Revista Colombiana de Anestesiología

a b s t r a c t Background: The procedure for arterial blood sampling can be technically difficult with limitations and complications. Aims: To evaluate the correlation and agreement between arterial and central venous blood pH, PO2, PCO2 and HCO3 − values and infer whether central venous blood gas (CVBG) values could replace arterial blood gas (ABG) values. Design: Prospective observational study. Methods and Material: A total of 100 samples were collected from 50 adult normotensive and normothermic patients requiring mechanical ventilation. Arterial blood was collected from radial artery and within 2 minutes central venous blood was withdrawn from the same patient. Correlation and agreement was tested using Pearson’s Correlation and Bland Altman Analysis. Results: The pH, PO2, PCO2 and HCO3 − of CVBG correlated significantly with arterial values (rpH = 0.88, p < 0.001; rPO2 = 0.358, p < 0.05; rPCO2 = 0.470, p < 0.001 and rHCO3 = 0.714, p < 0.001). Regression equations were derived to predict AVG values from CVBG values as follows: Arterial pH = 0.879 × central venous pH + 0.9422 (constant), arterial PO2 = 0.421 × central venous PO2 + 114.4 (constant), R 2 = 0.128, arterial PCO2 = 0.429 × central venous PCO2 + 24.627 (constant), R 2 = 0.2205 and arterial HCO3 = 1.045 × central venous HCO3 + 3.402 (constant), R2 = 0.5101.The mean arterial minus venous difference for pH, PO2, PCO2, and bicarbonate was 0.053 ± 0.014, 56.04 ± 15.74, 2.20 ± 4.4 and 4.30 ± 1.64 respectively. Bland-Altman plots for agreement of pH, PO2, PCO2, and bicarbonate showed 95% limits of agreement of −0.04 to 0.146, −52.51 to 164.59, −26.61 to 31.01 and −7.0 to 15.6, respectively.