Lower versus higher dose of enteral caloric intake in adult critically ill patients: a systematic review and meta-analysis

BACKGROUND

There is conflicting evidence about the relationship between the dose of enteral caloric intake and survival in critically ill patients. The objective of this systematic review and meta-analysis is to compare the effect of lower versus higher dose of enteral caloric intake in adult critically ill patients on outcome.

METHODS

We reviewed MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Scopus from inception through November 2015. We included randomized and quasi-randomized studies in which there was a significant difference in the caloric intake in adult critically ill patients, including trials in which caloric restriction was the primary intervention (caloric restriction trials) and those with other interventions (non-caloric restriction trials). Two reviewers independently extracted data on study characteristics, caloric intake, and outcomes with hospital mortality being the primary outcome.

RESULTS

Twenty-one trials mostly with moderate bias risk were included (2365 patients in the lower caloric intake group and 2352 patients in the higher caloric group). Lower compared with higher caloric intake was not associated with difference in hospital mortality (risk ratio (RR) 0.953; 95 % confidence interval (CI) 0.838-1.083), ICU mortality (RR 0.885; 95 % CI 0.751-1.042), total nosocomial infections (RR 0.982; 95 % CI 0.878-1.077), mechanical ventilation duration, or length of ICU or hospital stay. Blood stream infections (11 trials; RR 0.718; 95 % CI 0.519-0.994) and incident renal replacement therapy (five trials; RR 0.711; 95 % CI 0.545-0.928) were lower with lower caloric intake. The associations between lower compared with higher caloric intake and primary and secondary outcomes, including pneumonia, were not different between caloric restriction and non-caloric restriction trials, except for the hospital stay which was longer with lower caloric intake in the caloric restriction trials.

CONCLUSIONS

We found no association between the dose of caloric intake in adult critically ill patients and hospital mortality. Lower caloric intake was associated with lower risk of blood stream infections and incident renal replacement therapy (five trials only). The heterogeneity in the design, feeding route and timing and caloric dose among the included trials could limit our interpretation. Further studies are needed to clarify our findings.

Immunonutrition as an adjuvant therapy for burns

BACKGROUND

With burn injuries involving a large total body surface area (TBSA), the body can enter a state of breakdown, resulting in a condition similar to that seen with severe lack of proper nutrition. In addition, destruction of the effective skin barrier leads to loss of normal body temperature regulation and increased risk of infection and fluid loss. Nutritional support is common in the management of severe burn injury, and the approach of altering immune system activity with specific nutrients is termed immunonutrition. Three potential targets have been identified for immunonutrition: mucosal barrier function, cellular defence and local or systemic inflammation. The nutrients most often used for immunonutrition are glutamine, arginine, branched-chain amino acids (BCAAs), omega-3 (n-3) fatty acids and nucleotides.

OBJECTIVES

To assess the effects of a diet with added immunonutrients (glutamine, arginine, BCAAs, n-3 fatty acids (fish oil), combined immunonutrients or precursors to known immunonutrients) versus an isonitrogenous diet (a diet wherein the overall protein content is held constant, but individual constituents may be changed) on clinical outcomes in patients with severe burn injury.

SEARCH METHODS

The search was run on 12 August 2012. We searched the Cochrane Injuries Group's Specialised Register, The Cochrane Library, MEDLINE (OvidSP), Embase (OvidSP), ISI WOS SCI-EXPANDED & CPCI-S and four other databases. We handsearched relevant journals and conference proceedings, screened reference lists and contacted pharmaceutical companies. We updated this search in October 2014, but the results of this updated search have not yet been incorporated.

SELECTION CRITERIA

Randomised controlled trials comparing the addition of immunonutrients to a standard nutritional regimen versus an isonitrogenated diet or another immunonutrient agent.

DATA COLLECTION AND ANALYSIS

Two review authors were responsible for handsearching, reviewing electronic search results and identifying potentially eligible studies. Three review authors retrieved and reviewed independently full reports of these studies for inclusion. They resolved differences by discussion. Two review authors independently extracted and entered data from the included studies. A third review author checked these data. Two review authors independently assessed the risk of bias of each included study and resolved disagreements through discussion or consultation with the third and fourth review authors. Outcome measures of interest were mortality, hospital length of stay, rate of burn wound infection and rate of non-wound infection (bacteraemia, pneumonia and urinary tract infection).

MAIN RESULTS

We identified 16 trials involving 678 people that met the inclusion criteria. A total of 16 trials contributed data to the analysis. Of note, most studies failed to report on randomisation methods and intention-to-treat principles; therefore study results should be interpreted with caution. Glutamine was the most common immunonutrient and was given in seven of the 16 included studies. Use of glutamine compared with an isonitrogenous control led to a reduction in length of hospital stay (mean stay -5.65 days, 95% confidence interval (CI) -8.09 to -3.22) and reduced mortality (pooled risk ratio (RR) 0.25, 95% CI 0.08 to 0.78). However, because of the small sample size, it is likely that these results reflect a false-positive effect. No study findings suggest that glutamine has an effect on burn wound infection or on non-wound infection. All other agents investigated showed no evidence of an effect on mortality, length of stay or burn wound infection or non-wound infection rates.

