ACIDBASE ABNORMALITIES

1
ACID-BASE ABNORMALITIES

• AIMS
• What are the major acid base disturbances?
• How are these disturbances compensated?

2
ACID- BASE DISTURBANCES

• ACIDOSIS
• Respiratory (CO2 retention- PACO2 )
• causes- hypoventilation,COPD, ventilatory
  depression, neuromuscular disease
• compensation- lose more H conserve HCO3- via
  kidney,
• Metabolic (excess acid production- H)
• causes- kidney failure, lactic acidosis, loss of
  base (HCO3-)
• compensation- high H stimulates ventilation, so
  PACO2 reduced

3
ACID- BASE DISTURBANCES

• ALKALOSIS
• Respiratory (excess CO2 loss due to high
  ventilation- PACO2, bicarbonate normal)
• causes- hypoxaemia, high altitude,
  anxiety,mechanical ventilation
• compensation- decreased loss of H increased
  excretion of HCO3- from kidney
• Metabolic (increase in base- HCO3- , lower H)
• causes- loss of acid eg vomiting,excessive loss
  of ve ions via kidney, hypokalaemia
• compensation- Hypoventilation, HCO3-excretion

4
CONCLUSIONS

• Disturbances can be respiratory
• defects in ventilation
• increase in PCO2- respiratory acidosis
• decrease in PCO2- respiratory alkalosis
• Disturbances can be metabolic
• excess acid production or loss- metabolic
  acidosis and alkalosis
• gain or loss of HCO3-..metabolic alkalosis and
  metabolic acidosis
• Compensation varies whether disturbance is acute
  or chronic
• Acute respiratory disturbances are initially
  compensated by kidney
• acute metabolic disturbances are compensated by
  the lungs
• Chronic changes are compensated mainly by kidney