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110 Cards in this Set
- Front
- Back
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elimination of IA occurs primarily via
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lungs
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route of IA
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FGF-FI-FA-Fa-brain
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partial pressure and volume % is determined by
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solubility
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...is when to offset uptake, the concentration of inspired gas is increase
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overpressurization
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aveolar ventilation can offset what is taken up by blood, this effect...
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This effect is less with an agent less soluble in blood
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Inhaled anesthetics effect their own uptake by
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dose-dependent respiratory depression
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Increased in c.o. causes more rapid uptake and a decrease in rate of rise of P alveolar & _________ induction
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slower
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the effect of CO is...
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Most prominent with a soluble anesthetic
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Alveolar-to-venous partial pressure differences
Reflects the... |
Reflects tissue uptake of anesthetic
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The fraction of anesthetic removed from blood as it passes through the tissues depends on
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Solubility of anesthetic in tissue
Blood flow Partial pressure difference |
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After ....time constants or... min uptake is decreased due to decreased inspired-to-alveolar partial pressure difference (saturation of vessel-rich groups)
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3/15 min
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The concentration effect has two components
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1) concentation effect 2) tracheal inflow
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augmentation of tracheal inflow creates a..
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creates a negative pressure which pulls in more inspired gas
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w/the concentration effect..the makes the biggest difference
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decrease in lung volume
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concentrating effect is the result of
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Concentrating Effect: Concentration of the inhaled anesthetic in a smaller lung volume due to uptake of all gases from the lung
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Concentration effect is more significant with than with the volatiles as
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nitrous, can be given at higher concentrations
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As temp decreases...solubility...
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INCREASES
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Volitiles
OG coef BG coef tissue coef |
OG/potency
BG/induction tissue/emergency |
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BG
Halothane Isoflourane Enflourae |
H 2.54
Iso 1.46 En 1.9 |
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BG
N20 Des Sevo |
N20 .46
Des .42 Sev .69 |
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OG
Halothan ISo Enf |
halothane 224
ISO 98 Enf 98 |
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OG
N20 Des SEve |
N20 1.4
Des 17 Sevo 55 |
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If Desflurane has a lower solubility than nitrous oxide, why does nitrous equilibrate (FA/Fi) sooner?
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this is the concentrating effect; you would have to use more nitrous
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Time Constant =
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capacity/flow
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fat blood flow
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fat blood flow of 2-3 ml/100 grams/minute
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1 time constant = 63% change
2 time constants = 86% change 3 time constants = 95% change 4 time constants = 98% change |
1 63%
2 86% 3 95% 4 98% |
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if the capacity of the machine is 8L
the fresh gas flow is 4L/min what is one time constant |
2L
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If Iso was dialed in at 2%, what would be the change
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63%
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vrg are ...% of Co and ..% of body mass
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CO 75%
BM 9% |
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what is the Time to 50% ↓ in anesthetic concentration independent of duration
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context sens 1/2 time
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Advantages of MAC as a potency measure
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Very reproducible
End-tidal concentration is an index |
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MAC limitations
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Limitations
Patient is either anesthetized or not MAC represents a whole population (or 50%) not response of a single patient Only applies to anesthetic gases Difficult to measure plasma brain concentration of IV anesthetics |
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Substituting a of low atomic weight such as for one of higher atomic weight such as , potency
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halogen, F
such as CL decreases potency |
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Which drug has F subsituted from Cl and is less potent
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Desflourane - CL
Isoflourane- F |
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....mac potency correlates to action on
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spinal cord
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Addition of nitrous oxide to carrier gas .....MAC of the volatile
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decreases
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using 70% nitrous and 30% o2 w/Volitile will .....the mac... by
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decrease by 1/2
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MAC awake
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MACawake: the average concentration permitting voluntary response to a command
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mac awake halothane
iso, des, sevo nitrous |
Halothane 1/2
Iso, des, sevo 1/3 nitrous 60% |
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Agents with higher MACawake/MAC ratio are
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poorer providers of amnesia (nitrous oxide)
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Normal pharyngeal function requires the anesthetic concentration to be at levels of
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0.1 MAC or less
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mac ratio for laryngoscopy
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equal or greater than MAC
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mAc BAR;;
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considerably in excess of MAC
blocks autonomic reflexes |
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hypothermia ....MAC
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decreases
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MAC
Young Elderly |
young..increases
old..decrease |
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cocaine..mac
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increases
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anemia...mac
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decreases
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hypercalcemia ..mac
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decreases
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hypernatremia
hyponatremia |
hyponatremia..increase
hypernatremia..decrease |
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ephedrine mac
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increases
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acute amphetamines, chronic..mac
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acute, increase
chronic decrease |
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etoh..mace
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acute, decrease
chronic increase |
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pregnancy effects on MAC
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by 8 weeks gestation , decrease
by 72 hrs post delivery, normal |
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MAC Halothane
VP |
MAC .75
VP 243 |
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MAC Enflourane
VP |
MAC 1.7
VP 175 |
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ISO MAC
VP |
MAC 1.29
VP 240 |
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SEVO MAC
VP |
MAC 2.0
VP 160 |
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DES MAC
VP |
DES MAC 6.0
VP 680 |
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Nitrous MAC
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105%
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...sig increases ICP, Cerebral flow
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Halothane
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....is 50% metabolized
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methoxyflourane
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...is 18-20 % metabolized
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halothane
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..is 2-3 % metabolized
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sevo
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..is less than .1% metabolized
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DES
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...seizures
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enflourane
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normal cerebal blood flow
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50-55 ml/100 grams of brain tissue/minute = 750 ml/min = 15% resting C.O.
