Prior to evaluating CBC abnormalities and determining appropriate transfusion strategies, hemostatic defects such as inherited coagulation and platelet (PLT) disorders must be ruled out. In major studies concerning transfusion based on abnormal CBC findings, patients with inherited hemostatic defects were either excluded or not further analyzed. Therefore, these patients should be categorized separately and undergo preoperative patient optimization according to the specific guidelines for each condition.

Identifying these patients is crucial. Excessive postoperative bleeding, as reported by surgeons, occurs in approximately 3% of all surgical procedures [4]. Laboratory assessments including, PLT count, prothrombin time, and activated partial thromboplastin time (aPTT) tests, have been employed to predict the risk of excessive postoperative bleeding. However, these preoperative screening tests exhibit no correlation with surgery-induced hemorrhage, exhibiting low sensitivity (<35%) and a positive predictive value (<3%) [5, 6]. Furthermore, given the lack of evidence supporting the efficacy of such tests in reducing postoperative bleeding, the routine implementation of these conventional screenings across all surgical patients is not warranted [6, 7].

Preoperative screening tests for hemostatic defects are deemed insufficient for several reasons. First, most patients with inherited coagulation and PLT disorders are diagnosed early in life, typically before the age of 10 years [8–12]. For adult patients undergoing surgery, obtaining a patient history is a faster and more cost-effective method for detecting inherited hemostatic defects. Second, the predominant cause of postoperative bleeding is not hemostatic failure but rather surgical or technical complications, which can be appropriately addressed by surgical interventions [5, 13]. Lastly, the traditional tests (PLT count, prothrombin time, and aPTT tests) are primarily designed to detect static disorders. Consequently, preoperative tests cannot reliably predict hemostatic disorders that may arise during surgery, such as disseminated intravascular coagulation, hyperfibrinolysis, and thrombocytopenia.

In conclusion, the risk of bleeding associated with surgery should be initially assessed through thorough history taking and physical examination, followed by selective preoperative screening tests in individuals deemed at high risk. Table 1 summarizes the relevant questions for this purpose, while Table 2 outlines the specific preoperative screening tests for each bleeding risk [14].

The human hemostatic system maintains a delicate balance between procoagulant and anticoagulant mechanisms. Procoagulant actions include PLT adhesion, aggregation, and fibrin clot formation, while anticoagulant mechanisms involve the natural inhibitors of coagulation and fibrinolysis. Typically, hemostasis is finely regulated to facilitate blood flow while also being prepared for rapid clot formation to stop bleeding and prevent excessive blood loss. The key components of this system include (1) PLTs and other blood components, such as monocytes and erythrocytes; (2) plasma proteins, including coagulation and fibrinolytic factors and inhibitors; and (3) vessel walls [15]. Preoperative PLT transfusion is employed in clinical practice to reduce the risk of bleeding during and after surgery; however, PLTs are only one component of the hemostatic process.

The relationship between a decrease in PLT count and the risk of nontraumatic bleeding remains undefined, with several clinical factors needing consideration. The PLADO study, a multicenter, randomized, controlled trial, evaluated the association between PLT count, transfusion practices, and bleeding outcomes in patients undergoing chemotherapy or stem cell transplantation (SCT) at risk for developing hypoproliferative thrombocytopenia [16]. The study enrolled 1,077 patients, including 378 who underwent autologous SCT, 413 who underwent allogeneic SCT, and 286 who received chemotherapy for hematologic malignancies.

Patients with a PLT count of ≤5 × 10⁹/L demonstrated a higher bleeding risk compared with those with a PLT count of ≥81 × 10⁹/L. In the multivariate analysis of grade 2 or greater bleeding, laboratory parameters associated with increased bleeding included a PLT count of ≤5 × 10⁹/L, a hematocrit count of ≤25%, an INR of >1.2, and an aPTT of >30 s. However, in a multivariate analysis of grade 3 or higher bleeding requiring red blood cell (RBC) transfusion, PLT count was not significantly associated. Additionally, PLT transfusions administered on the days of bleeding often prove insufficient to alter bleeding outcomes the following day. In another study of hospitalized patients undergoing SCT or chemotherapy for hematologic cancers or solid tumors, where prophylactic PLT transfusions were administered based on thresholds ranging from approximately 20–70 × 10⁹/L, prophylactic PLT transfusion did not affect the incidence of bleeding [17].

