Question 21: Which one of the following is the safest gas for creating pneumoperitoneum in operative laparoscopy?
- A. Oxygen
- B. Carbon monoxide
- C. Nitrous oxide
- D. Carbon dioxide (Correct Answer)
Explanation: ***Carbon dioxide***
- **Carbon dioxide (CO2)** is the gold standard for creating **pneumoperitoneum** because it is rapidly absorbed from the **peritoneal cavity** and excreted by the lungs, minimizing the risk of gas embolism.
- Its **high solubility in blood** (20x more soluble than nitrogen) reduces the risk of serious complications if inadvertently injected intravascularly.
- **Non-combustible** and does not support combustion, making it safe to use with electrocautery and other heat sources during surgery.
*Oxygen*
- **Oxygen** is highly **combustible** and would create a significant fire hazard in the presence of electrocautery or other heat sources during surgery.
- It could also cause **gas emboli** if it enters the bloodstream, as it is less soluble than CO2.
- Risk of **oxidative tissue damage** with prolonged exposure.
*Carbon monoxide*
- **Carbon monoxide** is extremely **toxic** and binds irreversibly to hemoglobin with 200-250 times greater affinity than oxygen, forming **carboxyhemoglobin**, which impairs oxygen transport.
- Even minimal exposure can be life-threatening due to systemic hypoxia.
- Absolutely contraindicated for clinical use.
*Nitrous oxide*
- **Nitrous oxide** can diffuse into gas-filled spaces (bowel loops) 30x faster than nitrogen, potentially causing **bowel distension** and increased intra-abdominal pressure during prolonged procedures.
- Although less of a fire risk than oxygen, it can **support combustion** at high concentrations.
- Less rapidly absorbed than CO2, posing higher embolism risk if intravascular injection occurs.