風險指數評分表準確預測減肥手術後之死亡率


  May 2, 2007 —根據在美國科羅拉多州科泉市召開的美國外科協會年會所發表的多所醫學中心研究結果顯示,以5項醫療因子為基礎的簡易評分系統--肥胖手術死亡風險指數評分表(Obesity Surgery Mortality Risk Score,以下簡稱OS-MRS)能準確預測,可能是死亡風險最高的病態性肥胖患者中,誰該考慮接受胃繞道手術(gastric bypass surgery,以下簡稱GBS)。
  
  講演者及研究報告主筆北卡羅來納州達拉謨市杜克大學醫學中心一般外科教授Eric DeMaria醫師向WebMD表示,醫界認為減肥手術的整體風險相當低,但尚未有足夠的研究去將其風險分級,就我們所知,這項研究是率先獨立將胃繞道減肥手術的風險分級系統具體化。
  
  OS-MRS最初是由單一研究中心所進行研發,它並非於不同的數個研究中心在之前就制定成功;此評分系統對5項術前因子中的每一項設定為1分,包括身體質量指數(BMI)值高於50 kg/m2、男性、高血壓、肺栓塞的風險,以及年齡長於45歲;風險最低的A組,分數區間為0至1分,風險中等的B組,分數區間為2至3分,而風險最高的C組,分數區間為4至5分。
  
  在接受GBS的4,433名連續患者的有效群組中(這4,433名患者接受GBS的處所為南佛羅里達大學、南卡羅來納醫學大學及亞利桑那州Scottsdale市的一間私人診所),整體死亡率低於1%,而低風險群組的手術致死率約為0.3%,約僅有6名患者具有全部5項的風險因子。
  
  A、B、C這3組的死亡率,就數據上來看是完全不同的(P < .05),B組的死亡率是A組的3倍,C組的死亡率是A組是的6倍,儘管C組的患者僅佔總群組(n = 125)的3%,C組患者的死亡率卻超出比例,佔了總死亡率的8%。
  
  美國減肥手術學會主席Philip Schauer醫師向WebMD表示,減肥手術的死亡風險,與患者本身及患者上手術台身上所帶的風險因子,有高度相關;Schauer醫師並未參與該研究,但被諮詢以提供獨立公正的意見。
  
  Schauer醫師表示,預測死亡率的5大風險因子:隨著年齡而變高,特別是超過45歲、隨著BMI值而變高、男性、有肺栓塞的風險因子、共存疾病,這並非石破天驚的新知,此研究的貢獻在於發展出這套風險指數評分表,讓患者及醫師對手術預作判定。
  
  根據Schauer醫師(他亦為俄亥俄州克里夫蘭醫療機構肥胖及代謝研究中心主任)的說法,本研究的的限制在於統計上的數據不夠確實,而無法標示出其他的預測因子,像是小型的硬化發生。
  
  DeMaria醫師表示,病態性肥胖的時期愈長,手術的風險就愈高,因此,病態性肥胖患者更不應延遲接受唯一已知有益的胃繞道減肥手術;手術的風險亦會隨著BMI值而變高,因此減重方法是降低風險的可能性措施,這些方法可能有些要開刀,例如在最後的手術完成前,以減重為輔助的分段手術程序。
  
  根據Schauer醫師的說法,其他術前措施也可能有助於降低風險,其中包括血壓控制最佳化。
  
  Schauer醫師總結指出,即使是對那些手術死亡率風險較其他人高的患者,手術或許仍是最佳選項,因為嚴重肥胖的死亡率風險,遠比手術所帶來的風險還要來得高;大多數研究顯示,減肥手術後5至7年的死亡率風險,降低了50%至70%,因此它相當值得。
  
  DeMaria醫師的研究團隊正計畫採用取自美國減肥手術學會每年約100,000名患者的資料,對其風險指數評分系統之有效性,進行預測性的評估。
  
  執筆人總結表示,OS-MRS是對減肥手術的第一項具體風險指數評分系統,預期能有助於告知後同意、輔助手術決策,並讓不同的醫學中心之間能有手術結果比對的基準。
  
  DeMaria和Schauer兩位醫師和此議題皆無直接相關的財務關聯。
  
  美國外科協會2007年會。2007年4月26日發表。

Risk Score Accurately Predicts

By Laurie Barclay, MD
Medscape Medical News

May 2, 2007 — The Obesity Surgery Mortality Risk Score (OS-MRS), a simple scoring system based on 5 medical factors, accurately predicts which patients being considered for gastric bypass surgery (GBS) for morbid obesity would be at highest risk for dying, according to the results of a multicenter study presented at the American Surgical Association annual meeting in Colorado Springs, Colorado.

