Heat Stroke: Vascular Event Or Not?

Heat stroke is a life-threatening condition that can be caused by high external temperatures and/or physical exertion. It is characterised by a body temperature greater than 40°C, along with symptoms such as red skin, headache, dizziness, and confusion. The condition can be subclassified as either classic (occurring when someone is at rest) or exertional (occurring through strenuous physical activity). Heat stroke results from an imbalance in heat production and heat dissipation. When the body's thermoregulatory mechanisms are overwhelmed, the core body temperature rises, leading to hyperthermia and central nervous system dysfunction. This can lead to seizures, rhabdomyolysis, or kidney failure.

The cardiovascular system plays a crucial role in heat dissipation, as it is responsible for dilating cutaneous vasculature and increasing cardiac output. Individuals with impaired cardiovascular function have a limited ability to increase stroke volume and cardiac output, which increases the risk of heat stroke. Additionally, those with pre-existing cardiovascular disease are more susceptible to the cardiovascular complications of heat stroke, including arrhythmias, myocardial ischemia, heart failure, shock, and sudden death. Therefore, it is important to consider the impact of cardiovascular function on the development of heat stroke and the associated risks.

Heat stroke and the elderly

Heat stroke is a severe heat illness that results in a body temperature greater than 40°C (104°F), along with red skin, headache, dizziness, and confusion. It is a life-threatening condition due to the potential for multi-organ dysfunction, including the cardiovascular system. Certain health conditions and medications can increase the risk of heat stroke, and it is often triggered by high external temperatures and/or physical exertion.

The elderly are particularly vulnerable to heat stroke due to age-related changes in the body's ability to regulate temperature and adapt to changes in body temperature. This vulnerability is further compounded by common health conditions and medications associated with older age. Age-related changes to the skin, such as poor blood circulation and inefficient sweat glands, can impair the body's ability to cool down. Additionally, older adults are more likely to have heart, lung, and kidney diseases, as well as other illnesses that cause general weakness or fever, all of which increase the risk of heat stroke.

The impact of heat stroke on the elderly can be severe, with a mortality rate exceeding 50% in classic heat stroke cases. The risk factors and consequences are often interconnected and exacerbated by the vulnerabilities associated with older age. For example, medications commonly taken by older adults, such as diuretics, sedatives, tranquilizers, and certain heart and blood pressure drugs, can reduce sweating and further compromise the body's ability to regulate temperature. Polypharmacy, or taking multiple medications for various conditions, is also common in older adults and can increase the risk of heat stroke and its complications.

Lifestyle factors can also increase the risk of heat stroke in the elderly. For example, living in extremely hot climates without access to air conditioning, lack of transportation to cooler locations, and not understanding how to respond to weather conditions can all contribute to the risk. Social isolation is another critical factor, as there may not be someone to support or check in on the elderly person during extreme heat.

To prevent heat stroke in the elderly, it is crucial to take precautions during hot weather. This includes staying in air-conditioned spaces or cool areas, wearing lightweight and light-colored loose-fitting clothing, and staying hydrated by drinking plenty of fluids. It is also important to be aware of the signs and symptoms of heat stroke, such as high body temperature, behavioural changes, confusion, dizziness, and dry or flushed skin. Seeking immediate medical attention is essential if heat stroke is suspected.

In summary, heat stroke poses a significant risk to the elderly due to age-related changes, common health conditions, medications, and lifestyle factors. Taking preventive measures, being aware of the signs and symptoms, and seeking prompt medical attention are crucial to reducing the risk and impact of heat stroke in this vulnerable population.

Heat stroke and children

Heat stroke is a severe heat illness that results in a body temperature greater than 40°C (104°F), along with red skin, headache, dizziness, and confusion. It is a life-threatening condition due to the potential for multi-organ dysfunction, with typical complications including seizures, rhabdomyolysis, or kidney failure.

Children are particularly vulnerable to heat stroke due to age-specific physiological differences. They have an increased surface area-to-mass ratio, leading to increased heat absorption, an underdeveloped thermoregulatory system, a decreased sweating rate, and a lower blood volume-to-body size ratio, resulting in decreased compensatory heat dissipation.

Heat stroke in children can have severe consequences and requires immediate medical attention. It occurs when a child's body creates and retains more heat than it can release, resulting in a rapid increase in core body temperature. This can lead to brain damage or even death if not treated promptly.

