Blood
Vol. 24 No 1 | Autumn 2022
Feature
Anaemia: often overlooked
Dr Ella Houston
BSc, MBBS (Hon); ANZCA Advanced Trainee

Perioperative anaemia is commonly encountered in patients undergoing major elective surgery with a reported prevalence of 30–60%. It is defined as a haemoglobin less than 130 g/L in males and less than 120 g/L in non-pregnant females. The early identification of anaemia is particularly relevant given its association with worse outcomes after surgery, including increased mortality, morbidity, allogeneic blood transfusion and longer length of stay.1 2 3 The aim of this article is to summarise major guidelines and recent literature on this topic with the hope it will provide the impetus to identify this at-risk cohort early, investigate and institute appropriate management.

Absolute and functional iron deficiency

The aetiology of anaemia in surgical patients is complex and often multi-factorial, which further complicates its diagnosis and management. The most common cause of anaemia is absolute iron deficiency, secondary to increased demand, decreased supply or increased loss. Another large subset of surgical patients exist in a state of chronic inflammation, resulting in functional iron deficiency or iron sequestration. In this setting, enteric iron is unable to be absorbed and body iron stores are inaccessible due to upregulation of the regulatory protein hepcidin. Distinguishing between the two is paramount, as although iron is necessary in both instances, intravenous iron to bypass the enteric route, often in combination with erythropoiesis stimulating agents, is required in the setting of inflammation. The key to diagnosing iron deficiency and distinguishing between absolute and functional iron deficiency lies in interpretation of iron studies.

Demystifying iron studies

In the first instance, interpretation of iron studies begins with assessment of ferritin levels. A ferritin level <30 μg/L is indicative of absolute iron deficiency, with a sensitivity and specificity of 92% and 98% respectively. Ferritin between 30–100 μg/L and either transferrin saturation <20% or CRP >5 mg/L is also suggestive of absolute iron deficiency. Ferritin >100 μg/L in combination with transferrin saturation <20% suggests functional iron deficiency, that is, the presence of adequate iron stores that are inaccessible to the body. In addition to investigation of the underlying cause, subsequent management of iron deficiency will depend on the urgency of surgery, tolerance and response to oral iron therapy.

What to do?

An international consensus statement on the management of perioperative anaemia and iron deficiency recommends a trial of oral iron with dietary advice in the first instance, if time to surgery is greater than 6–8 weeks, with reassessment of efficacy after 4 weeks. Conversely, administration of intravenous iron is recommended if non-deferrable surgery is scheduled within 6–8 weeks.4 Peak increase in haemoglobin after intravenous iron is anticipated at 3 weeks. Practice guidelines also recommend iron replacement in patients with suboptimal iron stores (ferritin <100 μg/L) if significant blood loss (>500 mL) is anticipated.5 In this setting, intraoperative blood loss culminating in a postoperative haemoglobin decrease of 30 g/L or greater would exhaust body iron stores. Importantly, in order to facilitate these recommendations, appropriate investigations must be ordered and reviewed when patients are initially booked for surgery including full blood count, iron studies, a measure of inflammation (eg. serum CRP) and renal function.

A spanner in the works

Recommendations from major guidelines have been described above; however, a discussion of anaemia and iron deficiency would not be complete without mention of the recently published Preoperative intravenous iron to treat anaemia before major abdominal surgery (PREVENTT) trial.6 This large multicentre randomised controlled trial was published in the Lancet in September 2020. It investigated the effect of administration of intravenous iron 10–42 days prior to major elective open abdominal surgery in patients with anaemia on the composite outcome of death or transfusion events 30 days postoperatively. In summary, there was no difference between the intervention and placebo group with respect to the primary outcome, despite a modest increase in haemoglobin preoperatively. Secondary endpoints suggested some benefits with respect to decreased readmissions for complications, which will be further investigated in a follow-up study. This trial suggests that a blanket approach to preoperative anaemia with administration of intravenous iron is not superior to placebo and advocates that tailored strategies aimed at treating the underlying cause may be more appropriate.

The big picture: Patient Blood Management

Investigation and correction of anaemia and iron deficiency is just one part of the broader picture of Patient Blood Management (PBM). PBM principles aim to reduce unnecessary administration of blood products and associated transfusion-related risks via adoption of a three-pillar approach. These three pillars apply throughout the perioperative journey and encompass optimisation of red cell mass (as outlined in this article), minimisation of blood loss and improving patient tolerance of anaemia.7 We all have a role to play in implementing these recommendations, from investigating and treating anaemia throughout the perioperative period, minimising blood loss with evidence-based intraoperative haemostatic techniques and by applying a considered approach to ordering of blood investigations, as well as adopting restrictive transfusion strategies. The perioperative period serves as an opportunity to identify and manage modifiable risk factors such as anaemia with the hope of improving patient-centred outcomes.

 

Our feature articles represent the views of our authors and do not necessarily represent the views of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG), who publish O&G Magazine. While we make every effort to ensure that the information we share is accurate, we welcome any comments, suggestions or correction of errors in our comments section below, or by emailing the editor at [email protected].

 

References

  1. Fowler AJ, Ahmad T, Phull MK, et al. Meta-analysis of the association between preoperative anaemia and mortality after surgery. Br J Surg. 2015;102:1314-24.
  2. Musallam KM, Tamim HM, Richards T, et al. Preoperative anaemia and postoperative outcomes in non-cardiac surgery: a retrospective cohort study. Lancet. 2011;378:1396-407.
  3. Baron DM, Hochrieser H, Posch M, et al. Preoperative anaemia is associated with poor clinical outcome in non-cardiac surgery patients. Br J Anaesth. 2014;113:416-23.
  4. Munoz M, Acheson AG, Auerbach M, et al. International consensus statement on the peri-operative management of anaemia and iron deficiency. Anaesthesia. 2017;72:233-47.
  5. National Blood Authority. Patient blood management guidelines: Module 2 Perioperative. National Blood Authority, Canberra, Australia. 2012. Available from: www.blood.gov.au/pbm-module-2.
  6. Richards T, Baikady RR, Clevenger B, et al. Preoperative intravenous iron to treat anaemia before major abdominal surgery (PREVENTT): a randomised, double-blind, controlled trial. Lancet. 2020;6736:1-9.
  7. National Blood Authority. Patient blood management guidelines: Module 2 Perioperative. National Blood Authority, Canberra, Australia. 2012. Available from: www.blood.gov.au/pbm-module-2.

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