AUTHORS' CONCLUSIONS

Although we found evidence of an effect of glutamine on mortality reduction, this finding should be taken with care. The number of study participants analysed in this systematic review was not sufficient to permit conclusions that recommend or refute the use of glutamine. Glutamine may be effective in reducing mortality, but larger studies are needed to determine the overall effects of glutamine and other immunonutrition agents.

Early versus delayed enteral nutrition support for burn injuries

BACKGROUND

A burn injury increases the body's metabolic demands, and therefore nutritional requirements. Provision of an adequate supply of nutrients is believed to lower the incidence of metabolic abnormalities, thus reducing septic morbidity, improving survival rates, and decreasing hospital length of stay. Enteral nutrition support is the best feeding method for patients who are unable to achieve an adequate oral intake to maintain gastrointestinal functioning, however, its timing (i.e. early versus late) needs to be established.

OBJECTIVES

To assess the effectiveness and safety of early versus late enteral nutrition support in adults with burn injury.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library, issue 1, 2006), the Cochrane Injuries Group's Specialised Register, MEDLINE (1966 to May week 1, 2006), EMBASE (1980 to week 17, 2005) and CINAHL (1982 to May week 1, 2006).

SELECTION CRITERIA

We included all randomised controlled trials comparing early enteral nutrition support (within 24 hours of injury) versus delayed enteral support (greater than 24 hours).

DATA COLLECTION AND ANALYSIS

Two authors used standardised forms to independently extract the data. Each trial was assessed for internal validity with differences resolved by discussion.

MAIN RESULTS

A total of three randomised controlled trials were eligible for inclusion in this review. Results of the studies indicate that evidence about the benefit of early enteral nutritional support on standardised clinical outcomes such as length of hospital stay and mortality, remains inconclusive. Similarly, the question of whether early enteral feeding influenced or decreased metabolic rate as documented in part by our included studies, remains uncertain.

AUTHORS' CONCLUSIONS

This systematic review has not found sufficient evidence to support or refute the effectiveness of early versus late enteral nutrition support in adults with burn injury. The trials showed some promising results that would suggest early enteral nutrition support may blunt the hypermetabolic response to thermal injury, but this is insufficient to provide clear guidelines for practice. Further research incorporating larger sample sizes and rigorous methodology that utilises valid and reliable outcome measures, is essential.

Propofol use precludes prescription of estimated nitrogen requirements

The objective was to determine whether reducing enteral nutrition to accommodate 1% Propofol-derived energy results in suboptimal nitrogen prescription. This was a prospective observational study of 85 consecutive patients requiring mechanical ventilation and receiving 1% Propofol. Enteral nutrition prescription often failed to meet nitrogen requirements (<90%, in 50.6%; <80%, in 21.1%), whereas fat provided 51% of total energy input, exceeding 2 g fat/kg/d in 20%. However, gastroparesis was common, resulting in suboptimal nutrition (median of requirements: energy 71%; nitrogen 57%). If energy balance had been strictly maintained, substituting 1% with 2% Propofol would reduce the number of patients failing to meet nitrogen requirements (1% vs 2%: <90%: in 58.8% vs 17.6%, P< .001; <80% in 35.3% vs 4.7%, P< .014). These effects are directly related to the amount of fat delivered with Propofol. Intensive care unit-associated gastroparesis commonly reduces enteral nutrition input. However, even where this is overcome, use of 1% Propofol frequently precludes prescription of estimated nitrogen requirements; either 2% Propofol or a non-Propofol alternative should be considered.

Duration of dysphagic symptoms and swallowing outcomes after thermal burn injury

Levels of swallowing disability, patterns of dysphagia rehabilitation and swallowing outcomes on discharge were retrospectively reviewed for 30 patients with thermal burn injury (with or without inhalation injury), referred to speech pathology services for dysphagia management. The average total surface burn area of the group was 50%. All patients were mechanically ventilated for an average of 24 days, with 80% of patients requiring subsequent tracheostomy. Initial dysphagia assessment occurred approximately 20 days after admission, whereas first safe oral intake was achieved by approximately 30 days. Supplementary nutrition and hydration was necessary for all patients. The time to achieve oral intake without supplementation was 53 days. Outcome measures revealed a significant improvement in swallowing function throughout the duration of inpatient stay, with 90% of patients discharged safely tolerating a normal diet, 6.7% of patients managing soft diet consistencies, and 3.3% managing soft puree consistencies on discharge.