Fluid and Electrolytes

Fluid and Electrolytes 150 150 Tony Guo

Fluid and Electrolytes


Normal physiology

  • Maintenance of homeostasis
  • Composition of fluids and electrolytes kept within narrow limits
  • Water content varies with age, gender, and fat content

Fluid Compartments 

  • Intracellular fluid (ICF)
    • Interstitial
    • Intravascular (plasma)
  • Extracellular fluid (ECF)
    • Transcellular
    • Lymph

Calculation of Fluid Gain or loss

  • One liter of water weighs 2.2 lbs. (1 kg) 
  • Body weight change is an excellent indicator of overall fluid volume loss or gain



  • Substances whose molecules dissociate into ions when placed in water
    • Cations: positively charged
    • Anions: negatively charged
  • Concentration of electrolytes is expressed in milliequivalents (mEq)/L
  • ICF
    • Prevalent cation is K+
    • Prevalent anion is PO43-
  • ECF
    • Prevalent cation is Na+
    • Prevalent anion is Cl-


Osmotic Movement of Fluids and effects on RBC

  • The osmolality of the fluid surrounding cells affects them
    • Isotonic
      • Normal distribution of water and solvent
    • Hypotonic
      • Large amount of water entering the cell
      • Causing the cell to swell
      • Eventually burst
    • Hypertonic
      • Large amount of water leaving the cell
      • Causing it to shrink
      • Eventually crenating

Mechanisms controlling fluid and electrolyte movement

  • To main homeostasis different processes are involved
    • Simple diffusion
      • movement of molecules from an area of high concentration to low concentration
    • Facilitated diffusion
      • Use of a protein carrier in the cell membrane that combine with molecules that are too large to pass easily through the cell membrane, and assists in moving the molecule across the membrane from an area of high to low concentration
    • Active transport.
      • Molecules move against the concentration gradient, but only in the presence of external energy. (sodium-potassium pump)
    • Osmosis
      • Movement of water across a semipermeable membrane from a region of low solute concentration to one of high solute concentration
  • Water is driven by two forces
    • Hydrostatic pressure
      • Blood pressure generated by heart contraction
    • Oncotic pressure
      • Osmotic pressure caused by plasma proteins


Fluid movement in capillaries

  • The plasma flows through the capillary but its amount and direction in/out is determined by 
    • Capillary hydrostatic pressure (out the capillaries)
    • Plasma oncotic pressure (into the capillaries)
    • Interstitial hydrostatic pressure (into the capillaries)
    • Interstitial oncotic pressure (out the capillaries)
  • Fluid shifts
    • Plasma-to-interstitial fluid shift results in edema
      • Elevation of venous hydrostatic pressure
      • Decrease in plasma oncotic pressure
      • Elevation of interstitial oncotic pressure
    • Interstitial fluid drawn into plasma decreases edema

Fluid spacing

  • Used to describe the distribution of body water
    • First spacing- Normal distribution
    • Second spacing- Abnormal (edema)
    • Third spacing- Fluid is trapped where it is difficult or impossible for it to move back into cells or blood vessels
  • Normal fluid balance


Fluids  1200 mL
Solid food L 1000 m
Water from oxidation  300 mL
Total  2500 mL
Insensible loss (skin and lungs)  900 mL
In feces  100 mL
Urine  1500 mL
Total  2500 mL


Extracellular fluid volume imbalances

  • ECF volume deficit (hypovolemia)
    • Abnormal loss of body fluids, inadequate fluid intake, or plasma to interstitial fluid shift
    • Clinical manifestations related to loss of vascular volume as well as CNS effects
    • Correct the underlying cause and replace water and electrolytes (Oral, Blood products, and IV Fluids)
  • Fluid volume excess (hypervolemia)
    • Excess intake of fluids, abnormal retention of fluids, or interstitial-to-plasma fluid shift
    • Clinical manifestations related to excess volume
    • Remove fluid without changing electrolyte composition or osmolality of ECF (diuretics, fluid restriction, sodium restriction)


