【Waiting for change】
(2) Protein targets of nutritional therapy
The hypercatabolic state after nerve injury is associated with significant proteolysis and muscle loss, leading to an increased demand for protein. Therefore, it is generally believed that critically ill neurosurgery patients have higher protein requirements than other critically ill patients. But it remains unclear what the optimal protein target should be, nor is it clear when the best time to reach protein energy targets is. According to previous recommendations, patients can supplement protein at 1.2~2.0 g·kg-1·d-1[30], of which more than 50% should come from high-quality protein, and can be obtained through the nitrogen balance formula: nitrogen balance (g/24 h) = protein intake (g/24 h)/6.25-[urea nitrogen in urine (g/24 h) + 4] is evaluated and requires continuous monitoring. High protein supply is associated with improved nitrogen balance.
Whether high protein supply improves outcomes in critically ill patients remains controversial. A recent meta-analysis showed that high protein supply may be associated with improved mortality in patients with nutritional risks [31]. A number of observational studies support that high protein supply can improve the body's protein balance, reduce mechanical ventilation time and higher survival rate [27, 32-34]. When the protein supply is >1.3 g·kg-1·d-1, patient survival It can be significantly improved [22].
However, the results of many studies have shown that high protein supply does not have a significant impact on clinical outcomes. The results of a clinical RCT published in 2021 suggested that patients who received a higher protein supply [(1.5±0.5) vs. (1.0±0.5) g·kg-1·d-1] had better clinical outcomes or quadriceps muscle strength. There was no difference in layer thickness [35]. A recent multicenter RCT including 120 patients studied high- versus low-protein enteral nutrition formulas (100 g/l vs. 63 g/l). Compared with low-protein enteral nutrition formulas, high-protein formulas The protein supply was higher (1.52 g·kg-1·d-1 vs. 0.99 g·kg-1·d-1, body weight was calculated as ibw), but the clinical outcomes (90-day mortality) were not the same between the two groups. There is no difference[36]. There are still some large-scale clinical trials underway such as efort (nct03160547), aiming to evaluate the impact of high and low protein supply on critically ill patients. It is hoped that the latest trial results can give clinicians more guidance. The protein treatment target value for non-dialysis patients with impaired renal function must be analyzed based on the specific condition and decided through multidisciplinary discussion when necessary.
Recommendation 8: The existing evidence cannot provide recommendations on the optimal protein target and the best time to reach the target. For critically ill neurosurgery patients, the protein target can be set at 1.2~2.0 g·kg-1·d-1 in the acute phase. .
(3) Carbohydrate and fat targets for nutritional therapy
1. Carbohydrates and glucose: When performing enteral nutrition, carbohydrates are the preferred substrate for energy production. Carbohydrates are generally considered harmless, but high carbohydrates may be the main cause of feeding intolerance. Enteral nutrition Other polysaccharide components in the formula may also cause intolerance in susceptible patients. In neurosurgery patients, the incidence of stress hyperglycemia is high. Therefore, it is recommended that the energy supply ratio of carbohydrates does not exceed 60% [37], and carbohydrates Compounds are often chosen from sources with a low glycemic index.
During parenteral nutrition, excess glucose-based energy supply is associated with hyperglycemia, increased CO2 production, increased lipogenesis, increased insulin requirements, and has no advantage in reducing protein consumption. Hyperglycemia associated with glucose-rich parenteral nutrition often requires higher doses of insulin. Therefore, it is recommended that the intravenous glucose dosage should not exceed 5 mg·kg-1·min-1[38?39].
2. Fat and venous lipids: Lipid oxidation provides more than half of the energy required by the liver, heart and skeletal muscles. Although some studies have evaluated the optimal sugar/fat ratio from the perspective of improving nitrogen balance, due to severe neurosurgery patients Changes in lipid metabolism, the optimal total amount of daily lipids required is currently unclear. In addition to the total amount, the composition of the enteral nutrition formula (ef) needs to be carefully evaluated during enteral nutrition. The fat composition included should limit but not completely exclude w?6 fatty acids. Monounsaturated fatty acids should be provided, w ?3 fatty acids, reduce saturated fatty acids and avoid trans fatty acids. The recommended dosage of essential fatty acids (fatty acid, fa) is in accordance with the dietary reference intake.
At the same time, fat absorption is impaired in severe patients, and lipid overload may cause immunosuppression and impair lung and liver function. For intravenous lipids, the upper limit of supply is recommended to be 1 g·kg-1·d-1, and the maximum tolerated dose is 1.5 g·kg-1·d-1. The lipid ratio can be adjusted according to blood triglyceride levels and liver function [40].
