A 40-year-old woman has an arterial $\mathrm{pH}$ of 7.25, an arterial $\mathrm{PCO}_{2}$ of $30 \mathrm{~mm} \mathrm{Hg}$, and serum $\left[\mathrm{K}^{+}\right]$of $2.8 \mathrm{mEq} / \mathrm{L}$. Her blood pressure is $100 / 80 \mathrm{~mm} \mathrm{Hg}$ when supine and $80 / 50$ $\mathrm{mm} \mathrm{Hg}$ when standing. What is the cause of her abnormal blood values?

Question

Quizplus · Accepted Answer

[Chapter 5 , IX D; Table 5.9]. The arterial blood values and physical findings are consistent with metabolic acidosis, hypokalemia, and orthostatic hypotension. Diarrhea is associated with the loss of $\mathrm{HCO}_{3}{ }^{-}$and $\mathrm{K}^{+}$from the gastrointestinal (GI) tract, consistent with the laboratory values. Hypotension is consistent with extracellular fluid (ECF) volume contraction. Vomiting would cause metabolic alkalosis and hypokalemia. Treatment with loop or thiazide diuretics could cause volume contraction and hypokalemia, but would cause metabolic alkalosis rather than metabolic acidosis.

A 40-Year-Old Woman Has an Arterial pH\mathrm{pH}pH Of 725, an Arterial PCO2\mathrm{PCO}_{2}PCO2​

A 40-Year-Old Woman Has an Arterial $\mathrm{pH}$ Of 725, an Arterial $\mathrm{PCO}_{2}$