Central Venous Blood Gas Analysis: An Alternative to Arterial Blood Gas Analysis for pH, PCO(2), Bicarbonate, Sodium, Potassium and Chloride in the Intensive Care Unit Patients

AIMS: Arterial blood gas (ABG) analysis is a frequently ordered test in intensive care unit (ICU) and can analyze electrolyte in addition to pH and blood gases. Venous blood gas (VBG) analysis is a safer procedure and may be an alternative for ABG. Electrolyte estimation by auto analyzer usually takes 20–30 minutes. This study was aimed to investigate the correlation of pH, PCO(2), bicarbonate, sodium, potassium, and chloride (electrolytes) between ABG and central VBG in ICU patients. MATERIALS AND METHODS: This was a prospective observational study conducted in medical college hospital ICU. Adult patients requiring ABG and electrolyte estimation as a part of their clinical care were consecutively included in the study. Patients having any intravenous infusion or who were pregnant were excluded. Venous samples were taken within 2 minutes of arterial sampling from in situ central line. Data were analyzed using Bland-Altman methods. RESULTS: A total of 110 patients' paired blood samples were analyzed. The mean difference between arterial and central venous values of pH, PCO(2), bicarbonate, sodium, potassium, and chloride was 0.04 units, –5.84 mm Hg, 0.89 mmol/L, –1.8 mEq/L, –0.04 mEq/L, and –0.89 mEq/L, respectively. The correlation coefficients for pH, PCO(2), HCO(3)(−), sodium, potassium, and chloride were 0.799, 0.831, 0.892, 0.652, 0.599 and 0.730, respectively. Limits of agreement (95%) were within acceptable limits. CONCLUSION: Central venous pH, PCO(2), and bicarbonate may be an acceptable substitute for ABG in patients admitted in the ICU. However caution should be exercised while applying electrolyte measurements. HOW TO CITE THIS ARTICLE: Bijapur MB, Kudligi NA, Asma S. Central Venous Blood Gas Analysis: An Alternative to Arterial Blood Gas Analysis for pH, PCO(2), Bicarbonate, Sodium, Potassium and Chloride in the Intensive Care Unit Patients. Indian J Crit Care Med 2019;23(6):258–262.