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153 Cards in this Set
- Front
- Back
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IAs were discovered by these 2 types of practitioners in the US and England
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physicians and dentists
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The most commonly used inhaled anesthetic in modern anesthesia include _____ and ____.
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a single gas and volatile liquids
(n20, halothane, enflurane, iso, sevo, des) |
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____ of the IAs meet all of the criteria of an ideal IA, and the _______ differ among the drugs.
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none, chemical characteristics
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This is the first IA synthesized by the chemist Joseph Priestly. Later, Sir Humphrey Davy observed its ability to produce analgesia and wrote a book about its beneficial effects during surgery. Davy also gassed himself w it for a toothache.
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N20
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This drug was first used during "frolics" for recreational purposes, and researched by William Morton to show that its effects mimicked those of N20
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Diethyl ether
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This drug was first used by James Simpson for labor cases, but there were unexplained intraop. deaths of healthy pts and numerous cases of hepatotoxicity
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chloroform
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These 3 agents were used between 1920 and 1940, had faster and more pleasant induction and emergence. However, they were flammable and halogenated entirely w chlorine, making them toxic
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ethylene, cyclopropane, divinyl
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Put these in order of introduction: isoflurane, sevoflurane, desflurane
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first iso, then des, then sevo
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IAs exist in these 2 forms
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liquid and gas
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Liquid IAs are packaged in
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glass or plastic containers
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IAs are poured as a liquid into agent-specific _____.
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vaporizers
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From vaporizers, IAs are carried into the anesthesia breathing circuit as vapors by ____.
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fresh gas flow
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Early IAs were ____, had prolonged ____ and were ____.
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unstable, prolonged effect, flammable
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_____ reduces flammability
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halogenation
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______ reduces solubility
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fluorination
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_____ groups add stability
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trifluorcarbon
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______ precipitate arrythmias
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alkanes
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What are the CV effects of IAs?
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decrease myocardial contractility, vasodilate, decr CO, incr CVP, decr BP, decr SVR
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What are the resp effects of IAs?
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depress hypoxic ventillatory drive, incr RR, decr TV, bronchodilate, blunts HPV (incr shunt), incr PaCO2
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What are the cerebral effects of IAs?
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incr CBF, incr ICP, decr CMRO2
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What is the neuromuscular effect of IAs?
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augments NDMR, muscle relaxation
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What is the hepatic effect of IAs?
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decr hepatic blood flow
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What are the renal effects of IAs?
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decr RBF, decr GFR --> decr U/O
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IAs undergo biotransformation through this enzyme in the hepatic system through _____.
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CYP 450
Oxidation |
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Halothane, introduced in _____, was a halogenated ____, preserved in the bottle was ____ to reduce oxidation.
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1956, alkane, thymol
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_____ is the most commonly used agent worldwide, and is very inexpensive.
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Halothane
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What are the CV effects of halothane?
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direct myocardial depression, sensitizes heart to arrythmias
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What are the resp effects of halothane?
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potent bronchodilator, "Sweet" nonpungent odor
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What are the cerebral effects of halothane?
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decrease CVR and incr CBF, blunts autoregulation, may alter CPP
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What are the neuromuscular effects of halothane?
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synergistic NDMR, MH trigger
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What are the renal effects of halothane?
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decr RBF, decr GFR
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What are the hepatic effects of halothane?
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decr blood flow, decr drug clearance, primarily excreted by exhalation but also significant liver metabolism
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When is halothane contraindicated?
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liver dz, intracranal mass, severe hypovolemia
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This complication results from multiple short exposures to a particular IA, and the oxidative metabolite binds to liver cells and causes autoimmune response
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halothane hepatitis
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All agents except _____ are metabolized by the liver
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sevoflurane
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___ was introduced in 1972, is similar to isoflurane, and its metabolism to inorganic fluorine can cause seizure activity.
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enflurane
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This IA was introduced in 1980, has a pungent ether-like odor, and is a chemical isomer of enflurane
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isoflurane
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CV effects of isoflurane?
