Maintenance Gases (Inhalation Drugs) Flashcards
Vapour pressure
Tendency of a liquid anesthetic to evaporate;
determines whether a precision or non-precision vaporizer is used to deliver the agent
Blood-gas partition coefficient
Measure of solubility of an inhalant anesthesic in blood as compared with alveolar gas;
Indicates speed of induction & recovery one should expect for a given inhalant anesthesic
(**The lower the coefficient the faster the expected induction & recovery) ❤️🩹
Mean alveolar concentration
(MAC)
Lowest concentration at which 50% of patients show no response to a painful stimuli;
Measures potency of the agent & the average vaporizer setting that must be used to produce surgical anesthesia
Isoflurane used for
Induction & maintenance
Precision vaporizer usually used
Stable at room temp
Isoflurane vapour pressure
Higher
@ 750 mmHg and 20 celc: 240
Isoflurane blood-gas partition coefficient
Higher
1.46
In combo w low tissue solubility
Results in rapid induction & recovery
Can change anesthetic depth fast
Isoflurane MAC
Lower
Dogs: 1.3%
Cats: 1.63%
Horses: 0.88%
Usually kept at: 1.5-2.5%
Isoflurane side effects
May vomit
Min liver metabolism
Less costly than second
Fewest adverse CV effects
Metabolism: 0.2%
Sevoflurane
Best for mask & chamber inductions
Precision vaporizer usually used
Popular in equine despite high cost
Sevoflurane Mac
Higher
Dogs 2.34%
Cats 2.58%
Horses 2.34%
Sevoflurane effects
More pleasant odor
Less irritating
Compound a - renal damage
Mod-severe cardiac dz: mask inductions
Metabolism: 2.5%
Doxapram
Emerg drug for Resp depression
Not controlled
Onset: 2 mins
Analeptic
Stimulates breathing & awakening
(Increases tidal volume & RR)
May cause hyperventilation, seizures, hypertension and arrhythmias
Sevoflurane & Isoflurane
Min liver metabolism & renal excretion
Dose related
Not analgesic
Decent muscle relaxer
Crosses placenta
Low fat solubility
Be careful of occupation exposure hazard- use balanced anesthesia
ISO & Sevoflurane CNS
Dose related
Reversible depression (to a point)
Hypothermia
Increased ICP (esp if poor ventilation & CO2 levels increase )
Padding, excitement and muscle fasciculations on recovery (why we use premeds!)
Sevoflurane & iso CV
Depressant
Not arrhymogenic
Dose related vasodilation, Hypoventilation, decreased cardiac output, BP and tissue perfusion
Variable effect on HR
ISO & sevo respiratory
Dose dependant depression
Concentrations of 2-3 x MAC leads to respiratory arrest
Hypoventilation, retention of CO2 & resp arrest
Depression of RR in neonates
Production of carbon monoxide when exposed to desiccated CO2 absorbent
