Targeted temperature management (TTM) is a technique developed to precisely regulate a patient’s core temperature (1). TTM has been extensively documented to reduce brain inflammation, neuronal cell death, and activation of harmful cellular processes (2). The therapeutic modality is considered a firstline treatment for improving neurological outcomes in post-cardiac arrest and traumatic brain injury and is applicable to cases of myocardial infarction and neonatal hypoxic-ischemic encephalopathy (2-6).

Heat stroke is characterized by a core temperature exceeding 40 °C and is accompanied by central nervous system dysfunction, musculoskeletal abnormalities, or multiorgan failure (7,8). Exertional heat stroke occurs when an external heat source considerably elevates the patient’s temperature. Compared to adults, children and adolescents are more vulnerable due to their higher metabolic rates, lower sweat production, and reduced ability to dissipate heat, particularly during vigorous physical activity under hot and humid conditions (9,10). In Korea, the incidence of heat-related illnesses correlates with the average maximum daily temperature (11). Based on the statistical data compiled from the annual reports by the Korea Disease Control and Prevention Agency from 2020 to 2023, an average of 1,709 cases of heat-related illnesses were reported annually to emergency departments during this period. In 2023, there were 2,818 reported cases, including 32 fatalities. Child and adolescent cases and proportion to total cases of heat-related illnesses increased from 24 (2.2%) in 2020 to 111 (3.9%) in 2023 (11).

Immediate cooling and maintenance of normal temperature are critical for managing heat stroke and significantly affect outcomes (12,13). Traditional cooling methods include evaporative cooling, water blankets, and administration of cold intravenous fluids (14,15). Given the precision and rapidity with which TTM can achieve target temperatures, its application in adult heat stroke management was reported (16).

A previously healthy 14-year-old girl presented to the emergency department after collapsing during a midday run in July 2023, when the daytime ambient temperature reached 35 °C. The girl was not on medication at that time. Her initial vital signs were as follows: blood pressure, 78/56 mmHg; pulse rate, 180 beats/minute; respiratory rate, 38 breaths/minute; temperature, 40.5 °C; and oxygen saturation, 99% on room air. Her skin was wet. There were no physical examination findings of trauma, such as bruises. Her Glasgow Coma Scale score was 9 (eye opening, 2; verbal response, 2; and motor response, 5). Initial laboratory findings indicated compensated metabolic acidosis, acute kidney injury, and mild myocardial injury (Table 1). Brain computed tomography showed no specific lesions. At this point, we made a diagnosis of exertional heat stroke given her absence of underlying medical conditions, collapse during exercise, and lack of clinical clues suggestive of central nervous system infection or poisoning.

As a part of the initial management, 1 L of 0.9% saline was administered over 1 hour. TTM was applied on day 1 to achieve a more consistent and precise reduction in core temperature to a target of 36 °C, compared to the traditional evaporative cooling. TTM was induced using the Artic SunTM (Medivance, Inc.), targeting at a lowering rate of 0.5 °C/hour to minimize shivering. The core temperature was monitored using an esophageal catheter temperature probe. Remifentanil and midazolam were administered for sedation and shivering, respectively. On day 2, the girl regained consciousness but remained drowsy and confused. Her cardiovascular status improved with hydration and appropriate temperature control. Her systolic blood pressure and heart rate stabilized around 110 mmHg and 80 beats/minute, respectively. There were no signs of cardiomegaly or congestive heart failure. On day 3, as she had fully regained consciousness and her vital signs were stable, TTM was discontinued. Brain magnetic resonance imaging on day 5 showed normal findings. During the application of TTM, her respiratory function remained stable, with oxygen saturation above 98% in room air despite extensive hydration, and there was no pleural effusion.

Creatine kinase concentrations showed a bimodal peak on days 2 and 7, without muscle pain (Fig. 1). Blood urea nitrogen and creatinine concentrations peaked at 52.4 mg/dL on day 1 and 3.4 mg/dL on day 3, respectively (Fig. 2). Without a dialysis, urine output was adequate throughout the hospital stay. She was discharged on day 10 with normalized consciousness and with all laboratory values within normal ranges. She was advised to refrain from strenuous activities and limit herself to light daily activities. At a 1-month follow-up visit, all laboratory values remained within normal ranges, and she was cleared to resume physical activities.

Two options are available for pediatric application of TTM: 1) maintaining hypothermia at 32-34 °C for the first 2 days followed by normal temperature, or 2) maintaining normal temperature at 36-37.5 °C for 5 days (17,18). In the setting of post-cardiac arrest care, there is still an ongoing debate over whether hypothermia offers more benefits than normothermia does (17,18). However, to our knowledge, there have been neither reports on the application of TTM to pediatric heat stroke, nor any studies indicating whether hypothermia provides benefits. One adult case report detailed the 3 patients with heat stroke (age, 21-73 years) who were treated successfully using therapeutic hypothermia (< 36 ° C) during 24-36 hours (16). Of the 3 patients, only 1 who was aged 73 years was discharged with a cerebral performance categories scale of 3 (16). In our case, we used a normothermic protocol that resulted in recovery without neurological sequelae. The girl regained clear consciousness on day 3, and subsequently, showed no neurological deficits on magnetic resonance imaging. This report may serve as evidence that in the treatment of pediatric heat stroke, normothermia without hypothermia may be sufficient to achieve recovery without neurological sequelae.

The bimodal or trimodal phase of rhabdomyolysis has been reported in previous studies; some have attributed it to enzyme deficiencies or genetic metabolic issues, while others have attributed it to the early resumption of physical activity without underlying diseases (19,20). This current case exhibited a bimodal pattern without underlying conditions or early resumption of physical activity, suggesting another mechanism for the bimodal peak in rhabdomyolysis. In a case of a 12-year-old Korean boy with heat exhaustion-related rhabdomyolysis, its third attack occurred 2 months after the initial event (20). However, in our case, the girl was followed up only 1 month after discharge and failed to attend follow-ups thereafter, leaving the occurrence of the third attack undetermined.

In conclusion, with the impact of global warming, the importance of emergency management for heat stroke in Korea is increasing. In this context, this case suggests a potential efficacy of normothermic TTM in pediatric heat stroke.