Flashcards in Isoflurane Deck (27)
What is the trade name for Isoflurane?
What drug class is Isoflurane in?
General Inhalational Anesthetic
What is Isoflurane (chemically speaking)?
Halogenated methyl ethyl ether
What is the primary use of Isoflurane?
Induction and maintenance of GA
What makes Isoflurane less useful as an induction agent?
What is the MOA of Isoflurane?
Current predominant theory is that target proteins (most likely ion channels/and or receptors) are the site of action of the inhaled anesthetics. Separate sites of action for the loss of consciousness and immobility have been preposed
What are the pharmacokinetics of Isoflurane?
-Small, lipid-soluble molecules that readily cross alveolar membranes
-Isoflurane is specifically a ventilation-limited anesthetic
What does it mean that Isoflurane is a ventilation-limited anesthetic?
It has a high rate of uptake into the bloodstream that prevents the alveolar partial pressure from rising rapidly. Physiologic or pathologic changes that act to increase the rate of rise of the alveolar partial pressure will speed induction
How is Isoflurane metabolized?
-metabolized only slightly (0.2-2%!)
-deflurinated much less than other halogenated agents
-oxidatively metabolized by the liver CYP450 enzymes to form acetylated liver protein adducts
What are the acetylated liver protein adducts capable of?
evoking an antibody response that could occur after exposure to Isoflurane (aka Halothane Hepatitis!)
What can acetylated liver protein adducts cause?
What is the partial pressure of Isoflurane?
240mmHg at 20C
What is Isoflurane's Blood/Gas coefficient and Oil/Gas partition coefficient?
1.4 (intermediate solubility in blood)
91 (solubility in fat)
How is isoflurane eliminated?
Both ventilation and metabolism; but the lungs mostly eliminate isoflurane (only 0.17% of iso is excreted in the urine as urinary metabolites)
What is the volume of distribution for Iso?
The time constant of iso for equilibration of tissue with arterial partial pressure is 2.1 minutes into the vessel-rich group (CNS and visceral organs), 88 minutes into the muscle group (muscle and skin), and 2039 min into the fat group
What are the CNS side effects of Isoflurane?
Dose dependent extensions of pharmacological effects.
Increases CBF and ICP
Particularly at 1 MAC or greater
What are the CV side effects of Isoflurane?
Coronary Artery Vasodilation
Possible exacerbation of cardiac ischemia in CAD
Drop in SVR and BP, mild drop in HR
What happens if Isoflurane concentrations are rapidly increased?
May see transient increase in BP and HR (less than with Desflurane)
What are the Resp. side effects of Isoflurane?
-Respiratory Irritation r/t noxious odor
-Often intolerable in small children/ may lead to a/w events such as laryngospasm and coughing
-Overall decreased Minute Ventilation and
-Decreased response to hypoxia and hypercarbia
-Bronchodilator in maintenance phase
What can happen with MAC >1 with Isoflurane?
attenuates hypoxic pulmonary vasoconstriction promoting hypoxia during one lung ventilation
What is the pattern of breathing with Isoflurane?
Decreased Tidal Volume and increased RR
What are the GI side effects of Isoflurane?
What are the endocrine side effects of Isoflurane?
What are the GU side effects of Isoflurane?
Decreased renal blood flow, GFR, UO
What are the Contraindications with Isoflurane?
Known sensitivity to isoflurane or other halogenated agents, Pregnancy category C, or patients with known or genetic susceptibility to malignant hyperthermia
What are the drug interactions with Isoflurane?
-potentiates the muscle relaxant effect of all muscle relaxants, most profoundly NDMR
-MAC is reduced by accompanying administration of N2O
-Can react with desiccated CO2 absorbents to produce CO, which may result in increased lvls of carboxyhemoglobin in some patients