Preoperative anaemia in elective surgery with bleeding risk

Discussion

Preoperative anaemia was identified in 34 % of patients scheduled for elective surgery with an estimated risk of blood loss exceeding 500 mL. Our findings were consistent with the reported prevalence of preoperative anaemia in large-scale European studies. An Austrian study reported a prevalence of 33 % in a mixed surgical population including 6908 patients (3), while a Spanish multicentre study involving 3342 patients reported a prevalence of 36 % (4).

The aetiology of anaemia is often multifactorial and may reflect underlying serious disease rather than an isolated, modifiable risk factor. Iron deficiency, however, is the most common cause of anaemia in the surgical population and is particularly relevant prior to planned surgery where there is a risk of significant bleeding and additional iron loss (4, 5). Although bleeding, and thus iron deficiency anaemia, may be prevalent among patients with various pathologies scheduled for surgery (such as uterine fibroids, bladder cancer and colorectal cancer), measurement of ferritin and administration of intravenous iron were only standardised in the colorectal cancer group in our population (a subgroup of the gastrointestinal surgery group). Ferritin is often included in an 'anaemia blood test panel', which typically also comprises several iron parameters as well as vitamin B12 and folate levels. In the specialist health service, ferritin was measured in a total of 17 % of patients. Ferritin may have been measured in primary care prior to referral for surgery; nevertheless, assessment of preoperative iron stores is clinically relevant. Measurement of ferritin is recommended in international guidelines for preoperative anaemia, both for diagnostic purposes and to stratify patients who may benefit from iron therapy (6, 10, 19). For each millilitre of blood lost, approximately 0.5 mg of iron is lost, and iron is required for efficient production of new blood cells following surgery (20).

The surgical procedures we included carry a moderate risk of bleeding, unlike high-risk procedures such as vascular or thoracic surgery, which are performed at larger hospitals (10, 17). Unfortunately, we do not have data on the actual blood loss in our cohort. In our view, there is a lack of national, validated overviews defining 'surgery with bleeding risk'. In our internal quality registry, 96 % of patients had pre-transfusion blood tests, in line with the Norwegian version of the Choosing Wisely initiative (Gjør Kloke Valg), which states that 'preoperative transfusion testing should only be ordered for operations where blood transfusions are often indicated' (21). However, haemoglobin was not measured preoperatively in 29 % of urological patients; the urology department will therefore review its procedures for preoperative testing.

Overall, 29/293 (10 %) patients received red blood cell transfusions, with a median haemoglobin level prior to transfusion of 8.1 g/dL, reflecting good adherence to restrictive transfusion thresholds. In practice, however, restrictive transfusion thresholds appear to have resulted in an 'untreated anaemic interval', in which patients not receiving transfusions are often not offered alternative treatment. According to international guidelines, patients with severe, moderate or mild anaemia should be offered treatment that optimises their own blood, regardless of transfusion indication (13, 19).

International guidelines provide specific recommendations on how to manage anaemia in the perioperative period (9, 10, 19), but there are no equivalent Norwegian guidelines. The Norwegian Society for Immunology and Transfusion Medicine notes in Choosing Wisely (Gjør kloke valg) that transfusion should be 'avoided as a treatment for iron deficiency anaemia' (22). Haemoglobin levels should, for example, be checked at the time of referral for surgery. If iron deficiency anaemia is identified, treatment should be initiated in primary care, and the sooner, the better. This includes supplementation with vitamin B12, folate or iron.

In most patients with iron deficiency anaemia, oral iron therapy can initially be attempted, provided the anaemia is mild (haemoglobin > 11 g/dL) and there is sufficient time (months) before the planned surgical procedure. If the patient does not achieve an adequate increase in iron stores and haemoglobin, or if surgery that should not be postponed is only weeks away, intravenous high-dose iron therapy should be considered (19). Patients with chronic inflammation will also yield less benefit from oral supplementation due to reduced iron absorption, and erythropoietin therapy is recommended for a small subgroup of patients.

Limitations of the study were the retrospective collection of data from a local hospital, the inclusion of only 293 patients over a six-month period, and the small number of patients in each surgical category. We did not examine precise ferritin levels or other laboratory measurements used in anaemia evaluation. Ferritin and haemoglobin levels may also have been measured for reasons other than preoperative assessment, as we included laboratory results up to three months before surgery. The list of surgical procedures expected to involve blood loss > 500 mL was not based on validated assessments, and we lacked data on both the actual intraoperative blood loss and postoperative haemoglobin levels. We did not investigate complications associated with preoperative anaemia; however, a number of studies have reported on this (1–3).