Isoflurane

Question 1

When and by whom was Iso synthesized?

Answer 1

1965, Ross Terrell and Louise Speers Ohio Medical

Question 2

When was Iso approved and most widely used in US?

Answer 2

1981, on hold for causing cancer in mice but not true.

Question 3

What 6 things are general requirements for patient use of gases?

Answer 3

Volatility (evaporate at normal temp, = 4 carbon atoms); Nonflammability (limited H atoms, substituted with Cl or F aka halogenation); Low boiling point, Stable in soda lime, Easy to manufacture at lower cost (Cl atom makes it more cost effective); low biodegradation/metabolism.

Question 4

Isoflurane is a structural isomer of which other gas?

Answer 4

Enflurane

Question 5

What is the long name of Isoflurane

Answer 5

1-chloro-2,2,2-trifluoroethyl, difluoromethyl ehter

Question 6

What is the molecular weight of isoflurane?

Answer 6

184.5g

Question 7

What are the characteristics of isoflurane?

Answer 7

clear, colorless, stable liquid, no additives or stabilizers, pungent odor (resp irritant)

Question 8

Isoflurane is similar in chemical structure to which other gas?

Answer 8

Desflurane, only difference in des is F atom for Cl atom. Des is chemically more stable (0.02%) vs Iso (0.2%) but not clinically significant.

Question 9

True/False: Isoflurane is not altered by CO2 absorbents, light, or moisture.

Answer 9

True, also non-reactive with metal and stored in amber bottles.

Question 10

Where is isoflurane metabolized/biotransformed and a high or low level of metabolism?

Answer 10

Eliminated mostly unchanged through the lungs, very low metabolism <0.2%, oxidative metabolism by cytochrome P450 in liver, increases trifluoroacetic acid (small rise in serum F levels)

Question 11

What is the B:G solubility coefficient of Isoflurane? Is that high or low?

Answer 11

1.46, high. 1.46x higher in blood to every 1 molecule in alveoli. prefers to be in blood state.

Question 12

What does oil:gas partition coefficient reflect? What is isoflurane’s? Is that high or low?

Answer 12

measure of potency; 91; HIGH.

Question 13

What is the MAC of Isoflurane? high or low potency?

Answer 13

MAC 1.2; high

Question 14

Is induction fast or slow with isoflurane?

Answer 14

slow, high b:g; usual onset 5-7 min

Question 15

Is emergence fast or slow with isoflurane?

Answer 15

slow if prolonged exposure as it is highly soluble in fat, muscle, and the brain.

Question 16

Does high cardiac output affect isoflurane induction?

Answer 16

Yes, highly soluble in blood so it slows the concentration in the lungs and alveolar partial pressure leading to lower concentration in brain.

Question 17

What cardiac effects does Isoflurane have?

Answer 17

CO maintained, HR increase 10-30bpm, slight SV reduction, decreased SVR, dysrhythmias can occur if rapid increases in MAC, coronary steal: dilates coronary arteries, theoretically diverts blood from stenotic arteries.

Question 18

What respiratory effects does isoflurane have?

Answer 18

bronchospasm/irritation to upper resp mucosa, bronchodilation of bronchial smooth muscle, most respiratory depressant of all volatiles–related to anesthetic depth(decreased Tv, RR increase), blunts normal response to hypoxia and hypercapnia (central and peripheral chemoreceptors)

Question 19

What cerebral effects does isoflurane have?

Answer 19

reduces CMRO2 requirements, decreased CVR >1 MAC, increased CBF and ICP but can be reversed with hyperventiation, suppresses seizure activity, 2 MAC=electrical silent EEG.

Question 20

What are the neuromuscular effects of isoflurane?

Answer 20

muscle relaxant effect progresses with depth, potentiates non-depolarizing relaxants, uninhibited spinal cord reflexes–shivering.

Question 21

What are the renal effects of isoflurane?

Answer 21

decreased renal blood flow, GFR, and UOP

Question 22

What are the hepatic effects of isoflurane?

Answer 22

reduced total hepatic blood flow, maintains hepatic oxygen supply, minimally affects liver function test, low metabolism toxicity effects.

Question 23

What are the GI effects of isoflurane?

Answer 23

PONV, more with long cases, PO ileus.

Question 24

Can you do inhalation induction with isoflurane?

Answer 24

NO, pungent

Question 25

What are the other uses of isoflurane?

Answer 25

ECMO for sedation, Neuro and Peds for breaking seizures.

Question 26

Are there many drug interactions with isoflurane? Which ones?

Answer 26

229!, severe interactions with droperidol (long QT), NE and epi (arrhythmias), and MAOIs (labile BP)

Question 27

What is the other name for isoflurane?

Answer 27

Forane