Flashcards in Urinary 5 - Acid-base balance Deck (27):
What is the normal plasma pH range?
7.35 - 7.45
Plasma pH < 7.35
Plasma pH > 7.45
Why is the acid-base balance of the body dependent on the kidneys and the lungs?
Kidneys = responsible for HCO3- (base) regulation
Lungs = responsible for CO2 (acid) regulation
Why does Alkalosis lead to paraesthesia and/or tetany?
Alkalosis leads to lowered free Ca2+ (increased binding to plasma proteins), which increases neuronal excitability
Why does alkalosis has a high mortality (if pH > 7.65)?
Alkalosis lowers free Ca2+ which increases neuronal excitation leading to tetany. If tetany of respiratory muscles --> lead to death
Describe the pathophysiology of respiratory alkalosis:
Hyperventilation leads to hypocapnia = increased pH
How does the body compensate for alkalosis?
Central chemoreceptors detect hypocapnia and reduce ventilation rate (limited by tissue O2 demand)
Kidney tubular cells decrease H+ excretion, and decrease HCO3- recovery
What are the main causes of Metabolic alkalosis?
Loss of H+ - vomiting, diarrhoea, increased secretion (Aldosterone)
Shift of H+ into ICF - hypokalaemia
Increased [HCO3-] - renal failure
Metabolic alkalosis can lead to what kind of K+ disorder?
pH < 7.35
At what point is acidosis life threatening?
If pH < 7.0
Describe the pathophysiology of respiratory acidosis:
Hypoventilation = hypercapnia = decreased pH
How does the body compensate for acidosis?
Central chemoreceptors detect decreased pH, and increase respiratory rate
Kidneys increase HCO3- recovery and production
Where does the majority of HCO3 reabsorption occur?
What enzyme catalyses the conversion of H+ + HCO3- to H2O + CO2?
List the 3 ways in which the kidneys increase production of HCO3-:
1 - increased conversion of CO2 + H2O into H+ and HCO3- (due to increased metabolic rate = increased CO2)
2 - From amino acids in the PCT
3 - Buffering of H+ via HPO4(2-) increases conversion of CO2 + H2O into H+ and HCO3- in DCT
What in the tubular lumen buffers H+ allowing the increased production of HCO3-?
What are the main causes of metabolic acidosis?
Increased metabolic production of acid - lactic acidosis, ketoacidosis, damaged muscle cells (trauma/tumour)
Ingestion of acid
Increased HCO3- loss - renal failure, diarrhoea
Decreased H+ excretion - renal failure
What is the Anion Gap?
Difference between [Na+] + [K+] and [Cl-] + [HCO3-]
What is the normal Anion Gap?
10-15 mM (usually less anions than cations)
What type of acid-base disorder can cause an increased anion gap?
A decreased anion gap is rare, but what can cause it?
Paraprotein anaemia - Multiple myeloma
Why is metabolic acidosis associated with an increased anion gap?
Metabolically produced acids have an associated anion (ie Lactate) which replaces HCO3- in plasma = decreased pH
What kind of acid-base disorder is associated with HYPOkalaemia?
What kind of acid-base disorder is associated with HYPERkalaemia?