1. Causes of hyponatremia with the overall decrease in sodium: sodium lost in such cases is greater than water loss, in the outer renal sodium loss and loss of renal sodium. Ranked according to urine can be the difference between sodium and urine sodium concentration [Na +]> 20mmol / L for an increase in renal sodium loss; <20mmol / L for the loss of renal outside.
1) Causes of sodium loss from renal: The excessive use of diuretics. The lack of mineralocorticoid to reduce renal tubular sodium reabsorption. Nephritis accompanied by loss of salt, renal tubular acidosis and metabolic alkalosis. Urine ketone, etc. (including diabetic ketoacidosis, hunger, alcohol and ketones in urine).
2) Causes of extrarenal sodium loss: The loss of the gastrointestinal tract, such as vomiting, diarrhea, the third body fluid retention lacunar, burns, pancreatitis and pancreatic fistula and biliary fistula, etc.
2. Cause of hyponatremia with normal overall sodium:
1) the lack of glucocorticoid: on the one hand, so that obstacles to happen renal water excretion, in the absence of blood volume reduction in the case of the release of ADH may also be an increase in (non-osmotic release of ADH); on the other hand, the occurrence of renal hemodynamics obstacles at ADH release is not increasing, can increase the permeability of collecting duct.
2) hypothyroidism: Yes because of cardiac output and glomerular filtration rate, leading to ADH for intrarenal mechanisms mediated disorder happened.
3) acute schizophrenic patients, its mechanism are many factors, including a sense of increased thirst (polydipsia), ADH release defects mild osmotic regulation in the case of low plasma osmotic pressure also has ADH release, renal response to ADH increase and antipsychotics; surgery is a kind of stress, patients hyponatremia can occur, which is characterized by increased plasma ADH levels and renal free water to remain in the body increased, patients Enter no more than the liquid electrolyte is also a factor.
4) drug-induced hyponatremia: the mechanism is for the ADH-mediated, or increased ADH release, or to enhance the role of ADH. Drugs: antipsychotics, such as flexidine, including sertraline, on behalf of tons of fertile thiothixene, haloperidol, amitripine; and amphetamine-related drug ecstasy; certain anti-cancer drugs, such as vinblastine, vincristine, high-dose cyclophosphamide, carbamazepine bromocriptine, chlorpromazine, intravenous vasopressin andlorcainide. These patients is to increase the overall volume and urine sodium concentration [Na +] regular> 20mmol / L.
3. Cause of hyponatremia that the overall increase in sodium: sick of this type of hyponatremia despite the overall increase in sodium, but because there is water retention in vivo, it reduced sodium. Common due to: Acute or chronic renal failure, nephrotic syndrome, hepatocirrhosis and heart failure. At heart, the cardiac output reduced mean arterial pressure decreased, leading to non-osmotic release of ADH increased, reduced sodium; heart failure at the same time there is renin - angiotensin - aldosterone system activation and increased catecholamine release, so that further aggravate hyponatremia. Patients with nephrotic syndrome because of reduced effective blood volume, can cause non-osmotic release of ADH to increase water reabsorption, resulting in hyponatremia. In chronic renal failure, are often components of renal sodium excretion to increase, coupled with impaired renal drainage, especially when the intake of water exceeded the drainage capacity kidney more susceptible to hyponatremia, such as excessive sodium intake at the same time the trigger edema.