If a client has developed SIADH after a craniotomy, which manifestation should the nurse anticipate?

In the case of a client who has developed Syndrome of Inappropriate Antidiuretic Hormone secretion (SIADH) after a craniotomy, oliguria is the expected manifestation. SIADH leads to excessive secretion of antidiuretic hormone (ADH), resulting in the body retaining water and consequently diluting serum sodium levels. This condition causes decreased urine output, as the kidneys are instructed to reabsorb more water rather than excrete it.

Oliguria refers specifically to a noticeable decline in urine output, typically classified as less than 400 milliliters of urine per day in adults. In the presence of SIADH, the excess fluid retention causes the kidneys to produce less urine, leading to oliguria as the body attempts to manage fluid balance and maintain normal serum sodium levels.

Understanding this helps differentiate it from other potential manifestations. For instance, polyuria and frequent urination would indicate conditions where there is an excess of urine production, while increased thirst, a common response to dehydration, would not make sense in the context of SIADH, where fluid retention occurs. Hence, anticipating oliguria is crucial for effectively managing the client's condition post-craniotomy.