The rehydration test is an important test in the emergency treatment of shock, usually 250ml of isotonic saline is taken and administered intravenously over 5-10 minutes, and the changes in blood pressure and central venous pressure are observed to determine the body’s blood volume and the condition of cardiac function. First, if the blood pressure increases, but the central venous pressure remains unchanged, this suggests that there is insufficient blood volume, usually caused by hypovolemic shock, injury shock, infectious shock. Second, if the blood pressure is unchanged, but the central venous pressure is elevated, it usually indicates cardiac insufficiency, which is most likely caused by cardiogenic shock, distributive shock, obstructive shock, and common hemorrhagic shock and traumatic shock can also cause clinical symptoms of cardiac insufficiency.