What is Arterial Blood Gas?

(1) pH: Reference value 7.35-7.45. <7.35 is acidemia, and> 7.45 is alkalemia. But normal pH does not completely rule out acid-base imbalance. (2) Carbon dioxide partial pressure (PCO2): The reference value is 4.65-5.98kPa (35-45mmHg), multiplied by 0.03 is the H2CO3 content. Exceeding or falling below the reference value is called hypercapnia and hypocapnia. > 50mmHg risk of suppressing the respiratory center. It is the main indicator for judging various types of acid-base poisoning. (3) Total carbon dioxide (TCO2): The reference value is 24-32mmHg, which represents the sum of CO2 and HCO3 in the blood. It is affected by both breathing and metabolism in vivo. Significantly decreased during metabolic acidosis and significantly increased during alkalosis. (4) The reference value of oxygen partial pressure (PO2) is 10.64-13.3kpa (80-100mmHg). Respiratory failure is below 60mmHg, and <30mmHg can be life-threatening. (5) The reference value of oxygen saturation (SatO2) is 3.5kPa (26.6mmHg). (6) The actual bicarbonate (AB) reference value is 21.4-27.3mmol / L, and the standard bicarbonate (SB) reference value is 21.3-24.8mmol / L. AB is an important indicator of metabolic acid-base imbalance in the body. SB calculated under specific conditions also reflects metabolic factors. The two are normal for acid-base stabilization. Both are low for metabolic acidosis (uncompensated), both are high for metabolic alkalosis (uncompensated), AB> SB is respiratory acidosis, and AB <SB is respiratory alkalosis. p> (7) Residual base (BE): Reference value3- + 3mmol / L, positive value indicates increase, negative value decreases. (8) Anion gap (AG): The reference value is 8-16mmol / L, which is an important indicator for early detection of mixed acid-base poisoning. Judging the acid-base imbalance should first understand the clinical situation, generally based on pH, PaCO2, BE (or AB) to determine the acid-base imbalance, according to PaO2 and PaCO2 to determine hypoxia and ventilation. A pH outside the normal range indicates an imbalance. But pH may still have acid-base imbalance. PaCO2 above normal indicates respiratory acid-base imbalance, and BE above normal indicates metabolic acid imbalance. However, blood gas and acid-base analysis sometimes need to be combined with other tests and combined with clinical dynamic observation to get a correct judgment.

Arterial blood gas analysis refers to the technical process of analyzing various types of gases and different types of gases and acid-base substances in liquids. The specimens can come from blood, urine, cerebrospinal fluid, and various mixed gases, but the most clinical application is blood. Blood samples include arterial blood, venous blood, and mixed venous blood, among which the application of arterial blood gas analysis is the most common.

Name

Arterial blood gas analysis

category

blood

Normal arterial blood gas analysis

(1) pH: Reference value 7.35-7.45. <7.35 is acidemia, and> 7.45 is alkalemia. But normal pH does not completely rule out acid-base imbalance. (2) Carbon dioxide partial pressure (PCO2): The reference value is 4.65-5.98kPa (35-45mmHg), multiplied by 0.03 is the H2CO3 content. Exceeding or falling below the reference value is called hypercapnia and hypocapnia. > 50mmHg risk of suppressing the respiratory center. It is the main indicator for judging various types of acid-base poisoning. (3) Total carbon dioxide (TCO2): The reference value is 24-32mmHg, which represents the sum of CO2 and HCO3 in the blood. It is affected by both breathing and metabolism in the body. Significantly decreased during metabolic acidosis and significantly increased during alkalosis. (4) The reference value of oxygen partial pressure (PO2) is 10.64-13.3kpa (80-100mmHg). Respiratory failure is below 60mmHg, and <30mmHg can be life-threatening. (5) The reference value of oxygen saturation (SatO2) is 3.5kPa (26.6mmHg). (6) The actual bicarbonate (AB) reference value is 21.4-27.3mmol / L, and the standard bicarbonate (SB) reference value is 21.3-24.8mmol / L. AB is an important indicator of metabolic acid-base imbalance in the body. SB calculated under specific conditions also reflects metabolic factors. The two are normal for acid-base stabilization. Both are low for metabolic acidosis (uncompensated), both are high for metabolic alkalosis (uncompensated), AB> SB is respiratory acidosis, and AB <SB is respiratory alkalosis. p> (7) Residual base (BE): Reference value3- + 3mmol / L, positive value indicates increase, negative value decreases. (8) Anion gap (AG): The reference value is 8-16mmol / L, which is an important indicator for early detection of mixed acid-base poisoning. Judging the acid-base imbalance should first understand the clinical situation, generally based on pH, PaCO2, BE (or AB) to determine the acid-base imbalance, according to PaO2 and PaCO2 to determine hypoxia and ventilation. A pH outside the normal range indicates an imbalance. But pH may still have acid-base imbalance. PaCO2 above normal indicates respiratory acid-base imbalance, and BE above normal indicates metabolic acid imbalance. However, blood gas and acid-base analysis sometimes need to be combined with other tests and combined with clinical dynamic observation to get a correct judgment.

