Review Question - QID 104323

This patient was likely started on a thiazide diuretic for her hypertension and developed contraction metabolic alkalosis. She needs volume resuscitation with isotonic saline.

Metabolic alkalosis is generated and maintained by four factors: volume depletion, chloride depletion, hypokalemia, and aldosterone excess. These factors either increase the rate of bicarbonate reabsorption or decrease the rate of bicarbonate secretion. There are four main clinical settings to consider:

1. Loss of gastric fluid - nasogastric drainage or vomiting
2. Diuretic therapy
3. Mechanical ventilation of patients with chronic respiratory acidosis
4. Primary hyperaldosteronism

In this vignette, hydrochlorothiazide caused sodium, chloride, and water excretion, but not bicarbonate. Because fluid is lost, the bicarbonate is distributed in a smaller extracellular fluid volume, so plasma bicarbonate rises. This "contraction" alkalosis can be rectified by replenishing volume.

Incorrect Answers:
Answer 1: Electrocardiogram is important to observe for hypokalemia-induced arrhythmia, but the patient's heart rate is normal and the physical exam is unremarkable. Delaying care for further diagnostics would be harmful in this case.

Answer 2 & 3: Potassium repletion is important, but metabolic alkalosis responds most to volume resuscitation. In fact, most potassium derangements correct with volume correction alone. Providing a supplement that includes bicarbonate would worsen the alkalosis. Potassium chloride at 40mEq would cause phlebitis through a peripheral IV.

Answer 5: Although the elevated creatinine suggests acute kidney injury despite a baseline creatinine not being provided, the history is already suggestive enough of a pre-renal etiology. No further workup is indicated for now.

Bullet Summary:
Metabolic alkalosis is commonly generated and maintained by volume, chloride, and potassium depletion; volume resuscitation is indicated to increase bicarbonate excretion.