It is summer and the dog days will soon to be upon us...
You are working in a beautiful temperature controlled emergency department (which you are particularly thankful for because local weather has hit highs of 99-100 for past 4 days straight.) Today is another hot one. As you look outside the window you marvel at the refracting heat waves rising from the tar based parking lot.
You then notice a van pull up to the front Emergency Department doors. Out rushes a parent, opens the passenger door, scoops up what appears to be a 5 year old boy, and runs into the triage area.The boy is rushed back to the resuscitation room. He had been playing outside for most of the day when Mom decided to drive to the local Walmart. The boy had been misbehaving so she left him inside the van for "just a minute...with the windows cracked." Upon returning to the van she found him disoriented, then difficult to arouse.
You initially see a 5 year old boy who appears to be very agitated. His clothes are eventually removed. He struggles with mom and nurses to stay on the gurney, then becomes minimally responsive. You note that his speech sounds slurred and mom agrees that he is not speaking in his normal voice. He otherwise appears to be protecting his airway. His pulse is rapid about 160 and his skin is pink and dry.
Vital signs are obtained: Rectal temp 41 C (105.8), Pulse 160, BP 80/60, RR 20, Sats 100%
You complete your secondary survey: Head is atraumatic. Eyes: mild nystagmus. Oral: mucus membranes are dry. Neck supple. Cardiac: tachy without murmur. Resp: tachypnic otherwise clear. Abdomen: non-tender. Neuro: confused, agitated, slurred speech. No other focal deficits. Skin: pink-flushed, and dry to touch.
Mom notes that he has a history of ADHD for which he takes a medicine, but is otherwise healthy.
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What is your next step(s).
How would you cool this patient?
What associated disease processes are you concerned about in a hyperthermic patient?
What Labs would you order?
Are there certain drugs or conditions that predispose a patient to developing heat stroke or heat exhaustion?
Who is at greatest risk for heat stroke?
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Weekend Update
Heat cramp usually follows severe work stress (such as an overnight shift at ANW during Excellian Downtime). It is most likely to occur in well conditioned individuals. It usually follows severe work stress during a period of relaxation. It can be associated with abnormal electrolytes.
Heat Exhaustion is broken down into two forms: Type A: Water Depletion and Type B: Salt Depletion. Temps are usually less than 39C (102.2F). Heat exhaustion usually occurs in individuals who are unacclimatized to the environment. A variety of symptoms can occur: lethargy, thirst, headache, vomiting, CNS dysfunction, low bp, elevated HR, muscle cramps.
Heatstroke is defined as hyperthermia exceeding 41°C and anhidrosis associated with an altered sensorium. It is reported to affect those at the extremes of age. Infants in closed cars are particularly at risk. Also pediatric patients who undergo extreme exertion (such as athletes practicing in extreme conditions.) It can present with complete circulatory collapse, severe CNS dysfunction, Rhabdomyolysis, and renal failure.
Get a RECTAL TEMP (Much More ACCURATE)
Clinically, 2 forms of heatstroke are differentiated: Exhertional and Non-exhertional.
Exertional heatstroke
EHS is characterized by hyperthermia, diaphoresis, and an altered sensorium, which may manifest suddenly during extreme physical exertion in a hot environment.
A number of symptoms (eg, abdominal and muscular cramping, nausea, vomiting, diarrhea, headache, dizziness, dyspnea, weakness) commonly precede the heatstroke and may remain unrecognized. Syncope and loss of consciousness also are observed commonly before the development of EHS.
EHS commonly is observed in young, healthy individuals (eg, athletes, firefighters, military personnel) who, while engaging in strenuous physical activity, overwhelm their thermoregulatory system and become hyperthermic. Because their ability to sweat remains intact, patients with EHS are able to cool down after cessation of physical activity and may present for medical attention with temperatures well below 41°C. Despite education and preventative measures, EHS is still the third most common cause of death among high school students.
Risk factors that increase the likelihood of heat-related illnesses include a preceding viral infection, dehydration, fatigue, obesity, lack of sleep, poor physical fitness, and lack of acclimatization. Although lack of acclimatization is a risk factor for heatstroke, EHS also can occur in acclimatized individuals who are subjected to moderately intense exercise.
EHS also may occur because of increased motor activity due to drug use, such as cocaine and amphetamines, and as a complication of status epilepticus.
Nonexertional heatstroke
Classic NEHS is characterized by hyperthermia, anhidrosis, and an altered sensorium, which develop suddenly after a period of prolonged elevations in ambient temperatures (ie, heat waves). Core body temperatures greater than 41°C are diagnostic, although heatstroke may occur with lower core body temperatures.
