Management of Neurosurgical Patients with Hyponatremia and Natriuresis

Abstract

The main objective of our study was to evolve a practical management protocol for neurosurgical patients with hyponatremia and natriuresis, based on their blood volume status and hematocrit. Twenty-one patients with hyponatremia and natriuresis and 3 control patients were studied. Patients with hyponatremia were categorized on the basis of their hematocrit, central venous pressure, and total blood volume. Group A consisted of patients with hypovolemia and anemia (16 patients); Group B patients had hypovolemia but no anemia (5 patients); Group C included those with hypervolemia (0 patients). Patients in Groups A and B received isotonic saline (> 50 ml/kg/d) and oral salt (12 g/d). Additionally, those in Group A were transfused with 500 ml of whole blood. The end points in the study were 72 hours after entry or two consecutive serum sodium values of > 130 mEq/L, whichever was earlier. Hyponatremia was corrected in all the patients within 72 hours (1 patient, < 24 h; 13 patients, < 48 h; and 7 patients, < 72 h). We conclude that most neurosurgical patients with hyponatremia and natriuresis have hypovolemia, with or without anemia. Fluid and salt replacement and a blood transfusion rather than fluid restriction often results in the correction of the hyponatremia. Our findings offer indirect evidence to support the hypothesis that in most of these patients, hyponatremia is caused by cerebral salt wasting syndrome, rather than the syndrome of inappropriate secretion of antidiuretic hormone.

Syndromes related to sodium and arginine vasopressin alterations in post-operative neurosurgery

“…the incidence of csWs among all the patients was greater than that of sIADH, which is in agreement with reports from various other authors, who also observed a greater prevalence of csWs, compared to sIADH in neurological patients 1,2,4,5,10,18,30 . the coexistence of DI and csWs (mixed syndrome) observed in our patients has also been described by yamaki et al 17 , who studied two patients postoperatively following surgery for pituitary tumor and observed the presence of severe natriuresis and hyponatremia in a study patient who developed DI (fluid loss >2.36 ml/kg/h), which led the authors to conclude that hyponatremia resulting from csWs in intracranial diseases may develop in patients with DI.…”

“…Alterations in sodium are frequently found in neurological and neurosurgical patients [1][2][3][4][5][6][7] and are associated with alterations in the osmolarity of the extracellular medium and changes in the volume of the cells of the central nervous system (cNs). they may aggravate the condition of these patients 8 .…”

“…At the present time, csWs has again been proposed as a cause of hyponatremia associated with neurological disease. the majority of patients diagnosed with sIADH are hypovolemic and, when treated with fluid restriction, may develop a stroke with consequent worsening of their neurological condition 18 , suggesting that csWs may be the most probable cause of hyponatremia in these patients 1,2,4,5,7,16,19 . other studies suggest that hyponatremia may be iatrogenic, secondary to the excessive administration of hypotonic liquids 20 .…”

“…However, they differ with respect to volemic states since sIADH is associated with normovolemia or hypervolemia, whereas csWs is associated with fluid depletion 2,4,5,7 . Although sIADH is characterized by fluid retention, the majority of patients show no signs of hypervolemia since onethird of the remaining fluid is maintained in the extracellular compartment, making diagnosis difficult 8 .…”

“…Measurement of AVP can be useful in the differential diagnosis of these syndromes 2,7 . However, it can also be influenced by several factors involved in the postoperative phase of neurosurgical patients, that are able to stimulate the non-osmotic secretion of AVP, such as stress, an increase in intracranial pressure (IcP), pain, use of medication (antipsychotics, tricyclic antidepressives, carbamazepine, morphine, anesthetics, metoclopramide), hypovolemia, prolonged recumbency and positive-pressure mechanical ventilation 4,7,16,[22][23][24][25][26][27] . considering that patients submitted to neurosurgery may frequently suffer sodium and AVP alterations of various causes and since differential diagnosis of these alterations is essential to guarantee adequate treatment, their accurate diagnosis is of great importance 17,18 .…”