Hot As Hell
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Nathan Cleveland, MD, MS
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Hot As Hell
- 2. CASE #2INTRODUCTION CASE #1
- 3. CASE #2INTRODUCTION CASE #1
- 4. CASE #2INTRODUCTION CASE #1
- 5. CASE #2INTRODUCTION CASE #1
- 6. CASE #2INTRODUCTION CASE #1
- 7. CASE #1 CASE #2INTRODUCTION
- 8. OBJECTIVESCASE #1 CASE #2
- 9. CASE #2 OBJECTIVESCASE #1
- 12. OBJECTIVES OBJECTIVES MORTALITYCASES 1. Review heat stroke 2. Identify best practices for management
- 13. MORTALITY HEAT ILLNESSOBJECTIVES Leon LR, Helwig BG. Heat stroke: Role of the systemic inflammatory response. J Appl Physiol 2010;109:1980-8. HEAT STROKE Mortality rate? 21-63%
- 14. HEAT ILLNESS MANAGEMENTHYPERTHERMIA Khosla R, Guntupalli KK. Heat-related illnesses. Crit Care Clin 1999;15:251-63 HEAT-RELATED ILLNESS End-organ Dysfunction = “Heatstroke”
- 15. MANAGEMENT HEAT STROKEHEAT ILLNESS Bouchama A, Knochel JP. Heat Stroke. N Engl J Med 2002;346:1978-88 Supportive Care Rapid Cooling MANAGEMENT
- 16. HEAT STROKE HEAT BALANCEMANAGEMENT Bouchama A, Knochel JP. Heat Stroke. N Engl J Med 2002;346:1978-88 HEAT STROKE CLASSIC EXERTIONAL
- 17. HEAT BALANCE CONDUCTIONHEAT STROKE Lugo-Amador NM, Rothenhaus T, Moyer P. Heat-related illness. Emerg Med Clin N Am 2004;22:315-27. HEAT BALANCE HEAT IN HEAT OUT RADIATION TEMPERATURE METABOLISM RADIATION CONVECTION CONDUCTION EVAPORATION
- 18. CONDUCTION EVAPORATIONHEAT BALANCE Lugo-Amador NM, Rothenhaus T, Moyer P. Heat-related illness. Emerg Med Clin N Am 2004;22:315-27. HEAT BALANCE HEAT IN HEAT OUT RADIATION TEMPERATURE METABOLISM RADIATION CONVECTION EVAPORATION X CONDUCTION
- 19. CONDUCTION EVAPORATIONHEAT BALANCE Exerc Sport Sci Rev 2007;35:141-9. CONDUCTION Cold Water Immersion
- 20. CONDUCTION CONDUCTION Ice Packs Kielblock AJ, Van Rensburg JP, Franz RM. Body cooling as a method for reducing hyperthermia: An evaluation of techniques. S Afr Med J 1986; 69:378-80 EVAPORATION CONVECTION
- 21. Resus 2007;73:46-53 CONDUCTION Cold IV Fluids CONDUCTION EVAPORATION CONVECTION
- 22. Aviation, Space, Enviro Med. 2009;80:720-2. EVAPORATION Mist / Water-Dousing EVAPORATION CONVECTIONCONDUCTION
- 23. CONVECTION SUMMARYEVAPORATION Wyndham CH, Strydom NB, et al. Methods of cooling subjects with hyperpyrexia. J Appl Physiol. 1959;14:771–776. CONVECTION Fans
- 24. SUMMARY NEW IDEASCONVECTION COMBINATION Fans + Mist / Dousing
- 25. SUMMARY SUMMARY NEW IDEASCONVECTION Immersion 0.2-0.35 ⁰C/min Water+Fans 0.15-0.25 ⁰C/min Dousing + Ice Massage 0.2 ⁰C/min Cool IV Fluid 0.015-0.076 ⁰C/min Ice Packs 0.028-0.034 ⁰C/min Fan Alone 0.02-0.04 ⁰C/min Casa DJ, et al. Cold water immersion: the gold standard for heat stroke treatment. Exerc Sport Sci Rev 2007;35:141-9.
- 26. NEW IDEAS TAKE HOMESUMMARY Acad Emerg Med 2001;17:360-7. FUTURE DIRECTIONS Cooling Blankets / Garments
- 27. TAKE HOME THE ENDNEW IDEAS FUTURE DIRECTIONS Metabolism - Intubation
- 28. J Parenter Enteral Nutr. 2003;27:27-35. FUTURE DIRECTIONS Metabolism - Paralysis TAKE HOME THE ENDNEW IDEAS
- 29. TAKE HOME THE ENDNEW IDEAS
- 30. THE ENDTAKE HOME TAKE HOME 1. Aggressive supportive care
- 31. THE ENDTAKE HOME TAKE HOME 2. Rapidly cool by: -Cooling blanket -Ice massage -Cool IV fluids -Water dousing / Mist -Fans
- 32. THE ENDTAKE HOME TAKE HOME 3. Consider: -Early intubation / mechanical ventilation -Short period of neuromuscular blockade
- 33. THE ENDTAKE HOME
Notas del editor
- Hi, my name is Nathan Cleveland and today I would like to talk to you about the patient who arrives in your ED ‘hot as hell’ and what the evidence tells us about managing heatstroke patients.
