Borderline anaemia and postoperative outcome in women undergoing major abdominal surgery: a retrospective cohort study

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.