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minimal CV depression, mild incr HR (Dose dep), decr SVR, dilates coronary arteries (Coronary steal)
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Resp effect of isoflurane?
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irritating to upper airway
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Cerebral effect of isoflurane?
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greater IMAC = incr CBF/ICP, decr CMRO2 and 2 MAC produces silent EEG
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Neuromuscular effects of isoflurane?
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MH trigger, synergistic NMDR
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Renal effects of isoflurane?
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decr RBF ,decr GFR, decr UO
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Hepatic effects of isoflurane?
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decr blood flow - less than halothane
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____ Was introduced in the 1980s, is halogenated w fluorine, and has nonpungent odor.
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sevoflurane
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CV effects of sevoflurane?
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mild depression myocardial contractility, little effect on HR, decr CO, prolonged QT
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Resp effects of sevoflurane?
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decr RR, bronchodilator
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Cerebral effects of sevoflurane?
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similar to iso - incr CBF/ICP, decr CMRO2, 2 MAC- silent EEG
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Neuromuscular effects of sevoflurane?
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augments NDMR
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Renal effects of sevoflurane?
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slight decr RBF, impaired renal tubule fcn
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Does sevo have hepatic effects?
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no change in hepatic blood flow
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___ causes an incr in inorganic Flourine ion - inducing renal dysfunction
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sevoflurane - nephrotoxic
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_____ is the product of degradation of sevo by CO2 absorbent, and is nephrotoxic.
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compound A
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Sevo-induced nephrotoxicity risk is increased when
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low flow anesthesia (2L/min), dry CO2 absorbent, when used w current/prior renal dysfunction
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_____ was introduced in the 1980s, and has similar structure to isoflurane. The F atom is substituted w a Cl atom causing profound physical property effects.
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desflurane
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____ has a very high vapor pressure, requiring a special vaporizer, as it will boil at room temp. It also has low solubility.
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desflurane
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CV effects of desflurane?
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dose dependent decr in SVR, CO unchanged, dose dependent incr in HR, doesnt incr coronary artery blood flow
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Resp effects of desflurane?
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pungent odor, decr TV, depr PaCO2 response, coughing, breath holding, laryngospasm
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Cerebral effects of desflurane?
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incr CBF, decr CMRO2
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Neuromuscular effect of desflurane?
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synergistic w NDMR
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Does desflurane have renal or hepatic effects?
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nope!
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CV effects of N2O
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decr myocardial contractility but incr overall CV function, induces catecholamines and can cause arrhythmias
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Resp effects of N2O
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tachypnea, decr TV, doesnt effect MV and PaCO2, inhibits hypoxic drive, incr PVR
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Cerebral effects of N20
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incr CBF/CBV, increases ICP
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Does N20 have neuromuscular effects?
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no but enhances muscle relaxers
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During general anesthesia, a known concentration of anesthetic gas is administered via an anesthesia breathing circuit through ____ to the patient.
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ventilation
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Anesthetic gas enters the lungs, alveoli, passes through the ______ into the blood, to the left side of the heart, and is distributed to _____.
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alveolar membrane, tissues of the body
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Initially the _______, then the muscles, skin, fat, and connective tissues are perfused w blood/anesthetic gas mixture
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brain and vital organs
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5 effects of general anesthesia
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analgesia, amnesia, muscle relaxation, LOC, immobility
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Induction w IA is good for these scenarios
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pediatrics, mentally challenged, adults w/o IV access
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_____ are the most popular agents for maintenance in adults and peds.
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IAs
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Stage 1 of anesthesia
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analgesia: initial analgesia without amnesia (complete or partial inability to remember), ends with analgesia nad amnesia
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Stage 2 of anesthesia
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excitement: patient is delirious and excited but amnesic, irregular resp, retching and vomitng, incontinence, ends w reestablishment of regular breathing
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Stage 3 of anesthesia
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surgical anesthesia: begins w recurrence of regular resp and extends to complete cessation of spontaneous resp, 4 planes of stage 3 (Depending on changes in ocular mvmts, eye reflexes, pupil size)
most reliable indications - loss of eyelash reflex, establishment of resp pattern that is regular in rate and depth |
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stage 4 of anesthesia
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medullary depression: cessation of spontaneous respiration, severe depression of vasomotor and resp centers in medulla
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Pharmacokinetics
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how body affects a drug, relationship between drug dose, tissue concentration and elapsed time
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IAs undergo ____ From alveoli into systemic circulation
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uptake
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Distribution and elimination of IAs is by the ___ or metabolism principally by the ____.
