Hyponatremia frequently complicates the care of neurosurgical patients and requires prompt effective
therapy. These patients commonly fulfill the laboratory criteria of the syndrome of inappropriate secretion of
antidiuretic hormone (
SIADH) or cerebral
salt wasting; the classification depends on the volume status of the patient. The authors have been dissatisfied with the standard
therapy of fluid restriction for the
critically ill neurosurgical patient because of 1) slow rates of
sodium correction; 2) poor applicability in patients requiring multiple intravenous medications and/or
nutritional support; and 3) possible dangers of inducing or enhancing
cerebral ischemia in patients who already may be fluid-depleted. Reported successes in the treatment of
hyponatremia due to
SIADH by administration of
urea and
normal saline led to the authors' routine use of this
therapy for hyponatremic neurosurgical patients. A retrospective review of an 18-month period revealed 48 patients (3% of all neurosurgical inpatients) with
hyponatremia from various causes who received 62 treatments of
urea and
normal saline. Treatment consisted of 40 gm
urea dissolved in 100 to 150 ml
normal saline as an
intravenous drip every 8 hours and an
intravenous infusion of
normal saline at 60 to 100 ml/hr for 1 to 2 days. The mean pretreatment serum
sodium level (+/- standard deviation) was 130 +/- 3 mmol/liter (range from 119 to 134 mmol/liter). There was a significant mean posttreatment elevation to 138 +/- 4 mmol/liter (range 129 to 148 mmol/liter) (p less than 0.001, Student's t-test). Average daily fluid intake and output on treatment days were 2719 +/- 912 and 2892 +/- 1357 ml, respectively. There were no treatment complications in this group. It is concluded that
urea and saline administration results in a rapid, safe, and effective correction of
hyponatremia, making this method superior to fluid restriction in many neurosurgical patients.