Background

Adequate nutritional support is important in severely ill patients. In recent years, the importance of adequate nutritional support has been highlighted because catabolic activity and a negative nitrogen balance resulting from systemic inflammation induced by severe stress such as trauma are associated with a poor prognosis. Therefore, an inadequate supply of calories and major nutrients to trauma patients can result in significant negative outcomes. In trauma patients, like other intensive care unit (ICU) patients, timely enteral feeding plays a positive prognostic role, and the existing enteral nutrition (EN) strategy is related significantly to good outcomes in nutrient delivery [1]. However, situations such as gastrointestinal trauma or surgery/examination requiring fasting while hospitalized in the ICU impede the supply of target calories and proteins [2,3]. Several evidence-based protocols applicable to trauma patients have been shown to increase the reliability of nutritional therapy provided to ICU patients [4,5]. Institutions utilizing EN protocols have shown significant improvements in nutrition practice compared with facilities that do not use such approaches [6]. Volume-based feeding (VBF) protocols have been shown to be effective in achieving the targeted daily feeding goals in trauma patients requiring frequent imaging examinations or surgeries [7]. However, many trauma surgeons and physicians are reluctant to implement VBF protocols due to safety concerns. Adding to the surgeons’ reluctance is the lack of well-designed clinical studies in surgical and traumatic ICU populations. Although studies have reported successful increase in energy transfer using VBF protocols, the clinical outcomes of such protocols have not been established [8].

Objectives

This study’s aim was to determine if implementation of a VBF protocol for adult trauma patients admitted to a single trauma center could help achieve early EN goals and improve clinical outcomes.

Ethics statement

This study was approved by the Institutional Review Board of the Ajou University Hospital (approval number: AJOUIRB-MDB-2021-580). The committee waived the need for informed consent due to the observational design of the study, which posed little risk to the study population.

Study design

It is a retrospective cohort study. It was described according to the STROBE statement available at: https://www.strobe-statement.org/.

Setting

This study was conducted at a 40-bed trauma intensive care center from October 2020 to September 2021. This trauma center has the capacity to provide in-patient treatment to about 3,000 trauma patients per year. The center also participates in the Trauma Quality Improvement Program of the American College of Surgeons, in which it is compared with Level I/II trauma centers in the United States, to achieve quality control.

Standard of care for EN

Prior to the introduction of the new EN protocol (VBF protocol), a multidisciplinary trauma team assessed the patient’s condition during morning rounds in the trauma intensive care unit (TICU). A registered dietitian belonging to the multidisciplinary trauma team identified high-risk patients based on The Nutrition Risk in Critically Ill score for nutrition. The target calorie intake for these patients was in the range of 25–30 kcal/kg/day considering the patient’s nutritional characteristics; for some patients, it was determined considering the basal energy expenditure evaluated using an indirect calorimeter. Patients who were unable to eat orally for a long period of time underwent EN with insertion of a feeding tube via nasogastric or percutaneous endoscopic gastrostomy. The target protein was calculated as 1.3–3.0 g/kg/day and was adjusted with reference to patient weight change and prealbumin level. During morning rounds, the attending physician updated the patient’s clinical condition and prescribed the rate of tube feeding for the day. Although there were minor differences among patients, the rate of enteral feeding generally started at 20 mL/h and increased by 20 mL/h every 4 hours until the target rate was reached.

Introduction of the new EN protocol

A new EN protocol involving volume-based principles was developed over approximately 6 months, from March to August 2020. According to the new protocol, the charge nurse initiated EN immediately following patient hospitalization upon approval of the attending physician, without waiting for an evaluation by the multidisciplinary team. Once the patient reached the target enteral feeding rate, if feeding was interrupted due to examination or surgery, the charge nurse applied the recalculated speed to achieve the original target volume faster when feeding was restarted (Fig. 1). To apply the new EN (VBF) protocol, ICU nurses were trained for approximately two months. The new EN protocol was applied to patients assigned to nurses trained in the new EN protocol, and the existing EN protocol was applied to patients who were not assigned to these nurses. During admission, patients were randomly assigned to a charge nurse.