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lungs, liver
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By controlling the _____ a gradient is created such that the anesthetic is delivered from the machine to the brain.
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inspired partial pressure
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The primary objective of IA is
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to achieve a constant and optimal brain partial pressure (PBr) of the anesthetic
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The brain and other tissues equilibrate with the partial pressure of the IA delivered to them by the _____.
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arterial blood (Pa)
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The blood equilibrates w the _____ of the anesthetic.
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alveolar partial pressure (PA)
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What is the goal of uptake and distribution of IAs?
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to achieve brain concentrations of anesthetic agents that promotes amnesia and analgesia
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IAs are standardized according to their
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MAC (min alveolar concentration)
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How does blood solubility affect FA (Alv conc)?
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the higher the blood gas concentration, the greater the solubility and uptake by the pulm circulation
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How does alveolar blood flow affect FA (alv conc)?
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the greater the uptake, the slower the rise of alveolar concentration
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Low cardiac output predisposes the patient to
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overdose w soluble agents
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Partial pressure difference between the alveoli and venous blood depends on
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tissue uptake
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A high ____ is necessary during initial admin of IA.
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FI -- initial high FI offsets impact of uptake into blood and accellerates induction of anesthesia as reflected by rate of incr in PA, this is known as concentration effect
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The higher the FI, the more rapidly the ____ approaches the FI. The higher FI provides anesthetic molecule input to offset ____ And speeds the rate at which the FA increases.
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FA, uptake
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How does A-a gradient affect Fa (art conc)?
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due to dead space and venous admixture, there is non-uniform alveolar gas distribution, resulting in VQ mismatch
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The greater the RR and volume, the faster the rate of rise of ____ to _____.
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alveolar partial pressure, inhaled partial pressure
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_____ agents are taken up by the blood less readily than ___ agents; as a result, the alveolar concentrations rise faster and induction is faster.
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insoluble, soluble
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The higher the blood gas partition coefficient, the greater the anesthetic's _____ and the greater its ____ by the pulmonary circulation.
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solubility, uptake
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Lowering of alveolar partial presure by uptake can be countered by
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increasing alveolar ventilation
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The effect of increasing ventilation will be most obvious in raising the ____ for soluble anesthetics.
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FA/FI
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For insoluble agents, increasing ventilation has ____ effect.
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minimal
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___ increases rate of rise of FA; _____ decreases rate of rise of FA.
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hyperventilation, hypoventilation
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Elimination of rebreathing, high fresh gas flows, low anesthetic-circuit volume, low absorption by the circuit, decr solubility, high cerebral blood flow, and incr ventillation all contribute to
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speeding induction and recovery
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This is the ability of the high volume uptake of one gas increases the alveolar partial pressure of a second gas-- high inhaled partial pressure of first gas results in higher alveolar partial pressure of the first and second gases
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second gas effect
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The second gas effect is easily seen with volatile agent coadministration with
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N20
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Rise of alveolar concentration toward inspired concentration is most rapid with ___ agents such as ____ and least rapid with ____ agents.
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least blood soluble agents, N20, most blood soluble agents
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Blood gas coefficient of N20
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.47
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Blood gas coefficient of halothane
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2.4
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Blood gas coefficient of methoxyflurane
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12
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Blood gas coefficient of enflurane
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1.9
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Blood gas coefficient of isoflurane
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1.4
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Blood gas coefficient of desflurane
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0.42
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Blood gas coefficient of sevoflurane
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0.65
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What factors affect the transfer of IA from blood to tissues?
