WEEK 2 (FLUIDS, ACID/BASE, STARLINGS LAW)

• What is ACIDOSIS?

  • state where there is too much H+ or CO2 cannot be removed
  • occurs when bicarbonate is lost from the ECF
  • associated with tachypnoea, ALOC and lethargy
  • pH below 7.35

  COMMON CAUSES:

  • resp depression
  • chest disorders
  • disorders of lung parenchyma
  • pneumonia, pulmonary oedema

  RESP:

  • hypoventilation
  • asphyxiation
  • COPD

  METABOLIC:

  • shock
  • liver + renal failure
  • hyperglycaemia + seizures
• How does O2 help with shock?

  As pH decreases, acidosis worsens. CO2 binds more strongly to haemoglobin so more can be removed. This means less O2 is bound to it so providing supplementary O2 it helps provide more to the tissues
• What is ALKALOSIS?

  • pH above 7.45
  • caused by excessive loss of H+ ions or an increase in bicarbonate
  • electrolyte imbalances can be profound

  RESP:

  • hyperventilation syndrome
  • metabolic acidosis
  • excessive loss of CO2 via hyperventilation

  METABOLIC:

  • vomiting + diarrhoea
  • toxic alkali ingestion
  • diuresis
• What are buffer systems?

  • act to resist changes to pH
  • ALKALOSIS = release H+ ions due to high pH
  • ACIDOSIS = remove H+ ions due to low pH
  • react quickly but limited capacities
• What are types of BUFFER SYSTEMS and WHERE are they found?

  1. phosphate = ICF
  2. protein = ICF + ECF
  3. bicarbonate = ECF
• What is the equation for the PHOSPHATE buffer system?

  dihydrogen phosphate = hydrogen + hydrogen phosphate
• What is the equation for the BICARBONATE buffer system?

  carbon dioxide + water = carbonic acid = hydrogen + bicarbonate
• What is the PROTEIN buffer system?

  AMINO = takes in H+ ions when pH is low (when acidotic)

  CARBOXYL = releases H+ ions when pH is high (when alkalotic)
• What are the different types of fluid movement?

  1. diffusion (high solute to low solute)
  2. facilitated (high to low, no ATP)
  3. active (against, low to high, needs ATP)
  4. osmosis (high to low solute until equal)
• What is osmotic pressure?

  The drawing of water. The solute that cannot diffuse, draw water towards it. The strength is determined by number. The bigger the difference, the bigger the pressure.
• What are electrolytes and non-electrolytes?

  ELECTROLYTES = molecules that conduct electricity when dissolved in water. Dissolve into ions (positive or negative)

  NON-ELECTROLYTES = compounds that do not dissolve into ions in water
• What are the 4 functions of electrolytes?

  1. regulation of essential minerals
  2. influence osmosis
  3. maintain acid/base balance
  4. create action potentials for neuotransmission
• What is the sodium/potassium pump?

  Sodium is expelled from the cell by binding to a cell membrane protein and a protein pump. This triggers the use of ATP which changes the shape of the protein pump and sodium is expelled out. Extracellular potassium binds to the pump and resets the shape. Causing potassium to be released back into the cell. Sodium and potassium leak slowly, but continuously through leakage channels and the plasma membrane. The pump is used to maintain normal concentrations.
• Where are the different electrolytes commonly found?

  Sodium = plasma + interstitial

  Potassium = ICF

  Calcium = plasma + interstitial

  Magnesium = ICF

  Bicarbonate = plasma + interstitial

  Chloride = plasma + interstitial

  Hydrogen phosphate = ICF
• What are the different properties of water?

  1. solvent
  2. reactions
  3. heating
  4. lubrication
  5. suspension
  6. cooling
• What is INTRACELLULAR FLUID?

  • the largest compartment
  • all fluid housed inside of cells
  • stable
• What is EXTRACELLULAR FLUID?

  • all fluid not in cells
  • variable, constantly changing volumes
  • interstitial, plasma and transcellular
• What is the distribution of water?

  ICF = 66%

  ECF = 33%

  Of the ECF:

  Interstitial = 75%

  Plasma = 21%

  Transcellular = 4%
• What is STARLING'S LAW OF CAPILLARIES?

  • The rate and direction of fluid movement across the capillary membrane are determined by the balance between hydrostatic and osmotic pressures
• What is the STARLING'S LAW EQUATION?

  NFP = BHP - BOP
• What are the different pressures?

  HYDROSTATIC:

  • the pressure exerted by a fluid as it pushes against a 'container'

  BHP:

  • pressure exerted by the blood against the wall of a capillary
  • outward pressure

  BOP:

  • determined by osmotic concentration gradients - driven by the difference in the solute to water on either side of the membrane
  • pulling/inward pressure
• What are FILTRATION, NFP, and REABSORPTION?

  FILTRATION:

  • direction of flow out of the capillary
  • arterial end of the capillary
  • more filtration overall = more fluid leaving than returning (NFP = +)

  NFP:

  • net pressure causing filtration (out of the capillary)

  REABSORPTION:

  • direction of flow into the capillary
  • venous end of the capillary
  • more reabsorption overall = more fluid returning capillary than leaving (NFP = -)