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126 Cards in this Set
- Front
- Back
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2 old agents that were used for general anesthesia
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Ether
N2O |
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GA's have ________ therapeutic index
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narrow/low
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Stage 1 of anesthesia =
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Analgesia
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In stage 1 of GA = Analgesia, get depression in (2)
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- RAS (general sensory)
- Dorsal horn cells (pain) |
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Stage 2 of GA = ______
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Delirium
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Stage 2 of GA = Delirium --> begins with ______
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Loss of consciousness
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In stage 2 of GA --> depression of ______________ --> results in ______________
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Depression of cortex --> less inhibition of subcortical areas --> Disinhibition
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Disinhibition in Stage 2 of GA can cause 3 dangerous events
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1. Hyperreflexia --> violent muscle ctx
2. Irregular respiration --> apnea alternating with hyperapnea --> probs with stability 3. Vomit --> aspiration, asphyxiation and postop pneumonia |
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Stage 3 of GA = __________
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Surgical Anesthesia
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Stage 3 of GA = surgical anesthesia = (3)
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- Muscle relaxation
- Return to regular RR and BP but at lower set point - Greater depression of RAS and spinal cord |
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Stage 4 of GA = __________
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Medullary paralysis
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Stage 4 of GA = medullary paralysis (3 progressive steps)
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1. Cessation of spontaneous respiration
2. Pons and medulla depression 3. Ends with circulatory failure |
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Objective of uptake and distribution of GA
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Conscious --> unconscious as quickly and safely as possible
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GA Perfusion rate (highest to lowest)
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Brain (highest) --> muscle --> adipose
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Lipid content of tissue highest to lowest
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Adipose --> Brain --> Muscle
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Max blood levels achieved almost instaneously with ____ admin --> much faster than IM
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IV
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IV and IM administration of GA bypass ___________-
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Lung transfer
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3 factors influencing transfer of inhalation GA's
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1. Blood gas partition coefficient
2. Anesthesia concentration in inspired air 3. Pulmonary ventilation |
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Index of "solubility" of GA in blood
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Blood/Gas Partition Coefficient
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High Blood/Gas Partition Coefficient = ________
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- More soluble in blood
- Takes longer to get to tissues (longer induction time) |
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Low Blood/Gas Partition Coefficient = _________-
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GA has limited solubility in blood --> short induction time
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Higher concentration of anesthesia (inc loading dose) = ____________ --> ________-
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Increase rate of transfer --> shorter induction pd
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At stage __ of GA, do not need to give any more
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Stage 3
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Faster and deeper breath = __________
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Faster transfer of drug
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Elimination is slower than induction b/c GA ___________
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is gradually released from tissue storage
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Major route of elimination of inhaled GA's
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Expired Air
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Higher _____ = longer recovery time from GA
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Blood/Gas Partition Coefficient
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Contributes to elimination of GA but is not a major factor
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Biotransformation
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Inc _____ of administration of GA --> tissue stores increase --> longer recovery
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Duration
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GA potency determined by (2)
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Blood Levels
Minimum Alveolar Concentraton (MAC) |
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GA potency factor:
- Used only for inhalation GA's - Assumes that the partial pressure of anesthetic in lung air corresponds to [GA] in brain |
Minimum Alveolar Concentration (MAC)
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1 MAC =
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Concentration of GA in alveolar space at which 50% of pts do not feel initial surgical incision
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95% of all pts do not feel initial surgical incision at ____ MAC
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1.1
(very steep dose-response curve) |
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MOA of GA is probable not realted to ________ b/c very different molecular structures produce GA
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Specific Receptor
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Theory of GA
- Explains access of GA to brain but not MOA |
Myer-Overton (Lipid Solubulity)
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Myer-Overton (Lipid Solubility) theory of GA explained that if something is lipid soluble can get access to brain, but did not explain GA MOA b/c _________
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Increasing the lipid solubility of something does not make it a better GA
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2nd theory of GA MOA
- Cell membrane shifts between gel and liquid - Adding GA will ______ (4) |
- Membrane --> disordered state
- Less openings for channels - Dec Na+ influx --> dec cell activity - Dec Ca 2+ influx --> dec excitatory NTs |
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Prob with interaction with lipid component of cell membrane GA MOA theory
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- There is 1 GA molecule/5000 A^2
- Also 100 lipid molecules/5000 A^2 - Unsure if 1 molecule could have such a large effect |
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Current theory of GA MOA
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Interaction with protein component of membrane of Brain cell
