Agreement between arterial and venous blood gas measurements in patients with sepsis and septic shock

Background and Objective: Acid–base status is mandatory for clinical assessment of patients with septic shock and severe sepsis. Generally, venous blood gas sample collection is easier, however, the data regarding this approach are lesser defined in our population as a substitute for arterial blood gas (ABG) sample. The present study aimed to determine and compare the pH, pCO2, and bicarbonate levels in VBG and ABG samples in patients with sepsis and septic shock. Method: A cross sectional comparative study was conducted on 350 patients with sepsis and/or septic shock admitted to the medical emergency of Jinnah Hospital, Lahore, Pakistan. Both ABG and VBG samples were collected and pH, pCO2, and bicarbonate levels were determined by standard methods. Data were analyzed using Pearson correlation and the Bland–Altman method for bias. Results: An interclass correlation (r = 0.995, r = 0.929 and r = 0.946) was found for pH, pCO2, and bicarbonate between ABG and VBG samples, respectively. The Bland–Altman method showed a high degree of agreement for two sets of measurements; pH (bias ± SD, 0.089 ± 0.00472) and pCO2 (bias ± SD, -1.1096 ± 1.0089) with a clinically acceptable difference whereas the difference in bicarbonate measurement was found slightly higher (bias ± SD, 1.124 ± 0.674) revealing, however, a good degree of agreement with clinically acceptable bias. Conclusion: Use of a venous blood sample in patients with sepsis or septic shock is a clinically acceptable substituent for ABG measurement in evaluating acid-base status of these patients for further management.