In a patient with inadequate fluid intake, which laboratory values are likely to be elevated?

In a patient experiencing inadequate fluid intake, the elevated laboratory values most commonly observed are sodium and blood urea nitrogen (BUN). This condition, often leading to dehydration, impacts the concentrations of certain substances in the blood.

When fluid intake is insufficient, the concentration of sodium in the blood typically rises because there is less water available to dilute it. Sodium is a key electrolyte, and its homeostasis is closely tied to fluid balance. Elevated sodium levels can indicate hypernatremia, which is commonly seen in dehydration.

Blood urea nitrogen (BUN) also tends to increase with inadequate fluid intake due to a decrease in renal perfusion and the kidneys' ability to excrete urea effectively. When dehydrated, the kidneys conserve water, leading to a more concentrated blood urea nitrogen level. This relationship is essential for evaluating a patient’s hydration status and kidney function.

In summary, sodium and BUN are reliable indicators of dehydration and inappropriate fluid intake, reflecting the changes in the body’s ability to manage its electrolytes and waste products when under stress from fluid deficits.