Aetiology of preoperative anaemia in patients undergoing elective cardiac surgery Jacob Abhrahm 1,Romi Sinha 2,Kathryn Robinson 3, David Cardone 1 1 Department of Anaesthesia and Intensive Care, Royal Adelaide Hospital 2 Blood, Organ and Tissue Programs, Department for Health and Ageing, SA Health 3 Bloodsafe Programs, SA Health Background Preoperative anaemia and red cell transfusion are associated with increased morbidity and mortality. Aim To determine the likely aetiology of preoperative anaemia in patients undergoing elective cardiac surgery from July 2011 to June 2013 at a tertiary referral hospital in South Australia. Methods Laboratory data up to 6 weeks preoperatively was used to stratify patients into diagnostic categories according to the ‘Preoperative haemoglobin assessment and optimisation template’ of the National Patient Blood Management (PBM) guidelines Perioperative Module (2012). Results 442 patients undergoing elective cardiac surgery were included. The median age of the cohort was 66 years (IQR 57-74) and 70% were male. Overall prevalence of anaemia was 20.6% (91/442). When patients with preoperative anaemia were stratified according to the preoperative haemoglobin optimization and assessment template (Figure 1), initial analysis showed that 17 patients had serum ferritin <30 µg/L 25 patients had serum ferritin between 30 and 100 µg/L 49 had serum ferritin >100 µg/L Patients with serum ferritin between 30 and 100 µg/L, 6 had raised C reactive protein (CRP) and were further classified into possible iron deficiency The remaining 19 patients with normal CRP, and collectively with 49 patients with serum ferritin >100 µg/L were classified as possible anaemia of chronic disease (ACD). Therefore, 21 (23.1%) were categorised as having ‘iron deficiency anaemia’ (IDA), 6 (6.6%) ‘possible iron deficiency’ and 64 (70.3%) ‘possible anaemia of chronic disease (ACD) / other cause’ based on the assessment algorithm within the PBM guidelines. Of those categorised as having ‘possible ACD / other cause’, 10.9% (6/64) had low red cell indices suggestive of co-existing iron deficiency. 23.4% (15/64) of patients in this category had a ferritin between µg/L with a normal CRP suggestive of either depleted iron stores (in the presence of chronic disease) or iron stores at the low end of normal which may become depleted with surgical blood loss. Within this category of patients where transferrin saturation (TSAT) was performed in addition to ferritin, 44% (11/25) had a TSAT <20% and serum ferritin µg/L consistent with ‘functional’ iron deficiency. Nearly half of patients in our cohort with IDA (10/21) received IV iron therapy in the preoperative period. A small proportion of the non-anaemic patients 6% (23/351) had serum ferritin <30 µg/L indicating deficient iron stores. Discussion One in five of all patients who underwent elective cardiac surgery had preoperative anaemia and approximately one third of patients with preoperative anaemia had iron deficiency or possible iron deficiency anaemia. Based on the template, 4 patients who were diagnosed with IDA in a previous admission and treated were misclassified as ‘possible ACD’ because of serum ferritin >100 µg/L (post treatment) and still being anaemic at pre operative assessment. 19 patients with serum ferritin between µg/L but with normal CRP are an important group with low or deficient iron stores that have the potential to be misclassified. History of chronic disease, red cell indices and blood film rather than CRP alone could help determine whether ferritin could be misleadingly elevated. 3 patients with serum ferritin between µg/L and 4 of patients with ‘possible ACD’ had low red cell indices (MCH <27 and/or MCV<80). Figure 1 Summary of patients classified by using preoperative haemoglobin assessment and optimisation template Table 2 Summary of patient characteristics including haemoglobin, red cell indices and ferritin at pre POAC, POAC and at discharge of IDA patients who received intravenous iron These patients with low or limited iron stores are likely to be rendered iron deficient post operatively and iron replacement should therefore be considered. Nearly one fourth of anaemic patients in our cohort were potentially able to be receive iron supplementation preoperatively to optimize haemoglobin stores to potentially reduce red cell transfusions. However, only roughly half received IV iron. Patients who received IV iron in an earlier admission (first 4 patients in red Table 2) prior to pre-operative assessment clinic (POAC) had an increment of g/l of haemoglobin and improved serum ferritin at POAC assessment. Patients who received IV iron after being diagnosed with IDA at POAC were also found to be anaemic in previous admission. The haemoglobin increment before surgery for these patients receiving IV iron could not be assessed due to non - availability of repeat haemoglobin (Hb) values immediately prior to surgery. There may have been an increase, but if not due to a short time to surgery, at least iron was available for post operative recovery of Hb levels. ACD or inflammation was the most common cause of preoperative anaemia in our cohort. Based on TSAT% 100 µg/L, a significant proportion of the patients (with ferritin >100 µg/L) fulfilled the definition of functional deficiency. Data on the role of pre-op IV iron this group is unclear but it may be of benefit in patients with chronic heart failure and chronic kidney disease based on studies outside the perioperative setting. Conclusion One fifth of patients undergoing elective cardiac surgery had preoperative anaemia, with almost a third having evidence of reversible iron deficiency. ‘Functional’ iron deficiency was also common. A previous admission leading up to surgery (eg. with an acute coronary syndrome) provides an important opportunity for early identification and treatment of anaemia, to help maximise response to therapy before surgery. The effect of haemoglobin optimization and/or iron repletion on transfusion and other important patient outcomes including mortality needs to be studied in cardiac surgical patients using well designed multicenter randomized controlled trials. IDA Patient Pre POAC Hb g/L POAC Interval between IV iron and date of surgery in weeks Discharge HbFerritin MCVMCH Hb Male, 82 y Male, 68y Female,71y Male, 74y Male,56y Male,74y Male,70y Male, 60y Female,75y Female,67y Pre-Operative Anaesthesia Clinic – POAC Patients Highlighted in Blue received preoperative intravenous Iron infusions