Association of serial lactate measurements with mortality in children with septic shock: a prospective cohort study

Background Septic shock remains a leading cause of mortality among children admitted to pediatric intensive care units (PICU), particularly in developing countries. Early recognition and continuous monitoring of tissue perfusion are essential to improving outcomes. This prospective study aimed to evaluate whether sequential assessments of blood lactate, central venous oxygen saturation (ScvO₂), and the venous-to-arterial carbon dioxide difference (ΔPCO₂) were associated with mortality among children with septic shock. Methods A prospective observational study was conducted from October 2020 to September 2021 in the tertiary PICU of the Vietnam National Children’s Hospital, Vietnam. Children aged 1 month to 16 years who met the Surviving Sepsis Campaign 2020 criteria for septic shock were enrolled. Blood lactate, ScvO₂, and ΔPCO₂ were measured at PICU admission (0h) and at 6, 24, and 48 hours after admission. The primary outcome was 28-day mortality. Data were collected and analyzed using Stata MP 17.0 (Stata Corp LLC, College Station, TX, USA). Results The 28-day mortality rate was 21%. Baseline lactate was the strongest independent predictor of mortality (adjusted OR 1.24 per 1 mmol/L increase; p = 0.055). Serial lactate levels remained consistently higher in non-survivors across all time points (p < 0.05), whereas ScvO₂ and ΔPCO₂ showed no significant between-group differences. Lactate decreased significantly over time in survivors but not in non-survivors (p < 0.001). The multivariable model demonstrated moderate discrimination with an AUC of 0.74 (95% CI 0.59–0.88). Conclusions In this paediatric septic shock cohort, sequential assessment of lactate over the first 48 hours provided better mortality risk stratification than ScvO₂ and ΔPCO₂. Serial lactate monitoring represents a simple, low cost tool that can be integrated into septic shock resuscitation protocols.