Low cardiac index and stroke volume on admission are associated with poor outcome in critically ill burn patients: a retrospective cohort study.

BACKGROUND: Impact of early systemic hemodynamic alterations and fluid resuscitation on outcome in the modern burn care remains controversial. We investigate the association between acute-phase systemic hemodynamics, timing of fluid resuscitation and outcome in critically ill burn patients. METHODS: Retrospective, single-center cohort study was conducted in a university hospital. Forty critically ill burn patients with total body surface area (TBSA) burn-injured >20 % with invasive blood pressure and cardiac output monitoring (transpulmonary thermodilution technique) within 8 h from trauma were included. We retrospectively examined hemodynamic variables during the first 24 h following admission, and their association with 90-day mortality. RESULTS: The median (interquartile range 25th-75th percentile) TBSA, Simplified Acute Physiology Score II (SAPS II) and Abbreviated Burn Severity Index of the study population were 41 (29-56), 31 (23-50) and 9 (7-11) %, respectively. 90-Day mortality was 42 %. There was no statistical difference between the median pre-hospital and 24-h administered fluid volume in survivors and non-survivors. On admission, stroke volume (SV), cardiac index (CI), oxygen delivery index and mean arterial pressure (MAP) were significantly lower in patients who died despite similar fluid resuscitation volume. ROC curves comparing the ability of initial SV, CI, MAP and lactate to discriminate 90-day mortality gave areas under curves of, respectively, 0.89 (CI 0.77-1), 0.77 (CI 0.58-0.95), 0.73 (CI 0.53-0.93) and 0.78 (CI 0.63-0.92); (p value <0.05 for all). In multivariate analysis, SAPS II and initial SV were independently associated with 90-day mortality (best cutoff value for SV was 27 mL, sensitivity 92 %, specificity 69 %). During 24 h, no interaction was found between time and outcome regarding macrocirculatory parameters changes. Hemodynamic parameters improved during the first 24-h resuscitation in all patients but patients who died had lower SV and CI on admission, which remained through the first 24 h. CONCLUSION: Low initial SV and CI were associated with poor outcome in critically ill burn patients. Very early hemodynamic monitoring may in help detecting under-resuscitated patients. Future prospective interventional studies should explore the impact of early goal-directed therapy in these specific patients.