The section Daily-MCQ series for EDAIC covers a different topic each day with the intent that candidates can prepare one small topic each day, making steady progress in their exam preparation.
Question: Nitrous oxide (N2O):
- a) has blood: gas partition coefficient of 0.47
- b) is 34 times less soluble than N2
- c) may be associated with postoperative hearing loss
- d) inactivates methionine synthetase after prolonged administration
- e) when inhaled at 66% can double a pneumothorax in 10 minutes
Explanation:
- Nitrous oxide is an NMDA receptor antagonist with a blood Blood: gas partition coefficient of 0.47, and Oil: gas partition coefficient of 1.4
- It is roughly 34 times more soluble than nitrogen. therefore, it will quickly and readily transfer across membranes and enter these closed gas-filled spaces more than 30 times faster than nitrogen will diffuse out of the space, causing distension of these spaces significantly. Intrapleural gas volumes can double within 10 min and triple in 30–45 min. Therefore, pneumothorax, bowel obstruction and pneumopericardium are considered contraindications to N2O.
- Molecular weight: 44
- Boiling point: −88°C (309 K)
- Critical temperature: 36.5°C
- The saturated vapour pressure (SVP) is temperature-sensitive (Gay-Lussac’s law). At standard temperature (0°C) the SVP is 35 bar (3500 kPa) and at room temperature (20°C) it is 52 bar (5200 kPa
- Critical pressure: 72 bar
- Cylinder colour (UK) Blue
- Cylinder phase Liquid/vapour at <36.5°C
- Cylinder pressure at 15°C 44 bar (4400 kPa)
- Pipeline pressure 4 bar (400 kPa)
- Filling ratio 0.75 (UK) 0.67 (tropical). ). The filling ratio in the UK is 0.75 (i.e. the weight of nitrous oxide in a full cylinder is three-quarters the weight of water that would fill the cylinder). This is reduced in tropical climates to 0.67 because of the increased vapour pressures exerted at higher temperatures.
- MAC 105%
- it N2O indirectly inhibits methionine synthase, a key enzyme in the metabolism of homocysteine.
Answers:
- true
- false
- false
- true
- true
Cardiopulmonary bypass Module
-
- The basic CPB circuitry.
- Myocardial injury and preservation during CPB.
- Conduct and complications of CPB.
- The perioperative considerations surrounding the management of a patient undergoing CPB.
Cardiovascular physiology module by targetedaic
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The section Daily-MCQ series for EDAIC. covers a different topic each day with the intent that candidates can prepare one small topic each day, making steady progress in their exam preparation.
