Heat Stroke

Heat Stroke

Stuart Swadron MD, Mel Herbert MD and Bob Paquette MD

Take Home Points

• The most important priority in the treatment of heat stroke is immediate cooling.
• Cooling may be performed with a combination of ice packs, evaporative cooling and cooling pads.
• Patients will frequently need intubation and rocuronium is the agent of choice.
• Benzodiazepines are good option for sedation as they help protect against seizures.
• Cooling should be stopped when the patient reaches a normal fever temperature of 101-102F or 38.5 C.

• Herbert treated a UCLA student who wanted to get fit and was running up and down the hill while wearing a sweater. It was about 100 degrees. At first, he was a little altered but then he quickly worsened even though they were cooling him. He started seizing, developed DIC and died in front of them within an hour.
• We are approaching the time of year when some regions are subject to extreme heat.
• The hot and altered patient. You need to consider a broad differential diagnosis such as endocrine or infectious causes. However, for most of the heat stroke patients, you will have collateral information that will lead you to the diagnosis. If the paramedics are bringing in a grandma from a non-air-conditioned apartment, they will tell you it was really hot in there. Or the patient is high on methamphetamine and running down the street in a leather jacket.
• The diagnosis of heat stroke can be challenging at times. The official diagnosis discusses a core temperature greater than 104 F (40 C) degrees Fahrenheit with altered mental status. Frequently, the temperature is much higher and around 106-108F (41.1-42.2 C). The higher temperature can help narrow the differential diagnosis. Very few other conditions will generate a temperature that high.
• One pitfall is focusing on the classic heat stroke presentation of dry skin and not considering the diagnosis in a diaphoretic patient. For example, the elderly patient who has multiple comorbid conditions, is on multiple medications and is sitting in a hot apartment. In this scenario, the skin may be dry. This is different from exertional heat stroke. Exertional heat stroke is usually in a young healthy athlete or military recruit. These are people who are in great shape and they are working hard physically out in the heat. They are really sweaty.
  • An example of this was Korey Stringer, an offensive tackle for the Vikings, who was doing summer camp in Louisiana. He collapsed and was babbling nonsensically. The trainer brought him into an air-conditioned trailer and started an IV. The trainer thought that it was heat exhaustion rather than heat stroke because he was sweaty. Stringer sat in the trailer and began to seize. They transported him to a local emergency room where he had a core temperature of 108 F (42.2 C). They were unable to resuscitate him and he died.
• This is your first and primary priority. We know heat stroke has high mortality. The rate at which you cool them is linearly correlated to the mortality. The faster you cool them, the lower the mortality. One reason for delay in cooling is that the temperature is not taken quickly enough.
  • In one case, a young man was brought in for agitated delirium. He was in a wide complex tachycardia that was thought to be ventricular and he was shocked multiple times. It wasn’t until 10-15 minutes later that they realized that he was hot.  He had a core temperature of 108 F (42.2 C) and this was the core issue.  Waiting for placement of the Foley catheter to determine the temperature can result in significant delays.
  • A simple strategy is to place your hand on the chest. If someone is severely hypothermic or hyperthermic, you will know immediately and it can tip you off that you need to obtain a core temperature.
  • How do you cool the patient? There are multiple options. An effective technique is immersion in an ice water bath. However, this is not practical for most community emergency department Most of us don’t have tubs large enough for an adult. The patient may be intubated and it may be impractical to submerge them with monitoring. Some military bases will submerge them in an ice bath. Some work at raves and may have a set-up with ice filled bathtubs ready for hyperthermic patients.
  • In the hospital setting, we usually do evaporative cooling. The patient is stripped and misted with water and fans directed at bare skin. A potential pitfall is placing a wet sheet over the body. You need evaporation from the skin for this strategy to work.
  • How important is the temperature of the water? We are classically taught to use lukewarm water because ice cold water has the potential to trigger shivering. Our bodies don’t detect core temperature. Our body senses temperature through the skin. In practice, this is less concerning. Many of these patients will be intubated and if they are intubated, they will usually be paralyzed. You could also give benzodiazepines.
  • You can pack the patient in ice.
  • You can use the cooling pads for therapeutic hypothermia. This is a good way of cooling the patient’s back.
  • With a combination of evaporative cooling, packing in ice and using cooling pads, Paquette has been able to decrease a core temperature of 108 (42.2 C) to 101 (33 C) within 20 minutes. Every minute counts.
• What is your goal? A normal physiologic core temperature. People will frequently aggressively cool the patient to a core temperature of 98.6 F (37 C). However, if you cool the patient to a core temperature this low, their extremities and periphery will be much cooler. If you stop cooling them at 98.6 core, their body temperature will continue to drift down and you can actually make them hypothermic. You want to stop cooling when their core temperature hits 101 or 102 F (38.5 C), which is a normal fever temperature. Dry them off. Put a sheet on them and the core temperature will continue to drift down over the next hour.
• Heat stroke and hyperthermia are not a fever and should not be treated as such. It is not mediated by the hypothalamus. Medications like aspirin, NSAIDs and acetaminophen will not have any effect on this process. They may make things worse. These patients will have severe liver injury and possibly failure; pumping them full of acetaminophen won’t make this situation better.
• Airway management. Unless you are catching the patient very early in the process, most of these patients will require intubation. You have to use rocuronium. These heat stroke patients will commonly have a high potassium. Many of them will be in rhabdomyolysis or have acute tubular necrosis.  They may have a potassium of 7 or 8 mEq/L. If you use succinylcholine, you will kill them.  Rocuronium will also last 35-40 minutes and prevent shivering. By the time the rocuronium is wearing off, you will hopefully have cooled them.
• Benzodiazepines are a good agent for sedation when these patients are paralyzed. These patients are prone to seizures and this will help protect them.
• Do you need to adjust the ventilator settings? You want to have a higher minute ventilation. These patients are usually dry and acidemic. Starting them at a minute ventilation of 400cc and a rate of 12 will likely under-ventilate them. Start them on a higher rate and tidal volume until you get a blood gas back and can titrate your ventilator settings.
• Fluid management. One of the most common mistakes is to latch onto the classic teaching of heat stroke; that the little old lady with comorbid conditions cooking in her apartment is not very dehydrated and only needs 1-1.5L.  However, athletes with exertional heat stroke may be profoundly dehydrated. They may be 3-5 liters in the hole. You want to aggressively treat these patients. They usually will require large volumes. You will tailor your management to whether it is a classic heat stroke patient versus an exertional heat stroke patient. Paquette starts with normal saline and transitions to Lactated Ringers. Rhabdomyolysis, renal failure and hyperkalemia are common in these heat stroke patients. You can transition to a fluid other than normal saline at a later point.
• Exertional heat stroke patients such as marathon runners are losing fluids and salts in their sweats and replacing it with free water. Hyponatremia may become an important issue.
• When a patient first presents with heat stroke, they are in a shock state. They are usually profoundly hypoperfusing. Your first goal is to resolve that hypoperfusion. Don’t overthink the types of fluids. Fix the hypoperfusion with normal saline and then you will likely have a chemistry or i-stat back and can fine tune your sodium therapy.
• Heat stroke patients are going to be hypotensive. They are profoundly vasodilated and dehydrated. You can expect them to have systolic blood pressures in the 80s. The treatment is fluids and cooling, not pressors. The blood pressure will improve with cooling and IV fluid resuscitation. Pressors cause systemic vasoconstriction and can decrease the body’s ability to release heat. [Ed. Note they can also result in dysrhythmias in these patients] They don’t need it and it can make things worse.