Topic 17: Anesthetic Agents & Adjucts Flashcards
Dissociative Anesthetic - what kind of substance?
Only drug?
A controlled substance
Ketamine - only legal one
Dissociative Effects on the CNS (6)
ketamine
- Cataleptoid state
- Intact reflexes
- Ocular effects
- Muscle tone
- Analgesia
- Sensitivity to sensory stimuli
Dissociative Effects Ketamine - Ocular effects
Eyes remain open (therefore must keep eyes moist), Central dilated pupil, MUST use ophthalmic ointment
Dissociative Effects on the CNS
(ketamine)- Intact reflexes
Palpebral, corneal, pedal, PLR, laryngeal, swallowing
Dissociative Effects on the Cardiovascular System?
is it good?
- Increase in heart rate
- Increased cardiac output
- Increased mean blood pressure
- Effects due to stimulation of the SNS *So while it seems much safer for patients with heart disease, cardiac workload and myO₂cardial make sick hearts work harder!
Dissociative Effects on the Respiratory System
- Respiratory rate and tidal volume remain stable
- Respiratory depression usually insignificant
- Apneustic (what’s this?) respiration at higher doses
Dissociative Anesthetic (ex Ketamine) reversal agent ?
NO reversal agent
Dexmedetomidine
Precedex
α₂-agonist sedative
Etomidate
Amidate
Noncontrolled, sedative-hypnotic imidazole drug with no analgesic properties
Etomidate (amidate) - CV effects?
Minimal effects on the cardiovascular
and respiratory systems!
Precedex
Dexmedetomidine
α₂-agonist sedative
Amidate
Etomidate
Noncontrolled, sedative-hypnotic imidazole drug with no analgesic properties
Benzodiazepines - are what kind of substances?
Tranquilizers-all controlled substances
Benzodiazepines (3 drugs)
Diazepam (Valium)
Lorazepam (Ativan)
Midazolam (Versed)
Diazepam
(Valium)
Benzodiazepines
–Not water soluble (should only be administered concurrently with opiods, thiopental, & propofol)
–Don’t mix with water-soluble drugs!
Lorazepam
(Ativan) Benzodiazepines -Water soluble/poorly lipid soluble. -Decreasing use in open-heart *D.O.C. for symptomatic treatment of recreational stimulant overdose
Diazepam (Valium) - dont mix with what?
–Don’t mix with water-soluble drugs!
Benzodiazepines
*As with most other anesthetics & sedatives & hypnotics it targets what receptors ?
Υ-amino-butyric acid receptors (GABA) since GABA is the major inhibitory CNS neurotransmitter
Benzodiazepines potentate what?
Potentate general anesthetics
Benzodiazepines - Cardiovascular and respiratory system effects?
Minimal effect with a high margin of
safety
*D.O.C. for symptomatic treatment of recreational stimulant overdose.
Lorazepam (Ativan)
Midazolam (Versed) solubility?
Water soluble
Benzodiazepine side effects - memory?
Also cause antegrade amnesia
Benzodiazepine Reversal
Flumazenil (Anexate)
Flumazenil
(Anexate)
Benzodiazepine Reversal
Most Commonly used Halogenated Organic Compounds
Isoflurane and sevoflurane
Uptake and Distribution of Halogenated Organic Compounds Diffusion rate is dependent on what?
concentration gradient (alveoli/capillary &/or opposite sides of oxygenator membrane/pseudomembrane) and lipid solubility
Uptake and Distribution of Halogenated Organic Compounds Distribution to tissues is dependent on what?
blood supply
Lipid solubility determines entry into tissues through cell walls (why?)
Uptake and Distribution of Halogenated Organic Compounds: Maintenance of anesthesia is dependent on what?
sufficient quantities of anesthetic delivered to the lungs &/or oxygenator bundle fibers.
