A mathematical approach to severe hyponatremia and hypernatremia in renal replacement therapies

Treating chronic hyponatremia by continuous renal replacement therapy (CRRT) is challenging because the gradient between a replacement fluid's [sodium] and a patient's serum sodium can be steep, risking too rapid of a correction rate with possible consequences. Besides CRRT, other gains and losses of sodium‐ and potassium‐containing solutions, like intravenous fluid and urine output, affect the correction of serum sodium over time, known as osmotherapy. The way these fluids interact and contribute to the sodium/potassium/water balance can be parsed as a mixing problem. As Na/K/H 2 O are added, mixed in the body, and drained via CRRT, the net balance of solutes must be related to the change in serum sodium, expressible as a differential equation. Its solution has many variables, one of which is the sodium correction rate, but all variables can be evaluated by a root‐finding technique. The mixing paradigm is proved to replicate the established equations of osmotherapy, as in the special case of a steady volume. The flexibility to solve for any variable broadens our treatment options. If the pre‐filter replacement fluid cannot be diluted, then we can compensate by calculating the CRRT blood flow rate needed. Or we can deduce the infusion rate of dextrose 5% water, post‐filter, to appropriately slow the rise in serum sodium. In conclusion, the mixing model is a generalizable and practical tool to analyze patient scenarios of greater complexity than before, to help doctors customize a CRRT prescription to safely and effectively reach the serum sodium target.

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“…Without trial and error, the direct way to calculate the D5W rate is to use algebra:

ml/h. This is the same technique as a formula that is widely used to dilute the pre ‐filter RF to a capping [Na]:

ml/h (Lippold & Patel, 2020 ; Tinawi & Bastani, 2021 ).…”

Section: Discussionmentioning

confidence: 99%

Safely correct hyponatremia with continuous renal replacement therapy: A flexible, all‐purpose method based on the mixing paradigm

Chen

Yee

Chiaramonte

2023

Physiological Reports

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“…The treatment of dysnatremias by peritoneal dialysis will be presented in the peritoneal dialysis section. Attention is required for the prevention of errors during the treatment of severe dysnatremia by dialytic methods (110)(111)(112)(113). These procedures require performance in intensive care units by well-trained personnel.…”

Section: Treatment Of Dysnatremias By Dialytic Methodsmentioning

confidence: 99%

“…There are important deficits in our knowledge about the treatment of dysnatremias in patients with CKD not on dialysis and by dialytic methods, particularly by peritoneal dialysis. These deficits include the targets of change in [Na], the best method to achieve these targets, the problems encountered during treatment, and particularly the outcomes of the treatments ( 113 , 148 ). Whether treatment of dysnatremias in CKD improves mortality is another important question that needs to be studied.…”

Section: Reviewmentioning

confidence: 99%

Dysnatremias in Chronic Kidney Disease: Pathophysiology, Manifestations, and Treatment

Arzhan

Lew²,

Ing³

et al. 2021

Front. Med.

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The decreased ability of the kidney to regulate water and monovalent cation excretion predisposes patients with chronic kidney disease (CKD) to dysnatremias. In this report, we describe the clinical associations and methods of management of dysnatremias in this patient population by reviewing publications on hyponatremia and hypernatremia in patients with CKD not on dialysis, and those on maintenance hemodialysis or peritoneal dialysis. The prevalence of both hyponatremia and hypernatremia has been reported to be higher in patients with CKD than in the general population. Certain features of the studies analyzed, such as variation in the cut-off values of serum sodium concentration ([Na]) that define hyponatremia or hypernatremia, create comparison difficulties. Dysnatremias in patients with CKD are associated with adverse clinical conditions and mortality. Currently, investigation and treatment of dysnatremias in patients with CKD should follow clinical judgment and the guidelines for the general population. Whether azotemia allows different rates of correction of [Na] in patients with hyponatremic CKD and the methodology and outcomes of treatment of dysnatremias by renal replacement methods require further investigation. In conclusion, dysnatremias occur frequently and are associated with various comorbidities and mortality in patients with CKD. Knowledge gaps in their treatment and prevention call for further studies.

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“…Yessayan et al ( 35 , 38 ) suggested adjusting the sodium concentration in the CRRT replacement fluid by adding 23.4% hypertonic saline (containing 4 mEq sodium per mL) to control the patient's serum sodium to the required correction level so that the hypernatremia could be corrected safely and gradually. The above measures changed the dose of CRRT replacement fluid, and serum sodium was monitored every 1–2 h during treatment ( 31 , 34 , 35 , 39 ). The concentration of sodium in the replacement solution can be calculated by the following formula:…”

Section: Application Of Crrt In Brain Injury Patients With Hypernatremiamentioning

confidence: 99%

Diagnosis and treatment of brain injury complicated by hypernatremia

Bai

et al. 2022

Front. Neurol.

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Hypernatremia is a common electrolyte disorder in patients with brain injury. The mortality of brain injury patients with severe hypernatremia may be as high as 86.8%. The efficacy of conventional treatment for hypernatremia is limited. Continuous renal replacement therapy (CRRT) can slowly, controllably, and continuously reduce the blood sodium concentration and gradually become an important treatment for severe hypernatremia patients. This review aims to provide important information for clinicians and clinical researchers by describing the etiology, diagnosis, hazards, conventional treatment, and CRRT treatment of hypernatremia in patients with traumatic brain injury.

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A mathematical approach to severe hyponatremia and hypernatremia in renal replacement therapies

Cited by 6 publications

References 17 publications

Safely correct hyponatremia with continuous renal replacement therapy: A flexible, all‐purpose method based on the mixing paradigm

Safely correct hyponatremia with continuous renal replacement therapy: A flexible, all‐purpose method based on the mixing paradigm

Dysnatremias in Chronic Kidney Disease: Pathophysiology, Manifestations, and Treatment

Diagnosis and treatment of brain injury complicated by hypernatremia

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