Blood gas analysis (AGD) or arterial blood gas (ABG) tests are blood tests taken through arteries to measure the levels of oxygen, carbon dioxide, and the level of acid base (pH) in the blood.
Blood gas analysis is generally done to check the function of the pulmonary organs into which red blood cells carry oxygen and carbon dioxide from and throughout the body.
In addition, this test can be done to check the condition of the heart and kidney organs, as well as symptoms caused by disturbances in the distribution of oxygen and carbon dioxide, or pH balance in the blood, such as nausea, shortness of breath, and decreased consciousness. This test is also done on patients who are using breathing aids to monitor their effectiveness.
Indications and Contraindications for Blood Gas Analysis
Blood gas analysis is carried out to measure levels of acid base (pH) to find out if the blood is too acidic (acidosis) or alkaline (alkalosis), and to find out whether the oxygen pressure in the blood is too low (hypoxia), or carbon dioxide is too high (hypercarbia). These conditions can be related to the body's metabolic system or respiratory system. Some conditions that can cause these changes include:
- Asthma.
- Cystic fibrosis.
- Chronic obstructive pulmonary disease.
- Pneumonia.
- Heart disease.
- Kidney illness.
- Metabolic Disorders.
- Head or neck trauma that affects breathing.
- Severe infection or sepsis.
- Sleep disturbance.
- Diabetic ketoacidosis.
- Chemical poisoning or drug overdose.
- Patients using respiratory aids.
Blood Gas Analysis Warning
There are several conditions that can affect the results of the examination. One is blood vessel disorders, such as peripheral arterial disease or the formation of abnormal ducts (fistulas) in arteries, both arising from disease or deliberately made for dialysis access (cimino). In these circumstances, it is better for arterial blood samples to be taken from other places. In addition, if there are local disorders at the site of blood collection, such as infections, burns, or scars, it is also expected to be careful before taking blood samples for blood gas analysis.
Patients with blood clotting disorders, either due to disease or because of the administration of drugs, such as anticoagulants, the risk of causing hematoma after the action of taking blood. There are also conditions that make it difficult for nurses or doctors to take blood samples from arteries, for example if the patient is less cooperative, has a weak pulse, or tremors.
Before Blood Gas Analysis
There is no special preparation that the patient needs to do before undergoing blood gas analysis. The doctor or nurse will do an Allen test or check the smooth flow of blood vessels by pressing the blood vessels in the wrist for a few seconds.
If the patient is being given additional oxygen, the doctor will release the oxygen tube approximately 20 minutes before conducting a blood gas analysis test. However, this can be done if the patient is not completely dependent on the additional oxygen.
For certain conditions, the doctor will give a local anesthetic to relieve the pain that can occur when a needle is inserted into an artery.
Blood Gas Analysis Procedure
As an initial step in blood gas analysis, the doctor will sterilize blood sampling points, such as wrists, elbows, or thighs, with antiseptic fluid.
After finding the arteries, which are throbbing blood vessels, the doctor will insert a syringe through the skin into the vein. The amount of blood drawn is usually 1 mL.
After the blood sample has been taken, the syringe will be removed slowly and the area will be covered with bandages. To reduce the potential for swelling, press the area for a few minutes after the needle is removed. Blood samples will be immediately taken to the laboratory to go through the analysis process.
After Blood Gas Analysis
The patient will feel pain and discomfort when taking blood for several minutes afterwards, because the arteries are quite sensitive. Patients are advised not to leave the room immediately to monitor what might happen, such as dizziness, nausea, or fainting shortly after blood is drawn.
Usually, patients can receive test results about 15 minutes after taking blood. If further analysis is needed, the results will be given to the referring doctor.
Blood Gas Analysis Results
Blood gas analysis results generally include measurements of several things, including:
- Acid base (pH) of blood, namely by measuring the amount of hydrogen ions in the blood. If the pH of the blood below normal is said to be more acidic, while if the pH is above normal then the blood is said to be more alkaline.
- Oxygen saturation, which is a measure of the amount of oxygen carried by hemoglobin in red blood cells.
- Oxygen partial pressure, which is a measurement of the pressure of oxygen dissolved in the blood. This measurement can determine how well oxygen can flow from the lungs into the blood.
- Partial pressure of carbon dioxide, which is a measurement of the pressure of carbon dioxide dissolved in the blood. This measurement determines how well carbon dioxide can be released from the body.
- Bicarbonate, a balancing chemical that helps prevent blood pH from becoming too acidic or too alkaline.
