第二節(jié) 腸內(nèi)營養(yǎng)的選擇

1、第二節(jié) 腸內(nèi)營養(yǎng)的選擇 進(jìn)行腸內(nèi)營養(yǎng)支持時(shí)，需根據(jù)預(yù)期營養(yǎng)支持的時(shí)間、腸道功能的受損程度、發(fā)生吸入性肺炎的危險(xiǎn)性及病人的病情和營養(yǎng)狀況，決定腸內(nèi)營養(yǎng)方式和制劑。 一、病人的選擇If the GI tract is functional, it should be used for enteral nutrition (EN), even if only a small amount can be tolerated. Oral intake is encouraged once a speech pathologist has determined the patient is no

2、t at high risk for aspiration. Nasoenteric devices, preferably postpyloric, are preferred if EN is not expected to persist past 30 days. Percutaneous gastrostomy or jejunostomy devices are placed if EN is expected beyond 30 days.一般認(rèn)為當(dāng)病人胃腸道功能不健全、不能吸收足夠的營養(yǎng)時(shí)，腸外營養(yǎng)能迅速補(bǔ)充營養(yǎng)，改善營養(yǎng)狀況，拯救病人的生命。但原則上講，只要病人胃腸道功能存在

3、或部分存在，并具有一定的吸收功能，就應(yīng)該首選腸內(nèi)營養(yǎng)。只有真性腸麻痹、機(jī)械性腸梗阻及嚴(yán)重腹腔感染時(shí)，才考慮采用腸外營養(yǎng)。 二、時(shí)機(jī)的選擇腸內(nèi)營養(yǎng)的時(shí)機(jī)選擇很重要。危重病人或嚴(yán)重創(chuàng)傷病人一旦血液動(dòng)力學(xué)穩(wěn)定，酸堿失衡和電解質(zhì)紊亂得到糾正，就應(yīng)立即開始腸內(nèi)營養(yǎng)。一般嚴(yán)重創(chuàng)傷后2448小時(shí)內(nèi)給予腸內(nèi)營養(yǎng)效果最佳。對于擇期手術(shù)的病人，如果存在營養(yǎng)不良，手術(shù)前就應(yīng)該采用腸內(nèi)營養(yǎng)，改善病人的營養(yǎng)狀況和免疫功能，提高手術(shù)耐受力，降低手術(shù)風(fēng)險(xiǎn)，減少手術(shù)并發(fā)癥。 三、置管方式的選擇Access routes for enteral feeding vary according to the individual

4、patient. In deciding which route to use, the anticipated length of feeding and the presence of delayed gastric emptying are two major considerations. Access to the GI tract via the nasal route such as nasogastric, nasoduodenal, or nasojejunal tubes are usually short term (less than 6-8 weeks). These

5、 tubes can be placed at the bedside. When enteral feeding is anticipated for a longer period of time an enterostomy tube should be considered. This is a more invasive category of enteral feeding where the tube accesses the GI tract through the abdominal wall. This procedure can be carried out in an

6、endoscopy unit, radiology department or in theatre.1. 對病人的損傷程度 損傷小、簡單安全是置管最重要的原則。目前臨床應(yīng)用最廣泛的是經(jīng)鼻置鼻胃管、鼻十二指腸管或鼻空腸管。對于有腸內(nèi)營養(yǎng)指征，上消化道無梗阻，營養(yǎng)支持后仍可恢復(fù)自然經(jīng)口進(jìn)食者，應(yīng)盡可能采用經(jīng)鼻置管。只有口、咽、鼻、食管梗阻或因疾病原因不能恢復(fù)經(jīng)口進(jìn)食，或雖然能恢復(fù)經(jīng)口進(jìn)食但需時(shí)較長、發(fā)生吸入性肺炎危險(xiǎn)性大的病人才考慮造瘺置管。2. 營養(yǎng)支持所需時(shí)間 需長期管飼者宜用胃造口或空腸造口置管，估計(jì)時(shí)間較短者宜采用經(jīng)鼻置管。時(shí)間長短受病人疾病、營養(yǎng)狀況、醫(yī)療監(jiān)護(hù)條件和所用鼻飼管質(zhì)地等影響

7、。3. 胃腸道功能 胃腸道功能受損程度影響腸內(nèi)營養(yǎng)方式的選擇，嚴(yán)重受損者不能應(yīng)用腸內(nèi)營養(yǎng)。胃腸功能差、需持續(xù)滴入營養(yǎng)液以及有較大誤吸危險(xiǎn)者，宜用胃或空腸造口置管。經(jīng)腹手術(shù)的病人，如營養(yǎng)狀況差、手術(shù)創(chuàng)傷重，或估計(jì)術(shù)后發(fā)生胰瘺、膽瘺、胃腸吻合口瘺等可能性大者，應(yīng)在術(shù)中作空腸造口置管，用于病人較長時(shí)間的營養(yǎng)支持。四、營養(yǎng)液輸注方法的選擇1. 營養(yǎng)液輸注時(shí)間的選擇 根據(jù)病人營養(yǎng)需要及其耐受程度而定。一般使用間歇輸注，病人可以有較大的活動(dòng)度，適用于胃腸道功能較好的病人。對于胃腸道功能差、嚴(yán)重營養(yǎng)不良、并發(fā)癥多、高應(yīng)激狀態(tài)或躁動(dòng)的病人，可以給予連續(xù)性輸注，一般為連續(xù)喂養(yǎng)20小時(shí)、間歇4小時(shí)，以讓消化系統(tǒng)有

