During permissive hypercapnia, which buffer is mentioned as helping maintain pH above 7.2?

• A. Tromethamine (THAM)
• B. Sodium bicarbonate
• C. Ammonia chloride
• D. Lactated Ringer's

Answer: (A)

Permissive hypercapnia aims to tolerate higher CO2 while keeping the blood pH from dropping too low. The buffer that best fits this scenario is Tromethamine (THAM). THAM acts as a proton acceptor and neutralizes hydrogen ions without generating additional carbon dioxide. It neutralizes acid directly and is then eliminated, largely avoiding the CO2 burden that comes with other buffering methods. That makes it effective for keeping pH above 7.2 even when CO2 levels are elevated.

Sodium bicarbonate, while it can raise pH, does so by converting buffering H+ into CO2 via the bicarbonate- carbonic acid system, which can worsen the hypercapnia you’re trying to limit. Ammonia chloride would acidify the blood, lowering pH rather than raising it. Lactated Ringer's contains lactate, which can act as a buffer under some conditions, but its effect is not as predictable or potent for maintaining pH in permissive hypercapnia, and it carries other fluid and electrolyte considerations.