The Impact of Preoperative Anemia on Postoperative Outcomes in Liver Resection: A Propensity Score Matching Analysis

Globally, anemia affects approximately 33% of the population, with nearly 50% of cases attributed to iron deficiency. In Thailand, anemia remains a significant public health issue, with prevalence rates of 24% among women of reproductive age, 23.8% among nonpregnant women, and 32.2% among pregnant women. Iron deficiency anemia (IDA) is the leading and most common cause of anemia worldwide, and it is highly prevalent in Thailand. Moreover, the situation in Thailand is often exacerbated by the widespread incidence of thalassemia and hemoglobinopathies, with 30% to 40% of the population carrying thalassemia genes.

According to the World Health Organization (WHO), anemia is defined as a hemoglobin concentration of less than 12 g/dL in nonpregnant women and less than 13 g/dL in men. The prevalence of preoperative anemia among surgical patients has been reported to be between 32% and 48%. Preoperative anemia is one of the most common medical conditions encountered in surgical patients, with a prevalence ranging from 20% to 45% depending on the type of surgery. Specifically, in hepato-pancreato-biliary (HPB) surgery, 16.9% to 32.8% of patients present with anemia prior to surgery.

Preoperative anemia is a well-established predictor of the need for perioperative blood transfusions in liver resection, as supported by multiple studies. Perioperative allogeneic blood transfusions are associated with numerous adverse outcomes, both short-term and long-term. These include transfusion reactions, increased rates of postoperative infections, cardiopulmonary and thromboembolic events, prolonged mechanical ventilation, re-operations, extended hospital and ICU stays, elevated postoperative morbidity, increased tumor recurrence, reduced disease-specific survival, and decreased overall survival.

A large retrospective study reported a prevalence of preoperative anemia at 32.8%, which was associated with higher rates of postoperative major morbidities and mortality. After adjusting for confounding factors-such as age, type of liver resection, ASA classification, preoperative laboratory results, comorbidities, functional status, and diagnosis-patients with preoperative anemia were found to have a 21% higher risk of developing major morbidities within 30 days (adjusted odds ratio 1.21, 1.09-1.33). These morbidities included organ space infections, sepsis, septic shock, prolonged postoperative ventilator use (>48 hours), unplanned reintubation, pneumonia, and acute kidney injury requiring dialysis. However, preoperative anemia was not associated with increased postoperative mortality in liver resection (adjusted odds ratio 0.88, 0.66-1.16).

Furthermore, a retrospective study involving 4,170 patients demonstrated that preoperative anemia was associated with an increased risk of major postoperative complications compared to patients without anemia (24% versus 19%). After adjusting for confounders, including age, sex, race, obesity, extent of liver resection, comorbidities, functional status, and clinical and biochemical markers of liver dysfunction and portal hypertension, preoperative anemia was linked to a threefold increased risk of blood transfusion, a twofold increased risk of prolonged hospitalization, and higher healthcare costs in anemic patients. These findings suggest that anemia significantly impacts resource utilization in liver resection.