Acid-base Balance Flashcards
What donates free hydrogen ion when dissolved in water?
Acid
What accepts free hydrogen ion when dissolved in water?
Base
What is normal blood pH?
7.35-7.45 (slightly acidic)
What does normal body metabolism produce that needs to be removed & what are examples of these?
Acid
- Carbonic acid from CO2 –aerobic respiration
- Lactic acid – from anaerobic respiration (lactoacidosis)
- Ketones – from use of lipids as an energy source, eg during starvation or diabetes (ketoacidosis)
- Sulphuric acid from oxidation of sulphur containing amino acids
- Phosphoric acid from the breakdown of phosphoproteins and ribonucleotides
What are examples of buffer system?
- Bicarbonate
- Phosphate
- Protein
- Respiratory
- Renal
What is a chemical buffer system?
- System to maintain pH level
- Buffers react with a relatively strong acid (or base) to replace it with a relatively weak acid (or base)
What is the buffer equation?
CO2 + H2O H2CO3 H + HCO3-
What is the bicarbonate carbonic acid buffer?
- Catalysed by carbonic anhydrase in red blood cells
- Regulates pH by maintaining the ratio of 20 bicarbonate ions:1 carbonic acid
What is the respiratory regulation of hydrogen?
- Physiological buffer (slower effect)
- Eliminate carbon dioxide (an acid)
- During CO2 unloading (at lungs), reaction shifts
to left (and H+ is incorporated into H2O) - During CO2 loading (at tissues), reaction shifts to right (and H+ is buffered by proteins
How does the respiratory buffer get triggered and respond?
- Medullary and peripheral chemoreceptors detect high levels of carbon dioxide and hydrogen in the blood
- Increase respiratory rate & depth
- Remove carbon dioxide from blood, reducing hydrogen concentration
How does hypoventilation affect pH balance?
Hypoventilation causes respiratory acidosis if pH < 7.35 due to the increase in carbon dioxide driving the buffer system to the right, thereby raising hydrogen ion concentrations
How does hyperventilation affect pH balance?
Hyperventilation causes respiratory alkalosis if pH > 7.45 from too much loss of carbon dioxide driving the buffer system to the left, thereby lowering hydrogen ion concentrations
How does renal regulation affect pH balance?
- Kidney can excrete and retain bicarbonate and hydrogen ions, influencing pH
- Response take several hours
How is pH compensated?
If either the lungs or kidney experience impaired function, the other organ compensate
What encompasses acid-base disorders?
Can be:
- Acidosis or alkalosis
- Respiratory or metabolic
- Partly or fully compensated or uncompensated
- Or it can have both a respiratory & metabolic cause
What is respiratory acidosis and what are the levels & causes?
- Impaired respiratory function causing low pH
- In uncompensated respiratory acidosis, pH less than 7.35, carbon dioxide levels will be elevated while bicarbonate levels are now
Causes: - Inadequate oxygen supply causes hypoxia & hypoxemia
- Reduced ability to regulate pH
What is metabolic acidosis and what are the levels & causes?
- From cause that is not respiratory e.g. due to excessive buffering or loss of buffer causing low bicarbonate levels
- In uncompensated metabolic acidosis, pH less than 7.35, low bicarbonate, normal carbon dioxide
Causes: - Severe diarrhoea
- Renal disease
- Diabetes
How can acidosis cause hyperkalemia?
- Increased hyrogen ions exchange causes increase potassoim
1) Hydrogen enters cells in exchanges for potassium leaving into ECF
2) Acidosis cause decreased secretion of potassium in kidney - Hyperkalemia can cause cardiac arrhythmias
What is respiratory alkalosis and what are the levels & causes?
- High pH from impaired respiratory function
- In uncompensated respiratory alkalosis pH is above 7.45, low carbon dioxide, normal bicarbonate
Causes are hyperventilation causes by: - Hypoxemia
- Strong emotions
- Brain tumour or injury to respiratory controls
What is metabolic alkalosis and what are the levels & causes?
- Alkalosis without respiratory cause
- In uncompensated metabolic alkalosis, pH is above 7.45, high bicarbonate, normal carbon dioxide
Causes: - Vomiting or gastric suctioning
- Overdose of antacids
- Adrenal tumours over secreting aldosterone
How do you identify compensation of acid-base imbalances?
The levels will opposes the observed deviation in pH
What is the compensation of respiratory acidosis?
- Kidneys retain bicarbonate and secrete hydrogen
- Normal/acidic pH, high carbon dioxide & high bicarbonate
What is the compensation of respiratory alkalosis?
- Kidneys excrete bicarbonate and retain hydrogen
- Normal/basic pH, low carbon dioxide & low bicarbonate
What is the compensation of metabolic acidosis?
- Respiratory system increases respiratory rate & depth since increased hydrogen levels stimulate respiratory centres
- Normal/acidic pH, low bicarbonate & low carbon dioxide
What is the compensation of metabolic alkalosis?
Respiratory system decreases respiratory rate & depth since low hydrogen levels decrease respiratory drive
- Normal/basic pH, high bicarbonate & high carbon dioxide
How can disorders be identified?
ABG - arterial blood gases
What is the normal carbon dioxide level?
35-45 mmHg
What is the normal bicarbonate level?
80-100 mmHg
What is the normal oxygen level?
22-32 mmol/L
What is the normal oxygen saturation level?
95-99%
