Acid Base Balance Flashcards
How does alkalaemia effect Ca?
Lowers free Ca by causing Ca ions to come out of solution = increases neuronal excitability = tetany
Outline some physiological effects of acidaemia
Increases [K] = effects cardiac muscle excitability = arrhythmia
Increasing [H] = denatures proteins, effects muscle contractility, glycolysis, hepatic function
How do the kidneys recover HCO3-?
Recovered in the PCT via Na/H exchanger = expelling H+, reacts with bicarb to form water and CO2, CO2 absorbed into the cell, reacts with H2O to form bicarb, bicarb exported via basolateral membrane to capillaries
How does the proximal tubule create HCO3?
AA glutamine broken down to give HCO3- and ammonium (NH4+)
Outline the H+ buffering systems in the kidney
Distal tubule = H excreted by H+ATPase, combines hydrogen phosphate
Proximal tubule = H excreted, combines with ammonia to produce ammonium (trapped in lumen)
How does pH effect the movement of K in the kidney?
Acidosis = deceased K excretion in distal nephron = hyperkalaemia
Alkalosis = enhanced K excretion in distal nephron = hypokalaemia
Outline how the levels of K effect tubular cells in the kidney?
Hypokalaemia = HCO3 recovery = metabolic alkalosis
Hyperkalaemia = HCO3 excretion = metabolic acidosis
How does hypoventilation effect acid base balance?
Hypercapnia = fall in plasma pH = resp acidosis
How does hyperventilation effect acid base balance?
Hypocapnia = rise in pH = resp alkalosis
Outline the characteristics of respiratory acidosis
High pCO2
Normal HCO3
Low pH
Outline the characteristics of respiratory alkalosis
Low pCO2
Normal HCO3
Raised pH
Outline the characteristics of compensated respiratory acidosis
High pCO2
Raised [HCO3]
Relatively normal pH
Outline the characteristics of compensated respiratory alkalosis
Low pCO2
Lowered [HCO3]
Relatively normal pH
Outline the characteristics of metabolic acidosis
Low [HCO3]
Low pH
Normal pCO2
Renal cause = normal anion gap (HCO3 replaced by Cl-)
Metabolic cause = increased anion gap (HCO3 replaced by another unmeasured anion)
Outline the characteristics of metabolic alkalosis
Raised [HCO3]
Rise in pH
Normal pCO2
What is the anion gap?
Diff between measured cations and anions
Outline the characteristics of compensated metabolic acidosis
Low HCO3
Lowered pCO2
Nearer normal pH
Peripheral chemoreceptors (carotid bodies) = detect pH drop = ventilation = decreased pCO2
What conditions lead to respiratory acidosis?
Type 2 resp failure = alveoli cannot be properly ventilated
E.g. Severe COPD, severe asthma, drug overdose
What conditions lead to respiratory alkalosis?
Hyperventilation = anxiety/panic attacks
Type 1 resp failure = hyperventilation in response to long-term hypoxia
What conditions lead to metabolic acidosis with an increased anion gap?
Increased anion gap = indicated metabolic prod of an acid
Keto-acidosis
Lactic acidosis
Uraemic acidosis
What conditions lead to metabolic acidosis with a normal anion gap?
Normal anion gap = HCO3 is replaced by Cl-
Renal tubular acidosis
Severe persistent diarrhoea, loss of HCO3
What conditions lead to metabolic alkalosis?
Severe prolonged vomiting = loss of H+K depletion
Certain diuretics
