Acid-Base Handling Flashcards
What is the normal range of [H+]?
35-45 nmol/l
What is normal pH?
7.35-7.45
How are H+ ions produced?
Metabolism of proteins, carbohydrates and fats produce carbon dioxide, water and hydrogen ions.
How are H+ ions excreted?
Excetion by the kidney
How much H+ is produced per day?
50-100 mmol/day
What is the equation of the role of H+ within the body?
H+ + HCO3- H2CO3 CO2 + H2O
What are limitations of buffering against H+?
ECF buffering of hydrogen is at the expense of bicarbonate.
Bicarbonate buffering of H+ is only effective in the short term.
To maintain normal homeostasis the kidney needs to excrete hydrogen ions and regenerate bicarbonate.
How is CO2 produced?
Metabolism of proteins, carbohydrates and fats produce carbon dioxide, water and hydrogen ions.
How is CO2 excreted?
Lungs
How much CO2 is produced per day?
20,000-25,000 mmol/day
What is CO2 production and excretion controlled by?
Respiration is controlled by chemoreceptors in the hypothalamic respiratory centre. In health any increase in CO2 stimulates respiration thus tending to maintain a stable concentration of CO2.
What is metabolic acidosis?
Primary abnormality is increased H+ (decreased pH) with decreased bicarbonate.
What can metabolic acidosis be due to?
- Increased H+ production e.g. Diabetic ketoacidosis
- Decreased H+ excretion e.g. Renal tubular acidosis
- Bicarbonate loss e.g. Intestinal fistula
What is compensated metabolic acidosis?
Increase in H+ stimulates the respiratory centre.
Identified by a fall in pCO2.
H+ returns towards normal.
What is acute respiratory acidosis?
Primary abnormality is increased CO2, producing increased H+ (decreased pH) and a slight increase in bicarbonate (2-4 mmol/L).
What are causes of acute respiratory acidosis?
Decreased Ventilation
Poor Lung Perfusion
Impaired Gas Exchange
What is chronic respiratory acidosis?
Over the course of a few days this leads to increased renal excretion of H+ combined with generation of bicarbonate. H+ may return to near normal but pCO2 and bicarbonate remain elevated.
What is metabolic alkalosis?
Primary abnormality is decreased H+ (increased pH) with increased bicarbonate.
What are causes of metabolic alkalosis?
H+ loss (e.g. pyloric stenosis)
Hypokalaemia
Ingestion of Bicarbonate
What are causes of respiratory alkalosis?
Due to Hyperventilation
- Voluntary
- Artificial ventilation
- Stimulation of respiratory centre
What happens in chronic respiratory alkalosis?
If prolonged this leads to decreased renal excretion of H+ and less bicarbonate generation. H+ may return to near normal but pCO2 and bicarbonate remain low.