8、足夠的時(shí)間休息。對于消化、吸收功能非常差或使用抑酸劑的病人甚至可以24小時(shí)持續(xù)喂養(yǎng)。The length of time which enteral feeding is given depends on the patient's needs and tolerance as well as local practices. If a patient requires full nutritional support it is usual to feed over about 20h with a 4-h rest period to allow the gastric acidi

9、ty to return to normal. If the patient is given antacids, the feeding can continue over 24h if required as the gastric acidity is already altered.2. 營養(yǎng)液輸注速度的選擇 病人由腸道曠置到重新耐受腸道內(nèi)營養(yǎng)物質(zhì)需要一段時(shí)間，因此剛開始輸注腸內(nèi)營養(yǎng)液時(shí)應(yīng)遵循低滲、少量、慢速的原則。一般間歇性輸注病人開始腸內(nèi)營養(yǎng)時(shí)，營養(yǎng)液的滴速宜控制在2550ml/h。如病人耐受，可每8小時(shí)增加2550ml，16小時(shí)后可增加100ml，24小時(shí)可增加150ml左右。如

10、病人不耐受，滴速增加的幅度應(yīng)減慢。連續(xù)性泵輸注的病人可勻速輸注，最初滴速亦為2550ml/h，每8小時(shí)增加2550ml，最終的平均滴速宜為100ml/h左右，最高可至200ml/h。調(diào)整滴速的依據(jù)是胃內(nèi)潴留物的檢查。If a patient has not been fed in the last 5 days, feedings should begin as low volume, continuous flow feedings in the range of 25 to 50ml/hour. Depending on the patient's tolerance, the r

11、ate can be titrated upward by 25ml every 8 to 12 hours. Residual volume in stomach should be monitored every 2 to 4 hours. If the patient is tolerating enteral feeding, the length of time that they are fed can be reduced, and the rate must increase to make sure all requirements are met. In situation

12、s where adult patients are well established on feeding, feeds can be administered at a rate of up to 200ml/h by pump or bolus. 五、營養(yǎng)制劑的選擇胃腸道功能良好者可用管飼滴注含完整蛋白的完全膳食，如勻漿膳、混合奶等，小兒可給予嬰兒膳。如果口咽無梗阻，經(jīng)一段時(shí)間管飼營養(yǎng)支持后病情緩解，可逐漸恢復(fù)自然飲食。但對口、咽、食管有梗阻，或因疾病、手術(shù)而吞咽功能受損者，則需長期管飼完全膳食。消化吸收功能較差者，可以采用要素制劑。詳見下一節(jié)。 六、能量、氮量及液體量的選擇Since

13、the loss of protein stores directly affects body function, it is important to administer sufficient amounts of energy and protein.1. 能量 腸內(nèi)營養(yǎng)支持的實(shí)施首先要確定病人的能量需要量。In the past, hyperalimentation (the delivery of energy in excess of requirements) was thought to be efficient in improving nutritional status

14、. However, hyperalimentation has been shown to induce severe metabolic abnormalities such as hyperglycemia, hyperlipidemia, and increased carbon dioxide production. Patients receiving nutritional support should be fed to their requirements.In clinical practice, selected methods for estimating basal

15、energy requirements are shown in Box . A frequently used simple guideline for estimating the daily energy needs of a patient is 25-35 kcal/kg body weight.Box Selected methods for estimating energy requirementsHarris-Benedict equation (estimates basal energy expenditure) Male:(13.75×W)+(5.0×

16、;H)+(6.76×A)+66.47 Female:(9.56×W)+(1.85×H)-(4.68×A)+655.1where W is weight in kilograms; H is height in centimeters; A is age in years.To predict total energy expenditure (TEE), add an injury/activity factor of 1.2-1.8 depending on the severity and nature of illness.Ireton-Jones

17、 energy expenditure equationsObesityIEE =606S+9W+12A+400V+1444 Spontaneously breathing patientsEEEs =629-11A+25W-609O Ventilator-dependent patientsEEEv =1925-10A+5W+281S+292T+8518 EEE is in kcal/day; subscript V indicates ventilator dependent; subscript S indicates spontaneously breathing.S: sex (ma

18、le=1, female=0)V: ventilator support (present=1, absent=0)T: diagnosis of trauma (present=1, absent=0)B: diagnosis of burn (present=1, absent=0)O: obesity > 30% above ideal body weight from 1959 Metropolitan Life Insurance tables (present=1, absent=0)In the clinical situation, additional disease-

