Fluids & Electrolytes: Calcium, Phosphorus, and Magnesium

Twenty Q&A style flashcards covering normal ranges, causes, assessments, and treatments for calcium, phosphorus, and magnesium imbalances.

Which two hormones are the chief regulators of calcium levels?

Parathyroid hormone (PTH) and activated Vitamin D.

How do serum calcium and phosphorus levels relate to each other?

They have an inverse relationship—when one is high, the other tends to be low.

Name three common causes of hypercalcemia.

Hyperparathyroidism, excessive Vitamin D or calcium intake, and bone-destroying cancers (bone metastases).

List two neuromuscular findings typical of hypercalcemia.

Generalized weakness/flaccidity and decreased deep-tendon reflexes.

What are two key interventions for managing hypercalcemia?

Administer IV normal saline with loop diuretics and give calcitonin (other options: encourage oral hydration, dialysis as needed).

Give four possible causes of hypocalcemia.

Chronic renal failure, acute pancreatitis, Vitamin D deficiency, and hypoparathyroidism (others: malabsorption, alcoholism, hyperphosphatemia).

Positive Chvostek’s and Trousseau’s signs indicate which electrolyte imbalance?

Hypocalcemia.

How is symptomatic hypocalcemia treated?

PO or IV calcium supplements, given with Vitamin D, plus a calcium-rich diet.

Symptoms seen in hyperphosphatemia are usually manifestations of what concurrent electrolyte problem?

Hypocalcemia caused by the inverse Ca–P relationship.

List three common causes of hyperphosphatemia.

Renal failure, tumor lysis syndrome, and hypoparathyroidism.

What is the first-line pharmacologic therapy for hyperphosphatemia?

Phosphate binders taken with meals (along with management of associated hypocalcemia).

How does hyperparathyroidism affect phosphorus levels?

It causes hypercalcemia and consequently leads to hypophosphatemia.

Which life-threatening cardiac rhythm is associated with hypomagnesemia?

Torsades de pointes (a form of polymorphic ventricular tachycardia).

How is severe hypermagnesemia managed?

Hold Mg-containing products, give loop diuretics and IV calcium gluconate, and consider dialysis if needed.

Name two neuromuscular signs of hypomagnesemia.

Increased deep-tendon reflexes with muscle cramping/tetany, and paresthesias or seizures.