The signs of heat stroke in children include:

• A body temperature that rises above 104°F
• Confusion and disorientation
• Flushed, hot, and dry skin (although skin may also be wet)
• Loss of consciousness
• Nausea, vomiting, and diarrhea
• Rapid heartbeat and breathing
• Weakness and dizziness

To prevent heat stroke in children, it is crucial to ensure they stay properly hydrated, wear lightweight and light-colored clothing, and take frequent breaks in cool, shaded areas. It is also recommended to schedule outdoor activities during the cooler times of the day, such as early morning or late evening, and to seek medical attention immediately if any symptoms of heat stroke are observed.

In 2022, 33 children in the United States died from heat stroke, highlighting the importance of recognizing the signs and taking preventive measures to protect children from this dangerous condition.

Heat stroke and cardiovascular disease

Heat stroke is a severe heat illness that results in a body temperature greater than 40°C, along with red skin, headache, dizziness, and confusion. It is a life-threatening condition due to the potential for multi-organ dysfunction, including the cardiovascular system.

Under thermal stress, the human body achieves heat dissipation through the evaporation of sweat and increased cutaneous blood flow. When these mechanisms are overwhelmed, the core body temperature rises, leading to heat stroke. Heat dissipation relies on an intact cardiovascular system to dilate cutaneous vasculature and increase cardiac output. Individuals with impaired cardiovascular function have a limited ability to increase stroke volume, cardiac output, and blood flow to the skin, increasing the risk of heat stroke.

Those with underlying cardiovascular disease are more susceptible to heat stroke and its cardiovascular complications, including arrhythmias, myocardial ischemia, heart failure, shock, and sudden death. The majority of excess deaths during heat waves are of cardiovascular origin, highlighting the impact of heat stroke on the cardiovascular system.

Classic (non-exertional) heat stroke typically affects older individuals and those with underlying chronic diseases that impair the body's ability to dissipate heat. Conversely, exertional heat stroke usually affects younger individuals, such as athletes, outdoor workers, or military personnel, whose production of heat due to exertion exceeds the body's ability to dissipate it.

Heat stroke results from an imbalance in heat production and heat dissipation. When the body is unable to regulate its temperature effectively, it can lead to a dangerous rise in core body temperature. This can be due to excessive metabolic heat production, high external temperatures, insufficient heat loss, or a combination of these factors.

The pathophysiology of heat stroke involves intense heat overload followed by a failure of the body's thermoregulatory mechanisms. This can lead to inflammatory and coagulation responses that damage the vascular endothelium and result in platelet complications. Additionally, there is growing evidence of a second pathway involving heat and exercise-driven endotoxemia, where extreme exercise and heat disrupt the intestinal barrier, allowing bacteria and their metabolites to enter the circulatory system and trigger a systemic inflammatory response.

The impact of heat stroke on the cardiovascular system is significant. It increases the stress on the heart, and in patients with underlying cardiovascular disease, the demand for heat dissipation can overwhelm the heart, resulting in various cardiac complications. These include sinus tachycardia, atrial fibrillation, conduction disturbances, myocardial ischemia, and, in severe cases, heart failure, circulatory collapse, and death.

The management of heat stroke involves rapid cooling to a target temperature of less than 39°C, along with standard resuscitation measures. Cooling can be achieved through various methods, including cold water immersion, cold intravenous fluids, ice packs, and fanning.

In summary, heat stroke is a life-threatening condition that has a significant impact on the cardiovascular system. Individuals with impaired cardiovascular function are at an increased risk of developing heat stroke, and those with underlying cardiovascular disease are susceptible to its cardiovascular complications. The management of heat stroke requires rapid cooling and supportive care to prevent further cardiovascular and other organ damage.

Heat stroke and medication

Heat stroke is a severe heat illness that results in a body temperature greater than 40°C (104°F), along with red skin, headache, dizziness, and confusion. It is a life-threatening condition that can lead to multi-organ dysfunction and even death. Certain medications can increase the risk of heat stroke and impact its treatment.

