Which of the following is considered an H in the H's & T's for cardiac arrest?

• A. Hypoxia
• B. Hypothermia
• C. Hydrogen Ion (Acidosis)
• D. Hyperkalemia

Answer: (A)

In the Hs and Ts framework for cardiac arrest, the Hs are reversible conditions that can cause or perpetuate arrest. Hypoxia is one of these Hs because a lack of oxygen delivery to the heart and brain directly suppresses electrical activity and tissue perfusion; restoring oxygenation and ventilation can often reverse the arrest.

Hypothermia, while it can provoke arrhythmias, is categorized with temperature-related issues and placed in the Ts group rather than the Hs. Hydrogen ion (acidosis) and Hyperkalemia are also Hs, representing metabolic disturbances that can trigger arrest and are treatable. Among the options, hypoxia clearly fits the H category, making it the best answer.