Fluid, Electrolytes, and Acid-Base Balance

Objectives

• Identify risk factors for fluid and electrolyte imbalances.

• Discuss the movement of fluid between intracellular and extracellular spaces.

• Identify risk factors for fluid and electrolyte imbalances in clients in the healthcare setting.

• Identify assessment findings when a client has a fluid or electrolyte imbalance.

• Differentiate between isotonic, hypotonic, and hypertonic solutions.

• Interpret laboratory findings to determine fluid or electrolyte imbalances and acid-base balance in clients.

• Implement nursing interventions for clients with fluid and electrolyte imbalances and acid-base imbalances in the healthcare setting.

• Evaluate the effectiveness of nursing care provided to a client with fluid and electrolyte and acid-base imbalances.

Fluid and Electrolyte Compartments

• ICF (Intracellular Fluid) and ECF (Extracellular Fluid)
    - ECF includes intravascular and interstitial fluids.

• Electrolytes:
    - Cations (+): Sodium (Na⁺), Potassium (K⁺)

Fluid Movement in the Body

• Basic Principles:
    - Particles move from low to high concentration utilizing energy (ATP).
    - Particles move from high to low concentration through processes such as diffusion.
    - Water Movement:
      - Water follows sodium (
   ext{, and fluid moves due to hydrostatic pressure})

Mechanisms of Movement

• Active Transport: Movement of substances against a concentration gradient using energy.

• Diffusion: Movement of particles from an area of higher concentration to lower concentration.

• Osmosis: Movement of water across a semi-permeable membrane.

• Filtration: Movement based on pressure differences.

Osmolality

• Definition: Measures blood concentration.

• Control: Managed by water balance regulated by the Antidiuretic Hormone (ADH).

• High Osmolality: Indicates dehydration; blood is concentrated due to insufficient water.

• Low Osmolality: Indicates overhydration; blood is diluted with excess water.

Tonicity of Solutions

• Hypertonic Solutions:
    - Fluid shifts into cells, causing cells to swell.
    - Occurs when sodium concentration is low, allowing water to enter cells.

• Isotonic Solutions:
    - No fluid shift; stays the same.

• Hypotonic Solutions:
    - Fluid shifts out of cells, causing cells to shrink.
    - Occurs when sodium concentration is high, promoting fluid to exit cells.

IV Fluids

• Types:
    - Hypotonic: 0.45% NS (½ NS) – fluid moves into cells.
    - Isotonic: 0.9% NS (Normal Saline), Lactated Ringer’s (LR) – fluid stays in vessels.
    - Hypertonic: 3% NS – fluid moves out of cells.
    - These fluids can be used in emergencies (BOLUS).

Assessment Findings - ECV (Effective Circulating Volume)

• ECV Excess (Fluid Overload):
    - Signs: Edema, rapid weight gain, elevated BP, crackles in lungs, shortness of breath (SOB), bounding pulses, orthopnea, activity intolerance, exhaustion.

• ECV Deficit (Fluid Deficit):
    - Signs: Poor skin turgor, dry mucous membranes, decreased BP, elevated pulse, confusion, brain fog, sleepiness, lack of tears/sweating/oral secretions, decreased urine output (dark/concentrated urine), dizziness, irritability, headache.

Risk Factors for Fluid and Electrolyte Imbalances

• Demographics: Infants, older adults.

• Environmental Factors: Heat, excessive sweating, physical activity, inaccurate I&O (input/output).

• Health Conditions: Kidney disease, heart failure, COPD, cancer, poor nutrition/starvation, alcohol use, difficulty chewing/swallowing, burns, hemorrhage, head injury, crush injury.

• Medical Treatments: NPO (nothing by mouth), diuretics, laxatives, blood pressure medications, IV fluids, oxygen therapy.

Sodium Overview

• Normal Range: 136–145 mEq/L (check facility reference).

• Function: Major extracellular electrolyte responsible for fluid balance, nerve impulse transmission, and muscle contraction.

• Regulation: Controlled largely by the Na/K pump and aldosterone.

Sodium Regulation and Key Relationships

• Regulatory Mechanisms:
    - Kidneys manage renal excretion and retention.
    - Aldosterone promotes sodium reabsorption and potassium excretion.
    - Antidiuretic Hormone (ADH) controls water reabsorption.

• Interactions: Works closely with chloride and potassium; influenced by fluid intake, diuretics, vomiting, and diarrhea.

Hyponatremia (Na⁺ < 136 mEq/L)

• Evaluation: Sodium levels must normalize (136–145 mEq/L); maintain patient alertness without seizures.

• Causes: Excess water intake, hypotonic IV fluids, excessive ADH (SIAHD), vomiting, diarrhea, diuretics, tap water enemas.

• Symptoms: Decreased level of consciousness (LOC), seizures.

• Laboratory Findings: Low sodium and osmolality.

• Plan/Interventions: Restore sodium gradually, prevent neurologic complications, ensure patient safety. Restrict free water, stop hypotonic IV fluids, administer hypertonic saline (3% NaCl) for severe cases, closely monitor neuro status and I&O.

Hypernatremia (Na⁺ > 145 mEq/L)

• Causes: Dehydration, vomiting, diarrhea, lack of water intake, ADH deficiency.

• Symptoms: Intense thirst, dry mucous membranes, decreased LOC, seizures.