Medications that Increase the Risk of Heat Stroke:

• Beta-blockers: These medications can impair the body's ability to increase cardiac output in response to thermal stress, making it harder to regulate body temperature.
• Non-dihydropyridine calcium channel blockers: Similar to beta-blockers, these drugs can hinder the body's ability to regulate temperature by impacting cardiac output.
• Diuretics: By increasing fluid loss, diuretics can exacerbate dehydration and electrolyte imbalances, which are risk factors for heat stroke.
• Renin-angiotensin system inhibitors (angiotensin-converting enzyme inhibitors and angiotensin receptor blockers): These medications increase the risk of acute kidney injury, which is a potential complication of heat stroke.
• Oral hypoglycemic agents (like metformin, sulfonylureas, and sodium-glucose co-transporter 2 inhibitors): In a state of dehydration, these medications can have detrimental effects.
• Antipyretics (e.g., aspirin): While useful for treating fevers, antipyretics are not effective for heat stroke and may worsen associated conditions like coagulopathy and liver dysfunction.

Medications Used in the Treatment of Heat Stroke:

• Benzodiazepines: These are used to provide sedation, control convulsions, and manage shivering in patients with heat stroke. Lorazepam is often the drug of choice due to its effectiveness, rapid onset of action, and duration of effects. Midazolam, a short-acting benzodiazepine, is useful for sedation during short procedures and may help with convulsions.
• Barbiturates (e.g., phenobarbital): If benzodiazepines are ineffective, barbiturates can be used to control convulsions.
• Alkalinizing agents: These are indicated for severe acidosis and rhabdomyolysis, a breakdown of skeletal muscle that releases muscle products into the bloodstream, causing organ dysfunction. Sodium bicarbonate is used to prevent acute renal failure by alkalizing the urine. Mannitol, a diuretic, is also used to force diuresis and has beneficial effects on the kidneys.
• Adrenergic agonist agents: These drugs produce vasodilation and increase the inotropic state. Dobutamine is the drug of choice for circulatory support in heat stroke.

It is important to note that the treatment of heat stroke primarily involves rapid physical cooling of the body and supportive care. Medications play a role in managing specific symptoms and complications but are not the first line of treatment.

Heat stroke prevention

Heat stroke is a life-threatening condition that requires immediate medical attention. It is a severe heat illness that results in a body temperature greater than 40°C, along with red skin, headache, dizziness, and confusion. It can lead to seizures, rhabdomyolysis, or kidney failure, and in some cases, even death.

• Stay in a Cool Environment: Try to stay in an air-conditioned place as much as possible. If your home does not have air conditioning, spend time in shopping malls, public libraries, or cooling centres to give your body a break from the heat.
• Wear Appropriate Clothing: Opt for lightweight, loose-fitting clothing in light colours. Wide-brimmed hats and sweatbands soaked in cool water can also help keep your body temperature down.
• Stay Hydrated: Drink plenty of cool liquids, and if you're engaging in physical activity, drink fluids before, during, and after to replace the fluids lost through sweating. Avoid sugary, alcoholic, and very cold drinks.
• Replace Electrolytes: Heavy sweating removes salt and minerals from the body, so it's important to replace them. Consider drinking sports drinks or consuming mineral salts to maintain electrolyte balance.
• Avoid Strenuous Activities: Limit your outdoor activities during the hottest parts of the day. If you must engage in physical labour or exercise, do so during cooler times, such as early morning or evening. Take frequent breaks and rest in shady areas.
• Be Cautious with Medications: Some medications can affect your body's ability to stay hydrated and regulate temperature. Consult your healthcare provider to understand the impact of your medications and take extra precautions if needed.
• Protect Against Sunburn: Sunburn impairs your body's ability to cool down, so be sure to use sunscreen with an SPF of at least 30, wear protective clothing, and avoid peak sun hours.
• Check on High-Risk Individuals: Infants, young children, the elderly, and people with certain health conditions are at higher risk of heat stroke. It is important to frequently check on them and ensure they are staying cool and hydrated.
• Never Leave Anyone in a Parked Car: Cars can quickly heat up to dangerous temperatures, even with a window slightly open. Leaving anyone, especially children, in a parked car can be fatal.
• Monitor Your Body: Know the signs and symptoms of heat stroke, such as behavioural changes, confusion, dizziness, nausea, rapid breathing, and a racing heartbeat. If you experience any of these, stop all activity and move to a cool area immediately.

Frequently asked questions