T3 L10: Regulation of homeostasis - acid-base balance

• What are the types of buffer systems?

  carbonic anhydrase / bicarbonate

  protein

  phosphate
• How do the kidneys and the lungs regulate blood pH together?

  HCO3- in kidneys

  CO2 in lungs

  
• Inverse relationship between pH and plasma concentration of CO2
• How does the renal regulation of acid-base balance work?

  HCO3- in filtrate reabsorbed

  H+ secreted

  if pH of ECF falls (acidaemia) → more H+ secreted into filtrate & reabsorption of HCO3- into ECF → pH increases
• Bicarbonate → blood (kan)

  H+ → urine
• What happens in intercalated cells in response to acidaemia in distal tubule & CD?

  H+ secretion into tubular fluid

  HCO3- reabsorption from tubular fluid

  HCO3- generation from amino acids

  
• What are the respiratory and metabolic causes of acidosis?

  Respiratory:

  • inadequate ventilation
  • acute / chronic

  Metabolic:

  • all conditions other than respiratory that decrease pH
  • always CHRONIC
• How can you gain H+?

  CO2 in blood

  Non-volatile acids from metabolism

  Loss of HCO3- in diarrhoea / non-gastric GI fluids

  Loss of HCO3- in urine
• How does the body respond to acidosis?

  generation of HCO3- by kidneys

  increased respiration rate
• What is the treatment of respiratory acidosis?

  restore ventilation

  treat underlying dysfunction / disease

  give IV lactate solution (converted to HCO3- buffer in liver)
• What is the treatment of metabolic acidosis?

  give IV isotonic HCO3-

  give IV lactate solution (buffer)
• What are the respiratory and metabolic causes of alkalosis?

  Respiratory:

  • hyperventilation
  • acute / chronic

  Metabolic:

  • results from all conditions other than respiratory that increase pH
  • always CHRONIC
• How can you suffer a loss of H+?

  use of H+ in metabolism of organic anions

  loss of H+ in vomit

  loss of H+ in urine

  hyperventilation
• What is the treatment of respiratory alkalosis?

  treat underlying cause

  breathe into paper bag (increases pCO2)

  give IV Cl- containing solution (increased HCO3- excretion)
• What is the treatment of metabolic alkalosis?

  Give electrolytes to replace those lost

  IV Cl- solution

  treat underlying disorder
• What is the Siggaard-Andersen Acid-Base chart?

  A tool for interpreting blood gas results.