PurposeSevere haemorrhage is a leading cause of early mortality following major trauma. By early identification of patients at risk, blood transfusion could already be initiated in the prehospital period. Aim of the study was to evaluate the extent to which prehospital lactate and base excess, which are known to be associated with trauma-induced coagulopathy, and additional clinical parameters are associated with the need for early transfusion.MethodsIn this prospective, single-centre observational study, trauma patients treated by a helicopter emergency medical service were included, regardless of the injury severity. Patients with coagulation-influencing drugs in long-term therapy were excluded. Blood samples obtained at the beginning of the prehospital treatment were analysed. Primary outcome was the association of lactate and base excess with the need for early transfusion (resuscitation room or immediate surgery). Receiver operating characteristic curves were created, and the area under the curve (AUROC) was calculated.ResultsBetween 2015 and 2018, 21 out of 130 adult trauma patients received blood products during the early in-hospital treatment. Both prehospital lactate and base excess were associated with the transfusion (AUROC 0.731 and 0.798, respectively). The optimal calculated cut-off values were 4 mmol/l (lactate) and − 2.5 mmol/l (base excess). When circulatory instability and suspected relevant bleeding were included, the association further improved (AUROC 0.871 and 0.866, respectively).ConclusionPrehospital lactate and base excess could be used in combination with other clinical parameters as indicators of the need for early transfusion. This relationship has yet to be confirmed in the current validation study.Trial registrationGerman Clinical Trials Register,www.drks.de(No. DRKS 00009559).