Hypothermia after Cooling Therapy in Exertional Heat Stroke : A Case Study

Since the beginning of the 21st century, global temperatures have risen and are predicted to rise even higher.1 Heat reduces worker’s productivity and affects body thermoregulation and homeostasis. The hypothalamic thermoregulatory center and peripheral heat receptors are activated when body temperature reaches 37oC.2,3 Inadequate body response causes inflammation in heat-related illness which occurs as a spectrum from heat edema, heat cramp, heat syncope, heat exhaustion to heat stroke.4-7 Clinical outcome depends on environmental conditions, physical activities and individual biological factors. The environmental component includes climate, geographic and socio-economic factors. Individuals who are motivated and perhaps fear losing their job might do strenuous physical activities beyond their heat tolerance.3,8 Physical exertion produces more heat while protective clothing and equipment may worsen the condition.9 Moreover, medical or mental conditions, youth, aging, pregnancy, taking drugs or some medications, history of previous heat illness and heat acclimatization may influence the variation of heat response.7,10,11


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removing the patient out of the heat and rapid cooling should be managed.10A target temperature near 38ºC for evaporative cooling and 39ºC for immersion cooling were seen in the majority of studies.15Hypothermia from overcooling may lead to life-threatening cardiac arrhythmia. 15When rewarming a patient with high-grade hypothermia, core temperature afterdrop can be one of its complications. 16It is described as further drop of core body temperature after removing the patient from a cold environment. 17This case demonstrated an EHS patient with iatrogenic hypothermia, which should be of concern in both emergency and delivery medical care.Furthermore, core temperature afterdrop was also observed during management of his hypothermia.

Case report
A 33-year-old male ranger was admitted to a 90-bed district hospital with unconsciousness and general tonic-clonic seizure.He had been fatigued and nauseated during his first few days of an advanced military training course.He felt too unwell to take food or drink during the strenuous training.At the district hospital, his medical record showed axillary temperature of 42ºC, blood pressure of 60/40 mmHg, and pulse rate at 160 beats per minute.Endotracheal intubation, volume resuscitation with 2 liters of room temperature normal saline, Foley's catheter and continuous inotrope (epinephrine) were provided.The seizure was controlled with medications (diazepam and phenytoin).Intravenous glucose was also given due to hypoglycemia of 59 mg/dL.He was then referred to a tertiary hospital.Documentation showed that his axillary temperature was 34.2ºC when leaving the district hospital.During 1-hour transportation, he was laid down on a plastic sheet, surrounded with ice cubes and water without core temperature monitoring.
At an emergency room of a tertiary hospital, his blood pressure was 110/60 mmHg.Glasgow Coma Score was E1VTM1.Ten minutes later, he was transferred to an intensive care unit (ICU) where his esophageal temperature measurement was 29ºC.Heat stroke with iatrogenic hypothermia and hypovolemic shock was diagnosed.Medical electric blanket was applied to keep temperature above 36ºC.His lowest temperature during rewarming was 28ºC. Figure 1 shows his body temperature.During the first two days, his core temperature and central blood pressure were measured.Initial electrocardiogram (EKG) showed junctional rhythm with J wave between QRS complex and ST segment (Osborn wave).Continuous monitoring of cardiac wave showed no adverse event and the wave became regular sinus rhythm after rewarming.No evidence of intracranial hemorrhage, recent infarction or herniation in brain tomography.Table 1 demonstrates his laboratory findings during treatment.On the first day, the investigations showed metabolic acidosis with respiratory alkalosis, hypokalemia, hypophosphatemia, rhabdomyolysis, pre-renal azotemia, and elevated liver transaminases.Intravenous fluid was administered and electrolyte imbalance was corrected.He gained consciousness with stable vital signs on the second day of admission.The inotrope was discontinued and extubation was performed.
Hyperthermia, thrombocytopenia with normal fibrinogen level developed on day 2. Empirical antibiotic (ceftriaxone) was given.Septic workup showed a positive hemoculture for Enterococcus faecalis.Neurological deficit was assessed on day 6.Only weakness of right nasolabial fold remained without swallowing difficulty.Cerebellar signs were intact.Thai Mental State Examination (MSE) was normal (score 25/30).He was sent to a community hospital in his hometown to complete the treatment for infection.