Reducing amount of anesthetic administered
reduces amount delivered to the alveoli/oxygenator
Uptake and Distribution of Halogenated Organic Compounds: Depth of anesthesia is dependent on what?
partial pressure of anesthetic in the brain
Partial pressure in the brain is dependent on
partial pressure of the anesthetic in blood and
alveoli
Halogenated Organic Compounds Adverse Effects to the Cardiovascular system?
Decreases blood pressure and may decrease renal blood flow
Effects on HR variable
Depress cardiovascular function
One of perfusionists’ most effective tools for changing blood pressure/arterial pressure is what?
their anesthetic vaporizer.
Volatile Anesthetics & Arterial Pressure
•Increasing the level (percentage) of volatile anesthetic provides a reliable, dose-dependent vasodilatory response HOW IS THIS CAUSED???
This is caused by a combination of direct vaso-dilatory effect and sympatholytic effect
Volatile Anesthetics Potential Disadvantages?
–Very significant hemodynamic variability from patient to patient.
–Possibility of “coronary steal syndrome”
coronary steal syndrome
Disadvantage of volatile anesthetics
phenomenon where an alteration of circulation patterns lead to a reduction in the blood directed to the coronary circulation.[1] It is caused when there is narrowing of the coronary arteries and a coronary vasodilator[2] is used - “stealing” blood away from those parts of the heart. This happens as a result of the narrowed coronary arteries being always maximally dilated to compensate for the decreased upstream blood supply. Thus, dilating the resistance vessels in the coronary circulation causes blood to be shunted away from the coronary vessels supplying the ischemic zones, creating more ischemia.
Arteriolar dilation of normal vessels diverts blood away from stenotic areas
–Commonly associated with adenosine, dipyridamole, and SNP
–Forane causes steal and new ST-T segment depression
–May not be important since Forane reduces SVR, depresses the myocardium yet maintains CO
Vapor Pressure - is what? and is determined by what?
“The tendency of an inhalation anesthetic to
vaporize to its gaseous state”
Determines how readily an inhalation
anesthetic will evaporate in the anesthetic
machine vaporizer
Temperature and anesthetic agent
dependent
Nonvolatile agents
- vapor pressure?
- example?
- delivered how?
-Low vapor pressure
–Methoxyflurane
–Delivered from a nonprecision vaporizer
***NO LONGER USED (but now you understand why they are referred to as “precision vaporizers”
Blood:Gas Partition Coefficient
is what?
The measure of the solubility of an inhalation anesthetic in blood as compared to alveolar/oxygenator gas Indication of the speed of induction and recovery for an inhalation anesthetic agent
Low blood:gas partition coefficient
- solubility?
- recovery?
Agent is relatively less soluble in blood
than alveolar/oxygenator gas
–Faster expected induction and recovery
High blood:gas partition coefficient
solubility?
recovery?
–Agent is more soluble in blood than in alveolar/oxygenator gas at equilibrium
–Agent is less soluble in alveolar/oxygenator
gas
-Agent is absorbed into blood and tissues
(sponge effect)
-Slower expected induction and recovery
Blood: gas partition coefficient determines what?
the clinical use of the anesthetic agent
Maintenance: How fast will the anesthetic
depth change in response to changes in
the vaporizer setting?
Recovery: How long will the patient sleep
after anesthesia?
Minimum Alveolar Concentration (MAC) - what is it?
The measure of the potency of a drug
–Used to determine the average setting on the
vaporizer that will produce surgical anesthesia
“The concentration of anesthetic vapor in alveoli that is required to prevent a motor
response in 50% of patients subjected to
surgical pain stimuli”
*it isn’t really a minimum concentration, it’s really an average concentration
The lower the MAC, the more potent the what?
the anesthetic agent and the lower the vaporizer setting (does this make sense?)
–MAC may be altered by age, metabolic
activity, body temperature, disease, pregnancy, obesity, and other agents present
A vaporizer setting of roughly _____ of an agent is required for surgical anesthesia and completely depends on the individual critter!