Numerous CNS symptoms, ranging from minor irritability to delusions, irrational behavior, hallucinations, and coma have been described.
Anhidrosis due to cessation of sweating is a late occurrence in heatstroke and may not be present when patients are examined.
Other CNS symptoms include hallucinations, seizures, cranial nerve abnormalities, cerebellar dysfunction, and opisthotonos.
Patients with NEHS initially may exhibit a hyperdynamic circulatory state, but, in severe cases, hypodynamic states may be noted.
Classic heatstroke most commonly occurs during episodes of prolonged elevations in ambient temperatures. It affects people who are unable to control their environment and water intake (eg, infants, elderly persons, individuals who are chronically ill), people with reduced cardiovascular reserve (eg, elderly persons, patients with chronic cardiovascular illnesses), and people with impaired sweating (eg, patients with skin disease, patients ingesting anticholinergic and psychiatric drugs). In addition, infants have an immature thermoregulatory system, and elderly persons have impaired perception of changes in body and ambient temperatures and a decreased capacity to sweat.
Other Diagnosis to consider:
- Delirium
- Delirium Tremens
- Diabetic Ketoacidosis
- Encephalopathy, Hepatic
- Encephalopathy, Uremic
- Hyperthyroidism
- Meningitis
- Neuroleptic Malignant Syndrome
- Tetanus
- Toxicity, Cocaine
- Toxicity, Phencyclidine
- Toxicity, Salicylate
Labs to consider: BMP, CK, Lactate, LFTs,
Treatment: COOLING, COOLING, COOLING
The goal of treatment is to reduce the temperature by at least 0.2°C/min to approximately 39°C. Active external cooling generally is halted at 39°C to prevent overshooting, which can result in iatrogenic hypothermia.
The optimal method of rapidly cooling patients is a matter of debate; each method has its own theoretical advantages and disadvantages.
- Ice-water immersion or an equivalent method is an extremely effective method of rapidly reducing core body temperature and traditionally was the most frequently recommended method. The increased thermal conductivity of ice water can reduce core body temperature to less than 39°C in approximately 20-40 minutes. The practice has been criticized recently. Theoretically, the ice water, which may be extremely uncomfortable to patients who are awake, can cause subcutaneous vasoconstriction, preventing the transfer of heat via conduction. Ice water also increases shivering, which in turn increases internal heat production. Other reasons for the recent criticisms include difficulty monitoring and resuscitating patients.
- Recently, evaporative techniques have been touted to be as effective as immersion techniques without the practical difficulties. However, data on the efficacy of this method are limited. Evaporative body heat loss may be accomplished by removing all of the patient's clothes and intermittently spraying the patient's body with warm water while a powerful fan blows across the body, allowing the heat to evaporate.
- A number of other cooling techniques have been suggested, but none has proven superior to or equal to cold-water immersion or evaporative techniques. These include peritoneal, thoracic, rectal, and gastric lavage with ice water; cold intravenous fluids; cold humidified oxygen; cooling blankets; and wet towels.
- In the most severe cases, cardiopulmonary bypass has been suggested, but this requires highly trained personnel and sophisticated equipment.
- Antipyretics (eg, acetaminophen, aspirin, other nonsteroidal anti-inflammatory agents) have no role in the treatment of heatstroke because antipyretics interrupt the change in the hypothalamic set point caused by pyrogens. They are not expected to work on a healthy hypothalamus that has been overloaded, as in the case of heatstroke. In this situation, antipyretics actually may be harmful in patients who develop hepatic, hematologic, and renal complications because they may aggravate bleeding tendencies.
- Dantrolene has been studied as a possible pharmacological option in the treatment of hyperthermia and heatstroke, but at present, it has not been proven to be efficacious in clinical trials.
Along with immediate active cooling, steps to stop excessive production of heat must be taken.
- Agitation and shivering should be treated immediately with benzodiazepines.
- Benzodiazepines are the sedatives of choice in patients with sympathomimetic-induced delirium as well as alcohol and sedative drug withdrawals.
- Neuroleptics, such as chlorpromazine, which were the mainstays of therapy in the past, are best avoided because of their deleterious adverse effects, including lowering of the seizure threshold, interference with thermoregulation, anticholinergic properties, hypotension, hepatotoxicity, and other adverse effects.
Similarly, convulsions must be controlled: BENZODIAZEPINES OR INTUBATION
OTHER CONSIDERATIONS: RHABDOMYOLYSIS, MUSCLE NECROSIS, HEPATIC DAMAGE, DIC, PULMONARY EDEMA, ARF
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