The measurement of pH of the blood is the measurement of the concentration of free hydrogen ions (Η+) in the blood. Intracellular metabolism results in the continuous production of hydrogen ions, which are regulated either as an acid (HCO3-) or as a base (H2CO3). The organism requires a constant pH. The kidneys and lungs regulate the pH by maintaining the ratio of acids to bases. Any change in the ratio between bicarbonate and carbonic acid will cause a reciprocal change in the release or uptake of free Η+, thus altering the pH value. Significant pH deviations can be life-threatening. Both bicarbonate (HCO3-) and carbonic acid (H2CO3) are components of the body's acid-base balance system that affect pH.
Venous blood pH can be measured in whole blood and serum or plasma. The measurement is done with a special calibrated instrument (pH meter) and at a specific temperature (25οC).
- Venous Blood pH (Whole Blood) at 25οC: 7.32 - 7.43
- Venous Blood pH (Serum / Plasma) at 25οC: 7.35 - 7.45
Possible Interpretations of Pathological Values
- Increase: Alkali ingestion, Cushing's disease, diarrhea, fever, high altitude, hyperventilation, hysteria, intestinal obstruction (pylorus, duodenum), metabolic alkalosis, treatment of peptic ulcer, renal disease, respiratory alkalosis, salicylate poisoning, vomiting (excessive). Drugs: sodium bicarbonate.
- Decrease: Addison's disease, asthma, heart disease, diabetic ketoacidosis, diarrhea, emphysema, arrhythmia, liver disease, hypercapnia, hypoventilation, malignant hyperthermia, metabolic acidosis, myocardial infarction, nephritis, nephrosis, renal disease, pneumonia, pulmonary edema, pulmonary embolism, pulmonary infection, lung malignancy, respiratory acidosis, respiratory failure, sepsis, shock.
Important note: The specific reference values refer exclusively to the tests performed at Diagnostiki Athinon, based on the pre-analytical procedure (patient preparation, method of sampling, sample preparation, etc.) and the analytical phase of the specific examination (method, reagents, equipment, etc.). It is not possible to make direct comparisons between results produced by different laboratories. Each laboratory (should) has its own reference values.