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Interaction with protein component of membrane of brain cell (4)
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- 1 protein/ 5000 A^2
- 1 GA molecule/ 5000 A^2 - 1 GA molecule inactivates protein --> changes ion channel - Result: K+ efflux --> hyperpolarization |
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4th theory of GA MOA
- Interaction with GABA-A R causes: __________- |
- Inc influx of Cl- -->Hyperpolarization
- Imp b/c GABA-A R has multiple sites, so very different complexes may bind |
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Pre-anesthetic used to (4)
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- Relieve Anxiety
- Decrease Secretions - Counteract Bradycardia - Elevate Gastric pH |
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Given pre-anesthetic to relief anxiety
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BZ's --> esp Midazolam
(any CNS depressant will enhance) |
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Given pre-anesthetic to decrease salivary and bronchial mucous secretions
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Scopolamine
(much better than atropine) |
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Given pre-anesthetic to counteract Bradycardia
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Atropine
(much better than scopolamine) |
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Pre-anesthetic given to inc gastric pH
(dec scarring of lung tissue by acidic gastric contents if pt vomits) |
Cimetidine
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GA objectives (3)
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1. Rapid elimination of consciousness
2. Skeletal muscle relaxant 3. Analgesia |
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No single current GA can cause rapid unconsciousness, muscle relaxant and analgesia --> therefore 2+ GA's + adjunctive are used = ___________
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Balanced Anesthesia
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GA - Balanced Anesthesia Protocol (3)
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1. Induction agent (usually rapid GA)
2. GA 3. Adjuncts - Muscle relaxants (NM blocking agents) - Opiods |
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2 Adjuncts in GA
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- Muscle relaxants (NM blocking agents)
- Opiods |
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Problems with biotransformed GAs (2)
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- Pre-exiting enzyme induction
- Obesity (inc adipose) |
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- Inhalation gas anesthetic
- Not flamable or explosive |
N2O
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Concentration of N2O
- Analgesia = morphine - dec Beta-endorphin levels |
20% N2O / 80% O2
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Concentraion of N2O
- Dentists use - No respiratory depression |
50% N2O / 50% O2
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Concentration of N2O
- highest conc that provides adequate oxygen (no hypoxia) |
65% N2O / 35% O2
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Concentration of N2O
- most pts unconscious - Stage 2 could cause sickle cell crisis in pts with condition |
80% N2O / 20% O2
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Concentration of N2O
- Not used b/c still won't take pts into stage 3 |
100% N2O
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N2O uses (2)
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1. Analgesia (dentists, MI, labor 1st stage)
2. GA induction |
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Advantages of N2O (2)
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- Rapid
- Pleasant |
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Disadvantages of N2O (3)
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- Not potent
- No skeletal muscle relaxation - Dreams of sexual assault |
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Acute toxicity with N2O (2)
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- Pt falls --> bone fx
- Death from positional asphyxia |
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Chronic Toxicity with N2O (4)
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- Ataxia
- Leg weakness - Peripheral neuropathy (reported in dentists) - Impotence |
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Used in whip cream cans for preservation
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N2O (whip its)
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- Volatile liquids are ______ GAs
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Inhaled
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Halothane is a potent GA --> 1 MAC at _____
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.75% concentration of air
(so can give pt lots of O2) |
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- 15-20% is biotransformed
- Nonexplosive/flammable - Rapid induction - Bronchodilation - Low toxicity incidence |
Halothane
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Halothane disadvantages (5)
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- Poor analgesia
- Poor muscle relaxant - Cardiac arrhythmias - Hepatitis - Hypotension |
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Causes sensitization of the myocardium --> can cause cardiac arrhythmias
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Halothane
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Can cause hepatitis
- not dose related - could be allergic rxn - rarely fatal |
Halothane
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2 mechanism by which Halothane cause Hypotension (has a lower set point)
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- Decreased myocardial ctx --> (b/c dec Ca2+)
- Decrease compensatory tachycardia |
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- Volatile liquid GA
- Most potent GA (1 MAC = .16%) - Slow induction (B/G = 12) |
Methoxyflurane
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Compared to halothane, methoxyflurane provides (3)
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- More muscle relaxation
- More analgesia - Less myocardial ctx |
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Methoxyflurane = Significant biotransformation (50-70%) results in (3)
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- Toxic F- levels for 2-4 days
- Damaged renal system - Fluoride diabetes insipidus |
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- Has increased incidence of fluoride toxicity with longer operation
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Methoxyflurane
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Methoxyflurane use
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Limited to analgesia during labor (small dose only)
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4 volatile liquid GA's
- all potent compounds |
Enflurane
Isoflurane Desflurane Sevoflurane |
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Volatile liquid GA
- Has less production of F- in kidney --> less nephrotoxocitiy |
Sevoflurane
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Volatile liquid GA
- May cause seizures |
Enflurane
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Volatile liquid GA
- More respiratory irritation than halothane - Limited biotransformation |
Isoflurane
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Volatile liquid GA
- HIGH incidence of respiratory tract irritation |
Desflurane
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IV GA categories (3)
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- Barbiturates
- Non Barbiturates - Dissociative Agents |
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- IV
- Barbiturate - Anesthesia occurs within seconds |
Thiopental
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- Rapid emergence due to redistribution from brain to other tissue (not biotransformation)
- Stored in adipose --> slow release |
