4.1 Combined use of several methods were conducted to assess gastrointestinal functions and risk of feeding intolerance in STBI patients
The results of the survey showed that more than a half of respondents chose at least 3 options to assess patients’ gastrointestinal functions as well as predicting the risk of feeding intolerance, which indicated that most of the medical staff use multiple methods to evaluate gastrointestinal functions and tolerability of EN in patients with STBI. Further analysis of the collected data suggested that the current assessment methods of gastrointestinal functions are mainly based on clinical symptoms related to gastrointestinal dysfunction (85.04%), GRV (82.23%) and bowel sounds (78.31%). There were only 28.81% and 15.66% of the respondents took AGI grade and medical imaging methods (motility of gastric antrum), respectively, which showed that these 2 measures were not yet widely applied in clinical practice. In 2012, European Society of Intensive Care Medicine (ESICM) proposed AGI grade to assess the degree of acute gastrointestinal impairment in critically ill patients . The low prevalence of AGI grade in evaluating gastrointestinal functions might due to 2 reasons: AGI grade lacks of objective evaluation indexes and is hard to quantify the severity; on the other hand, as most respondents involved in the survey were nurses (89.06%), we supposed that the use of AGI grade might have not been included in the scope of nurses’ responsibility. Using imaging measure to evaluate gastrointestinal functions is an emerging technique in the field of intensive care in recent years, and it can visually reflect the gastric antrum movement . The low prevalence of this imaging measure may be due to that it’s a novel technique and has not yet been widely conducted among STBI patients. We suggest that timely comparative studies of emerging methods with traditional methods are urgently needed to confirm their effectiveness and feasibility in assessing gastrointestinal functions, in order to make these newest techniques timely applied in critically ill patients.
The present study found that 71.39% of respondents predict the risk of feeding intolerance in STBI patients based on injury severity (GCS, APACHE II, etc.), 60.84% of the respondents based on assessment scales, and 60.64% of the respondents based on the patients’ basic characteristics (age, sex, etc.). It is well known that disease severity is closely related to the occurrence of feeding intolerance . GCS and APACHE II scores are applied in STBI patients within 24 hours after admission to assess the injury severity . The risk of gastrointestinal dysfunctions is predicted on the basis of these assessments. As these 2 scores are the classic assessment methods for STBI patients, they have long been used in clinical practice and are therefore more widely applied. Studies have shown that basic characteristics of patients such as age and sex are risk factors for disease severity [16, 17]. For example, atrophy of intestinal mucosa can occur in the elderly, affecting the absorption and transportation of water and electrolytes . Therefore, clinicians and nurses should pay attention to the basic characteristics of patients such as age and sex when considering EN delivery. Recent years, researchers in China have developed risk assessment scales to facilitate the assessment and prediction of the feeding intolerance in critically ill patients [19, 20]. These results of present survey showed that the assessment scales for feeding intolerance are used widely among STBI patients, indicating that clinical staff prone to use methods which are based on objective indexes and clear grading. However, considering the heavy workload and various assessment scales needed to complete in ICU, we suggest that it is necessary to further optimize the assessment scales and procedure, in order to improve the effectiveness in evaluation of feeding intolerance and reduce the workload of medical staff.
4.2 Evidence-based strategies for EN delivery have been widely used
We found the following feeding strategies were mostly applied in China: using nasogastric tube (91.16%), 30°-45° of head-of-bed elevation during EN (89.46%), continuous infusion method (72.89%), 38-40℃ of EN solution, and initiating EN within 24-48 hours after admission (61.45%) with <500ml EN solution (50%). Some of these strategies were in accordance with several guidelines and expert consensus on nutritional support for critically ill patients [21, 22], which indicating that most clinicians and nurses are able to apply evidence-based strategies during EN delivery. In recent years, it has been reported that administration of low-temperature EN solutions (22°C-25°C)  and intermittent infusion semi-solid solutions [24, 25] can reduce the risks of gastric ulcer and aspiration, while these 2 strategies were only used among 13.65% and 38.35% of the respondents, respectively. The low utility rates might due to the related researches were limited, causing insufficient popularization and application. Thus, for these effective methods found in clinical practice, we should summarize and spread them timely, and carry out multicenter and multidisciplinary studies to confirm their effectiveness.
The amount of GRV is positively correlated with the incidence of reflux and aspiration [26, 27]. Therefore, monitoring GRV is an important part during EN. The collected data in our survey presented that retraction of gastric content by syringe is still the main method for monitoring GRV (93.67%). However, it has been reported that the accuracy of use of syringe withdrawal would be influenced by various factors, such as patient’s position and gastric tube diameter . Recent years, more accurate and feasible methods for monitoring GRV have been explored, including ultrasound. Some studies have shown that GRV could be calculated accurately using 3-dimensional morphology by ultrasound, which would not be affected by other factors [29, 30]. However, only 9.74% of the respondents chose to apply ultrasound to monitor GRV. The reason for this result may be related to the fact that use of ultrasound for EN is still in its early phase, and the ultrasound instrument is a highly specialized technique, which requires systematic learning and training. We suggest that we should focus on the timely training of new methods or techniques to make them applied in clinical practice better and faster.