Fig. 1. Volume-based feeding algorithm.
EN = enteral nutrition; TICU = trauma intensive care unit; ICU = intensive care unit; NG = nasogastric; OG = orogastric; CIx. = contraindication; GI = gastrointestinal; Abd. = abdominal; GRV = gastric residual volume; BP = blood pressure; Prox. = proximal; PN = parenteral nutrition; NPO = nil per os; BST = blood sugar test; C. difficile = clostridium difficile.

Participants

The patients included in the study were adults aged 18 years or older who were admitted to the TICU for at least 72 hours.

Variables

The primary outcome variable is in-hospital mortality, and the secondary outcomes are the start time of EN, the number of calories and amount of protein supplied, and the time required to reach the target amount.

Data sources/measurement

Data were from the electronic medical records of the institute. Variables were extracted with patient’s information and clinical course. The outcomes of patients admitted to the TICU were compared between the group that utilized the VBF protocol and the group that did not.

Bias

There was no potential source of bias in selecting participants.

Study size

Since it is a retrospective study, sample size estimation was not done. All participants were selected according to the inclusion and exclusion criteria.

Statistical methods

All statistical analysis were performed using the Statistical Product and Service Solution IBM SPSS version 23.0 (IBM Corp.). Student’s t-test and analysis of variance were applied for quantitative data analysis, and the chi-square test was applied for qualitative data analysis. To study categorical variables with expected cell frequencies less than five, Fisher’s exact test was applied. Statistical significance decreased to P<0.05. For descriptive statistics, normally distributed data are presented as the mean±standard deviation, and nonparametric data are presented as the median.

Participants

A total of 2,935 patients visited the trauma center from October 2020 to September 2021; of these, 1,872 patients were admitted to the TICU and 388 underwent EN. Among the 388 patients, 163 stayed in the TICU for less than 72 hours, and 114 patients died within seven days of starting EN or were successfully transitioned to a complete oral diet and stopped tube feeding during the study period. Additionally, two pediatric patients younger than 18 years were excluded from the study, resulting in a total of 109 patients analyzed in this study. Of these 109 patients, 64 received EN according to the VBF protocol, while the rest received standard EN care (Fig. 2). There were no statistically significant differences in age, sex, body mass index, trauma severity indicators (Injury Severity Score, Trauma and Injury Severity Score, Glasgow Coma Scale), 24-hour red blood cell transfusion volume, and number of operations or laparotomies between the two groups. Further, there was no statistical difference between the VBF and control groups in terms of number of symptoms related to feeding intolerance, such as ileus, vomiting, constipation, diarrhea, and abdominal distension (Table 1). Three patients in the VBF group discontinued tube feeding due to feeding intolerance, a smaller number than in the control group (Table 2). According to the protocol, maintenance, reduction, or discontinuation of feeding was determined according to the severity of symptoms (Fig. 1).

Table 1

Patient demographics and enteral nutrition tolerances

Variable	VBF (n=64)	Standard of care (n=45)	P-value
Age (yr)	61 (46–72)	60 (41–69)	0.52
Sex, male	56 (87.5)	34 (75.6)	0.11
Weight (kg)	68.1 (54.2–75.4)	67.1 (56.4–78.5)	0.76
Body mass index (kg/m2)	23.7 (20.8–26.1)	24.6 (22.0–26.0)	0.64
Injury Severity Score	33 (23.5–43.0)	29 (19–43)	0.30
TRISS	0.87 (0.66–0.91)	0.91 (0.68–0.95)	0.30
Glasgow Coma Scale	11 (8–14)	13 (7–15)	0.43
Mechanism			0.79
Blunt	59 (92.2)	45 (100)
Penetration	1 (1.6)	0
Others	4 (6.3)	0
Red blood cell/24 h	4 (2.0–10.5)	4 (2.0–12.3)	0.79
Operation	49 (76.6)	36 (80.0)	0.67
Laparotomy	11 (17.2)	7 (15.6)	0.82
Ileus	4 (6.3)	2 (4.4)	>0.99
Vomiting	4 (6.3)	3 (6.7)	>0.99
Constipation	8 (12.5)	6 (13.3)	0.90
Diarrhea	7 (10.9)	4 (8.9)	>0.99
Abdominal distension	7 (10.9)	4 (8.9)	>0.99

Values are presented as median (IQR) or number (%).