- But first, let me say, “welcome to Las Vegas.” I’m not just here for this conference. I actually live and work in this town at University Medical Center just between here and downtown. As you would expect, emergency medicine here is pretty glamorous. But we do see a lot of what you would expect to see in a hot desert environment.
- Things like…
- And…
- And of course… Believe me, I couldn’t make this stuff up if I tried. These are all real chief complaints from our electronic tracking board.
- But what I really want to talk to you about today, is the patient who comes in hot. Because unlike ‘falling off a stripper pole,’ ‘being sad that Michael Jackson died’ or ‘waking up naked next to your bike at the pig farm’ – ‘hot’ kills.
- I was working an afternoon shift back in August of last year when this man was brought in to the department. A 34yo Hispanic male landscaper with no health problems, on no medications and with no reported history of drug abuse. His friends stated that he was ‘tired all day’ and ‘quieter than normal.’ Then when they were walking back to their truck at the end of a job, he fell to the ground unresponsive. EMS arrived and transported the patient. En route, he began seizing. When arrived to the ED, he was no longer seizing but had a GCS score of 6 and was immediately intubated.
- Although it is hard to read, this was the initial core temperature we recorded – 109.2. For any of you not from the United States, Belize or Palau, that’s 42.9 C
- Three weeks later, a 42yo female with a history of methamphetamine abuse was found unconscious next to a bus stop. As I said, it’s a pretty glamorous place… No additional information about medications or recent drug abuse could be obtained. She also arrived to the department obtunded and required immediate intubation.
- This is even a little harder to read, but her initial core temperature was 107.1. Again, for the very educated, that’s 41.7 C
- Since we are the premier academic and tertiary care hospital in southern Nevada, I of course used our cutting edge and high-tech cooling equipment. Namely, a cafeteria cart full of buckets of ice and an industrial fan. Unfortunately the male patient never even made it out of the emergency department and died of cardiovascular collapse approximately 2.5 hours after arrival. The female patient was admitted to the ICU, but ultimately died prior to hospital discharge. Maybe these patients’ fates were sealed before they arrived in my department, but I had a very difficult time adequately cooling either of these patients and I began to wonder whether I really knew what the current best available literature was regarding rapid cooling of heatstroke patients.
- I really only have two objectives for this short talk. First, I want to briefly define the heatstroke problem. Second, I want to go to the literature to identify the best practices for management of heatstroke and try to provide you with some strategies to take back to your shop.
- So, let’s talk about heat stroke mortality. Who here thinks the mortality rate for patients arrive with a temp greater than 40 C is 0-5%? 5-10%? 10-15%? 15-20% Anyone think it’s over 20%??... 21-63%!!! Are you kidding me? The mortality from heat stroke is remarkably high! With the exception of cardiac arrest, I can’t think of many emergency conditions with that high of a mortality rate. This is unacceptable. And this mortality is due to multi-organ system failure. Heatstroke can cause dysfunction to almost every system and common findings include… AMS, Sz, renal failure, CHF, ARDS, DIC, electrolyte abnormalities, dysrhythmias, rhabdomyolysis, etc., etc.
- I do just want to briefly mention terminology here. Obviously, when apt is found to be hotter than they should be, you have to consider a broad differential for that hyperthermia. But once you have established that you are dealing with hyperthermia as a result of environmental or exertional factors, there is always a lot of discussion about the correct terminology. Is it “heat cramps,” “heat exhaustion,” “sun stroke” or “heat stroke?” Well, Vegas is a food-crazy town, so let’s use a food analogy. Think of it as degrees of doneness like a steak which ranges from rare to well-done. The only point on this spectrum that you need to know is that when you have evidence of end-organ dysfunction, the patient is classified as having “heat stroke” and the aggressiveness of your care needs to be escalated.
- When it comes to management, you really only have 2 options. I’m going to assume that you are all experts in supportive care – things like intubation and mechanical ventilation, controlling seizures, correcting electrolyte abnormalities, etc. so we will focus on what the literature says about rapid cooling.