The results also showed that gastric retention in China is mainly defined by GRV > 200 ml/time within 24 hours (57.73%). However, GRV > 500 ml every 6 hours was recommended by ESICM in 2017  and has been only used in 36.95% respondents. The definition of gastric retention can directly influence the EN delivery, as well as preventive and curative measures. If the definition is too conservative, it may lead to more feeding interruptions and clinical interventions during EN; if the threshold of the definition is too strict, it might increase the risk of feeding intolerance. Therefore, how to define the threshold of gastric retention still needs more further scientifically explorations.
4.3 The prevention of feeding intolerance has been paid more attention in clinical practice
Strategies for promoting gastrointestinal motility (81.22%) and defection (84.14%), protecting the mucosa (93.67%), and modulating gut microbiota (80.92%) have been widely used before the occurrence of feeding intolerance. We found that antacid agents (84.13%) are still important treatments for preventing stress-related gastrointestinal bleeding among STBI patients. The antacid is a double-edged sword. It can protect the gastrointestinal mucosa, while it will also increase the gastric pH and aggravate the risk of feeding intolerance. Expert consensus has stated that we should discontinue the application of proton pump inhibitors as soon as possible when TBI patients could take adequate energy by oral feeding . Thus, how to use the antacid properly still needs further exploration.
The current survey also found that clinicians have paid attention to the effects of gut microbiota for STBI patients, and probiotics were mainly used in clinical practice (79.01%). With the increasing understanding of the interaction of gut microbiota-brain axis, it has been found that regulating the gut microbiota after TBI can not only improve gut dysbiosis, but also promote the recovery of neurological functions [33, 34].
For measures to improve gastrointestinal motility in STBI patients, most respondents chose prokinetic agents (73.29%) other than traditional Chinese medicine (22.59%). Although several studies in China have confirmed that measures such as Chinese medicine rhubarb , Da Cheng Qi Tang , and acupuncture  can significantly improve gastrointestinal motility in STBI. However, the applications of these effective methods of traditional Chinese medicine are still very limited. We suggest that the collaborative working model of Traditional Chinese Medicine department and physiotherapy department could be established to promote the applications of effective traditional Chinese medicine measures.
The results of survey indicated that enema is a commonly used strategy to assist defection in STBI patients. While enema can only alleviate the symptoms, but not treat primary cause of constipation. Studies suggested that nursing strategies such as rectal stimulation  and acupoint massage  are effective in stimulating gut motility and promoting defecation reflexes in patients. There were only 28.41% of the respondents chose nursing strategies, which might due to that these methods are mild and takes a longer time and shows slower progress. Moreover, it may also relate with the limited manpower of ICU nurses who are unable to perform tasks other than those prescribed by clinicians.
Most of the respondents gave STBI patients non-nutritional preparations (glucose, warm water, etc.) at the initiation of EN. Critically ill patients are commonly accompanied by gastrointestinal dysfunctions. Solutions such as glucose and water that can be easily digested and absorbed are given firstly in clinical practice, which will make the gastrointestinal tract to adapt the following EN solution. A research reported that giving non-nutritional preparations 1 day before giving EN solution could reduce the incidence of diarrhea in critically ill patients . We also found that rice broth, milk or other solution were also used as the initial type of EN formula. This result suggests that there is a need to further explore and standardize what, how much and how long to give at the beginning of EN in STBI patients, so that EN can be delivered smoothly at the early stage.
4.4 Preventive measures for feeding intolerance need to be further explored
We provided an analysis of the reasons for not taking preventive measures. The survey found that the main reason why preventive measures are not used is “unclear preventive effects”. The results suggest that comparative studies of various measures for preventing feeding intolerance are urgently needed, which are important to confirm the effectiveness of these treatments and provide basis for clinical practice. Furthermore, medical staff should make an effort to learn the knowledge relevant to EN and the latest techniques, methods and theories, in order to reduce the risk of feeding intolerance as effective as possible.
As a nationwide survey, this survey is expected to provide a more realistic picture of the clinical conditions regarding feeding intolerance in STBI patients. In view of the diversity and complexity of clinical measures in practice, the survey was designed with the option “others” as the final option, in order to discover the points that the survey did not cover. We found that some nurses filled in “relying on dietitians’ assessment or suggestion” or “no medical advice”. This indicates that some nurses only act as a “implementer” during EN delivery period and lack initiative. A study has confirmed that nurse-led EN delivery protocols can help reduce feeding interruptions and improve the nutritional status of critically ill patients . We suggest that it is important for nurses in ICU to improve their role awareness and skills in EN support for critically ill patients, which might significantly contribute to reducing the risk of feeding intolerance.
This cross-sectional survey study provides a snapshot of medical staff’s views on preventive strategies for feeding intolerance in STBI patients. The demographic of the participants and the fact that participants were mostly recruited from grade II level A or above hospitals which may limit the generalizability. The non- probability sampling methods (convenience sampling and snowball sampling) used to approach hospitals or participants for inclusion in this study signifies that the findings are likely to not be generalizable to the wider medical staff in China.