DOI: 10.1097/TA.0000000000003326
Journal of Trauma and Acute Care Surgery
2021年6月22日Online
A. 营养风险与需求评估
时机：
After initial resuscitation, consideration of early (within 24-48 hours of admission) nutrition therapy should begin.
多发伤及合并症人群稍显复杂，可考虑早期请营养科介入：
Provision of nutrition therapy may be particularly complex in patients with polytrauma and/or pre-existing comorbidities. Depending on the experience of the treating team, early consultation with a nutrition support team or registered dietitian should be considered, which has been shown to improve outcomes in some cohorts of patients.
The determination of malnutrition remains an area of international discussion and research without definitive definitions or scoring systems. Despite this, there is consensus that objective criteria such as body mass index (BMI) and a detailed history of recent volitional intake or weight loss are predictors of nutritional risk and post-surgical complications and should be used to help stratify patients as “high” or “low” risk. An initial assessment of malnutrition should be completed utilizing validated scoring systems such as the Nutrition Risk Assessment (NRS 2002) or Nutrition Risk in Critically Ill (NUTRIC). The determination of baseline nutritional risk guides the initial prescription for nutrition therapy including total energy and protein goals.
低至中危营养风险创伤患者的初始热卡要求：
For patients determined to have low or moderate nutritional risk, begin nutrition support at 70% of energy goals corresponding to 15 to 20 kcal/kg/day over the initial 1 to 4 days following ICU admission. Limiting energy delivery to not greater than 70% of resting energy expenditure when initiating feeding early in critical illness or injury has demonstrated the lowest 60-day mortality compared to feeding at higher amounts of energy. However, for patients determined to be at high risk of malnutrition the progression to protein and energy goals should be more aggressive（高危风险者蛋白和热卡目标要更加积极）.
For energy and protein estimations, we suggest using actual body weight（用实际体重） if BMI is <30kg/m2 or a BMI of 25kg/m2 if actual body weight is >BMI of 30kg/m2. Protein goals are calculated exclusive of total kcal needs; that is, total protein should be administered in addition to minimum kcal goals such that protein does not constitute all or most of the total kcal.
蛋白目标：Minimum protein needs should be estimated at least 1.2gm/kg/day to 1.3gm/kg/day and increased up to 2gm/kg/day protein or higher in polytrauma or burn patients.
烧伤患者：Additionally, burn patients with 40% total body surface area or greater affected require at least 25 kcal/kg/day plus 40 kcal per percent total body surface area burn per day.
With appropriate monitoring for refeeding syndrome, no less than 80% of energy and protein goals should be achieved within 48 to 72 h of ICU admission when possible. A minimum of 1.5g/kg/day of protein and 25-30kcal/kg/day should be initiated. Caution must be exercised, however, when initiating nutrition in patients at risk for malnutrition and they must be monitored for the development of refeeding syndrome (RS)（仔细监测再喂养综合征）. RS is defined as the constellation of metabolic and electrolyte disturbances resulting from rapid reintroduction of protein and energy to a patient after a prolonged period of decreased or absent intake. Hypophosphatemia is the traditional hallmark of RS and frequent measurement of electrolyte panels is paramount in patients at risk for RS to prevent life threatening complications from these derangements. Those patients most likely to be at risk for RS includes those with a history of anorexia nervosa, bariatric or extensive bowel resection surgery, alcohol and substance use disorder, diseases associated with malabsorption (eg, celiac), some mental health diagnoses, malignancy, and in patients whose social situation places them at risk for food insecurity（再喂养综合征的高危因素）.
B. 肠内vs肠外营养的决策
Once a nutritional risk and needs assessment has been completed, the route of nutrition delivery must be decided. Enteral nutrition (EN) is nearly always preferred to parenteral nutrition (PN) and should be started after resuscitation goals have been met (eg, normal or down trending lactate level, no longer needing large volume fluid or blood product resuscitation, adequate urine output, etc) so long as there are no contraindications. If vasopressor support continues to be required despite adequate resuscitation, EN can be initiated when the vasopressor dose is deescalating or stable（即便是有升压药）. The need for ongoing vasopressor support is not an absolute contraindication to the initiation of EN or an indication for PN（升压药并非绝对禁忌症）.
There are relatively fewer contraindications to EN than historically believed and we advocate for a trial of EN in most patients including those with an open abdomen after damage control laparotomy, newly created ostomy, those who require prone positioning neuromuscular blockade infusions, and in patients with traumatic brain injury (TBI). Previous studies have not only shown EN to be safe, but even advantageous for these patients. Specifically, patients with an open abdomen who receive EN derive benefits such as fewer overall complications, earlier fascial closure, and decreased mortality. Additionally, early EN has been demonstrated to reduce length of hospital stay in TBI patient and is associated with improved survival and Glasgow Coma Score (GCS) recovery.
