RML MAINS 2025
Pharmacology
Easy
Which gas is commonly known as 'Laughing Gas'?
Appeared in: RML MAINS 2025
Explanation
- Nitrous oxide (N₂O) is widely known as 'laughing gas' because of the feelings of euphoria, relaxation, and dissociation it produces upon inhalation.
- It is commonly used in dentistry and obstetrics as an analgesic and weak anesthetic, often in a 50:50 mixture with oxygen (Entonox).
- Its rapid onset and quick recovery make it suitable for short procedures and managing labor pain.
- In a hospital setting, nitrous oxide is stored in cylinders that are painted French Blue for easy identification, which is a critical safety standard.
Why Other Options Were Wrong
- Option A: Nitric oxide (NO) is a vasodilator, not an anesthetic. It relaxes blood vessels and is used to treat conditions like pulmonary hypertension.
- Option B: Nitrogen pentoxide (N₂O₅) is a reactive solid and a strong oxidizing agent. It is not a gas used for medical purposes and is toxic.
- Option D: Nitrogen dioxide (NO₂) is a toxic, reddish-brown gas and a known air pollutant. It is harmful to the respiratory system and has no medical application as an anesthetic.
Related Visual
Clinical Relevance
- Nursing practice connection: Knowing Identification of the common name and properties of a medical gas helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
- Correctly identifying medical gases is a fundamental patient safety responsibility for nurses. The standardized color-coding of gas cylinders (e.g., blue for nitrous oxide, black with a white shoulder for oxygen) is a critical visual check to prevent potentially fatal errors.
- When administering nitrous oxide, nurses must monitor the patient for side effects like dizziness, nausea, and vomiting. It's also important to ensure adequate ventilation in the room to prevent occupational exposure.
- Chronic recreational use or occupational exposure to nitrous oxide can inactivate vitamin B₁₂, leading to megaloblastic anemia and severe neurological damage (subacute combined degeneration of the spinal cord). Nurses should be aware of these risks in patients with a history of substance misuse.
How to Approach the Question
- This is a factual recall question that tests your knowledge of common names for chemical compounds used in medicine.
- First, identify the key term in the question: 'Laughing Gas'.
- Recall or deduce the chemical name associated with this common term. The name itself hints at a mood-altering effect.
- Evaluate the options provided. 'Nitrous oxide' is the well-established chemical name for laughing gas.
- Differentiate it from other similar-sounding nitrogen compounds. 'Nitric oxide' has a distinct medical use (vasodilation), while 'nitrogen dioxide' and 'nitrogen pentoxide' are toxic and not used for anesthesia.
Concept Tested & Keywords
- Concept Tested: Identification of the common name and properties of a medical gas.
- Stem keywords: gas, Laughing Gas
- Lead-in keywords: Which gas
Question ID
QnQCyYPx7trjj5CZdClYuB
Reference Book
E6 Robert Boland, Marcia L. Verduin - Kaplan and Sadock's Comprehensive Text of Psychiatry-Wolters Kluwer Health (2024) (pp 1-16525 of 16525) p. 4486-4488
E6 Medicine Harrison 22e Part 2 p. 2056-2058
E6 Obstetrics Williams p. 60-81
Practise the full RML MAINS 2025
Attempt every question from this paper in a timed mock, then review the full solution for each one.
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