Hyponatremia

The investigators are conducting this study to investigate new preventive measures for patients with low sodium levels (hyponatremia), which can occur after surgery on the pituitary gland. This hyponatremia is often caused by the syndrome of inappropriate antidiuresis (SIAD). SIAD occurs when the pituitary gland secretes too much antidiuretic hormone. The antidiuretic hormone causes the kidneys to absorb more water. This dilutes the sodium in the blood and leads to hyponatremia. Low sodium levels are particularly common after pituitary surgery, as the procedure on the pituitary gland can lead to increased reactive secretion of antidiuretic hormone. At present, apart from educating patients about the symptoms of hyponatremia, there are no established standard measures for prevention after pituitary surgery. If hyponatremia is present, it is currently treated primarily by fluid restriction, which is not always pleasant or easy to adhere to. With this study, the investigators want to investigate whether protein supplementation or fluid restriction between day 4 and day 9 after surgery can serve as a preventive measure to stabilize sodium levels after pituitary surgery and improve the quality of life of patients.

Hyponatremia is the most common electrolyte derangement occurring in hospitalized patients. It is usually classified as hypovolemic, euvolemic or hypervolemic. The most common aetiology of euvolemic hyponatremia is the syndrome of inappropriate antidiuresis (SIAD). Hypervolemic hyponatremia is common in patients with congestive heart failure (CHF) (10-27%) and liver cirrhosis (up to approximately 50%). In SIAD, the regulation of arginine vasopressin (AVP) secretion is impaired which leads to free water retention. In CHF and liver cirrhosis, the effective arterial blood volume is decreased leading to non-osmotic baroreceptor mediated AVP release and consecutive free water retention. Current treatments of euvolemic and hypervolemic hyponatremia, including the most used treatment fluid restriction, are of limited efficacy. Sodium-Glucose-Co-Transporter 2 (SGLT2) inhibitors reduce glucose reabsorption in the proximal tubule, resulting in glucosuria and consecutive osmotic diuresis. A placebo-controlled randomized trial of our group has shown that a short-term, i.e. a 4-days administration of the SGLT2 inhibitor empagliflozin (Jardiance)® in addition to fluid restriction was effective in increasing the serum sodium concentration in 87 patients with SIAD-induced hyponatremia. The effect of empagliflozin (Jardiance)® without additional fluid restriction is however not yet known. Large randomized controlled trials have shown that SGLT2 inhibitors reduced hospitalization for heart failure in patients with, and more recently without type 2 diabetes. No studies have investigated the effect of SGLT2 inhibitors in hypervolemic hyponatremia. To evaluate the effect of empagliflozin (Jardiance)® in eu- and hypervolemic hyponatremia, a randomized placebo-controlled study is needed.

Hyponatremia is the most common electrolyte disorder of all and can be observed in more than 30% of all patients in hospitals. Osmotic homeostasis of body fluids is essential for survival of all living creatures. It is widely accepted that extra- and intracellular osmolalities are in equilibrium at all times and thus, changes in the extracellular osmolality will lead to either shrinkage or swelling of cells which can be detrimental. In severe cases, it can lead to swelling of the brain and death. Even in less dramatic scenarios, symptoms such as epileptic seizures, headaches, depression and dizziness exist, leading to an increased risk of fractures, hospital admissions and a considerable burden for affected patients. As short-term defense against osmotic stress, each individual cell is capable of actively externalizing or internalizing osmotically active solutes which restores normal or near-normal cell volume at the expense of an altered milieu interior. Obviously, there must be limitations to this strategy if intracellular integrity is meant to be kept stable. It has therefore been postulated that, apart from this cell-immanent mechanism, extracellular and intracellular electrolyte stores could assist in buffering osmotic imbalances. The Edelman formula states that extracellular sodium is determined by the total amount of exchangeable body sodium (the major extracellular cation) plus potassium (the major intracellular cation) divided by total body water. Several studies have shown, that it only partially explains the changes in patients outside the osmotic equilibrium. To better understand these physiological responses might not only promote the researcher's insight into the most basic cellular self-defense systems by measuring and comparing extra- and intracellular electrolyte concentrations with estimated changes in a patient that will be intravenously challenged with either water or sodium chloride 3%. The evolution over time of extra- and intracellular sodium and other electrolytes will be assessed quantitatively in patients with impaired renal function after water or sodium chloride (NaCl) administration.

The goal of this study is to assess the impact of protein supplementation on hyponatremia caused by the syndrome of inappropriate antidiuresis during hospitalization.

ICU patients with severe hyponatremia and a high risk of rapid SNa overcorrection.

Observational study of biochemical volume biomarker levels in response to a standardized intravenous isotonic saline infusion in patients with hyponatremia.