Which situation would increase permeability of the blood-brain barrier?

Choice A rationale

Restricting fluids would be contraindicated in a patient with adrenal insufficiency experiencing hypotension. These patients suffer from a profound deficit of mineralocorticoids, specifically aldosterone, which leads to massive urinary loss of sodium and water. Normal serum sodium is 135 to 145 mEq/L. The resulting hypovolemia requires aggressive fluid resuscitation with isotonic saline to restore circulating volume and blood pressure. Fluid restriction would worsen the cardiovascular collapse and exacerbate the Addisonian crisis.

Choice B rationale

Providing potassium supplements is dangerous because hyperkalemia is already present in adrenal insufficiency. Normal serum potassium is 3.5 to 5.0 mEq/L. Without aldosterone, the kidneys cannot effectively excrete potassium in exchange for sodium. Adding more potassium would increase the risk of life threatening cardiac arrhythmias or cardiac arrest. The clinical goal is to lower the potassium levels through volume expansion and corticosteroid replacement rather than increasing the total body potassium load.

Choice C rationale

Administering insulin is a temporary measure used to shift potassium from the extracellular fluid into the intracellular compartment. While it addresses the hyperkalemia, it does not treat the underlying cause of the crisis, which is a lack of cortisol and aldosterone. Furthermore, patients in adrenal crisis are often hypoglycemic due to glucocorticoid deficiency. Giving insulin without dextrose could cause fatal hypoglycemia. It is not the primary priority compared to replacing the missing hormones.

Choice D rationale

Administering intravenous hydrocortisone is the priority intervention because it provides both glucocorticoid and mineralocorticoid activity. This replacement therapy addresses the underlying hormonal deficit, helping to restore vascular tone, increase blood glucose levels, and promote the renal retention of sodium and excretion of potassium. By correcting the hormonal imbalance, hydrocortisone stabilizes the hemodynamics and electrolyte disturbances. This intervention is essential to reverse the life threatening systemic effects of an acute adrenal or Addisonian crisis.

Choice A rationale

Hypophosphatemia is a condition where serum phosphorus levels fall below the normal range of 2.5 to 4.5 mg/dL. While phosphorus levels can be affected by various metabolic processes and insulin administration, it is not the primary electrolyte concern during prolonged vomiting and metabolic alkalosis. The shifts associated with alkalosis specifically target cations rather than anions like phosphate. Therefore, while monitoring is important in complex cases, it is not the highest risk associated with this specific acid-base disturbance.

Choice B rationale

Hyponatremia involves a sodium level below 135 to 145 mEq/L. Vomiting does cause the loss of sodium and water, but the body often compensates through the renin-angiotensin-aldosterone system, which promotes sodium retention to maintain volume. While sodium levels may fluctuate, the hallmark of metabolic alkalosis from upper gastrointestinal loss is the specific depletion of hydrogen and chloride. Potassium imbalances usually present a more acute and life-threatening risk than the moderate sodium fluctuations seen in simple vomiting.

Choice C rationale

Hypocalcemia is defined as a total serum calcium level below 9.0 to 10.5 mg/dL. In an alkalotic state, the decrease in hydrogen ions causes more calcium to bind to albumin, which reduces the amount of ionized, physiologically active calcium in the blood. While this can cause symptoms like tetany, it is often a functional deficiency rather than a total body deficit. Potassium depletion is generally more severe in vomiting because it involves both direct loss and significant renal excretion.

Choice D rationale

Hypokalemia, where potassium is less than 3.5 to 5.0 mEq/L, is the highest risk. During vomiting, potassium is lost directly in gastric secretions. Furthermore, in metabolic alkalosis, hydrogen ions move out of cells to compensate for the high extracellular pH, forcing potassium to move into the cells to maintain electrical neutrality. Additionally, the kidneys excrete more potassium in exchange for retaining hydrogen ions. These three mechanisms work together to rapidly and severely deplete serum potassium levels.