VBF = volume-based feeding; TRISS = Trauma and Injury Severity Score.

Table 2

Enteral nutrition status at the end of follow-up

EN status	VBF (n=64)	Standard of care (n=45)
No cessation of EN	28 (43.8)	19 (42.2)
Transition to oral feeding	32 (50.0)	19 (42.2)
Deceased	1 (1.6)	0
Terminated due to feeding intolerance	3 (4.7)	7 (15.6)

Values are presented as number (%).

EN = enteral nutrition; VBF = volume-based feeding.

Fig. 2. Flow diagram for participants.
EN = enteral nutrition; ICU = intensive care unit.

Main results

Clinical outcomes

Clinical outcomes between the two groups, such as mortality, number of days in the ICU, or complication rate showed no differences during the study period. The average time to start EN in the VBF group was 16.9 hours earlier than that in the control group (P<0.01).

Target calories and proteins

There was no difference in target calories and proteins between the two groups (P=0.49), and there was no difference in the frequency of patients who succeeded in achieving 80% of the target calorie (P=0.11) and protein supply (P=0.31). The VBF group established this 80% of the target calorie (P<0.001) and protein intake (P=0.04) an average of one day faster than the control group (Fig. 3). During the study period, the VBF group had larger average daily supply of calories (P<0.001) and protein (P<0.001) per body weight than did the control group (Table 3).

Table 3

Primary and secondary outcomes of patients

Outcome	VBF (n=64)	Standard of care (n=45)	P-value
Primary outcomes
Mortality	6 (9.4)	2 (4.4)	0.47
ICU LOS (day)	16.5 (12.0–25.5)	19 (11–30)	0.71
Hospital LOS (day)	31.5 (22.8–46.0)	39 (20–51)	0.40
Total ventilator days (day)	10.5 (6.0–15.5)	12 (8–22)	0.28
Sepsis	6 (9.4)	2 (4.4)	0.47
Pneumonia	25 (39.1)	16 (35.6)	0.71
ARDS	7 (10.9)	6 (13.3)	0.70
AKI	4 (6.3)	4 (8.9)	0.72
UTI	3 (4.7)	2 (4.4)	>0.99
Delirium	23 (35.9)	18 (40.0)	0.67
Secondary outcomes
Time to EN initiation (h)	24.6 (18.7–41.1)	41.5 (22.0–58.1)	<0.01*
Target calorie (kcal/day)	1,730.5 (1,581–1,860)	1,725 (1,473–1,905)	0.49
Target 80% of calories achieved	59 (92.2)	37 (82.2)	0.11
Day on which 80% was achieved (day)	2 (2–3)	3 (2–5)	<0.01*
Calorie per body weight (kcal/kg/day)	20.5 (16.0–24.7)	15.6 (12.8–18.6)	<0.01*
Target protein (g/day)	82 (74.5–88.6)	77.7 (68.0–87.4)	0.15
Target 80% of calories achieved	57 (89.1)	37 (82.2)	0.31
Day when 80% protein was achieved (day)	2 (2–3)	3 (2–4)	0.04*
Protein per body weight (g/kg/day)	1.0 (0.8–1.2)	0.8 (0.6–0.9)	<0.01*

Values are presented as number (%) or median (IQR).

VBF = volume-based feeding; ICU = intensive care unit; LOS = length of stay; ARDS = acute respiratory distress syndrome; AKI = acute kidney injury; UTI = urinary tract infection; EN = enteral nutrition.

*p<0.05.

Fig. 3. Daily achievement rate of calorie (A) and protein (B) supply ratio against target.

Interpretation

In trauma patients, EN is often interrupted due to frequent imaging examinations and surgeries. Therefore, trauma patients are more likely to fail in early EN targets compared to medical patients or elective surgical patients [9]. For trauma patients, it is extremely important to establish a well-designed protocol to successfully set and achieve target calorie and protein amounts for nutrition supply. Our data are expected to help in developing protocols for proper nutrition in patients with severe trauma. It was identified that the daily energy and protein goals could be achieved more quickly using our protocol compared to the traditional method, and that there was a high possibility of supplying more energy and protein through the early stage of hospitalization. In addition, the new protocol did not cause adverse symptoms related to feeding intolerance, such as vomiting or diarrhea.

