Supplementary Material for: Early Net Ultrafiltration during Continuous Renal Replacement Therapy: Impact of Admission Diagnosis and Association with Mortality.

Introduction: Continuous Renal Replacement Therapy (CRRT) is common in the Intensive Care Unit (ICU) but a high Net ultrafiltration rate (UFNET) calculated with daily data may increase mortality. We aimed to study early UFNET practice using minute-by-minute CRRT machine recordings and to assess its association with admission diagnosis and mortality. Methods: We studied CRRT treatments in three adult ICUs over 7-years. We calculated early UFNET rates minute-by-minute and categorised UFNET into tertiles of mean UFNET in the first 72 hours and admission diagnosis. We applied Cox-proportional hazards modelling with censoring of patients who died within 72 hours. Results: We studied 1218 patients; 154,712 hours and 9,282,729 minutes of CRRT (5,702 circuits). Mean early UFNET was 1.52 (1.46 to 1.57) mL/kg/hr. Early UFNET tertiles were similar to previously reported values at 0.00-1.20 mL/kg/hr, 1.21 to 1.93mL/kg/hr and >1.93mL/kg/hr. UFNET values were similar whether evaluated at 24 or 72 hours or for the entire duration of CRRT. There was, however, significant variation in UFNET practice by admission diagnosis: higher in respiratory diseases (pneumonia P=0.01, other P<0.0001), and cardiovascular disease (P=0.005) but lower in cardiothoracic surgery (P=0.04), renal (P=0.0003) and toxicology-associated diagnoses (P=0.01). Higher UFNET was associated with an increased hazard of death, HR 1.24 (1.13 to 1.37), independent of admission diagnosis, weight, age, sex, presence of ESKD and severity of illness. Conclusion: Early UFNET practice reflects known tertiles but varies significantly by admission diagnosis. Higher early UFNET is independently associated with mortality. Impacts of UFNET on mortality may vary by admission diagnosis. Further work is required to elucidate the nature and mechanisms responsible for this association.

引言：连续性肾脏替代治疗（CRRT）在重症监护病房（ICU）中应用广泛，但基于每日数据计算的高净超滤率（UFNET）可能会增加患者死亡率。本研究旨在通过逐分钟记录的CRRT机器数据，探究早期UFNET的临床实践情况，并评估其与入院诊断及患者死亡率的相关性。
方法：本研究纳入了7年间3家成人ICU的CRRT治疗数据。研究人员逐分钟计算早期UFNET速率，并根据患者前72小时的平均UFNET水平将其分为三分位组，同时按入院诊断进行分组。本研究采用Cox比例风险模型进行分析，并对72小时内死亡的患者进行删失处理。
结果：本研究共纳入1218例患者，累计CRRT治疗时长154712小时，共计9282729分钟，涉及5702条透析管路。早期UFNET的平均水平为1.52（95%置信区间：1.46~1.57）mL/kg/hr。早期UFNET的三分位分组区间与既往报道一致，分别为0.00~1.20 mL/kg/hr、1.21~1.93 mL/kg/hr以及>1.93 mL/kg/hr。无论在24小时、72小时还是整个CRRT治疗周期内评估，UFNET的数值均无显著差异。不过，不同入院诊断患者的UFNET实践存在显著差异：呼吸系统疾病（肺炎：P=0.01，其他呼吸系统疾病：P<0.0001）与心血管疾病患者的UFNET水平更高（P=0.005），而心胸外科术后、肾脏疾病及毒理学相关诊断患者的UFNET水平则较低（分别为P=0.04、P=0.0003及P=0.01）。较高的UFNET水平与死亡风险升高显著相关（风险比HR=1.24，95%置信区间：1.13~1.37），且该相关性不受入院诊断、体重、年龄、性别、是否合并终末期肾病（ESKD）以及疾病严重程度的影响。
结论：早期UFNET的临床实践水平符合既往报道的三分位分布特征，但不同入院诊断患者的UFNET水平存在显著差异。早期较高的UFNET水平与患者死亡率独立相关。UFNET对死亡率的影响可能因入院诊断的不同而存在差异，未来仍需进一步研究以阐明该关联的本质与潜在机制。