Early Central Venous-to-Paco 2 Difference and Subsequent Lactate Clearance in Shock: Prospective Pediatric Cohort, 2021–2022

OBJECTIVES: To evaluate early central venous-to-Pa co2 difference (∆P co2 ) and its correlation with later lactate concentration in pediatric patients with shock. DESIGN: Prospective observational study. SETTING: Two medical-surgical PICUs in a tertiary-care university hospital. PATIENTS: Children younger than 18 years old with septic or cardiogenic shock admitted to the PICUs (March 2021 to December 2022). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Demographic, clinical, and outcome data were collected from medical records. Arterial and central venous blood samples were collected simultaneously at PICU admission and 6, 24, and 48 hours after admission to determine ∆P co2 , arterial lactate concentration, lactate clearance, and central venous oxygen-hemoglobin saturation (Scv o2 ). Left ventricle ejection fraction (LVEF) was estimated by echocardiography. Fifty-four patients 1.1 to 203.1 months old (median, 25.2 mo old) were included: (43/54 [79.6%] had septic shock and 11/54 [20.4%] had cardiogenic shock). Patients were divided into two groups according to ∆P co2 at 6 hours (24 ≤ 6 mm Hg and 30 > 6 mm Hg). The group with ∆P co2 greater than 6 mm Hg, compared with the group less than or equal to 6 mm Hg, had a higher Vasoactive-Inotropic Score and Pediatric Logistic Organ Dysfunction score, and there was a higher proportion of patients with low LVEF, elevated lactate concentrations, reduced lactate clearance, and Scv o2 less than 70%. ∆P co2 positively correlated with lactate concentrations and negatively correlated with lactate clearance and Scv o2 . The ∆P co2 cutoff of 7.5 mm Hg at 6 hours had sensitivity of 0.70, specificity of 0.76, positive predictive value of 0.87, and negative predictive value of 0.54 for predicting lactate clearance less than 10% at 24 hours (area under the receiver operating characteristic curve, 0.81 [95% CI, 0.69-0.91]). There were no differences in clinical outcomes between the groups. CONCLUSIONS: In pediatric shock, ∆P co2 measured 6 hours after presentation is correlated with subsequent lactate clearance at 24 hours and may serve as an early resuscitation and severity stratification metric.