Refractory hyponatremia.

CASE PRESENTATION A 51-year-old woman with a history of an olfactory neuroblastoma treated with radiation, chemotherapy, and surgical resection 13 years ago was admitted for evaluation and treatment of persistent nausea, vomiting, fatigue, and dehydration. The patient suffered from significant cosmetic defects since resection of the neuroblastoma, and had undergone a left eyebrow lift 1 year before presentation for chronic left facial droop. The surgery was complicated by recurrent left scalp wound infections requiring long antibiotic courses. Owing to the persistence of infection despite appropriate antibiotic therapy, she underwent partial resection of a mesh in the wound 3 weeks before presentation. She was doing well after this procedure until 2 days before admission, when she developed persistent nausea, vomiting, and diarrhea. She was subsequently admitted for further evaluation and treatment. Other than the neuroblastoma, her past medical history was remarkable only for depression. Her outpatient medications at the time of admission included intravenous vancomycin and piperacillin/tazobactam, rifampin, amitriptyline at a stable dose for the past 6 months, and vitamin B6 supplements. She was unemployed, did not use tobacco or alcohol, and lived with her husband. She had one child, a daughter, who is a registered nurse. Her vital signs on admission were notable for a temperature of 981F, pulse of 75/min, and blood pressure of 84/50 mm Hg. Her blood pressure before surgery averaged around 105/70 mmHg. Orthostatic vital signs were not able to be obtained owing to extreme dizziness when she attempted to stand or sit up. Her physical exam was notable for dry mucous membranes, flat neck veins, clear lungs, benign abdominal examination, no lower extremity edema, and markedly decreased skin turgor. Initial laboratory results included were Na 120 mmol/l (her most recent serum Na 4 weeks ago was 140 mmol/l), K 3.0 mmol/l, Cl 87 mmol/l, HCO3 22.0 mmol/l, blood urea nitrogen 5 mg/dl, Cr 0.6 mg/dl, and serum osmolality 242 mosm/kg (Table 1). Urine electrolytes obtained on the same afternoon of admission were notable for Na 110 mmol/l and osmolality 351 mosm/kg (Table 2). Her white blood cell count was 4100/ml, hemoglobin 10.6 g/dl, hematocrit 28.1%, and platelets 251 000/ml. Her serum glutamic pyruvic transaminase (SGPT) was 66 U/l, serum glutamic oxaloacetic transaminase (SGOT) 50 U/l, and albumin was 3.2 g/dl. Her uric acid level was 2.2 mg/dl. Her urinalysis had an specific gravity (SPGR) of 1.019, pH of 6.5, and was negative for leukocytes, heme, and glucose. A chest radiograph was unremarkable. She was initially treated with intravenous normal saline with 5% dextrose for a total of 2.4 l and anti-emetics through the first 2 days of admission. With this regimen her serum sodium increased from 120 to 123 mmol/l (Table 1 and Figure 1), although she remained hypotensive and orthostatic. Repeat urine electrolytes were notable for Na 222 mmol/l, K 36.8 mmol/l, and osmolality 550 mosm/kg (Table 2). Owing to the increase in urine osmolality, she was placed on a 1 l daily fluid restriction to treat presumed syndrome of inappropriate antidiuretic hormone (SIADH). After 2 days of fluid restriction, she remained hypotensive and her serum sodium decreased to 118 mmol/l. A renal consult was then obtained on the fourth hospital day for ‘refractory SIADH.’ Her vital signs at the time of renal consultation included a blood pressure of 80/61 mmHg, a heart rate of 66/min, and a temperature of 98.81F. Her physical examination was again notable for dry mucous membranes, marked skin tenting, and inability to obtain orthostatic vital signs owing to dizziness with sitting or standing. Her thyroid and adrenal function were tested and were found to be normal. Owing to prominent signs of extracellular fluid (ECF) contraction, her fluid restriction was discontinued, and she was started on a normal saline infusion at 100 ml/h (hospital day 4). Within the first 24 h of normal saline infusion, her serum sodium increased from 118 to 132 mmol/l (Table 1 and Figure 1), and her urine output was noted to increase from an average of 600 ml/day in the preceding 2 days to 3.6 l over the course of the next day. Her urine electrolytes, however, continued to demonstrate inappropriate natriuresis in the face of persistent hyponatremia and signs and symptoms of ECF contraction, and her serum sodium again fell after hospital day 5 when continuous IV saline infusions were stopped and sporadic IV saline boluses were administered instead (Table 1 and Figure 1). An magnetic resonance imaging of http://www.kidney-international.org t h e r e n a l c o n s u l t