Some Like It Hot

As Seen in the Odessa American Medical Matters

http://www.oaoa.com/people/health/medical_matters/article_e4a67b46-8ab7-11e7-a364-833e575d9cdb.html

Well, it’s that time of year again … time for two-a-days, marching practice and heat illness. Heat illness is a very real threat, even in cooler climates than the Permian Basin. There are several risk factors for heat illness which I will discuss below. Heat illness actually occurs on a spectrum that ranges from heat cramps to heat exhaustion, and then to heat stroke. The physiology behind heat illness and heat regulation are very complex, and I won’t go into a lot of details here.

Risk factors for heat illness can be broken down into three main categories: medical conditions, environmental and drugs.

• Medical conditions that can put you at risk of heat injury are obesity, heart disease, high blood pressure, diabetes, hyperthyroidism, gastroenteritis or a febrile illness to name a few.
• Environmental factors include exercise in a hot environment, inappropriate clothing, decreased fluid intake, lack of acclimatization, enclosed hot environments such as a hot car or sauna and lack of air conditioning or proper ventilation.
• Some common medications or drugs that make you more susceptible to heat injury include: beta blockers (Atenolol, Metoprolol), diuretics, antihistamines (Benadryl, Claritin, Zyrtec), alcohol, cocaine, amphetamines (including Adderall) and aspirin. Basically, what these risk factors boil down to is impaired heat regulation.

So, what is the body’s normal response to heat stress? The first thing the body does is dilate the blood vessels and increase blood flow to the skin, which increases heat transfer to the environment. When this happens, the heart has to increase the heart rate to increase cardiac output. There is also release of catecholamines that causes you to sweat to dissipate heat by evaporation. The body also decreases heat-producing processes. Where you get into trouble and things start breaking down is when the body reaches its cardiac output limits in the face of water and electrolyte loss. This leads to the inability to regulate heat which causes damage to the cells and organs. If not stopped, this leads to multisystem organ failure and ultimately death.

The first stage of heat injury is heat cramps. This actually occurs with adequate hydration with water. When you are sweating, you lose electrolytes as well as water. If you are only replacing those losses with water, you actually will dilute your electrolytes, leading to involuntary muscle cramps. These cramps are usually treated with an oral salt solution or, sometimes in worse cases, with IV normal saline.

The next stage of heat illness is heat syncope. This is caused by a drop in blood pressure from a loss of fluids, dilation of the blood vessels and decreased vagal tone that leads to a lower heart rate. This most commonly occurs in elderly and people not acclimated to an environment. Symptoms include lightheadedness, nausea, yawning and restlessness. After the patient is flat on the ground, consciousness returns because blood flow has been restored. People who suffer heat syncope are generally not very dehydrated or hyperthermic. Treatment for this stage of heat illness includes moving the patient to a cool area out of direct sunlight, lying flat and elevating the feet.

Heat exhaustion is the next stage in the progression of heat injury. For heat exhaustion to occur, there is a significant heat stress, loss of fluid and salt depletion. Symptoms of heat exhaustion are weakness, fatigue, lightheadedness, headache, nausea and thirst. Signs of heat exhaustion include a rapid heart rate, rapid breathing rate, profuse sweating, low blood pressure and elevated body temperature. Treatment of heat exhaustion entails immediate cessation of activities, removal to a cool area out of direct sunlight, removal of restrictive clothing, aggressive fluid and electrolyte resuscitation and active cooling measures if the body temperature is above 100.4 degrees Fahrenheit. The best method to cool the body is to use room temperature water to soak the patient, and then fan him or her to cool by evaporation. You do not want to use ice and cold water because this causes shivering which actually raises body temperature.

Heat stroke is a life-threatening medical emergency. It is differentiated from heat exhaustion by the presence of central nervous system dysfunction such as ataxia, irritability, confusion, hallucinations, seizures and ultimately coma. The core body temperature is greater than 104 degrees Fahrenheit for heat stroke. A late sign of heat stroke is the lack of sweating (anhidrosis). In addition to the treatment measures listed for heat exhaustion, rapid cooling measures should be employed. The most effective way is ice packs to the areas where large blood vessels are located such as arm pits, groin, neck and scalp. A patient with heat stroke needs emergency medical care and evacuation to a medical facility. They need constant vital sign monitoring and support. The important thing to remember is that heat injury is not independent disease processes, but one continuum (i.e., a patient can progress).

Preventing Heat Stroke

Preventing heat stroke involves adequate hydration, acclimation and heat dissipation. You should drink enough fluid to have clear urine. This is a better goal than an amount of fluid to take in. If you are exercising in heat for more than two to three hours and are only drinking water, you should add salt to the fluid (¼ to ½ teaspoon per liter) or eat salt-containing foods. You can drink sports drinks such as Gatorade if you dilute it 50/50 with water. Otherwise there is too much sugar. Wear loose-fitting, light clothing to allow air circulation. Frequently spray or douse your skin with tepid water to allow evaporation. To acclimate to an environment, you should slowly increase activity levels over seven to 10 days. Children and elderly may need 10 to 14 days to acclimate.

Heat stroke can carry a mortality rate approaching 75 percent. Every year, about 200 people die of heat stroke. Often, they are young, healthy athletes with no prior issues. So, if someone is lagging behind, don’t tell them to “just suck it up” and keep going. The main thing is to be smart and be aware.