Inhalation 2 Flashcards
Mechanism of action : Meyer-Overton Theory (Critical Volume Hypothesis
States that there is a correlation between lipid
solubility on inhaled anesthetics and MAC
Meyer-Overton Theory (Critical Volume
Hypothesis ANESTHESIA occur when
Anesthesia occurs when a sufficient number of
molecules dissolve in lipid cell membranes which changes the shape of the membrane
Meyer-Overton Theory: Expansion of cell membranes by dissolved
anesthetic could distort channels necessary for ion
flux, and a subsequent effect on the development
of action potentials necessary for synaptic
transmission to occur.
Mechanism of action (Protein
Receptor Hypothesis)
Evidence for protein receptors in the central nervous system as a site and mechanism of action of inhaled anesthetics is suggested by the steep dose response curve (MAC) of inhaled anesthetics (crucial degree of
receptor occupancy)
Another theory About GABA
Volatile anesthetics and injected anesthetics may activate GABAA channels (preventing the release of neurotransmitters) and inhibit glutamate channels.
Volatile anesthetics are
Halogenated methyl ethyl ETHER derivaties.
Volatile anesthetics that is not an ETHER? what is it?
Halothane, halogenated alkane derivative
In which gas is fluorine the only halogen present
Desflurane
Blood solubility of Desflurane , and VP and metabolism
low, high vapor pressure ; low metabolism
What contributes to the RAPID onset of PA and recovery from NO, Des and Sevo
LOW BLOOD/GAS solubility
EEG, as the dose of anesthetic approaches ___MAC, the frequency on the EEG_______
1 ; Decreases
Administration of concentrations of ______MAC produce dose depended increases in
0.6; CBF
CBF effects of Volatile from HIGHEST to LOWEST
HEIDS
Halothane–> ENFLURANE–> ISOFLURANE –> DESFLURANE–> SEVO
Does NO increase CBF?
Yes
Do inhaled anesthetics alter the RESPONSIVENESS of the CEREBRAL CIRCULATION to changes in PaO2?
No
The greater decrease in CMRO2 requirements in produced by
ISOFLURANE
Inhaled that alters the GLOBAL CEREBRAL OXYGEN supply-demand balance
ISOFLURANE
May have cerebral protecting EFFECT
ISOFLURANE
Inhaled anesthetics and ICP
increases ICP parallels the CBF
What patients are most vulnerable in increase in ICP?
Patients with space-occupying intracranial lesions.
CSF production is increased by which inhaled anesthetic?
ENFLURANE
Conscious memory is suppressed by
Volatile anesthetics
Conscious memory suppressed by _____MAC Isoflurane
0.45
Conscious memory suppressed by _____MAC NO
0.60
Conscious memory concentrations are similar to
MAC awake
NitrousO effect on BP
No effect or A MODEST INCREASE in BP
Volatile anesthetics and BP
Produce dose dependent and similar DECREASES in BLOOD PRESSURE
The decrease in BP of Halothane and enflurane is PRINCIPALLY due to
Decreases in myocardial contractility
The decrease in BP of DIS (Des, ISO, SEVO) is PRINCIPALLY due to
Decreases in SVR
Agent associated with junctional rhythm
Halothane
Agent associated with Suppression of sinus node activity
Halothane
HR does not change despite decrease in BP with those 2 agents
Halothane and Sevoflurane
Because HR does not change despite decrease in BP with halothane and sevo what does it indicate
Depression of carotid sinus reflex response by the volatile anesthetic
Depression of carotid sinus reflex 2 agents
Sevo and halothane
HR change OCCUR and tend to INCREASE with the decrease in BP with those 2 agents
Isoflurane and Desflurane
Preservation of carotid sinus reflex response by the volatile anesthetics (2)
Isoflurane and Desflurane.
Increase in HR of iso and des are ______. Occur at low dose for _____and at high doses for ______
dose-dependent; Iso; Des
2 agents produces dose dependent decrease in CO
Halothane , enflurane
Not associated with decreases in CO ,despite decrease in BP
SID (sevoflurane, Isoflurane, and Desflurane)
Modestly increase CO
Nitrous
Agent with mild sympathomimetic effect
Nitrous
Possible explanation of why SID doesn’t affect myocardial contractility?
Those agents are more potent
Readily depress brain, spare the heart
Inhaled anesthetics on RAP
Dose-dependent INCREASE
RAP increase with N2O most likely reflects increase
PVR
Which agents produce does dependent decreases in SVR
SID (Sevoflurane, Isoflurane, Desflurane)
What can offset the magnitude of the decrease in SVR
Substitution of Nitrous with part of the case.
Volatiles on PVR
Little or no predictable effect
PVR: Nitrous oxide may produce ? what patients are at higher risk?
increases in PVR ; Patients with HTN
Volatile anesthetics and EPI
Decrease the dose of epi necessary to cause Ventricular cardiac dysrhythmias. Greatest with ALKANE (halothane) least with DIES (ether)
Which is the MORE POTENT CORONARY ARTERY VASODILATOR?
Isoflurane
What can ISOFLURANE-induced Coronary artery vasodilation cause______/ what is the phenomenon known as ?
redistribution of coronary blood flow from diseased areas of myocardium to AREAS with normally responsive coronary arteries. Known as CORONARY STEAL SYNDROME
Why is spontaneous breathing better with inhaled anesthetics?
because of the impact of accumulation of CO2 and better venous return with spontaneous breathing
What are the preexisting disease and drug therapy affecting the circulatory effects of inhaled anesthetics
Diseased cardiac muscle
Aortic stenosis
Prior drug therapy
Mechanism of circulatory effects from inhaled anesthetics?
Myocardial and sympathetic outflow
Myocardial depression
Inhibition of CNS sympathetic outflow