Haemoglobin values, transfusion practices, and long-term outcomes in critically ill patients with traumatic brain injury: a secondary analysis of CENTER-TBI

Abstract

Haemoglobin (Hb) thresholds and red blood cells (RBC) transfusion strategies in traumatic brain injury (TBI) are controversial. Our objective was to assess the association of Hb values with long-term outcomes in critically ill TBI patients. We conducted a secondary analysis of CENTER-TBI, a large multicentre, prospective, observational study of European TBI patients. All patients admitted to the Intensive Care Unit (ICU) with available haemoglobin data on admission and during the first week were included. During the first seven days, daily lowest haemoglobin values were considered either a continous variable or categorised as < 7.5 g/dL, between 7.5-9.5 and > 9.5 g/dL. Anaemia was defined as haemoglobin value < 9.5 g/dL. Transfusion practices were described as "restrictive" or "liberal" based on haemoglobin values before transfusion (e.g. < 7.5 g/dL or 7.5-9.5 g/dL). Our primary outcome was the Glasgow outcome scale extended (GOSE) at six months, defined as being unfavourable when < 5. Of 1590 included, 1231 had haemoglobin values available on admission. A mean Injury Severity Score (ISS) of 33 (SD 16), isolated TBI in 502 (40.7%) and a mean Hb value at ICU admission of 12.6 (SD 2.2) g/dL was observed. 121 (9.8%) patients had Hb < 9.5 g/dL, of whom 15 (1.2%) had Hb < 7.5 g/dL. 292 (18.4%) received at least one RBC transfusion with a median haemoglobin value before transfusion of 8.4 (IQR 7.7-8.5) g/dL. Considerable heterogeneity regarding threshold transfusion was observed among centres. In the multivariable logistic regression analysis, the increase of haemoglobin value was independently associated with the decrease in the occurrence of unfavourable neurological outcomes (OR 0.78; 95% CI 0.70-0.87). Congruous results were observed in patients with the lowest haemoglobin values within the first 7 days < 7.5 g/dL (OR 2.09; 95% CI 1.15-3.81) and those between 7.5 and 9.5 g/dL (OR 1.61; 95% CI 1.07-2.42) compared to haemoglobin values > 9.5 g/dL. Results were consistent when considering mortality at 6 months as an outcome. The increase of hemoglobin value was associated with the decrease of mortality (OR 0.88; 95% CI 0.76-1.00); haemoglobin values less than 7.5 g/dL was associated with an increase of mortality (OR 3.21; 95% CI 1.59-6.49). Anaemia was independently associated with long-term unfavourable neurological outcomes and mortality in critically ill TBI patients.Trial registration: CENTER-TBI is registered at ClinicalTrials.gov, NCT02210221, last update 2022-11-07.

Keywords: Anaemia; Blood transfusion; Haemoglobin; Long-term outcome; Traumatic brain injury.

Fig. 1

Haemoglobin values during the first week of ICU admission. Distribution of haemoglobin values during the first week of Intensive care unit (ICU) admission. The mean haemoglobin values (empty circles) gradually decreased during the first week from 12.62 (SD 2.2) to 9.8 (SD 1.5) g/dL at day 7

Fig. 2

Haemoglobin values over time according to outcomes. Values of Hb over time according to unfavourable outcomes at 6 months (A) and mortality at 6 months (B). Patients with lower haemoglobin values on admission and during the first week of intensive care unit had a higher occurrence of unfavourable neurological outcomes (identified as GOSE < 5) and mortality at 6 months

Fig. 3

Haemoglobin values and unfavourable outcome. Results of logistic models on unfavourable outcomes at six months (GOSE < 5) and A the daily minimum value of haemoglobin during the first week of ICU stay (continuous value); B between haemoglobin subgroups (< 7.5 g/dL, 7.5–9.5 g/dL, and > 9.5 g/dL) during the first week of ICU stay. Any ECI; Any major extracranial injury AIS ≥ 3 defines all the patients with at least one major extracranial injury in any AIS anatomical region

Fig. 4

Haemoglobin values and mortality. Results of logistic models on mortality at 6 months and: A the daily minimum value of haemoglobin during the first week of ICU stay (continuous value); B between haemoglobin subgroups (< 7.5 g/dL, 7.5–9.5 g/dL, and > 9.5 g/dL) during the first week of ICU stay. Any ECI; Any major extracranial injury AIS ≥ 3 defines all the patients with at least one major extracranial injury in any AIS anatomical region