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32 Cards in this Set
- Front
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MAC significance
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Minimal Alveolar Concentration that will block movement of 50% of patients in response to incision
"relative potency of anesthetic gases" |
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Combination Anesthesia
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multiple anesthetic agents used to take advantage of their best properties and minimize undesirable side effects
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Ketamine
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produces dissociative anesthesia
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Complete Anesthesia
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extremely potent, produce all stages of anesthesia at low concentrations allowing sufficient O2 to patient
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Incomplete Anesthesia
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can NOT produce all stages of anesthesia w/out producing hypoxia
less efficacy than a complete anesthetic |
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Inhaled Anesthesia --mechanism of action
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transfer of the anesthetic from . . .
alveolar air to the blood and from the blood to the brain |
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Concentration of Inhaled Anesthetic
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is proportional to the gas mixture's Partial Pressure
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Dissociative -- anesthetic state
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characterized by catatonia, amnesia, and analgesia,
with or without loss of consciousness (hypnosis) |
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Induction & Recovery (emergence)
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determined by the rate of change of...
Partial Pressure "concentration" of Gas in Brain which is determined by the Partial Pressure of Gas in Arterial Blood |
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Speed of Induction
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correlates with blood/gas partition coefficient
an inverse correlation ie. the smaller the coefficient the more Rapid Onset |
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Induction of Anesthesia
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accomplished via Intravenous Drugs (usually)
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Maintenance of Anesthesia
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accomplished via Inhaled Drugs (usually)
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Ideal General Anesthetic -- Characteristics
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1. provide smooth & rapid Induction of Unconsciousness
2. produce amnesia "memory loss" 3. block troublesome reflexes 4. produce skeletal muscle relaxation 5. produce analgesia "no pain" 6. smooth & rapid Emergent Recovery w/o Long-lasting Adverse effects |
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Blood/ Gas partition coefficient (λ)
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a measure of anesthetic gas's solubility in blood
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Inhalation Anesthetics
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(slow) Ether
(medium) Halothane, Enflurane Isoflurane (fast) Nitrous Oxide, Desflurane, Sevoflurane |
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Halothane
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MEDIUM induction/recovery
Hypotension / Cardiac Arrhythmias Hepatotoxicity with repeated use Malignant Hyperthermia (rare) Metabolism to Trifluro-free radical |
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Enflurane
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MEDIUM induct/recovery
slight risk of Convulsions Malignant Hyperthermia (rare) Less Hepatotoxic than halothane |
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Isoflurane
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MEDIUM induct/recovery
few side effects -- Coronary ischemi in at risk patients Widely used |
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Nitrous Oxide
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FAST induction/recovery
Anemia risk -- w/ repeated/prolonged use Good Analgesic Low potency = sole or combination anesthetic |
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Desflurane
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FAST induction/recovery
Respiratory irritation, cough, bronchospasm used in Day-case surgery (fast onset & recovery) |
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Sevoflurane
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FAST induction/recovery
few side effects theoretical renal toxicity risk due to fluoride widely used in Children |
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Intravenous Agents
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Thiopental (barbiturate)
Propofol -- longer periods of anesthesia Ketamine - dissociative Benzos = diazepam & midazolam Etomidate = short procedures Dexmedetomidine = alpha2 agonist (sedative/analgesic effects) |
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Thiopental-- Rapid onset & Brief duration
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due to redistribution from highly vascular tissue (brain) to less vascular tissue (muscle & adipose)
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Thiopental
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FAST induction/recovery
Hangover effect / Cardiovascular & Respiratory deprs. decreases cerebral bloodflow & O2 consumption (induction use is declining) |
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Etomidate
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FAST onset / FAIRLY fast recovery
Excitatory @ Induction/recovery Adrenocortical suppression Pain at injection site **less cardio-resp effects |
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Propofol
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FAST onset, VERY FAST recovery
Cardiovas-Respiratory depression Pain at injection site **propofol abuse Rapidly metabolized -- can be continuous infusion most common induction agent |
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Propofol
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most common induction agent (intravenous drug)
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Ketamine
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SLOW onset
After effects common in RECOVERY Psychotomimetic effect/ Nausea / Vomiti/ Salivation Cardiovascular stimulation ↑ CSF pressure good amnesia and analgesic |
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Determinants of Gas Partial Pressure in Blood
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1. concentration inspired gas
2. Pulmonary Ventilation delivering agent to lungs 3. transfer from Alveoli to pulmonary circulation 4. transfer from Blood to body tissues |
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Potency
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expressed as activity per weight administered
expressed as (MAC) Minimal Alveolar Concentration MAC correlates with lipid/gas partition coefficient |
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Elmination of anesthetic
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tissue concentration drops and effects are reversed
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Ketamine -- substance abuse
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hallucinatory effects lasting less than 2 hours
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