TRANSFUSION OF WHITE-CELL-CONTAINING ALLOGENEIC BLOOD COMPONENTS AND POSTOPERATIVE WOUND-INFECTION - EFFECT OF CONFOUNDING FACTORS

Randomized controlled trials (RCTs) of the relationship between alloge neic transfusion and postoperative bacterial infection at any site hav e generated discordant results, but have suggested an association of t ransfusion with wound infection. To examine the specific association o f perioperative transfusion with wound infection, we reviewed the reco rds of 964 consecutive patients undergoing elective colorectal cancer resection at our hospital. Diagnoses of wound infection were made retr ospectively by the Centers for Disease Control criteria, and transfusi on was defined as number of units of white-cell-containing allogeneic blood components received, The probability of wound infection in assoc iation with the transfusion was calculated following adjustment for th e effects of 12 confounders that had not been previously considered in combination. These factors related to severity of illness, difficulty of operation and risk of wound infection. Wound infection developed i n 39 (11.4%) transfused patients, as compared to 24 (3.9%) untransfuse d subjects (P < 0.0001). In the multivariate analysis, there was a tre nd suggesting an adverse transfusion effect, which amounted to a 7% in crease in the risk of wound infection per unit of red cells or platele ts transfused (relative risk [RR] = 1.07; 95% confidence interval for RR = 0.98-1.16; P = 0.1241). This marginally significant effect was re lated to post-operative (P = 0.1274), rather than perioperative (P = 0 .3061), transfusion. We conclude that allogeneic transfusion may perha ps be associated with a small increase in the risk of post-operative w ound infection, but this small effect can be established only by RCTs enrolling several thousand patients. The modest magnitude of the effec t may have been responsible for the disagreements among the published RCTs.