Terminated due to protocol amendment: intervention window changed from entire ED stay to first 2h after ED admission. Revised protocol will be registered separately.

The goal of this clinical trial is to compare the effect of high chlorine solution such as normal saline and non-high chlorine solution such as sodium lactate ringer's solution on renal function in patients with heat stroke. The main question it aims to answer is whether limiting the amount of normal saline infusion during emergency department can lower the incidence of acute kidney injury and mortality in patients with heat stroke.

Participants will receive a free normal saline infusion during the emergency department according to the study design, or a restricted normal saline infusion while using sodium lactate Ringer's instead.

Researchers will compare the normal saline infusion group and sodium lactate Ringer's group to see if limiting the amount of normal saline infusion during emergency department can lower the incidence of acute kidney injury and mortality in patients with heat stroke.

Inclusion Criteria:

• ≥ 18 years
• diagnosed as heat stroke
• Informed consent from patients or family members.

Exclusion Criteria:

• need immediate cardiopulmonary resuscitation
• transferred from another hospital
• with original end-stage renal disease or dialysis
• with severe organ damage
• pregnant women