Double #Vena-cava-superior | Figure 1

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Double #Vena-cava-superior

Plasma transfusions before major surgery (other than heart surgery) or invasive procedures, to prevent bleeding

Review question
Human plasma, a blood component, is often transfused to people before undergoing surgery or other procedures (such as inserting a chest drainage tube) when blood tests show that their blood may not clot adequately. Aims of this review were to assess how effective this practice is in reducing subsequent bleeding or need for blood transfusion, and whether this approach increases risk of death or other significantly harmful effects. The review excluded people with inherited bleeding disorders and those taking medication that reduces their blood's clotting ability.

Background
Human plasma is obtained from blood donors. It contains many factors that help blood to clot. Although plasma may be transfused to people based on blood tests suggesting that their blood may not clot adequately, these tests have limitations. A person's blood may clot adequately despite abnormal test results. Abnormal test results also do not clearly predict those people who will go on to bleed. Furthermore, plasma transfusion corrects abnormal blood tests to varying degrees. Plasma is also expensive, and some countries have issues with blood product shortages, donor reliability, and incomplete screening for infections that could be transmitted through blood product transfusion. Given the potential for life-threatening complications from plasma transfusion, its use in this setting carries risk of harm without clear evidence of benefit.

Study characteristics
We included five trials which were all conducted in high-income countries. Our search is current up until 28 January 2019. One trial compared plasma transfusion with no transfusion given. Another trial compared plasma or platelet transfusion or both with neither plasma nor platelet transfusion given. One trial compared plasma transfusion with alternative products given to help blood clot. Another trial compared different blood tests to trigger a plasma transfusion, and still another trial compared different transfusion triggers using the same blood test. Four trials involved adult participants over 18 years old, and the fifth trial did not specify age of participants. In four trials, participants underwent bedside procedures. Only one trial involved some participants undergoing major surgical operations. Two trials included only participants in intensive care, and two trials included only participants with liver disease. One trial recruited only two participants. Therefore review results include the remaining four trials, incorporating 234 participants. Three further trials are ongoing.

Key results
When plasma transfusion was compared with no transfusion given, we are very uncertain whether there was a difference in major bleeding, number of blood transfusions per participant, or harmful effects from the transfusion (1 trial; very low-quality evidence). When plasma or platelet transfusion or both were compared with neither plasma nor platelet transfusion, we are very uncertain whether there was a difference in mortality within 30 days, or in the number of individuals requiring a transfusion (1 trial; very low-quality evidence). When plasma transfusion was compared with other haemostatic agents, we are very uncertain whether there was a difference in major bleeding or in harmful effects from the transfusion (1 trial; very low-quality evidence). When different triggers for plasma transfusion were compared (1 trial; 60 participants), we are very uncertain whether there was a difference in major bleeding or in harmful effects from the transfusion due to very low-quality evidence for these outcomes. The number of people requiring blood products may have been reduced overall, although this is based on low-quality evidence. No trials reported procedure-related harmful events or quality of life as an outcome.

Quality of the evidence
The overall quality of the evidence was predominantly very low over a range of clinically important outcomes due to combinations of issues within the studies, such as potential for bias, limited clinical settings, and imprecise estimates of intervention effects.

Authors' conclusions
We are very uncertain of the effectiveness and safety of the use of plasma in non-cardiac operations or invasive procedures due to very low-quality evidence. Furthermore, as trials do not cover a wide range of surgical contexts, our confidence in applying study results to the wider surgical setting is limited. Overall limited evidence for the utility of plasma transfused to people within this context is of insufficient quality to support or oppose its use.