Fluids and Electrolytes

• Fluid pressure inside and outside capillary

  • Outside capillary: Hydrostatic pressure 40 mmhg to the tissue
  • Inside capillary: 25 for oncotic pressure and 10 mmhg for hydrostatic pressure
• Regulation factors of water

  • Hypothalamus
  • Pituitary
  • Gastrointestinal
  • Genitourinary
• Gastrointestinal


  Gives source of water for the body, diarrhea and vomiting can led to increased water loss
• Genitourinary


  Output through urine and provides the largest output
• Insensible water loss


  900 MLs per day due to sweating, breathing, perspiration, and metabolic processes
• Hypothalamus and pituitary role in water regulation

  Hypothalamic osmoreceptors detect low osmolarity, triggering thirst, releasing ADH which increases water reabsorption
• RAAS

  Angiotensin 2 activates aldosterone which increases kidney reabsorption of water and sodium
• Age related changes for fluid regulation

  • Reduced renal function, excessive sweating, reduced thirst, reduced temp regulation
• Total intake and output fluid values

  • Intake: liquid 1000ml, food 800ml, oxidation of food 200ml with a total between 2000-2500 ml
  • Output: Lungs 400ml, Skin 300ml, urine 1000, feces 100ml with a total of 2500ml
• First spacing


  Normal ICF and ECF
• Second spacing

  Edema in the tissue resulting from too much IF
• Third spacing

  Accumulates in abnormal body cavities like the abdominal cavity, pleural effusion, Blisters which cannot move back into plasma
• Causes of hypovolemia (low fluid level)

  • vomiting diarrhea
  • suctioning fluid
  • wound drainage
  • kidney disease
  • diuretic overuse
• Manifestations of hypovolemia

  • low weight
  • low BP
  • weak pulse
  • High HR
  • long cap refill
  • dizziness
  • Low blood flow to the kidney
  • dry mucosa
  • constipation
  • low tissue turgor
  • no tears or sweat
• Causes of hypervolemia

  • Iv fluid overload
  • anything that increases aldosterone or kidneys to fail like corticosteroids
• Manifestations of hypervolemia


  • High weight
  • bounding pulses
  • High BP
  • High hydrostatic pressure
  • edema
  • pink sputum from pulmonary edema
• Isotonic IV fluid

  Expands only the extracellular fluid, used frequently
• Hypotonic IV fluid


  Provides more water than electrolytes, diluting the extracellular fluid moving water into the cells
• Hypertonic IV fluid


  Raises osmolarity in the ECF, drawing fluid outside of the cells. Used only in special circumstances with monitoring
• Crystalloids

  Supply water and electrolytes to the body, maintaining osmotic gradients between intra/extravascular spaces. They do not contain proteins and only contain naturally found fluids. Best for treating dehydration and expanding plasma volume. Compensates for fluid loss, replaces fluids, manages specific disturbances, promotes urinary flow.
• Normal saline (0.9%)


  Isotonic and used to expand ECF volume, providing immediate response and does not change ICF volume.
• ½ Normal saline (0.45%)


  Hypotonic containing water sodium and chlorine. Promotes movement from ecf to ICF and can lead to cellular swelling
• 3% Saline


  Hypertonic and used with extreme caution with slow administration. Can cause dangerous intravascular overload.
• 5% Dextrose


  Isotonic and provides 170 kcal/L. Free water becomes hypotonic, moving water into ICF.
• 10% Dextrose


  Hypertonic provides 340 kcal/L reaching the upper limit of dextrose concentration than can be absorbed.
• 5% Dextrose in 0.45% Saline


  Hypertonic In the bag by hypotonic in the body while providing calories.
• Lactic ringer


  Isotonic solution, similar to plasma. Contains K, Ca, Po, and lactate. Expands ECF and common replacement fluid.
• Colloid solutions


  Plasma expanders that increase colloidal osmotic pressure, moving fluid from interstitial to plasma compartment. Used to treat when protein level in blood falls, fluid shifts out of blood vessels and into tissues.
• Colloid solutions composition

  25% albumin and 5% albumin
• Hyponatremia


  Low osmolarity causes fluid to shift from the plasma where water concentration is high into the cells where it is low.
• Manifestations of Hyponatremia

  • Malaise
  • Anorexia
  • Headaches
  • Confusion
  • Brain swelling
• Causes of Hyponatremia

  • Drugs that cause too much ADH to be secreted
  • Gaining too much water
  • Excessive iv fluids with sodium
• Hypernatremia


  High NA in the plasma pulls fluids out if the ICF, shrinking cells and killing them.
• Manifestations of Hypernatremia

  • Intense thirst
  • CNS dysfunction
  • Lethargy
  • Seizures
  • Coma
  • Hypernatremia leading to death
• Causes of Hypernatremia

  • Gaining more salt than water due to hypertonic IV fluids
  • Drinking sea water
  • Losing more salt from diseases like diabetes that causes lack of ADH
• Hypernatremia treatments

  • With water loss, treat the cause and replace with isotonic fluid
  • With excess sodium, treat the underlying cause and replace it with salt free IV LIKE d5W and use diuretics
• Potassium


  The most abundant electrolyte in the cells with a percentage of 95% intercellular.
• Roles of potassium in the body

  • Muscle contraction
  • Nerve transmission
  • Heart regulation
  • Acid-base balance
• Sources of potassium


  • Fruit juice
  • Fish
  • Vegetables
  • Meats
  • Dairy
• Hypokalemia


  Deficiency of potassium below 3.5mmol