George Torres is admitted with a head injury. He is comatose and is breathing rapidly. His blood gases show a pH of 7.47, PaCO2 of 32 mm Hg, and HCO3- of 26 mEq/L. Compare these gases to normal values. What type of imbalance does this patient have, and is it being compensated or uncompensated?

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: This is incorrect because low HCO3- and high PaCO2 are signs of metabolic acidosis, not alkalosis. Metabolic acidosis is a condition where the blood pH is lower than the normal range of 7.35 to 7.45, due to an excess of acids or a loss of bases in the body.

Choice B reason: This is incorrect because low PaCO2 and low HCO3- are signs of respiratory acidosis, not alkalosis. Respiratory acidosis is a condition where the blood pH is lower than the normal range of 7.35 to 7.45, due to impaired gas exchange or hypoventilation, which causes carbon dioxide to accumulate in the blood.

Choice C reason: This is correct because low PaCO2 and high HCO3- are signs of alkalosis. Alkalosis is a condition where the blood pH is higher than the normal range of 7.35 to 7.45, due to a loss of acids or an excess of bases in the body. There are two types of alkalosis: respiratory and metabolic. Respiratory alkalosis is caused by hyperventilation, which lowers the PaCO2 in the blood. Metabolic alkalosis is caused by vomiting, diuretics, or excessive intake of antacids, which raises the HCO3- in the blood.

Choice D reason: This is incorrect because high PaCO2 and high HCO3- are signs of compensation, not alkalosis. Compensation is a process where the body tries to restore the normal pH by adjusting the levels of PaCO2 and HCO3- in the opposite direction of the primary disorder. For example, if the patient has metabolic alkalosis, the respiratory system will try to compensate by retaining carbon dioxide and lowering the PaCO2. If the patient has respiratory alkalosis, the renal system will try to compensate by excreting bicarbonate and lowering the HCO3-.