Role of L-carnitine in apnea of prematurity: a randomized, controlled trial

Guidelines for parenteral nutrition in preterm infants: The American Society for Parenteral and Enteral Nutrition

BACKGROUND

Parenteral nutrition (PN) is prescribed for preterm infants until nutrition needs are met via the enteral route, but unanswered questions remain regarding PN best practices in this population.

METHODS

An interdisciplinary committee was assembled to answer 12 questions concerning the provision of PN to preterm infants. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) process was used. Questions addressed parenteral macronutrient doses, lipid injectable emulsion (ILE) composition, and clinically relevant outcomes, including PNALD, early childhood growth, and neurodevelopment. Preterm infants with congenital gastrointestinal disorders or infants already diagnosed with necrotizing enterocolitis or PN-associated liver disease (PNALD) at study entry were excluded.

RESULTS

The committee reviewed 2460 citations published between 2001 and 2023 and evaluated 57 clinical trials. For most questions, quality of evidence was very low. Most analyses yielded no significant differences between comparison groups. A multicomponent oil ILE was associated with a reduction in stage 3 or higher retinopathy of prematurity (ROP) compared to an ILE containing 100% soybean oil. For all other questions, expert opinion was provided.

CONCLUSION

Most clinical outcomes were not significantly different between comparison groups when evaluating timing of PN initiation, amino acid dose, and ILE composition. Future clinical trials should standardize outcome definitions to permit statistical conflation of data, thereby permitting more evidence based recommendations in future guidelines. This guideline has been approved by the ASPEN 2022-2023 Board of Directors.

Intravenous Carnitine Administration in Addition to Parenteral Nutrition With Lipid Emulsion May Decrease the Inflammatory Reaction in Postoperative Surgical Patients

BACKGROUND

A prospective randomized study was performed to investigate the validity of intravenous carnitine administration during postoperative parenteral nutrition (PN) with lipid emulsion.

METHODS

Patients undergoing surgery for gastric or colorectal cancer were enrolled in the study and were randomly divided into two groups (n = 8 in each group): 1) group L, who received a peripheral PN (PPN) solution of 7.5% glucose, 30% amino acid, and 20% lipid emulsion; and 2) group LC, who received the same PPN solution, as well as carnitine intravenously. PPN was performed from postoperative day (POD) 1 to POD4. Clinical and laboratory parameters were compared between the two groups; statistical significance was set at P < 0.05.

RESULTS

Serum carnitine concentrations were significantly higher in group LC on POD3 (P < 0.01) and POD7 (P = 0.01). Postoperative changes in laboratory parameters and morbidity were comparable between the two groups. However, the decrease in C-reactive protein from POD3 to POD7 was significantly greater in group LC than in group L (P = 0.011).

CONCLUSION

The results show that intravenous carnitine administration in addition to PN is safe and may be beneficial for recovery from postoperative inflammatory reactions.

The Use of Carnitine in Pediatric Nutrition

Carnitine is synthesized endogenously from methionine and lysine in the liver and kidney and is available exogenously from a meat and dairy diet and from human milk and most enteral formulas. Parenteral nutrition (PN) does not contain carnitine unless it is extemporaneously added. The primary role of carnitine is to transport long-chain fatty acids across the mitochondrial membrane, where they undergo beta-oxidation to produce energy. Although the majority of patients are capable of endogenous synthesis of carnitine, certain pediatric populations, specifically neonates and infants, have decreased biosynthetic capacity and are at risk of developing carnitine deficiency, particularly when receiving PN. Studies have evaluated for several decades the effects of carnitine supplementation in pediatric patients receiving nutrition support. Early studies focused primarily on the effects of supplementation on markers of fatty acid metabolism and nutrition markers, including weight gain and nitrogen balance, whereas more recent studies have evaluated neonatal morbidity. This review describes the role of carnitine in metabolic processes, its biosynthesis, and carnitine deficiency syndromes, as well as reviews the literature on carnitine supplementation in pediatric nutrition.

Evaluation of serum carnitine levels for pediatric patients receiving carnitine-free and carnitine-supplemented parenteral nutrition

PURPOSE

Carnitine is a carrier molecule transporting long-chain fatty acids (LCFAs) into the mitochondria for fatty acid β-oxidation. The purpose of this study is to evaluate the role of carnitine supplementation in parenteral nutrition (PN) within the pediatric population. Our goal was to determine a weight range for which empiric carnitine supplementation is justified and to determine a weight range at which a carnitine level should first be drawn to confirm a deficiency prior to supplementation. Secondarily, we tried to determine a relationship among carnitine deficiency, hypoglycemia, and hypertriglyceridemia.