• Laboratory Findings: High sodium, high osmolality.

• Plan/Interventions: Aim to reduce sodium gradually to ≤145 mEq/L, restore normal hydration. Encourage oral water intake, administer hypotonic IV solutions, monitor neuro status and daily weights.

Potassium (K⁺) Overview

• Normal Range: 3.5–5.0 mEq/L (check agency reference).

• Function: Major intracellular electrolyte; affects cardiac rhythm, nerve transmission, and muscle contractility; inversely related to sodium.

• Regulation: Controlled by aldosterone, kidneys, and insulin; impacted by dietary intake.

• Key Dietary Sources: Bananas, oranges, tomatoes, spinach, potatoes, meats.

Hypokalemia (K⁺ < 3.5 mEq/L)

• Assessment/Diagnosis: Caused by vomiting, diarrhea, potassium-wasting diuretics, poor diet. Symptoms include weakness, dysrhythmias, constipation, decreased bowel sounds. Labs reveal low potassium and possible metabolic alkalosis.

• Planning/Interventions: Goal is to increase potassium to 3.5–5.0 mEq/L. Administer oral or IV potassium as prescribed. Encourage potassium-rich foods; closely monitor ECG and potassium levels.

Hyperkalemia (K⁺ > 5.0 mEq/L)

• Assessment: Causes include kidney dysfunction, potassium-sparing diuretics, and acidosis. Symptoms encompass irritability, cramping, diarrhea, ECG changes.

• Diagnosis: Risk of decreased cardiac output related to altered cardiac rhythm and injury risk related to muscle weakness.

• Planning/Interventions: Goal to lower potassium to ≤5.0 mEq/L, administer loop diuretics or insulin with glucose as ordered, monitor ECG continuously.

Calcium Overview

• Normal Range: 9.0–10.5 mg/dL (verify facility range).

• Functions: Essential for bone and teeth structure, muscle contraction, nerve transmission, and blood clotting. Requires vitamin D for absorption.

Calcium Regulation and Key Relationships

• Regulation: Governed by parathyroid hormone (raises calcium), calcitonin (lowers calcium), and vitamin D (promotes absorption).

• Inverse Relationship: Calcium and phosphorus.

Hypocalcemia (Ca²⁺ < 9.0 mg/dL)

• Assessment: Caused by hypoparathyroidism, vitamin D deficiency, renal disease. Symptoms include tingling, cramps, tetany, Chvostek’s and Trousseau’s signs.

• Interventions: Administer calcium as ordered, ensure vitamin D intake; monitor ECG and treat causes of deficiency.

Hypercalcemia (Ca²⁺ > 10.5 mg/dL)

• Assessment: Associated with hyperparathyroidism, malignancy, immobility, vitamin D excess. Symptoms include nausea, constipation, confusion, muscle weakness.

• Interventions: Limit calcium intake, encourage fluids, administer phosphate supplements or diuretics as needed.

Magnesium Overview

• Normal Range: 1.3–2.1 mg/dL (verify facility range).

• Functions: Supports cardiac rhythm, neuromuscular function; cofactor for enzyme and ATP activity. Dietary sources include leafy vegetables, nuts, and chocolate.

Hypomagnesemia (Mg²⁺ < 1.3 mg/dL)

• Assessment: Causes include diuretics, chronic alcoholism, diarrhea; symptoms range from nausea to seizures. Labs show low magnesium and possibly low potassium.

• Interventions: Raise magnesium to ≥1.5 mg/dL, administer supplements, monitor ECG and DTRs.

Hypermagnesemia (Mg²⁺ > 2.1 mg/dL)

• Assessment: Caused by renal failure or excess magnesium intake. Symptoms include bradycardia, lethargy, muscle weakness.

• Interventions: Decrease magnesium levels; consider diuretics if kidneys function adequately, continue cardiac monitoring.

Acid-Base Balance

• Normal Values:
    - pH: 7.35–7.45
    - PaCO₂: 35–45 mmHg (acid, lungs)
    - HCO₃: 22–26 mEq/L (base, kidneys)

pH and Acid-Base Status

• Acidosis: pH < 7.35; excess hydrogen ions (H⁺).

• Alkalosis: pH > 7.45; insufficient hydrogen ions (H⁺).

Assessment of Acid-Base Status

• PaCO₂ (Respiratory Number): High levels (hypercapnia) indicate acidosis; low levels (hypocapnia) indicate alkalosis.

• HCO₃⁻ (Metabolic Number): Low bicarbonate indicates metabolic acidosis; high indicates metabolic alkalosis.

Mnemonic for Acid-Base Disorders: "ROME"

• Respiratory disorders show opposite changes (as pH increases, PaCO₂ decreases, and vice versa).

• Metabolic disorders show equal changes (as pH and HCO₃ both increase or decrease).

Disorder Breakdown

• Respiratory Acidosis: pH < 7.35; causes include COPD and hypoventilation; management includes retaining CO₂ to improve pH.

• Respiratory Alkalosis: pH > 7.45; causes include hyperventilation; management involves addressing anxiety and breathing patterns.

• Metabolic Acidosis: pH < 7.35; includes conditions like DKA and renal failure; treatment involves correcting the underlying cause and bicarbonate replenishment.

• Metabolic Alkalosis: pH > 7.45; include causes like vomiting or diuretics; management focuses on replacing lost fluids and electrolytes.