Electrolyte and Fluid Volume Cheat Sheet

Vocabulary flashcards covering normal electrolyte lab ranges, clinical manifestations, ECG changes, and fluid volume alterations based on lecture notes.

Normal Sodium ($\text{Na}^+$) Range

$$135-145\,\text{mEq/L}$$

Hyponatremia

A serum sodium level below $135\,\text{mEq/L}$ that primarily affects neurological function due to brain swelling, causing symptoms such as headache, nausea, vomiting, confusion, lethargy, seizures, decreased level of consciousness, and coma.

Hypernatremia

A serum sodium level above $145\,\text{mEq/L}$ caused by dehydration or sodium excess, presenting with extreme thirst, dry mucous membranes, restlessness, irritability, confusion, muscle twitching, weakness, seizures, and coma.

Normal Potassium ($\text{K}^+$) Range

$$3.5-5.0\,\text{mEq/L}$$

Hypokalemia

A serum potassium level below $3.5\,\text{mEq/L}$ causing muscle weakness, fatigue, muscle cramps, constipation, ileus, decreased reflexes, dysrhythmias, flattened or inverted T waves, U waves, and potential cardiac arrest.

Hyperkalemia

A serum potassium level above $5.0\,\text{mEq/L}$ causing muscle weakness, paresthesias, abdominal cramping, diarrhea, dysrhythmias, peaked T waves, widened QRS, bradycardia, and potential cardiac arrest.

Normal Calcium ($\text{Ca}^{2+}$) Range

$$8.5-10.5\,\text{mg/dL}$$

Hypocalcemia

A serum calcium level below $8.5\,\text{mg/dL}$ causing increased neuromuscular excitability, tingling/numbness, muscle cramps, muscle spasms, tetany, positive Chvostek's sign, positive Trousseau's sign, seizures, laryngospasm, hyperactive reflexes, cardiac dysrhythmias, and prolonged QT interval.

Hypercalcemia

A serum calcium level above $10.5\,\text{mg/dL}$ causing decreased neuromuscular activity ('bones, stones, groans, and psychiatric overtones'), kidney stones, bone pain, muscle weakness, fatigue, constipation, abdominal pain, nausea/vomiting, confusion, lethargy, depression, dysrhythmias, and shortened QT interval.

Normal Magnesium ($\text{Mg}^{2+}$) Range

$$1.7-2.2\,\text{mg/dL}$$

Hypomagnesemia

A serum magnesium level below $1.7\,\text{mg/dL}$ causing increased neuromuscular excitability ('twitchy'), tremors, muscle cramps, hyperactive reflexes, tetany, weakness, seizures, confusion, dysrhythmias, Torsades de pointes, and refractory hypokalemia.

Hypermagnesemia

A serum magnesium level above $2.2\,\text{mg/dL}$ causing decreased neuromuscular activity ('everything slows down'), hyporeflexia, muscle weakness, lethargy, hypotension, bradycardia, respiratory depression, confusion, and cardiac arrest.

Severe Magnesium Toxicity Antidote

IV calcium gluconate.

Normal Phosphorus ($\text{PO}_4^{3-}$) Range

$$2.5-4.5\,\text{mg/dL}$$

Phosphorus and Calcium Inverse Relationship

The reciprocal physiological relationship where an increase in phosphorus causes calcium to decrease, and a decrease in phosphorus causes calcium to increase.

Hypophosphatemia

A serum phosphorus level below $2.5\,\text{mg/dL}$ causing muscle weakness, bone pain, confusion, irritability, respiratory muscle weakness (which can cause respiratory failure), seizures, dysrhythmias, and difficulty swallowing.

Hyperphosphatemia

A serum phosphorus level above $4.5\,\text{mg/dL}$ commonly caused by kidney failure, hypoparathyroidism, or tumor lysis, resulting in low calcium symptoms such as muscle cramps, tetany, tingling/numbness, muscle spasms, seizures, bone/joint pain, and soft tissue calcification.

Hypovolemia

Too little fluid in the vascular space ('DRY + FAST + LOW'), characterized by tachycardia, hypotension, weak/thready pulse, dry mucous membranes, poor skin turgor, decreased urine output, dark/concentrated urine, weight loss, dizziness, orthostatic hypotension, weakness, confusion, and elevated BUN/creatinine ratio.

Hypervolemia

Too much fluid volume in the body ('WET + SWOLLEN + HEAVY'), characterized by edema, weight gain, hypertension, bounding pulse, jugular venous distention, crackles, shortness of breath, pulmonary edema, ascites, and initially increased urine output.

Chvostek's Sign and Trousseau's Sign

Clinical diagnostic signs indicating hypocalcemia and increased neuromuscular excitability.

Torsades de Pointes

A critical cardiac dysrhythmia associated with hypomagnesemia.