- Historically, there has been a focus on dividing heat stroke into two types. Classic heatstroke is seen in elderly, obese and psychiatric patients who have comorbid disease. Essentially, these are people who have difficulty removing themselves from the hot environment.Exertional heat stroke, on the other hand, occurs in young and otherwise healthy patients. Frequently athletes, military recruits and manual laborers. This distinction is irrelevant – since heat stroke is all about the heat balance…
- There are two external sources of heat: radiation from the sun, and the ambient temperature if that temperature is greater than the patient’s core temperature – these are both big contributors in an environment like Las Vegas. Metabolism however, is the biggest source of heat – after all, we’re warm-blooded creatures and we have been designed to create heat. There are 4 ways to dissipate heat: evaporation – which is facilitated by sweating and the large surface area of our skin, but also occurs with respiration; radiation – is a relatively small contributor to heat loss; conduction – which requires contact with a cooler object such as an icepack; and convection – which can be thought of as conduction to the air immediately around us, followed by removal of that air by wind.
- Assuming the patient is already in your department, they have been removed from the radiation of the sun and the hot environment. That leaves you with these five processes by which you can attempt to cool the patient. Unfortunately there is little you can do to increase the negligible amount of heat lost via radiation. Let’s look at what the literature says about cooling via each of these mechanisms.
- Strategy #1 is cold-water immersion. Who has heard that cold water immersion can actually paradoxically RAISE core temperature due to peripheral vasoconstriction? Turns out that that is not true. Two separate systematic reviews have found that cold water immersion leads to the most rapid decrease in core body temperature – approaching 1/3 degree Celsius per minute. The biggest problem with water immersion is that very few of us have tubs in our departments and placing an altered or obtunded pt in cold water makes supportive care very difficult.
- Ice packs have usually been studied in conjunction with other methods, however, one study looked at ice packs alone. They found cooling rates between 0.028-0.034 C/min.
- Cold IV fluids have been studied in the setting of heat stroke as well as in induced therapeutic hypothermia. I consider this to be an example of conductive cooling as well and numerous studies have shown cooling rates on the order of 0.015-0.076 C/min
- What about my strategy of mist or water dousing? When I was in residency I remember being taught that this was the most rapid way to cool a patient. Much of this early work was performed by a Dr. Khogali in the middle east but more recent studies have confirmed that keeping the skin moist in order to increase evaporation can cool the pt up 0.076 C/min. I especially like this study which combined water dousing (evaporative cooling) with ice massage (conductive cooling) and found cooling rates close to 70% as rapid as water immersion.
- What about fans alone (convection without evaporation)? Well, it’s relatively ineffective – the fact that it hasn’t really been studies since 1959 tells you something. The only recent study actually used a helicopter downdraft as the fan – which I can’t entirely endorse. Rates are in the 0.02-0.04 C/min.
- But when you combine the two previous strategies - fans (convection) with mist or water dousing (evaporation) you get much-improved cooling rates of around 0.15-0.25 C/min.
- With the advent of therapeutic hypothermia protocols, many of us have these devices in our departments. I am a big fan of using these in a modified way in the hyperthermicpatient. Let me explain why. With traditional cooling strategies like mist and fans, ice massage or ice packs, almost 50% of the patient’s surface area is in contact with the hospital bed and is actually well-insulated. Since we can’t hang the patient from the ceiling, I advocate placing cooling blankets or garments under the patient. This strategy has not been studies in heat stroke patients but we know from the therapeutic hypothermia literature that…
- Often your severely hyperthermic patient will need intubation for airway protection. But there is an additional theoretical reason for considering mechanical ventilation. The work of breathing itself contributes about 5-10% of our basal metabolic rate. We are unable to influence the majority of processes contributing to BMR - but we can decrease the work of breathing. This has not been studied in heat stroke but I believe it is worth looking into in the future.
- What about using neuromuscular blocking agents to decrease the heat generated by metabolism. Numerous studies have shown that NMBs reduce oxygen consumption and energy expenditure. I think it is worth investigating whether short-term neuromuscular blockade could help speed cooling rates. In addition, since shivering is often triggered by a drop in temperature (rather than absolute temperature) neuromuscular blockers can prevent heat generation by shivering.
- So… what’s the take home message of all of this? Well, it’s safe to say yourpt needs more than just some cowbell. How can you modify your practice to give your patient the best chance of survival?– here are my recommendations for management of heatstroke, based on the current best available evidence…
- First, aggressively support your patient.
- Rapidly cool the patient by: Conduction – with cooling blankets UNDER the patient; ice massage on OVER the patient; and cool IV fluids running IN the patient. Evaporation – with water dousing or cold water mist. And Convection – by fanning the patient, which will also speed evaporative cooling. I should point out that in order to do this, you should plan ahead by storing 1-2 liters of IV fluid in a medication refrigerator and know who to call in order to get your maintenance crews’ fan.
- If you act early and aggressively, with a focus on cooling, you have the chance to…
- Thank you for your attention. I’d be happy to take any questions?