Inhalational Agents: Individual Agents Flashcards
halothane was introduced into practice in
1956
halothane odor
sweet, nonpungent
halothane is stable in __ but decomposes __
soda lime
rubber products and most metals
halothane requires storage in
dark bottles and preservative to prevent spontaneous oxidative decomposition
halothane perservative it is stored in
thymol
halothane breaks down to
- hydrochloic acid
- hydrobromic acid
- chloride
- bromide
- phosgene
halothane causes ___ myocardial depression
dose-dependent
halothane dose-dependent myocardial depression causes
decreased cardiac output and decreased blood pressure
2 MAC of halothane causes __ reduction in BP, CO
50%
halothane slows conduction of the heart through the
AV node to cause junctional rhythms, wandering pacemaker, and bradycardia
halothane inhibits (cardiac related)
baroreceptor reflex
halothane myocadial depression comes from
the interference with Na-Ca exchange and intracellular calcium utilization
halothane myocardial depression is accentuated with
b-blocking agent, propanolol, and CCB
combining halothane with aminophylline results in
serious ventricular arrhythmias
halothane sensitizes the myocardium to
catecholamines
halothane adults max dose of epi
1.5 mcg/kg subq
halothane lidocaine 0.5% added essentially
doubles dose of epi allowed
halothane children max dose of epi
7.8-10 mcg/kg with and without lido
__ enhances sensitization of catecholamines from halothane
hypercarbia
halothane sensitization of catecholamines is thought to be due to
effect on the transmission rate of cardiac impulses through the conduction system
halothane is an excellent broncho___
dilator- reverses asthma-induced bronchospasm
halothane respiratory effects work by
inhibiting intracellular calcium mobilization- bronchial smooth muscle
halothane is used for __ induction
inhalation
halothane causes direct cerebral ___ and decreases __
vasodilation
CMRO2
with halothane __ is attenuated so you must __ prior to initiation of halothane
cerebral autoregulation
hyperventilate
at 1.1 MAC and MAP of 80, halothane increases CBF by
190% (more than iso)
halothane is the most potent trigger for
MH
halothane metabolism
15-40%
halothane hepatitis mechanism
not clear but likely an antibody that binds to hepatocytes previously exposed to halothane has been isolated from 70% patients with halothane-induced hepatic dysfunction
the antibody response from halothane may involve
liver microsomal proteins that have been modified by trifluoroacetic acid as the triggering antigens
incidence of halothane hepatitis
1 in 35,000 fatal, hepatic necrosis (1 in 10,000 jaundice)
incidence of halothane hepatitis is higher if
halotahne exposure repeats within 28 days
risk factors for halothane hepatitis
- sepsis
- obesity
- age > 40 years
- female
- enhanced metabolism/induced enzymes
halothane hepatitis has rarely been reported in
prepubescent children, even with preexisting liver disease
hepatitis similar to halothane hepatitis can be induced by
other volatile agents but rarely (**potential trick question, can happen with all the other agents but not sevo)
halothane effect on hematology
may cause a decrease in platelet aggregation and increased bleeding time (like sevo)
halothane effect on immune system
depresses the defense against infection, the oxidative burst response of neutrophils (unlike the other three potent agents)
isoflurane was introduced into clinical practice in
1981
isoflurane odor
pungent, ether-type
isoflurane is an isomer of
enflurane
isoflurane flammability
stable, nonflammable
isoflurane preservative
not necessary
isoflurane __ myocardial depression
minimal
isoflurane ___ oxygen demand more in heart than other organs
decreased
with isoflurane, CO is preserved by
increased HR related to baroreflexes
isoflurane __ decreases (cardiac related)
stroke volume (CO remains nearly constant due to compensation)
rapid increase in isoflurane concentration causes
increases in HR, BP, and norepinephrine
isoflurane is different from other agents due to __ properties (cardiac related)
mild beta-adrenergic agonist test question
can prevent HR increases at lower concentration of isoflurane with
small dose of opioid, MSO4 or fentanyl, and anxiolytic
increased HR with isoflurane is not seen in
neonates with decreased BP or elderly; more likely seen in healthy younger patients
CO is not affected by __ MAC of isoflurane
1-1.8
RA pressure can __ with isoflurane but is unchanged by __ MAC
increase
0.9-1.4
heart remains efficient even up to __ MAC isoflurane
1.4-1.9
mild beta stimulation from beta 1 with isoflurane causes
maintenance of CO, increased HR
mild beta stimulation from beta 2 with isoflurane causes
vasodilation, decreased SVR and lower BP
isoflurane causes __ coronary vascular resistance with ___ increased or unchanged
decreased
coronary blood flow
isoflurane dilates
small endocardial coronary arteries within the heart muscle (unlike nitroglycerin)
isoflurane causes ___ steal according to some studies
coronary artery (blood flow goes to areas that already have good blood flow versus the ischemic areas)
cardioprotection from isoflurane
0.25 MAC
coronary artery steal with isoflurane is only when MAP was allowed
to go below 60
with isoflurane BP is decreased based on
dose which is mainly due to SVR reduction
__ patients may not tolerate BP decrease seen with isoflurane
hypovolemic
with isoflurane, carotid sinus baroreceptor reflex is maintained at __ MAC but depressed at __ MAC
1
2
isoflurane increases the refractoriness of
accessory pathways and the AV conduction system
isoflurane’s effect on the accessory pathway conduction interferes with
interpretation of confirming success of ablation procedures (suppression of SVT re-entry tachycardia)
isoflurane effect on ablations
- prolong action-potential duration, delay atrial and vent repolarization, decrease tachyarrhythmia inducibility
- enhance automaticity of secondary atrial pacemakers causing ectopic atrial rhythms
isoflurane cause __ prolongation in healthy patients
QT; may not be seen in patients with idiopathic long QTc
isoflurane causes __ respiratory depression than halothane
greater
with isoflurane, tachypnea is less pronounced resulting in
enhanced reduction in minute ventilation
isoflurane is __ and __ to airways but a good broncho__
pungent and irritating
dilator
concentration greater than 1 MAC, isoflurane increases __ and __ pressure
CBF and intracranial
__ that accompanies the introduction of isoflurane can minimize the effect on ICP
hyperventilation
when isoflurane is used for deliberate hypotension, it decreases
cerebral oxygen demand
at 2 MAC, isoflurane results in
an isoelectric EEG; this provides brain protection during episodes of cerebral ischemia
isoflurane hepatic oxygenation is better maintained because
hepatic artery perfusion and hepatic venous oxygen saturation are preserved
isoflurane is metabolized to
- flouride ions
- trifluoroacetic acid
- formic acid
no real concerns for inorganic fluoride levels
isoflurane metabolism
0-0.2%
desflurane was introduced to practice in
1992
desflurane differs from isoflurane only in
the substiution of a fluorine atom for a chlorine atom on the alpha ethyl carbon
desflurane __ boiling point, __ vapor pressure requiring __
low
high
temperature-controlled vaporizer
desflurane is stable in
moist absorbent