Inhalation Anesthetics M&M Flashcards
which gas dilates Coronary arteries
Isoflurane
what determines the FA/Fi ratio.
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.
What happens to the FA/Fi ratio as cardiac output increases.
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.
What 3 factors influence Alveolar gas pressure
1) Uptake
2) ventilation (does not effect low soluble gas)
3) concentration
What factors influence uptake portion of alveolar gas
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).
What is second gas effect?
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.
What is concentration effect?
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)
What can happen with patient is recovering from Nitrous Oxide inhalation
Large quantity of NO go from blood –> alveoli and dilute O2 and CO2
DIFFUSION HYPOXIA
What happens to MAC in hyper and hypo natremia
Hypernatremia = Increased MAC Hyponatremia = Decreased MAC
Has to do with alterations in the CSF.
Which Gas does not trigger MH, and what are some other advantages.
Xenon (NMDA receptor)
- Low blood solubility.
- mac 70%
- minimal effect on CV
- fast on and fast off.
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
1 brainscape picture
What is complication of prolonged Nitrous Oxide exposure?
Bone marrow suppression (megaloblastic anemia)
- it is also teratogenic in pregnancy.
Effect of Halothane on Coronary arteries
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.
Which gas causes Bronchodilation
1) Halothane: not through beta receptors. Works on calcium channels directly in the lungs.
2) Isoflurane (not as good as halothane)
3) Sevoflurane
Which gas has a metabolite that can causes problems.
Halothane –> trifluoroacetic acid
- post anesthetic changes in mentation.
- also can be the trigger for autoimmune hepatitis.
