Fluid and Electrolyte Balance

• Fluid & electrolyte balance involves water and minerals in the body
• Disruptions lead to heart failure, kidney disease, and hypertension

Fluid Balance

• Equilibrium between fluid intake and output maintains hydration and fluid distribution
• Regulates blood pressure, nutrient transport, waste elimination, and temperature control
• Management of fluids is critical for treatment

Factors Contributing to Fluid Balance

• Hydrostatic pressure pushes fluid out of blood vessels into tissues
• Oncotic pressure pulls fluid into blood vessels from tissues
• Capillary permeability regulates fluid passage between blood and tissues
• The lymphatic system drains excess fluid back into the bloodstream
• ADH, aldosterone, and natriuretic peptides regulate fluid levels
• Fluid intake and output regulate fluid balance
• Sodium and potassium influence water movement
• Acid-base balance affects fluid distribution and function

Fluid Compartments

• Intracellular space contains fluid inside cells, about 60% of total body water, rich in potassium, phosphate, and magnesium
• Extracellular space contains fluid outside cells, about 40% of total body water, rich in sodium, chloride, and bicarbonate
• Intravascular space (plasma) contains fluid inside blood vessels, about 20% of extracellular fluid (ECF)
• Interstitial space contains fluid between cells, about 75% of ECF
• Transcellular fluid is in specialized compartments like cerebrospinal, synovial, and peritoneal fluid, about 5% of ECF

Fluid Shifts and Mechanisms

• Water movement between compartments occurs due to pressure or solute changes
• Purpose is to maintain balance, adjust hydration, and support nutrient/waste exchange
• Key mechanisms are hydrostatic pressure, oncotic pressure, and osmosis
• These mechanisms regulate fluid distribution between the intracellular and extracellular spaces

Hydrostatic Pressure

• The force exerted by blood against blood vessel walls
• It is the "push" from blood volume and flow
• Highest at the arterial end of capillaries and lowest at the venous end
• Pushes fluid out of blood vessels (intravascular space) into the tissues (interstitial space), facilitating nutrient exchange

Oncotic Pressure

• A force exerted by proteins, mainly albumin, that pulls water into the bloodstream
• "Pull" from proteins helps maintain fluid balance within blood vessels
• If albumin levels are low, oncotic pressure weakens, causing fluid to shift into surrounding tissues, leading to edema
• It pulls fluid from tissues (interstitial space) into blood vessels (intravascular space), maintaining proper fluid distribution

Normal Fluid Balance

• Hydrostatic and oncotic pressures work together in a push-pull system regulating fluid movement to maintain proper fluid balance and prevent edema
• Hydrostatic pressure pushes fluid out of blood vessels (intravascular) into tissues for nutrient exchange
• Oncotic pressure pulls fluid into blood vessels (intravascular) from tissues maintained by proteins like albumin
• At the arterial end, hydrostatic pressure is greater than oncotic pressure, pushing fluid into tissues
• At the venous end, hydrostatic pressure drops, and oncotic pressure pulls fluid back into capillaries

Disruptions in Fluid Balance

• High hydrostatic pressure, due to heart failure or high blood pressure, causes excess fluid to move into tissues, leading to edema
• Low oncotic pressure, due to low albumin, prevents fluid from returning to the capillaries, resulting in edema
• Heart failure causes high hydrostatic pressure pushing fluid into tissues
• Liver disease reduces albumin leading to low oncotic pressure, preventing fluid return to blood vessels
• Burns cause plasma proteins to leak from blood vessels, lowering oncotic pressure
• Renal failure results in the loss of albumin in urine (nephrotic syndrome), lowering oncotic pressure

Third-Spacing

• Fluid shifts into compartments not available for circulation or physiological use, such as inflammation, burns, or injury
• Fluid moves out of vascular and interstitial spaces into non-functional areas
• This includes ascites (abdomen), pleural effusion (pleural cavity), and pericardial effusion (pericardial sac)
• Trapped fluid is unavailable for circulation or nutrient exchange, which increases the risk of hypovolemia

