Prognostic Value of Venous to Arterial Carbon Dioxide Difference during Early Resuscitation in Critically Ill Patients with Septic Shock

CONTEXT The partial pressure of venous to arterial carbon dioxide gradient (PCO2 gap) is considered as an alternative marker of tissue hypoperfusion and has been used to guide treatment for shock. AIMS The aim of this study was to investigate the prognostic value of venous-to-arterial carbon dioxide difference during early resuscitation of patients with septic shock and compared it with that of lactate clearance and Acute Physiology and Chronic Health Evaluation II (APACHE-II) score. SETTINGS AND DESIGN Forty patients admitted to one Intensive Care Unit were enrolled. SUBJECTS AND METHODS APACHE-II score was calculated on admission. An arterial blood gas, central venous, and lactate samples were obtained on admission and after 6 h, and lactate clearance was calculated. Patients were classified retrospectively into Group I (survivors) and Group II (nonsurvivors). Pv-aCO2 difference in the two groups was evaluated. STATISTICAL ANALYSIS USED Data were fed to the computer and analyzed using IBM SPSS software package version 20.0. RESULTS At T0, Group II showed high PCO2 gap (8.37 ± 1.36 mmHg) than Group I (7.55 ± 0.95 mmHg) with statistically significant difference (P = 0.030). While at T6, Group II showed higher PCO2 gap (9.48 ± 1.47 mmHg) with statistically significant difference (P < 0.001) and higher mean lactate values (62.71 ± 23.66 mg/dl) with statistically significant difference (P < 0.001) than Group I where PCO2 gap and mean lactate values became much lower, 5.91 ± 1.12 mmHg and 33.61 ± 5.80 mg mg/dl, respectively. Group I showed higher lactate clearance (25.42 ± 6.79%) with statistically significant difference (P < 0.001) than Group II (-69.40-15.46%). CONCLUSIONS High PCO2 gap >7.8 mmHg after 6 h from resuscitation of septic shock patients is associated with high mortality.