Figure 4.

Trends in transfusion rates among elective (green), urgent (red), and overall (blue) cases, in patients who underwent aortic arch surgery with hypothermic circulatory arrest between 2008 and 2018, in 12 institutions across Canada. Transfusion rates included packed red blood cells, fresh frozen plasma, platelets, and factor VII. There has been a decline in total transfusion rates over time among overall cases (P < 0.001) and elective cases (P < 0.001), but not among urgent cases (P = 0.06). Trend in time was assessed using mixed-effect regression models with random-effect for the centre to account for the effect of individual centres. The percentages presented are derived from a model and do not translate to a specific number of cases, and they are presented with their 95% confidence intervals. P value was obtained from a linear regression model using date of surgery as a continuous variable to assess a linear trend across the years from 2008 to 2018. *P < 0.05.