Background

One in two adults undergoing cardiac surgery are iron deficient, best practice guidelines and consensus statements recommend routine investigation and treatment of iron deficiency before elective cardiac surgery, even in the absence of anaemia; however, it is not clear if non-anaemic iron deficiency is associated with worse outcomes in this patient population. We hypothesised that iron deficiency would be associated with worse postoperative outcomes than an iron replete state in adults without anaemia undergoing elective cardiac surgery.

Methods

We performed a prospective, cohort study at two hospitals in Australia. We recruited adults (ie, people 18 years and older) undergoing elective cardiac surgery without anaemia (defined as a haemoglobin of less than 130 g/L for men and less than 120 g/L for women), concomitant haemoglobinopathy, bone marrow pathology, haemochromatosis, or end-stage renal failure requiring dialysis. Participants were stratified as iron deficient or iron replete on the basis of preoperative testing. Iron deficiency was defined as a serum ferritin of less than 100 μg/L or 100–300 μg/L if transferrin saturation was less than 20% or C-reactive protein was more than 5 mg/L. The primary endpoint was days alive and at home at postoperative day 30. The primary analysis included all patients with data available for the primary endpoint and was adjusted for risk measured using EuroSCORE-II and body surface area. The study was prospectively registered with the Australian and New Zealand Clinical Trials Registry, ACTRN12618000185268.

Findings

We conducted the study between Feb 21, 2018, and May 7, 2021. We assessed 1171 patients for eligibility and 691 were ineligible; therefore, we enrolled and followed up 480 participants. 240 (50%) were iron deficient and 240 (50%) were iron replete, 95 (20%) were women, 385 (80%) were men, and 453 (94%) were White. Complete data was available for 479 individuals (240 in the iron deficient group and 239 in the iron replete group) for the primary endpoint. The iron deficient group had a median of 22·87 days (IQR 20·65 to 24·06) alive and at home at postoperative day 30, and the iron replete group had a median of 23·18 days (IQR 20·69 to 24·70). The unadjusted difference in medians between the groups was −0·18 days (95% CI −0·73 to 0·36; p=0·51) and the adjusted difference in medians between the groups was −0·11 days (95% CI −0·66 to 0·45; p=0·70).

Interpretation

In non-anaemic adults undergoing elective cardiac surgery, our findings suggest that patients with iron deficiency do not have a reduction in days alive and at home at postoperative day 30 compared with patients who have a normal iron status. Routine preoperative investigation for iron deficiency in patients without anaemia undergoing elective cardiac surgery using the definitions we tested might be low-value care.

Funding

Australian and New Zealand College of Anaesthetists Foundation.

中文翻译：

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非贫血性缺铁与择期心脏手术 (IDOCS) 后结局之间的关联：一项前瞻性队列研究

背景

接受心脏手术的成年人中有二分之一缺铁，最佳实践指南和共识声明建议在择期心脏手术前对缺铁进行常规检查和治疗，即使没有贫血；然而，尚不清楚非贫血性缺铁是否与该患者群体的不良预后相关。我们假设在接受择期心脏手术的没有贫血的成人中，与铁充足状态相比，缺铁与更差的术后结果相关。

方法

我们在澳大利亚的两家医院进行了一项前瞻性队列研究。我们招募了接受择期心脏手术的成年人（即 18 岁及以上的人），没有贫血（定义为男性血红蛋白低于 130 g/L，女性低于 120 g/L）、伴随的血红蛋白病、骨髓病理学、血色素沉着症或需要透析的终末期肾功能衰竭。根据术前测试，参与者被分为缺铁或缺铁。如果转铁蛋白饱和度低于 20% 或 C 反应蛋白高于 5 mg/L，则铁缺乏定义为血清铁蛋白低于 100 μg/L 或 100-300 μg/L。主要终点是术后第 30 天的存活天数和在家中的天数。主要分析包括所有具有主要终点可用数据的患者，并针对使用 EuroSCORE-II 和体表面积测量的风险进行了调整。该研究在澳大利亚和新西兰临床试验注册处进行了前瞻性注册，ACTRN12618000185268。

发现

我们在 2018 年 2 月 21 日至 2021 年 5 月 7 日期间进行了这项研究。我们评估了 1171 名患者的资格，691 名不符合资格；因此，我们招募并跟踪了 480 名参与者。240 人（50%）缺铁，240 人（50%）缺铁，95 人（20%）女性，385 人（80%）男性，453 人（94%）白人。主要终点有 479 人（缺铁组 240 人，缺铁组 239 人）的完整数据。缺铁组术后第 30 天在家中生存和在家的中位时间为 22·87 天（IQR 20·65 至 24·06），铁充足组的中位时间为 23·18 天（IQR 20·69 至24·70)。组间未调整的中位数差异为 -0·18 天（95% CI -0·73 至 0·36；p=0·51），组间调整后的中位数差异为 -0·11 天（95 % CI -0·66 至 0·45；p=0·70)。

解释

在接受择期心脏手术的非贫血成人中，我们的研究结果表明，与铁状态正常的患者相比，缺铁患者术后第 30 天的存活天数和在家中的天数并未减少。使用我们测试的定义对接受择期心脏手术的无贫血患者进行常规术前检查可能是低价值的护理。

资金

澳大利亚和新西兰麻醉师学院基金会。