Correlation and agreement between arterial and central venous blood pH, PO2, PCO2 and HCO3− values of mechanically ventilated patients in intensive care unit: A prospective observational study

The procedure for arterial blood sampling can be technically difficult with limitations and complications. 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. Prospective observational study. 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 Arterial blood was collected from radial artery and within 2 minutes central venous blood was withdrawn from the same patient.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. 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), R2 = 0.128, arterial PCO2 = 0.429 × central venous PCO2 + 24.627 (constant), R2 = 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. The arterial pH, PO2, PCO2 and HCO3− values correlated well with central venous values. However, only the arterial pH value can replace the central venous pH value. la toma de gases arteriales (GA) puede ser difícil con limitaciones y complicaciones. evaluar la correlación y concordancia entre valores de pH, PO2, PCO2 y HCO3− en sangre arterial y venosa central e inferir si valores de gases venosos centrales (GVC) pueden reemplazar valores de GA. Estudio prospectivo observacional. se tomaron 100 muestras en 50 pacientes adultos normotensos y normotérmicos, que requirieron ventilación mecánica. Los GA se tomaron de la arteria radial y 2 minutos después se tomaron los GVC. Se evaluó la correlación y concordancia utilizando la Correlación de Pearson y Análisis de Bland Altman. los valores venosos y arteriales de pH, PO2, PCO2 y HCO3− correlacionaron significativamente (rpH = 0.88, p < 0.001; rPO2=0.358, p < 0.05; rPCO2=0.470, p < 0.001 y rHCO3=0.714, p < 0.001). Las ecuaciones que predicen los valores de GA a partir de valores de GVC, son: pH arterial = 0.879 × pH venoso central + 0.9422; PO2 arterial = 0.421 × PO2 venoso central + 114.4, R2 = 0.128, PCO2 arterial = 0.429 × PCO2 venoso central +24.627, R2 = 0.2205 y HCO3 arterial = 1.045 × HCO3 venoso central + 3.402, R2 = 0.5101. La diferencia media de GA menos GVC de pH, PO2, PCO2, y bicarbonato fue de 0.053 ± 0.014, 56.04 ± 15.74, 2.20 ± 4.4 y 4.30 ± 1.64, respectivamente. Las gráficas de Bland-Altman para concordancia del pH, PO2, PCO2 y bicarbonato mostraron límites de concordancia del 95% de -0.04 a 0.146, −52.51 a 164.59, −26.61 a 31.01 y −7.0 a 15.6, respectivamente. hubo correlación entre los valores de GA y GVC de pH, PO2, PCO2 y HCO3−. Sin embargo, solamente el pH venoso puede reemplazar el pH arterial.