Setting PICU

Consultant and PICU registrar

Problem 4 year old child transferred to PICU after space occupying lesion cranial surgery. On day 2 post operatively was noted to have very high urine output with falling serum sodium. His urine output was very variable and ranged from 3 ml/kg/hour to 17 ml/kg/hour. He had very high urinary sodium content.

Clinical context

• Falling sodium

• High urine output

• Low plasma osmolality

Assessment of problem and analysis of its causes

• Hyponatremia in Patients with Neurologic Disorders

• Inappropriate secretion of antidiuretic hormone (SIADH)

• Cerebral salt wasting (CSW) syndrome

Assessment of problem and analysis of its causesThe distinction between these two conditions is important because their treatments are different. It is not possible to distinguish CSW from SIADH based on serum and urine laboratory findings alone, because their associated abnormalities are identical. For this reason, accurate determination of the patient’s volume status is the key to differentiating these syndromes.

Fundamental difference between the two processes is extracellular fluid volume status. Patients with CSW have hypovolemia compared with patients with SIADH, who have euvolemic or mild extra cellular fluid expansion.

The mainstay of therapy for CSW is replacement of the sodium and water that is lost as a result of pathologic natriuresis and diuresis. This is in direct contrast to the treatment of SIADH, the crux of which is free water restriction.

CVP-directed treatment of hyponatremia and volume status in such patients is effective.

Intervention New guidelines for cerebral salt wasting introduced in PICU guidelines.

Lessons learnt Consider CSW in children with low sodium and high urine output, measure volume status, in PICU setting with CVP measurement