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Glossary of T2 anesthetics

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What are the two major types of anesthesia?
General (inhaled and intravenous) and Local (injected nerve blocks)
Define General anesthesia.
reversible changes in neurological function that cause: 1. inhibition of stimulatory systems 2. stimulation of inhibitory systems, 3. balace between systems; mechanism poorly understood (there are 4 stages- 1.analgesia, 2.excitement, 3.surgical anesthesia, 4.medullary paralysis - not in handout)
What are the 3 major problems with understanding anesthesia?
1. the definition is unclear and doesn't describe the neurobiology, 2. neurobiology of consciousness is not understood, 3. there are multiple differences and unknowns in the anesthesia pharm agents
Give a general overview of how one would use general anesthesia during surgery.
use an intravenous agent for induction of anesthesia and use an inhalational agent for maintenance of anesthesia.
Why would you give other medications before surgey? Name some and their action.
Benzodiazepines (midazolam,deazepam, reduce anxiety); barbituates (pentobarbital, sedation); antihistamines (diphenhydramine, prevent allergic rxn); opioid (fentanyl, provide analgesia); anticholinergics (scopolamine, amnesia, prevent bradycardia, and fluid secretion); Antiemetics (ondansetrone, prevent aspiration, reduce post-op N/V)
Name the intravenous agents that one would utilize for induction of anesthesia.
Barbituates, Benzodiazepines, etomidate, ketamine, propofol
Name the inhalational agents one would use to maintain anesthesia.
volatile agents (isoflurane, halothane, Sevoflurance, desflurane,enflurane); Nitrous oxide and Xenon
What is the mechanism of action of anesthetics?
Increase GABA's effect on GABAa's receptors; block nicotinic receptors, activate K+ channels, inhibit NMDA (glutamate) receptors, inhibit synaptic proteins (decrease NT release-amnesia); enhance glycine effect on glycine receptors (immobility, since glycine is inhibitory - controls Cl- channel)
What is the Mechanism of action for benzodiazepines, etomidate, and propofol?
enhance GABA's effect on GABAa receptors - enhance inhibition
what is the mechanism of action for anesthetic nitrous oxide?
activating K+ channels and blocks NMDA (glutamate) channels
what is the mechanism of inhaled anesthetics and barbiturates?
enhance GABA's effect on GABAa receptors - enhance inhibition
what is the mechanism of action for ketamine and xenon?
inhibit NMDA (glutamate) receptors - block excitation and activates K+ channels
What anesthetics work by enhancing GABA's effect on GABAa receptors?
BZDs, Barbs, inhaled anesthetics, etomidate, propofol
in regard to inhaled anesthetics, how would one measure the concentration of the Gas?
measure the partial pressure or the "tension"
the inspired gas' partial pressure, ventilation rate, and gas solubility tell you what about the inhaled anesthetic?
these factors will determine the speed of induction or the time it takes from administration to teh achievement of surgical anesthesia
less soluble gas =
faster induction and elimination
what inhalational anesthetics smell good?
sevoflurane and halothane
what inhalational anesthetics smell bad?
desflurane and isoflurane
what is the MAC?
Minimum Alveolar concentration or minimum anesthetic concentration = the concentration of an anesthetic that produces immobility in 50% of patients exposed to it
What is the relationship with MAC, potency and lipophilicity?
the lower the MAC, the higher the potency and more lipophilic
If you mix gases together, how do you measure MAC?
add the MACs together (nitrous oxide is commonly mixed with other agents)
Why is MAC useful?
helps compare anesthetic agents; easily measured, consistent and reproducible
since MAC is changed by many diseases, drugs, physiological states, What happens to MAC in pregnancy, elderly, acute alcohol poisoning, chronic alcoholism?
pregnancy, elderly, acute alcohol poisoning = all DECREASE; chronic alcoholism INCREASES (cross tolerance)
What happens to MAC in hyperthermia?
MAC increases in hyperthermia
What happens to MAC in hypernatremia?
MAC increases in hypernatremia
What happens to MAC in hypothermia?
MAC decreases in hypothermia
What happens to MAC in shock?
MAC decreases in shock
What happens to MAC in elevated CNS catecholamine NT release?
MAC increases
What happens to MAC in CNS depressant drugs?
MAC decreases
What happens to MAC in acute cocaine use?
MAC increases in acute cocaine use
Name the inhaled anesthetics in order of increasing potency or decreasing MAC.
nitrous oxide, desflurane, sevoflurane, ether, enflurane, isoflurane, halothane
nitrous oxide, Halothane, desflurane, isoflurane, and sevoflurane all _________ cerebral blood flow.
increase cerebral blood flow
Halothane, desflurane, isoflurane, and sevoflurane all _________ cerebral oxygen consumption.
decrease cerebral oxygen consumption
Halothane, desflurane, isoflurane, and sevoflurane all _________ intracranial pressure.
increase ICP
What does a decreased cardiac output do to induction speed of an inhaled anesthetic?
a decreased CO will speed up the induction time
What type of tissue in the body will hold an anesthetic the longest?
fat, has low flow and high capacity
Halothane, desflurane, isoflurane, and sevoflurane all _________ tidal volume.
decrease
Halothane, desflurane, isoflurane, and sevoflurane all _________ respiratory rate.
increase
Halothane, desflurane, isoflurane, and sevoflurane all _________ airway resistance.
decrease
Halothane, desflurane, isoflurane, and sevoflurane all _________ ventilatory response to hypercarbia/hypoxemia.
depresses it
Halothane, desflurane, isoflurane, and sevoflurane all _________ renal blood flow.
decrease
Halothane, desflurane, isoflurane, and sevoflurane all _________ GFR.
decrease
Halothane, desflurane, isoflurane, and sevoflurane all _________ hepatic blood flow.
decrease
Halothane, desflurane, isoflurane, and sevoflurane all _________ uterine smooth muscle.
decrease
What inhaled anesthetic increases nausa and vomiting?
nitrous oxide
what is the relationship of blood:gas partitioning coefficient to speed of induction and elimination?
the lower the number, the faster the induction and elimination
Name the inhaled anesthetic. MAC>100%.
Nitrous Oxide
Name the inhaled anesthetic. rapid onset and recovery and a good analgesic.
Nitrous oxide.
Name the inhaled anesthetic. not pungent (used for induction with children), rare induction of hepatitis, medium rate of onset and recovery, and sensitizes the heart to epi-induced arrhythmias.
halothane
Name the inhaled anesthetic. most rapid onset of action and recovery (low PC), poor induction agent, used for maintaince, used for outpatient surgery, irritates the airway and stinks.
desflurane
Name the inhaled anesthetic. used for out-patient surgery, smells good and is not irritating to the airway, useful induction agent, esp. in children.
sevoflurane
Name the inhaled anesthetic. smells bad, replaced by desflurane, potent, medium rate of onset and recovery, least likely to cause nausea.
isoflurane
Name the inhaled anesthetic. considered obsolete; slow onset and recover (large PC), releases F-ions causing renal dysfunction.
methoxyflurane.
used in conjunction with succinylcholine, this inhalant can cause malignant hyperthermia. what is your antidote?
any halogenated GA (halothane); rescue: dantrolene
this inhalant can cause megoblastic anemia after prolonged exposure.
nitrous oxide
many anesthetics cause nausea and vomiting by affecting the chemoreceptor zone in the base of the 4th ventricle. name some Rx.
ondansetron, avoid N2O, droperidol, metaclopromide and dexamethasone

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