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Old definition of anesthesia (the 4 pillars or 4 As)
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Controlled, reversible state of:
amnesia (with LOC)
analgesia
akinesia (skeletal muscle relaxation)
autonomic and sensory reflex blockade
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New definition of anesthesia
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State of reversible come intentionally induced by drugs in which the pt is not arousable, even w/ painful stimuli:
intervention often required to support the airway
spontaneous ventilation often inadequate
CV fxn may be impaired
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Balanced anesthesia
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General anesthesia w/ several agents, possibly a mixture of inhalational and IV meds
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Regional anesthesia
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Local anesthetics that numb a particular part of the body and can be supplemented w/ sedation
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Combined technique and its advantages
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Use of regional anesthesia and general anesthesia at the same time
often allows used of lower dose of general anesthetic (good for pt w/ many comorbidities) and useful for procedures that cannot logistically be done w/ just regional but have significant post-op pain amenable to a regional (ie thoracotomy)
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Sedation
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Pt remains arousable when given an IV agent that induces analgesia, anxiolysisk, and often amnesia but consciousness is maintained
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Minimal sedation (analgesia) changes in:
responsiveness
airway
spontaneous ventilation
CV fxn
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Normal response to verbal stimuli
unaffected
unaffected
unaffected
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Moderate sedation changes in:
responsiveness
airway
spontaneous ventilation
CV fxn
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Purposeful response to verbal or tactile stimuli
no intervention necessary
adequate
usually maintained
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Deep sedation changes in:
responsiveness
airway
spontaneous ventilation
CV fxn
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Purposeful response w/ repeated or painful stimuli
intervention may be required
may be inadequate
usually maintained
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General anesthesia/analgesia changes in:
responsiveness
airway
spontaneous ventilation
CV fxn
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Unarouseable even w/ painful stimulus
intervention often required
frequently inadequate
may be impaired
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ASA physical status classification
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I: no medical problems other than localized indication for sx that can be cured w/ sx
II: one or more systemic diseases under good control which do not limit function
III: one or more systemic diseases which are not in perfect control or limit fxn to some extent (cancer, dialysis, most PVD pts)
IV: systemic condition which is a constant threat to life
V: expected to die w/in a day, sx is a desperation measure (80 yr old w/ ischemic bowel; sx even w/ 75% mortality b/c w/o sx mortality ~100%)
VI-E: brain-dead pt for organ harvesting
E: emergency, add to any status
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General process of general anesthesia from pre-op to PACU
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Pre-op eval, consent,counseling
IV
premed (usually BDZ)
to OR
IV induction
neuromuscular blocking agent
intubation
maintenance
emergence
extubation
recovery
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Characteristics of thiopental (barbiturate)
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- crosses BBB rapidly and is short acting even though elimination half life is several hours b/c redistribution half life is very short; the slow release from tissues is not enough to reanesthetize the pt but enough to work for synergism w/ other drugs
- dose dependent decr in SVR, MAP, CO
- potent resp depressant (apnea)
- reduces CMRO2 and CBF
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Side effects of etomidate
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Potential adrenocortical depression
myoclonic movements
N&V
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Propofol uses
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Useful as a sedation/induction agent w/ amnestic and anti-emitic properties and least residual sedation/faster and more complete awakening
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