Comparison with previous studies

Although many studies are published on the efficacy and safety of VBF in the medical ICU [10,11], well designed studies in patients with severe trauma are lacking. Although unique surgical requirements or pathophysiological characteristics of severe trauma patients, such as damage control surgery or temporary abdominal closure, can create a potentially unsuitable environment, enteral feeding is an important tool for treatment of traumatized patients. Roberts et al. [12] recently published a retrospective review in Journal of Parenteral and Enteral Nutrition (JPEN) and examined the outcomes of patients with severe trauma admitted to surgical and medical ICUs within 48 hours of requiring mechanical ventilation. There were 171 patients who met the inclusion criteria, 25 of whom were trauma patients, and 16 of whom were treated with a VBF protocol. During the first 12 days of hospitalization, either ratio-based or volume-based EN plans were used (n=85 and n=86, respectively). Within the VBF group, energy supply increased 8.9% and protein supply increased 7.7%. In addition, the VBF group received more calories and protein, although its inclusion of only trauma patients resulted in a more homogeneous patient population than in other ICU types. Another study on provision of appropriate EN for trauma patients admitted to the ICU was recently published in JPEN and compared control (n=121) and study patients in a trauma ICU (n=118). They suggested three principles to enhance nutrient delivery.

First, EN should be initiated as quickly as possible. Second, fasting was limited, and proper nutrition was provided to the patient before surgery. Third, if the patient had been fasting for a certain period, additional nutrition was supplied through a separate protocol. This strategy can serve as a reference for other organizations that seek to incorporate similar guidelines. Those authors concluded that their approach started EN sooner, reduced the time to reach calorie goals, and improved overall EN delivery. The authors also reported an additive effect of reduced pneumonia in the intervention group. However, in our study, improvements were not demonstrated in adverse hospital events, such as pneumonia, acute kidney injury, and urinary tract infection, as well as in-hospital mortality. Many of the benefits of proper nutrition cannot be ascertained until the patient has fully recovered. This study was also incapable of identifying long-term prognoses by reviewing patient records to determine outcomes, such as 1-year mortality or readmission rates. In addition, this study did not reflect the variability in patients’ nutritional supply after discharge. To provide evidence for the significance of adequate nutrition after discharge to long-term prognosis [13-16], an additional follow-up is required for the patient group included in this study.

When developing novel feeding protocols, safety is an important factor. This is particularly true for patients with severe traumatic brain injury or spinal cord trauma, as secondary intestinal obstruction and gastric motility disorders are frequent. Vomiting is the most common safety issue experienced by such patients. Feeding intolerance symptoms, including vomiting, are tallied in nursing records and showed that the number of vomiting and feeding intolerance events did not increase after introduction of the VBF protocol. Although the difference was not statistically significant, there was a small tendency to discontinue EN with the VBF protocol due to these symptoms. However, a recent multi-center, pilot, randomized, controlled trial with a small number of patients reported increased vomiting and pointed out that these issues complicated the protocol [17].

Limitations

This study had some limitations. First, data collection and analysis were conducted retrospectively and were not randomized or blinded. A blinded study design was not possible because bedside nurses recorded the respective changes in feeding rates of patients according to circumstances. Second, the EN products used in the study were not uniform. The total amounts of calories and proteins provided through EN products were used as data, but compositional ingredients can vary from product to product, which might have affected the results. Finally, this study excluded patients during the first 72 hours of their ICU stay. This exclusion most likely did not affect the overall pattern and significance of the data points [18]; however, this could not be proven. To confirm the full effect of tube feeding, patients who were briefly admitted to the ICU were excluded.

Generalizability

Above results can be generalized in the trauma center in other area in Korea with same protocol of the EN.

Conclusion

This study aimed to confirm the validity of a VBF strategy for injured patients admitted to an ICU. The novel protocol increased the initial nutrient supply without increasing the risk of enteral intolerance-related symptoms; however, no improvement in mortality was observed.

None.