Meaning of HCO3 index in arterial blood gas results

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1. What is an arterial blood gas test?

Arterial blood gas is a test to evaluate the acid-base balance, ventilation status and blood oxygenation status of the patient.
The test will provide parameters such as blood pH , arterial blood carbonic pressure (PaCO2), plasma bicarbonate concentration HCO3-, arterial blood oxygen saturation (SaO2) and specific pressure fraction of dissolved oxygen in arterial blood (PaO2). Blood gas results are normal when:
pH: 7.35-7.45 PaCO2 : 35-45 mmHg HCO3-: 22-26 mmol/l PaO2: 80-100mmHg SaO2: 95-100%.

Arterial blood gas testing is indicated in diagnosis, monitoring and treatment, especially for critically ill patients. For patients requiring mechanical ventilation, the results of arterial blood gas testing performed prior to mechanical ventilation will help to adjust ventilator parameters.

2. Meaning of HCO3 in blood gas results

Most of the arterial blood gas results calculate the value of HCO3- and residual alkalinity in order to find out the metabolic causes in acid-base disorders, or the compensatory mechanism of metabolic acid-base disorders. HCO3- and excess alkalinity are particularly useful when the cause of acid-base disturbance is a combination of metabolic and respiratory problems. Laboratory results for normal HCO3- and residual alkalinity may rule out metabolic acid-base disorder.
To evaluate acid-base, it is necessary to consider the following indicators:
pH: Acidic blood when pH < 7.35, alkaline blood pH> 7.45. Within 7.35-7.45 may be normal or mixed acid-base disorder. PaCO2 and HCO3-: To determine whether the acid-base disorder is due to metabolic or respiratory causes.

If the metabolic cause is primary, evaluation should be made for compensatory respiration. In case the results show metabolic acidosis, the anion gap (AG) should be calculated to find the cause. Unmeasurable residual anions are responsible for acidosis such as lactic acidosis, ketoacidosis, renal failure, and poisoning. Metabolic acidosis with a normal anion gap is associated with hyperchloremia, caused by excessive fluid infusion, as well as gastrointestinal loss of HCO3- through diarrhea or renal loss of HCO3-. In summary, the HCO3- value in arterial blood gas test results is intended to identify metabolic causes in acid-base disorders, or compensatory mechanisms of metabolic acid-base disorders.
Any questions that need to be answered by a specialist doctor as well as customers wishing to perform an arterial blood gas test at Vinmec International General Hospital, you can contact Vinmec Health System worldwide. country or register online HERE.

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