolism
- 0.2% metabolised by CYP2E1 subfamily
- Trifluoroacetic acid
- Inorganic fluoride ions
Respiratory
- Pungent smell may cause irritability, coughing and breath-holding
- Significant reduction in VT and therefore increases PaCO2
- Causes some bronchodilation
Cardiovascular
- Causes:
- Reduced myocardial contractility and therefore cardiac output
- Reduced SVR
- Reflex tachycardia suggests carotid sinus baroreceptor reflex is preserved
- Net effect is a reduction in mean arterial pressure
- May have myocardial protective properties via effects on ATP-dependent K+ channels
- Can cause Coronary Steal Syndrome
- Normally responsive coronary arterioles vasodilate
- Unresponsive/diseased arterioles don't vasodilate
- Blood is diverted away from diseased arterioles, causing worsening ischaemia
- May not occur if coronary perfusion is maintained
Neurological
- Reduces CMRO2
- Increases CBF when MAC >1, otherwise preserves autoregulation
- Can cause burst suppression on EEG
- Significant potentiation of muscle relaxation and some uterine relaxation
- Purportedly some analgesic properties
- The -CHF2 group may react with dry soda lime or baralyme to produce carbon monoxide
- If a circle system is left with dry gas circulating, subsequent use of isoflurane may cause carbon dioxide release
- Enflurane and desflurane also possess -CHF2 groups and may react similarly