Postoperative outcomes following cardiac surgery in non‐anaemic iron‐replete and iron‐deficient patients – an exploratory study

Abstract

Iron deficiency anaemia is strongly associated with poor outcomes after cardiac surgery. However, pre-operative non-anaemic iron deficiency (a probable anaemia precursor) has not been comprehensively examined in patients undergoing cardiac surgery, despite biological plausibility and evidence from other patient populations of negative effect on outcome. This exploratory retrospective cohort study aimed to compare an iron-deficient group of patients undergoing cardiac surgery with an iron-replete group. Consecutive non-anaemic patients undergoing elective coronary artery bypass grafting or single valve replacement in our institution between January 2013 and December 2015 were considered for inclusion. Data from a total of 277 patients were analysed, and were categorised by iron status and blood haemoglobin concentration into iron-deficient (n = 109) and iron-replete (n = 168) groups. Compared with the iron-replete group, patients in the iron-deficient group were more likely to be female (43% vs. 12%, iron-replete, respectively); older, mean (SD) age 64.4 (9.7) vs. 63.2 (10.3) years; and to have a higher pre-operative EuroSCORE (median IQR [range]) 3 (2-5 [0-10]) vs. 3 (2-4 [0-9]), with a lower preoperative haemoglobin of 141.6 (11.6) vs. 148.3 (11.7) g.l . Univariate analysis suggested that iron-deficient patients had a longer hospital length of stay (7 (6-9 [2-40]) vs. 7 (5-8 [4-23]) days; p = 0.013) and fewer days alive and out of hospital at postoperative day 90 (83 (80-84 [0-87]) vs. 83 (81-85 [34-86]), p = 0.009). There was no evidence of an association between iron deficiency and either lower nadir haemoglobin or higher requirement for blood products during inpatient stay. After adjusting the model for pre-operative age, sex, renal function, EuroSCORE and haemoglobin, the mean increase in hospital length of stay in the iron-deficient group relative to the iron-replete group was 0.86 days (bootstrapped 95%CI -0.37 to 2.22, p = 0.098). This exploratory study suggests there is weak evidence of an association between non-anaemic iron deficiency and outcome after cardiac surgery after controlling for potentially confounding variables.

An international consensus statement on the management of postoperative anaemia after major surgical procedures

“…In observational studies of patients undergoing abdominal or cardiac surgery, pre‐operative non‐anaemic iron deficiency was associated with poor outcomes, including: increased rates of postoperative infection; transfusion; fatigue; and prolonged hospital stay . Although it is presently unknown whether pre‐operative correction of non‐anaemic iron deficiency may offset the excess of risk of postoperative complications, some guidelines recommend peri‐operative iron supplementation for patients with non‐anaemic iron deficiency .…”

Management of Perioperative Iron Deficiency Anemia

“…In 100 consecutive cardiac procedures, preoperative ID was frequent (37%), and it was associated with preoperative anemia, higher RBCT requirements, and postoperative fatigue [11]. In a retrospective cohort of 277 cardiac surgeries, prevalence of ID was 39%, and univariate analysis suggested that ID was associated with a longer hospital stay and fewer days alive out of hospital on postoperative day 90 [12]. In a retrospective cohort of 115 total hip arthroplasties at the first author’s center, patients with ID ( n = 54: 45 ID, 9 FID) have lower perioperative Hb, higher prevalence of preoperative anemia, higher RBCT rate, without differences in pretransfusion Hb, and a trend to longer hospital stays than those without ID [unpubl.…”

Is Iron Deficiency Correction the Real Ultimate Goal of Patient Blood Management?

“…Herein, the study findings added some credits to the compiled knowledge about the strong incidence of preoperative ID (31%) in elective cardiac surgery patients and the high prevalence of red blood cell transfusion (23% v 12%, p < 0.03) during intraoperative surgery in this population. 2,3 Although supported by the literature, 4 the authors did not find significant difference in the postoperative red blood cell transfusion despite a high incidence of combined surgical procedure in the ID group. This result could be explained partly by the small size of this study that analyzed 272 patients.…”