Ex2IA2 Flashcards
Characteristics of Isoflurane
Halogenated methyl ethyl ether
Clear, nonflammable at room temp
Pungent, ethereal odor
Intermediate solubility, high potency
Isoflurane has a ______ onset and recovery from anesthesia
Rapid
T/F isoflurane contains thymol
False
Intermediates of isoflurane
Acyl halide - hepatic necrosis
Sevoflurane characteristics
Fully fluorinated - methyl isopropyl ether
Nonpungent, minimal odor
Least degree of airway irritation
Preferred agent for inhalation induction
Sevoflurane
Sevoflurane has a _____ induction/emergence
Rapid
Sevoflurane metabolism
3-5% undergoes biodegradation
Sevoflurane metabolites
Inorganic fluoride (nephrotoxic)
Hexafluoroisopropanol (ulcerations to mucus membrane/skin)
No acyl halide metabolites (liver toxicity)
Least likely to form CO on exposure to CO2 absorbants
Sevo
Formed in presence of CO2 absorbents (Sevo)
Compound A (renal proximal tubular injury)
Which agent has flow rate requirements?
Sevo
Flow rate requirements for Sevo
During 1st 2 MAC hours: flow must equal or > 1L/min
After 2 MAC hours: flows must be 2L/min
Risk of low flows
High temperature of absorbant assoc. with canister explosions (esp 100% O2/N20 on ped pts Monday morning)
Fluorination results in
Increased vapor pressure
Enhances molecular stability
Decreases potency
Which agents are fully fluorinated?
Sevo, Des
Only 2 Hydrogens
Desflurane characteristics
Fluorinated methyl ethyl ether
Very pungent/irritating to lungs
Which agent is not preferred for inhalation induction
Desflurane
How does desflurane differ from iso
Substitution of F for Cl
Agent that produces most CO
Desflurane
Des metabolism
Minimal serum/urinary trifluoroacetate concentrations
Hepatic necrosis rare but possible
Desflurane potency
1/5 of Iso
Unique aspect of desflurane
High vapor pressure (boil at room temp)
Requires special vaporizer to regulate concentration
Sudden initiation of high concentrations of ______ may cause _______
Des
Tachycardia/coughing
**fentanyl 1.5-3mcg/kg can attenuate
What permits rapid onset/prompt awakening in ______
Solubility/potency
Desflurane
How is Nitrous administered during general anesthesia
Admin in combo with opioids/VAs
Characteristics of N2O
LMW, inorganic
Sweet smelling/odorless
Non-flammable, low potency, poorly soluble; supports combustion
N2O metabolism
Minimal - via gut reductive processes
Which IA produces analgesia
N2O
AEs of N2O
Skeletal muscle rigidity
PONV
Expansion of gas filled spaces
Inactivation of VitB12
PTX volume can double in _____ with _____% N2O
10 minutes
75%
Magnitude of volume expansion from N2O is influenced by
Partial pressure of N2O
Blood flow to gas filled spaces
Duration of administration
Which operations should you avoid N2O in?
Bowel obstruction
Tympanic rupture
Intraocular (retinal artery/vision loss)
Effect on CNS - CBF, CMRO2
Increased CBF (VAs > N2O)
Decreased CMRO2
N2O increases CMRO2
How is increased ICP offset?
Hyperventilation paCO2 < 30 torr
Desflurane 0.5 MAC results in _____ ICP
No effect on ICP until >1.1 MAC
EEG at < 0.4 MAC
Increases in voltage/frequency produced
EEG 0.4 MAC
Amnesia occurs
CMRO2 begins to decrease
EEG 1 MAC
Decreased frequency
Max voltage achieved
ISO produces _____ at ____ MAC and _____ at 2 MAC
Burst suppression at 1.5 MAC
Isoelectric EEG at 2 MAC
Which IA has anticonvulsant properties?
ISO
N2O < 0.75 MAC can produce
Clonus/opisthotonus
N2O effect on evoked potentials
Decreases amplitude
What may effect anesthetic requirement
Surgical stimulation may increase requirement
Effect of IAs on CVS: direct myocardial \_\_\_\_\_\_ \_\_\_\_\_\_\_ of sympathetic outflow Peripheral autonomic ganglion \_\_\_\_\_\_\_ \_\_\_\_\_\_ Carotid sinus reflex activity \_\_\_\_\_\_\_ cAMP \_\_\_\_\_\_\_\_ catecholamine release \_\_\_\_\_\_\_\_ calcium influx via slow channels
direct myocardial ___depression___
____inhibition___ of sympathetic outflow
Peripheral autonomic ganglion ___blockade____
___attenuated___ Carotid sinus reflex activity
____decreased___ cAMP
___ decreased_____ catecholamine release
____ decreased____ calcium influx via slow channels
Effect of IAs on CSF
Iso improves rate of absorption
Nitrous effect on CVS
Mild sympathomimetic stimulation - masks the cardiac depressant effects
- mydriasis
- increased body temp
- increased catecholamine release
- increased RAP
- diaphoresis
- vasoconstriction
How would IAs effect patients with HTN/anxiety?
Larger decrease in MAP
IA effect on MAP
Dose-dependent decrease
Offset during surgical stimulation
How do IAs effect MAP?
Primarily via reductions in SVR
N2O effect on MAP
Increase or no effect
IAs effect on HR
ISO/Sevo/Des increase HR
- elderly less likely
- Sevo at >1.5MAC
IA effect on HR
Des produces significant increases in HR if concentration increased suddenly
*attenuated by prior small dose of opioid
N2O depresses carotid sinus - may dampen HR response to hypotension
IA effect on CO
N/A only Sevo @ 1.5-2 MAC decreases
VA effect on SV
Decrease by 15-30%
Effect of N2O on CO
Modestly increased CO
- d/t sympathomimetic effect
- cardiac depression offset by sympathomimetic effect
IA effect on RAP
Increase
(Sevo does NOT)
N2O - d/t increased PVR (don’t use in pHTN)
IAs effect on SVR
Decrease
N2O does not change - may produce constriction of cutaneous vessels (increased body temp)
Iso - Beta agonist; heat loss
IAs effect on PulmVR
Little or no effect
N2O - increases (R—>L shunting may jeopardize oxygenation in pts with congenital heart defects)
Effect on HPV
Inhibited at greater than 1 MAC
Effect on dysrhthmias
Iso slows SA discharge - prolongs ventricular conduction times
Effect on rhythm
Prolong QTc
Which IA is acceptable for ablative procedures?
Sevo
Which IA should not be used in ablative studies?
Iso - increases the refractory period of accessory pathways/slows AV conduction
Effect on Coronary blood flow
All produce coronary dilation
*Iso preferentially dilates small resistance vessels more than larger conductance vessels
Anesthetic preconditioning
Brief exposure to VAs confers cardioprotection
Brief periods of myocardial ischemia prior to a longer period of ischemia provides protection
Abrupt increases in Iso/Des can result in?
Increase sympathetic/RAA activity
Cause transient increase in SBP/HR/coughing
**doses from 0.55-1.66 MAC
*des>iso
Factors that effect transfer of IA from arterial blood to brain
Brain-blood partition coefficient
CBF
A-vD difference
