Heat stroke and hypertension

Hypertension may have no obvious symptoms, so a home blood pressure reading does not rule out heat illness. Heat causes blood vessels to widen and sweating removes fluid; dehydration can then affect circulation. Some blood-pressure medicines, including water tablets, may alter fluid balance or the response to heat.

Do not stop or change prescribed treatment because of hot weather without advice. Heart failure, kidney disease, obesity and sleep-related breathing problems can also affect a person's heat plan. The key concern in heat stroke is new confusion, reduced alertness, collapse or seizure, not a particular blood pressure number.

Stay in a cool indoor space during the hottest part of the day, use shade and wear loose breathable clothing. Drink regularly unless your clinician has given a fluid restriction, and ask how that advice should be adjusted during heat or illness. Avoid heavy exertion and alcohol in extreme heat.

Keep a current medicine list and arrange a plan before a heatwave. If you feel dizzy or weak, stop activity, sit or lie in a cool place and cool your skin. Recheck blood pressure only if it does not delay help and do not use a reading to dismiss serious symptoms.

Call emergency services for confusion, fainting, collapse, seizure, chest pain, severe breathlessness or new weakness after heat exposure. These symptoms can signal heat stroke or a cardiovascular or neurological emergency. Cool the person while waiting and do not give drinks if they are confused or unable to swallow safely.

Ask whether your medicines affect sweating or fluid balance, whether you have a fluid limit, how to monitor blood pressure during heat, and which symptoms need same-day or emergency care. If you also have heart or kidney disease, request an individual hot-weather plan.