Malnutrition in infants and children with congenital heart defect or disease (CHD) is common and influenced by age, underlying cardiac diagnoses, and presence or absence of congestive heart failure. During the surgical hospitalization period, these children are prone to nutritional deterioration due to:
- Stress of surgery
- Anaesthetic/perfusion techniques
- Postoperative care.
The postoperative clinical course of these infants along with persistent inflammatory catabolic periods contributes to the loss of lean body mass affecting both immune status and hospital outcomes. Prolonged, cumulative caloric and protein deficits occur both before and after staged multiple surgeries with the potential to affect long-term neurological and developmental outcomes. Critically ill infants post-cardiac surgery require specialized nutrition support. Many infants present with feeding and nutrition concerns prior to surgery and following surgery, metabolic dysregulation leads to a high risk of malnutrition.
The goal is to match energy expenditure to the energy provided throughout a complex stay. This can be achieved by estimating the amount of calories needed by an individual using Indirect calorimetry. it is essential for individualized nutrition prescription as body abnormal response and clinical condition vary greatly between children and over the course of each child’s illness to avoid overfeeding of underfeeding the child. This prescription may involve both enteral and parenteral nutrition and incorporate distinct doses of macro and micronutrients.
(A) Enteral nutrition (EN)
This refers to intake of food via the gastrointestinal (GI) tract. The GI tract is composed of the mouth, esophagus, stomach, and intestines. It can also mean nutrition taken through the mouth or through a tube that goes directly to the stomach or small intestine. In order to prevent cumulative nutrient deficits, it is very important to initiate nutrition support as soon as possible post-cardiac surgery. Enteral nutrition has been associated with decreased risk of infection, decreased length of stay, and improved biochemical indices of nutrition status.
Additionally, enteral nutrition offers immunoprotection by reducing the risk of gut atrophy, preventing the loss of the intestinal mucosal barrier, promoting the development of healthy intestinal microflora, and initiating normal feeding patterns. Some infants tolerate early and aggressive progression to full enteral feeds, while others have more complex clinical courses that may impede reaching enteral goals – again, individual differences.
Intuitively, small amounts of EN may be enough for beneficial effects on an infant’s intestinal health and function. Trophic feeds or minimal enteral nutrition has been found to be associated with decreased time to reach full feeds and decreased length of stay when compared to no enteral feeds. Volumes of trophic feeds generally range from 12 to 24 ml/kg/day. Therefore, if tolerance concerns or fluid restrictions prevent delivery of full enteral nutrition, trophic feeds should be considered in an effort to provide immunoprotection to the gut. While enteral feeding may provide benefits, intense monitoring is required for complications such as necrotizing enterocolitis (NEC), which has been associated with higher mortality.
(B) Parenteral Nutrition
As it is not always safe or possible to feed an oxygen-compromised gut, it may become necessary to use TPN to balance the caloric and protein needs during this period to prevent the total depletion of endogenous stores. It is important to remember that compared to enteral nutrition, parenteral nutrition confers a higher risk of infection.
When prescribing and initiating TPN, it is essential to account for all extraneous dextrose infusions containing inotropes, medication, and other drugs as these lines provide a significant amount of glucose (calories) to the infant. Peritoneal dialysis (PD) may also deliver a significant energy source dependent on dextrose strength and dwell times. When these sources of glucose are calculated, the remaining macronutrients can be calculated based on the remaining energy and protein needs. It is rare that a critically ill infant during an acute-phase response requires more than a 4–5 mg/kg/min glucose infusion rate (GIR).
Protein requirements have received considerable discussion in recent years and it is thought that current dosing for infants and children should be increased. This would certainly be true for infants post-cardiac surgery. Current guidelines suggest 2–4 g/kg/day of protein dependent on age during critical illness. It is conceivable that protein requirements are unique and individualized to the infants’ nutritional status and clinical picture. It is imperative to provide protein to prevent lean body mass wasting that can result in poor wound healing, poor immune function, and loss of muscle function. Indeed, adequate protein delivery is considered the most essential nutrition support element during critical illness. A key element to providing adequate protein is to consider potential sources of protein losses from the patient. These can include chest tubes, dialysis, and wounds.
Lipids should be initiated in small doses of 0.5 g fat/kg/ day in non-septic infants and based upon biochemical tolerance.
Cardiac surgical infants experience inflammation, oxidative stress, and immune dysfunction. The combined effect of systemic inflammatory response syndrome (SIRS) and malnutrition distributes micronutrients from the circulation to the tissues for needed immune function and protein synthesis. Selenium is a trace element of critical importance to the antioxidant systems in the body as well as provides immune and anti-inflammatory properties.
In a critically ill infant, both iron deficiency and inflammation contribute to anemia. Acknowledging that excess iron supplementation can potentially induce oxidative stress and provide for bacterial proliferation, excess iron should be discouraged. In the absence of blood transfusion, iron repletion for deficiency should be considered especially in the presence of chronic heart failure as normalization of iron stores may have a beneficial effect on cardiac remodeling and function
Omega-3 Fatty Acids
To newborn infants with CHD, the benefits go beyond the anti-inflammatory effect. The benefits of adequate intake of essential long-chain polyunsaturated fatty acid early in life are well documented and include visual development, related complex brain functions, as well as developmental benefits for growth and immune function. Infants with long stays in the hospital are particularly venerable to n-3 fatty acid deficits especially if there are prolonged periods of NPO and TPN dependence.
The need for individualized nutrition prescription remains critical to the child’s metabolism as the metabolic consequence and clinical circumstance are highly variable between children throughout the course of intensive care. Energy expenditure is highly variable throughout the course of critical illness.
- Energy expenditure cannot accurately be estimated from clinical or biochemical indices.
- Serial measures of energy expenditure using indirect calorimetry are ideal to match energy delivery to requirements and prevent the consequences of over- and underfeeding.
- In the absence of measured energy expenditure, 65–100 % predicted basal metabolic rate should be used as initial target energy prescription and increased as clinical supports are removed for infants post-cardiac surgery.
- Enteral nutrition should be initiated when deemed medically safe for infants post-cardiac surgery.
- An intake of 2–4 g/kg/day protein should be targeted and individualized to age, clinical status, and losses.
- Many barriers to reaching goals for nutrition support exist and attempts should be made to recognize and minimize these where possible.
- Cautious parenteral nutrition prescriptions should consider metabolic dysregulation that can lead to hyperglycemia and hypertriglyceridemia. • Supplementation may be required to provide adequate amounts of vitamin D, selenium, iron, and omega-3 fatty acids.
- Diet and Nutrition in Critical Care by Rajkumar Rajendram, Victor R. Preedy and Vinood B. Patel https://link.springer.com/referencework/10.1007/978-1-4614-7836-2