Contraindications to the use of EN（肠内营养明确的禁忌症） include intestinal obstruction (eg, extrinsic compression from hematoma, adhesions, anastomotic stricture, etc), intestinal discontinuity after damage control laparotomy, high-output enterocutaneous fistula, high dose vasopressor requirements, intestinal ischemia, or documented intolerance (discussed below in Section D) to trials of EN. If a patient has these contraindications, consideration should be
given to the initiation of PN.
C. 启动肠内营养
Once the decision has been made to start EN, gastric access should be established and confirmed by radiograph. It is acceptable, and likely faster, to begin EN via the stomach. It is recommended that EN begin in the first 24-48 hours after hospital admission and after resuscitation goals have been met. There are numerous commercial enteral nutrition (EN) products available that vary in caloric density, inclusive of protein and non-protein calories, (1.0-2.0 kcal/mL), fiber content, macronutrient source, as well as specialized products designed for patients with specific dietary restrictions or allergies, and finally disease specific formulas. EN is available in polymeric formulas, in which the whole milk protein is intact, or hydrolyzed formula in which the milk proteins are partially broken down to aid in digestion. The various formulas vary in cost but nearly all are less than $10 USD/1000kcal, which is substantially less expensive than 500mL of parenteral nutrition (PN), estimated to cost $173 USD(显然肠内比肠外经济划算). Disease specific formulas are available but are used infrequently and only in specialized situations beyond the scope of this review. In the immediate perioperative period (within 5 days pre-op or post-op), an immunomodulating formula should be started, but should be discontinued in the setting of sepsis, though it should be noted that the data for these formulas in the trauma patient population is less robust than in medical patients. If there is no surgery planned, a high protein polymeric formula should be used. It is recommended that EN begin at a rate of 20ml/hour to assess tolerance (discussed below) and advanced to a goal rate over the following 12-24 hours unless there is some contraindication to advancement（明确了起始速度）.Patients should receive 70-80% of their energy needs over the first one to four days and achieve 100% of protein and calorie goals by day five（第5天要达100%目标热卡）. Consideration should be given to implementing volume-based feeding protocols, which have been shown to safely increase the protein and energy delivered although there has been little evidence of a positive impact on clinical outcomes.
Trophic feeding（营养性喂养） has been advocated for its promotion in the maintenance of gut integrity, positive influence on the immune system, and the stimulation of insulin sensitivity, among other benefits. Special consideration for obese patients (BMI > 30 kg/m2) includes reduction of protein and energy goals to 11-14 kcal/kg/day and 2.0-2.5g/kg/day of protein based on actual body weight（肥胖人群）. Patients with a diagnosis of acute respiratory distress syndrome (ARDS)/acute lung injury (ALI) may also benefit from trophic (<50% calculated protein and energy requirements) to promote feeding tolerance with equivalent ventilator-free and mortality outcomes by maintaining the provision of protein but limiting the excessive production of CO2.
Controversy remains regarding the administration of EN while patients require continuous administration of vasopressors, with some studies demonstrating concern about gastrointestinal complications without a mortality benefit or reduction in infections. Two studies, however, have realized a mortality benefit when EN was administered with vasopressors. Another study demonstrated the safety and efficacy of EN delivery to patients on vasopressors, with concomitant improvements in protein and energy delivery.
The SCCM/ASPEN guidelines recommend withholding EN in patients on “high-dose” vasopressors, but the exact definition of “high-dose” remains elusive. Some studies reveal the safety and benefit to early trophic feeding to patients requiring vasopressors. Additional randomized, controlled trials will be required to answer this question, but with the available evidence, we recommend that beginning trophic rate EN (10-20ml/hour) with slow advancement (to goal rate over the following 24-48hr) is safe and tolerated in patients receiving the equivalent of 12.5mcg/min of norepinephrine or less, or up to 0.3ug/kg/min（明确了有去甲多少剂量是安全的，给出了病人开始的输注速度并且缓慢增加，再24-48h达满意速度）. Patients should not have escalating vasopressor requirements, including the need for the addition of a second or third vasopressor agent even at “low dose”, or rising lactate levels. The gastric route of delivery is preferred and vigilance is required to assess for signs of feeding intolerance or bowel ischemia such as abdominal distention, emesis, or peritonitis.
D. 肠内营养的监测与维持
After initiation of EN, daily assessments（每日评估） for tolerance and readiness for volitional intake should ensue, tempered by the risk of potential aspiration in the debilitated critically injured adult. Tolerance of EN is a clinical decision and should not be determined by gastric residual volume (GRV) assessment alone（胃残余量不可靠）. The routine use of GRV is discouraged as this practice has been demonstrated to yield unreliable and variable quantities of residual tube feeds and leads to unnecessary and prolonged periods of nil per os (NPO). Clinician discretion is recommended in using GRV as an adjunct for monitoring critically ill patients whose physical exam is unreliable (eg, neuromuscular blockade, severe TBI) when concern about tolerance arises. When the decision is made to use GRV for monitoring, we recommend a threshold of >500ml to hold EN（如果要用这项指标，需要达到500ml以上）.
