Pharmacology Of Inhaled Surgical General Anesthetics Flashcards
General anesthesia definition
Loss of consciousness, feeling and protective reflexes
Side effects:
- analgesia
- amnesia
- skeletal muscle relaxations
What was the first anesthesia?
Diethyl ether inhalation
- nitrous oxide
stages of general anesthesia
1) stage of analgesia
- loss of conscious w/ loss of pain
- amnesia can be developed here
- inhibits cerebral cortex
2) stage of excitement
- patient is delirious/excited
- respiration is irregular
- can vomit and or incontinent
- elevated blood pressure and heart rate
- once the hypothalamus takes over this stage occurs
* this is the stage to avoid, or minimize during anesthesia treatment*
3) stage of surgical anesthesia
- regular respiration and blood pressure occurs
- continues until regular respiration ceases
- subdivided into 4 phases based on eye movements and pupil reflexes
- ventilators must be present
* you have to try to keep patient in this stage*
4) stage of medullary depression
- severe depression of vasomotor and respiratory centers
- kills patient
* DONT get in this stage*
Induction vs maintenance in anesthesia
Induction:
- time required to take a patient from consciousness -> stage 3
Maintenance:
- ability to keep patient safely in stage 3
Examples of inhaled anesthetics
Nitrous oxide
Flurane agents
MOA:
- inhibt excitatory synapses by blocking NMDA receptors
- enhance inhibitory synapses in CNS by agonist activity to GABAa receptors
What determines the rate of induction
Time required for therapeutic Concentration of inhaled anesthetic that gets into the CNS
Solubility in anesthesia
Most important factor effecting transfer of general anesthesia from lung -> blood
Blood:Gas partition coefficient
Determines the solubility of an inhaled drug
High coefficients indicate the drug is more soluble in blood
- higher solubility in blood = slower onset for action (this is bad)
How to combat high blood:gas partition agents
Administer at higher dose intitally and reduce for maintenance
Also can give in conjunction with a low solubility agent (nitrous oxide)
What determines the time to recovery from anesthesia?
Rate of elimination of general anesthesia from the brain
measured by the brain: blood coefficient
- lower number = quicker recovery