Preoperative fasting for adults to prevent perioperative complications

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Abstract
Fasting before general anaesthesia aims to reduce the volume and acidity of stomach contents during surgery, thus reducing the risk of regurgitation/aspiration. Recent guidelines have recommended a shift in fasting policy from the standard 'nil by mouth from midnight' approach to more relaxed policies which permit a period of restricted fluid intake up to a few hours before surgery. The evidence underpinning these guidelines however, was scattered across a range of journals, in a variety of languages, used a variety of outcome measures and methodologies to evaluate fasting regimens that differed in duration and the type and volume of intake permitted during a restricted fasting period. Practice has been slow to change. To systematically review the effect of different preoperative fasting regimens (duration, type and volume of permitted intake) on perioperative complications and patient wellbeing (including aspiration, regurgitation and related morbidity, thirst, hunger, pain, nausea, vomiting, anxiety) in different adult populations. Electronic databases, conference proceedings and reference lists from relevant articles were searched for studies of preoperative fasting in August 2003 and experts in the area were consulted. Randomised controlled trials which compared the effect on postoperative complications of different preoperative fasting regimens on adults were included. Details of the eligible studies were independently extracted by two reviewers and where relevant information was unavailable from the text attempts were made to contact the authors. Thirty eight randomised controlled comparisons (made within 22 trials) were identified. Most were based on 'healthy' adult participants who were not considered to be at increased risk of regurgitation or aspiration during anaesthesia. Few trials reported the incidence of aspiration/regurgitation or related morbidity but relied on indirect measures of patient safety i.e. intra‐operative gastric volume and pH. There was no evidence that the volume or pH of participants' gastric contents differed significantly depending on whether the groups were permitted a shortened preoperative fluid fast or continued a standard fast. Fluids evaluated included water, coffee, fruit juice, clear fluids and other drinks (e.g. isotonic drink, carbohydrate drink). Participants given a drink of water preoperatively were found to have a significantly lower volume of gastric contents than the groups that followed a standard fasting regimen. This difference was modest and clinically insignificant. There was no indication that the volume of fluid permitted during the preoperative period (i.e. low or high) resulted in a difference in outcomes from those participants that followed a standard fast. Few trials specifically investigated the preoperative fasting regimen for patient populations considered to be at increased risk during anaesthesia of regurgitation/aspiration and related morbidity. There was no evidence to suggest a shortened fluid fast results in an increased risk of aspiration, regurgitation or related morbidity compared with the standard 'nil by mouth from midnight' fasting policy. Permitting patients to drink water preoperatively resulted in significantly lower gastric volumes. Clinicians should be encouraged to appraise this evidence for themselves and when necessary adjust any remaining standard fasting policies (nil‐by‐mouth from midnight) for patients that are not considered 'at‐risk' during anaesthesia. 成年人術前禁食以預防手術過程併發症 全身麻醉前的禁食是為了減少手術中胃內消化物的體積和酸度,減低反胃/吸入異物的風險.新的治療準則建議改變過去‘午夜後不得經口飲食’的標準禁食策略,改為較不嚴格的策略:手術前數小時內可以飲用限量液體.有證據支持這些新準則.然而這些證據散佈在許多期刊中,且是用許多語言寫成,使用不同結果變數與方法學評估不同長度,種類的禁食和可食用不同份量的禁食策略.實務上並沒有馬上採用新準則. 系統性回顧不同術前禁食計畫(時間長短,可食用的食物種類和量)對不同成人病人族群的手術併發症和病人福祉(包含吸入異物,反胃和相關發病率,口渴,飢餓,疼痛,噁心,嘔吐,焦慮)的影響. 2003年八月搜尋電子資料庫,相關文章的會議資料和參考文獻清單.以尋找術前禁食相關文章.也諮詢本領域專家. 比較使用不同術前禁食方案,對成年病人術後併發症的隨機對照控制試驗 符合資格的研究細節由兩位檢閱者獨立擷取.若相關資訊闕如則連絡作者試圖取得. 找到三十八個隨機對照比較(於22個試驗中執行). 大部分對象都是健康成年受試者,麻醉過程不會增加反胃/吸入異物的風險.少數試驗結果由間接病人安全指標(如手術間胃容量和酸鹼值)得到反胃/吸入異物發生率或相關發病率.沒有證據證明術前禁食時間縮短組,和標準禁食組相比,兩組胃內消化物量或酸鹼值有顯著不同.研究包含以下液體:水,咖啡,果汁,清液和其他飲料(等滲透壓飲料和碳酸飲料). 術前有喝水的受試者,與標準禁食組相比,有顯著較少的胃內消化物量.此差異不大且臨床上不具顯著意義.術前容許飲用液體量不同的各組,和標準禁食組相比,結果並沒有顯著不同.在麻醉過程中,有些病人反胃/吸入異物的風險較高,相關發病率也較高.有一些試驗特別研究這些人對不同術前禁食計畫的反應. 沒有證據指出縮短液體禁食期間,與標準禁食策略‘午夜後不得經口飲食’相比,會增加反胃/吸入異物發生率或相關死亡率.在術前容許喝水,可顯著減少胃容量.應鼓勵醫生自行考量這個證據,在需要的時候對麻醉時沒有風險的病人,調整標準禁食策略:‘午夜後不得經口飲食’. Le jeûne...