SIADH is diagnosed as a collection of symptoms that take place with otherwise normal function. This syndrome is characterized by hyponatremia, concentration of urine and dilution of blood. The patient has an adequate amount of blood, but it is more dilute than normal. SIADH causes the body to retain fluid resulting in decreased electrolyte balance.
SIADH is caused as an effect of other disorders, often nervous system disorders such as epilepsy, Guillain-Barre syndrome or head trauma, or cancers of the pulmonary, brain, GI and genitourinary systems. It is caused when the hypothalamus is stimulated to produce excess amounts of AVP (arginine vasopressin) which is an antidiuretic hormone (ADH) that triggers the kidneys to retain fluid in the tubules and excrete sodium. As the amount of fluid builds up in the cells and tissues, it creates an imbalance of electrolytes, specifically sodium, causing hyponatremia. The excess fluid dilutes the blood instead of being excreted causing the urine to become concentrated.
Patient will maintain normal electrolyte and fluid balance
Patients may be on fluid restrictions to help balance intake and output. Monitor for retention through calculated intake and output and with daily weights at the same time on the same scale each day.
Changes in electrolyte balance can disrupt the electrical conduction in the heart causing dysrhythmias.
Fluid shifts can occur quickly causing changes in blood pressure and heart rate. Most often patients will experience hypotension.
Excess fluid volume can settle in and around the lungs and heart. Monitor for signs of congestion, difficulty breathing. SIADH can also be triggered by pneumonia, so monitor for the underlying cause as well.
Supplements may be given to regulate electrolyte imbalance. Carefully administer supplements to avoid overloading too quickly
Hyponatremia is the hallmark of SIADH. Monitor lab values to determine if treatment is effective.
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