Fluid Imbalances

• Fluid overload occurs when the body retains more fluid than needed, leading to edema and increased heart workload
• Fluid deficit (dehydration) occurs when there is insufficient fluid intake or excessive fluid loss, leading to hypovolemia

Indicators of Fluid Overload and Deficit

• Fluid overload signs include rapid weight gain and edema (swelling of feet, ankles, or lungs)
• Fluid overload also includes shortness of breath (dyspnea, fluid accumulation in lungs) and increased blood pressure
• Fluid deficit (dehydration) signs include thirst (early sign), dry skin and mucous membranes
• Fluid deficit also presents signs of low blood pressure, tachycardia (compensatory response), and decreased urine output (dark-colored urine)

Antidiuretic Hormone (ADH)

• ADH (vasopressin) increases water retention by kidneys, conserving fluid
• The release of ADH is triggered by high blood osmolarity such as dehydration
• In fluid deficit, ADH increases to retain water
• In fluid overload, ADH decreases to excrete excess water

IV Fluids

• Crystalloids and colloids are the two primary types of IV fluids
• Both restore fluid balance, treat dehydration and shock, and correct electrolyte imbalances
• Both help manage fluid shifts, osmotic pressure, and blood volume

Crystalloids

• IV fluids that have small molecules, easily moving between compartments
• Examples include normal saline and lactated Ringer’s
• Typically used for short-term intravascular volume expansion

Colloids

• IV fluids that have larger molecules, staying in the vascular space
• Colloids pull fluid into vessels
• Examples include albumin
• Used for rapid volume expansion with longer intravascular effect
• Used when crystalloids are insufficient due to their cost and potential side effects

Types of Crystalloid Solutions

• Isotonic are examples that include 0.9% Normal Saline and Lactated Ringer’s used for fluid resuscitation and electrolyte replacement
• Hypotonic examples are 0.45% NaCl and D5W, can be used for rehydration or replacing free water
• Hypertonic examples are 3% NaCl and D5LR, can be used for severe hyponatremia or to expand intravascular volume.
• They restore fluid balance by affecting the ECF and ICF, providing hydration and supporting electrolyte management

Types of Colloid Solutions

• Albumin is a natural protein used to expand blood volume
• Dextran and Hetastarch are synthetic colloids, helping maintain intravascular volume
• Whole blood contains all blood components, rarely used
• Packed red blood cells are for acute anemia and blood loss
• Platelets are for low platelet count
• Fresh frozen plasma replaces clotting factors
• Colloids are more effective in volume expansion, by drawing water into the blood vessels, ideal for hypovolemia or shock

Electrolytes

• Electrolytes are electrically charged minerals found in body fluids
• Electrolytes enable electrical impulses for nerve signaling, including cardiac conduction to regulate heart rhythm
• Crucial for proper muscle function including the heart, helping to maintain pH balance and regulating water movement

Key Electrolytes

• Sodium (Na⁺)
• Potassium (K⁺)
• Chloride (Cl⁻)
• Bicarbonate (HCO₃⁻)
• Calcium (Ca²⁺)
• Magnesium (Mg²⁺)
• Phosphate (PO₄³⁻)

Electrolytes & Fluid Balance

• Sodium and potassium regulate osmotic pressure, controlling fluid movement
• Hypernatremia drives water into the bloodstream, leading to dehydration
• Hyponatremia moves into the cells, leading to edema
• Changes in fluid volume dilute or concentrate electrolytes
• Fluid overload dilutes sodium and potassium leading to hyponatremia or hypokalemia
• Dehydration concentrates sodium leading to hypernatremia

Sodium

• Major extracellular cation, maintaining fluid balance, nerve transmission, and BP regulation
• Hyponatremia is when values are less than 135 mEq/L that results from increased intake due to SIADH, diuretic use, and heart/liver failure
• Hyponatremia results in headache, confusion, nausea, muscle cramps, and seizures
• Treatment involves fluid restriction (for SIADH), hypertonic saline (3% NaCl) for severe cases, diuretics (for overload), and correcting underlying cause.
• Hypernatremia is when values are greater than 145 mEq/L as a result of dehydration, hyperaldosteronism, Cushing’s, and DI
• Hypernatremia presents signs that include thirst, dry mouth, irritability, and muscle twitching.
• Treatment involves hypotonic fluids (0.45% NaCl), oral fluids (if able), treating the underlying cause, and frequent monitoring

