Inhaled Anesthetics

Inhaled anesthetics are indicated for the induction and maintenance of anesthesia. Desflurane and sevoflurane are the most commonly used medications in this class due to their relative safety profiles.  Any of these medications can precipitate malignant hyperthermia, which is a condition that results from uncontrolled skeletal muscle oxidative metabolism.  There appears to be an autosomal dominant inheritance pattern. Malignant hyperthermia is treated with rapid cooling, supportive cares, and administration of dantrolene.  

Class Drugs

• Desflurane

• Halothane

• Isoflurane

• Sevoflurane

Class Mechanism of Action

Exact mechanism unknown

• Increases sensitivity of GABA receptors to GABA, ultimately leading to hyperpolarization of neurons by increasing chloride ion influx through the chloride ion channel

Class Application

Induction of anesthesia

Class Adverse Effects

Bradycardia

• Responsive to atropine

Hypotension

Malignant Hyperthermia

• Rare disorder affecting certain populations, thought to be inherited in an autosomal dominant fashion

• Uncontrolled increase in skeletal muscle oxidative metabolism resulting in:

Increased oxygen consumption (demand outstrips supply)

• Toxic levels of CO2 production

• Hyperthermia

• Ultimately results in circulatory collapse

• Treatment

Cooling

• Supportive care

• Dantrolene

Blocks release of calcium ions from the SR of muscle cells

Drug Table

Drug Name	Application	Comments	Image
Halothane		Adverse Effects; Liver failure is possible with exposure; Can result in death; Anorexia, nausea, vomiting; Cardiac arrhythmias; Halothane sensitizes the heart to catecholamines, which can lead to arrhythmia	"Halo" "Hanes"
Isoflurane	Used in maintenance of anesthesia; Bad odor causes breath holding, salivation, cough, etc. during induction, so not effective	Adverse Effects; Minimal metabolism makes kidney and liver toxicity rare	"Iso" "Flu Rain"
Desflurane	Outpatient procedures; Low blood solubility gives property of rapid onset and recovery; Used in maintenance of anesthesia; Bad odor causes breath holding, salivation, cough, etc during induction, so not effective	Adverse Effects; Minimal metabolism makes kidney and liver toxicity rare	"Dez" "Flu Rain"
Sevoflurane	Anesthesia induction/maintenance; Low odor; Rapid onset and recovery due to low blood solubility	Adverse Effects; Can form nephrotoxic compounds in the inhalation circuit if flow is too low	"Seven" "Flu Rain"