Among adults without anemia presenting for elective cardiac surgery, iron deficiency was not associated with fewer days alive and at home when assessed at postoperative day 30 or 90, researchers reported in The Lancet Haematology.

One in two adults undergoing cardiac surgery are iron deficient, and best practice guidelines and consensus statements recommend routine investigation and treatment of iron deficiency before elective cardiac surgery, even in the absence of anemia, Lachlan F. Miles, MBBS, PhD, associate professor in the department of critical care at Melbourne Medical School at the University of Melbourne, Australia, and colleagues wrote. However, it is not clear if non-anemic iron deficiency is associated with worse outcomes.

“To our knowledge, there are no prospectively registered studies in any cardiac or non-cardiac surgical population that have recruited a non-anemic cohort to examine the associations between iron deficiency and patient-centered postoperative outcomes,” the researchers wrote. “To address this gap in the evidence, we aimed to determine whether adults without anemia undergoing elective cardiac surgery who are iron deplete have worse postoperative outcomes than those who are iron replete.”

In a prospective study, Miles and colleagues recruited 480 adults undergoing elective cardiac surgery without anemia, defined as a hemoglobin of less than 130 g/L for men and less than 120 g/L for women, and without concomitant hemoglobinopathy, bone marrow pathology, hemochromatosis, or end-stage renal failure requiring dialysis. The mean age of participants was 64 years; 20% were women and 94% were white. Researchers stratified participants as iron deficient or iron replete based on preoperative testing. Iron deficiency was defined as a serum ferritin of less than 100 g/L or 100 g/L to 300 g/L if transferrin saturation was less than 20% or C-reactive protein was more than 5 mg/L. Primary endpoint was days alive and at home at postoperative day 30.

Within the cohort, 50% was iron deficient and 50% was iron replete.

The iron-deficient group had a median of 22.87 days alive and at home at postoperative day 30 and the iron replete group had a median of 23.18 days, for an unadjusted between-group difference of –0.18 days (95% CI, –0.73 to 0.36; P = .51) and an adjusted between-group difference of –0.11 days (95% CI, –0.66 to 0.45; P = .7).

At postoperative day 90, the iron-deficient group had a median of 82.82 days alive and at home; the iron-replete group had a median of 83.06 days. The difference in medians in the iron-deficient group was no different to the iron-replete group in the unadjusted or adjusted analysis, according to researchers.

Researchers did not observe evidence of between-group differences in the incidence of postoperative complications, including all-cause complication (adjusted OR = 1.24; 95% CI, 0.84-1.83; P = .27), readmission to acute care (aOR = 0.9; 95% CI, 0.58-1.42; P = .66), mortality (aOR = 11.88; 95% CI, 0.66-214.4; P = .094) and complication stratified by body system.

“These results suggest there is no evidence of an identifiable association between iron deficiency (using the definitions in this study) and worse postoperative outcomes or patient welfare in adults without anemia undergoing elective cardiac surgery,” the researchers wrote. “Therefore, using routine preoperative iron studies to stratify risk or to make treatment decisions in this patient population could be low-value care.”