Gradient washout and secondary nephrogenic diabetes insipidus after brain injury in an infant: a case report

Transient severe hypotonic hyponatraemia in children - presentation of three cases

Hyponatraemia, defined as sodium concentration below 135 mmol/l, is one of the most common electrolyte imbalances. Differential diagnosis of hyponatraemia is difficult. We describe 3 cases of children with transient, severe hyponatraemia (< 125 mmol/l). While diagnosing hyponatraemia, it is of major importance to carefully ask in the anamnesis about habits related to the amount of fluid intake and the type of consumed fluids. It should also be noted that a frequent procedure during an infection is to increase fluid ingesting as a prevention of dehydration. One, however, should remember about the possibility of inducing water poisoning in a patient consuming excessive amounts of hypotonic fluids, especially when exposed to non-osmotic antidiuretic hormone stimulus, such as an acute infection or stress, and/or reduced renal excretory capacity. Only the presence of polyuria does not justify a diagnosis of arginine vasopressin deficiency (AVP-D), and especially the implementation of desmopressin treatment before all diagnostic procedures are completed, specifically in the case of hyponatraemia. Desmopressin can be used simultaneously with intravenous 3% saline solution only in the treatment of a very severe hyponatraemia, to avoid overcorrection of natraemia. In patients after profound hyponatraemia, polyuria can be observed after normalisation of fluid intake, but it is temporary.

Suspected medullary washout leading to severe polyuria following delayed cerebral ischemia: a case report

BACKGROUND

Delayed cerebral ischemia is a clinical entity commonly encountered in patients presenting with acute neurological injury and is often complicated by dysnatremias, such as the cerebral salt wasting syndrome. In this case report, we described an exceptional case of polyuria attributed to an initial cerebral salt wasting phenomenon and iatrogenic-induced medullary washout.

CASE PRESENTATION

A 53-year-old woman was admitted to our hospital for the management of a Modified Fisher scale grade 4 subarachnoid hemorrhage due to a ruptured posterior communicating aneurysm. She was initially managed with coil embolization and external ventricular drain due to secondary hydrocephalus. Throughout the course of her hospitalization, she developed severe polyuria reaching up to 40L per day. To keep up with the excessive urinary losses and maintain appropriate cerebral perfusion, fluid replacement therapy was adjusted every hour, reaching up to 1.3 L of crystalloid per hour in addition to aminergic support. An initial diagnosis of partial diabetes insipidus, followed by a cerebral salt wasting syndrome was suspected. While the urine output continued to increase, her serum urea concentration progressively decreased to a point of almost being undetectable on day 9. At that time, the presence of an interstitial medulla washout was hypothesized. Various pharmacological and non-pharmacological interventions were progressively introduced to regain normal renal homeostasis, including non-steroidal anti-inflammatory drugs, fludrocortisone, oral urea and high-protein intake. Medications were progressively weaned, and the patient was successfully discharged from the ICU.

CONCLUSIONS

Cerebral salt wasting should be considered in the initial differential diagnosis of a patient presenting with polyuria in the context of acute neurological injury. Early recognition of this entity is critical to quickly implement proper management. However, as shown in this case report, the concomitance of delayed cerebral ischemia may complexify that management.