Clinical significance of arterial blood gas analysis

In the past, due to backward medical conditions, the determination of hypoxia can only be estimated by clinical symptoms, and the acid-base imbalance is only judged by symptoms and CO2CP (carbon dioxide binding power). Because clinical symptoms and CO2CP are affected by many factors and their reliability is poor, arterial blood gas analysis is a reliable indicator for determining whether the body has an acid-base balance disorder and the degree of hypoxia and hypoxia. At present, arterial blood gas analysis has become an essential test item in the diagnosis and treatment of hypoxemia and acid-base imbalance in clinical departments. (1) Hypoxemia is a common and life-threatening complication. Many diseases can be caused, such as respiratory diseases, heart diseases, severe trauma, shock, multiple organ dysfunction syndrome (MODS), poisoning. And other critical illnesses, as well as surgical anesthesia. The clinical symptoms and signs alone cannot make accurate judgments and estimates of hypoxemia and its extent. Arterial blood gas analysis is the only reliable indicator for the diagnosis and extent of hypoxemia. Even if a ventilator can correct hypoxia and hypoxemia, many of the indications of a ventilator cannot be reasonably applied without the help of arterial blood gas analysis monitoring. (2) In the treatment of critical illness, acid-base imbalance is the most common clinical complication after hypoxemia, and timely diagnosis and correction of acid-base imbalance is of great significance for the treatment of critical illness. Arterial blood gas analysis is also the only reliable indicator for judging and measuring the acid-base balance of the human body.

Precautions for arterial blood gas analysis

Influencing factors of arterial blood gas analysis: (1) Blood collection location: If the blood collection artery is infused, hemolysis and dilution may occur, increasing K + and decreasing Ca2 +. If it is mistakenly collected as venous blood, because the venous blood cannot accurately reflect the arterial blood gas status, its pH value is close to that of arterial blood under normal circumstances, but when the body is sick, various metabolisms have different degrees of obstacles. There is a clear difference between the pH of arteries and veins. (2) Blood collection and heparin concentration: Heparin concentration is the core guarantee for accurate blood gas analysis results. Excessive use of heparin can cause dilution errors, lower pH, PaO2 values, and higher PaCO2 values, resulting in pseudohypocapnia. However, if the amount of heparin is too small, it will not function as an anticoagulant. The International Biochemical Federation (IFCC) recommends a final concentration of heparin in blood gas samples of 50 u / ml. (3) Air bubbles: Because air bubbles will affect the blood gas pH, PaCO2, PaO2 detection results, especially PaO2 value. Ideal blood gas specimens should have air bubbles below 5%. (4) Degree of specimen mixing: As with other anticoagulated specimens, inadequate mixing will increase the occurrence of coagulation, which will affect the accuracy of hemoglobin and hematocrit results. (5) Storage of specimens: For specimens for lactic acid detection, they must be stored in ice water before testing. Other testing items can be stored at room temperature or in ice water for 1 h. (6) Sample submission time: The detection of PaCO2, PaO2 and lactic acid must be completed within 15 minutes. The remaining items such as pH, electrolyte, BUN, hemoglobin, blood glucose and hematocrit should be completed within 1 h.

Arterial blood gas analysis related diseases

Cardiogenic shock, acute right heart failure, acute left heart failure, liver-lung syndrome, strangulation, end-stage pneumonia in the elderly, emphysema in the elderly, respiratory failure in the elderly, acute respiratory distress syndrome in the elderly, Metabolic alkalosis in the elderly

Arterial blood gas analysis related symptoms

Opening the shoulders and raising the shoulders, the internal heat swells, the fingers (toes) swell, the limbs grow and thicken excessively, the local skin color and temperature of the limbs change, the palm depression disappears or slightly bulges, halo effect, pregnant women get angry, scleredema, nails Frostbite