Nursing Management

Nursing Diagnosis

  • Hypovolemia
    • Deficient fluid volume related to excess ECF losses or decreased fluid intake
    • Decreased cardiac output related to excess ECF losses or decreased fluid intake
    • Risk for impaired oral mucous membranes related to fluid volume deficit
    • Potential complication: Hypovolemic shock
  • Hypervolemia
    • Excess fluid volume related to increased water and/or sodium retention
    • Impaired gas exchange related to water retention leading to pulmonary edema
    • Risk for impaired skin integrity related to edema
    • Activity intolerance related to increased water retention, fatigue, and weakness
    • Disturbed body image related to altered body appearance secondary to edema
    • Potential complications: Pulmonary edema, ascites


Nursing implementation

  • Daily weights
    • Most accurate measure of volume status
  • Input & Output
    • Record to find out any information that will show fluid and electrolyte imbalance
  • Laboratory findings
    • Monitor laboratory results when available and calculate the serum osmolality
    • Patient with a fluid volume deficit often has increased BUN, sodium, and hematocrit levels with increased plasma and urine osmolality. 
    • Patient with fluid volume excess will have decreased BUN, sodium, and hematocrit levels with decreased plasma and urine osmolality
  • Cardiovascular care
    • Changes in BP, central venous pressure, pulse force, and jugular venous distention reflect ECF volume imbalances
    • Know what can happen when there is excess and deficit
      • In excess, 
  • The pulse is full, bounding, and not easily obliterated. 
  • Increased volume causes distended neck veins (jugular venous distention)
  • Increased central venous pressure and high BP
  • Auscultate heart sounds, being alert for the presence of an S3
  • Fluid volume deficit, 
  • Sympathetic nervous system compensation increases the heart rate and results in peripheral vasoconstriction in an effort to maintain BP within normal limits. 
  • Pulses may be weak and thready. 
  • Assess for orthostatic changes.
  • Respiratory care
    • Monitor pulse oximetry and auscultate lung sounds as needed
      • In excess
  • Pulmonary congestion and pulmonary edema, as increased hydrostatic pressure in the pulmonary vessels forces fluid into the alveoli. 
  • The patient will experience shortness of breath and moist crackles on auscultation
  • deficit will demonstrate 
  • An increased respiratory rate because of decreased tissue perfusion and resultant hypoxia. 
  • Administer oxygen as ordered.
  • Patient Safety
    • Deficit is at risk for falls because of orthostatic hypotension, muscle weakness, and changes in level of consciousness.
  • Skin care
    • Examine the skin for turgor and mobility



  • Plays a major role in
    • ECF volume and concentration
    • Generation and transmission of nerve impulses
    • Muscle contractility
    • Acid-base balance
  • Hypernatremia
    • Elevated serum sodium occurring with inadequate water intake, excess water loss or sodium gain
      • Causes hyperosmolality leading to cellular dehydration 
      • Manifestations
  • Thirst
  • Alterations in mental status, ranging from agitation, restlessness, confusion and lethargy to seizures and coma 
  • Symptoms of fluid volume deficit
  • Nursing diagnosis
    • Risk for electrolyte imbalance related to inadequate water intake, excess sodium intake and/or water loss injury related to altered sensorium and seizures
    • Risk for fluid volume deficit related to inadequate water intake and/or water loss
    • Risk for injury related to altered sensorium and seizures
    • Potential complication: Seizures and coma
  • Nursing implementation
    • Treat underlying cause
    • Primary water deficit—replace fluid orally or IV with isotonic or hypotonic fluids
    • Excess sodium—dilute with sodium-free IV fluids and promote excretion with diuretics
  • Hyponatremia
    • Results from loss of sodium-containing fluids and/or from water excess
      • Manifestations
        • Mild- headache, irritability, difficulty concentrating.  
        • More severe- confusion, vomiting, seizures, coma
    • Nursing diagnosis
      • Risk for electrolyte imbalance related to excess sodium loss and/or excess water intake or retention
      • Risk for injury related to altered sensorium and decreased level of consciousness
      • Risk for acute confusion related to electrolyte imbalance
      • Potential complication: Severe neurologic changes
    • Nursing implementation – Cause is water excess
      • Fluid restriction is needed
      • Loop diuretics
      • Severe symptoms (seizures)
        • Give small amount of IV hypertonic saline solution (3% NaCl)
      • Fluid replacement with sodium-containing solution
      • Increase oral intake
      • Withholding diuretics
      • Drugs that block vasopressin (ADH)


