Effect of supplementary parenteral nutrition on glucose and lipid metabolisms, risk of infection, and prognosis in critically ill patients with low body weight

Introduction

Nutritional support plays a critically important role in the treatment of critically ill patients. The patient’s body is featured by high decomposition and high metabolism under severe stress, and proper nutritional support can meet the body’s requirements on energy and nutrients, improve gastrointestinal function, promote recovery, and eventually improve prognosis. However, gastrointestinal intolerance or even interruption during enteral nutrition (EN) often leads to failure in achieving the nutrition targets. Supplemental parenteral nutrition (SPN) is a reasonable supplement to EN. In our current study, we explored the role of SPN in treating low-weight critically ill patients by focusing on its impacts on energy supply and clinical outcomes.

Methods

Subjects

Critically ill patients who were admitted to the intensive care unit (ICU) of our hospital from May 2017 to December 2018 were enrolled in this study. The inclusion criteria were as follows: (I) aged ≥18 years; (II) with an APACHE II score of ≥10; (III) with a body mass index (BMI) of <22; (IV) with an expected duration of mechanical ventilation of >72 h; (V) expected to live more than 7 days; (VI) with gastrointestinal function but unable to eat independently; (VII) with a nutritional risk screening (NRS) score of ≥3; and (VIII) having received EN within 48 h after ICU admission but less than 60% of the prescribed nutrition goal had been reached after three days of EN. The exclusion criteria included: (I) unstable vital signs; (II) in the end stage of chronic diseases; (III) with the contraindications (e.g., intestinal obstruction, intestinal perforation, etc.) of EN; and (IV) with accompanying nutritional and metabolic diseases.

The study was approved by the Ethics Committee of the Sixth Hospital affiliated to Sun Yat-sen University, and the ethical approval number is 2017SYSUSH-003.

Grouping and nutritional support

The subjects were divided into the EN group and SPN group by using the random number table. According to the nutritional support protocol, the calorie target was 20–25 kcals/kg, and the protein target was 1.2–1.5 g/kg. In the EN group, the EN solution (short-peptide EN formula) (Leskon, Xi’an, China) was fed through an EN pump. Gastric juice was collected every 4 hours to judge if there was any gastric retention. Frequency of defecation, fecal characteristics and amount, abdominal distension, gastric retention, and gastrointestinal bleeding, if any, were observed. The dose of the nutrient solution was adjusted based on the patient’s tolerance. In the SPN group, a pre-mixed nutrient solution (containing glucose, fat emulsion, amino acids, vitamins, and trace elements, which were prepared in specific ratios and filled in a 3-L bag) was applied based on EN.

Observations

NRS was performed at admission, and the nutritional status and biochemical parameters of the patients were recorded at admission and 10 days after treatment. The length of stay (LOS) in ICU and hospital, duration of mechanical ventilation, as well as ICU-related infections, ICU mortality, and hospital mortality, were recorded.

Statistical analysis

Statistical analysis was performed using the SPSS 17.0 software package. Measurement data are presented as (x¯±SD). The means were compared using a t-test, and Welch's t-test was performed for unequal variances. Comparison of count data was performed using the chi-square test, with a P value of less than 0.05 being considered statistically significant.

Results

General data

A total of 118 patients were enrolled in this study, among whom six patients stopped EN due to gastrointestinal bleeding and/or refractory diarrhea, and four patients gave up treatment halfway. Thus, 108 patients entered the final analysis, with 54 patients in each group. The baseline data of these two groups showed no significant difference (all P>0.05) (Table 1).

Actual nutrient intakes

In the EN group, the actual protein intake accounted for (64.08±26.11)% of the protein required, and the actual calorie intake accounted for (69.03±27.76)% of the calories needed. In the SPN group, the actual protein intake accounted for (85.97±18.88)% of the necessary protein, significantly higher than that in EN group (t=4.992, P=0.000); the exact calorie intake accounted for (94.58±12.67)% of the calories required, substantially higher than that in EN group (t=6.218, P=0.000).

Changes in biochemical parameters one week after treatment

One week after treatment, the albumin level was significantly higher in SPN group than in EN group (P<0.05); however, the levels of urea nitrogen, alanine aminotransferase, fasting blood glucose, and triglyceride showed no significant changes in both groups (all P>0.05) (Table 2).

Clinical outcomes

The duration of mechanical ventilation, LOS in ICU, and LOS in hospital in the SPN group were significantly shorter than those in the EN group (all P<0.05). However, there was no significant difference in ICU mortality and hospital mortality (both P>0.05) (Table 3).

