Inhalation agents for anesthesia

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Inhalation agents for anesthesia

Inhalation agents are anesthetics that you inhale. Inhalation anesthetics are used to both begin (induce) and maintain general anesthesia. Induction with inhalation agents is preferred for small children and adults when it would be difficult to give anesthetics through a vein (intravenously, IV).

Inhalation anesthetics are often preferred for general anesthesia because they are easy to give through a face mask, an endotracheal (ET) tube, or a laryngeal mask airway (LMA). They also act quickly and wear off relatively quickly. However, after they wear off, inhalation anesthetics do not provide any long-lasting relief from pain (analgesia).

The most commonly used inhalation agents include:

• Potent inhalation agents, which provide complete general anesthesia without additional medications. The most commonly used potent inhalants include desflurane (Suprane), isoflurane (Forane), and sevoflurane (Ultane). The potent inhalants are delivered mixed with oxygen. They may be combined with nitrous oxide to allow the potent agent to be used at a lower concentration, which decreases undesirable side effects and risk of complications.
• Nitrous oxide, which is commonly called "laughing gas." Nitrous oxide is an odorless, colorless gas that relieves pain and has milder effects that cause forgetfulness (amnesia) and sleepiness (hypnosis). This is sufficient for many minor procedures such as dental work, but nitrous oxide must be combined with other sedatives, analgesics, and anesthetic medications to provide full general anesthesia for more painful or extensive procedures. It is given in a mixture with oxygen.

Anyone receiving inhalant anesthetics for general anesthesia is closely monitored because the anesthetics can strongly affect the central nervous system and cardiovascular system and significantly affect breathing, heartbeat, blood pressure, and other vital functions.

Some inhalation agents have an unpleasant odor and may irritate the respiratory tract. This irritation may cause coughing and muscle spasms in the voice box, or larynx (laryngospasm), or in the bronchial tubes in the lungs (bronchospasm). Sevoflurane is less irritating to the airway than the others and is preferred for inducing anesthesia in children.

All the potent inhalation agents are capable of triggering malignant hyperthermia (MH), a rare inherited (genetic) disorder that is potentially fatal.

Credits

Last updated:	March 21, 2006
Author:	Ralph Poore
Reviewed By:	Kathleen Romito, MD - Family Medicine, John M. Freedman, MD - Anesthesiology
Editors:	Susan Van Houten, RN, BSN, MBA, Pat Truman