General Anesthetics Flashcards
Use of general anesthetics (GA)
ONLY for surgery
What methods were used before GA
- Ethanol
- Opiates
- Partial asphyxia
- Cerebral concussion
Then new drugs were discovered:
- Diethyl ether
- Chloroform (esp for pregnancy)
Ideal anesthesia
- Loss of consciousness
- Amnesia
- Analgesia
- Inhibition of reflexes
- Muscle relaxation
- Rapid onset and recovery
- Pleasant experience
- No dangerous SE
- Decreased resp
- Hypothermia
- Nausea and vomiting
Inhaled GAs-Mechanism
Inhalation→CNS→alters memb of neurons
*Inhibition of neuronal firing
Potentiation of GABA neurons
Inhibition of excitatory glutaminergic neurons
Cortex is the most sensitive, then the thalamus
Inhaled GAs-Potency and Toxicity
Factors that influence potency
- More lipid soluble=more potent
- Lower the minimal alveolar conc. (MAC) =more potent
- MAC is the same as ED50
TI=2-4 so dangerous
Inhaled GAs-Induction and Recovery
Speed of induction and recovery:
More soluble in blood=slower
High blood-gas coeffecient (B/G C)=slower
Think of blood as a reservoir that must be completely filled before effects begin
Nitrous oxide
Gas at room temp
B/G C=0.5
*Relatively insoluble in blood so rapid onset
MAC>100%
*Can never reach 100% so not efficacious
- Rapid induction and recovery
- Good analgesia
- Low potency
- No amnesia
SE
- Not soluble in blood so leaves blood and enters body cavities as gas→Pt discomfort
What do we use halogenated hydrocarbons
Maintain anesthesia
-fluranes
The halogenated hydrocarbons
Isoflurane (MAC=1.4; BG C=1.4)
Desflurane
Sevoflurane
SE:
- Increased incidence of liver disease w/ repeated exposure (doesn’t occur anymore)
- Increased Ca uptake by mm→mm rigidity
- Malignant Hyperthemia
- Tachycardia
- Increase body temp
SE treated w/ Dantrolene–inhibits Ca uptake
Dantrolene
Inhibits CA uptake
Treats mm rigidity caused by the halogenated hydrocarbons (-fluranes)
Methohexital
IV GA
Barbituate
Bind to and activate GABAergic neurons
Action terminated by redistribution from brain
Propofol
IV GA
Most common parenteral anesth.
Increase GABA activity
Rapid onset
Short duration
Antiemetic effects
Ketamine
IV GA
Analog of phenylcyclidine (angel dust)
Dissociative anesthesia-profound anesthesia and analgesia
Short induction-short duration
Binds to receptor that inhibits glutamate neuron
Hallucinations in pts emerging from anesthesia
Etomidate
IV GA
Non-analgesic
Conscious sedation
High TI
Activates GABA
Some nausea post op
Midazolam
aka versed
Benzodiazepene
Binds to BD receptor→enhances action of GABA
Anesthesia
