Compared with CO2, Nitric Oxide as an insufflation gas is associated with which acid-base effect?

• A. Less acid-base disturbance
• B. More acidosis
• C. No difference in acid-base balance
• D. Severe metabolic alkalosis

Answer: (A)

When looking at acid-base effects of pneumoperitoneum gases, the crucial point is how the gas dissolves in blood and alters CO2 levels. CO2 is highly soluble and readily absorbed from the peritoneal cavity into the bloodstream. As CO2 accumulates in blood, it combines with water to form carbonic acid, which dissociates to hydrogen ions and bicarbonate, increasing H+ and lowering pH (a mild respiratory acidosis if ventilation isn’t increased). Nitric oxide, on the other hand, does not form carbonic acid in the same way and does not contribute a significant CO2 burden to the bloodstream. Therefore, using nitric oxide as the insufflation gas would produce less CO2-related acid-base disturbance than CO2, leading to a more stable acid-base status. Some other gas-related effects of NO exist (such as possible methemoglobinemia or vasodilatory effects), but the acid-base impact is diminished compared with CO2.