A physiological analysis of hyponatremia: implications for patients on peritoneal dialysis.
The basis for hyponatremia is a negative balance for sodium (Na+) plus potassium (K+) and/or a positive balance for water. In patients with normal renal function, vasopressin is needed to prevent the excretion of electrolyte-free water. Vasopressin is not important when there is little residual renal function. If hyponatremia is accompanied by a quantitatively appropriate gain in weight, this implies that a gain of electrolyte-free water was the basis for hyponatremia. In the absence of this weight gain, a loss of salts is to be suspected. If the extracellular fluid (ECF) volume is obviously low, hyponatremia is due to a deficit of NaCl, unless there is a deficit of K+. With a KCl deficit and a contracted ECF volume, there should also be a large shift of Na+ into cells, so metabolic alkalosis would not be an expected finding. In contrast, those patients with no change in weight who have a normal or expanded ECF volume are subdivided into those with a gain of solutes restricted to the ECF compartment (glucose, mannitol), or those with a deficit of solutes of intracellular fluid origin, which implies that a catabolic state (malnutrition) may be present.
Cherney
D Z
DZ
Zevallos
G
G
Oreopoulos
D
D
Halperin
M L
ML
D005110:Extracellular Space / Q000378:metabolism; D006801:Humans; D007010:Hyponatremia / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology*; D010530:Peritoneal Dialysis; D010531:Peritoneal Dialysis, Continuous Ambulatory; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D015430:Weight Gain
D012964:Sodium; D011188:Potassium