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19 Cards in this Set

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Meaning of Anesthesia
insensible or without feeling
Effects of general anesthesia
* Reversible CNS depression
* Absence of awareness (unconsciousness)
* No recall of events at conscious level (amnesia)
* Insensitivity to pain (analgesia)
* Muscle relaxation
* Diminished motor response to noxious stimuli (immobility)
What are the 4 stages of anesthesia?
1. Stage I = stage of voluntary movement
2. Stage II = stage of delirium or involuntary movement
3.Stage III = surgical anesthesia
4.Stage IV = CNS extremely depressed, respiration ceases
• Weak or imperceptible HR, absent reflexes, acutely dilated eyes, loss of mm. tone
What occurs during Stage I anesthesia?
*stage of voluntary movement*

* From time of drug administration to loss of consciousness

* Tachycardia, hypertension, irregular resp rate, reflexes intact, salivation, muscle tone present
What occurs during Stage II anesthesia?
*stage of delirium or involuntary movement*

* Loss of voluntary control (excitement stage)

* Irregular resp rate, salivation less, reflexes present but depressed, nystagmus (esp. horses and cows)
What occurs during Stage III anesthesia?
**surgical anesthesia**

* Unconsciousness with progressive depression of reflexes

* Progressive bradycardia, progressive resp depression, minimal mm. tone
What occurs during Stage IV anesthesia?
* CNS extremely depressed, respiration ceases*

* Weak or imperceptible HR, absent reflexes, acutely dilated eyes, loss of mm. tone
Why is anesthetic solubility in blood and body tissues such an important factor?
* Determines rate of uptake and distribution

* Determines rate of induction and subsequent recovery

* Solubility in lipid is closely related to anesthetic potency; tendency to dissolve influences management and admin.
What is the solubility coefficient?
extent to which gas will dissolve in a given solvent
What is the partial coefficient?
* Conc. ratio of anesthetic in 2 solvent phases

* Describes affinity of an anesthetic for one phase compared to another phase of that solvent (describes how the anesthetic partitions itself between 2 phases at equilibrium)
Anesthetic uptake is influenced by what?
1. Solubility
2. CO
3. Difference in anesthetic PP between alveoli and venous blood
What is the blood/gas partition coefficient?
The ratio of an anesthetic in the safe phase (blood & gas)

* Basically how it will partition itself between the two phases (affinity)
What does it mean if an anesthetic has a low blood/gas PC?
o Low – wants to pass thru blood to CNS so causes induction faster (recovery faster too)
What does it mean if an anesthetic has a high blood/gas PC?
High – wants to stay in blood so diffusion takes longer
Sequence of events: how anesthetics enter the body?
1.Vaporizer
2, Lungs
3. Blood
4. CNS (brain/spinal cord)
How does CO affect induction of anesthesia?
• Increased CO means decreased time for diffusion from inspired air to blood = slower induction

* Decreased CO means increased time for blood-gas exchange= faster induction
When does the largest gradient between alveolar and venous PP occur?
Largest gradient between alveolar and venous PP occurs during induction
MAC
minimum alveolar conc. of anesthetic that anesthetizes 50% of patients
How is anesthetic potency determined?
Anesthetic potency = 1/MAC

(sevoflurane MAC > Isoflurane MAC = isoflurane is more potent)