Sodium Imbalances: Causes and Manifestations
Hypernatremia (Na+ >145 mEq/L [mmol/L]) Hyponatremia (Na+ <135 mEq/L [mmol/L])
  • Diabetes insipidus
  • Primary hyperaldosteronism
  • Cushing syndrome
  • Uncontrolled diabetes mellitus
  • Heart failure
  • Primary hypoaldosteronism
  • Cirrhosis
Excessive Sodium Intake Excessive Sodium Loss
  • IV fluids: hypertonic NaCl, excessive isotonic NaCl, IV sodium bicarbonate
  • GI losses: diarrhea, vomiting, fistulas, NG suction
  • Hypertonic tube feedings without water supplements
  • Renal losses: diuretics, adrenal insufficiency, Na+ wasting renal disease
  • Near-drowning in salt water
  • Skin losses: burns, wound drainage
Inadequate Water Intake Inadequate Sodium Intake
  • Unconscious or cognitively impaired individuals
  • Fasting diets
Excessive Water Loss (Increased sodium concentration) Excessive Water Gain (Decrease sodium concentration)
  • Increased Insensible water loss (high fever, heatstroke, prolonged hyperventilation)
  • Excessive hypotonic IV fluids
  • Osmotic diuretic therapy
  • Primary polydipsia
  • Diarrhea


  • Manifestations
Hypernatremia with Decreased ECF Volume Hyponatremia with Decreased ECF Volume
  • Restlessness, agitation, lethargy, seizures, coma
  • Irritability, apprehension, confusion, dizziness, personality changes, tremors, seizures, coma
  • Intense thirst, dry swollen tongue, sticky mucous membranes
  • Dry mucous membranes
  • Postural hypotension, decrease CVP, weight loss, increased pulse
  • Postural hypotension, decrease CVP, decrease jugular venous filling, increase pulse, thready pulse
  • Weakness, muscle cramps
  • Cold and clammy skin
Hypernatremia with Normal or Increased ECF Volume Hyponatremia with Normal or Increased ECF Volume
  • Restlessness, agitation, twitching, seizures, coma
  • Headache, apathy, confusion, muscle spasms, seizures, coma
  • Intense thirst, flushed skin
  • Nausea, vomiting, diarrhea, abdominal cramps
  • Weight gain, peripheral and pulmonary edema, increased BP, increased CVP
  • Weight gain, increased BP, increased CVP



  • Major ICF cation necessary for
    • Transmission and conduction of nerve and muscle impulses 
    • Cellular growth
    • Maintenance of cardiac rhythms
    • Acid-base balance
  • Sources 
    • Fruits and vegetables (bananas and oranges)
    • Salt substitutes 
    • Potassium medications (PO, IV)
  • Regulated by kidneys
  • Hyperkalemia
    • High serum potassium caused by
      • Impaired renal excretion
      • Shift from ICF to ECF
      • Massive intake
    • Most common in renal failure
    • Manifestations
      • Cardiac dysrhythmias
      • Cramping leg pain
      • Weak or paralyzed skeletal muscles
      • Abdominal cramping or diarrhea
    • ECG effects of Hyperkalemia
  • Decreased R wave amplitude
  • Widened QRS
  • Wide, flat P wave
  • Depressed ST segment
  • Prolonged PR interval
  • Tall, peaked T wave


  • The most clinically significant manifestations of hyperkalemia are the disturbances in cardiac conduction. 
  • Cardiac depolarization is decreased, leading to flattening of the P wave and widening of the QRS complex. 
  • Repolarization occurs more rapidly, resulting in shortening of the QT interval and causing the T wave to be narrower and more peaked. 
  •  Ventricular fibrillation or cardiac standstill may occur.
  • Nursing diagnosis
    • Risk for electrolyte imbalance related to excessive retention or cellular release of potassium
    • Risk for activity intolerance related to muscle weakness
    • Risk for injury related to muscle weakness and seizures
    • Potential complication: dysrhythmias
  • Nursing implementation
    • Eliminate oral and parenteral K intake
    • Increase elimination of K (diuretics, dialysis, Kayexalate)
    • Force K from ECF to ICF by IV insulin and a -adrenergic agonist or sodium bicarbonate
    • Reverse membrane effects of elevated ECF potassium by administering calcium gluconate IV
  • Hypokalemia
    • Low serum potassium caused by
      • Increased loss of K+ via the kidneys or gastrointestinal tract
      • Increased shift of K+ from ECF to ICF
      • Dietary K+ deficiency (rare) 
    • Manifestations
      • Cardiac most serious
      • Skeletal muscle weakness (legs)
      • Weakness of respiratory muscles
      • Decreased GI motility
      • Hyperglycemia
    • ECG effects of Hypokalemia
  • Slightly peaked P wave
  • Shallow T wave
  • Slightly prolonged PR interval
  • Prominent U wave
  • ST depression


