Hyponatremia is classified into four degrees according to the Wattad criteria: mild ≥ 125 mmol/L, moderate ≥ 120 mmol/L, severe ≥ 110 mmol/L, and extreme < 110 mmol/L. In addition to treating the primary disease, the principle of combining water restriction, sodium supplementation, and dehydration should be used? Mild hyponatremia can be corrected by strict water restriction. When blood sodium is <120mmol/L, 3% hypertonic saline can be used to rapidly relieve the hypotonic state of body fluids and raise the blood sodium concentration to 120-125mmol/L. 12% hypertonic saline 12ml/kg raises blood sodium by 10mmol/L and is supplemented in 2-3 times, and blood sodium is rechecked to guide treatment. If a larger amount of hypertonic saline or 5% sodium bicarbonate is used for rapid intravenous drip or push, it is bound to greatly increase the possibility of osmotic demyelination syndrome and should be noted. The best way to calculate the total amount of sodium needed on the first day is to calculate it according to the formula. The best way is to calculate the total amount of sodium needed on the first day according to the formula and then pump it continuously for 24 hours with a syringe pump. This way it is not affected by the concentration. And it is more reliable and safe! Clinical data indicate that chronic hyponatremia is prone to central pontine myelinolysis (CPM) when corrected too quickly, especially when the blood sodium is too high after correction. In addition to the central pontocerebrum, similar pathological changes can occur at the junction of the gray and white matter of the brain, the pathogenesis of which is unknown. It is generally believed that a rapid rise in blood sodium can cause an increase in cerebrovascular endothelial cell permeability and impaired blood-brain barrier function, leading to brain edema and demyelinating changes. Experimentally, it has been proved that after hyponatremia is rapidly corrected by hypertonic saline, demyelinating changes can occur in the brainstem, thalamus, striatum, cerebellum, hippocampal gyrus, anterior association and white matter of cerebral hemispheres. Prevention: Attention should be paid to the rate of correction of hyponatremia to prevent the occurrence of central pontine myelinolysis (CPM). It is safe to raise the blood sodium value not more than 12 mmol/L per day, and to correct it at a rate of 2 mmol/L per hour to the level of 120-130 mmol/L.