Which of the following is an H that may cause cardiac arrest?

• A. Hypoxia
• B. Tamponade (Cardiac)
• C. Toxins
• D. Thrombosis (Pulmonary and Coronary)

Answer: (A)

Recognizing the Hs that can cause cardiac arrest is the key idea here. Hypoxia is listed as an H because it means the heart and brain aren’t getting enough oxygen. When oxygen delivery drops, heart muscle cells can’t maintain normal electrical activity, which raises the risk of dangerous rhythms and ultimately cardiac arrest. The immediate corrective actions focus on restoring oxygenation—clear and open the airway, provide high-flow oxygen, and assist ventilation as needed while addressing the underlying cause.

The other options are important causes of arrest, but they’re not the H being highlighted in this item. Tamponade, toxins, and thrombosis fall under different categories in the Hs/Ts framework. In this question, hypoxia best fits the H category.