Potassium

• Major intracellular cation necessary for nerve transmission, muscle contraction, cardiac rhythm, fluid balance and acid-base regulation
• Hypokalemia is when K+ is less than 3.5 mEq/L, caused by diuretics, vomiting, and diarrhea
• Signs and symptoms include fatigue, muscle weakness, leg cramps, constipation, and abnormal heart rhythms like U waves, PVCs, and Torsades de Pointes
• Oral or IV potassium supplementation is the treatment, never as a bolus. Hyperkalemia is when K+ is greater than 5.0 mEq/L due to renal failure, potassium-sparing diuretics, and acidosis
• Signs and symptoms include muscle weakness, fatigue, palpitations, irregular heart rhythms (e.g., peaked T waves, widened QRS), nausea, and vomiting
• Treatment involves calcium gluconate, insulin/dextrose, sodium bicarbonate, furosemide, or dialysis if severe.

Chloride

• Major extracellular anion maintaining osmotic pressure and fluid balance, by working with sodium
• Hypochloremia is when Cl- is less than 98 mEq/L due to vomiting, metabolic alkalosis, and diuretics
• Hypochloremia signs include muscle twitching, weakness, slow, shallow breathing and respiratory distress/confusion
• Treatment involves chloride-rich fluids, 0.9% NaCl or LR.
• Hyperchloremia is when Cl- exceeds 108 mEq/L caused by dehydration, renal failure, and respiratory acidosis
• Symptoms include tachypnea, hypertension, lethargy, and deep/rapid breathing (Kussmaul respirations)
• Treatment involves hypotonic fluids and sodium bicarbonate

Bicarbonate

• Key role in acid-base balance
• It buffers to maintain pH with carbonic acid maintaining homeostasis
• Metabolic Acidosis (Low HCO3- < 22 mEq/L) results from Diarrhea, renal failure, and metabolic acidosis
• Signs are rapid breathing (Kussmaul respirations), fatigue, confusion and Nausea/vomiting
• Treatment is sodium bicarbonate IV to neutralize acid.
• Metabolic Alkalosis (High HCO3- > 28 mEq/L) results from Vomiting, metabolic alkalosis, comp. resp acidosis
• Signs include Slow/shallow breathing, confusion/dizziness and Muscle twitching, tetany -Correction of underlying cause, potassium chloride, and fluids balance electrolytes.

Calcium

• Essential for bone tooth formation, neuromuscular function, and blood clotting
• Helps maintain cellular function and cardiac rhythm
• Hypocalcemia (Ca++ < 8.5 mg/dL) results from hypoparathyroidism, vit D deficiency, and CKD
• Symptoms include Muscle cramps tetany, Numbness around the mouth extremities, and Positive Chvostek's/Trousseau's signs
• Treatment is Calcium gluconate or calcium chloride IV.
• Hypercalcemia (Ca++ > 10.5 mg/dL) results from Hyperparathyroidism, cancer, and excessive vit D intake
• Symptoms are Lethargy/weakness, Nausea/vomiting and Kidney stones/bone pain
• Treatment: Hydration with IV fluids, bisphosphonates, and calcitonin

Magnesium

• Important for neuromuscular transmission, enzyme/ATP production and regulating cardiac rhythm/muscle function.
• Hypomagnesemia (Mg++ < 1.5 mg/dL) results from Alcohol Use Disorder, malnutrition, and diuretics
• Symptoms are Muscle cramps/tremors, Seizures/irritability, and Cardiac arrhythmias (cardiac arrhythmias)
• Treatment is Magnesium sulfate IV or oral magnesium supplements.
• Hypermagnesemia (Mg++ > 2.5 mg/dL) results from Renal failure, excessive Mg supplementation, and antacids/laxatives
• Symptoms:Hypotension/bradycardia, Respiratory depression and Muscle weakness/drowsiness
• Treatment is Discontinue magnesium, calcium gluconate, and possibly dialysis.

