Micronutrients in Critical Illness: Essential and Enigmatic

Micronutrient intake from enteral nutrition in critically ill adults: A systematic review of randomised controlled trials

OBJECTIVES

The primary objective was to compare the intake of important micronutrients provided from enteral nutrition to critically ill patients with the Australia and New Zealand recommended dietary intakes. A secondary objective was to compare the upper levels of intake and investigate prespecified subgroups.

REVIEW METHOD USED

A systematic literature review was performed.

DATA SOURCES

MEDLINE, EMBASE, CINAHL, and CENTRAL were used.

REVIEW METHODS

Databases were searched for randomised controlled trials that investigated an enteral nutrition intervention as the sole source of nutrition, were published in English between January 2000 and January 8th, 2021, and provided data to calculate micronutrient intake. The primary outcome was the % recommended dietary intake. The quality of individual trials was assessed using the Cochrane Risk of Bias Tool. Outcomes are presented as either mean ± standard deviation or median [interquartile range], with a p < 0.05 considered statistically significant.

RESULTS

Thirteen trials were included (n = 1538 patients). Trials investigating hypocaloric nutrition were excluded from the primary outcome assessment (conducted in nine trials (n = 1220)). All nine trials delivered ≥104% of the recommended dietary intakes and <100% of the upper level of intakes of all micronutrients. In subgroup analyses, trials with ≥80% target energy delivered a higher % of the recommended dietary intake of vitamin B12, thiamine, zinc, and vitamin C. Acute Physiology and Chronic Health Evaluation scores ≥20 delivered a higher % of the recommended dietary intake of vitamin B12 and vitamin A. Antioxidant formulas compared with standard formulas delivered a higher % recommended dietary intake of vitamin C and thiamine. In the four trials that investigated hypocaloric feeding compared with control, there was no difference in micronutrient intake. The quality was low.

CONCLUSIONS

Enteral nutrition delivery frequently met the recommended dietary intakes for all micronutrients investigated and did not exceed the upper levels of intake set for health.

PROSPERO REGISTRATION

CRD42020178333.

Micronutrient status during paediatric critical illness: A scoping review

Background

No evidence based recommendations for micronutrient requirements during paediatric critical illness are available, other than those arising from recommended nutrient intakes (RNI) for healthy children and expert opinion.

Objectives

The objective of this review is to examine the available evidence from micronutrient status in critically ill children considering studies which describe 1) micronutrient levels, 2) associations between micronutrient levels and clinical outcome, and 3) impact on clinical outcome with micronutrient supplementation during PICU admission.

Design

Scoping review.

Eligibility criteria

Any study which used a qualitative and quantitative design considering causes and consequences of micronutrient levels or micronutrient supplementation during paediatric critical illness.

Sources of evidence

NICE Healthcare Databases Advanced Search website (https://hdas.nice.org.uk/) was used as a tool for multiple searches, with a content analysis and charting of data extracted.

Results

711 records were identified, 35 were included in the review. Studies evaluated serum micronutrient status was determined on admission day in majority of patients. A content analysis identified (n = 49) initial codes, (n = 14) sub-categories and (n = 5) overarching themes during critical illness, which were identified as: i) low levels of micronutrients, ii) causes of aberrant micronutrient levels, iii) associations between micronutrients levels and outcome, iv) supplementation of micronutrients.

Conclusion

During critical illness, micronutrients should be provided in sufficient amounts to meet reference nutrient intakes for age. Although, there is insufficient data to recommend routine supplementations of micronutrients at higher doses during critical illness, the ‘absence of evidence should not imply evidence of absence’, and well designed prospective studies are urgently needed to elucidate paediatric micronutrient requirements during critical illness. The absence of reliable biomarkers make it challenging to determine whether low serum levels are reflective of a true deficiency or as a result redistribution, particularly during the acute phase of critical illness. As more children continue to survive a PICU admission, particularly those with complex diseases micronutrient supplementation research should also be inclusive of the recovery phase following critical illness.