The principle of rehydration for hypertonic dehydration is to remove the cause of the disease so that the patient no longer loses fluid, and to replace the fluid that has been lost, orally as much as possible if it can be taken orally, and intravenous infusion of 5% glucose sugar or hypotonic saline solution can be considered if it cannot be taken orally. When rehydrating, it should be noted that although the blood sodium is higher, the total sodium in the body is actually still decreasing due to dehydrated blood concentration. Proper sodium supplementation should be given along with rehydration to correct sodium deficiency in the body. In patients with diabetes combined with hyperosmolar coma, the cause must be removed and the blood sugar should be brought down as soon as possible in addition to rehydration. Because many diabetic patients are elderly, their cardiopulmonary function is often not very good. It is important to monitor the patient’s central venous pressure while rehydrating, to prevent rehydration from being too fast, which can cause heart failure.