After a craniotomy, what clinical indicators should the nurse monitor for inappropriate ADH secretion?

Inappropriate secretion of antidiuretic hormone (ADH), often referred to as syndrome of inappropriate ADH secretion (SIADH), can occur following a craniotomy due to various factors, including trauma, surgery, or other neurological conditions. In this case, monitoring for decreased serum sodium is crucial because SIADH leads to water retention, which dilutes the serum sodium levels, resulting in hyponatremia.

When ADH is secreted inappropriately, the kidneys retain water, causing an increased volume of fluid in the bloodstream, but without the corresponding increase in sodium. This dilution effect directly leads to a decrease in serum sodium concentration. Since sodium plays a vital role in maintaining cellular function and balance, a drop in serum sodium can have significant neurological implications, including confusion, seizures, or even coma in severe cases.

While increased weight can occur due to fluid retention associated with SIADH, it is a less direct indicator than serum sodium levels. Decreased level of consciousness can also occur when serum sodium drops significantly, but it is not an early clinical indicator and represents a secondary effect rather than a direct manifestation of inappropriate ADH secretion. Polyuria typically occurs in conditions like diabetes insipidus, which is characterized by low