fluids

Fluid and Electrolytes

Course Information

• Instructor: Maegen Mackenzie, MSN, RN

• Institution: Austin Community College

Preparation for Lecture

• Read Lewis et al. (12th ed.) – Chapter 17, pages 302 - 320 (skip Acid-Base Imbalances) and pages 324 - 328 (up to Central Venous Access)

• Watch the Fluid Balance pre-recorded lecture

• Determine the best learning strategy for recalling electrolyte lab values throughout the semester.

Lecture Objectives

1. Understand fluid status and disruptions in fluid balance.

2. Identify and differentiate fluid replacement therapies.

3. Describe common electrolyte imbalances, including:

   • Signs and symptoms

   • Lab values

   • Treatment and interventions

Normal Fluid Balance

Physiology

• Maintenance of homeostasis is crucial for a stable internal environment.

• Body fluids and electrolytes are in constant motion.

• The composition of fluids and electrolytes is kept within narrow limits to maintain balance and homeostasis.

• Adaptive responses to various disease processes can affect fluid and electrolyte balance.

• Importance for nurses to monitor for changes in fluid status.

Water Content Variability

• Water content varies with:

  • Age

  • Gender

  • Fat content

Fluid Compartments

• Intracellular Fluid (ICF):

  • Fluids inside cells; approximately 2/3 of body water.

  • Predominant Electrolytes:

    • Potassium (K+) cation

    • Phosphate (PO4^3−) anion

• Extracellular Fluid (ECF):

  • Fluids outside of cells; includes:

    • Interstitial Fluid

    • Intravascular Fluid (plasma)

  • Predominant Electrolytes:

    • Sodium (Na+) cation

    • Chloride (Cl-) anion

• Fluid Volume Distribution:

  • Plasma: 3 L

  • Interstitial Fluid (IF): 10 L

  • Intracellular Fluid (ICF): 28 L

Osmolality Imbalances

• Hypo-osmolality:

  • Value < 275 mOsm/kg indicates water excess or insufficient solute, causing cell swelling.

• Hyperosmolality:

  • Value > 295 mOsm/kg indicates concentration of solute is too great or water content is too little, leading to dehydration and cell shrinkage.

Osmotic Movement of Fluids

• Hypotonic (Hypo-osmolar):

  • Solutes less concentrated, causing cell swelling as water moves from ECF to ICF.

• Isotonic:

  • Fluids have the same osmolality; no fluid movement occurs.

• Hypertonic (Hyperosmolar):

  • Solutes more concentrated, causing cell shrinkage as water moves from ICF to ECF.

Osmolality Effects on Cells (RBCs)

• Hypotonic Solution:

  • Results in cellular swelling.

• Isotonic Solution:

  • Results in no changes to cell size.

• Hypertonic Solution:

  • Results in cellular shrinking.

Capillary Fluid Movement

• Interstitial Edema:

  • Fluid drawn into interstitial space leads to edema due to:

  • Fluid overload related to heart failure

  • Low plasma protein (albumin) levels

  • Damage to capillary walls from trauma, burns, or inflammation

• Interstitial Dehydration:

  • Interstitial fluid drawn into plasma reduces edema, influenced by medications (colloids, dextran, mannitol) and hypertonic IV solutions.

Practice Question

• An older adult patient with a serum protein level of 5.2 g/dL may present with:

  • Clinical manifestations such as pallor, edema, confusion, or restlessness.

Body Fluid Balance

Normal Fluid Volume Balance

• Fluid Volume Spacing

• Fluid Volume Imbalances:

  • Hypervolemia: Excess fluid volume.

  • Hypovolemia: Deficit in fluid volume .

Normal Fluid Volume Balance (Table)

Calculation of Fluid Gain or Loss

• Intake and output as well as daily weight.

Practice Question

• Fluid Loss Conversion:

  • 1 kg = 1 liter of water.

  • 2.2 kg = 1 liter.

