Anemia can develop in patients undergoing colorectal cancer surgery because of various factors, including cancer-related blood loss, malnutrition, neoadjuvant chemotherapy, systemic inflammation, and intraoperative blood loss. Even though preoperative intravenous iron has been utilized to treat anemia, postoperative transfusion may still be necessary because of the correlation between anemia and postoperative complications, such as anastomotic leakage, which sometimes results in death [1]. However, numerous reports suggest the occurrence of adverse effects from a blood transfusion during oncologic surgery, such as postoperative infectious complications or long-term disease recurrence. In addition, the transfusion volume could affect the surgical outcome due to its immunosuppressive effect. Based on previous studies, efforts have been made to determine the appropriate threshold of hemoglobin (Hgb) levels for postoperative transfusion [1–5].

The liberal transfusion strategy has been adopted as the conventional transfusion practice when the Hgb level is below 10 g/dL to maintain stable blood circulation and enhance blood perfusion at the anastomotic site [1]. However, controversies have emerged concerning the optimal transfusion strategy for anemic patients especially in critical care. These controversies have been described in several randomized controlled studies, which showed the noninferiority of restrictive transfusion [6]. Moreover, this issue extends to anemic patients in the postoperative period following colorectal surgery because of the increasing adverse surgical outcomes resulting from transfusion. Several randomized studies endorse a restrictive transfusion strategy to decrease the disastrous effects of allogeneic blood transfusion [7, 8]. These controversies also contributed to the shift towards patient blood management for elective surgeries, which recommend nontransfusion management such as iron or folate supplements and the stimulation of erythropoiesis in the perioperative period [9]. Accordingly, restrictive transfusion strategy was admitted which involves judicious withholding of blood transfusions in patients without significant bleeding and deferring transfusion until the Hgb level is as low as 7 g/dL [1, 10–12].

During the COVID-19 pandemic, surgeons found it difficult to manage anemia due to decreased blood donations. Fear of infection and restriction of blood compound supply were probable causes for the decrease [13]. As the blood supply became insufficient, many changes were made to the transfusion policy worldwide, including at our center, Ewha Womans University Mokdong Hospital (Seoul, Korea). For transfusions, the recommended Hgb threshold level was lowered to 7.0 g/dL, whereas there had been no specific limitations for transfusion before the spread of COVID-19. The restrictions on transfusions also resulted in insufficiencies in the correction of anemia in the postoperative period for patients who underwent elective and emergency surgery. In this study, we investigated whether changes in blood transfusion policy in the prepandemic and postpandemic eras influenced the occurrence of infectious complications and suggested anemia restoration guidelines for a safe colorectal surgery.

In this study, we evaluated the effect of restrictive versus liberal transfusion on the occurrence of postoperative infectious complications by comparing the pre– and post–COVID-19 groups in terms of the restrictive transfusion policy administered during the spread of COVID-19. Our study demonstrated no significant difference in the occurrence of infectious complications (anastomotic leakage, organ/space SSIs, and overall infectious complications) between the restrictive strategy of the post–COVID-19 group and the liberal strategy of the pre–COVID-19 group. Based on our findings, it seems necessary to reconsider the standard Hgb level for postoperative transfusion.

Controversies surrounding restrictive and liberal transfusion strategies have emerged due to the established adverse effects of blood transfusion on the human immune system, primarily through transfusion-associated immunomodulation [16, 17]. Numerous studies have been published on the negative outcomes of postoperative transfusions and the effects of restrictive or liberal transfusions in patients experiencing postoperative anemia. Recently, the consensus regarding transfusion strategies has changed, with growing evidence suggesting that a restrictive transfusion is not associated with harm compared with a liberal transfusion strategy [10–12, 18, 19]. A systematic meta-analysis of the effects of transfusion on short- and long-term prognosis [20] suggested that postoperative transfusion increases short-term adverse effects, including infectious complications and anastomotic leakage. The negative effects of blood transfusion have led to controversies regarding the necessity of liberal transfusion and the efficacy of restrictive transfusion. Another systematic review and meta-analysis [21] elucidated that restrictive transfusion decreased the risk of serious healthcare-associated infections compared with liberal transfusion. Carson et al. [22] also suggested that liberal transfusion did not reduce mortality or in-hospital morbidity compared with restrictive transfusion, and in another study [5], suggested that there were no differences in long-term mortality between the 2 strategies. Numerous studies have suggested that postoperative transfusion has a negative effect on postoperative outcomes [16, 19, 23], and restrictive transfusion has no significant disadvantages compared with liberal transfusion in the postoperative period [1, 5, 11, 22].

Consistent with previous studies, our study showed that the transfusion group tended to develop more infectious complications than the nontransfusion group (Table 2). The higher incidence of infectious complications in the transfused group can be attributed to the implementation of transfusion and other confounding factors. We hypothesized that confounding factors in the transfusion group would contribute to the results of multivariate analysis. Consequently, the findings from our study could be interpreted as suggesting that transfusion was associated with adverse outcomes, which is consistent with previous studies [19, 24, 25]. While our multivariate analysis, as presented in Table 3, did not identify any risk factors, including the implementation of transfusions, a subsequent subgroup analysis, detailed in Supplementary Table 1, revealed stoma formation as a risk factor for infectious complications. It is speculated that the association between infectious complication and stoma formation would attribute to the higher frequency of emergency operation such as colon perforation or ischemia. It is worth noting that the incidence of anastomotic leakage within our study population remained relatively low. Therefore, the positive correlation between stoma formation and infectious complications, as established in our study, does not offer a comprehensive explanation for the association between stoma formation and anastomotic leakage.

Subgroup analysis within the transfusion group was performed to evaluate the association between restrictive or liberal transfusion and the occurrence of infectious complications. There was no interaction of infectious complication, and the postoperative lowest Hgb level categorized into 2 groups (Hgb <7 g/dL vs. 7 g/dL≤Hgb<10 g/dL), and this finding suggested that the impact on adverse surgical outcomes did not differ between the liberal strategy and restrictive transfusion. Our findings align with previous studies that have consistently insisted on the lack of advantages or even disadvantages of liberal transfusion related to the occurrence of infectious complications compared with the restrictive transfusion strategy [1]. As a result, the administration of transfusions at lower Hgb levels according to the patient’s condition could be considered as an effective practice for managing postoperative anemia, allowing for the optimization of medical resources by minimizing unnecessary transfusions.

The present study has several limitations. First, we enrolled a small population of patients at a single institution. Second, our study findings were limited to a 30-day postoperative period, and potential complications beyond this period were not investigated. Third, there were no data on the oncologic outcomes due to the limited follow-up period. However, the methodological strength of the present study is that we utilized the transition of the blood transfusion policy resulting from the emergence of the COVID-19 pandemic without any change in the treatment strategy. This approach enabled objective evaluation of the association between transfusion and surgical outcomes.

In conclusion, we found that restrictive transfusion was sufficient for patients who underwent colorectal cancer surgery, particularly under circumstances of limited availability of medical resources, such as during the COVID-19 pandemic. The impact of restrictive and liberal transfusions on negative surgical outcomes did not differ. Although the administration of transfusion itself was not independently associated with infectious complications, transfused patients showed more adverse surgical outcomes. It is crucial to make judicious decisions regarding the implementation of transfusion in patients with postoperative anemia by adequately evaluating their overall condition. To prevent the waste of medical resources and unnecessary transfusion, surgeons should consider prudent transfusion practices in the postoperative period by adopting a restrictive transfusion strategy.