A group of emergency medicine doctors in Japan has updated a set of treatment guidelines for heatstroke, adding a ¡°most severe¡± category to the scale for the seriousness of the condition.

The move is meant to stress the need for urgent medical attention in severe cases as the number of heatstroke cases soars amid record-high temperatures, which are at least partially attributable to climate change.

The treatment guidelines are written primarily for front-line health care workers but are sometimes referred to by school officials and sports instructors.

The previous guidelines, set out by the Japanese Association for Acute Medicine in 2015, classified heat-related illnesses into three categories: Grade I, which involves dizziness; Grade II, which comes with a headache and vomiting; and Grade III, which is for patients with impaired consciousness.

The new Grade IV is defined as cases where patients have a core body temperature of 40 degrees Celsius or higher and their consciousness is seriously impaired.

If a patient is considered to be suffering from Grade III or Grade IV heatstroke, the doctors are recommended to administer ¡°active cooling.¡±

Active cooling can be performed in many ways, including through the use of ice packs, placing the patient into a pool of cold water, spraying water over the body surface to accelerate evaporative cooling, and inserting catheters in veins to control temperature through blood vessels.

The guidelines stress the need to standardize medical care for the most severe patients.

The association¡¯s survey of heatstroke patients nationwide between 2020 and 2023 found that in severe cases involving a body surface temperature of 40 C or higher, 25% didn¡¯t have their core body temperature ¡ª the temperature of internal organs ¡ª measured. The active cooling rate among such cases was about 64%, and their in-hospital mortality rate was 37%.

In cases where the patient¡¯s core body temperature was measured and was also found to be 40 C or higher, the active cooling rate stood at 91%, and their in-hospital mortality rate was lower, at 21%.

Extreme heat has resulted in a surge in ambulance calls in recent years. Last year, a total of 91,467 people called ambulances after suffering heatstroke, and each year over 1,000 people now die from the illness.

The number of heatstroke patients spikes after the rainy season ends in mid-July. In the week through Sunday, the number of ambulance calls over heat-related symptoms shot up to 12,666, rising from 9,078 from the week before.