Though standard pre-procedural practice is to make patients NPO for a period of 8-12 hours, we recommend against this historical practice, particularly for the critically ill patient with a protected airway (endotracheal tube or tracheostomy appliance). In a 2020 consensus statement, the authors conclude, “Current concerns about aspiration are out of proportion to the actual risk”. Frequent interruptions of EN for procedures contributes to failures to meet protein and energy delivery goals and has been shown to propagate an ileus. For patients undergoing a non-aerodigestive tract procedure and who have a protected airway, we recommend continuing EN until the time of the procedure. As most studies excluded patients who will be in the prone position for the procedure, we recommend caution in continuing EN until the time of these procedures.
Monitoring for tolerance includes evaluation for abdominal distention, pain, emesis, obstipation, radiographic evidence of obstruction or severe ileus, or clinical decompensation. As previously stated, ileus may be propagated, not mitigated, by NPO periods. In the event a patient receiving EN via the gastric route demonstrates an ileus causing emesis or distention, and there is concern for gastroparesis and subsequent aspiration, an attempt should be made to place nasojejunal access prior to abandoning EN altogether. At this point, prokinetic medications such as metoclopramide or erythromycin may be added.
If the patient appears to be tolerating full dose EN, it should be maintained and
consideration given to the expected duration of EN. If it is expected that even after resolution of the critical illness, oral intake will not be reasonable (eg, severe TBI), consideration should be given to placement of durable enteral access after 7-14 days. (60) Once it appears a patient can be extubated and safely consume >60% predicted protein and energy of their own volition, EN may be discontinued.
E. 肠外营养
As previously noted, PN is more costly than EN, requires central venous access, and does not confer the aforementioned benefits of using the GI tract. Therefore, PN is reserved for the patient who cannot safely meet protein and energy goals via EN, as EN is the preferred route of nutrition delivery. In fact, recent studies have demonstrated that PN administered to critically ill patients within 5 days has detrimental effects For patients with a high risk of malnutrition, such as those with a pre-admission BMI of ≤18.5kg/m2, unintended weight loss 10% body weight over the previous three months, or <75% energy intake in seven days prior to admission, should be considered for PN within the first 24-48 hours if EN cannot safely be started. Patients who do not meet these high-risk criteria should be reassessed for EN adequacy daily up to seven days prior to the initiation of PN. The initial PN prescription should provide full protein requirements and energy delivery should be increased over a period of five days to reach the calculated goals. Hypocaloric prescriptions should be used for patients at risk of refeeding syndrome while maintaining protein delivery. For patients who have had a period of EN, but later are unable to tolerate EN due to severe ileus or a change in clinical status, PN should be considered. Evaluation and decision management can be made by returning to the beginning of the algorithm. Daily assessments should be performed to determine readiness for EN or volitional PO intake, as EN remains the preferred route of nutrition support for its evidence of gut mucosal integrity, ease of administration, reduced complications, and lower cost compared to PN. However, the evidence to support the benefit of a course of PN less than seven days is limited.
争议与知识空白
Discussion among the membership of Western Trauma Association (WTA) revealed lack of consensus regarding the use of EN while patients require vasopressors. While there is agreement that EN should not be completely withheld in patients on stable, low dose vasopressors, defining “low dose” remains elusive. There was robust consensus that limiting NPO periods is of paramount importance but learly defining which patients can safely continue EN (gastric vs small bowel access, prone vs supine procedure positioning) was not achieved. It is also important to note that there are many areas of this algorithm that lack high quality evidentiary support, and where further focused research is required. Table 1 provides a list of the most important specific topics or existing research “gaps” related to this topic that were identified by the authors during the development of this algorithm.
总结
In summary, based on the available evidence and the collective experience and expertise of the WTA membership, we provide these recommendations to promote the optimal delivery of nutrition therapy to this high-risk population: critically injured adults. Our algorithm aids the clinician in a step-wise approach to assessing patients for nutrition support therapy readiness and guides a management pathway that puts nutrition delivery on par in importance with all other interventions and therapeutics we offer our critically ill patients, not simply an adjunct, starting on day one. This algorithm challenges historical practice patterns that withhold crucial protein and energy delivery required for healing, such as prolonged NPO periods for procedures, mild ileus, or the use of vasopressors. Early, adequate nutrition delivery has been demonstrated to improve patient outcomes and this algorithm will provide the clinician with a step-by-step decision tree to provide this crucial therapy.
最后是决策流程，很可惜，原文暂时没有提供高清版
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