4C 4D Discussion
This young and healthy man with hyperthermia and loss of consciousness after extreme outdoor training is a typical presentation of EHS. 3 He was experiencing severe dehydration that led to hypovolemic shock and hyponatremia.Environmental and physical predisposing factors in the case were advanced military training, tropical ambient environment, thick grey outfits and inadequate rehydration.One to two liters of sweat per hour or 15 liters per day could be lost during strenuous training. 2,3Dehydration burdens the heart, increases work of sodium-potassium adenosine pump in cellular metabolism and lowers the heat transport. 3,18Heat distribution to capillary network of skin is served by splanchnic vasoconstriction and cutaneous vasodilatation. 2,3Heat destroys megakaryocyte and decreases platelet levels.Splanchnic hypoperfusion and ischemia from heat injury usually present with nausea and vomiting. 18Permeability of intestinal mucosa increases after heat damage. 2Translocation of gastrointestinal bacteria and endotoxin to systemic circulation led to E. faecalis septicemia and systemic inflammatory response syndrome (SIR). 3Elevation of hepatic aminotransferases demonstrates typical hepatic injury in heatstroke. 18This impairs gluconeogenesis and induces hypoglycemia. 18Abnormal CPK and creatinine from rhabdomyolysis and acute renal failure are mainly found in EHS rather than CHS. 18Amphetamine did not involve the rhabdomyolysis in this case.Rhabdomyolysis usually presents with hyperkalemia and hyperphosphatemia.However, a report showed 8 out of 24 military heat injury cases with rhabdomyolysis had hypokalemia. 19Hypophosphatemia can be associated with severe heat exhaustion. 20Metabolic acidosis and respiratory alkalosis were found in heat injury. 19Alkalinisation may increase activity of pH-sensitive phosphofructokinase which enhances cellular uptake of phosphorous. 21mperature was not measured on arrival at the emergency department of the tertiary hospital because oral temperature is not accurately correlated to core temperature. 22Instead, esophageal temperature probe was placed in the ICU.This patient encountered both hyperthermia and hypothermia.Most studies successfully used temperature below 39ºC for termination of ice immersion in heat injury to avoid hypothermia. 13,15,23The patient's axillary temperature before leaving the first hospital was already under the usual target temperature.Cooling with 2ºC water cooling can reduce core body temperature by 0.35ºC per minute. 24Using this method during long distance transportation caused hypothermia.
Hypothermia in this patient was moderately severe (mild = 32.2-35.1ºC, moderate = 28.1-32.1ºC,severe = less than 28.1ºC ). 16sborn wave in the EKG is a diagnostic pattern when body temperature reaches below 32ºC. 25Risk of atrial fibrillation and cardiac arrest is increased. 16,25Rewarming is indicated in this case.25 His temperature shows core temperature afterdrop from 29 ºC to 28ºC in the first hour of rewarming.This phenomenon occurs from convection and conduction heat loss from increased blood flow form core to peripheral region during rewarming. 17t disappears after the balancing of core and peripheral temperature. 25A case has been reported with no complication after termination of cooling. 26ngpant S, et al.

Hypothermia after Cooling Therapy in Exertional Heat Stroke: A case study
Neurological deficit after treatment was mild in this case.Recently, successful therapeutic hypothermia of 33ºC in non-response heat stroke patients has been reported. 27,28eurological benefit after therapeutic hypothermia has also been shown in cardiac arrest patients. 29No exact mechanism may describe the weakness of right nasolabial area.A study showed that incidence of Bell's palsy in the American army was significantly higher in waterless regions. 30ncern with risk factors, early detection, cooling methods, management pitfalls and return to duty program are essential in primary, secondary and tertiary prevention of exertional heat injury (EHI). 24,31 his patient should have 2 weeks of work restriction, at least 1 month of physical training and at least 1 month of gradual acclimatization. 31However, return to the military training is not possible in this case.His work plan was uncertain.Brief advice was given for return to work plan.Evaluation tests on heat tolerance would be recommended if he continued his military service. 8,31,32cupational EHS is preventable.Workplaces with heat sources should measure and assess occupational heat stress.Health and safety controls can reduce modifiable risk factors in metabolic heat production and heat exchange. 32Air ventilation, insulation and air conditioning equipment can be used in engineering control. 32Administrative control may include work/rest schedules and acclimatization. 32Medical monitoring programs before and during employment should be established. 32Health and safety training for workers should aim to teach effective self-preparedness such as proper rehydration and early recognition of symptoms. 32Supervisors should be able to monitor weather warnings. 32Workplace heat alert programs are recommended for emergency preparedness. 32

Conclusion
This case report demonstrates the EHS patient with multiple organ dysfunction and overcorrection of core body temperature.Continuous application ice cubes and water while transfer for prolonged period of more than 1 hour has put the patient at risk of hypothermia.The typical Osborn wave in the EKG was also reported.To prevent the sequelae of hypothermia, we recommended that the patient' core temperature during cooling method should be monitored closely not only in the hospital but also in the transfer vehicle.It is of note that the transfer of EHS patients from one medical facility to another should become a national issue for emergency medical service, especially in the vicinity of military camps.
In conclusion, preparedness and training for emergency response, safety during transfer are necessary for both high risk workplaces and the medical settings in charge in order to prevent and control of heat stroke and its fatal consequences.

Figure 1 :
Figure 1: Fluctuation of temperature in this case.
Hypothermia after Cooling Therapy in Exertional Heat Stroke: A case study

Table 1 :
Laboratory data of the patientA