Detection of preanalytical errors in arterial blood gas analysis

INTRODUCTION: Blood gas analysis (BGA) is an essential test used for years to provide vital information in critically ill patients. However, the instability of the blood gases is a problem. We aimed to evaluate time and temperature effects on blood gas stability. MATERIALS AND METHODS: Arterial blood was collected from 20 patients into syringes. Following BGA for baseline, syringes were divided into groups to stand at 4°C and 22°C for 30, 60, 90, 120 minutes. All were tested for pH, partial pressure of carbon dioxide (pCO(2)), partial pressure of oxygen (pO(2)), oxygen saturation (sO(2)), oxyhemoglobin (O(2)Hb), sodium, potassium, glucose, lactate, oxygen tension at 50% hemoglobin saturation (p50), and bicarbonate. A subgroup analysis was performed to detect the effect of air on results during storage. Percentage deviations were calculated and compared against the preset quality specifications for allowable total error. RESULTS: At 4°C, pO(2) was the least stable parameter. At 22°C, pO(2) remained stable for 120 min, pH and glucose for 90 min, lactate and pCO(2) for 60 min. Glucose and lactate were stable when chilled. Air bubbles interfered pO(2) regardless of temperatures, whereas pCO(2) increased significantly at 22°C after 30 min, and pH decreased after 90 min. Bicarbonate, sO(2), O(2)Hb, sodium, and potassium were the unaffected parameters. CONCLUSIONS: Correct BGA results are essential, and arterial sample is precious. Therefore, if immediate analysis cannot be performed, up to one hour, syringes stored at room temperature will give reliable results when care is taken to minimize air within the blood gas specimen.