Infection complications

Nosocomial infection occurred in 7 cases in the SPN group, and the incidence rate was 12.96%, which was significantly lower than that in the EN group (P<0.05). The composition of the pathogens showed no significant difference between two groups (P>0.05) (Table 4).

Discussion

Nutritional support is an integral part of the multidisciplinary treatment of critically ill patients. In these patients, a series of metabolic and physiological changes occur under severe stress conditions, causing abnormal carbohydrate, fat, and protein metabolism. Proper nutritional support is vital to avoid malnutrition, reduce protein catabolism, and even improve prognosis (1). EN is more consistent with human physiology and helps to maintain the structure and function of the intestines; meanwhile, it is less expensive and with fewer metabolism-related complications. Thus, EN is the preferred nutritional support method in clinical practice. However, EN alone often can not meet the energy needs of critically ill patients due to stress and/or poor intestinal function and thus may affect organ function and even prognosis (2,3). Reasonable SPN can compensate for EN; however, few pieces of literature have described its impacts on energy intake/metabolism and prognosis in low-weight critically ill patients.

The primary goal of SPN is to improve the nutritional status of patients and increase calorie and protein intakes. In our current study, the calories and protein intakes were significantly higher in the SPN group than in EN group, suggesting SPN can increase the inputs of energy and protein and improve the nutritional status (4). Similarly, a multicenter prospective randomized controlled study also found that SPN helped to increase caloric and protein intakes in patients, and albumin level in the SPN group was higher than that in the EN group after nutritional support (5). Decreased glucose oxidation and utilization (6), insulin resistance, gluconeogenesis, and many other conditions under severe stress often lead to stress-induced hypertension, while PN can easily cause acute and chronic metabolic complications such as blood sugar fluctuations, hyperlipidemia, and hypercalciuria. In our current study, the glucose infusion rate during PN was strictly controlled at 4–5 mg/(kg·min) and fasting blood glucose and triglyceride levels showed no significant difference between SPN group and EN group, indicating that SPN has no remarkable impact on blood sugar in low-weight critically ill patients.

Also in our current study, the SPN group had significantly shorter duration of mechanical ventilation, LOS in ICU, and LOS in hospital and considerably lower incidences of infection complications, suggesting SPN can shorten the mechanical ventilation time and hospital stay, improve the quality of life, and lower the rates of complications associated with ICU infections. The body of critically ill patients is under stress status, which is featured by increased protein catabolism and decreased immunity, and delayed and/or insufficient nutritional supplementation will affect the structures and functions of organs and even lead to multiple organ dysfunction and death. Also, the strength and endurance of respiratory muscles decrease during malnutrition, which increases the risk of respiratory failure. While the standard caloric and protein targets may not be achieved by EN alone (7), excessive EN will exceed the endurance of the digestive system, increase the burden of the gastrointestinal tract, and finally worsen the stress-related gastric mucosal lesions, weaken the gastric mucosal barrier function, and injure the gastrointestinal hormone- and immunoglobulin-secreting functions. Early SPN can help reduce the incidences of infection complications and improve prognosis (7). SPN increases energy and protein intake, improves nutritional status and ensures the proper regulations of metabolism, physiology, and immune by the body, which facilitates tissue repair, improves gastric mucosal barrier function and micro-ecological environment, lowers the incidences of infection complications, and eventually shortens the duration of mechanical ventilation and LOS in ICU (8). However, it has also been argued that early SPN did not significantly reduce hospitalization time or increase 60-day survival rate and even worsened the prognosis (9,10), which might be explained by patient heterogeneity and SPN timing (11) and/or by variations in energy and protein demands, intestinal function, and SPN dose and compositions (12).

In summary, SPN can shorten the duration of mechanical ventilation, ICU stays, and hospital visits in low-weight critically ill patients, reduce the incidence of infectious complications, and supplement the energy and protein supply when EN cannot meet the needs of the body.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the Guest Editors (Changhua Zhang and Liang Li) for the series “Nutritional Support for Digestive Surgery” published in Digestive Medicine Research. The article has undergone external peer review.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/dmr.2019.06.03). The series “Nutritional Support for Digestive Surgery” was commissioned by the editorial office without any funding or sponsorship. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the Ethics Committee of the Sixth Hospital affiliated to Sun Yat-sen University, and the ethical approval number is 2017SYSUSH-003. Informed consent was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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