In this study, we identified several factors that increase the risk of perioperative blood transfusion. Key patient factors include low preoperative hemoglobin, diabetes mellitus, female gender, high ASA score, malignant pathology, and a BMI below 24.9. Additionally, surgical factors such as the length of surgery, volume of blood loss, and scheduled open procedures play a significant role. While we can modify some of these factors before surgery, others remain constant. These factors can be used to develop a scoring system that guides perioperative management. Furthermore, our study findings can be used to develop intraoperative recommendations for patients at high risk of transfusion. These recommendations may include measures to improve hemostasis, such as the use of tranexamic acid, and strategies to reduce blood loss, such as minimally invasive surgery.

In our study, we found that anemia was the strongest risk factor for transfusion. Preoperative anemia affects 47–52% of patients undergoing colorectal surgery and often results from malnutrition, chronic disease, or gastrointestinal bleeding (Ristescu et al. 2019; Kwon et al. 2019). We found patients with preoperative anemia are three times more likely to need more than two units of PRBC compared to those without. Previous research shows that 59% of surgeons believe anesthetists and pre-admission clinics should manage preoperative anemia (Alamri et al. 2018). However, treating anemia in the pre-anesthesia clinic requires a multidisciplinary team, including anesthesia, surgery, hematology, and a dietitian, as well as sufficient time before the scheduled surgery. Current recommendations suggest delaying surgery for 4–6 weeks, if possible, to correct anemia with parenteral or intravenous iron (Mandal et al. 2023). Yet, recent studies show mixed results on whether iron treatment reduces the transfusion rate despite improving hemoglobin levels (Richards et al. 2020; Scrimshire et al. 2020; Moon et al. 2021; McSorley et al. 2020).

Our findings align with previous studies on patient-related risk factors (Halabi et al. 2013; Nilsson et al. 2002). In addition to anemia and blood loss, diabetes was a strong predictor of blood transfusion. It increases the risk of transfusing > 2 units by 140%. Around a quarter of the Saudi population is diabetic and 78% have a poorly controlled disease (Alsuliman et al. 2006); Robert and Al Dawish 2019). This predisposes them to systemic diseases, such as ischemic heart disease, which is associated with a higher transfusion trigger. Poor glycemic control has been correlated with adverse outcomes in colorectal surgery (Nilsson et al. 2002). Additionally, our findings indicate that a normal to low BMI is highly associated with intraoperative transfusion, likely due to malnutrition. Malnutrition, in turn, exacerbates preoperative anemia and increases the risk of blood transfusion (Garcia et al. 2016; Stang and Cornell 1995). These findings strengthen our previous recommendation of a multidisciplinary team including a dietitian and internist in the perioperative planning team.

We also discovered that 28% of patients received unnecessary transfusions, with hemoglobin levels raised to above 11 mg/dl. Over-transfusion not only wastes hospital resources but also increases the risk of postoperative complications (Halabi et al. 2013; Kwon et al. 2019). We found that these patients often begin surgery with a higher hemoglobin. This over-transfusion can be explained by anesthetists' tendency to rely on patients’ comorbidities, hemodynamics, and visual estimation of blood loss to make transfusion decisions. It has led to a wide variation in practice (Aquina et al. 2016). In instances of sudden massive intraoperative blood loss, anesthetists often transfuse patients without evaluating preoperative hemoglobin levels. Additionally, the excessive administration of intravenous crystalloids can cause hemodilution, which may mimic anemia and lead to unnecessary transfusions. Implementing enhanced recovery after surgery (ERAS) protocols can mitigate these issues by emphasizing point-of-care testing for blood replacement, individualized fluid management plans, and avoidance of overhydration (Peden et al. 2023; ( (Gustafsson et al. 2018).

This study has limitations due to its retrospective nature. We did not review surgical notes or anesthesia records. We therefore may have missed other factors that influence transfusion, such as tumor size, cancer stage, location, or vascular injury. Intraoperative hemoglobin is measured using the portable arterial blood gas monitor at our hospital and is not entered into the electronic patient database. Our hospital does not have a thromboelastogram or rotational thromboelastometry. We were therefore unable to include these variables in our results. These results may not apply to all settings as they reflect our surgeons’ surgical techniques, hospital resources, patient population, and non-colorectal surgeries. Therefore, when applying our results to other centers, it is essential to consider these differences. In areas with a strong healthcare system, the prevalence of anemia requiring correction may be lower. In contrast, under-resourced regions may see more patients with anemia and late-stage disease, making preoperative correction less feasible. In addition, facilities with easy access to blood products can afford a lower threshold for surgical interventions, knowing that transfusions are readily available. However, in locations where blood is scarce, more conservative blood management strategies are necessary with an emphasis on preoperative optimization. More research is required to study the effect of preventive strategies on perioperative blood utilization as well as the barriers to their implementation in different populations.

In conclusion, we identified several modifiable and non-modifiable risk factors for perioperative blood transfusion in colorectal surgery. The most significant risk factors include preoperative anemia, diabetes, low BMI, and blood loss. Addressing these factors through the development of clinical pathways and protocols, starting from the preoperative clinic and optimizing intraoperative management, may help conserve blood products and reduce the need for transfusions. Further prospective research is required to confirm these results and improve transfusion risk evaluations and perioperative management.