With the highest temperatures recorded in the last decade, now is a good time to review the heat-related illnesses we often encounter during summer months. From mild muscle cramps to stroke-like symptoms and coma, heat-related illnesses are diverse and must be recognized early for better chances of recovery.
The good news is that heat illnesses are preventable! By understanding the differences among various heat illness manifestations and identifying key signs in alerting the emergency medical system (EMS) promptly, I hope you and your family and friends stay safe for the rest of the summer.
Under normal conditions, the human body regulates its internal temperature through various mechanisms: diverting blood flow to the skin to help dissipate heat, sweating and maintaining proper hydration. However, in extreme heat, these processes are overwhelmed, causing an increase in internal temperature.
In order of increasing severity, there are four heat illnesses:
HEAT CRAMPS — These are felt as painful, involuntary muscle spasms that usually occur after exercise performed in high heat; this can happen indoors if there is insufficient air circulation. The most commonly affected muscle groups are the calves, thighs and shoulders. In addition to the muscle cramps, patients may report muscle twitching. There is usually no fever. Mental status changes with confusion are usually not seen.
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If these symptoms develop during exercise, whether indoors or outdoors, stop and take a break. Move to a cool area and hydrate with fluids, preferably those containing electrolytes like Gatorade and Powerade. My main concern with these electrolyte drinks is their high sugar content, so I recommend drinking them in moderation, such as when outdoors, exercising or during any activity.
Usually, a hospital visit isn’t necessary if symptoms improve.
HEAT SYNCOPE — Heat syncope is a sudden episode of dizziness or fainting that occurs while performing any activity outside. Although fainting has several causes, consider heat as the primary cause if considerable time was spent outdoors preceding the event. I have seen people who perform yard work and have fainted. There may or may not be muscle cramps. Fever is usually not seen.
Lightheadedness may worsen when standing after sitting for some time. If you feel lightheaded, sit down, move to a cool environment and drink plenty of water. If you have a fainting spell, you may warrant a visit to the emergency department (ED). A good rule of thumb is any patient with a history of heart disease or lung disease should consider a visit to the doctor or even the ED after such a spell. If symptoms fail to improve, come to the ED.
HEAT EXHAUSTION — Heat exhaustion is a more severe condition that involves the body losing large amounts of fluid through excessive sweating. The dehydration that results can lead to gastrointestinal symptoms of nausea and vomiting. Muscle cramps may or may not be present. The patient will become weak. There will be sweating. There may also be dizziness. Fever is often seen.
In these cases, patients usually present to the ED after family or friends call 911. An emergency workup follows to check for clinical dehydration and, in some cases, kidney failure. If caught early, treatment can reverse the deterioration in kidney function within hours to days. Patients with preexisting renal disease may take longer to recover their renal function. Most patients will need intravenous (IV) fluids. Not all patients will require hospitalization after the initial ED evaluation.
HEAT STROKE — Heat stroke is the most severe form of heat-related illness and is life-threatening. The body’s capacity to thermoregulate is overcome when the temperature rises above 104°F. Skin will be hot and dry. Sweating is impaired. Mental status changes are seen and can manifest in confusion, slurred speech, irritability and even seizures. Some people will faint. Others will manifest gastrointestinal symptoms, such as abdominal cramping, nausea and vomiting.
In the case of possible heat stroke, EMS must be activated. Call 911. The person must be moved to a cool environment. Remove any excess clothing. Attempt cooling measures by immersing in cool water or applying ice packs to the armpits, groin, neck and back. If the person is conscious try cold water drinking. Prompt hospital treatment is required to prevent organ damage.
Risk factors for developing any of the above heat conditions include being outside in warm weather. However, the temperature does not necessarily have to be above 90 degrees for heat illnesses to occur. I once admitted a patient who was working in the garage on his motorcycle; the outdoor temperature was 75 degrees. Despite the fan and the copious water drinking, he still developed heat exhaustion and had to be admitted to the hospital.
It is essential to note that these temperature thresholds are estimates, and vulnerable patients, such as the very young, the elderly and those with chronic conditions, may develop symptoms at lower temperatures.
Medication, such as antihistamines and diuretics, can precipitate dehydration. Alcohol and caffeine use can dehydrate especially when drinking outside. The key to reducing your risk of developing heat illnesses is to stay hydrated, even if you’re not thirsty. If you must be outside, limit time outdoors and choose hours before 10 a.m. and after 4 p.m. Wear light-colored, loose clothing. Use cooling fans.
Understanding the differences between heat-related illnesses can mean the difference between quick recovery and a potentially life-threatening situation. Recognizing early warning signs, understanding how these conditions differ and acting decisively can make the difference between early recovery and more serious health consequences.
Sources: 1. Sorensen C, Hess J. Treatment and prevention of heat-related illness. N Engl J Med. 2022;387:1404-13. PMID: 36170473 doi:10.1056/NEJMcp2210623.
Dr. Naznin Jamal is a Jefferson Regional Medical Center hospitalist.