Anasthetic Agents Flashcards
inhalable anesthetics:
nitrous oxide halothane isoflurane desflurane sevoflurane
advantages and disadvantages to general anesthesia:
- adv: body wide
- disadv: disturbance of all organ systems
advantages and disadvantages to local anesthesia:
- adv: limit anesthesia to small area; minimal system disturbance
- disadv: may not be adequate
IV (fixed) anesthetics:
thiopental
propofol
etomidate
ketamine
two general side effects with anesthetics?
decreased respiration
decreased BP
*What is the triad of anesthesia?
Asleep, pain-free and still
**factors for ideal anesthetic:
1) unconscious - hypnosis
2) amnesia - produce sleep without recall
3) analgesia - abolish pain
4) skeletal muscle relaxation
5) areflexia - eliminate noxious reflexes
6) good minute to minute control
**Adjuvant drugs and conditions given prior to anesthesia to improve outcomes:
1) relieve anxiety - benzodiazepines
2) prevent allergic reactions - antihistaminics
3) prevent nausea and vomiting - antiemetics
4) provide analgesia - opioids
5) prevent bradycardia and secretion -atropine
**Important conditions to know about prior to anesthesia administration?
- *1) CV problems
- *2) respiratory disease
3) altered kidney or liver fx
4) abn tissue blood flow
5) psychiatric history
6) drug/medication/supplement history
7) allergies
8) prior anesthesia history
9) so maaannnnyy!
phases of general anesthesia:
1) induction phase-initial administration until desired level of anesthesia achieved
2) maintenance phase-starts once the desired depth/level of anesthesia is achieved; anesthetic concentration is maintained at or above a minimum necessary to stay at this level
3) emergence phase-waking up period
4) recovery period-from discontinuance of anesthetic agent administration until full restoration of consciousness and normal function
Stages of general anesthesia -effects on the the brain:
- Stage 1: Analgesia- amnesia, euphoria
- Stage 2: Excitement- delirium, combative beh
- Stage 3: Surgical anesthesia- unconsciousness, regular respiration, decreasing eye movement
- Stage 4: Medullary Depression- respiration arrest, cardiac depression and arrest, no eye movement
Commence surgery at what stage of general anesthesia?
Stage 3 - surgical anesthesia-unconsciousness, regular respiration, decreasing eye movement
Anesthetics - MOA?
1) depress spontaneous and evoked neuronal activity
a) induce neuronal hyperpolarization
b) increase firing threshold (lesser activity)
c) inhibit synaptic transmission and response to released neurotransmitters
2) anesthetics may alter ion channel function
* a) increase GABA_A receptor channel activity-enhanced inh neurotransmission and CNS depression
* b)activate voltage-gated K channels - hyperpolarization of neurons and reduced activation
* c) inhibit glutamate NMDA receptors - decreased excitatory neurotransmission
Which anesthetic inhibits glutamate NMDA receptors?
ketamine
Volatile inhalable anesthetic agents:
halothane
isoflurane
gaseous inhalable anesthetic agents:
NO
xenon
Advantages and disadvantages to inhalable anesthetics?
ADV:
-easy to control depth of anesthesia
-readily reversible, minute to minute control
DISADV:
-induction not as fast or smooth as with fixed agents
Inhalable anasthetics - pharmacokinetics:
Factors for uptake and distribution… and rate of onset and recovery…
- anesthetic concentration in inspired air
- pulmonary ventilation rate
- solubility in blood and lipid
- pulmonary blood flow
- arteriovenous concentration gradient
- elimination
Anasthetic concentration in inspired air factor
- relationship partial pressure or tension?
- main partial pressure factor?
- concentration in inspired air is proportional to partial pressure or tension
- partial pressure depends on the ability to vaporize the agents (heat of vaporization) - use of vaporizer
So the higher the inspired anasthetic concentration in the inspired air… then the _____ partial pressure in the lungs which has what result?
- HIGHER the partial pressure in the lung
- results in faster achievement of anesthetic concentration in the blood = gets to the brain faster
Pulmonary ventilation rate factor:
- better ventialation result in more rapid onset of anasthesia
- may be altered by pre-anesthetic medication or in some disease
- **partial pressure anesthetics with higher solubility are affected by ventilation rate
**solubility in blood and lipid factor info:
- Blood:gas partition coefficient (otswald coefficient) - solubility in blood
- brain:blood partition coefficient - solubility in lipid
So the lower the blood gass partition coefficient, then the ____ soluble results in a _____ in partial pressure in blood –> ___ equilibrium with brain and induction.
LESS SOLUBLE
MORE RAPID RISE IS PARTIAL PRESSURE IN BLOOD
FASTER EQUILIBRIUM WITH BRAIN AND INDUCTION
*Pulmonary blood flow/cardiac output factor info:
higher/lower blood flow?
- higher blood flow = slower partial pressure in blood and brain = slower onset (reasoning: more anesthetic distributes to other tissues due to high BF = less drug for brain)
- low blood flow = faster partial pressure rise in blood and brain = faster onset
Arteriovenous concentration gradient factor info:
- dependent on?
- increased difference b/w arterial and venous gas tensions means what?
- dependent on rate and uptake of the anesthetic by the tissues
- increased difference bw arterial and venous gas tensions == SLOWER onset