A Comparative Study of Arterial and Venous Blood Gas Analysis in Critically Ill Patients

Abstract

Background: Measurement of blood gases is increasingly becoming an essential part of diagnosis, management and monitoring of critically ill patients. In our study we used PVBG and four variables po2, pc02, hco3 and ph of PVBG was compared with ABG and their agreement and correlation assessed.
Objective: To study the relationship between ABG and VBG in critically ill patients and to assess the usefulness of VBG as a surrogate for ABG in the initial management of critically ill patients.
Methodology: 100 random patients who were considered critically ill based on SOFA score value >/ = 7 admitted in GRMC, Gwalior were taken. P value <0.05 was taken as significant. IBM SPSS was used for analysis.
Results: The pHA and pHV shows good correlation and agreement (mean difference is 0.04 (p<o.000) Correlation coefficient is 0.832.(p<0.000 ) 95% limits of agreement are -0.2 to .16 mm Hg). pCO2 A and pCO2V shows good correlation and agreement (mean difference is about 5.7 mmHg (P<0.000),Pearsons correlation coefficient is 0.916.(p <0.000) , 95% limits of agreement is -16 to 4mm Hg). HCO3A and HCO3V shows good agreement and correlation(mean difference between hco3A and hco3V is 1.22( p<0.001), Pearsons correlation coefficient is 0.960 (p<0.000) ,95% limits of agreement is from 6 to -8 mmHg).pO2A and pO2V shows poor correlation and agreement (mean difference is 55.191 (p <0.000),Pearsons correlation coefficient is 0.166 (p< 0.099 ),95% limit of agreement is 4 to 120 mmHg).
Conclusion: In our study we found that there is excellent agreement between pH, pCO2 and HCO3 between ABG and VBG in critically ill patients.. The agreement between arterial and venous pO2 is very poor and venous pO2 cannot be reliably used instead of arterial value.