base excess, arterial blood, calculated
Blood gas measurements are used to evaluate your oxygenation and acid/base status. They are typically ordered if you have worsening symptoms of an acid/base imbalance, difficulty breathing, or shortness of breath. Abnormal results of any of the blood gas components may mean that: you are not getting enough oxygen, not getting rid of enough carbon dioxide, and there is a problem with kidney function.
- Respiratory acidosis is characterized by a lower pH and an increased PCO2 and is due to respiratory depression - not enough oxygen in and carbon dioxide out. This can be caused by many things, including pneumonia, chronic obstructive pulmonary disease (COPD), and over-sedation from narcotics.
- Respiratory alkalosis, characterized by a raised pH and a decreased PCO2, is due to over ventilation caused by hyperventilating, pain, emotional distress, or certain lung diseases that interfere with oxygen exchange.
- Metabolic acidosis is characterized by a lower pH and decreased HCO3-; the blood is too acidic on a metabolic/kidney level. Causes include diabetes, shock, and renal failure.
- Metabolic alkalosis is characterized by an elevated pH and increased HCO3- and is seen in hypokalemia, chronic vomiting (losing acid from the stomach), and sodium bicarbonate overdose.