Recommendation 9: When critically ill neurosurgery patients undergo enteral nutrition, it is recommended that the carbohydrate energy supply ratio does not exceed 60%. The optimal fat intake is not yet clear. It is recommended to adjust based on blood triglyceride levels and liver function. During parenteral nutrition, it is recommended that the dosage of glucose should not exceed 5 mg·kg-1·min-1. Venous lipids (including non-nutritive lipid sources) should not exceed 1.5 g·kg-1·d-1, and lipid overload should be avoided.
[3. Enteral nutrition treatment for critically ill neurosurgery patients]
(1) Timing to start enteral nutrition therapy
Aspen/sccm (2016) and the "Expert Consensus on Nutritional Support and Treatment of Critically Ill Patients in China" both recommend starting enteral nutrition within 24 to 48 hours, and enteral nutrition is superior to parenteral nutrition [16, 41]. The European Society of Parenteral and Enteral Nutrition recommends that patients with craniocerebral trauma initiate enteral nutrition within 48 hours [42]. The European Society of Critical Care Medicine [43] recommends that although the current multiple RCT studies cannot yet draw a conclusion whether early enteral nutrition will definitely have more benefits than harms, based on expert opinions, it is recommended for patients with traumatic brain injury, ischemic or hemorrhagic stroke. , patients with spinal cord injury should start enteral nutrition early.
Situations for delayed enteral nutrition therapy: uncontrolled shock, hypoxemia, severe acidosis, active gastrointestinal bleeding, gastric retention >500 ml/6 h, intestinal ischemia, intestinal obstruction, abdominal compartment Syndrome and other conditions should delay the initiation of enteral nutrition. For patients with severe brain injury who undergo therapeutic mild hypothermia, because their metabolic levels are severely reduced and their gastrointestinal function is significantly inhibited by cooling, it is recommended to provide low-dose early enteral nutrition and gradually increase the amount after rewarming.
Recommendation 10: For critically ill neurosurgery patients, enteral nutrition therapy should be initiated early (within 24 to 48 hours after admission to the intensive care unit) when hemodynamics are stable.
(2) Formula selection for enteral nutrition therapy
1. Whole protein formula versus short peptide formula: Based on the results of an international multi-center cross-sectional study, it is shown that critically ill neurosurgery patients are often in a low feeding state, and their daily intake of calories and protein are lower than the prescribed amount. The reasons are as follows: Enteral nutrition intolerance, impaired gastrointestinal motility, etc., the most common clinical manifestations are diarrhea and gastroparesis, which will affect the absorption of nutrients and lead to insufficient energy and calorie intake. The existing aspen nutritional guideline recommends standard whole protein formula as the preferred dosage form for enteral nutrition [30]. Short peptide nutritional solution contains short peptides and medium-chain fatty acids, which can improve gastrointestinal tolerance. Especially for patients with gastrointestinal function impairment, short peptide formulas are easier to digest and absorb, and reduce the incidence of diarrhea. However, the results of a single center RCT for enteral nutrition treatment in patients with severe craniocerebral trauma also showed that compared with the whole protein formula, the short peptide formula has a higher osmotic pressure and may also cause gastrointestinal intolerance, and both groups There was no significant difference in the average daily intake of calories and protein between the two groups [44].
2. Diabetic formula compared with standard formula: A survey found that the rate of hyperglycemia in critically ill neurosurgery patients can be as high as 60%, regardless of whether they have a history of diabetes or not. Hyperglycemia is an independent risk factor for severe ICU complications, such as electrolyte imbalance, infection, prolonged hospitalization, and increased mortality. Diabetic nutritional formulas are usually low in sugar and high in monounsaturated fatty acids, and the maltose in the standard formula is replaced by slowly digested starch. Studies have shown that compared with standard enteral nutrition formula, diabetic formula combined with insulin therapy can effectively control blood sugar levels in patients with severe ischemic stroke [45].
3. Immune-modulating formula compared with standard formula: In the 2016 aspen guidelines, based on a small sample study (40 patients), compared with standard enteral nutrition formula, immune-modulating formula (mainly containing arginine, glutamine , w-3 fatty acids, etc.) can reduce the incidence of infection in patients with craniocerebral trauma [30]. Rai et al. [46] conducted a prospective RCT of moderate to severe TBI patients who were randomly assigned to receive enteral nutrition with immune formula and standard formula. The results showed that the inflammatory index (il-6) of patients in the immune formula group was significantly reduced. At the same time, The antioxidant index (glutathione) was significantly increased; in addition, the total protein level of patients in the immune formula group was also significantly increased. In a single-center RCT for a variety of critical neurosurgical diseases, Chao et al. [47] found that compared with standard enteral nutrition formula, the CD4+t lymphocyte count and CD4+/ The proportion of CD8+ was significantly increased, serum interferon-γ was significantly increased, and the levels of inflammatory factors such as tnf-α, il-6, il-8, and il-10 were significantly reduced; it can be seen that immune-enhancing enteral nutrition The formula can significantly improve the immune status of critically ill neurosurgery patients. In another retrospective study, Painter et al. [48] found that compared with standard enteral nutrition formula, immune-enhanced formula can reduce the incidence of bloodstream infection, but has no effect on lung infection and urinary tract infection. Significant differences.
