Fluid and Electrolytes Notes

Composition of Body Fluids

• The two largest constituents of the body are water and electrolytes.
• Infants and the elderly are more easily affected by changes in fluid balance.

Water

• Functions:
  • Transport
  • Heat regulation
  • Hydrogen balance
  • Digestion
• Amount varies with age, sex, and health.

Sources of Water and Avenues of Loss

• Intake:
  • Oral: 1500 mL
  • Food: 800 mL
  • Metabolism: 200 mL
  • Total: 2500 mL
• Output:
  • Urine: 1500 mL
  • Perspiration: 400 mL
  • Feces: 200 mL
  • Expired air: 400 mL
  • Total: 2500 mL

Electrolytes

• Diet is a major source.
• Functions:
  • Sodium: Water regulation and balance
  • Potassium: Heart rhythm, nerve impulse transmission, muscle contraction
  • Calcium: Muscle activity, blood coagulation
  • Magnesium: Nerve impulse transmission, muscle contraction, blood coagulation
  • Chloride: Helps maintain acid-base balance
  • Phosphate: ATP production

Major Electrolytes: Normal Range

• Electrolyte Normal Range
  • Sodium: 135-145 mEq/L
  • Potassium: 3.5-5 mEq/L
  • Calcium: 9-10.5 mg/dL
  • Magnesium: 1.5-2.5 mg/dL
  • Phosphate: 2-4.5 mg/dL
  • Chloride: 98-106 mEq/L

Non-Electrolytes

• Amino acids (proteins), glucose, and fatty acids.
• Remain bound together when dissolved in body fluid.

Blood

• Normal circulating blood volume is 4 to 6 L.
• Composed of:
  • Erythrocytes (red cells)
  • Leukocytes (white cells)
  • Platelets (thrombocytes)
  • Carried in plasma
• Plasma proteins and colloids contribute to plasma osmotic pressure, which keeps fluid in the vascular compartment.

Body Fluids

• Intracellular (within the cell)
  • About 2/3 of total body water
  • Most cell walls are permeable to water
• Extracellular (outside the cell)
  • Intravascular
  • Interstitial
  • Transcellular

Extracellular Fluid

• About 1/3 of the total body water
• Transports nutrients, oxygen, and waste products to and from cells
• Regulated by renal, metabolic, and neurologic factors
• High in sodium content

Intravascular Fluid

• The fluid within the blood vessels
• Consists of plasma and fluid within the blood cells
• Contains large amounts of protein and electrolytes, which help maintain intravascular volume

Transcellular Fluids

• Aqueous humor (in the eyes)
• Saliva
• Cerebrospinal fluid
• Pleural, peritoneal, synovial, and pericardial fluids
• Gastrointestinal secretions
• Fluid in the urinary tract
• Lymphatic system fluids

Movement of Fluid & Electrolyte

• Water out = water in
  • Hypothalamus: Thirst mechanism
  • Kidneys: Main organ for fluid excretion
    • ADH
    • Aldosterone
    • ANP

Fluid & Electrolyte Imbalance

• Impacted by:
  • Kidney function
  • Illness
  • Circulatory conditions

Deficient Fluid Volume

• Patients unable to take in enough fluid.
• Patients who lose excessive amounts of fluid.
• At risk: Result is dehydration.

Dehydration

• When too little water in the plasma, water is drawn out of the cells by osmosis to equalize concentration, and the cells shrivel.
• Treated by fluid administration, either orally or intravenously.
• Testing for tissue turgor
• Signs/symptoms

Fluid Volume Excess

• Healthy people do not ordinarily drink too much water.
• At risk:
  • Receive intravenous fluid too quickly.
  • Given tap-water enemas.
  • Drink more fluids than they can eliminate.
  • Overproduction of ADH or aldosterone.
• Result is hypervolemia.

Signs of Overhydration

• Weight gain
• Crackles in the lungs (wet lungs)
• Slow bounding pulse
• Elevated blood pressure
• Possibly edema
• Example of pitting edema

Assessment of Fluid/Electrolyte Status

• VS
• Physical assessment
• Urine
• Electrolytes

NURSING PROCESS- Diagnosis

• Fluid volume excess
• Fluid volume deficit

Interventions

• Assess I&O
• Daily weight
• Limit fluid intake
• Administer diuretics as ordered
• Administer IV fluids as ordered
• Encourage fluid intake
• Monitor electrolyte values