  • 2.2 liters = 1 kg.

  • 1 lb = 2.2 liters.

Fluid Volume Spacing

• Fluid Spacing:

  • Describes distribution of body water between ICF and ECF compartments.

Fluid Spacing Types

1. First Spacing: Normal state of fluid in the body.

2. Second Spacing: Increased fluids in interstitial spaces, such as pedal edema.

3. Third Spacing: Abnormal fluid accumulation in areas where it cannot move back into cells or blood vessels, such as in ascites, burns, or trauma.

Fluid Volume Imbalances

Hypervolemia

• Causes:

  • Excess intake or abnormal retention of fluids due to:

  • Heart failure

  • Renal failure

  • SIADH

  • Cushing's syndrome

  • Long-term corticosteroid usage

  • Excessive isotonic or hypotonic IVFs

• Clinical Manifestations:

  • Headache, confusion, fatigue, peripheral edema, jugular venous distention (JVD), S3 heart sound, bounding pulses, hypertension (HTN), dyspnea, crackles, pulmonary edema, weight gain, seizures, and coma.

• Interprofessional Care:

  • Remove fluid without altering electrolyte composition or osmolality of ECF, potentially requiring diuretics and fluid restriction.

Hypovolemia

• Causes:

  • Insensible water loss or perspiration (high fever, heatstroke), Diabetes or Diabetic Ketoacidosis, hemorrhage, GI loss, nutritional deficit, inadequate fluid intake, and third-spacing shifts (burns, ascites).

• Clinical Manifestations:

  • Symptoms include restlessness, drowsiness, confusion, thirst, dry mucous membranes, decreased skin turgor, hypotension, tachycardia, increased respiratory rate, decreased urine output, concentrated urine, weight loss, seizures, and coma.

• Interprofessional Care:

  • Address underlying causes and replace water and electrolytes orally or through blood products and balanced IV solutions (Isotonic 0.9% sodium chloride, Lactated Ringer’s).

Practice Question

• Postoperative Assessment:

  • For early identification of fluid volume alterations, the nurse should monitor intake and output, skin turgor, lung sounds, respiratory rate, and level of consciousness.

Nursing Management of Fluid Volume Imbalances

• Daily Weights and I & O:

  • The most accurate measure of fluid volume status.

  • Intake: All oral, IV, enteral, and retained irrigation.

  • Output: Urine, wound/tube drainage, vomitus, diarrhea, and perspiration.

Laboratory Findings

• Monitor for accompanying electrolyte imbalances.

Cardiovascular Care

• Vital sign check: Blood pressure, heart rate, pulses, and JVD reflect fluid volume status.

Respiratory Care

• Hypervolemia: Risk of pulmonary edema and congestion.

• Hypovolemia: Risk of inadequate tissue oxygenation.

Neurovascular Care

• Regular monitoring of neuro status; implement safety precautions.

Integumentary Care

• Check for hypervolemia-related edema or hypovolemia-related poor skin turgor

Physiologic Regulation of Water Balance

Systems Involved

• Hypothalamic-Pituitary:

• Renal:

• Adrenal-Cortical:

• Cardiac:

• Gastrointestinal:

• Integumentary:

Regulation of Fluid Balance

Hypothalamic-Pituitary Regulation

• Osmoreceptors in the hypothalamus sense fluid deficit or excess.

• A deficit stimulates thirst and anti-diuretic hormone (ADH) release.

• Decreased plasma osmolality suppresses ADH release.

• Reminder: Thirst is the primary defense against dehydration.

Adrenal-Cortical Regulation

• Hormones like glucocorticoids (e.g., cortisol) and mineralocorticoids (e.g., aldosterone) regulate water and electrolyte levels.

Cardiac Regulation

• Natriuretic peptides (ANP and BNP): Produced by cardiomyocytes in response to increased atrial pressure. These hormones decrease blood volume and pressure by suppressing aldosterone, renin, and ADH secretion.

