Myocardial substrates in children with congenital heart disease: relationship to substrate supply, age, growth and desaturation

A scoping review: urinary markers of metabolic maturation in infants with CHD and the relationship to growth

BACKGROUND

Growth failure in infants born with CHD is a persistent problem, even in those provided with adequate nutrition.

OBJECTIVE

To summarise the published data describing the change in urinary metabolites during metabolic maturation in infants with CHD and identify pathways amenable to therapeutic intervention.

DESIGN

Scoping review.

ELIGIBILITY CRITERIA

Studies using qualitative or quantitative methods to describe urinary metabolites pre- and post-cardiac surgery and the relationship with growth in infants with CHD.

SOURCES OF EVIDENCE

NICE Healthcare Databases website was used as a tool for multiple searches.

RESULTS

347 records were identified, of which 37 were duplicates. Following the removal of duplicate records, 310 record abstracts and titles were screened for inclusion. The full texts of eight articles were reviewed for eligibility, of which only two related to infants with CHD. The studies included in the scoping review described urinary metabolites in 42 infants. A content analysis identified two overarching themes of metabolic variation predictive of neurodevelopmental abnormalities associated with anaerobic metabolism and metabolic signature associated with the impact on gut microbiota, inflammation, energy, and lipid digestion.

CONCLUSION

The results of this scoping review suggest that there are considerable gaps in our knowledge relating to metabolic maturation of infants with CHD, especially with respect to growth. Surgery is a key early life feature for CHD infants and has an impact on the developing biochemical phenotype with implications for metabolic pathways involved in immunomodulation, energy, gut microbial, and lipid metabolism. These early life fingerprints may predict those individuals at risk for neurodevelopmental abnormalities.

Hyperlactatemia: An Update on Postoperative Lactate

While hyperlactatemia in postoperative cardiac surgery patients was once believed to solely reflect hypoperfusion, either from the accumulated "oxygen debt" during bypass or ongoing inadequate perfusion, our understanding of lactate generation, clearance, and management has evolved. A contemporary understanding of lactate balance is critical to the management of the postoperative patient with hyperlactatemia. In this review, we summarize the current understanding of lactate metabolism in pediatric patients following cardiac surgery and highlight two types of hyperlactatemia: type A, which is secondary to inadequate oxygen delivery and tissue hypoxia, and type B, which in postoperative pediatric cardiac surgery patients largely reflects increased glycolysis driven by the stress response. Both types may coexist; thus, it is imperative that providers first assess the patient for evidence of hypoperfusion. In patients with evidence of adequate perfusion, a type B component is often associated with a concomitant balanced (normal anion gap) metabolic acidosis and hyperglycemia. These patients will benefit from a more nuanced approach to their type B hyperlactatemia, as many will have a benign course and may be managed expectantly.

Lactate and acid base as a hemodynamic monitor and markers of cellular perfusion

BACKGROUND

: The intra- and postoperative monitoring of lactate and acid-base has been advocated in pediatric cardiac critical care as surrogate markers of cardiac output, oxygen delivery, and cellular perfusion. Many clinicians use lactate and base excess routinely as markers of tissue perfusion and to assess the effectiveness of their intervention. This review discusses the strengths and weaknesses of using these measurements in pediatric cardiac critical care.

METHODOLOGY

: A search of MEDLINE, EMBASE, PubMed, and the Cochrane Database was conducted to find controlled trials of lactate and base excess. Adult and pediatric data were considered. Guidelines published by the Society of Critical Care Medicine, the American Heart Association, the American Academy of Pediatrics, and the International Liaison Committee on Resuscitation were reviewed including further review of references cited.

RESULTS AND CONCLUSIONS

: Many factors other than tissue hypoxia may contribute to hyperlactemia in critical illness. Although the presence of hyperlactemia on admission appears to be associated with intensive care unit mortality and morbidity in some retrospective analyses, significant overlap between survivors and nonsurvivors means that nonsurvivors cannot be predicted from admission lactate measurement. Persistently elevated postoperative lactate is associated with increased morbidity and mortality in the pediatric cardiac population. To date there is no randomized control trial of goal-directed therapy in adult or pediatric cardiac care that includes normalization of lactate as a target. Overall equivalent time measurements of base excess, anion gap, and pH have a low predictive value for morbidity and mortality in children after cardiac surgery. Lactate is one of a cluster of markers of cellular perfusion and oxygen delivery. Alone, as a single measurement, it has minimal predictive value and is nondiscriminatory for survival.