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Inhaled Anesthetics Review > Nitrous Oxide > Flashcards

Flashcards in Nitrous Oxide Deck (20)
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1

N2O boiling point

-88.5 C

2

N2O saturated vapor pressure

38,628 mmHg

3

N2O MAC

105 vol%

4

N2O blood/gas coefficient

0.47

5

N2O brain/blood coefficient

1.1

6

N2O muscle/blood coefficient

1.2

7

N2O fat/blood coefficient

2.3

8

N2O Respiratory effects

Least decrease in tidal volume & increase in end tidal CO2 out of gases (Minimal compared to potent agents)
Reduces ventilatory response to hypoxia & hypercapnia
Additive respiratory depressant with other agents

9

N2O CV effects

Direct negative inotrope
No substantial effect on LV diastolic function
Slight decrease in CO
Modest increase in pulmonary & systemic arterial pressure (increase arterial vasomotor tone) via a sympathomimetic effect - counteracts hypotensive effects of all other agents
Increases circulating norepi levels

10

N2O Obstetrical effects

decreases activity of methionine synthetase & thymidylate synthetase - important for RNA/DNA replication - has been linked with miscarriages if N2O inappropriately scavenged

11

N2O Discovery

1760s

12

How does N2O effect MAC of other anesthetics

Each 1 vol% added to inspired gases, 1 vol% less potent inhalation agent may be administered

13

N2O concentration effect

Leaves less space in FRC for fresh gas inflow to occur- as fresh gas saturated with anesthetic flows in the concentration of anesthesia in FRC increases faster

14

N2O second gas effect

*Not a big deal with sevo/des*. Potent inhalation agent rises to higher concentration more quickly because of concentration effect.

15

N2O Diffusion Hypoxia

N2O washes out fast due to coefficients, as N2O rushes into lungs to leave, it drags other gases with it & displaces O2 which can results in diffusion hypoxia. (just turn on oxygen, should be fine)

16

N2O CNS effects

Inconsistent data - believed to increase CBP so increase ICP & CMRO2. May be attenuated by hypocapnia
Decreases seizure activity

17

N2O renal effects

Decreases renal blood flow, GFR & urinary output

18

N2O Complications

Contraindicated in patients with tympanic membrane/ear surgeries (*tympanoplasties), pneumothoraces (will double in size in 10 minutes, triple in 30 minutes), small bowel obstructions, pneumocephalus, air emboli (increase in pressure in spaces that cannot increase in size, increase in volume in spaces that can increase in size)

19

NIOSH standards of N2O in ambient OR air

<25 ppm

20

N2O liver:blood coefficient

0.8