On a nice sunny California day, you find yourself hiking through the redwood forest in Yosemite National Park.  As you come around a bend to a small opening among the trees, you find a husband and wife in the clearing. The wife comes up to you, she is frantic and says that her husband is not acting right and may have had a seizure.  You approach the husband and note that he is very sweaty, flushed in the face, confused and not answering questions coherently. You suspect that he has a heat related illness. Despite his protestations, you are able to coax him into the shade and apply cold-water compresses. The park rangers are notified and they transport him to an Emergency Room. 

Heat related illnesses range from benign heat cramps, to heat exhaustion, to heat stroke, a life-threatening emergency. Our Yosemite hiker likely had heat stroke. Heat related illnesses are becoming more prevalent with global warming and heat waves that occur more often and that are more intense.  In fact, last month, June 2019, was the warmest June ever recorded. The hot June was mostly driven by a heat wave in Europe.  Temperatures in France topped 110 degrees and in Athens the Acropolis was closed due to the heat.  There seemed to be no escape from the heat in June as Anchorage Alaska hit 90 degrees for the first time ever.

Heat stroke is a medical emergency and must be recognized and treated immediately. There are two types of heat stroke. In classic heat stroke, there is exposure to excess heat, as during a heat wave. The body cannot dissipate the heat in the environment. It occurs in the elderly, in chronically ill patients and in those who cannot take care of themselves (for example an infant in a hot car).  Exertional heat stroke occurs with excess production of heat. The body’s ability to dissipate the heat is overwhelmed by the heat produced. It strikes those who do strenuous physical activity, such as athletes, farm laborers, firefighters and soldiers. It does not always occur in hot weather and can happen at any time. Often overmotivation from peers or coaches drives the victim beyond what they can handle. In both types, there is a very high body temperature (often over 104 degrees), which leads to break down of tissue within the body, followed by multiorgan failure and, if not treated, death. 

Sign Up for E-News

Symptoms of heat stroke include high fever, fast heart rate, fast breathing, and low blood pressure. In exertional heat stroke there is sweating but the skin is dry in the classic form, reflecting the fact the body can’t adapt to the heat. The brain is very sensitive to high fever and heat stroke victims can have confusion, dizziness, agitation, combativeness, slurred speech, nausea, vomiting, seizures and loss of consciousness. The muscles of the body can break down and there is often kidney and/or liver damage as well.  The treatment of heat stroke is to cool the patient as quickly as possible. In the exertional form, immersion in cold water is often used.  In elderly, classic heat stroke victims, immersion is not practical so strategies include infusing a cool solution via an IV line, application of cold packs and using a cooling blanket. Promptly diagnosing heat stroke and rapid cooling often reverses heat associated organ problems, without long-term consequences. Staying indoors, in air conditioning, during heat waves, may prevent classic heat stroke. Prevention also includes checking on elderly or vulnerable persons frequently during heat waves to ensure that they are coping. 

Heart patients and patients with peripheral arterial disease are especially vulnerable to the heat. Cardiovascular problems can impair the body’s ability to open up blood vessels. If blood vessels cannot open up, heat cannot be dissipated through the skin and heat stroke results.   In addition, many heart medications can make handling the heat more difficult. Patients with high blood pressure and those with heart failure are often on diuretics (“water pills”).  These medications tend to dehydrate patients. If exposed to extreme heat while on a diuretic, the salt and water lost through sweat exacerbates dehydration, leading to low blood pressure, loss of consciousness or kidney problems. Other medications, such as calcium channel blockers, ACE inhibitors (for example, lisinopril) and ARBs (for example, losartan) coupled with excess heat can lead to low blood pressure. The best advice for heart patients in a heat wave is to stay inside, in air-conditioning. In addition, it is best not to walk, exercise or work in the yard in the middle of the day during hot days. Go outside early in the day or after sunset, when the temperature is generally lower. 

Enjoy the summer, but be cool and be careful on those hot humid days, don’t let a heat wave burn your heart.