1-2 X the MAC
KNOW
Halothane
The archetypical halogenated volatile anesthetic (NO LONGER Used in US)
•Relatively rapid induction & recovery.
•Not explosive like some of its predecessors
Most commonly used inhalant agent in
North America?
Isoflurane
Isoflurane
Vapor pressure? Bld:gas partition coefficient? Good for? MAC? rubber solubility?
-High vapor pressure: need a precision
vaporizer
–Low blood:gas partition coefficient: rapid induction and recovery
–Good for induction with mask or chamber
–MAC = 1.3% to 1.63%: helps determine initial vaporizer setting
–Low rubber solubility
Isoflurane storage?
–Stable at room temperature; no preservatives needed
Isoflurane CV effects?
Respiratory effects?
Cerebral BF effects?
Maintains cardiac output, heart rate, and rhythm–Fewest adverse cardiovascular effects
•Depresses the respiratory system
•Maintains cerebral blood flow
Sevoflurane
Vapor pressure?
Bld:gas partition coefficient?
Good for?
MAC?
- High vapor pressure: needs a precision vaporizer
- Blood:gas partition coefficient: rapid induction and recovery
- Good for induction with a mask or chamber
- High controllability of depth of anesthesia
- MAC = 2.34% to 2.58%
Sevoflurane CV effects?
Respiratory effects?
Elimination?
Cerebral BF effects?
-Minimal cardiovascular depression
•Depresses respiratory system
•Eliminated by the lungs, minimal hepatic metabolism
•Maintains cerebral blood flow
Desflurane
- Cost?
- Bld:gas partition coefficient?
- administration with ?
- MAC?
•Expensive •Lowest blood:gas partition coefficient: very rapid induction and recovery •Used with a special precision vaporizer •MAC = 7.2% and 9.8% –Least potent inhalant agent
Called one breath anesthesia - bc in one breath you are asleep or awake
Nitrous Oxide
- an excellent what?
- administration doesn’t require what?
- administered with what?
- MAX amount?
•Excellent analgesic, poor anesthetic (by
itself )
•Doesn’t require a precision vaporizer
•Often mixed with other gas anesthetics to
produce better analgesia (NEVER more than 80% N₂O!)
Nitrous Oxide - max admin amount?
NEVER more than 80% N₂O
Nitrous Oxide storage?
Unlike other gas anesthetics, nitrous oxide is a compressed liquid, therefore you have no idea how much is really in the tank you just have to lift it up and guesstamate
Most soluble in Blood highest to lowest
Bld:gas partition coefficient
- Halothane - 2.4
- Isoflurane - 1.4
- Sevoflurane - .65
- N.O - .47
- Desflurane - .42
inhalation anesthetic - Good for patients with asthma
Sevoflurane - bronchial smooth muscle dilation - not irritating, good for kids too
Inhalation anesthetic – has potential renal toxicity at low flows?
sevoflurane
inhalation anesthetic - must be delivered with a special vaporizer>
Desflurane
inhalation anesthetic - does not raise intracranial pressure?
isoflurane
Induction - highest alveolar concentration in quickest time to lowest?
Highest - N.O. Desflurane Sevoflurane Isoflurane Lowest - Halothan
Recovery - Lowest concentration in the quickest amount of time ?(fastest to recover)
N.O. Desflurane Sevoflurane Isoflurane Halothane
Important Properties to consider – of Inhalant Anesthetics (5)
- Vapor Pressure
- Partition coefficient
- Min alveolar concentration (MAC) - potency
- Rubber solubility (important in other countries)
- CO dependent
Intravenous Anesthetics - lowers intracranial pressure and not likely to cause nausea?
- poor analgesia
Propofol
Intravenous Anesthetics - No respiratory depression
- blunts undesirable CV reflexes?
Dexmedetomidine
Intravenous Anesthetics - causes significant nausea, laryngospasm, poor analgesia
Thiopental
potent anesthetic, rapid onset
