The principles of rehydration are as follows: fast first, then slow, salt first, then sugar, crystal first, then gel, potassium when seen in urine, and alkali when appropriate. Shock is the syndrome of the body due to various pathogenic factors caused by the imbalance of neurohumoral factors and acute microcirculatory disorders, resulting in insufficient blood perfusion in tissues and organs, cell damage and organ malfunction. The principle of rehydration in shock is generally first rapid input of crystalloid fluid such as saline, balanced salt solution, glucose solution to increase the amount of cardiac blood return and cardiac output, followed by infusion of colloid, whole blood, plasma, albumin, etc. to reduce the leakage of crystalloid blood into the extravascular third gap.