The nurse is aware that small ions such as glucose, oxygen, and carbon dioxide redistribute themselves through semipermeable membranes by a process called

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Choice A reason: Producing phosphate buffers is not the main function of the kidneys in response to acid-base disturbances. Phosphate buffers are mainly found in the intracellular fluid and the urine, where they help to maintain the pH by binding or releasing hydrogen ions.

Choice B reason: Adjusting PaCO2 levels is not the function of the kidneys, but rather the function of the lungs in response to acid-base disturbances. The lungs regulate the PaCO2 levels by increasing or decreasing the rate and depth of respiration, which affects the amount of carbon dioxide exhaled.

Choice C reason: Producing protein buffers is not the function of the kidneys, but rather the function of the cells and the plasma in response to acid-base disturbances. Protein buffers are the most abundant and versatile buffers in the body, as they can act as acids or bases by donating or accepting hydrogen ions.

Choice D reason: Excreting or reabsorbing hydrogen or bicarbonate is the main function of the kidneys in response to acid-base disturbances. The kidneys regulate the HCO3- levels by either reabsorbing it from the filtrate or generating it from carbon dioxide and water. The kidneys also regulate the hydrogen ion levels by either excreting it into the urine or exchanging it for sodium ions.

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.