A client developed diabetes insipidus as a result of a severe traumatic brain injury. Which finding does the nurse expect to observe?

Choice A reason: Serum osmolality 380 mOsm/kg is the expected finding because it is a sign of dehydration, which is a common complication of diabetes insipidus. Diabetes insipidus is a condition where the body does not produce enough antidiuretic hormone (ADH), which is a hormone that helps the kidneys retain water and regulate the fluid balance in the body. A severe traumatic brain injury can damage the pituitary gland or the hypothalamus, which are parts of the brain that produce and secrete ADH. Without enough ADH, the kidneys produce large amounts of diluted urine, which causes the loss of water and electrolytes from the body. This increases the concentration of solutes in the blood, which is measured by the serum osmolality. A normal serum osmolality is between 275 and 295 mOsm/kg, while a high serum osmolality is above 300 mOsm/kg.

Choice B reason: Urine output of 500 mL in 24 hours is not the expected finding because it is a sign of oliguria, which is a low urine output. Oliguria can be caused by various factors, such as dehydration, kidney failure, or urinary obstruction, and can result in symptoms such as fluid retention, swelling, or electrolyte imbalance. Oliguria is not a common finding in diabetes insipidus, because the condition causes polyuria, which is a high urine output. Polyuria can be defined as urine output of more than 3 liters in 24 hours, or more than 200 mL per hour.

Choice C reason: Weight gain of 5 pounds in 48 hours is not the expected finding because it is a sign of fluid overload, which is a condition where the body retains too much fluid, which can cause edema, hypertension, and heart failure. Fluid overload can be caused by various factors, such as heart failure, kidney failure, or liver failure, and can result in symptoms such as shortness of breath, chest pain, or fatigue. Fluid overload is not a common finding in diabetes insipidus, because the condition causes dehydration, which is a loss of fluid from the body. Dehydration can cause weight loss, not weight gain.

Choice D reason: Decreased serum hematocrit levels is not the expected finding because it is a sign of anemia, which is a condition where the blood has a low level of hemoglobin, which is the protein that carries oxygen in the red blood cells. Anemia can be caused by various factors, such as blood loss, iron deficiency, or bone marrow failure, and can result in symptoms such as fatigue, weakness, or pallor. Anemia is not a common finding in diabetes insipidus, because the condition does not affect the production or function of the red blood cells. Diabetes insipidus can cause increased serum hematocrit levels, not decreased, because the loss of water from the body can increase the proportion of red blood cells in the blood.