  • Nursing diagnosis
    • Risk for electrolyte imbalance related to excess potassium loss
    • Risk for activity intolerance related to muscle weakness
    • Risk for injury related to muscle weakness and hyporeflexia
    • Potential complication: dysrhythmias
  • Nursing implementation
    • KCl supplements orally or IV
    • Always dilute IV KCl 
    • NEVER give KCl via IV push or as a bolus
    • Should not exceed 10 mEq/hr. 
    • Use an infusion pump


Potassium Imbalances: Causes and Manifestations
Hyperkalemia (K+ >5.0 mEq/L [mmol/L]) Hypokalemia (K+ <3.5 mEq/L [mmol/L])
Excessive Potassium Intake Excessive Potassium Loss
  • Excessive or rapid parenteral administration
  • GI losses: diarrhea, vomiting, fistulas, NG suction, ileostomy drainage
  • Potassium-containing drugs (e.g., potassium penicillin)
  • Renal losses: diuretics, hyperaldosteronism, magnesium depletion
  • Potassium-containing salt substitute
  • Skin losses: diaphoresis
  • Dialysis
Shift of Potassium Out of Cells Shift of Potassium into Cells
  • Acidosis
  • Increased insulin release (e.g., IV dextrose load)
  • Tissue catabolism (e.g., fever, crush injury, sepsis, burns)
  • Insulin therapy (e.g., with diabetic ketoacidosis)
  • Intense exercise
  • Alkalosis
  • Tumor lysis syndrome
  • Increased Epinephrine (e.g., stress)
Failure to Eliminate Potassium Lack of Potassium Intake
  • Renal disease
  • Starvation
  • Adrenal insufficiency
  • Diet low in potassium
  • Medications: Angiotensin II receptor blockers, ACE inhibitors, heparin, potassium-sparing diuretics, NSAIDs
  • Failure to include potassium in parenteral fluids if NPO



  • Functions 
    • Formation of teeth and bone
    • Blood clotting
    • Transmission of nerve impulses
    • Myocardial contractions
    • Muscle contractions
  • Balance controlled by
    • Parathyroid hormone
    • Calcitonin
  • Hypercalcemia
    • High levels of serum calcium caused by
      • Hyperparathyroidism (two thirds of cases)
      • Malignancy 
    • Manifestations
      • Fatigue, lethargy, weakness, confusion
      • Hallucinations, seizures, coma
      • Cardiac dysrhythmias
      • Bone pain, fractures, nephrolithiasis
      • Polyuria, dehydration
    • Nursing diagnosis
      • Risk for electrolyte imbalance related to excessive bone destruction
      • Risk for activity intolerance related to generalized muscle weakness
      • Risk for injury related to neuromuscular and sensorium changes
      • Potential complication: dysrhythmias
    • Nursing implementation
      • Excretion of Ca with loop diuretic
      • Hydration with isotonic saline infusion
      • Low calcium diet
      • Mobilization
      • Bisphosphonates
      • IM or SC calcitonin
  • Hypocalcemia
    • Low serum Ca levels caused by
      • Decreased production of PTH
      • Multiple blood transfusions 
      • Alkalosis
      • Increased calcium loss
    • Manifestations
      • Positive Trousseau’s or Chvostek’s sign
      • Laryngeal stridor
      • Dysphagia
      • Tingling around the mouth or in the extremities 
      • Cardiac dysrhythmias
    • Nursing diagnosis
      • Risk for electrolyte imbalance related to decreased PTH level
      • Ineffective breathing pattern related to laryngospasm
      • Acute pain related to sustained muscle contractions
      • Risk for injury related to tetany and seizures
      • Potential complications: fracture, respiratory arrest

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