Relationship between injury severity and lactate levels in severely injured patients

Objective: To determine the correlation of blood concentration of lactate and severity of injury and survival in severely injured patients. Design and setting: A prospective study of severely injured patients admitted directly from an emergency surgical, unit to a surgical intensive care unit with an Injury Severity Score (ISS) of 16 points or more. The study was conducted over 30 months. Patients: 98 severely injured subjects aged between 16 and 82 years with ISS range from 16 to 75 points, overall 25.5% mortality. Interventions: Blood lactate concentrations were measured once on admission, twice daily during the first 2 days and once daily during the next 3 days. ISS, Revised Trauma Score, Shock Index, and Trauma and Injury Severity Score were calculated for each subject. Measurements and results: Of 98 severely injured patients 91 had elevated blood lactate concentration (over 2.0 mmol/l). Regression analyses demonstrated that injury severity, as measured by ISS, can be predicted from lactate concentration on admission, while survival, either actual or predicted by Trauma and Injury Severity Score higher than 0.5, can be predicted from lactate concentration after 12 h. We also found that patients with Shock Index higher than 0.9 had significantly higher lactate levels during the first 36 h than those with values less than 0.9. Conclusions: This study confirmed the relationship between blood lactate levels and injury severity as well as the prognostic value of blood lactate level for survival of severely injured patients.