Fluid and Electrolyte Balance

• Fluid and electrolyte balance is the regulation of body fluids and electrolytes, crucial for maintaining homeostasis.
• Disruptions in this balance can lead to various health problems.

Body Fluids

• Total Body Water (TBW) varies based on age, sex, and body fat, generally decreasing with age.
• Infants possess a higher percentage of TBW, making them more susceptible to fluid volume changes.
• Men generally have more TBW than women due to higher muscle mass.
• Fat contains less water than muscle; therefore, individuals with more body fat have a lower percentage of TBW.

Fluid Compartments

• Intracellular Fluid (ICF) is the fluid within cells, making up about two-thirds of TBW.
• Extracellular Fluid (ECF) is the fluid outside cells, comprising about one-third of TBW.
  • Interstitial Fluid fills the space between cells.
  • Intravascular Fluid is the plasma within blood vessels.
  • Transcellular Fluid is present in specialized compartments like cerebrospinal fluid and synovial fluid.

Fluid Movement

• Osmosis involves the movement of water across a semipermeable membrane from an area of lower solute concentration to one of higher concentration.
  • Osmotic pressure is the force that draws water into the area with higher solute concentration.
• Diffusion is the movement of solutes from an area of higher concentration to an area of lower concentration.
• Filtration describes the movement of water and solutes from an area of higher hydrostatic pressure to an area of lower hydrostatic pressure.
  • Hydrostatic pressure refers to the force exerted by a fluid against a wall.
• Active Transport is the movement of molecules against a concentration gradient, requiring energy (ATP).

Fluid Intake

• Fluid intake occurs primarily through drinking fluids, but also from food and metabolic processes.
• The thirst mechanism is regulated by the hypothalamus in response to changes in plasma osmolarity and blood volume.

Fluid Output

• Kidneys are the primary regulators of fluid balance through urine production.
• Skin eliminates fluid through sensible (sweat) and insensible (not noticeable) perspiration.
• Lungs expel water vapor during respiration.
• The gastrointestinal tract excretes fluid through feces.
• Abnormal fluid losses can occur through vomiting, diarrhea, hemorrhage, and wound drainage.

Hormonal Regulation

• Antidiuretic Hormone (ADH) is released by the posterior pituitary in response to dehydration or increased plasma osmolarity.
  • ADH causes the kidneys to reabsorb water, reducing urine output.
• Aldosterone is released by the adrenal cortex in response to decreased blood volume or increased potassium levels.
  • Aldosterone causes the kidneys to reabsorb sodium and water, and excrete potassium.
• Atrial Natriuretic Peptide (ANP) and Brain Natriuretic Peptide (BNP) are released by the heart in response to increased blood volume and blood pressure.
  • ANP and BNP cause the kidneys to excrete sodium and water, decreasing blood volume and blood pressure.

Fluid Volume Deficit (Hypovolemia)

• Causes include:
  • Excessive fluid loss (e.g., vomiting, diarrhea, hemorrhage, burns).
  • Inadequate fluid intake.
  • Third-space fluid shift (fluid accumulation in areas where it is not readily available, such as ascites).
• Signs and Symptoms include:
  • Weight loss.
  • Decreased skin turgor.
  • Dry mucous membranes.
  • Hypotension.
  • Tachycardia.
  • Concentrated urine.
  • Weakness.
• Nursing Management involves:
  • Fluid replacement (oral or IV).
  • Monitoring vital signs.
  • Assessing urine output.
  • Assessing skin turgor and mucous membranes.

Fluid Volume Excess (Hypervolemia)

• Causes include:
  • Excessive fluid intake.
  • Heart failure.
  • Kidney failure.
  • Excessive sodium intake.
• Signs and Symptoms include:
  • Weight gain.
  • Edema.
  • Hypertension.
  • Tachycardia.
  • Jugular vein distension.
  • Shortness of breath.
  • Crackles in lungs.
• Nursing Management involves:
  • Fluid restriction.
  • Sodium restriction.
  • Use of Diuretics.
  • Monitoring vital signs.
  • Assessing edema.
  • Monitoring respiratory status.

Electrolytes

• Electrolytes are substances that dissociate into ions (charged particles) when dissolved in water.
• Cations are positively charged ions (e.g., sodium, potassium, calcium, magnesium).
• Anions are negatively charged ions (e.g., chloride, bicarbonate, phosphate).
• Electrolytes are essential for maintaining fluid balance, nerve impulse transmission, muscle contraction, and other bodily functions.

Sodium (Na+)

• Normal Range: 135-145 mEq/L.
• Major cation in ECF.
• Regulates fluid balance, nerve impulse transmission, and muscle contraction.
• Sources: Diet (e.g., table salt, processed foods).
• Excretion: Primarily by the kidneys.

Hyponatremia (Low Sodium)

• Causes:
  • Excessive water intake.
  • Sodium loss (e.g., vomiting, diarrhea, diuretics).
  • Syndrome of Inappropriate Antidiuretic Hormone (SIADH).
• Signs and Symptoms:
  • Headache.
  • Confusion.
  • Nausea.
  • Muscle weakness.
  • Seizures.
• Nursing Management:
  • Sodium replacement (oral or IV).
  • Fluid restriction (if hypervolemic).
  • Monitoring neurological status.

