NUR-210 Fluid & Electrolyte Balance

FLUID & ELECTROLYTE BALANCE

• Prepared by Grace M. Gass, MSN, RN

OBJECTIVES

• Describe the volume disturbances:

  • Fluid Volume Deficit (FVD)

  • Fluid Volume Excess (FVE)

• Identify roles of sodium and potassium in homeostasis.

• List signs and symptoms of sodium and potassium imbalances.

• Discuss clinical assessments for fluid and electrolyte balance.

• Describe laboratory studies for monitoring these balances.

• Outline nursing actions for patients with fluid imbalances.

• Discuss administration of major electrolyte replacement agents.

DEFINITIONS

• Fluid: Water with dissolved/suspended substances.

• Electrolyte: Dissolvables in water producing ions that conduct electricity.

  • Cations:

    • Sodium (Na+)

    • Potassium (K+)

    • Magnesium (Mg2+)

    • Calcium (Ca2+)

  • Anions:

    • Chloride (Cl-)

    • Bicarbonate (HCO3-)

IMPORTANCE OF FLUID & ELECTROLYTES

• Cellular metabolism

• Nutrient transportation

• Digestive processes

• Waste excretion

• Temperature regulation

• Acid-base balance

• Muscle and neurological function

DISTRIBUTION OF BODY WATER

• Sex: Males have more body water.

• Age: Infants have a higher percentage, elderly have less.

• Body Composition: Obese individuals have less body water.

MAJOR FLUID COMPARTMENTS

• Intracellular Fluid (ICF): Fluid within cells.

• Extracellular Fluid (ECF):

  • Intravascular (plasma): Fluid in blood vessels.

  • Interstitial: Fluid surrounding cells.

  • Transcellular: Fluid within body cavities (e.g., pleura, peritoneum).

ELECTROLYTE CONTENT OF ICF & ECF

• ICF:

  • Potassium (K+)

  • Phosphate (PO4-)

• ECF (Intravascular):

  • Sodium (Na+)

  • Chloride (Cl-)

REVIEW: DIFFUSION

• Movement of solutes from higher to lower concentration.

• Passive process through semi-permeable membrane.

REVIEW: OSMOSIS

• Water transfer across semi-permeable membrane from low solute to high solute area.

FLUID BALANCE

• Healthy Adult Average Fluid Intake:

  • Intake:

    • Fluids: 1100-1400 mL

    • Foods: 800-1000 mL

    • Metabolism: 300 mL

    • Total: 2200-2700 mL

  • Output:

    • Urine: 1200-1500 mL

    • Gastrointestinal: 100-200 mL

    • Skin: 500-600 mL

    • Lungs: 400 mL

    • Total: 2200-2700 mL

REGULATING FLUID BALANCE

• Thirst-Control Mechanism:

  • Hypothalamus triggers thirst via osmoreceptors monitoring plasma osmolality.

  • Baroreceptors monitor plasma volume.

• Kidneys: Major regulators, respond to:

  • Antidiuretic hormone (ADH)

  • Renin-Angiotensin-Aldosterone System (RAAS)

REGULATING FLUID BALANCE: ADH

• Released by posterior pituitary when thirsty.

• Signals kidneys to reabsorb water back to bloodstream instead of excretion.

REGULATING FLUID BALANCE: RAAS

• Main Goal: Conserve fluid to increase blood pressure (BP).

  • Juxtaglomerular apparatus senses BP drop, secretes Renin.

  • Renin converts angiotensinogen to Angiotensin I.

  • ACE converts Angiotensin I to Angiotensin II:

    • Causes blood vessel constriction

    • Triggers aldosterone release to reabsorb sodium

    • Increased sodium attracts water via osmosis, increasing BP.

REGULATING FLUID BALANCE: Key Points

• ADH: Anti-urine, reabsorbs water.

• Aldosterone: Reabsorbs sodium.

ASSESSMENT

• Daily Weight: 1 kg = 1 liter, 2.2 lbs = 1 liter, measured at the same time on the same scale.

• Intake and Output (I&O): Document all intake and output in mL, including fluids, food, and IVs.

ASSESSMENT: LAB VALUES

• Blood Urea Nitrogen (BUN): 10-20 mg/dL

• Creatinine (Cr): 0.6-1.2 mg/dL

• Electrolytes:

  • Sodium (Na+): 135-145 mEq/L

  • Potassium (K+): 3.5-5.0 mEq/L

• Hematocrit (Hct): Male: 42%-52%, Female: 37%-47%

• Urine Specific Gravity: 1.005–1.030

FLUID IMBALANCES

• Fluid Volume Deficit (FVD): Dehydration, hypovolemia.

