Critical Care - Research Publications
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ItemA protocol for prospective observational study to determine if non-anaemic iron deficiency worsens postoperative outcome in adult patients undergoing elective cardiac surgery: the IDOCS study(BMC, 2022-02-08)BACKGROUND: Pre-operative anaemia has been associated independently with worse outcomes after cardiac surgery in adults and is often caused by absolute or functional iron deficiency. Iron deficiency is a continuum ending with anaemia, and therefore it is plausible that pre-operative early or 'non-anaemic' iron deficiency may also be associated with worse outcomes in patients undergoing cardiac surgery. METHODS: We have designed a prospective, observational study to determine if there is an association between non-anaemic iron deficiency and worse outcomes after cardiac surgery in adults. Patients without anaemia undergoing elective cardiac surgery will be allocated to an iron-deficient and an iron-replete group based on standard pre-operative blood tests (ferritin, transferrin saturation and C-reactive protein). The primary outcome is days alive and at home on postoperative day 30. The key secondary outcomes are days alive and at home on postoperative day 90 and readmission to acute care. Other secondary outcomes include health-related quality of life questionnaires, quality of postoperative recovery, postoperative complications, changes in haemoglobin concentration, and requirement for allogeneic blood products. The planned study sample size is 240 patients per group, which has 83% power to detect a median difference of 1.25 days in the primary outcome. The study commenced in March 2018, and recently completed recruitment, with data audit and cleaning ongoing. DISCUSSION: This study will be conducted using a rigorous, prospective observational design; it will provide peak bodies and clinicians with high-quality evidence concerning the associations between non-anaemic iron deficiency and patient-centred outcomes after elective cardiac surgery. Our primary and key secondary outcomes are known to have great importance to clinicians and patients alike and align with the recommendations of the StEP-COMPAC group for outcomes in prospective peri-operative research. The definition used for iron deficiency accounts for both absolute and functional iron deficiency and make use of standard pre-operative blood tests to make this determination, easing the transition of results into clinical practice. The study will be conducted in two relatively high-volume centres in a single high-income country. This limits the generalisability of study results to similar centres. TRIAL REGISTRATION: Australian and New Zealand Clinical Trials Registry ( ACTRN12618000185268 ). Registered 5 February 2018.
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ItemPostoperative outcomes following cardiac surgery in non-anaemic iron-replete and iron-deficient patients - an exploratory study(WILEY, 2018-04)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-1 . 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.
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ItemPeri-operative correction of non-anaemic iron deficiency(WILEY, 2017-07)
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ItemSelecting and optimising patients for total knee arthroplasty(WILEY, 2019-09)
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ItemAssociations between preoperative anaemia and hospital costs following major abdominal surgery: cohort study(OXFORD UNIV PRESS, 2021-03)BACKGROUND: Determining the cost-effectiveness and sustainability of patient blood management programmes relies on quantifying the economic burden of preoperative anaemia. This retrospective cohort study aimed to evaluate the hospital costs attributable to preoperative anaemia in patients undergoing major abdominal surgery. METHODS: Patients who underwent major abdominal surgery between 2010 and 2018 were included. The association between preoperative patient haemoglobin (Hb) concentration and hospital costs was evaluated by curve estimation based on the least-square method. The in-hospital cost of index admission was calculated using an activity-based costing methodology. Multivariable regression analysis and propensity score matching were used to estimate the effects of Hb concentration on variables related directly to hospital costs. RESULTS: A total of 1286 patients were included. The median overall cost was US $18 476 (i.q.r.13 784-27 880), and 568 patients (44.2 per cent) had a Hb level below 13.0 g/dl. Patients with a preoperative Hb level below 9.0 g/dl had total hospital costs that were 50.6 (95 per cent c.i. 14.1 to 98.9) per cent higher than those for patients with a preoperative Hb level of 9.0-13.0 g/dl (P < 0.001), 72.5 (30.6 to 128.0) per cent higher than costs for patients with a Hb concentration of 13.1-15.0 g/dl (P < 0.001), and 62.4 (21.8 to 116.7) per cent higher than those for patients with a Hb level greater than 15.0 g/dl (P < 0.001). Multivariable general linear modelling showed that packed red blood cell (PRBC) transfusions were a principal cost driver in patients with a Hb concentration below 9.0 g/dl. CONCLUSION: Patients with the lowest Hb concentration incurred the highest hospital costs, which were strongly associated with increased PRBC transfusions. Costs and possible complications may be decreased by treating preoperative anaemia, particularly more severe anaemia.
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ItemBorderline anaemia and postoperative outcome in women undergoing major abdominal surgery: a retrospective cohort study(WILEY, 2020-02)Pre-operative anaemia is typically diagnosed with a haemoglobin concentration < 120 g.l-1 for women and < 130 g.l-1 for men on the basis of limited evidence. This retrospective cohort study stratified women undergoing elective, major abdominal surgery based on pre-operative haemoglobin concentration: anaemic (< 120 g.l-1 ); borderline anaemic (120-129 g.l-1 ); and non-anaemic (> 130 g.l-1 ). Data from 1554 women were analysed. Women with borderline anaemia had a greater incidence of postoperative complications (55 (16%) vs. 110 (11%); p = 0.026), longer duration of hospital stay (median (IQR [range]) 3 (1-6 [0-69]) days vs. 2 (1-5 [0-80]) days; p = 0.017) and fewer days alive and out of hospital at postoperative day 30 (median (IQR [range]) 27 (23-29 [0-30]) vs. 28 (25-29 [0-30]) days; p = 0.017) compared with non-anaemic women. However, after matched cohort analysis, these outcome differences no longer remained statistically significant. After multivariable adjustment for procedure, Charlson comorbidity index and patient age, a negative relationship between logarithmic pre-operative haemoglobin concentration and duration of stay was found (parameter estimate (standard error) -0.006 (0.003) vs. 0.003 (0.003) for a haemoglobin concentration < 130 g.l-1 vs. > 130 g.l-1 , respectively; p = 0.03); the difference in duration of stay was approximately 50% greater for women with a haemoglobin concentration of 120 g.l-1 compared with those with a haemoglobin concentration of 130 g.l-1 . Although the contribution of borderline anaemia to the incidence of postoperative complications is uncertain, the current diagnostic criteria should be re-assessed.