Ex2IA2 Flashcards by Rachel Unknown

Characteristics of Isoflurane

Halogenated methyl ethyl ether
Clear, nonflammable at room temp
Pungent, ethereal odor
Intermediate solubility, high potency

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Isoflurane has a ______ onset and recovery from anesthesia

Rapid

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T/F isoflurane contains thymol

False

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Intermediates of isoflurane

Acyl halide - hepatic necrosis

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Sevoflurane characteristics

Fully fluorinated - methyl isopropyl ether
Nonpungent, minimal odor
Least degree of airway irritation

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Preferred agent for inhalation induction

Sevoflurane

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Sevoflurane has a _____ induction/emergence

Rapid

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Sevoflurane metabolism

3-5% undergoes biodegradation

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Sevoflurane metabolites

Inorganic fluoride (nephrotoxic)
Hexafluoroisopropanol (ulcerations to mucus membrane/skin)
No acyl halide metabolites (liver toxicity)

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Least likely to form CO on exposure to CO2 absorbants

Sevo

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Formed in presence of CO2 absorbents (Sevo)

Compound A (renal proximal tubular injury)

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Which agent has flow rate requirements?

Sevo

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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

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Risk of low flows

High temperature of absorbant assoc. with canister explosions (esp 100% O2/N20 on ped pts Monday morning)

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Fluorination results in

Increased vapor pressure
Enhances molecular stability
Decreases potency

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Which agents are fully fluorinated?

Sevo, Des

Only 2 Hydrogens

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Desflurane characteristics

Fluorinated methyl ethyl ether

Very pungent/irritating to lungs

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Which agent is not preferred for inhalation induction

Desflurane

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How does desflurane differ from iso

Substitution of F for Cl

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Agent that produces most CO

Desflurane

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Des metabolism

Minimal serum/urinary trifluoroacetate concentrations

Hepatic necrosis rare but possible

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Desflurane potency

1/5 of Iso

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Unique aspect of desflurane

High vapor pressure (boil at room temp)

Requires special vaporizer to regulate concentration

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Sudden initiation of high concentrations of ______ may cause _______

Des
Tachycardia/coughing
**fentanyl 1.5-3mcg/kg can attenuate

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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