ChemPath: Acid-Base Handling Flashcards
What is the normal range for H+ concentration?
35-45 mmol/L in ECF
What equation links H+ concentration to pH?
pH = log1/[H+]
What are the three main physiological buffers?
- Bicarbonate
- Haemoglobin
- Phosphate
NOTE: also protein and bone
What is the rate of production of H+ ions per day?
50 - 100 mmol/day
Describe how the kidneys excrete H+ ions.
Bicarbonate is regenerated through the production of carbonic acid
Describe how H+ ions pass through the renal epithelial membrane.
H+ ions cannot pass through the membrane itself so a transport system is necessary (Na+/H+ exchange)
What is the rate of production of carbon dioxide per day?
20,000-25,000 mmol/day
Describe the respirtaory control over carbon dioxide.
- Respiratory is controlled by chemoreceptors in the hypothalamic respiratory centre
- An increase in CO2 will stimulate an increase in ventilation which then brings down CO2 concentration
What information is provided by ABGs?
- pO2
- pCO2
- pH
What is the primary abnormality in metabolic acidosis? List three causes with examples.
Primary abnormality is increased H+ (with decreased bicarbonate)
Caused by:
- Increased H+ production (e.g. DKA)
- Decreased H+ excretion (e.g. renal tubular acidosis)
- Bicarbonate loss (e.g. intestinal fistula)
What is the primary abnormality in respiratory acidosis? List three causes with examples.
Primary abnormality is increased CO2 (therefore, increased H+) and a slight increase in bicarbonate
Caused by:
- Decreased ventilation
- Poor lung perfusion
- Impaired gas exchange
NOTE: metabolic compensation is slower than respiratory compensation
What is the primary abnormality in metabolic alkalosis? List three causes.
Primary abnormality is decreased H+ (with increased bicarbonate)
Caused by:
- H+ loss (e.g. pyloric stenosis)
- Hypokalaemia
- Ingestion of bicarbonate
What is the primary abnormality in respiratory alkalosis? List three causes.
Primary abnormality is reduced CO2
If prolonged, this can lead to reduced renal H+ excretion and reduced bicarbonate generation
Can be caused by hyperventilation due to:
- Voluntary
- Artificial ventilation
- Stimulation of the respiratory centre
What derangement of acid-base balance would be caused by pyloric stenosis?
Metabolic alkalosis due to loss of H+ from profuse vomiting
Which condition classically causes a mixed respiratory alkalosis and metabolic acidosis?
- Aspirin overdose
- Aspirin stimulates ventilation and reduces renal excretion of H+
