Nitrous Oxide

Question 1

What is the molecular weight of Nitrous Oxide?

Answer 1

44

Question 2

What is the boiling point of Nitrous Oxide?

Answer 2

-88 degrees C

Question 3

What is the SVP at 20 degrees C of Nitrous Oxide?

Answer 3

5200

Question 4

What is the blood:gas coefficient of nitrous oxide?

Answer 4

0.47

Question 5

What is the oil:gas coefficient of nitrous oxide?

Answer 5

1.4

Question 6

What is the MAC of nitrous oxide?

Answer 6

105

Question 7

What % of nitrous oxide is metabolised?

Answer 7

0.01%

Question 8

What are the metabolites of nitrous oxide?

Answer 8

nitrogen

Question 9

What are the CNS effects of nitrous oxide?

Answer 9

CNS depression and analgesia. It decreases the MAC of other agents when used concomitantly. Increases cerebral blood flow and intracranial pressure.

Question 10

What are the CVS effects of nitrous oxide?

Answer 10

Mild direct myocardial depressant, but also increases sympathetic activity at the same time. Therefore little overall effect

Question 11

What are the RS effects of nitrous oxide?

Answer 11

Slight decrease in tidal volume + increase in resp rate. Over all little change in ventilation

Question 12

What are the pharmacokinetics of nitrous oxide?

Answer 12

Fast onset and offset due to low blood:gas coefficient (0.47). Excreted unchanged through lungs and skin.

Question 13

What are the adverse effects of nitrous oxide?

Answer 13

• 34x more soluble than nitrogen and diffuses rapidly across membranes so can fill air-filled cavities as nitrogen diffuses out slowly
• CI in pneumothorax, middle ear surgery
• PONV ~15%
• bone marrow toxicity (metabolises cobalt atom in Vit B12)
• protracted use leads to neurotoxicity
• diffusion hypoxia - O2 in alveoli diluted by rapid movement of N2O from blood which can cause hypoxia if O2 not administered
• 2nd gas effect - speeds onset of other volatiles because N2O diffuses out of the alveolus faster, therefore the volatile is more concentrated and moves down the concentration gradient faster