Fluid and electrolytes

• Homeostasis


  Managing fluid, electrolyte, and acid-base imbalances
• Components of body fluid composition


  • Water
  • Electrolytes
• Water


  • Transport nutrients
  • Medium for metabolic reactions
  • Regulation of body temperature
• Electrolytes


  • Neuromuscular activity (powerhouse)
  • Acid-base balance
  • Enzyme reactions
  • Water balance regulation
• Intracellular fluid


  Fluid found inside the cells, essential for normal cell function, predominantly contains potassium, magnesium, phosphate, glucose, oxygen
• Extracellular fluid

  Refers to any fluid outside cells: interstitial fluid, intravascular fluid, transcellular fluid, predominantly contains sodium, chloride, bicarbonate
• Total body weight consists of 60% fluid
• Infants and children are most susceptible to dehydration
• Forcing fluids


  3,000 L
• Normal range for fluid intake

  1800-2400 mL, higher than output
• Examples of insensible losses


  • Skin
  • Lungs
• Normal ratio for weight with input & output

  Up to 2 lbs/week OR 1lb a day
• Normal range for urine output

  30-50 mL (cc)/hour
• Specific gravity of urine


  Aids in evaluating hydration status, normal range 1.010-1.030
• Sodium movement


  With water
• Fluid balance concerns for elderly

  • Decreased percentage of fluid (lose subcutaneous tissue & fat)
  • Hormone regulators respond more slowly (delayed/decreased reaction)
  • Increased loss of moisture through skin (increased heat stroke risk)
  • Decreased thirst mechanism
• Input and output


  Around the same with intake being slightly higher
• Osmosis


  Movement of water to dilute concentrated area
• Diffusion


  Movement of molecules form an area of higher concentration to an area of lower concentration, simple or facilitated (carrier-mediated)
• Facilitated diffusion


  Requires carrier and energy
• Filtration


  Separation of solids from fluids (liquids or gasses), trying to balance hydrostatic and colloid osmotic pressure
• Mechanism of filtration


  Push and pull of capillary beds and glomerus (kidneys)
• Active transport


  Requires energy, example is sodium-potassium pump fueled by ATP
• Where filtration is used in the body


  • Intravascular and interstitial spaces
• Capillary bed


  Meeting place for veins and arteries
• Capillary bed pressure


  Arterial Capillary Bed: Hydrostatic Pressure (Greater), Venous Capillary Bed: Osmotic Pressure (Vacuum)
• Nitrogen


  Also called albumin, increased in interstitial pressure
• IV solutions


  • Isotonic: 0.9% Sodium Chloride (Normal Saline/ NS), Lactated Ringer's Solution, Plasma-Lyte 148, 5% Dextrose in Water (D5W)
  • Hypotonic: 0.45% Sodium Chloride (½ NS), 0.225% Sodium Chloride (¼ NS)
  • Hypertonic: D5 NS, D5 in Lactated Ringer's Solution, 10% Dextrose in Water (D10W), 3% Sodium Chloride, 5% Sodium Chloride, Parenteral Nutrition Solutions
• You can put 2 hypertonic solutions together
• Cells and movement of water


  Isotonic: Nor lose or gain water (retain normal shape), Hypotonic: Absorb water and could burst (Hemolysis), Hypertonic: Loss water and shrink/shrivel and die (Cremation)
• Hypotonic solution can cause hyponatremia due to increased size in cells creating decreased fluid
• When isotonic solutions are used


  Hypovolemia & gunshot wounds
• Administering ½ NS IV solution

  The fluid would move from the vascular volume to the cells
• Ways the body regulates fluid


  • Thirst
  • Kidneys
  • Renin-Angiotensin-Aldosterone System
  • Antidiuretic Hormone
  • Atrial Natriuretic Peptide
• Thirst


  Negative feedback loop, primary regulator of water intake, e.g. sweating from working outside
• Kidneys


  Regulate volume, osmolarity of body fluids, unless excess sweating & diarrhea
• Increase in kidney function

  Increase of urine
• Renin-Angiotensin-Aldosterone System


  Helps maintain intravascular fluid balance & blood pressure
• ADH


  Made in hypothalamus, stored in posterior pituitary gland, function is to regulate water excretion from kidneys
• Malfunction with ADH


  Endocrine Disorder