Understanding Fluid Volume and Balance

Fluid Volume

• Water supports digestion, absorption, circulation, and excretion.
• Body fluids are distributed between the intracellular (ICF) and extracellular (ECF) compartments.
• The extracellular compartment includes interstitial, intravascular, and transcellular fluids.

Movement of Fluids and Electrolytes

• Active transport requires energy.
• Passive transport includes diffusion, filtration, and osmosis.

Maintaining Fluid Balance

• Thirst response, hypothalamus function, and osmosis are important for maintaining fluid balance.

Renin-Angiotensin-Aldosterone Mechanism

• Renin is released by the kidneys when blood pressure is low or there is a drop in volume.
• Renin acts on angiotensin, forming angiotensin I.
• ACE (angiotensin-converting enzyme) is released from the lungs.
• ACE acts on angiotensin I to form angiotensin II.
• Angiotensin II vasoconstricts blood vessels.
• Angiotensin II stimulates aldosterone release from the adrenal gland, which prompts the kidneys to reabsorb salt (NaCl) and water.

Fluid Volume Imbalances

• Fluid volume imbalances can be deficits or excesses.
• Both deficits and excesses manifest with specific signs and symptoms.
• Diagnosis and appropriate interventions can resolve imbalances.

Types of Diuretics and Adverse Effects

• Thiazide diuretics, like hydrochlorothiazide (Microzide), can cause hyponatremia, hypokalemia, hyperglycemia, and potassium wasting.
• Loop diuretics, like furosemide (Lasix), can cause hyponatremia, hypokalemia, hypotension, ototoxicity, hyperglycemia, and potassium wasting.
• Potassium-sparing diuretics, like spironolactone (Aldactone), can cause hyperkalemia and potassium sparing.

Fluid Volume Excess: Hypervolemia

• Hypervolemia manifests as weight gain, shortness of breath, orthopnea, pulmonary congestion, adventitious breath sounds, changes in mental status, jugular vein distention, oliguria, and edema.

Scenario: Mr. Peters

• Mr. Peters is a 32-year-old with a congenital heart problem, recovering from acute congestive heart failure and fluid excess.
• His blood pressure is elevated, his pulse is bounding, and he's having trouble breathing.

Scenario: Mrs. Levitt

• Mrs. Levitt is a 92-year-old widow in a nursing home for 4 years.
• Her urine smells bad, her heart feels like it is beating faster than usual, and dehydration is suspected.
• Her urine is dark amber with a strong odor.
• Vitals include a heart rate of 98 beats per minute, blood pressure of 126/74 mm Hg, respiratory rate of 20 per minute, and temperature of 99.2°F (37.3°C).

Normal Serum Electrolyte Values

• Sodium (Na): 135-145 mEq/L
• Potassium (K): 3.5-5.0 mEq/L
• Calcium (Ca): 9-11 mg/dL
• Magnesium (Mg): 1.5-2.5 mg/dL
• Chloride (Cl): 98-106 mEq/L
• Phosphate (HPO4): 2.4-4.5 mg/dL

Sodium Manifestations (Na- 135-145 mEq/L)

• Hypernatremia, with critical levels above 160 mEq/L, manifests as flushing, restlessness, irritability, increased blood pressure, edema, dry mouth, flushed skin, agitation, low-grade fever, and thirst.
• Hyponatremia, with critical levels below 110-120 mEq/L, manifests as stupor/coma, anorexia, nausea, vomiting, lethargy, tendon reflexes/hyperreflexia, limp muscles or twitching muscles, orthostatic hypotension, seizure, and stomach cramping.

Interventions to Correct Sodium Imbalances

• Hypernatremia is treated with oral or IV isotonic or hypotonic fluids, addressing the underlying cause, administering loop diuretics (as prescribed), monitoring intake and output, and avoiding rapid correction.
• Hyponatremia is managed by treating the underlying cause, restricting fluids if there is fluid overload, encouraging fluids and food high in Na+, administering IV isotonic or hypertonic fluids, and avoiding rapid correction.

Potassium Manifestations (K – 3.5-5 mEq/L)

• Hyperkalemia levels above 5.0 mEq/L and critically above 6.0 mEq/L causes muscle cramps/weakness, urine abnormalities, respiratory distress, dysrhythmias, ECG changes (tall peak T waves, prolonged QRS intervals), and reflexes-hyperreflexia and muscle twitching.
• Hypokalemia levels below 3.5 mEq/L and critically below 2.5 mEq/L results in lethargy, lethal cardiac arrhythmias, leg cramps, limp muscles, low shallow respirations, low blood pressure (hypotension), and less stool (constipation).

Interventions to Correct Potassium Imbalances

• Hyperkalemia treatments include limiting oral K+ intake, IV calcium gluconate, sodium polystyrene sulfonate (Kayexalate, PO or PR every 6 hours), 1 ampule of dextrose 50% (D50) and insulin 10 units IV, albuterol nebulizer, and hemodialysis.
• Hypokalemia treatments include oral replacement (K+ supplements, foods high in K+, potassium-sparing diuretics may be ordered), IV potassium and monitor K+ level frequently + NEVER PUSH IV POTASSIUM.

Calcium Manifestations (Ca 9-11mg/dL or 8.5-10.5 mg/dL)

• Hypercalcemia signs are bones, stones, groans, and moans.
• Hypocalcemia signs are convulsions, arrhythmias, tetany, Trousseau sign and Chvostek sign.

Interventions to Correct Calcium Imbalances

• Hypercalcemia can be treated with phosphate by mouth, hospitalization for cardiac monitoring, IV fluids to promote diuresis, loop diuretics, and hemodialysis.
• Hypocalcemia can be treated with calcium supplements, vitamin D supplements, and dietary changes.

Magnesium Manifestations (1.5 – 2.5 mEq/L)

• Hypermagnesemia Critical Level 3 mEq/L is not apparent until level is greater than 4 mEq/L, Bradycardia, Hypotension, Lethargy and Weakness.
• Hypomagnesemia Critical Level 0.5 mEq/L S/S are the same as Hypocalcemia : Convulsions, Arrhythmias, Tetany, Trouseau sign, Chvostek sign and Spasms.

Interventions to Correct Magnesium Imbalances

• Hypermagnesemia is treated with IV Calcium gluconate, Loop diuretics, IV fluids to help the kidneys excrete e Hemodialysis if severe.
• Hypomagnesemia is treated to Replace magnesium IV replacement e Cardiac Monitoring.