To the Editor:
Heat stroke is a life-threatening illness with the hallmark presentation of core body temperature greater than 40°C and altered level of consciousness. Mortality has been reported to be as high as 50%, 1 and the illness is often misdiagnosed in the Emergency Department (ED). 2 It has come to our attention after treating a recent heat stroke case in our ED that there may be similar potential for misdiagnosis by prehospital providers and missed opportunities to deliver early treatment in the prehospital setting.
An advanced life support unit in our command system staffed by 1 paramedic and 1 emergency medical technician-basic was dispatched for an unresponsive subject lying outdoors near a bus stop parking area. Weather conditions at the time of dispatch were reported by the National Weather Service to be 30.6°C, dew point of 16.1°C, and humidity of 41%. No care had been rendered before emergency medical service (EMS) arrival. Upon arrival, a 61-year-old woman was found breathing but unresponsive to deep sternal rub. In spite of the heat, the patient was wearing a denim jacket and black canvas pants. The crew documented the patient to have a Glasgow Coma Score of 3 and hot, dry skin. Her heart rate was 120 beats per minute, blood pressure was 136/90 mm Hg, respiratory rate was documented at 12 breaths per minute, and Sa
The patient arrived at the ED 38 minutes after the initial dispatch. The attending physician noted the patient to be moving upper extremities bilaterally but would not follow commands or open eyes spontaneously. During the transfer from the ambulance cot to the bed, the attending physician noted the skin was hot and dry to touch. A rectal temperature was obtained in the ED (46 minutes after dispatch) and reported to be 43.2°C. The heart rate was 125 beats per minute, and the respiratory rate was 32 breaths per minute. The pupils were 4 mm and reacted sluggishly. The remainder of the physical examination was unremarkable. An additional intravenous line was placed, and the patient was given a rapid infusion of cold normal saline (51 minutes after dispatch). The patient was administered etomidate and rocuronium to facilitate endotracheal intubation and subsequently given propofol for sedation. After intubation (1 hour after dispatch), ice packs were placed on the axilla, groin, and neck to supplement cooling. A femoral venous line was placed, and an esophageal probe was inserted for continuous temperature monitoring. These measures reduced the core temperature to 39.0°C. At 1 hour, 46 minutes after dispatch, a cooling blanket was applied.
Four hours after dispatch, the patient followed commands. She was subsequently extubated without event. Peak creatine phosphokinase was 2348 IU/L on hospital day 2. Her hospital course was complicated by a right lower lobe aspiration pneumonia, but she was transferred out of the intensive care unit on hospital day 3 and had an uneventful recovery, with discharge to home on hospital day 9.
We are concerned about the lack of early cooling therapy for this patient, and we believe that this case presents a number of important teaching points for EMS providers, medical directors, and emergency physicians. The EMS crew failed to recognize the heat stroke in spite of documenting classic signs and symptoms in the patient care report. That failure may be due to a relative rarity of clinical heat illness in the prehospital setting. Outside of certain regions or venues that are enriched for heat illness, such as a sporting event, individual EMS providers may not regularly encounter patients with heat illness. This insufficient frequency of exposure may not be enough to provide immediate recognition when compared with other potential mimics associated with altered level of consciousness (eg, drug overdose, hypoglycemia). Many EMS providers deliver care independent of medical control by following treatment algorithms. These algorithms are typically linear, so entering the wrong path may take the provider farther from a correct diagnosis. While the “adult altered level of consciousness” algorithm does caution the provider to consider other conditions, measurement of body temperature is not mentioned in the algorithm.
It is difficult for EMS providers to accurately measure body core temperature with commonly available thermometers (eg, oral, tympanic, temporal artery). 3 Although a tympanic thermometer was available, the EMS providers did not document the temperature in the patient care report even after hot skin was noted. Therefore, it may be advisable for EMS providers, especially those operating in remote areas, to carry equipment to measure rectal temperature in subsets of patients who may be at high risk for environmental illness.
We have previously suggested the application of cold saline infusion to treat heat illness after laboratory studies of healthy volunteers. This case demonstrates the potential utility of cold saline for treatment of heat stroke. 4 Although multimodal cooling was deployed in the ED for this patient, the treating clinicians reported an observable drop in core body temperature coincident with the cold saline infusion. The EMS providers in our area carry cold saline for induction of therapeutic hypothermia after resuscitation from cardiac arrest. While not explicitly part of the heat illness protocol in our state, the command physician could have ordered its administration if suspicion of heat stroke had been communicated. The failure to recognize heat stroke prevented early application of appropriate therapy. Although this patient survived without long-term issues, it is commonly recommended that cooling be initiated as early as possible to minimize the potential for seizures and subsequent multiple organ dysfunction syndrome. 5
In summary, we encourage medical directors and EMS physicians to consider the value of making rectal thermometry part of the prehospital “unconscious/unknown” protocol and differential diagnosis. Additionally, rapid infusion of cold normal saline already carried by many EMS providers may correct severe hyperthermia in the ED and prehospital setting.