Which of the following is an early sign of hypoxia?

• A. Dizziness
• B. Restlessness
• C. Nausea
• D. Shortness of breath

Answer: (B)

Restlessness as an early sign of hypoxia comes from how the brain reacts when it isn’t getting enough oxygen. When arterial oxygen drops, brain tissue becomes hypoxic and the body typically sends up signals through behavior and mental state changes. That brisk sense of unease, irritability, or agitation—often labeled as restlessness—can appear before more obvious physical symptoms. It’s a sensitive early cue that oxygen delivery to the brain is compromised.

Dizziness can occur with many conditions and isn’t specific to early hypoxia, so it isn’t as reliable a telltale sign in this context. Nausea is nonspecific and can be caused by numerous issues, including motion, medications, or stomach problems, making it a less precise indicator of hypoxia. Shortness of breath tends to reflect respiratory effort and discomfort that develop as hypoxemia worsens, so it generally shows up later than the initial brain-driven sign of restlessness.

So, the reason restlessness is the best answer is that cerebral hypoxia tends to manifest first as changes in mental status and behavior, making restlessness an early, more sensitive cue than the other symptoms listed.