Data from: Association between preoperative anaemia with length of hospital stay among patients undergoing primary total knee arthroplasty in Singapore: a single-centre retrospective study

OBJECTIVES: Studies in western healthcare settings suggest that
preoperative anaemia is associated with poor outcomes after elective
orthopaedic surgery. We investigated the prevalence of preoperative
anaemia among patients with primary unilateral total knee arthroplasty
(TKA) in Singapore and its association with length of hospital stay (LOS),
perioperative blood transfusion and hospital readmission rates. METHODS:
Retrospective cohort study performed in a tertiary academic medical centre
in Singapore, involving patients who underwent primary unilateral TKA
between January 2013 and June 2014. Demographics, comorbidities,
preoperative haemoglobin (Hb) level, LOS and 30-day readmission data were
collected. Anaemia was classified according to WHO definition. Prolonged
LOS was defined as more than 6 days, which corresponds to >75th
centile LOS of the data. RESULTS: We analysed 2394 patients. The
prevalence of anaemia was 23.7%. 403 patients (16.8%) had mild anaemia and
164 patients (6.8%) had moderate to severe anaemia. Overall mean LOS was
5.4±4.8 days. Based on multivariate logistic regression, preoperative
anaemia significantly increased LOS (mild anaemia, adjusted OR (aOR) 1.71,
p<0.001; moderate/severe anaemia, aOR 2.29, p<0.001).
Similar effects were seen when preoperative anaemia was defined by Hb
level below 13 g/dL, regardless of gender. Transfusion proportionately
increased prolonged LOS (1 unit: aOR 2.12, p=0.006; 2 or more units: aOR
6.71, p<0.001). Repeat operation during hospital stay, previous
cerebrovascular accidents, general anaesthesia and age >70 years
were associated with prolonged LOS. Our 30-day related readmission rate
was 1.7% (42) cases. CONCLUSION: Anaemia is common among patients
undergoing elective TKA in Singapore and is independently associated with
prolonged LOS and increased perioperative blood transfusion. We suggest
measures to correct anaemia prior to surgery, including the use of
non-gender-based Hb cut-off for establishing diagnosis.

研究目标：现有西方医疗体系中的研究表明，术前贫血与择期骨科手术后的不良预后密切相关。本研究旨在调查新加坡地区接受原发性单侧全膝关节置换术（total knee arthroplasty, TKA）患者的术前贫血患病率，并分析其与住院时长（length of hospital stay, LOS）、围术期输血率及30天住院再入院率的关联。研究方法：本研究为回顾性队列研究，于新加坡某三级学术医疗中心开展，纳入2013年1月至2014年6月期间接受原发性单侧全膝关节置换术的患者。收集患者的人口学特征、合并症、术前血红蛋白（haemoglobin, Hb）水平、住院时长及30天再入院数据。贫血依据世界卫生组织（World Health Organization, WHO）标准进行分类；延长住院时长定义为住院天数超过6天，即超出研究数据的第75百分位数。研究结果：本研究共纳入2394例患者，术前贫血患病率为23.7%。其中403例（16.8%）为轻度贫血，164例（6.8%）为中度至重度贫血。患者的平均住院时长为5.4±4.8天。多因素logistic回归分析显示，术前贫血可显著延长住院时长：轻度贫血的校正比值比（adjusted OR, aOR）为1.71，p<0.001；中重度贫血的aOR为2.29，p<0.001。当以不分性别的血红蛋白阈值<13g/dL定义术前贫血时，仍可观察到相似的关联结果。输血可显著增加住院时长延长的风险且呈剂量依赖性：输注1单位血液制品者aOR为2.12，p=0.006；输注2单位及以上者aOR为6.71，p<0.001。住院期间再次手术、既往脑血管意外病史、全身麻醉及年龄＞70岁均与住院时长延长相关。本研究的30天相关再入院率为1.7%（共42例）。研究结论：新加坡地区接受择期全膝关节置换术的患者中，贫血较为常见，且术前贫血与住院时长延长及围术期输血率升高存在独立关联。本研究建议在术前采取干预措施纠正贫血，包括采用不分性别的血红蛋白阈值作为贫血诊断标准。