Which information is most important for the nurse to communicate rapidly to the health care provider about a patient admitted with possible syndrome of inappropriate antidiuretic hormone (SIADH)?

A. The patient has a recent weight gain of 9 lb.
B. The patient complains of dyspnea with activity.
C. The patient has a urine specific gravity of 1.025.
D. The patient has a serum sodium level of 118 mEq/L.

The correct answer is D. The most critical piece of information for a nurse to communicate urgently to a healthcare provider about a patient with possible SIADH is a serum sodium level of 118 mEq/L, as it suggests severe hyponatremia requiring immediate attention and treatment.

Explanation:

The most important information for a nurse to rapidly communicate to the healthcare provider about a patient admitted with possible Syndrome of Inappropriate Antidiuretic Hormone (SIADH) is the patient has a serum sodium level of 118 mEq/L. SIADH is characterized by the excessive release of Antidiuretic Hormone (ADH), also known as vasopressin, which leads to water reabsorption in the kidneys and causes dilutional hyponatremia (low serum sodium concentration). A serum sodium level of 118 mEq/L indicates severe hyponatremia and can pose immediate dangers such as cerebral edema, seizures, and even death if not promptly corrected.

Hyponatremia is a critical finding in SIADH patients and is a direct consequence of ADH causing increased water retention, which dilutes the sodium in the body. As the serum sodium drops, patients may experience neurological symptoms such as confusion, seizures, or even coma. In addition to reporting low sodium levels, it is also essential to consider other findings such as the patient's weight gain, dyspnea on activity, and urine specific gravity, which provide further evidence of SIADH. However, serum sodium levels provide the most critical information impacting immediate clinical decisions. Prompt intervention with fluid restriction, salt administration, or medications to reduce water reabsorption can be lifesaving.

Understanding the role of ADH in maintaining plasma osmolarity and blood pressure is crucial for recognizing the pathophysiology of SIADH. ADH typically responds to increased plasma osmolality by triggering water reabsorption in the kidneys to restore balance. In SIADH, ADH secretion is inappropriate relative to osmolarity, leading to excessive water reabsorption, which in turn reduces urine volume while diluting blood sodium. Therefore, assessing the osmotic balance and sodium levels are integral for managing SIADH.