The effects of preoperative moderate to severe anaemia on length of hospital stay A propensity score-matched analysis in non-cardiac surgery patients

BACKGROUND Anaemia is frequently recorded during preoperative screening and has been suggested to affect outcomes after surgery negatively. OBJECTIVES The objectives were to assess the frequency of moderate to severe anaemia and its association with length of hospital stay. DESIGN Post hoc analysis of the international observational prospective ‘Local ASsessment of VEntilatory management during General Anaesthesia for Surgery’ (LAS VEGAS) study. PATIENTS AND SETTING The current analysis included adult patients requiring general anaesthesia for non-cardiac surgery. Preoperative anaemia was defined as a haemoglobin concentration of 11 g dl^-1 or lower, thus including moderate and severe anaemia according to World Health Organisation criteria. MAIN OUTCOME MEASURES The primary outcome was length of hospital stay. Secondary outcomes included hospital mortality, intra-operative adverse events and postoperative pulmonary complications (PPCs). RESULTS Haemoglobin concentrations were available for 8264 of 9864 patients. Preoperative moderate to severe anaemia was present in 7.7% of patients. Multivariable analysis showed that preoperative moderate to severe anaemia was associated with an increased length of hospital stay with a mean difference of 1.3 ((95% CI 0.8 to 1.8) days; P < .001). In the propensity-matched analysis, this association remained present, median 4.0 [IQR 1.0 to 5.0] vs. 2.0 [IQR 0.0 to 5.0] days, P = .001. Multivariable analysis showed an increased in-hospital mortality (OR 2.9 (95% CI 1.1 to 7.5); P = .029), and higher incidences of intra-operative hypotension (36.3 vs. 25.3%; P < .001) and PPCs (17.1 vs. 10.5%; P = .001) in moderately to severely anaemic patients. However, this was not confirmed in the propensity score-matched analysis. CONCLUSIONS In this international cohort of non-cardiac surgical patients, preoperative moderate to severe anaemia was associated with a longer duration of hospital stay but not increased intra-operative complications, PPCs or in-hospital mortality.