A nurse is monitoring an older adult female client who had a myocardial infarction (MI) for the development of an acute kidney injury. Which of the following findings should the nurse identify as indicating an increased risk of acute kidney injury (AKI)?

Choice A rationale Serum osmolality measures the concentration of dissolved particles in the blood, such as sodium, glucose, and urea. The normal range is 285 to 295 mOsm/kg. A value of 290 mOsm/kg is within the expected normal range, indicating a proper fluid and electrolyte balance. Since this finding is normal, it does not suggest the presence of acute kidney injury or provide evidence of impaired renal filtration or concentration abilities in this older adult client. Choice B rationale Magnesium is a vital intracellular cation involved in neuromuscular function and enzymatic reactions. The normal serum magnesium range is 1.3 to 2.1 mEq/L. A level of 2.0 mEq/L is a normal finding and does not indicate an increased risk or presence of renal dysfunction. In acute kidney injury, magnesium levels typically rise because the kidneys are unable to excrete the mineral effectively. This normal value suggests that renal excretion of magnesium remains currently stable. Choice C rationale Serum creatinine is a waste product of muscle metabolism excreted entirely by the kidneys. The normal range for females is 0.5 to 1.1 mg/dL. An elevated level of 1.8 mg/dL indicates impaired glomerular filtration, as the kidneys are failing to clear creatinine from the blood. For an older adult female, this elevation is a significant marker for acute kidney injury, reflecting a decrease in the number of functioning nephrons and overall renal clearance capacity. Choice D rationale Blood urea nitrogen measures the amount of urea nitrogen in the blood, a byproduct of protein breakdown in the liver. The normal range is 10 to 20 mg/dL. While 22 mg/dL is slightly elevated, it is less specific than creatinine for acute kidney injury. Minor elevations can occur due to dehydration, high protein intake, or decreased cardiac output following a myocardial infarction. It does not provide as definitive an indication of renal structural damage as creatinine.