Significantly higher death rates in blood type O severe trauma patients

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red blood cells in veinBlood type O was significantly associated with high mortality in severe trauma patients and might have a great impact on outcomes., according to a study that involved 901 Japanese emergency care patients. Researchers at Tokyo Medical and Dental University Hospital, Japan found that severe trauma patients (those with an injury that has the potential to cause long-term disability or death) with blood type O had a death rate of 28%, compared to a rate of 11% in patients with other blood types.

Dr Wataru Takayama, the corresponding author said: “Recent studies suggest that blood type O could be a potential risk factor for haemorrhage. Loss of blood is the leading cause of death in patients with severe trauma but studies on the association between different blood types and the risk of trauma death have been scarce. We wanted to test the hypothesis that trauma survival is affected by differences in blood types.”

Patients with blood type O have been shown to have lower levels of von Willebrand factor, a blood clotting agent, than those with other blood types. Lower levels of von Willebrand factor may be linked to higher levels of haemorrhage. The authors suggest that a lower level of the factor is a possible explanation for the higher death rate in trauma patients with blood type O.

Takayama said: “Our results also raise questions about how emergency transfusion of O type red blood cells to a severe trauma patient could affect homeostasis, the process which causes bleeding to stop, and if this is different from other blood types. Further research is necessary to investigate the results of our study and develop the best treatment strategy for severe trauma patients.”

The authors used data from medical records of 901 patients with severe trauma who had been transported to either of two tertiary emergency critical care medical centres in Japan during 2013 to 2016.

The authors caution that all the patients whose data was analysed in this study were Japanese and therefore there is a need for further research to understand if the findings apply to other ethnic groups. Additionally, there was no evaluation of the impact of the individual blood types A, AB or B on severe trauma death rates. Instead, the authors compared type O to non-O blood type which may have diluted the effect of individual blood types on patient survival.

Background: Recent studies have implicated the differences in the ABO blood system as a potential risk for various diseases, including hemostatic disorders and hemorrhage. In this study, we evaluated the impact of the difference in the ABO blood type on mortality in patients with severe trauma.
Methods: A retrospective observational study was conducted in two tertiary emergency critical care medical centers in Japan. Patients with trauma with an Injury Severity Score (ISS) > 15 were included. The association between the different blood types (type O versus other blood types) and the outcomes of all-cause mortality, cause-specific mortalities (exsanguination, traumatic brain injury, and others), ventilator-free days (VFD), and total transfusion volume were evaluated using univariate and multivariate competing-risk regression models. Moreover, the impact of blood type O on the outcomes was assessed using regression coefficients in the multivariate analysis adjusted for age, ISS, and the Revised Trauma Score (RTS).
Results: A total of 901 patients were included in this study. The study population was divided based on the ABO blood type: type O, 284 (32%); type A, 285 (32%); type B, 209 (23%); and type AB, 123 (13%). Blood type O was associated with high mortality (28% in patients with blood type O versus 11% in patients with other blood types; p <  0.001). Moreover, this association was observed in a multivariate model (adjusted odds ratio = 2.86, 95% confidence interval 1.84–4.46; p <  0.001). The impact of blood type O on all-cause in-hospital mortality was comparable to 12 increases in the ISS, 1.5 decreases in the RTS, and 26 increases in age. Furthermore, blood type O was significantly associated with higher cause-specific mortalities and shorter VFD compared with the other blood types; however, a significant difference was not observed in the transfusion volume between the two groups.
Conclusions: Blood type O was significantly associated with high mortality in severe trauma patients and might have a great impact on outcomes. Further studies elucidating the mechanism underlying this association are warranted to develop the appropriate intervention.

Wataru Takayama, Akira Endo, Hazuki Koguchi, Momoko Sugimoto, Kiyoshi Murata, Yasuhiro Otomo

Biomed Central material
Critical Care abstract

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