Hypovolemia and dehydration in the oncology patient.

Dehydration is commonly but often inappropriately diagnosed in cancer patients. Dehydration is the loss of water from the intracellular compartment due to hypernatremia. Dehydration can occur among patients who are hypervolemic, euvolemic, or hypovolemic. Cancer patients are more often hypovolemic, reflecting depletion of water from the extracellular space due to excessive loss, such as from vomiting and diarrhea, or inadequate intake of fluids. Hypovolemia can be hypernatremic, eunatremic, or hyponatremic. The appropriate state of the patient should be determined prior to attempts at correcting the problem. A hyponatremic patient would rehydrate more quickly with a solution higher in sodium, whereas this solution could be dangerous for a hypernatremic patient. Rapid or inappropriate treatment of hypernatremia can lead to death. Subjective findings, physical findings, and laboratory values will help direct the appropriate resuscitation methods. This paper reviews the physiologic control of extracellular volume and electrolytes, diagnosis of sodium and water balance problems, and the management of these concerns.