Inhalation Anesthetics M&M

Question 1

which gas dilates Coronary arteries

Answer 1

Isoflurane

Question 2

what determines the FA/Fi ratio.

Answer 2

Ratio in the Alveoli to Inspired gas. Mainly regulated by amount of uptake in the vasculature. At ratio of 1, the amount of inspired gas would equal partial pressure in the alveoli.

Question 3

What happens to the FA/Fi ratio as cardiac output increases.

Answer 3

As long as there is no shunt (PE), CO directly coorelates to amount of pulmonary blood flow. Increased CO = decreased FA/Fi = slower induction/emergence.

Question 4

What 3 factors influence Alveolar gas pressure

Answer 4

1) Uptake
2) ventilation (does not effect low soluble gas)
3) concentration

Question 5

What factors influence uptake portion of alveolar gas

Answer 5

1) Blood gas cofficient (solubility).
2) Alvoelar blood flow (CO)
3) partial pressure difference between venous and alveolar gas. (Depends on tissue solubility (brain vs. teeth), tissue blood flow, and partial pressure difference between arterial gas and tissue).

Question 6

What is second gas effect?

Answer 6

50% of anesthetic is absorbed in the blood

• Give 10/100 (10%) anesthetic and 90/100 O2. –> 5% of the gas gets absorbed in the blood –> 90/95 O2 (95%).
• The O2 percentage was concentrated by absorption of the inhalation gas.

Question 7

What is concentration effect?

Answer 7

50% of anesthetic absorbed in the blood

• 10% Sevo (10/100) and 90/100 O2 –> 5/95 Sevo –> 5.2%
• 50% Sevo and O2 –> 25/75 = 33% Sevo in A.

Rising the concentration by 5 fold causes a greater 5 fold increase in Sevo in the alveoli. (5% to 33% Sevo)

Question 8

What can happen with patient is recovering from Nitrous Oxide inhalation

Answer 8

Large quantity of NO go from blood –> alveoli and dilute O2 and CO2
DIFFUSION HYPOXIA

Question 9

What happens to MAC in hyper and hypo natremia

Answer 9

Hypernatremia = Increased MAC
Hyponatremia = Decreased MAC

Has to do with alterations in the CSF.

Question 10

Which Gas does not trigger MH, and what are some other advantages.

Answer 10

Xenon (NMDA receptor)

• Low blood solubility.
• mac 70%
• minimal effect on CV
• fast on and fast off.

Question 11

Talk about these gas and effect on CV, RR/TV, CO2, cerebral metabolic activity, NMB, renal and hepatic flow.

• Nitrous Oxide
• Isoflurane
• Sevoflurane
• Desflurane
• Halothane

Answer 11

1 brainscape picture

Question 12

What is complication of prolonged Nitrous Oxide exposure?

Answer 12

Bone marrow suppression (megaloblastic anemia)

- it is also teratogenic in pregnancy.

Question 13

Effect of Halothane on Coronary arteries

Answer 13

It vasodilates CA but overall low perufsion due to massive drop in BP due to myocardial depression and blunted baroreceptors leading to bradycardia.
- Also makes the heart more arrthymogenic to epinephrine, limit its use.

Question 14

Which gas causes Bronchodilation

Answer 14

1) Halothane: not through beta receptors. Works on calcium channels directly in the lungs.
2) Isoflurane (not as good as halothane)
3) Sevoflurane

Question 15

Which gas has a metabolite that can causes problems.

Answer 15

Halothane –> trifluoroacetic acid

• post anesthetic changes in mentation.
• also can be the trigger for autoimmune hepatitis.

Question 16

Which voltaile agents can cause coronary steal syndrome

Answer 16

Isoflurane

NO

Question 17

Which volatile agent can cause surge of catecholamines?

Answer 17

Desflurane when it rises rapidly can cause this, tachycardia and high BP.
- can be blunted to fentanyl

Question 18

Which gasses are effected by CO2 absorptant

Answer 18

Desflurane –> Carbon Monoxide

Sevoflurane –> Compound A

Question 19

which volatile agent causes QT prologation

Answer 19

Sevoflurane

Question 20

Which two gases have the most metabolism?

Answer 20

Halothane and Sevoflurane
- Are broken down by enzyme P-450 into inorganic fluoride which can theoretically cause renal damage but has not been really proven.