Table 4.
Clinical studies assessing the association between hemoglobin concentrations, anemia, or transfusion and subsequent outcomes among patients with traumatic brain injury
| Study | Patients | Design and setting | Exposure | Pre-transfusion Hb or Hct | Analysis (variables) | Main result |
| Carlson and colleagues [143] | 169 | Retrospective Single-center |
- Number of days hct <30% - Nadir hct - RBC transfusion |
Not reported | Linear regression assessing GOS as continuous variable | - Number of RBC units, lowest hct associated with worse discharge outcome - Number of days hct <30% associated with better outcome |
| ‡Steyerberg and colleagues [144] | 3554 |
Post hoc analysis of several RCTs Multi-center |
Admission Hb (median 12.7 g/dl) | Not relevant | Logistic regression (10 covariates) | - Lower Hb associated with poor 3 to 6 month outcome (OR for 14.3 g/dl vs. 10.8 g/dl = 0.78, 0.70 to 0.87) - Laboratory variables (Hb and glucose) improved prognostic models |
| Duane and colleagues [145] | 788 | Retrospective Single-center |
Hb in first 72 hours RBC transfusion |
Not reported | Logistic regression (age, ISS, total blood products) | - Minimum hemoglobin in first 72 hours associated with hospital mortality (OR = 0.86, 0.73 to 1.0 per g/dl increment) - RBC transfusions not associated with mortality, but with nosocomial infection |
| Salim and colleagues [146] | 1150 | Retrospective (prospective database) Single-center |
Anemia (Hb <9 g/dl; occurred in 46%) and RBC transfusion (46%) | Not reported | Logistic regression (10 covariates) | - RBC transfusion associated with hospital mortality (OR = 2.2, P = 0.004) and complications (OR = 3.7, P < 0.0001) - Anemia associated with adverse outcomes only when transfusion not included in model |
| George and colleagues [147] | 82 (Hb 8.0 to 10.0 g/dl) | Retrospective Single-center |
RBC transfusion (52%) | 8.6 g/dl | Cox proportional hazard regression (age, motor GCS, blood ethanol, lowest Na+, complications) | RBC transfusion predicted mortality (P < 0.05) |
| ‡Van Beek and colleagues [148] | 3872 |
Post hoc analysis of several RCTs Multi-center |
Admission Hb | Not relevant | Logistic regression (age, motor score, pupil reactivity) | - Lower Hb associated with higher risk of death/vegetative state at 3 to 6 months (OR = 0.69, 0.60 to 0.81, for 75th percentile vs. 25th percentile) |
| Schirmer-Makalsen and colleagues [149] | 133 | Retrospective Single-center |
Hb ever <8 g/dl (22%) | Not reported | Logistic regression (10 covariates) | A single Hb <8 g/dl did not predict adverse outcome |
| McIntyre and colleagues [150] | 67 |
Post hoc analysis of RCT Multi-center |
Comparison of transfusion thresholds of 7.0 g/dl vs. 10.0 g/dl | Not reported | Logistic regression (age, APACHE II, PAC use) | - 30-day mortality 17% in restrictive group vs. 13% in liberal group (P = 0.64) - Development of MOD and ICU LOS similar in both groups |
| Robertson and colleagues [151] | 102 | Prospective Single-center |
Hb at time of CBF determination | Not reported | Logistic regression (age, CBF, GCS, CPP, CMRO2) | - Lower Hb associated with unfavorable GOS after 3 months |
‡ Based, in part, on same datasets
APACHE = Acute Physiology and Chronic Health Evaluation; CBF = cerebral blood flow; CMRO2 = cerebral metabolic rate; CPP = cerebral perfusion pressure; GCS = Glasgow Coma Scale; GOS = Glasgow Outcome Scale; Hb = hemoglobin; hct = hematocrit; ICU = intensive care unit; ISS = injury severity score; LOS = length of stay; MOD = multiple organ dysfunction; OR = odds ratio; PAC = pulmonary artery catheter; RBC = red blood cell; RCT = randomized controlled trial.