Sodium And Stroke: Why Do Levels Drop?

Hyponatremia, or low sodium, is a common electrolyte disorder in patients with neurological disorders such as stroke. It is defined as serum sodium levels of 135 mmol/L or lower. The condition can be caused by the unchecked secretion of the antidiuretic hormone (ADH) or cerebral salt-wasting syndrome (CSWS). Studies have shown that acute ischemic stroke patients with hyponatremia have worse stroke scale scores on admission and discharge, as well as higher mortality rates in the hospital and at 3-month and 12-month follow-ups.

Hyponatremia is a common electrolyte disorder in stroke patients

The aetiology of hyponatremia in stroke patients is multifactorial and can be attributed to two main mechanisms: Syndrome of Inappropriate Antidiuretic Hormone (SIADH) and Cerebral Salt Wasting Syndrome (CSWS). In a study of 1000 stroke patients, 353 (35%) presented with hyponatremia, with 238 (67%) cases attributed to SIADH and 115 (33%) to CSWS.

SIADH occurs due to the unchecked secretion of antidiuretic hormone (ADH) from the posterior pituitary gland, resulting in body fluid hypotonicity and increased blood volume. It is often seen in patients with central nervous system (CNS) disorders, carcinomas, pulmonary disorders, and certain medications. On the other hand, CSWS is characterised by excessive natriuresis and subsequent hyponatremia, with dehydration in patients with intracranial disease. The exact mechanism of CSWS is not fully understood, but it may be related to increased sympathetic nervous system activity.

The clinical presentation of hyponatremia in stroke patients can vary depending on the severity of sodium depletion. Mild hyponatremia may be asymptomatic or present with non-specific symptoms such as lethargy, malaise, excessive sleepiness, and nausea. However, as hyponatremia progresses, neurological symptoms become more prominent and can include altered mental state, seizures, pulmonary edema, and cerebral edema.

The management of hyponatremia in stroke patients aims to address the underlying cause and normalise sodium levels. This may involve fluid restriction, medication adjustments, and in some cases, the administration of hypertonic saline. Close monitoring of serum sodium levels is crucial to prevent complications and improve patient outcomes.

It is caused by inappropriate secretion of antidiuretic hormone (SIADH) or cerebral salt wasting syndrome (CSWS)

Hyponatremia, or low sodium, is a common electrolyte disorder in patients with neurological disorders such as stroke. It is usually caused by either inappropriate secretion of antidiuretic hormone (SIADH) or cerebral salt wasting syndrome (CSWS).

SIADH is characterised by the unchecked secretion of antidiuretic hormone (ADH) from the posterior pituitary gland, which is stimulated by the hypothalamus. This results in body fluid hypotonicity and increased blood volume. It tends to occur in three disease groups: central nervous system (CNS) disorders, carcinomas, and pulmonary disorders. It is also associated with certain drugs, such as analgesics, antidepressants, barbiturates, carbamazepine, and oral hypoglycemic medications. Patients with SIADH typically present as euvolumic and hypertensive, and may exhibit neurological signs such as drowsiness, seizures, and coma.

On the other hand, CSWS is defined as "true hyponatremia," where there is a primary loss of sodium into the urine without an increase in total systemic volume. The exact mechanism of CSWS is not yet known, but one hypothesis suggests that it is due to an exaggerated renal pressure natriuresis caused by increased sympathetic nervous system activity.

In a study of 1000 stroke patients, 353 (35%) presented with hyponatremia, with 238 (67%) cases attributed to SIADH and 115 (33%) to CSWS. This highlights the significant impact of these conditions on stroke outcomes.

The distinction between SIADH and CSWS is crucial as they require different treatments. SIADH is typically managed by restricting fluids and administering drugs such as furosemide, demeclocycline, or lithium. In contrast, CSWS treatment involves addressing the underlying cause, volume replacement with normal or hypertonic saline solutions, and medications like fludrocortisones.

SIADH is characterised by body fluid hypotonicity and an expanded effective circulatory volume

Hyponatremia, or low sodium levels, is a common electrolyte disorder in patients with neurological disorders such as stroke. It is characterised by serum sodium levels of 135 mmol/L or lower. Hyponatremia is often caused by Syndrome of Inappropriate Antidiuretic Hormone (SIADH) or Cerebral Salt Wasting Syndrome (CSWS).

SIADH is a condition where the body produces excessive amounts of antidiuretic hormone (ADH), which is responsible for regulating water levels in the body. In SIADH, the secretion of ADH continues despite body fluid hypotonicity and an expanded effective circulatory volume. This means that the negative feedback mechanism that normally controls ADH fails, and the hormone continues to be released. As a result, the body is unable to excrete water through urine, disturbing the body's salt balance and leading to hyponatremia.

The symptoms of SIADH can vary depending on the severity of the condition. Mild cases may be asymptomatic, while more severe cases can lead to confusion, impaired balance, and an increased risk of falls. In older adults, confusion may be misattributed to age. If left untreated, SIADH can lead to coma, brain herniation, or even death.

SIADH is often reversible and can be treated by addressing the underlying causes, such as adjusting or changing medications that may be contributing to the condition. Treatment may also include high-salt infusions, fluid restriction, and medications that encourage the elimination of excess fluid or limit the production of ADH.

CSWS is defined as the primary loss of sodium into the urine without an increase in total systemic volume

Hyponatremia is a common electrolyte disorder encountered in patients with neurological disorders such as stroke. It is defined as serum sodium levels ≤135 mmol/L. In stroke patients, hyponatremia is mostly hypo-osmolar and may be caused by either the syndrome of inappropriate anti-diuretic hormone (SIADH) or cerebral salt-wasting syndrome (CSWS).

CSWS was first described by Peters et al. in 1950 as the development of excessive natriuresis and subsequent hyponatremia and dehydration in patients with intracranial disease.

The exact mechanism of CSWS is unknown

Hyponatremia, or low sodium, is a common electrolyte disorder in patients with neurological disorders such as stroke. It is usually caused by either the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) or cerebral salt-wasting syndrome (CSWS). While the former is more common than the latter, CSWS is associated with worse outcomes in stroke patients.

CSWS was first described by Peter et al. in 1950 and is defined by excessive natriuresis (increased sodium in the urine) and subsequent hyponatremia and dehydration in patients with intracranial disease. Despite many hypotheses, the exact mechanism of CSWS remains unknown.

One hypothesis suggests that CSWS is due to an exaggerated renal pressure natriuresis resulting from increased sympathetic nervous system activity. However, the precise pathophysiology is still unclear. Further research is needed to fully understand the mechanisms underlying CSWS and its role in stroke-related hyponatremia.

Distinguishing between SIADH and CSWS is crucial as they require different treatments. While SIADH is managed by fluid restriction and medications, CSWS is treated by addressing the underlying cause, volume replacement with normal or hypertonic saline, and drugs like fludrocortisones.

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