Week 6 - Acid Base Balance Flashcards
What is alkalaemia/ acidaemia?
- pH greater than 7.45 -> alkalaemia
- pH less than 7.35 -> acidaemia
What is the effect of alkalaemia on calcium ions? What is the consequence of this?
- Lowers free calcium by causing the ions to come out of solution -> bound to albumin instead of H
- Leads to increased neuronal excitability causing paresthesia and tetany
What effect does acidaemia have on K? What is the major consequence of this?
-Causes hyperkalaemia as H+ are taken into the cell in exchange for K+ in order to lower H+ conc
Why is a lower pH disruptive?
-Denatures proteins causing enzyme disturbances and affecting muscle contractility, glycolysis and hepatic function
Below what pH is life threatening?
-7.0
How is plasma pH determined?
-Ratio of [HCO3]/CO2
What is the henderson-hesselbach equation?
- pH=pK+log([hco3]/(CO2 x0.23))
- pK is a constant = 6.1 at 37 degrees
What is the normal ratio of HCO3:CO2?
-20:1
What ultimately determines the pCO2?
-Respiration controlled by the chemoreceptors
What controls the concentration of HCO3?
-Kidneys
What is the effect of hypoventilation on partial pressures and acid base balance?
-Decreased pO2, increased pCO2 -> respiratory acidosis
What is the effect of hyperventilation on partial pressures and acid base balance?
-Increased pO2, decreased pCO2 -> respiratory alkalosis
What controls respiration?
- Detectoion of pO2 and pCO2 by peripheral and central chemoreceptors respectively
- Send information to respiratory centre in brain
How are respiratory changes in acid base balance corrected?
-Change in ventilation rate
How are respiratory changes in acid base balance compensated?
-Change in [HCO3]
What produces the main source of bicarb in the blood?
-RBCs
When is metabolic acidosis caused?
-When there is an increase in the production of acids produced by tissues which reacts with HCO3 and decreases pH