inhalant anesthetics

liquid anesthetics

• liquid anesthetic is vaporized and delivered by carrier gas to pt through inspiratory tubing

diffusion of anesthetic gas

• gas anesthetic crosses alveoli to the bloodstream

• rate of diffusion is controlled by concentration gradient

during induction

• concentration of gas in alveoli is high

• concentration of gas in bloodstream is low

• results in rapid diffusion of anesthetic gas

depth/maintenance of anesthesia

• depth is determined by concentration of anesthetic in the brain

• anesthesia is maintained by insuring concentration of anesthetic in alveoli, blood and brain is maintained

recovery

• when concentration of gas in blood is less than brain anesthetic will diffuse from brain to blood to alveoli

• as levels in brain decrease, pt will regain consciousness

after vaporizer is turned off

• animals should breathe 100% O2 for up to 5 min

precision vaporizers

• deliver inhalants as %

• are VOC, bc they sit outside the breathing circuit

VOC

• vaporizer out of circuit

• create high resistance to gas flow so they sit out of the breathing circuit

nitrous oxide

• N2O

• not common in vet med

• wide margin of safety

• provides analgesia, muscle relaxation, and sedation

• blue cylinder

nitrous oxide- risk of hypoxia

effects of inhalant anesthetics

physical properties of inhalant anesthetics

• vapor pressure

• solubility

• MAC

vapor pressure

• measure tendency of anesthetic to go from liquid to gas

• high vapor pressure = wants to be a gas

  • need to be used with VOC

solubility

• solubility coefficient measures to solubility of an anesthetic gas

• provides info on speed of induction, depth change and recovery

• low solubility = fast gas

  • move rapidly to the brain

high solubility inhalants

low solubility inhalants

MAC

halothane

• high vapor pressure

• medium solubility

• medium MAC

halothane- adverse effects

halothane — effects

isoflurane

• higher MAC

• high vapor pressure

• low solubility

isoflurane- effects

sevoflurane

• lowest solubility

• highest MAC

• high vapor pressure

sevoflurane- effects

desflurane

malignant hyperthermia