• Fluid Volume Excess (FVE): Hypervolemia.

FLUID VOLUME DEFICIT: RISK FACTORS

• Age: infants and elderly at risk.

• Increased fluid loss: vomiting, diarrhea, fever, diaphoresis, increased respiratory rate.

• Decreased intake: nausea, anorexia, confusion.

FLUID VOLUME DEFICIT: SIGNS & SYMPTOMS

• Thirst

• Vital Signs: Tachycardia, weak/thready pulse, postural hypotension.

• Urine Characteristics: Dark yellow urine, oliguria (< 400mL/day).

• Physical Signs: Poor skin turgor, dry skin and mucus membranes.

FLUID VOLUME EXCESS: RISK FACTORS

• Abnormal fluid retention from renal failure, heart failure, or excess IV fluid.

FLUID VOLUME EXCESS: SIGNS & SYMPTOMS

• Sudden weight gain.

• Jugular vein distension (JVD).

• Bounding pulses.

• Peripheral or pulmonary edema (crackles).

HYDROSTATIC & ONCOTIC PRESSURE

• Hydrostatic Pressure: Pressure of fluids.

• Oncotic Pressure: Pressure of proteins (attracts water).

CAUSES OF EDEMA & THIRD SPACING

• Edema: Fluid collects in interstitial space due to:

  • Increased hydrostatic pressure (hypertension, fluid overload).

  • Decreased oncotic pressure (lack of proteins).

PITTING EDEMA CLASSIFICATION

• 1+ Pitting Edema: Slight indentation (2mm).

• 2+ Pitting Edema: Deeper pit (4mm), lasts longer than 1+.

• 3+ Pitting Edema: Deep pit (6mm), remains seconds after pressing.

• 4+ Pitting Edema: Deep pit (8mm), lasts minutes.

• Brawny Edema: No pitting, firm/hard tissue, shiny skin.

ELECTROLYTE IMBALANCES

• Potassium Imbalances:

  • Hyperkalemia

  • Hypokalemia

• Sodium Imbalances:

  • Hypernatremia

  • Hyponatremia

POTASSIUM (K+)

• Major intracellular cation; Reference range: 3.5 - 5 mEq/L.

• Functions: Nerve impulse transmission, fluid balance, acid/base balance.

HYPERKALEMIA (K+ EXCESS) (>5 MEQ)

• Causes: Excess intake, decreased loss (renal failure), acidosis, tissue damage.

• Signs & Symptoms: Irregular pulse, muscle weakness, gastrointestinal disturbances.

• Nursing Considerations: Monitor levels, manage using diuretics or insulin.

HYPOKALEMIA (K+ DEFICIT) (<3.5 MEQ)

• Causes: Increased loss (GI), decreased intake, shift into cells.

• Signs & Symptoms: Weak pulse, muscle weakness, constipation.

• Nursing Considerations: Increase dietary K+, monitor levels, carefully execute IV K+ therapy.

SODIUM (Na+)

• Major extracellular cation; Reference range: 135-145 mmol/L.

• Functions: Regulate fluid balance, blood pressure, muscle/nerve function.

HYPERNATREMIA (Na+ EXCESS) (>145 MEQ)

• Causes: Dehydration, excessive Na+ intake.

• Signs & Symptoms: Confusion, restlessness, thirst; severe cases can lead to seizures.

• Management: Gradually lower sodium levels, provide hydration.

HYPONATREMIA (Na+ DEFICIT) (<135 MEQ)

• Causes: Excessive water intake, loss of Na+ fluid.

• Signs & Symptoms: Irritability, headache, muscle spasms.

• Management: Monitor levels, fluid restriction if necessary.

ELECTROLYTE IMBALANCES SUMMARY

• Potassium (K+ Range): 3.5-5 mEq/L

  • Hyperkalemia: High potassium

  • Hypokalemia: Low potassium

  • Key concern: CARDIAC DYSRHYTHMIAS

  • NEVER IV PUSH OR RAPID BOLUS K+!!

• Sodium (Na+ Range): 135-145 mEq/L

  • Hypernatremia: High sodium

  • Hyponatremia: Low sodium

  • Key concern: SEIZURES

  • Sodium imbalances to be corrected SLOWLY.