Fluid & Electrolyte Balance

Vocabulary flashcards covering key terms, normal ranges, electrolyte functions, hormonal controls, and clinical signs from the Fluid & Electrolyte Balance lecture notes.

Intracellular Fluid (ICF)

Fluid located inside the cells comprising about $2/3$ of total body water, where the major electrolyte is potassium ($K^+$), along with magnesium, phosphate, and protein.

Extracellular Fluid (ECF)

Fluid located outside the cells comprising about $1/3$ of total body water, divided into intravascular (plasma) and interstitial fluid, with sodium ($Na^+$) as its major electrolyte.

Intracellular vs. Extracellular Electrolyte Locations

ICF contains $K^+$, $Mg^{2+}$, phosphate, and protein; ECF contains $Na^+$, $Ca^{2+}$, $Cl^-$, and $HCO_3^-$.

Sodium ($Na^+$)

The primary extracellular electrolyte with a normal range of $135-145$ mEq/L that controls water balance and helps nerve and muscle function.

Potassium ($K^+$)

The primary intracellular electrolyte with a normal range of $3.5-5.0$ mEq/L that regulates heart rhythm, muscle contraction, and nerve function.

Calcium ($Ca^{2+}$)

An electrolyte with a normal range of $\sim 8.6-10.2\,mg/dL$ essential for bones and teeth, muscle contraction, nerve transmission, blood clotting, and cardiac function.

Magnesium ($Mg^{2+}$)

An electrolyte with a normal range of $\sim 1.7-2.2\,mg/dL$ involved in muscle and nerve function, cardiac rhythm, and regulating other electrolytes.

Phosphate ($PO_4^{3-}$)

An electrolyte with a normal range of $\sim 2.5-4.5\,mg/dL$ necessary for energy production, bone formation, and cellular function, having an inverse relationship with calcium.

Chloride ($Cl^-$)

An electrolyte with a normal range of $\sim 98-106$ mEq/L that works closely with sodium to control fluid balance and acid-base balance.

Bicarbonate ($HCO_3^-$)

An electrolyte with a normal range of $22-26$ mEq/L primarily responsible for acid-base balance.

Antidiuretic Hormone (ADH)

A hormone released during dehydration that signals the kidneys to retain water, leading to concentrated urine and increased blood volume.

Aldosterone

A hormone acting on the kidneys to retain sodium and water while excreting potassium, which increases blood volume and blood pressure.

Renin-Angiotensin-Aldosterone System (RAAS)

A physiological pathway (Renin \rightarrow Angiotensin I \rightarrow Angiotensin II \rightarrow Aldosterone) that increases sodium retention, water retention, and blood pressure.

Fluid Volume Deficit

A state of dehydration (dry and low) characterized by thirst, dry mucous membranes, poor skin turgor, decreased dark urine output, weight loss, tachycardia, hypotension, weakness, and risk of hypovolemic shock.

Fluid Volume Excess

A state of fluid overload (wet and swollen) characterized by edema, weight gain, crackles, dyspnea, JVD, bounding pulse, hypertension, pulmonary edema, and ascites.

Hyponatremia

A serum sodium level $< 135$ mEq/L causing cellular fluid shift and brain swelling, manifested by headache, confusion, lethargy, nausea, muscle cramps, and seizure risk.

Hypernatremia

A serum sodium level $> 145$ mEq/L causing cellular dehydration, manifested by extreme thirst, dry mucous membranes, restlessness, irritability, confusion, muscle twitching, and seizures.

Hypokalemia

A serum potassium level $< 3.5$ mEq/L caused by diuretics, vomiting, diarrhea, or NG suction, manifesting as muscle weakness, fatigue, cramps, constipation, dysrhythmias, flattened T waves, and U waves on ECG.

Hyperkalemia

A serum potassium level $> 5.0$ mEq/L caused by kidney failure, ACE inhibitors, ARBs, or tissue damage, manifesting as muscle weakness, paresthesias, dysrhythmias, tall peaked T waves on ECG, and potential cardiac arrest.

Hypocalcemia

A serum calcium level $< 8.6\,mg/dL$ characterized by numbness/tingling, muscle cramps, tetany, hyperreflexia, seizures, Chvostek's sign, and Trousseau's sign.

Hypercalcemia

A serum calcium level $> 10.2\,mg/dL$ characterized by "stones, bones, groans" (kidney stones, bone pain, constipation, abdominal pain, weakness, confusion, and lethargy).

Hypomagnesemia

A serum magnesium level $< 1.7\,mg/dL$ manifesting as tremors, muscle cramps, hyperreflexia, tetany, seizures, and dysrhythmias.

Hypermagnesemia

A serum magnesium level $> 2.2\,mg/dL$ causing generalized depression of systems, manifested by lethargy, muscle weakness, hypotension, bradycardia, decreased deep tendon reflexes, and respiratory depression.

Chvostek's Sign

A clinical indication of hypocalcemia defined by facial muscle twitching when the facial nerve is tapped.

Trousseau's Sign

A clinical indication of hypocalcemia defined by carpopedal spasm induced by inflating a blood pressure cuff above systolic pressure.

Normal Electrolyte & Kidney Lab Test Values

Reference values for diagnostic laboratory testing of serum electrolytes, Blood Urea Nitrogen (BUN), and Creatinine.

BUN & Creatinine

Laboratory diagnostic values used to evaluate kidney function and hydration, with normal BUN at $\sim 10-20\,mg/dL$ and normal creatinine at $\sim 0.6-1.3\,mg/dL$.

Adult Minimum Urine Output

The essential baseline urine production threshold for an adult, required to be $\ge 30\,mL/hr$ or approximately $0.5\,mL/kg/hr$.

Calcium Gluconate

A medication administered in severe hyperkalemia to protect and stabilize the cardiac membrane.