Mastering quick interpretation of acid base lab values is a key element to success of the Nurse. Three components are included in typical lab value assessment. pH, pCO2, HCO3 (Bicarbonate)
The first step to interpret this is to look at pH. Blood pH is normally 7.35-7.45. pH is determined by the amount of hydrogen ions contained in the blood.
A pH of less than 7.35 is termed acidosis. Acidosis indicates a buildup of carbonic acid in the blood.
A pH higher than 7.45 is termed alkalosis. Alkalosis indicates a buildup of bicarbonate (bases) and/or a general decrease in carbonic acid in the blood.
The second step is to examine the partial pressure of carbon dioxide in the blood, pCO2. pCO2 is normally 35-45 mmHg. pCO2 is regulated primarily through respiration.
Opposite Respiratory and pH directions indicates a respiratory disorder. If the pCO2 is not in the opposite direction of the pH then check the HCO3 next.
Respiratory acidosis is often indicated by a pH of less than 7.35 and a pCO2 of higher than 45 mmHg.
Respiratory Alkalosis is indicated by a pH of more than 7.45 and a pCO2 of less than 35 mmHg.
The normal value of bicarbonate is 22-26 mmol/L. The amount of the base HCO3 and bicarbonate in the blood is regulated in the kidneys.
If the HCO3 (bicarbonate) is going in the same direction as pH then the problem is most likely a metabolic problem.
The patient with Metabolic acidosis can grossly be determined as Down, Down, Down (Decreased pH, Decreased pCO2, Decreased HCO3)
Metabolic alkalosis can grossly be determined as UP, UP, UP (Increased pH, Increased pCO2, Increased HCO3)
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