M. Muñoz, M. J. Laso-Morales, S. Gómez-Ramírez et al.
Anaesthesia 2017, 72, 826–834
Aim of study
To estimate of the prevalence of anaemia pre-operatively in patients having major elective surgery and identify main causes of this.
Design
Retrospective observational study of consecutive patients undergoing major elective surgery in 5 centres in Spain. (Jan 2008 – Dec 2014)
Methodology
3342 patients were scheduled for procedures in elective orthopaedic surgery, cardiac surgery, colorectal cancer resection, radical prostatectomy, gynaecological surgery and resection of liver metastases. Selection of procedures to include were those in which pre-operative anaemia was frequent due to underlying pathology, expected blood loss was >500ml and/or transfusion risk was >10%.
Anaemia was defined as Hb <130g/l. Absolute iron deficiency was defined as ferritin <30ng/ml (<100ng/ml, if transferrin saturation < 20% or C-reactive protein > 5 mg/l); iron sequestration as transferrin saturation <20% and ferritin >100 ng/ml; and low iron stores as transferrin saturation >20% and ferritin 30–100 ng/ml.
Statistics
Pearson’s chi-square test or Fisher’s exact test were used for comparison of qualitative variables, and unpaired Student’s t-test for comparison of quantitative variables, after testing for normality using the Kolmogorov–Smirnov test.
Results
The overall prevalence of anaemia was 36%. Laboratory results were available for 2884 patients to allow classification of iron status (including 1898 who were not anaemic). 62% of anaemic patients had absolute iron deficiency, 10% with iron sequestration and 5% with low iron stores. Corresponding figures for non-anaemic patients were 33%, 9% and 7%.
Conclusions/discussion
1/3 of analysed patients had pre-operative anaemia. 2/3 of these had absolute iron deficiency, for whom iron supplementation +/- erythropoietin were the suggested actions. Over half of those with Hb>130 had absolute iron deficiency or inadequate iron stores. Pre-operative anaemia screening and intervention were suggested to reduce transfusion requirements and improve outcome.
Women were included as anaemic for Hb<130, as the authors argued that they had lower circulating blood volumes, leading to higher proportional losses and thus transfusion. Also previous studies showed in orthopaedics and cardiac surgery that in comparison of 120 to 130 g/l, the lower limit led to increased complications.
Stated limitations from the study
No data available for clinical outcomes such as transfusion need, hospital length of stay, 30-90 day mortality.
There are peri-operative management differences between centres, ranging from oral/iv iron, erythropoietin, autologous blood donation, cell salvage to antifibrinolytics etc thus difficult to draw meaningful conclusions.
Discussion from journal club meeting
Pros:
Meta-analysis with a large number of patients and range of surgical procedures.
One would expect anaemic group to have iron deficiency but data says that one third of non-anaemic group also had absolute iron deficiency and another 27% had low iron stores. Therefore need to bear in mind potential need for iron top up if large estimated blood loss.
Cons:
Pre-operative anaemia in women is <120 according to WHO guidelines and thus in most epidemiological studies – as stated by authors themselves.
Did not measure blood loss and transfusion requirement from surgery, length of stay, mortality morbidity data
Unlikely to change practice in the UK – unlikely to be able to give EPO or screen for iron studies with Hb>120.
Current pre-assessment of patients too close to major surgery to have significant change if given iron pre-op – thus need to change whole pathway of pre-assessment
Summary by Dr T Mania and Dr PY Kuo. Journal Club 10 August 2017.
KingstonGasDocs 