Correlation of Venous Blood Gas and Pulse Oximetry With Arterial Blood Gas in the Undifferentiated Critically Ill Patient.

RATIONALE

Blood gas analysis is often used to assess acid-base, ventilation, and oxygenation status in critically ill patients. Although arterial blood gas (ABG) analysis remains the gold standard, venous blood gas (VBG) analysis has been shown to correlate with ABG analysis and has been proposed as a safer less invasive alternative to ABG analysis.

OBJECTIVE

The purpose of this study was to evaluate the correlation of VBG analysis plus pulse oximetry (SpO) with ABG analysis.

METHODS

We performed a prospective cohort study of patients in the emergency department (ED) and intensive care unit (ICU) at a single academic tertiary referral center. Patients were eligible for enrollment if the treating physician ordered an ABG. Statistical analysis of VBG, SpO, and ABG data was done using paired t test, Pearson χ, and Pearson correlation.

MAIN RESULTS

There were 156 patients enrolled, and 129 patients completed the study. Of the patients completing the study, 53 (41.1%) were in the ED, 41 (31.8%) were in the medical ICU, and 35 (27.1%) were in the surgical ICU. The mean difference for pH between VBG and ABG was 0.03 (95% confidence interval: 0.03-0.04) with a Pearson correlation of 0.94. The mean difference for pCO between VBG and ABG was 4.8 mm Hg (95% confidence interval: 3.7-6.0 mm Hg) with a Pearson correlation of 0.93. The SpO correlated well with PaO (the partial pressure of oxygen in arterial blood) as predicted by the standard oxygen-hemoglobin dissociation curve.

CONCLUSION

In this population of undifferentiated critically ill patients, pH and pCO on VBG analysis correlated with pH and pCO on ABG analysis. The SpO correlated well with pO on ABG analysis. The combination of VBG analysis plus SpO provided accurate information on acid-base, ventilation, and oxygenation status for undifferentiated critically ill patients in the ED and ICU.