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作者：Nancy Fowler Larson  
出處：WebMD醫學新聞

　　December 17, 2009 — 根據一項於12月17日線上發表在美國腎臟醫學會期刊的研究結果，住院時發生急性腎臟損傷（AKI）會增加出院後早期死亡風險，即使腎臟功能已經恢復。
　　
　　麻州Bedford Edith Nourse Rogers紀念退伍軍人醫院的Jean-Philippe Lafrance醫師與來自健康品質、預後暨經濟研究中心的Donald R. Miller博士寫到，過去探討AKI與死亡率的研究大多數僅檢驗住院死亡率，且並未提起出院後的發病與死亡率。檢驗出院後死亡率的研究主要針對需要透析的AKI重症病患；因此，不需要透析的AKI是否與所有原因死亡風險較高有關仍然未知。
　　
　　這項研究回溯性地分析82,711美國退伍軍人的數據，這些病患不需要透析，且在出院後至少存活90天以上。他們以多變項Cox迴歸模式校正流行病學、並存疾病、使用藥物、住院診斷、住院天數、是否使用呼吸器且估計離院後腎絲球廓清率（殘餘腎臟功能）來評估死亡風險。試驗前肌酐酸濃度，這些病患平均為3.5，在出院的時候下降到1.1。
　　
　　罹患AKI病患的死亡率顯著較高。在後續追蹤期間（平均時間為2.34±1.43年），150,231位病患死亡（17.4%）。AKI組的死亡粗累積風險為29.8%，沒有的AKI病患則是16.1%。
　　
　　然而，接連地將共變項加入模式中，降低死亡風險估計值，在完全校正模式中，AKI仍然與41%所有原因死亡率風險增加有關（校正危險比值[HR]為1.41；95%信賴區間[CI]為1.39-1.43）。作者們寫到，三種AKI分級之間發現存在風險梯度（校正危險比值為1.39相較於1.51以及1.71，對應到AKIN分級I、II、III相較於沒有AKI），AKI嚴重度與死亡風險上升有關（趨勢P值＜0.001）。就我們所知，這是第一項試著解開AKI與獨立於AKI造成腎臟功能短期喪失死亡率直接關係的研究。
　　
　　這項研究有許多限制，包括：
　　* 研究的現存數據並非根據特定目的收集
　　* 無法取得造成死亡的原因
　　* 用來評估AKI的血清肌酐酸濃度不完整
　　
　　除此之外，研究中僅有4.9%病患是女性。
　　
　　根據作者們表示，需要更長期與更詳盡的研究才能將這些發現應用於醫學上。
　　
　　作者們寫到，需要評估臨床病程（包括90天後腎臟功能變化）以及AKI病患出院後最佳治療的前瞻性研究來改善預後。
　　
　　退伍軍人研究經費贊助這項研究。Lafrance醫師接受KRESCENT獎學金，且Miller醫師接受來自Sanofi-Aventis的研究經費。


In-Hospital Kidney Injury Results in Increased Mortality After Discharge

By Nancy Fowler Larson
Medscape Medical News

December 17, 2009 — Experiencing acute kidney injury (AKI) while hospitalized increases the risk for early death after release, even if kidney function is restored, according to a study published online December 17 in the Journal of the American Society of Nephrology.

"The majority of previous studies linking AKI to mortality examined in-hospital mortality only and did not address post-discharge morbidity and mortality. Studies examining post-discharge mortality have focused primarily on critically ill patients with AKI that requires dialysis," write Jean-Philippe Lafrance, MD, and Donald R. Miller, ScD, from the Center for Health Quality, Outcomes, and Economic Research, and Edith Nourse Rogers Memorial Veterans Hospital, Bedford, Massachusetts. "Consequently, it remains unclear whether AKI that does not require dialysis is associated with a higher long-term risk for all-cause mortality."

The researchers retrospectively analyzed existing data regarding 82,711 US veterans whose AKI did not require dialysis and who survived at least 90 days after discharge. They evaluated mortality risks with multivariable Cox regression models adjusting for demographics, comorbidities, medications, admission diagnosis, number of days hospitalized, mechanical ventilation, and estimated glomerular filtration rate (residual kidney function) after leaving the hospital. Baseline creatinine values, a mean of 3.5 for each patient, had decreased to 1.1 at the time of hospital release.

The results showed a significant mortality increase among those with AKI. During follow-up (mean duration, 2.34 ± 1.43 years), 150,231 patients died (17.4%). The crude cumulative risk for death was 29.8% for the AKI group compared with just 16.1% for those who did not have AKI.

"Whereas each successive addition of covariates to the model reduced the mortality risk estimate, AKI remained associated with a 41% increased risk for all cause mortality in the fully adjusted model (adjusted [hazard ratio] 1.41; 95% confidence interval [CI] 1.39 to 1.43). A risk gradient was found among the three AKI categories (adjusted [hazard ratio] 1.39 versus 1.51 versus 1.71, for AKIN stages I, II, and III, respectively, compared with no AKI), with severity of AKI associated with increasing risk for death (P < 0.001 for trend)," the authors write. "To our knowledge, this is the first study to attempt to disentangle the direct association of AKI with mortality independent of the short-term loss of kidney function induced by AKI."

There were several limitations of the study, including that:

The existing data were not gathered for the specific purpose of this research,
The cause-of-death information was unavailable, and
The serum creatinine test information used to evaluate AKI was incomplete.
Furthermore, only 4.9% of patients studied were women.

More extensive and longer-term research is needed to use these findings in a medical setting, according to the authors.

"Prospective studies that evaluate the clinical course (including changes in kidney function after 90 [days]) and optimal treatment of patients discharged after AKI are needed to improve outcomes," the authors write.

A Veterans Affairs research grant supported this study. Dr. Lafrance is supported by a KRESCENT Fellowship, and Mr. Miller has received research grant funds from Sanofi-Aventis.

J Am Society Nephrol. Published online December 17, 2009.