Abstract
INTRODUCTION: Traumatic haemorrhage is a major cause of preventable death, and blood transfusion is a crucial component of damage control resuscitation. Several diagnostic strategies exist to anticipate hypovolaemic shock and subsequent blood transfusion requirements, but their pre-hospital utility is inconsistent. Capnography or end-tidal carbon dioxide (EtCO2) measurement has received growing recognition for prognostic capability in metabolic, respiratory and cardiac disease. This systematic review examines EtCO2 efficacy in predicting hypovolaemic shock and subsequent blood transfusion in pre-hospital adult trauma patients.The aims and objectives of this study were, first, to determine if early EtCO2 measurement in pre-hospital adult trauma patients can reliably predict hypovolaemic shock and/or blood transfusion when compared to existing strategies and scoring tools and, second, to identify if an EtCO2 predictive threshold can facilitate this.
METHODS: A systematic review following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines was conducted. Seven electronic databases were searched using relevant indexed terms and keywords. Inclusion criteria were adult (>13 years) trauma patients with suspected or confirmed haemorrhage and with early (pre-diagnostic) EtCO2 data from mainstream or side-stream devices, as related in peer-reviewed publications. All articles (n = 1932) were double-blind screened at abstract and title, then at full-text stage by two reviewers. Issues were discussed by the authors. Critical Appraisal Skills Programme (CASP) tools were used. Findings were narratively synthesised.
RESULTS: Thirteen articles were included. Significant heterogeneity, quality limitations and inconsistent reporting hindered direct comparison of results. Nevertheless, 10 comparator strategies/tools were identified and most studies demonstrated EtCO2's efficacy in predicting hypovolaemic shock / blood transfusion, with thresholds below 35 mmHg consistently suggested as predictive.
CONCLUSION: A universal definition for major blood transfusion is still lacking. Further research is needed to identify accurate markers of haemorrhage, including EtCO2 as a potential predictor. A high index of suspicion for haemorrhage and need for blood transfusion is recommended for adult trauma patients with EtCO2 levels below 35 mmHg (4.7 kPa).