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↑ CBF 2°
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↑ PaCO2
↑ [H+] ↓ oxygen concentration |
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greatest effect on cerebral flood flow increase is w/
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halothane
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All inhaled agents produce dose-dependent...... in cerebral metabolic oxygen requirements
greater effect w/ .... |
decrease
iso |
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decrease.....cerebral metabolic rate creates and opposition to...
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vasodilation
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Cerebral metabolic rate begins to ↓ at ..... probably due to the transition from wakefulness to loss of consciousness
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.4 mac
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......is used to counter act the increased CBF due to halothane
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hyperventilation
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carbon dioxide has...on the brain
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vasodilating.
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EEG: frequency decreases and maximum voltage occurs at
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1mac
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mAP decreases w/halothane because of..with other volitiles because of
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HALOTHANE-CO
others. SVR |
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HR- Volitiles
HR halothane |
Halothane, decrease HR because of decreased contractility
others, increase |
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steal prone anatomy
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Total occlusion of major coronary artery
90% stenosis by collateral distal to the occlusion 12 % of patients |
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.....is associated with coronary steal syndrome
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iso
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resp. side effects of volitiles
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↑ respiratory rate
↓ tidal volume ↓ minute volume ↑ PaCO2 Ventilatory response to hypoxemia ↓ Airway resistance ↓ |
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apnea occurs @ ..mac
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Apnea at 1.5-2 MAC
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...is more of an airway irritant than other VA
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Desflourane
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% of adults develop mild self-limited postop liver toxicity following halothane
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20
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halothane hepatitis is an...response
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immune mediated
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HH is less likely in
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children
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rate 0f hh
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1 in 10,000 - 1 in 30, 000 adults following halothaner
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all vol produce dose dependant decrease in GFR and renal blood flow. T?F
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T
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flouride induced nephrotox can be caused be two agents
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methoxyfl and enflourane
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signs of flouride induced nephrotox
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Polyuria, hypernatremia, hyperosmolarity
Inability to concentrate urine so urine is hypo-osmolar |
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Vinyl halide nephrotoxicity
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Compound A formed when sevoflurane reacts with CO2 absorbents
Dose-dependent nephrotoxin |
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nitrous ....produce skeletal muscle relax
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no
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Ether-derived volatiles produce.... skeletal muscle relaxation of halothane
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twice
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most potent volitile trigger of mal. hyp
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halothane
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nitrous oxide causes/not myocardial contractility decrease
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yes
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se of nitrous oxide, gi
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PONV
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Prolonged exposure to n20 can result in b
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one marrow depression (megaloblastic anemia) & neurological deficiencies exhibited by: Peripheral neuropathies
Pernicious anemia (vitamin B-12 deficiency) |
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s
Pernicious anemia (vitamin B-12 deficiency) caused as a result of |
Inhibits enzymes that are vitamin B-12 dependent including …
Methionine synthetase (necessary for myelin formation) Thymidylate synthetase (necessary for DNA synthesis) |
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Contraindications for n20
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Air embolism, pneumothorax, intestinal obstruction, etc
Pulmonary hypertension (↑PVR) Abdominal surgery |
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N20 effects on PVR
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increase
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n20 can/not support combustion
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yes
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halothane structure
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Halogenated alkane, alkyl halide
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which volitile is the most potent bronchodilator
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halothane
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contraindications for halothane
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Hepatic dysfunction
Epinephrine use Pheochromocytoma Myocardial depression exacerbated by beta-blockers & calcium channel blockers Dysrhythmias with concurrent aminophylline use |
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problem w/methoxyflouran
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p450 metabolism metabolized it into renal toxic compunds
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iso: 3 cardiac side effects
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Minimal cardiac depression because CO is maintained by ↑HR
Mild beta stimulation Coronary steal 2° coronary artery dilation |
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iso is metabolized to....extent of enflourane
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.1
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desflourane has a... subsitution on Iso
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F
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..va has Minimal cardiac depression because CO is maintained by ↑HR
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desflourane
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va is Is degraded by dessicated carbon dioxide absorbent into clinically significant carbon monoxide levels
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desflourane
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va is a resp irritant
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desflourane
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to ensure that minimal compound a degredation by sevo...
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Recommend gas flow of at least 2 liters/minute
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