Prevalence and predictors of hypotension on hospital arrival in traumatic brain injury: a prehospital HEMS cohort study

Hypotension is a well-established predictor of poor outcomes and increased mortality in patients with traumatic brain injury (TBI). Even a single episode of low systolic blood pressure (SBP) during the prehospital phase is associated with a worse prognosis. To minimise secondary brain injury, early identification and management of hypotension are critical. While international guidelines increasingly recommend higher SBP thresholds in TBI care, structured prehospital data remain limited in the German emergency care context. This study aimed to quantify the prevalence of hypotension on hospital arrival among adult TBI patients transported by helicopter emergency medical services (HEMS) and to identify high-risk subgroups. This retrospective cohort study analysed ADAC Luftrettung mission data from 2017 to 2021. Adults (≥ 18 years) with documented TBI in the mission record were included. Hypotension was defined as SBP < 90 mmHg in line with current German guidance. Two time points were assessed: SBP at initial HEMS contact ("initial hypotension") and SBP on hospital arrival ("hypotension on hospital arrival"). TBI severity was classified by Glasgow Coma Scale (GCS), and injury patterns were recorded as isolated TBI, multiple injuries (non-polytrauma; "Mehrfachverletzung"), or polytrauma. A multivariable logistic regression was used to identify independent predictors of hypotension on hospital arrival. A total of 20,756 patients were included (67.7% male; median age 55.0 years). Hypotension on hospital arrival occurred in 3.4% of patients overall and in 35.5% of those with initial hypotension. Initial hypotension was the strongest predictor of hypotension on hospital arrival (OR 13.82, 95% CI 11.47-16.65). Severe TBI (OR 4.26, 95% CI 3.41-5.32) and polytrauma (OR 3.08, 95% CI 2.44-3.90) were additional independent predictors. Initial hypotension identifies a high-risk subgroup of adult TBI patients transported by HEMS who are substantially more likely to be hypotensive at hospital arrival, particularly those with severe TBI and polytrauma. These findings support prioritising early haemodynamic stabilisation in this population and provide a basis for future outcome-linked studies in the German setting.