Lena Mason, who has diabetes, is admitted in a stuporous condition. Her blood gases show a pH of 7.33, PaCO2 of 40 mm Hg, and HCO3- of 20 mEq/L. What type of acid-base imbalance does this patient have?

Choice A reason: 60 mL of urine in a 2-hour period is not very concerning for a nurse, as it is within the normal range of urine output. The average urine output for an adult is about 1 to 2 L per day, or 40 to 80 mL per hour¹.

Choice B reason: 720 mL of urine in a 24-hour period is slightly below the normal range, but not alarming. It may indicate mild dehydration or reduced fluid intake, but it is not a sign of fluid volume excess or kidney failure¹.

Choice C reason: 600 mL of urine in a 10-hour period is also within the normal range of urine output, and does not indicate any problem with fluid balance or renal function¹.

Choice D reason: 100 mL of urine in a 5-hour period is the most concerning for a nurse, as it indicates oliguria, or abnormally low urine output. Oliguria is defined as urine output less than 400 mL per day, or less than 20 mL per hour². It may be caused by acute or chronic kidney injury, urinary obstruction, shock, dehydration, or fluid volume excess². Oliguria can lead to fluid overload, electrolyte imbalance, acidosis, and uremia, and requires immediate medical attention².

Choice A reason: Stroke is not a cause of hyponatremia, but rather a possible complication of it. Hyponatremia is a condition where the sodium level in the blood is too low, which can affect the brain function and cause symptoms such as confusion, seizures, or coma. Stroke is a condition where the blood supply to a part of the brain is interrupted, which can cause brain damage and neurological deficits.

Choice B reason: Dehydration is not a cause of hyponatremia, but rather a cause of hypernatremia. Dehydration is a condition where the body loses more fluids than it takes in, which can affect the blood volume and the electrolyte balance. Dehydration can cause hypernatremia, which is a condition where the sodium level in the blood is too high, which can also affect the brain function and cause symptoms such as thirst, dry mouth, or lethargy.

Choice C reason: Increased secretion of aldosterone is not a cause of hyponatremia, but rather a cause of hypokalemia. Aldosterone is a hormone that regulates the sodium and potassium levels in the body by increasing the reabsorption of sodium and the excretion of potassium in the kidneys. Increased secretion of aldosterone can cause hypokalemia, which is a condition where the potassium level in the blood is too low, which can affect the muscle and nerve function and cause symptoms such as weakness, cramps, or arrhythmias.

Choice D reason: Congestive heart failure (CHF) is a cause of hyponatremia, as it is a condition where the heart is unable to pump enough blood to meet the body's needs. This can lead to fluid retention and edema, which can dilute the sodium level in the blood and cause hyponatremia. CHF can also stimulate the release of antidiuretic hormone (ADH), which increases the reabsorption of water in the kidneys and further lowers the sodium level in the blood.