Heat Stroke and Passing Out

A person may lose consciousness when heat-related dehydration and circulation changes reduce blood flow to the brain. Heat stroke can also cause confusion, seizures and dangerous changes in breathing. Passing out may have other causes, including a heart problem or low blood sugar, so the person needs emergency assessment rather than an assumption that heat alone explains it. Vomiting can make dehydration and aspiration more concerning.

Call emergency services. Check whether the person is breathing normally. If they are not breathing normally, follow the dispatcher’s instructions. If they are breathing, place them on their side, move them to a cool area, remove excess clothing and cool the skin with water and airflow. Do not give food, drinks or medicines while they are unconscious. Stay nearby and watch for changes until help arrives.

Emergency care is required even if the person wakes quickly. Seek help for any collapse after heat exposure, especially with confusion, seizure, severe headache, hot skin, weakness, vomiting or a change in behaviour. Tell responders how long the person was unconscious, whether they struck their head, what activity they were doing and whether they have diabetes or heart disease.

Ask whether the collapse was consistent with heat stroke or another cause, which tests were performed, how to monitor recovery, and when the person may return to work, exercise or outdoor activity.