Syndrome of inappropriate antidiuretic hormone (SIADH), a disorder of the posterior pituitary gland, is a condition of excessive release of antidiuretic hormone (ADH) that results in excessive water retention and hyponatremia. SIADH occurs when ADH secretion is activated by factors other than hyperosmolarity or hypovolemia. Excess ADH secretion increases renal tubular permeability and reabsorption of water into the circulation, resulting in excess extracellular fluid volume, reduced plasma osmolality, increased glomerular filtration rates, and decreased sodium levels. Without treatment, SIADH can lead to lifethreatening complications. Water intoxication accompanied by sodium deficit may lead to free water movement into cerebral cells, which can cause cerebral edema and result in coma and even death.
Several conditions contribute to SIADH. Central nervous system (CNS) responses to fear, pain, psychoses, and acute distress are known to increase the rate of ADH secretion by the posterior pituitary gland. Physiological conditions that increase intracranial pressure, such as acute CNS infections, brain trauma, anoxic brain death, cerebrovascular accident, and brain surgery, may lead to SIADH. Other conditions associated with SIADH include peripheral neuropathy, delirium tremens, and Addison’s disease and also certain medications such as analgesics, anesthetics, thiazide diuretics, and nicotine. Some tumors have been associated with ADH production, such as small cell carcinoma of the lungs, pancreatic cancer, prostate cancer, and Hodgkin’s disease. Positive pressure ventilation can also lead to SIADH in normovolemic individuals.
Nursing care plan assessment and physical examination
Ask if the patient has experienced alterations in urinary patterns. Question the patient about recent weight gain.
Signs of sodium deficit generally occur slowly. Ask if the patient has experienced recent fatigue, weakness, or headaches. Late signs include nausea, vomiting, muscle weakness, decreased level of consciousness, seizures, and even coma. Note that the most severe, life-threatening signs of SIADH are not fluid overload and pulmonary congestion but, rather, the CNS effects from acute sodium deficiency. The severity of hyponatremia determines the severity of findings on physical assessment. Perform a neurological assessment to determine if the patient has experienced changes in the level of consciousness, which can range from confusion to seizure activity. Life-threatening symptoms such as seizures may indicate acute water excess, whereas nausea, muscle twitching, headache, and weight gain are more indicative of chronic water accumulation.
The family and significant others may be fearful if the patient has experienced CNS changes that alter behavior and alertness. If the patient has had seizures, note that family members may have many questions. The patient’s and family’s responses to SIADH are often a reflection of their responses to these other conditions, which are important to consider in any evaluation of patient and family coping.
Nursing care plan primary nursing diagnosis: Fluid volume excess related to retention of free water.
Nursing care plan intervention and treatment plan
Restoration of normal electrolyte and fluid balance and normal body fluid concentration are the treatment goals. Treatment involves correction of the underlying cause and correction of hyponatremia. If the patient’s life is not in danger from airway compromise or severe hyponatremia, the physician often restricts fluids initially to 600 to 800 mL per 24 hours or less. With fluid restriction, the hormone aldosterone is released by the adrenal gland and the patient begins to conserve sodium in the kidneys. As serum sodium increases, SIADH gradually corrects itself. The patient needs assistance to plan fluid intake, and a dietary consultation is also required for consistency in fluid management.
If fluid restriction is unsuccessful, the physician may prescribe an intravenous (IV) infusion of a 3% to 4.5% saline solution. Use caution in administering these hypertonic solutions, and always place them on an infusion control device to regulate the infusion rate precisely. Monitor the patient carefully because sodium and water retention may result, thus leading to pulmonary congestion and shortness of breath. Diuretics to remove excess fluid volume may be used in patients with cardiac symptoms.
If the patient is at risk for airway compromise because of low serum sodium levels or seizure activity, maintaining a patent airway is the primary nursing concern. Insert an oral or nasal airway if the patient is able to maintain her or his own breathing, or prepare the patient for endotracheal intubation if it is needed. If the patient is able to maintain airway and breathing, consider positioning the patient so that the head of the bed is either flat or elevated no more than 10 degrees. This position enhances venous return and increases left atria filling pressure, which, in turn, reduce the release of ADH.
Explore with the patient methods to maintain the fluid restriction. If thirst and a dry mouth cause discomfort, try alternatives such as hard candy (if the patient is awake and alert) or chewing gum. Allocate some of the restricted fluids for ice chips to be used throughout the day at the patient’s discretion. Work with the patient to determine the amount of fluid to be sent on each tray so that fluid intake is spread equitably throughout the day. If the patient is receiving fluids in IV piggyback medications, consider those volumes as part of the 24-hour intake. Work with the pharmacy to concentrate all medications in the lowest volume that is safe for the patient.
Promote range-of-motion exercises for patients who are bedridden, and turn and reposition them every 2 hours to limit the complications of immobility. Maintain side rails in the up position to prevent injury if the patient has a decreased mental status. Initiate seizure precautions to ensure the patient’s safety.
Nursing care plan discharge and home health care guidelines
Be sure the patient or significant others understand the medication regimen, including the dosage, route, action, adverse effects, and need for follow-up laboratory tests (ADH level, serum sodium and potassium, blood urea nitrogen and creatinine, urine and serum osmolality). Instruct the patient to report changes in voiding patterns, level of consciousness, presence of edema, symptoms of hyponatremia, reduced neurological functioning, nausea and vomiting, and muscle cramping. If the patient is going home on fluid restriction, be sure to discuss methods of limiting fluid intake and encourage the patient to weigh himself or herself daily to monitor for fluid retention.
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