Hypernatremia (High Sodium)

• Causes:
  • Dehydration.
  • Excessive sodium intake.
  • Diabetes insipidus.
• Signs and Symptoms:
  • Thirst.
  • Dry mucous membranes.
  • Confusion.
  • Seizures.
• Nursing Management:
  • Fluid replacement (oral or IV).
  • Sodium restriction.
  • Monitoring neurological status.

Potassium (K+)

• Normal Range: 3.5-5.0 mEq/L.
• Major cation in ICF.
• Regulates nerve impulse transmission, muscle contraction, and cardiac function.
• Sources: Diet (e.g., bananas, oranges, potatoes).
• Excretion: Primarily by the kidneys.

Hypokalemia (Low Potassium)

• Causes:
  • Potassium loss (e.g., vomiting, diarrhea, diuretics).
  • Inadequate potassium intake.
• Signs and Symptoms:
  • Muscle weakness.
  • Cardiac arrhythmias.
  • Fatigue.
  • Constipation.
• Nursing Management:
  • Potassium replacement (oral or IV).
  • Monitoring cardiac status.

Hyperkalemia (High Potassium)

• Causes:
  • Kidney failure.
  • Potassium-sparing diuretics.
  • Excessive potassium intake.
• Signs and Symptoms:
  • Muscle weakness.
  • Cardiac arrhythmias.
  • Nausea.
• Nursing Management:
  • Potassium restriction.
  • Medications to shift potassium into cells (e.g., insulin, sodium bicarbonate).
  • Dialysis (in severe cases).
  • Monitoring cardiac status.

Calcium (Ca2+)

• Normal Range: 8.5-10.5 mg/dL.
• Important for bone health, nerve impulse transmission, muscle contraction, and blood clotting.
• Sources: Diet (e.g., dairy products, leafy green vegetables).
• Regulation: Parathyroid hormone (PTH) and calcitonin.

Hypocalcemia (Low Calcium)

• Causes:
  • Hypoparathyroidism.
  • Vitamin D deficiency.
  • Kidney failure.
• Signs and Symptoms:
  • Muscle cramps.
  • Tetany.
  • Numbness and tingling.
  • Seizures.
• Nursing Management:
  • Calcium replacement (oral or IV).
  • Monitoring neurological status.

Hypercalcemia (High Calcium)

• Causes:
  • Hyperparathyroidism.
  • Cancer.
• Signs and Symptoms:
  • Muscle weakness.
  • Confusion.
  • Nausea.
• Nursing Management:
  • Fluid replacement.
  • Medications to decrease calcium levels.
  • Monitoring neurological status.

Magnesium (Mg2+)

• Normal Range: 1.5-2.5 mEq/L.
• Important for muscle and nerve function, enzyme reactions, and bone health.
• Sources: Diet (e.g., nuts, green vegetables).
• Excretion: Primarily by the kidneys.

Hypomagnesemia (Low Magnesium)

• Causes:
  • Malnutrition.
  • Alcoholism.
  • Diarrhea.
• Signs and Symptoms:
  • Muscle weakness.
  • Tremors.
  • Seizures.
• Nursing Management:
  • Magnesium replacement (oral or IV).
  • Monitoring neurological status.

Hypermagnesemia (High Magnesium)

• Causes:
  • Kidney failure.
  • Excessive magnesium intake.
• Signs and Symptoms:
  • Muscle weakness.
  • Hypotension.
  • Bradycardia.
• Nursing Management:
  • Calcium gluconate (to antagonize magnesium effects).
  • Dialysis (in severe cases).
  • Monitoring cardiac status.

Acid-Base Balance

• Regulation of hydrogen ion (H+) concentration in body fluids.
• Normal pH range: 7.35-7.45.
• Acidosis: pH < 7.35.
• Alkalosis: pH > 7.45.

Acid-Base Buffers

• Chemical systems that resist changes in pH.
• Bicarbonate buffer system: Major buffer in ECF.
• Phosphate buffer system: Important in ICF.
• Protein buffer system: Found in both ECF and ICF.

Respiratory Regulation

• Lungs regulate CO2 levels in the blood.
• Increased respiration rate decreases CO2 levels, increasing pH.
• Decreased respiration rate increases CO2 levels, decreasing pH.

Renal Regulation

• Kidneys regulate bicarbonate (HCO3-) levels in the blood.
• Kidneys can excrete or reabsorb HCO3- to maintain acid-base balance.
• Kidneys can also excrete H+.

Acidosis

• Respiratory Acidosis:
  • Cause: Hypoventilation, leading to increased CO2 levels.
  • Compensation: Kidneys retain HCO3-.
• Metabolic Acidosis:
  • Cause: Loss of HCO3- or accumulation of acid.
  • Compensation: Lungs increase respiration rate to decrease CO2 levels.

Alkalosis

• Respiratory Alkalosis:
  • Cause: Hyperventilation, leading to decreased CO2 levels.
  • Compensation: Kidneys excrete HCO3-.
• Metabolic Alkalosis:
  • Cause: Gain of HCO3- or loss of acid.
  • Compensation: Lungs decrease respiration rate to increase CO2 levels.