Acid Base Homeostasis Flashcards
Define an Acid and Base
Acid - Defined as any chemical substance that can donate a proton. Base - Any chemical that can accept a proton
How can you calculate the pH of plasma?
What is the pKa?
Defined as the pH at which 50% is ionised and 50% is unionised in the reaction
What is the acid-base equation for physiological mechanisms
What happens if there is a rise or fall in hydrogen ions?
Rise - Equation is driven to the left. Falls - Equation is driven to the right
What is the effects of changing the pH on this equation
Increasing the pH over the pKa will mean the equation is shifted to the right. If the pH is decreased below the pKa then the equation will be shifted to the left.
What are some of the causes of Acid-Base disturbances
- Increased CO2, decreased CO2, increased non-volatile acid/decreased base and increased base/decreased non-volatile acid
How can you differentiate between respiratory and metabolic disorders
Resp - When the primary change is to CO2 levels. Metabolic - Change to bicarbonate levels
Acidosis can be caused by what?
Rise in PCO2 or a fall in HCO3
Alkalosis can be caused by what?
Fall in PCO2 or a rise in HCO3
What changes in ions is respiratory acidosis caused by?
Increased in PCO2 via: - Hypoventilation (less CO2 blown off), - Ventilation-perfusion mismatch, - Reduced lung diffusion capacity
What is the compensation method for respiratory acidosis?
Renal compensation - Increased HCO3- reabsorption and increased HCO3- production, raising the pH towards normal.
What are some of the clinical causes of respiratory acidosis?
- COPD, - Blocked airway, - Lung collapse, - Injury to chest wall - Drugs that reduce respiratory drive, eg, morphine
What changes in ions is respiratory alkalosis caused by?
Decrease in PCO2 which is generally caused by alveolar hyperventilation, this will cause a decrease in H+ concentration and thus rise in pH
Describe the renal compensation method for respiratory alkalosis
Reduced HCO3- reabsorption and reduced HCO3- production this causes a fall in plasma HCO3- levels which compensates for the lower H+ conc so pH moves towards normal