Sodium Disorders: Hyponatremia and Hypernatremia

These flashcards cover key concepts and vocabulary related to sodium disorders, particularly hyponatremia and hypernatremia, as presented in the lecture.

Hyponatremia

Condition where sodium levels are too low, generally less than 135 mEq/L.

ADH (Antidiuretic Hormone)

Hormone that regulates water reabsorption in the kidneys; increases when blood volume or pressure is low.

Triggers for ADH release

Low blood volume and low blood pressure are primary triggers for the release of ADH.

Renin-Angiotensin-Aldosterone System (RAAS)

Hormonal system that regulates blood pressure and fluid balance; activated when blood volume is low.

Causes of Hypernatremia

Decreased water intake, increased water loss (i.e., through excessive urination, sweating, or diarrhea) or excess sodium intake.

Hypovolemic Hypernatremia

Condition in which the body loses water and sodium, but water loss is greater, leading to high sodium in the blood.

Urine Osmolality in Hyponatremia

High urine osmolality (>300 mOsm/kg) indicates ADH-dependent causes; low osmolality (<300 mOsm/kg) indicates ADH-independent causes.

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)

Condition in which excess ADH is produced without normal physiological triggers, leading to water retention and dilutional hyponatremia.

Symptoms of Hyponatremia

Cerebral edema, increased intracranial pressure, nausea, vomiting, confusion, seizures.

Treatment for Severe Hyponatremia

Rapid correction using hypertonic saline (>3% NaCl) while monitoring sodium levels to avoid osmotic demyelination syndrome.

Hypotonic Hyponatremia

True hyponatremia characterized by an osmolality <280 mOsm/kg; indicates low serum sodium.

Hypervolumic Hyponatremia

Condition characterized by high body water relative to sodium, often seen in conditions like heart failure or cirrhosis.

Central Diabetes Insipidus

Condition where ADH is not produced adequately due to damage to the hypothalamus or pituitary gland.

Nephrogenic Diabetes Insipidus

Condition where kidneys do not respond properly to ADH due to receptor problems.

Treatment for Central Diabetes Insipidus

Desmopressin (DDAVP) to replace ADH.

ADH Antagonists

Medications used to block the action of ADH, leading to increased water excretion.

Potassium and Sodium Relationship

High aldosterone levels can lead to hypokalemia (low potassium) due to increased renal excretion of potassium.

Osmotic Demyelination Syndrome

A complication from rapid correction of hyponatremia resulting in severe neurological deficits.

Free Water Deficit Calculation

Formula to determine how much water to replace in hypernatremia: (Total body weight) x (Desired sodium - Current sodium) / (Desired sodium).