Correcting Hypernatremia in Children

Hyperosmolarity in children with hyperammonemia: a risk of brain herniation at the start of renal replacement therapy

Purpose

Renal replacement therapy (RRT) is used in hyperammonemia to reduce the concentration of ammonia in the blood. In the case of plasma hyperosmolarity, RRT can also rapidly decrease plasma osmolarity, which may increase cerebral edema in these patients and favor the occurrence of brain herniation.

Methods

We conducted a retrospective clinical study in a tertiary care university-affiliated hospital. All patients admitted in a Pediatric Intensive Care Unit (PICU), less than 18 years old with ammonemia >150 µmol/L and who underwent RRT between January 2015 and June 2023 were included. We collected data on plasma osmolarity levels, osmolar gap and blood ammonia levels before and during RRT.

Results

Eleven patients were included (10 with acute liver failure and 1 with a urea cycle disorders). Their mean age was 36.2 months. Before RRT, the median highest measured osmolarity was 320 (305-324) mOsm/L, whereas the median calculated osmolarity was 303 (293-314) mOsm/L, corresponding to an osmolar gap of 14 mOsm/L. Ammonia blood level over 400 µmol/L are significantly associated with higher plasma osmolarity (P-Value <0.001). In one case, a patient had a brain herniation episode after a quick osmolar drop. This episode was reversed by the administration of hyperosmolar agents and the temporary suspension of RRT.

Conclusion

This study highlights the hyperosmolarity and high osmolar gap that occur in children with hyperammonemia. A careful monitoring and control of plasma osmolarity evolution may alert clinician on the risk of occurrence of neurological complication such as brain herniation.

Updates in hyponatremia and hypernatremia

PURPOSE OF REVIEW

Hyponatremia and hypernatremia are commonly encountered electrolyte abnormalities that require timely and careful intervention, as they can be associated with significant morbidity and mortality.

RECENT FINDINGS

This review article addresses the etiology, presentation, diagnosis, and management of both hyponatremia and hypernatremia, emphasizing the latest advancements and emerging trends in pediatric care.

SUMMARY

A methodical approach is needed to accurately assess and treat hyponatremia and hypernatremia. Both conditions continue to rely on serum and urine testing, however newer tests such as copeptin and stimulated testing may hold promise to further refine testing in the future.

[Dysnatremias - concepts and clinical work-up]

Osmotic gradients over cell membranes lead to water movement into or out of cells. An intact osmoregulation prevents osmotic gradients, thereby protecting cells from swelling or shrinking. Na+ is the major cation in the extracellular fluid (ECF) and the major determinant of the osmolarity in the ECF, including plasma. Therefore, the plasma-Na+ concentration needs to be tightly regulated. An excess of electrolyte-free water decreases the concentration of osmolytes leading to hyponatremia. In contrast, a free water deficit increases the osmolyte concentration leading to hypernatremia. Pathophysiology-oriented approaches to dysnatremic patients help both clinicians and patients. Therapeutic interventions depend on the differentiation between acute and chronic, asymptomatic, and symptomatic dysnatremia, and on the patient's extracellular volume status. The therapeutic armamentarium for hyponatremia consists of water restriction, hypertonic infusions, urea, V2 receptor-blockers, and sodium-glucose cotransporter 2 (SGLT2) inhibitors. Patients with hypernatremia are treated with electrolyte-free water or hypotonic sodium-containing solutions depending on their volume status. Basic concepts in the management of dysnatremic patients are discussed.

Massive Chronic Hypernatremia Associated With Failure to Thrive in a Pediatric Patient

Hypernatremia is a severe, potentially life-threatening condition that can manifest with altered mental status, coma, seizure, and even death. Values above 190 mmol/L are seldom reported in young pediatric patients and often have poor outcomes. We present a case of severe chronic hypernatremia secondary to failure to thrive (FTT) in a toddler, which led to significant pathology including bilateral metabolic strokes. A 21-month-old female was found unresponsive and brought to the hospital. The patient's childhood was complicated by prematurity, poor weight gain, and persistent postprandial emesis. On examination, the patient was tachycardic and obtunded. Her weight was below the first percentile. Initial laboratory results showed a sodium level of 197 mmol/L with marked dehydration. Normal saline boluses were given followed by maintenance fluids with the goal of sodium decrementation by 0.5 mmol/hour; nephrology assisted with fluid and electrolyte correction calculations. Imaging revealed metabolic strokes involving the brainstem and thalami. During hospitalization, hypokalemia and hypophosphatemia complicated the treatment course. Over the next 21 days, electrolytes normalized. She tolerated nasogastric feeding, gradually improved as she gained weight, and was discharged. Chronic hypernatremia must be fixed judiciously as rapid correction can cause significant harm. This unusual case reminds providers that florid electrolyte dyscrasias may be secondary to FTT and can lead to significant neurological sequelae. Careful fluid selection and calculations should be performed in these cases. Chronic hypernatremia should be considered in children with FTT with altered mental status, and the gradual correction of electrolytes should be performed to minimize patient harm.