Resumo

ISLAM, Mohd Sabihul et al. Correlation and agreement between arterial and central venous blood pH,PO2, PCO2 and HCO3− values of mechanically ventilated patients in intensive care unit. Rev. colomb. anestesiol. [online]. 2013, vol.41, n.3, pp.190-195. ISSN 0120-3347.  https://doi.org/10.1016/j.rca.2013.05.011.

Background: The procedure for arterial blood sampling can be technically difficult with various limitations and complications. Central venous catheterization is a mandatory procedure in ICU. The sampling of central venous blood is much easier, quicker and less complicated. Context: Correlation and agreement between arterial and central venous blood pH, PO₂, PCO₂ and HCO₃ − values of mechanically ventilated patients. Aims: Aim was 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 values could replace arterial blood gas values. Settings and design: Intensive Care Unit and prospective observational study. Materials and methods: A total of 100 samples (50 arterial blood gas and 50 central venous blood gas) were collected from 50 adult patients with varied disease process admitted in a medical college ICU. Patients requiring mechanical ventilation having palpable radial artery, normotensive and normothermic were enrolled for the study. No patient was repeated for the study. Arterial blood was collected from radial artery and within 2 minutes central venous blood was withdrawn from the same patient. Correlation and agreement were evaluated between arterial and central venous pH, PO₂, PCO₂ and HCO₃ −. Statistical analysis used: Pearson's correlation and Bland-Altman analysis. Results: The pH, PO₂, PCO₂ and HCO₃ − of CVBG correlated significantly with arterial values (r_pH = 0.88, P < 0.001; r_PO2 = 0.358, P < 0.05; r_PCO2 = 0.470, P < 0.001 and r_HCO3 = 0.714, P < 0.001). Regression equations were derived to predict arterial blood values from venous blood 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 PO₂ + 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 bicarbonatewas 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. Conclusions: The arterial pH, PO₂, PCO₂ and HCO₃ – values correlatedwell with central venous values. However, only the arterial pH value can replace the central venous pH value.

Palavras-chave : Arterial blood gas; Central venous blood gas; Correlation; Agreement.

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