Thiopental
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Thiopental use (2)
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- GA induction
- Sole GA for short procedures w/o significant pain |
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Thiopental advantages (3)
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- Easy to admin (can control IV better than inhaled)
- Rapid induction - Pleasant induction |
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Thiopental disadvantages
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- Lack of moment to moment control (b/c IV)
- Poor analgesia --> may cause hyperalgesia - Respiratory depression - Poor skeletal muscle relaxation |
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Poor analgesia --> may actually cause hyperalgesia
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Thiopental
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Thiopental contraindication
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Pts with porphyria
(may cause N/V, paralysis, death) |
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- Nonbarbiturate IV
- Not analgesic - Major use = induction of GA - Minimal effects of HR, CO, circulation |
Etomidate
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Etomidate uses (3)
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- GA induction (within 1 mins --> lasts 3-5 mins)
- Supplement GA during short op - Prolonged sedation of critically ill |
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- Nonbarbiturate
- Rapid liver metabolism --> kidney excretion |
Etomidate
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ADRs:
- Injection site pain - Hypotension, tachycardia, arrhythmias - Hyperventilation, apnea, laryngospasm, hiccups - Post op N/V - Myoclonic jerks after injection |
Etomidate
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1 ADR = Myoclonic skeletal muscle movements
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Etomidate
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Nonbarbituate
- Emulsion - combo of lipid and water - Rapid and wide distribution to highly perfused tissue |
Propofol
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Nonbarbiturate
- Hypnosis within 40 secs - GA in 1-3 mins - Some analgesia activity |
Propofol
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Can be used continously for continuous sedation in pts on mechanical ventilation in ICU
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Propofol
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Propofol uses (3)
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- Continuous sedation in ICU pts
- GA induction - Maintain GA in balanced anesthesia |
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Extensively biotransformed into inactive metabolities
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Propofol
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Has rapid recovery from GA
t 1/2 = 300-700 mins |
Propofol
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Propofol ADRs (5)
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- Injection site pain
- Seizures - Hypersalivation - Bronchospasm (hyperventilation) - Green urine / urinary retention |
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ADR = seizure and muscle jerk mvmts
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Propofol
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ADR =
- Green urine - Hypersalivation |
Propofol
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Propofol - cautioned in use in pts with
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Increased ICP
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Not recommended for delivery --> can case neonatal depression
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Propofol
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Has caused fatalities in pediatric ICU --> usually those with RT infection
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Propofol
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Propofol is not good for use in (3)
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- inc ICP
- Delivery - Peds in ICU with resp tract infection |
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Aka PCP or Angel dust
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Phencyclidine
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Dissociative Agent
- Better than morphine b/c has same analgesia but does not dec BP or RR |
Phencyclidine
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Used in vet office
But not in humans b/c adverse psychological rxns (hallucinations) |
Phencyclidine
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Dissociative agent
- Produces dissociative amnesia (not true GA) |
Ketamine
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- Pt appears to be in trance: catatonia, analgesia, amnesia
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Ketamine
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Pt appears to be in trance
- Eyes are open - Unresponsive to pain and other stimuli |
Ketamine
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Ketamine primary sites of action (2)
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- Limbic system
- Cerebral cortex |
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Ketamine action shortest --> longest
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Unconsciousness (shortest)
Analgesia Amnesia (longest) |
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Ketamine advantages (4)
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- Strong analgesia
- No resp depression - Inc HR and BP - Less psychological ADRs than PCP |
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Ketamine disadvantages (3)
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- Prolonged storage in body (trace in urine wks later)
- Some psychological ADRs - Flasbacks up to 1 yr after admin |
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- Causes some psychological ADRs (hallucinations, delirium, schizoid, nightmares)
- More often in pts > 30 - Dec with diazepam pre-medication, avoid tactile/verbal stimulation, counsel pt before |
Ketamine
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Can cause flashbacks 1 yr after admin
- Memory phenomenon - NOT still in body |
Ketamine
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Ketamine uses (4)
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- Emergency surgery
- Outpatient procedures - Changes in burn dressings - Dx procedures in kids |
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Causes increased risk of nephrotoxicity with methoxyflurane
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Tetracyclines
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Antibiotics that cause increased muscle paralysis with NM blocking agents in GA (3)
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- Bacitracin
- Aminoglycosides - Polymixins |
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Acutely caused increased effects when used with GA's
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CNS depressants
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Chronically, when CNS depressants given with GA's cause (2)
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- Inc effect if used during surgery
- Dec of GA effect if tolerance has previously developed |
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May require increased doses of GA due to enzyme induction
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Smokers
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Combo of neuroleptic agent + opiod --> not widely used
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Neuroleptanalgesia
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Neuroleptanalgesia
- Combo of Neuroleptic + opiod - May cause signif resp depression - Use: minor surgery, endoscopy, change burn dressing - Causes: dec emotions and initiative But no effect on intelligence and coordination |
Innovar
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