Phosphate

• Key component of ATP/DNA/RNA, Bone health, acid-base balance, energy metabolism
• Hypophosphatemia (PO4- < 2.5 mg/dL) results from Malnutrition, Alcohol Use Disorder, and hyperparathyroidism
• Symptoms:Muscle weakness/fatigue, Irritability confusion and Bone pain
• Treatment: Oral or IV phosphate supplementation.
• Hyperphosphatemia (PO4- > 4.5 mg/dL) results from Renal failure, hypoparathyroidism and excessive intake
• Symptoms:Itchy skin/muscle cramps, Calcium deposits, Symptoms of hypocalcemia
• Treatment: Treat underlying cause, phosphate binders, and dietary restrictions.

Fluid & Electrolyte Imbalance Treatment

• Edema, dehydration, and third spacing stem from electrolyte disturbances - Correct electrolyte imbalances, rehydrate, and manage IV volume
• Administer oral/IV fluid replacement for dehydration/third spacing
• Administer diuretics to increase urine electrolyte output, manage edema, and treat heart failure/hypertension while monitoring electrolytes, especially potassium, with careful avoidance when dehydrated

Types of Diuretics

• Loop Diuretics (e.g., Furosemide) blocks Na+/Cl¯ reabsorption, treats fluid overload
• Thiazides (e.g., HCTZ) blocks Na+/Cl reabsorption, treats chronic hypertension and mild fluid retention
• K⁺-Sparing (e.g., Spironolactone) blocks aldosterone while retaining potassium and treats edema when K⁺ conservation is needed
• Carbonic Anhydrase Inhibitors (e.g., Acetazolamide) blocks carbonic anhydrase and treats glaucoma, altitude sickness, or alkalosis
• Osmotic Diuretics (e.g., Mannitol) increases osmotic pull and shifts fluid, treating cerebral edema

Furosemide (Loop Diuretic)

• Inhibits reabsorption of sodium and chloride in the loop of Henle and distal tubule, promoting water excretion.
• Treats edema (heart failure, liver cirrhosis, renal disease), pulmonary edema, hypertension.
• Side Effects: Hypokalemia, hyponatremia, dehydration, hypotension, ototoxicity, dizziness
• slowly (IV) to prevent ototoxicity, monitor electrolyte and renal function, increase potassium, and administer in the morning to avoid nocturia.

Hydrochlorothiazide (Thiazide Diuretic)

• Inhibits sodium and chloride reabsorption in the distal renal tubule, increasing excretion of Na, Cl, and water
• Treats hypertension, mild edema and kidney stone prevention
• Side effects include hypokalemia, hyponatremia,hyperglycemia, hyperuricemia, photosensitivity, and dizziness
• Monitor blood pressure, electrolytes and glucose levels, educate on sun protection, and administer in the morning to enhance efficacy.

Spironolactone (Potassium-Sparing Diuretic)

• Antagonizes aldosterone in the distal renal tubules, promoting sodium and water excretion while conserving potassium
• Treats heart failure, hypertension, edema, primary hyperaldosteronism, acne, and hirsutism
• Side effects include hyperkalemia, gynecomastia and menstrual irregularities, dizziness, and rash
• Monitor potassium levels, and avoid potassium supplements and substitutes. Take with food to reduce irritation

Mannitol (Osmotic Diuretic)

• Increases osmotic pressure in the renal tubules, drawing water into the tubules promoting diuresis.
• Treats cerebral edema, increased intraocular pressure (glaucoma).
• Side Effects: Hyponatremia, hypokalemia, dehydration, pulmonary edema, and headache.
• Administer through a filter, monitor vital signs and electrolytes, and assess for pulmonary edema

Acetazolamide (Carbonic Anhydrase Inhibitor)

• Inhibits carbonic anhydrase, reducing sodium bicarbonate reabsorption in the proximal tubule, which leads to electrolyte excretion.
• Treats glaucoma, altitude sickness, metabolic alkalosis, and epilepsy
• Side Effects: Hypokalemia, hyponatremia, metabolic acidosis, kidney stones, drowsiness, and tingling sensation.
• Monitor electrolytes and renal function, promote hydration