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tissue solubility, tissue blood flow, and difference between partial pressure of arterial blood and tissue
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what are the vessel rich tisue groups
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brain, heart, lungs, liver, kidney, endocrine organs
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What arethe vessel poor groups of tissue
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bone, ligament, hair, teeth, cartilage
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What is the order of blood flow compartment filling?
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vessel rich > muscle > fat > vessel poor
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What effect does N20 have on bone marrow?
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suppression
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Elimination of IAs is dependent on the
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concentration
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Discontinuing the IA leads to a decrease in the partial pressure in the alveoli and causes the agent to ______
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diffuse away from the tissue
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3 elimination routes
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biotransformation (CYP450),
Transcutaneous loss (insignificant), exhalation |
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This is the most important route for elimination
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exhalation
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Factors that speed induction also speed elimination, such as
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incr FGF, incr ventilation, high CBF
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IAs are eliminated in the order from
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vessel rich to vessel poor tissue groups
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Pharmacodynamics
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how the drug affects the body, study of drug action and toxic effects
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This theory states that IAs work on specific GABA receptors by a neuroinhibitory neurotransmitter
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agent specific theory
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This theory states that all anesthetic agents affect cells the same way because potency is related to lipid solubility (Based on meyer-overton rule)
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unitary theory
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This theory states that lipophilic agents bind to and expand the cell membrane, making them less functional
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critical volume hypothesis
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____ may work by disturbing membrane shape, altering membrane conductance (disturbed ion channels, altered synaptic functions) or altering ligand gated ion channels (GABA enhancement, NMDA receptors)
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IAs
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MAC
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concentration at which 50% of the population wil move under surgical stimulation -- doesnt include addition of other agents like narcotics
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MAC 95%
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1.3,
has been shown to inhibit mvmt in 95% of all pts |
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MAC awake
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typically 0.3-0.5% of the MAC
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MAC BAR (don't move at all)
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1.5
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Factors that affect mac
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temp, age (young incr, decr 6% per decade), intoxication/drugs (acute/chronic), anemia, hypotension, pregnancy
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Highest MAC need is in
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infant up to 6 months
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Mac decreases ___% for each degree decrease in C temp
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7%
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MAC of N20
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104
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MAC of desflurane
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6
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MAC of sevoflurane
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2
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MAC of enflurane
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1.63
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MAC of isoflurane
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1.2
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MAC of halothane
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0.75
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The higher the MAC, the ___ potent the agent
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less
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The more potent the agent, the ___ lipid/oil soluble.
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more
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The higher the blood gas coefficient, the more ____ and ___ the agent.
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soluble, slower
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Since the MAC of N2O is 105%, you cant give 1 mac because
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it would be a hypoxic mixture -- must always give at least 30% Fi02
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____ is the only inorganic compound used, and it supports combustion. It is insoluble compared to other IAs
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N20
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N20 will fill air containing cavities, and is contraindicated in
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pneumothorax, venous air embolism, pneumocephalus, inner ear sx, bowel obstruction
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Renal effects of N20
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decr RBF and GFR
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Hepatic effects of N20
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mild decr blood flow
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GI effects of N20
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incr n/v
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metabolism of N20
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cyp450 in the liver
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N20 inhibits ____ synthesis, which is important w pregnant women and can cause congenital anomalies or spontaneous abortion.
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Vit B12
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This is the reverse of the second gas effect, and occurs when the elimination of N2O from the alveoli proceeds at a greater rate than other agents - N20 dilutes alveolar air and available O2 resulting in hypoxia
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diffusion hypoxia
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N2 is ___ less soluble in blood than N20.
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34x
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This condition is genetically linked, involves the uncoupling of the RYR causing prolonged skeletal muscle contraction (massive release of Ca2+ from SR of skeletal muscle causing contraction and heat production) -- can be fatal!
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MH
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Triggers for MH
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succinylcholine and IAs
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This toxic molecule can build up as a result of desflurane degradation by old baralyme, and can be avoided by regularly changing baralyme.
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CO
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