Gastrointestinal/Nutrition Regulation

• Oral intake is primarily responsible for body water volume.

• Adequate nutrition maintains fluid balance; low albumin can result in edema.

Integumentary Regulation

• Provides a waterproof barrier; regulates body temperature and elimination of waste.

• Imbalances:

  • Insensible water loss due to burns or heat conditions can lead to hypovolemic shock and various electrolyte imbalances.

Treatment of Fluid and Electrolyte Imbalances

Oral Fluid and Electrolyte Replacement

• Used for mild deficits, can include water, glucose, potassium, and sodium.

• Recommended hydration solutions for children: Pedialyte (mixed fruit).

Intravenous (IV) Fluid and Electrolyte Replacement

• Necessary for severe imbalances or when oral intake is inadequate.

• Fluids categorized by tonicity: hypertonic, isotonic, hypotonic.

IV Fluid Types

• Hypotonic IV Fluids:

  • More water than electrolytes, diluting ECF and causing water movement to ICF (e.g., 0.45% saline).

  • Important in treating hypernatremia but can risk cerebral edema.

• Isotonic IV Fluids:

  • Similar concentrations of water and electrolytes; maintains fluid balance (e.g., D5W, 0.9% saline).

  • Risks of fluid overload or electrolyte imbalances.

• Hypertonic IV Fluids:

  • Increases osmolality of ECF (e.g., D5 0.45% NS); requires frequent monitoring and is used to decrease brain swelling in trauma patients.

Electrolytes Overview

• Key Electrolytes:

  • Sodium (Na+), Potassium (K+), Calcium (Ca^2+), Phosphate (PO4^3−), Magnesium (Mg^2+).

Importance of Electrolytes

• Electrolytes dissociate into ions in water, affecting multiple bodily functions including:

  • Regulation of water balance

  • Maintenance of acid-base balance

  • Metabolic enzyme reactions

  • Neuromuscular activity and heart function.

Electrolyte Lab Values

• Potassium (K+): 3.5 - 5.0 mEq/L

• Sodium (Na+): 136 - 145 mEq/L

• Magnesium (Mg2+): 1.3 - 2.1 mEq/L

• Phosphate (PO43-): 3.0 - 4.5 mg/dL

• Calcium (Ca2+): 9.0 - 10.5 mg/dL

Sodium (Na+)

• Normal Range: 136-145 mEq/L.

• Key roles include balancing extracellular fluid (ECF) concentrations, maintaining ECF volume and concentration, generating nerve impulses, and regulating acid-base balance.

Sodium Effects on Fluid Osmolality and Cells

• Hypotonic: Na+ < 135, leading to cell swelling.

• Isotonic: Na+ 135-145, no cell change.

• Hypertonic: Na+ >145, causing cell shrinkage.

Hypernatremia (Na+ > 145 mEq/L)

• Causes:

  • Inadequate water intake, excess water loss, sodium gain.

  • Risk of hyperosmolality and subsequent cellular dehydration.

Clinical Manifestations:

• Thirst, poor skin turgor, neurological changes (confusion, agitation to lethargy, seizures).

Management:

1. Treat underlying cause.

2. Replace fluids orally or IV with isotonic/hypotonic solutions.

3. Dilute with sodium-free IV fluids and promote sodium excretion with diuretics.

Hyponatremia (Na+ < 136 mEq/L)

• Causes: Loss of sodium fluids (vomiting/diarrhea) or water excess.

• Clinical Manifestations: Primarily neurological, can lead to headaches, irritability, confusion, seizures, and coma.

Management:

1. If caused by water excess, restrict fluids and administer diuretics.

2. Severe symptoms may require hypertonic saline (3% NaCl).

3. If caused by fluid loss, replace with isotonic sodium-containing solutions.

Potassium (K+)

• Normal Range: 3.5 - 5.0 mEq/L.

• Primary intracellular electrolyte key for nerve and muscle function, cardiac rhythms, and acid-base balance.

