Impact of Iron Deficiency on the Incidence of Postoperative Infections (CARIPO)

Postoperative infections are one of the most common complication after surgery, involving 2 to 50% of patients according to series and representing 16% of healthcare associated infections. Postoperative infections are highly morbid and result in a significant cost for the society, by increasing the length of hospital stay for example. They also have an impact on bacterial ecology because of the use of broad-spectrum antibiotic therapy to treat nosocomial infection. The decrease of postoperative infections occurrence is a major public health challenge.

Iron deficiency, with or without iron-deficiency anemia, is also very common during the perioperative period. Its prevalence goes from 30 to 40% and even up to 60% when associated with anemia. Iron deficiency is associated with an increased morbidity and mortality. Indeed, iron is a mineral element essential for oxygen transport through hemoglobin, but also implied in cellular metabolism by its role in the electron transport chain and in the citric acid cycle in the mitochondrion. Hence, iron is essential for the proper functioning of the immune system. Iron deficiency leads to an alteration of cellular immune defenses with a decrease in neutrophils function secondary to reduced myeloperoxidase activity, an alteration of their phagocytic capacity, a decrease in the number of T lymphocytes and a weaker response to antigenic exposure, an alteration of Natural Killer lymphocytes activity and a lower interleukine-2 production by lymphocytes. Thus, iron deficiency was associated with an increased risk of sepsis in human.

According to an old cohort published in 1988, a preoperative iron deficiency (defined by ferritin ≤20 ng/L) on 448 patients who underwent abdominal surgery, was associated with an increased in postoperative infections (23 vs 5 infections, p<0,001) and with a longer hospital stay (12±4 vs 8±3 days, p<0,001). However, a recent prospective observational study (2018), regarding orthopedic elective surgery, iron deficiency was not associated with an increased perioperative morbidity nor mortality. The statistical power was limited (100 patients, whose 6 only with iron deficiency, postoperative infections are rare in elective orthopedic surgery and assessed at day 30 instead of day 90 as recommended).

Accordingly, data from literature do not allow us to conclude on how perioperative iron deficiency influences postoperative infections occurrence. Yet, patients might benefit from preoperative iron supplementation. The PREVENTT randomized controlled trial, published in October 2020, studied the impact of intravenous iron supplementation before major abdominal surgery for anemic patients. This trial found a statistically significant decrease in hospital readmission in the treatment group and a downward trend in the occurrence of postoperative infections. Similar results were highlighted in 2016 in a randomized controlled trial comparing the fate of patients according to iron supplementation or not immediately after surgery.

Those results invite to undertake further clinical studies to better characterize the impact of iron deficiency and its correction on postoperative infections occurrence.

Our first hypothesis is that preoperative iron deficiency would be associated with an increased incidence of postoperative infections after major surgery and that its correction would lessen this association.