The following objectives have been set:
1) To analyze if the administration of higher amount of protein on diet improves protein metabolism by increasing serum protein levels (total proteins, albumin, prealbumin, transferrin and retinol binding protein (RBP)) and NB in critically ill infants.
2) To evaluate the effect of protein supplementation on energy expenditure on these patients.
3) To register possible secondary effects of the administration of protein-enriched and high-enriched protein diet.
This is an open randomized controlled clinical trial. The study was conceived and designed in 2010. It has been retrospectively registered on the Clinical Trials Database (ClinicalTrials.gov) with the registry number NCT03901742. This protocol, version 1.0, was approved on September 30th, 2010. Central ethical approval has been confirmed from the Institutional Review Board of Hospital General Universitario Gregorio Marañón (ref approval no. 2010-022851-47) and recruiting will not begin at other centers in the trial until local ethical approval has been obtained. Informed consent will be obtained from parents before their children are enrolled in the study. A report releasing study results will be submitted for publication in an appropriate journal. This protocol has been written in accordance with the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT). A SPIRIT checklist is provided in Additional file 1.
PICUs from three hospitals in Spain will participate: Hospital General Universitario Gregorio Marañón (Madrid), Hospital Clínico Universitario de Santiago (Santiago de Compostela) and Hospital Universitario Central de Asturias (Oviedo).
The following are the inclusion criteria:
1) Children aged 1 month to 2 years.
2) Children admitted to PICU.
3) Children receiving enteral nutrition with an estimated length of over 72 hours.
Children who met any of the following criteria will be excluded:
1) Age less than 1 month or over 2 years.
2) Diabetes mellitus or any inborn metabolic error.
5) Renal replacement therapy.
6) Children receiving exclusive breastfeeding or in a need of special enteral formula.
After enrolment, the patient will be allocated randomly, in order of recruitment, into one of the three 3 diet groups using a randomized data table generated with EPIDAT 3.1 software. A copy of the randomization list will be securely stored in an envelope located at PICU working area desk drawer, which will be opened after the patient enrollment on the study. Physicians, care givers and investigators will know the allocation prior to the start of enteral feeding.
All patients will receive exclusively enteral nutrition via nasogastric o transpyloric tube. Group Standard Enteral Nutrition (SEN) would be fed exclusively with cow's milk based infant formula (Nidina 1; Nestlé, Barcelona, Spain). Group Protein-enriched Enteral Nutrition (PEN) would be fed exclusively with a polymeric infant formula (Infatrini; Nutricia, Madrid, Spain). Group High Protein-enriched Enteral Nutrition (HPEN) would receive a polymeric infant formula (Infatrini; Nutricia, Madrid, Spain) supplemented with 2.6 g of protein/100 mL of formula. The source of the protein supplement would be a nonhydrolyzed protein cow's milk-based formula (Resource Protein Instant; Nestlé, Barcelona, Spain) (table 1).
Since this is an open-label trial, the assigned diet will be written down on the medical prescription of each patient and will be prepared by the PICU staff at the own unit, using for it the branded bottles where the different formulae are commercialized.
Continuous enteral nutrition will be initiated within the first 24 hours of PICU admission, by transpyloric or nasogastric tube, at a rate of 0.5-1 ml/kg/hour, with increases of 0.5-1 ml/kg every 3-4 hours, if well tolerated, to reach a caloric intake of 60-65 kcal/kg/day, or as needed based on resting energy expenditure measured by indirect calorimetry
Demographic data will be recorded at inclusion: gender, age, weight, height, and diagnosis on admission. The risk of mortality at admission will be calculated using pediatric scales: Pediatric Index of Mortality 2 (PIM2), Pediatric Risk of Mortality (PRISM), and Pediatric Logistic Organ Dysfunction (PELOD).
Blood concentrations of urea, creatinine, total proteins, albumin, prealbumin, transferrin, RBP levels, urinary concentration of urea in 24-hours or isolated urine sample, and energy expenditure, oxygen consumption (VO2) and carbon dioxide production (VCO2) by indirect calorimetry (Datex S5 monitor, E-COVX; GE Healthcare/Datex-Ohmeda, Helsinki, Finland) will be measured at admission and at days 1, 3 and 5-7 after initiation of enteral feeding. Air leaks will be measured using the mechanical ventilator. Calorimetry-derived data will be collected only in patients with tracheal intubation, when air leakage is <10 %, FiO2 less than 80 %, absence of inhaled nitric oxide, sevofluorane or heliox, or connection to ECMO. The collection of indirect calorimetry data will be done over 30 to 120 minutes.
NB will be calculated as: nitrogen intake minus total nitrogen losses. Total nitrogen losses will include total urinary nitrogen and fecal/miscellaneous losses estimated according to the World Health Organization recommendations (29).
Another blood biochemical parameters as glucose, cholesterol, triglycerides, ions and blood gas will also be recorded.
Total daily enteral energy and protein delivery, intravenous albumin infused, and other treatments such as vasoactive drugs, neuromuscular blockers, sedatives and analgesic drugs, diuretics and steroids would be registered.
Protein-enriched diet safety
Enteral complications (constipation, diarrhea, abdominal distension, gastric residue), serum urea and total protein levels, as well as any unexpected adverse event occurring during the trial will be recorded to evaluate the safety of the protein-enriched diet.
1) After 7 days of enteral feeding.
3) If hyperproteinemia higher than 8.5 g/dL is present.
4) If serum urea levels elevates higher than 80 mg/dL without evidence of renal function disturbance or hypercatabolism.
The primary outcome of the study will be the variation of NB from baseline to the study ending and the incidence of hyperproteinemia or uremia causing the need to stop the study.
Secondary outcomes include the variation of plasma protein levels (total proteins, albumin, prealbumin, transferrin and RBP), expenditure energy measured by indirect calorimetry, and the incidence of gastrointestinal complications (abdominal distension, vomiting, diarrhea and excessive gastric residue) and metabolic acidosis.
Trial data will be extracted from the medical history of the patient, registered by investigators on a data collection form, and subsequently recorded on a central database. Each patient will be identified by number of medical history and subject number, so confidentiality of the patient will be kept.
As there are not previous studies reporting expected standard deviations, we use the standardized difference of means for computing the optimal minimum number of patients to include in the trial. The calculation of the sample size has been done with EPIDAT 3.1 software. Considering a significance level of 5% (Type I error), a power of 80% (complementary of the Type II error) and a minimum detectable standardized difference of means of 0.9, we need 30 patients per group (Bonferroni correction included).
We will use an intention-to-treat approach. A descriptive analysis will be performed where quantitative variables will be described by their means and standard deviations or their medians and interquartile ranges, as appropriate. The quantitative ones will be summarized by their absolute and relative frequencies. Parametric and non-parametric tests will be employed for contrasting equality among groups.
Univariate and multivariate mixed models will be used in order to assess the effects size of the different diets (fixed effects) on the patients (random effects) unadjusted and adjusted by potential confounders, respectively. P-values under 5% will be considered statistically significant.