Electrolyte Imbalance Review

Flashcards covering the pathophysiology, clinical presentation, and treatment for electrolyte imbalances involving potassium, sodium, and calcium based on the Dr. Tasneem Smerat lecture notes.

Na+/K+-ATPase pump

The mechanism responsible for maintaining the disproportionate intracellular distribution of potassium by transporting sodium out of the cell in exchange for potassium.

External Potassium Balance

The process by which the kidney regulates total body potassium by matching potassium excretion to dietary intake.

Internal Potassium Balance

An extrarenal process that regulates the distribution of potassium across cell membranes.

Hypokalemia

A condition defined as a serum potassium concentration of $< 3.5\,mEq/L$ ($mmol/L$).

Myalgias

A clinical symptom of moderate hypokalemia characterized by muscle pain.

U-wave elevation

An ECG change associated with severe hypokalemia where the serum concentration is $< 2.5\,mEq/L$ ($mmol/L$).

Hyperkalemia

A condition defined as a serum potassium concentration of $> 5\,mEq/L$ ($mmol/L$).

Peaked T waves

The earliest ECG change observed in hyperkalemia, typically occurring when serum potassium is between $5.5$ and $6\,mEq/L$ ($mmol/L$).

Sodium polystyrene sulfonate

A cation-exchange resin used as a pharmacological option for asymptomatic patients with mild-to-moderate hyperkalemia.

Hyponatremia

A disorder of water balance defined as a serum sodium concentration of $< 135\,mEq/L$.

SIADH

The most common cause of euvolemic hyponatremia, often triggered by drugs like SSRIs or carbamazepine.

Osmotic Demyelination Syndrome

A risk associated with the rapid correction of chronic hyponatremia, also known as central pontine myelinolysis.

Hypernatremia

A disorder of water deficit relative to sodium, defined as a serum sodium concentration of $> 145\,mEq/L$.

Diabetes insipidus (DI)

A cause of renal water loss leading to hypernatremia, which can be central (lack of ADH) or nephrogenic (ADH resistance).

Ionized Calcium

The physiologically active form of calcium in the plasma, representing approximately $47\%$ of the total.

Parathyroid hormone (PTH)

A hormone secreted when blood $Ca^{2+}$ is low that raises serum calcium by stimulating bone resorption and increasing renal absolute $Ca^{2+}$ reabsorption.

Calcitonin

A hormone secreted by thyroid C cells when blood $Ca^{2+}$ is high that lowers serum calcium by inhibiting osteoclast activity.

Tetany

The hallmark clinical manifestation of acute hypocalcemia, including paresthesias, muscle spasms, and carpopedal spasms.

Hypercalcemic crisis

A medical emergency characterized by an acute elevation of serum calcium to greater than $15\,mg/dL$, often leading to acute kidney injury and obtundation.

Cinacalcet

A calcimimetic drug that activates the calcium-sensing receptor (CaSR) on parathyroid chief cells to treat hypercalcemia secondary to parathyroid carcinoma.