Chapter10feABG 2

Chapter 10: Fluid and Electrolytes

Introduction

• Importance in life and homeostasis (internal equilibrium).

• Nurse's role: Anticipate, identify, and respond to imbalances.

Fluid

• Approximately 60% of a typical adult's body weight is fluid (combination of water and electrolytes).

  • Varies with age, body fat, gender.

• Types of Fluid:

  • Intracellular fluid (ICF):

    • Comprises 2/3 of body fluid.

    • Predominantly found in skeletal muscle mass.

  • Extracellular fluid (ECF):

    • Divided into:

      • Intravascular fluid:

        • Contains plasma, erythrocytes, leukocytes, thrombocytes.

      • Interstitial fluid:

        • Surrounds the cells and includes lymph.

      • Transcellular fluid:

        • Includes cerebrospinal, pericardial, and synovial fluids.

Electrolytes

• Active chemicals that carry positive (cations) and negative (anions) electrical charges.

• Major Cations:

  • Sodium, potassium, calcium, magnesium, hydrogen ions.

• Major Anions:

  • Chloride, bicarbonate, phosphate, sulfate, negatively charged proteins.

• Electrolyte concentration differs in ICF and ECF compartments.

• Measured in millequivalents (mEq)/liter.

Regulation of Fluid

• Osmosis:

  • The diffusion of water due to fluid and solute concentration gradients.

  • Dependent on:

    • Hydrostatic pressure: Exerted on blood vessel walls.

    • Osmotic pressure: Exerted by proteins in plasma.

• Directional fluid movement is determined by differences in hydrostatic and osmotic pressures.

Key Processes:

• Osmosis: Water moves from areas of low solute concentration to high.

• Diffusion: Solutes move from areas of high concentration to low.

• Filtration: Movement based on hydrostatic pressure.

• Active Transport:

  • Example: Sodium-potassium pump maintaining higher extracellular sodium and intracellular potassium.

Gains and Losses of Fluid and Electrolytes

• Gains:

  • Healthy individuals gain fluid primarily through drinking and eating.

  • Daily intake and output (I&O) of water typically are equal.

• Losses:

  • Kidneys: Urine output of 1 mL/kg/hr.

  • Skin: Sensible loss (sweating) and insensible loss (fever, exercise, burns).

  • Lungs: Approximately 300 mL daily, increased with respiration.

  • Gastrointestinal (GI) tract: Significant losses from diarrhea and fistulas.

Homeostatic Mechanisms

• Maintain body fluid within normal limits involving:

  • Kidney

  • Heart and blood vessels

  • Lungs

  • Pituitary gland

  • Adrenal glands

  • Parathyroid glands

  • Baroreceptors

  • Renin–Angiotensin–Aldosterone System

  • Antidiuretic Hormone (ADH)

  • Osmoreceptors

  • Natriuretic Peptides

Gerontologic Considerations

• Clinical manifestations of imbalances may present subtly in older adults.

• Fluid deficits can lead to delirium.

• Common changes include:

  • Decreased cardiac reserve.

  • Reduced renal function.

  • Increased risk of dehydration due to age-related skin changes.

Fluid Volume Disturbances

• Fluid Volume Deficit (FVD): Hypovolemia.

• Fluid Volume Excess (FVE): Hypervolemia.

Fluid Volume Deficit (Hypovolemia)

• Can occur alone or alongside other imbalances.

  • Occurs when loss of extracellular fluid exceeds intake, affecting electrolytes proportionally.

• Dehydration: Loss of water alone, leading to increased serum sodium levels.

Causes of FVD

• Abnormal fluid losses:

  • Vomiting, diarrhea, sweating, GI suctioning.

• Decreased intake:

  • Nausea, lack of access to fluids.

• Third-space fluid shifts:

  • Burns, ascites.

• Other causes:

  • Diabetes insipidus, adrenal insufficiency, hemorrhage.

Clinical Manifestations, Assessment, and Diagnostic Findings of FVD

• Rapid development possible; severity based on degree of loss.

• Refer to Table 10-4 for clinical signs, symptoms, and lab findings.

Gerontologic Considerations for FVD

• Assess:

  • Cognition

  • Ambulation

  • Activities of Daily Living (ADLs)

  • Gag reflex

Medical Management of FVD

• Oral rehydration preferred; IV therapy for acute/severe losses.

• Types of solutions:

  • Isotonic, Hypotonic, Hypertonic, Colloid (Refer to Table 10-5).

Nursing Management of FVD

• Monitor I&O at least every 8 hours; daily weights.

• Closely monitor vital signs and assess skin/tongue turgor, mucosa, urine output, and mental status.

• Minimize fluid loss, administer oral and parenteral fluids.

Fluid Volume Excess (Hypervolemia)

• Defined as expansion of the extracellular fluid (ECF) due to abnormal water and sodium retention, typically simultaneously.

• Often results from increased total-body sodium content.

Causes of FVE

• Due to fluid overload or diminished homeostatic mechanisms.

  • Includes heart failure, kidney injury, cirrhosis, excessive table salt or sodium-containing fluids.

Clinical Manifestations, Assessment, and Diagnostic Findings of FVE

• Symptoms include edema, distended neck veins, crackles, and lab values related BUN and hematocrit (HCT).

• Refer to Table 10-4 for relevant findings.

Medical Management of FVE

• Pharmacologic: Use of diuretics, dialysis as required.

• Nutritional: Implement dietary sodium restrictions.

Nursing Management of FVE

• Monitor I&O and daily weights; assess lung sounds, edema, and other symptoms.

• Monitor medications (diuretics, parenteral fluids), promote fluid restriction adherence, and educate regarding sodium and fluid restrictions.

Electrolyte Imbalances

• Common imbalances include:

  • Sodium: Hyponatremia, hypernatremia.

  • Potassium: Hypokalemia, hyperkalemia.

  • Calcium: Hypocalcemia, hypercalcemia.

  • Magnesium: Hypomagnesemia, hypermagnesemia.

  • Phosphorus: Hypophosphatemia, hyperphosphatemia.

  • Chloride: Hypochloremia, hyperchloremia.

Hyponatremia

• Sodium serum levels below 135 mEq/L.

  • Acute: Fluid overload in surgical patients.

  • Chronic: Longer duration, less severe.

  • Exercise-associated: More frequent in small-stature females in extreme conditions with excess fluid intake during prolonged exercise.

Pathophysiology, Clinical Manifestations, Assessment of Hyponatremia

• Pathophysiology: Imbalance of water leading to losses via:

  • Vomiting, diarrhea, sweating, medications, adrenal insufficiency, SIADH.

Clinical manifestations:

• Poor skin turgor, dry mucosa, headache, decreased blood pressure, nausea, abdominal cramping, neurologic changes.

Management of Hyponatremia

• Treat the underlying cause.

• Sodium replacement and water restriction as necessary.

• Monitor I&O, daily weights, lab values, and CNS changes.

• Encourage dietary sodium intake and monitor for effects of medications (e.g., diuretics).