Acid-Base Handling Flashcards
[H+] in extracellular fluid
35-45nmol/L
pH range
7.35-7.46
Determining pH
Log1/[H+]
How is H+ excreted
Kidneys
What produces H+ ions
Metabolism of proteins, carbohydrates and fats produce carbon dioxide, water and hydrogen ions
What are the buffers in the body (5)
Bicarbonate (ECF, glomerular filtrate) Haemoglobin (RBCs) Phosphate (renal tubular fluid, intracellular fluid) Protein Bone
What do buffers do
Mop up hydrogen ions
What is the most important buffer in the body
Bicarbonate
What is required to maintain homeostasis
Kidneys need to excrete hydrogen ions and regenerate bicarbonate
How are bicarbonate ions regenerated
Using carbonic acid
What transport system is used to excrete hydrogen ions in the kidney
Sodium transport system
How is CO2 excreted
Lungs
How is breathing controlled
Chemoreceptors in the hypothalamic respiratory centre
In health, any increase in CO2 stimulates respiration thus tending to maintain a stable concentration of CO2.
Causes of metabolic acidosis (3)
Increased H+ production (DKA) Decreased H+ excretion (renal tubular acidosis) Bicarbonate loss (intestinal fistula)
High H+
Low HCO3
Metabolic acidosis
High H+
Low HCO3
Low CO2
Compensated metabolic acidosis
High H+
High HCO3
High CO2
Respiratory acidosis
High H
Very High HOC3
High CO2
Chronic respiratory acidosis
Causes of respiratory acidosis (3)
Decreased ventilation
Poor lung perfusion
Impaired gas exchange
e.g. pneumonia
Chronic respiratory acidosis - COPD
Causes of metabolic alkalosis (4)
H+ loss (pyloric stenosis)
Hypokalaemia
Ingestion of bicarbonate
Anaerobic exercise
Low H+
High HCO3
Metabolic alkalosis
Low H+
High HCO3
High CO2
Compensated metabolic alkalosis
Causes of respiratory alkalosis
Due to hyperventilation (voluntary, artificial ventilation, stimulation of respiratory centre)
e.g. Panic attack
Low H+
Low HOC3
Low CO2
Chronic respiratory alkalosis
What does H+/pH indicated
Overt acidosis/alkalosis
What does pCO2 indicated
Respiratory disturbance (primary or secondary)
What does pO2 indicate
Respiratory function and tissue oxygenation
How are bicarbonate, pCO2 and pH interrelated
{H+} = k x pCO2/[HCO3-]
