General Anesthetics

What are the indications for oral pre-anesthetic agents?

prepping pts for surgery

• anxiety relief

  • hypnosedatives: diazepam/phenobarb

• decreasing GIT mobility + bronchial secretions

  • anticholinergics: atropine

• subside pain

  • analgesics: morphine

• relax skeletal muscles

  • NM blockers: succinylcholine chloride

What is one major criteria for induction (IV) anesthetic agents?

must be FULLY water soluble

Thiopental sodium

• induction agent

• barbiturate derivative

• fast acting

  • lipophilic sulfur → fast entry to CNS

• short acting

  • rapid metabolism by aliphatic hydroxylation

• injection as Na salt

Why should IV solutions, like thiopental sodium, not be mixed with acidic pH solutions?

precipitation will occur

Ketamine

• induction agent

  • very powerful central analgesic

• MOA: glutamate antagonist

• ketone

• amine

• injected as HCl salt → NO alklaline solution mixtures!

Etomidate

• induction agent

• MOA: GABA potentiation

• ethyl ester

• imidazole ring

  • basic nature

• sedative

If etomidate were to be given as a HCl salt injection, why would it need to be solubilized with propylene glycol and ethanol?

to protect ester from acidic pH

Midazolam

• induction agent

• MOA: GABA potentiation

• given as HCl salt (do not mix w/ alkaline solutions)

• benzodiazepine

  • sedation + muscle relaxation

Propofol

• induction agent

• MOA: GABA potentation

• 2 isopropyl groups

• phenol → low acidity

  • given as emulsion w/ soya oil and glycerol

• produces hypnosis + sedation

Clonidine

• induction agent

• central alpha 2 agonist → reduces sympathetic outflow

• 2-imidazoline group

• given as HCl salt injection intrathecally

Gamma-hydroxybutyric acid

• induction agent

• bioisotere of GABA

• MOA: direct GABA and DA agonist

• given as Na salt injection

• produces sleep + sedation (NOT hypnosis)

T/F: Inhalation anesthetic agents lead to total loss of all sensations

TRUE

Nitrous oxide

• inhalation agent → “laughing gas”

• very powerful central analgesic

• may cause hypoxia

Diethyl ether

• inhalation agent

  • volatile liquid

• 2 ethyls

• flammable properties → halogenation efforts (hypnosis)

Halothane

• inhalation agent

  • volatile liquid → nonflammable

• hepatotoxic (due to halogenated C’s)

• produces sleep and sedation

  • NO muscle relaxation

Methoxyfluorane

• inhalation agent

  • volatile liquid → somewhat flammable (due to ether)

• 2 Chloros and 2 fluoros (NO bromos like halothane)

• ether structure

• produces analgesia + muscle relaxation

What is the structural difference between halothane and methoxyflurane?

• halothane: 3 fluoros + 1 bromo

• methoxyflurane: 2 fluoros, 2 chloros, ether

What is the clinical difference between halothane and methoxyflurane?

• halothane: sleep + sedation ONLY

• methoxyflurane: analgesia + muscle relaxation ONLY

Sevoflurane

• inhalation

  • volatile liquid

• halogenated ether

• produces analgesia and muscle relaxation

SATA: Which anesthetic agents have flammable properties?

a. diethyl ether

b. propofol

c. halothane

d. methoxyflurane

e. ketamine

a. diethyl ether

d. methoxyflurane (somewhat flammable)

SATA: Which inhalation agents do NOT cause sedation?

a. halothane

b. methoxyflurane

c. nitrous oxide

d. sevoflurane

e. diethyl ether

b. methoxyflurane → analgesia + muscle relaxation

c. nitrous oxide → analgesia

d. sevoflurane → analgesia + muscle relaxation

What inhalation agents cause muscle relaxation AND analgesia?

• sevoflurane

• methoxyflurane