4. Mixed formula with added dietary fiber: Severe neurosurgery patients usually have poor gastrointestinal function tolerance. When patients have persistent diarrhea, enteral nutrition can be replaced with a mixed formula containing dietary fiber. When choosing dietary fiber additives, less soluble fiber can cause blockage in feeding tubes. Fibers with high soluble properties, such as partially hydrolyzed guar gum, wheat lake essence, inulin or fructooligosaccharides, do not form a gel when dissolved, and the probability of feeding tube blockage is greatly reduced. Soluble dietary fiber supplementation can reduce the incidence of clinical diarrhea [49, 50, 51]. Soluble dietary fiber uses intestinal probiotics to produce short-chain fatty acids through fermentation, promotes the growth of intestinal beneficial bacteria, and regulates intestinal microecology.
Recommendation 11: For enteral nutrition treatment of critically ill neurosurgery patients, whole protein nutritional formulations can be selected. For patients with gastrointestinal function impairment, short peptide formulations can be selected.
Recommendation 12: For patients with diabetes or hyperglycemia, using diabetic enteral nutrition formula can help improve blood sugar control in the acute phase.
Recommendation 13: For patients with a higher risk of infection, immunomodulatory enteral nutrition formula may be used.
Recommendation 14: For critically ill neurosurgery patients with persistent diarrhea, a mixed formula containing dietary fiber may be considered.
(3) Feeding approaches for enteral nutrition therapy
Nasogastric tube feeding can promote normal physiological stimulation of the gastrointestinal tract and is technically simple and easy to implement. However, postpyloric feeding requires certain experience in tube insertion and may delay the start of enteral nutrition. In addition, an international multi-center observational study included a total of 1,691 critically ill neurosurgery patients (including cerebral hemorrhage, subarachnoid hemorrhage, craniocerebral trauma, intracranial infection, stroke, epilepsy, and neurological tumors) in 353 ICUs. , to evaluate the effects of gastric feeding and intestinal feeding on nutritional and clinical endpoints. The results found that although patients in the gastric feeding group were more likely to interrupt enteral nutrition due to gastrointestinal complications, they were better able to accept adequate caloric feeding; in addition, the two groups of patients had better mechanical ventilation time and survival to discharge. There was no statistically significant difference between other important clinical endpoints such as proportion [52]. Therefore, nasogastric tube feeding is recommended as the preferred route of enteral nutrition.
Postpyloric feeding reduces the incidence of pneumonia in people at high risk of aspiration. Critically ill neurosurgery patients have a high proportion of consciousness disorders, weak airway protection, and a high proportion of mechanical ventilation, making them a high-risk group for aspiration. In an RCT study on the enteral nutrition route in patients with severe TBI, the patients were randomly divided into transgastric tube feeding and transpyloric feeding groups. The results of the study found that compared with transgastric tube feeding, postpyloric feeding can significantly improve Reduce the incidence of pneumonia [53]. A meta-analysis compared the impact of post-pyloric feeding and transgastric feeding on the incidence of pneumonia and other important prognostic endpoints in patients with severe TBI. A total of 5 RCT studies with 325 patients were included. It was found that compared with transgastric feeding, post-pyloric feeding was more effective than gastric feeding. Feeding can significantly reduce the incidence of aspiration pneumonia and ventilator-associated pneumonia [54]. Therefore, postpyloric feeding is feasible for patients who are intolerant to nasogastric tube feeding and are at high risk of aspiration.
Recommendation 15: Nasogastric tube feeding is the preferred route of enteral nutrition. For patients who are intolerant to nasogastric tube feeding and have a high risk of aspiration, post-pyloric feeding can be performed in centers with conditions.
(4) Feeding methods for enteral nutrition therapy
Although continuous feeding is different from the intestinal physiological model, continuous feeding causes fewer gastrointestinal and respiratory complications and can achieve nutritional support goals earlier. Compared with continuous feeding, although intermittent feeding is more physiological and can promote protein synthesis, it also increases the risk of high gastric residual volume (grv), diarrhea and aspiration.
The results of a latest meta-analysis in 2021 that included 14 trials and a total of 1,025 critically ill patients showed that compared with continuous feeding, intermittent feeding leads to an increased risk of feeding intolerance and high grv, and errors occur when the duration is >1 week. The risk of smoking increases [55]. The results of multiple clinical studies have shown that continuous feeding can provide more enteral nutrition and have a lower probability of gastrointestinal intolerance and feeding interruption [56, 57, 58].
Recommendation 16: It is recommended for critically ill neurosurgery patients to use continuous pumping for enteral nutrition.
