Question of the Week

For September 6, 2016

A 17-year-old girl is admitted after undergoing posterior spinal fusion because of idiopathic spinal scoliosis. There were no intraoperative complications. The patient is receiving maintenance intravenous fluids, and her pain is well controlled with intravenous opioids and benzodiazepines. A urinary catheter is in place.

At 6 hours postoperatively, the nurse notes that the patient's urine output has decreased over the past few hours, from 3.0 to 0.5 mL/kg/hour.

The patient's heart rate is 90 beats per minute, her blood pressure is 122/68 mm Hg, and her weight is 60 kg. She is awake and responsive. Her cardiorespiratory examination is normal. There is no edema, and her capillary refill is <2 seconds.

Laboratory testing yields the following results:

Patient value

Reference range

Sodium (mEq/liter)

129

135–147

Potassium (mEq/liter)

3.4

3.4–4.7

Glucose (mg/dL)

118

70–105

Bicarbonate (mEq/liter)

24

22–26

Blood urea nitrogen (mg/dL)

7

5–18

Serum osmolality (mOsm/kg)

270

275–295

Urinalysis reveals a sodium level of 41 mEq/liter, an osmolality of 600 mOsm/kg, and a specific gravity of 1.030 (reference range, 1.001–1.035).

Which one of the following management approaches is most appropriate for this patient?

Administer oral sodium supplementation
Institute fluid restriction
Administer a furosemide bolus
Infuse 5% dextrose in 0.45% normal saline
Administer a bolus of 3% normal saline