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: This is incorrect because respiratory alkalosis is a condition where the blood pH is higher than the normal range of 7.35 to 7.45, due to hyperventilation, which lowers the carbon dioxide in the blood. Severe diarrhea does not cause hyperventilation, but rather dehydration and electrolyte imbalance.

Choice B reason: This is incorrect because metabolic 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. Severe diarrhea does not cause a loss of acids or an excess of bases, but rather a loss of fluids and bicarbonate, which is a base that buffers the acids in the blood.

Choice C reason: This is correct because 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. Severe diarrhea causes a loss of fluids and bicarbonate, which is a base that buffers the acids in the blood. This leads to an accumulation of acids and a decrease in pH.

Choice D reason: This is incorrect because 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. Severe diarrhea does not affect the respiratory system directly, but rather the metabolic system.

An isotonic solution is a solution that has the same osmotic pressure as another solution, which means that the solute concentration on both sides of a semipermeable membrane is equal. This causes no net movement of water across the membrane, and the cells remain the same size and shape. An example of an isotonic solution is normal saline (0.9% sodium chloride), which is used to treat dehydration and fluid loss.