19、associated factors should be taken into account during the calculation of the required energy needs. These include disease stress factor, activity factor, and temperature factor. Energy and nutrient losses from malabsorption should be taken into account when present.能量的供給并非多多益善，不僅要考慮病人的能量消耗，還要考慮病人的實(shí)

20、際代謝能力。1970年，Kinney和他的研究小組發(fā)現(xiàn)選擇性手術(shù)并不增加能量消耗，只有重大創(chuàng)傷或非常嚴(yán)重的敗血癥病人，其能量消耗會在一定時(shí)間內(nèi)增加20%40%。隨著護(hù)理和鎮(zhèn)痛技術(shù)的提高，與創(chuàng)傷有關(guān)的代謝負(fù)荷出現(xiàn)下降的趨勢。因此，病人的能量供給應(yīng)因人因時(shí)而異。對應(yīng)激期的病人，尤其是危重病人，能量補(bǔ)充宜維持體重而非增加體重，能量供給量應(yīng)以能維持能量代謝平衡、氮平衡為宜。而在恢復(fù)期則應(yīng)在能量消耗的基礎(chǔ)上，考慮合成代謝所需，以利于機(jī)體的修復(fù)。病人能量供給量包括基礎(chǔ)能量消耗、體力活動(dòng)消耗和疾病應(yīng)激時(shí)的能量消耗?？筛鶕?jù)Harris-Benedict公式確定BEE（見Box ）。再根據(jù)BEE、活動(dòng)系數(shù)、應(yīng)激

21、系數(shù)、體溫系數(shù)來確定總能量的消耗，即總能量需求BEE×活動(dòng)系數(shù)×應(yīng)激系數(shù)×體溫系數(shù)?；顒?dòng)系數(shù)：臥床為1.2，床邊活動(dòng)為1.25，正常輕度活動(dòng)為1.3。應(yīng)激系數(shù)見表9-2-1。體溫系數(shù)：正常時(shí)為1.0，每升高1增加消耗10%。表9-2-1不同疾病狀態(tài)下應(yīng)激系數(shù)疾病 應(yīng)激系數(shù) 疾病 應(yīng)激系數(shù) 中等程度饑餓 0.851.00嚴(yán)重感染或多發(fā)性創(chuàng)傷 1.301.55術(shù)后（無并發(fā)癥） 1.001.05燒傷（10%30%體表面積） 1.50癌癥 1.101.45燒傷（30%50%體表面積） 1.75腹膜炎 1.051.25燒傷（50%體表面積） 2.00長骨骨折 1.151.3

22、0  引自：臨床腸外與腸內(nèi)營養(yǎng)，蔣朱明、蔡威主編，2000年。際上，病人實(shí)際能量的消耗通常低于由經(jīng)典的公式計(jì)算出來的數(shù)值。大部分病人（包括ICU病人）的能量消耗一般不高于8.36MJ/d（2000kcal/d）。能量的計(jì)算還可按(105146kJ)2535kcal/kg估算。2. 蛋白質(zhì) 正常人每日蛋白質(zhì)的需要量一般為0.8g/kg。營養(yǎng)治療時(shí)為滿足蛋白質(zhì)需要可增至每日1.5g/kg，正常或輕度營養(yǎng)不良者按實(shí)際體重計(jì)，重度營養(yǎng)不良者按平時(shí)體重計(jì)，超重者則需按理想體重計(jì)。對于危重病人，能夠滿足蛋白質(zhì)合成需要、糾正負(fù)氮平衡的理想攝入量為1.51.7g/kg。由于高蛋白質(zhì)飲食會增

23、加肝、腎負(fù)擔(dān)，蛋白質(zhì)的攝入量不宜超過2.0g/kg。如以能量計(jì)算，每日蛋白質(zhì)攝入量應(yīng)占全天總能量的15%左右。另外，非蛋白質(zhì)能量與氮量之比（能氮比）以（627836kJ）150200kcal:1g較為合適。能量需要下降時(shí)，能氮比也應(yīng)下降。如病人需要較多蛋白質(zhì)，則能氮比需降至（418502kJ）100120kcal:1g才能滿足蛋白質(zhì)需要，肝衰、腎衰病人以（1.051.88MJ）250450kcal:1g為宜。Simply providing an excess of energy will not promote a positive N balance if the protein inta

24、ke is less than adequate. Whereas in the diseased patient protein synthesis can be stimulated by feeding, protein intake cannot influence whole body protein breakdown that occurs during inflammation.When protein accretion is the goal of nutritional therapy, the protein intake will have to be raised

25、to about 1.5g/kg per day. In severely ill patients and increased protein intake of 1.5-1.7g/kg body weight per day (normally 0.8g/kg body weight/day) optimally stimulates protein synthesis, resulting in the least negative nitrogen balance. Since there may be a diminished ability of the kidney and li

26、ver to tolerate a high amino acid load, the protein intake of patient should ideally not exceed 2 g/kg per day. Expressed as a percentage of the energy given, the protein intake should be about 15%.3. 液體量During disease, fluid and electrolyte balances can become disturbed. Overloading of fluids and electrolytes may impair gastric motility and delay the use of the enteral route for feeding. Flui