Final answer:
The most common underlying and potentially reversible cause of pulseless electrical activity, in addition to hypoxia, is ischemia, which restrains blood and oxygen flow to the heart and brain.
Step-by-step explanation:
In addition to hypoxia, the most common underlying and potentially reversible cause of pulseless electrical activity (PEA) is ischemia, which involves reduced blood flow leading to decreased oxygen supply to tissues. Ischemia often affects the heart, causing cell death and impeding heart and brain function. To treat PEA, healthcare professionals attempt to identify and address the reversible causes, which in the case of ischemia may involve restoring blood flow and oxygen delivery to the affected tissues.