Volatiles Flashcards
What is the MAC of sevoflurane
2
What is the MAC of Desflurane
6.5
What is the MAC of Isoflurane
1.17
What is the MAC of Enflurane
1.63
What is the MAC of Halothane
0.75
What is the blood:gas coefficient of Sevoflurane
0.69
What is the blood:gas coefficient of Desflurane
0.42
What is the blood:gas coefficient of Isoflurane
1.4
What is the blood:gas coefficient of Enflurane
1.90
What is the blood:gas coefficient of Halothane
2.54
What are the metabolites of Sevoflurane, and how much is metabolized?
Inorganic and organic fluorides
Compound A in the presence of soda lime and heat
Also compounds (B-E)
3.5% metabolised
What is compound A
A toxic compound produced by interaction of Sevoflurane with CO2 absorbers
Causes renal tubular necrosis in rodent models in concentrations >300ppm after 3hrs exposure. Human threshold is ~150ppm
Unlikely to be clinically relevant as ~20ppm measured at low flow rates after 5hrs
What are the metabolites of Halothane
Trifluoroacetic acid
Cl-, Br-
20% metabolised
What are the metabolites of Enflurane
Inorganic and organic fluorides
2% metabolised
What are the metabolites of Isoflurane
Trifluoroacetic acid and F-
0.2% metabolised
What are the metabolites of Desflurane
Trifluoroacetic acid
0.02% metabolised
Outline the cause of Halothane hepatitis
Immune mediated hepatits
Antibodies are formed against liver microsomal proteins on the surface of hepatocytes that have been covalently modified to form neoantigens by the reactive oxidative trifluoroacetyl halide metabolite of halothane
How do volatiles produce CO
volatile agents interact with sodalime or baralyme absorbers to form CO
Des > Enf > Iso
Production is worse if the CO2 absorber is hot and dry (eg after a machine is left idle overnight/weekends)