"We know that the risk of bariatric surgery is very low overall, but not many studies have been done to stratify that risk," presenter and lead author Eric DeMaria, MD, a professor of general surgery at Duke University Medical Center in Durham, North Carolina, told Medscape. "This is the first study we know of that has independently validated a risk stratification system for bariatric surgery."

The OS-MRS was originally developed from a single institution, but it was not previously validated at different institutions. This scoring system assigns 1 point to each of 5 preoperative factors, including body mass index (BMI) higher than 50 kg/m2, male sex, hypertension, risk for pulmonary embolism, and age older than 45 years. Lowest risk (class A) is a score of 0 to 1, intermediate risk (class B) is a score of 2 to 3, and high risk (class C) is a score of 4 to 5.

In a validation cohort of 4433 consecutive patients undergoing GBS at the University of South Florida, the Medical University of South Carolina, and a private practice in Scottsdale, Arizona, overall mortality was less than 1%, and the risk for surgical mortality in the low-risk group was about 0.3%. There were only 6 patients who had all 5 risk factors.

Mortality in classes A, B, and C was statistically different from each of the other 2 classes (P <  .05), with mortality 3-fold greater in class B than in class A, and mortality 6-fold greater in class C  than in class A. Although class C patients made up only 3% of the total cohort (n = 125), they accounted for a disproportionate 8% of all mortalities.

"The mortality risk of a bariatric procedure is highly dependent on the patient and on the risk factors the patient brings to the operating table," Philip Schauer, MD, president of the American Society for Bariatric Surgery, told Medscape. Dr. Schauer was not involved in this study but was asked to provide independent commentary.

"Five major risk factors predict mortality: increased age, especially after age 45; increased BMI; male gender; risk factors for pulmonary thrombosis; and comorbid conditions," Dr. Schauer said. "This is not earth-shattering news, but the contribution of this study is developing this score to allow patients and doctors to develop prognosticators of surgery risk."

According to Dr. Schauer, who is also director of the Bariatric and Metabolic Institute at the Cleveland Clinic in Ohio, limitations of this study include insufficient statistical power to identify other predictors such as cirrhosis, despite the large sample size.

"The risk of surgery increases with the duration of morbid obesity, so patients who suffer from this often lifelong condition should not delay the only intervention known to help, namely bariatric surgery," Dr. DeMaria said. "The risk of surgery also increases with BMI, so weight reduction strategies are possible interventions that may reduce risk. Some of these strategies may be surgical, for example, staged surgical procedures that assist with weight loss before definitive surgery is done."

Other preoperative strategies that may help minimize risk, according to Dr. Schauer, include optimizing blood pressure control.

"Even for patients who are at higher risk for mortality from surgery than are other patients, surgery may still be the best option, because the mortality risk of severe obesity is much higher than that of the surgery," Dr. Schauer concluded. "Most studies show that by 5 to 7 years after bariatric surgery, mortality risk declines by 50% to 70%, so it's a very good tradeoff."

Dr. DeMaria's group is planning a prospective assessment of the validity of their scoring system, using data collected from approximately 100,000 patients per year through the American Society for Bariatric Surgery.

"OS-MRS is the first validated risk scoring system in bariatric surgery and is anticipated to aid informed consent, assist surgical decision-making, and allow standardization of outcome comparisons between centers," the authors conclude.

Drs. DeMaria and Schauer report no relevant financial relationships directly related to this topic.

American Surgical Association 2007 Annual Meeting. Presented April 26, 2007.


    
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