The bicarbonate test is performed to measure the level of bicarbonate in a person's blood. Bicarbonate is a chemical substance that does not allow the pH of the blood to become too acidic. Whenever the pH level of the blood drops, the kidneys absorb bicarbonate, prevent it from passing out through urine, and return it to the blood. The bicarbonate test can be performed on a blood sample that is usually taken from a vein. The levels of other electrolytes such as potassium, sodium, and chloride may also be estimated simultaneously.
Mostly, the level of bicarbonate is estimated as a part of the carbon dioxide test or arterial blood gas test. In the process of breaking down food into energy, inhaled oxygen is used up by the body. In this process, the carbon dioxide formed as a byproduct is then carried away by red blood cells and some part of it gets dissolved in blood. This carbon dioxide that gets dissolved in the blood is converted to bicarbonate. It flows to the lungs, where again some amount of it is converted into carbon dioxide and exhaled. In case there is excess bicarbonate in the blood, it is thrown out of the body through urine by the kidneys.
The bicarbonate test is helpful in detecting a number of conditions that affect the blood bicarbonate levels such as lung disease, kidney disorders, and metabolic conditions.No special preparations are required before the test. Local anesthesia is given in order to reduce pain while taking out blood from the artery. If you suffer from any bleeding disorder or are on blood thinning medications, tell the doctor about this well in advance.
The blood sample is collected from an artery in the wrist, groin, or the inner side of your arm, just above the elbow crease. In case your hand is used for dialysis, or there is an infection or inflammation in the area of the puncture site, the arterial blood gas test is not performed. You should breathe normally when your blood is being collected. Once the blood sample is obtained, a bandage is applied over the punctured site and pressure is applied for at least ten minutes. The normal values for the bicarbonate test can vary from lab to lab, depending upon the equipment used and their calibration. Normally, the bicarbonate value ranges between 22 and 29 mEq/L.
Higher values are found in the blood of patients suffering from persistent vomiting and dehydration, or in those who have just undergone a blood transfusion. The excessive use of antacids can also increase the bicarbonate level. It can also be indicative of conditions like chronic obstructive pulmonary disease, heart disease, Cushing's disease, and Conn's syndrome. Low bicarbonate values are observed due to rapid breathing and an overdose of alcohol or aspirin. Severe malnutrition, burns, shock, liver or kidney diseases, hyperthyroidism, uncontrolled diabetes, or a massive heart attack can also lower the bicarbonate value.
Blood collection from an artery is more painful than that from a vein. There are a few risks involved in the process of drawing blood out from an artery such as the development of a swelling or bruise at the punctured site. In rare cases, the needle may damage a nerve that is lying close to the artery. Even when the blood is taken from a vein, similar risks do exist. Rarely, if proper aseptic precautions are not taken before inserting the needle, an infection may develop in the area of puncture.
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