Abstract
Hyponatremia is the most common electrolyte disorder in clinical practice and is associated with increased morbidity and mortality. It is frequently encountered in hematologic patients with either benign or malignant diseases. Several underlying mechanisms, such as hypovolemia, infections, toxins, renal, endocrine, cardiac, and liver disorders, as well as the use of certain drugs appear to be involved in the development or the persistence of hyponatremia. This review describes the pathophysiology of hyponatremia and discusses thoroughly the contributing factors and mechanisms that may be encountered specifically in patients with hematologic disorders. The involvement of the syndrome of inappropriate antidiuretic hormone (SIADH) secretion and renal salt wasting syndrome (RSWS) in the development of hyponatremia in such patients, as well as their differential diagnosis and management, are also presented. Furthermore, the distinction between true hyponatremia and pseudohyponatremia is explained. Finally, a practical algorithm for the evaluation of hyponatremia in hematologic patients, as well as the principles of hyponatremia management, are included in this review.
Highlights
Hyponatremia, usually defined as serum sodium concentration < 135 mEq/L, is the most common electrolyte abnormality encountered both in hospitalized patients and in the general population and is associated with increased morbidity and mortality [1,2]
Long-term survivors of hematopoietic stem cell transplantation (HSCT) are at increased risk of developing metabolic syndrome and Diabetes mellitus (DM); these probably ensue in the context of the long-term effects of intensive chemotherapy, as well as the immunological and inflammatory consequences of graft versus host disease (GvHD) and its treatment [87]
Urine sodium concentration (UNa) in a random urine specimen has a pivotal role in the diagnostic approach
Summary
Hyponatremia, usually defined as serum sodium concentration < 135 mEq/L, is the most common electrolyte abnormality encountered both in hospitalized patients and in the general population and is associated with increased morbidity and mortality [1,2]. The rapidity and the degree of reduction in serum sodium concentration are the main determinants of the symptoms associated with this electrolyte disorder. Chronic moderate (serum sodium levels 120–129 mEq/L) and mild (serum sodium levels 130–134 mEq/L) hyponatremia are usually asymptomatic and have no remarkable findings on a conventional clinical examination Individuals with such sodium levels may develop subtle manifestations, e.g., fatigue, cognitive impairment, disorientation and gait disorders, as well as falls, osteoporosis, and fractures [3,4]. In a study including hospitalized children treated for acute lymphoblastic leukemia (ALL), the incidence of hyponatremia (serum sodium levels < 130 mmol/L) on at least 2 out of 3 consecutive days was 11.9% [8]. Hyponatremia was significantly related both to neurologic complications and the existence of obvious central nervous system leukemia at diagnosis [8] In another single center analysis of 140 pediatric patients, hyponatremia was observed in 40% of patients following hematopoietic stem cell transplantation (HSCT) [9].
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