Venous-to-arterial carbon dioxide difference to arteriovenous oxygen content difference ratio combined with lactate to predict prognosis of patients with septic shock

Abstract

To investigate the prognostic significance of venous-to-arterial carbon dioxide difference to arteriovenous oxygen content difference ratio (Pv-aCO2/Ca-vO2 ratio) combined with lactate in patients with septic shock during the early phases of resuscitation. A retrospective study was conducted for 104 septic shock patients. All patients received an initial fluid resuscitation according to the Surviving Sepsis Campaign: International Guidelines for Management of Severe Sepsis and Septic Shock, 2012(SSC2012). Patients were classified into four groups according to lactate levels and Pv-aCO2/Ca-vO2 ratio at 6 h of resuscitation: group A, lactate≥2.0 mmol/L and Pv-aCO2/Ca-vO2>1.0; group B, lactate≥2.0 mmol/L and Pv-aCO2/Ca-vO2≤1.0; group C, lactate<2.0 mmol/L and Pv-aCO2/Ca-vO2>1.0; group D, lactate<2.0 mmol/L and Pv-aCO2/Ca-vO2≤1.0. The hemodynamic parameters and oxygen metabolism parameters were recorded at baseline and 6 h after fluid resuscitation. Sequential organ failure assessment (SOFA) score at day 1, day 3 were calculated. The 28-day mortality rate was recorded. (1) Group A had the highest SOFA score at day 3 and group D the lowest, which were respectively 10.8±3.3, 6.7±3.6, 5.6±3.1, 4.1±2.2 in four groups. Accordingly, the 28-day mortality rate of group A was the highest and group D the lowest, which were respectively 83.3%, 59.1%, 60.0%, 14.3% in four groups. The differences were statistically significant (P<0.05). (2) The Cox regression analysis of 28 d mortality revealed that lactate levels (RR=4.306, 95%CI 1.979-9.369) and Pv-aCO2/Ca-vO2 ratio (RR=2.888, 95%CI 1.676-4.976) at T6 were independent predictors to 28-day mortality. (3) The AUCROC of Pv-aCO2/Ca-vO2 ratio combined with lactate [0.910(95%CI 0.857-0.963)] was significantly greater than the AUCROC of wither lactate [0.762(95%CI 0.673-0.852), Z=2.775; P=0.006) or Pv-aCO2/Ca-vO2 ratio [0.781(95%CI 0.693-0.868), Z=2.458; P=0.014) alone. Combination of Pv-aCO2/Ca-vO2 ratio and lactate level at early stage of resuscitation in patients with septic shock is better than single parameter to predict the prognosis.