Hyperkalemia (K+ > 5.0 mEq/L)

• Causes: Impaired renal excretion (most common), dietary excess, shifts from ICF to ECF.

• Clinical Manifestations: Cardiac dysrhythmias, muscle cramping, weakness, abdominal symptoms.

Management:

1. Monitor cardiac status.

2. Eliminate K+ intake.

3. Increase elimination via diuretics, dialysis, or medications like Kayexalate.

Hypokalemia (K+ < 3.5 mEq/L)

• Causes: Increased loss of K+ through kidneys or GI tract, dietary deficiency.

• Clinical Manifestations: Cardiac dysrhythmias, muscle weakness, respiratory muscle weakness, decreased GI motility.

Management:

1. Monitor cardiac function.

2. Increase dietary K+ or oral supplements.

3. Severe cases require IV replacement of potassium.

Calcium (Ca2+)

• Normal Range: 9.0 - 10.5 mg/dL.

• Most abundant cation in the body; regulates muscle contractions, blood clotting, and is stored predominantly in bones.

Hypercalcemia (Ca2+ > 10.5 mg/dL)

• Causes: Hyperparathyroidism, malignancies, immobilization, increased intake.

• Clinical Manifestations: Sedative effects (lethargy, confusion), cardiac dysrhythmias, muscle pain.

Management:

1. Restrict dietary calcium.

2. Increase hydration and promote urinary excretion.

3. May require bisphosphonates or dialysis in severe cases.

Hypocalcemia (Ca2+ < 9.0 mg/dL)

• Causes: Decreased PTH production, blood transfusions, increased losses.

• Clinical Manifestations: Muscle excitability, cramping, Chvostek’s and Trousseau’s signs.

Management:

1. Replace calcium and vitamin D.

2. Administer oral or IV calcium gluconate.

Phosphate (PO43−)

• Normal Range: 3.0 - 4.5 mg/dL.

• Major electrolyte in ICF, controlled by parathyroid hormone and has a reciprocal relationship with calcium.

Hyperphosphatemia (PO43− > 4.5 mg/dL)

• Causes: Renal dysfunction, excessive intake, hypoparathyroidism.

• Clinical Manifestations: Similar to hypocalcemia, muscle excitability.

Management:

1. Address renal function and underlying causes.

2. Restrict dietary phosphorus.

3. May require phosphate binders or dialysis.

Hypophosphatemia (PO43− < 3.0 mg/dL)

• Causes: Malnourishment, chronic diarrhea, phosphate-binding antacids.

• Clinical Manifestations: Muscle weakness, severe cases can lead to respiratory or heart failure.

Management:

1. Promote foods high in phosphorus.

2. Administer oral or IV phosphate replacements.

Magnesium (Mg2+)

• Normal Range: 1.3 - 2.1 mEq/L.

• Important for muscle and nerve function, carbohydrate metabolism, and DNA synthesis.

Hypermagnesemia (Mg2+ > 2.1 mEq/L)

• Causes: Renal insufficiency, excessive intake.

• Clinical Manifestations: Low BP, muscle paralysis, lethargy.

Management:

1. Limit magnesium intake.

2. Promote excretion via IV fluids.

3. Severe cases may need IV calcium administration.

Hypomagnesemia (Mg2+ < 1.3 mEq/L)

• Causes: Prolonged fasting, alcoholism, GI loss.

• Clinical Manifestations: Resembles hypocalcemia; increased muscle excitability, seizures.

Management:

1. Check medications.

2. Increase dietary intake and oral supplements.

3. Severe cases require IV replacement.

Practice Questions

• Various clinical scenarios involving fluid and electrolyte management, assessment, and nursing interventions.

Study Recommendations

• Review PowerPoint lecture presentation and complete the Learning Guide utilizing information from lecture and textbook.

• Utilize the Learning Guide and Case Studies as a study guide.

• Make flashcards and/or concept maps.

• Create and participate in a study group.