INTRODUCTION: Multiple studies have suggested blood red blood cell transfusions to be individual markers of post-operative outcomes, including infectious complications. This study set out to examine statistical relationships between red blood cell transfusions and infections following coronary artery bypass grafting surgery,in a retrospective cohort design following patients undergoing CABG in Tampere University Hospital in 2014 and 2015.

METHODS: Preoperative and intraoperative variables were collected in the study, as well as data on intraoperative transfusions. Transfusions of red blood cells were considered an ordinal variable, with stratification following number of units of RBCs transfused. Study outcome variables included development of post-operative pneumonia, mediastinal surgical site infection, or serious nosocomial infection (SNI). Univariate analysis was the mainstay of statistical analysis of collected data. Relevant percentages and p-values were calculated for comparisons of study variables and outcomes.

RESULTS: A total of 461 patients undergoing CABG where included in the study. Red blood cell transfusions where significantly associated with development of post-operative mediastinitis. Totally, 38 patients received 2 units of RBCs, of which mediastinitis presented in 4 cases or 10% of cases in the group (p = 0.03). No statistically significant correlation was observed in the comparison of RBC transfusions and pneumonia or serious nosocomial infection rates. Female sex in patients was significantly associated with development of pneumonia (6 cases of pneumonia, covering 7% of total female patients, compared to 7 cases of pneumonia, accounting for 2 % of male patients, p = 0.007). Obesity (BMI > 30 kg/m2) was associated with a decreased rate of pneumonia (0 pneumonias, or 0% in obese patients, compared to 13 pneumonia patients, representing 4% of the non-obese group, p = 0,024) and SNI (3 cases, or 2% of patients in the obese group, versus 25 cases or 7% in the non-obese group, p = 0,048).

CONCLUSIONS: Statistical analysis revealed an association between transfusion of 2 red blood cell units and mediastinitis post-operation. The study also produced surprising results pertaining to development of infections in obese and female patients. A number of factors limit the reliability of study results, including modest sample size and restriction of analysis to the univariate level. Optimization of intraoperative patient blood management should continue to be an object of further studies.