Studies on the optimal PLT threshold and appropriate transfusion dose to reduce the bleeding risk remain limited. The PLT thresholds recommended for different procedures according to each guideline are summarized in Table 3 [18–22].

In a cohort study involving adult patients aged 18 years or older (n = 232,440) requiring inpatient care, approximately 20% presented with anemia upon admission, while more than 50% developed anemia during admission [23]. Patients who presented anemia upon admission had significantly higher mortality rates than in those without anemia, with the risk increasing significantly if the anemia worsened during the hospitalization period. In 18 large observational studies involving more than 650,000 surgical patients, the mean prevalence of preoperative anemia was approximately 35%, ranging from 10.5% to 47.9% depending on the type of surgery [24]. After adjusting for several potential confounders, including age, sex, and underlying medical conditions, preoperative anemia emerged as an independent risk factor for increased postoperative morbidity and mortality and prolonged hospital stays [24].

The effectiveness of RBC transfusions in reducing mortality among hospitalized patients or those undergoing surgery with anemia remains uncertain. Although RBC transfusions rapidly increases hemoglobin (Hb) levels, the effectiveness of transfusions in improving tissue oxygen consumption or reducing tissue oxygen debt is still unknown. Additionally, RBC transfusions are frequently linked with poor outcomes. In critically ill patients and those undergoing surgery, transfusion of a single unit of packed RBCs is associated with a higher multivariate risk of mortality, wound complications, pulmonary problems, postoperative renal dysfunction, systemic sepsis, composite morbidity, and prolonged postoperative hospital stays compared with propensity-matched patients who did not receive intraoperative RBC transfusion [24–28]. In summary, although the postoperative mortality rate increases in patients with anemia, RBC transfusion does not decrease this rate. However, the adverse effects associated with transfusion may increase the incidence of postoperative complications and mortality.

Given the clinical drawbacks associated with both preoperative anemia and perioperative RBC transfusion, individualized strategies must be developed to minimize RBC transfusion, with the ultimate goal of improving patient outcomes. To achieve this goal, a structured approach that includes 1) the correction of preoperative anemia, 2) implementation of surgical techniques and perioperative strategies to minimize transfusion requirements, and 3) postoperative patient care is required. In alignment with the focus of this review, particular emphasis was placed on the correction of preoperative anemia. Based on the World Health Organization criteria, anemia is defined as Hb levels of <13 g/dL for adult men and <12 g/dL for adult women. However, for surgeries with the potential for blood loss exceeding 500 mL or a likelihood of transfusion of ≥10%, preoperative anemia is defined as an Hb level of <13 g/dL regardless of sex [29]. The basic checklist and the management of patients with preoperative anemia are summarized in Fig. 1.

The goal of correcting preoperative anemia is to stabilize oxygen delivery during surgery. The use of the Fick equation to assess anemia revealed that increasing blood flow could effectively increase oxygen delivery (Fig. 2). Additionally, erythropoiesis-stimulating agents (ESAs) are effective in increasing Hb concentration and improving oxygen delivery. The role of ESAs in managing preoperative anemia remains uncertain, with varying guidelines [30–32]. Concerns arise regarding the cardiovascular risks associated with their use in managing chronic kidney disease and cancer [33]. However, recent systematic reviews have suggested that preoperative ESA use reduces transfusion risk without increasing the incidence of thrombosis [34, 35]. When combined with iron therapy, ESAs further reduced the need for transfusions without significantly increasing the incidence of adverse events. Shortterm ESA use (2–4 weeks) appears safe in the preoperative setting; however, its cost-effectiveness and overall impact on patient outcomes warrant further investigation.