METHODS

This was a retrospective observational study to evaluate 2 groups of pediatric patients (weighing 0.68 kg to 60 kg) who were NPO and receiving PN. The first group of patients (n = 454) received carnitine supplementation (15 mg/kg/day) upon initiation of PN. The second group (n = 299) did not receive carnitine supplementation until they were determined to have a carnitine deficiency.

RESULTS

The data indicated that 82% of the patients weighing less than 5 kg were deficient. Patients weighing more than 5 kg had serum carnitine levels within the normal range. Therefore, patients receiving PN and weighing less than 5 kg should be supplemented with carnitine. Comparison of triglyceride, glucose, and carnitine showed no statistically significant difference (P = .1936).

CONCLUSION

Patients weighing more than 5 kg should have serum carnitine levels drawn within 7 days to determine whether supplementation is needed. There is no statistical correlation among carnitine deficiency, hypoglycemia, and hypertriglyceridemia.

Neuroprotective effects of L-carnitine against oxygen-glucose deprivation in rat primary cortical neurons

Purpose

Hypoxic-ischemic encephalopathy is an important cause of neonatal mortality, as this brain injury disrupts normal mitochondrial respiratory activity. Carnitine plays an essential role in mitochondrial fatty acid transport and modulates excess acyl coenzyme A levels. In this study, we investigated whether treatment of primary cultures of rat cortical neurons with L-carnitine was able to prevent neurotoxicity resulting from oxygen-glucose deprivation (OGD).

Methods

Cortical neurons were prepared from Sprague-Dawley rat embryos. L-Carnitine was applied to cultures just prior to OGD and subsequent reoxygenation. The numbers of cells that stained with acridine orange (AO) and propidium iodide (PI) were counted, and lactate dehydrogenase (LDH) activity and reactive oxygen species (ROS) levels were measured. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and the terminal uridine deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay were performed to evaluate the effect of L-carnitine (1 µM, 10 µM, and 100 µM) on OGD-induced neurotoxicity.

Results

Treatment of primary cultures of rat cortical neurons with L-carnitine significantly reduced cell necrosis and prevented apoptosis after OGD. L-Carnitine application significantly reduced the number of cells that died, as assessed by the PI/AO ratio, and also reduced ROS release in the OGD groups treated with 10 µM and 100 µM of L-carnitine compared with the untreated OGD group (P<0.05). The application of L-carnitine at 100 µM significantly decreased cytotoxicity, LDH release, and inhibited apoptosis compared to the untreated OGD group (P<0.05).

Conclusion

L-Carnitine has neuroprotective benefits against OGD in rat primary cortical neurons in vitro.

Carnitine supplementation in premature neonates: Effect on plasma and red blood cell total carnitine concentrations, nutrition parameters and morbidity

BACKGROUND & AIMS

Carnitine may be considered conditionally essential in the neonatal population. The purpose of this study was to evaluate the effects of long-term carnitine supplementation on total carnitine status and morbidity in premature neonates.

METHODS

In this prospective, randomized, placebo-controlled, double-blinded study, premature neonates received carnitine supplementation (20mg/kg/day) or placebo. Plasma (nmol/ml) and red blood cell (RBC) (nmol/mg hemoglobin) total carnitine concentrations, 24-h nitrogen excretion, intake and weight, and respiratory, gastroesophageal, and infectious morbidity were assessed.

RESULTS

Twenty-nine neonates (13 placebo, 16 carnitine; 27+/-2 weeks gestation; 976+/-259g birthweight) were studied for up to 8 weeks. Plasma total carnitine concentrations exceeded the reference range in the carnitine group (weeks 1-8); however, concentrations did not reach reference range until week 4 in the placebo group. RBC total carnitine concentrations increased, but remained below reference range in both the carnitine (weeks 1-6) and placebo (weeks 1-8) groups. Carnitine group neonates regained their birthweight more rapidly than placebo group neonates (day of life 11.8+/-6 vs. 16.9+/-6.3, P=0.034). In addition, percent periodic breathing calculated from cardiopulmonary trend monitor data (weeks 1-8) was lower in the carnitine group (0.4+/-0.9 vs. 1.4+/-1.9, P=0.014). There was no difference with respect to other markers of respiratory, gastroesophageal and infectious morbidity or nitrogen balance.

CONCLUSIONS

Carnitine supplementation at 20mg/kg/day results in increased plasma and RBC total carnitine concentrations, has a positive effect on catch-up growth, and may improve periodic breathing in premature neonates.

Lack of effect of L-carnitine supplementation on weight gain in very preterm infants

OBJECTIVE

Carnitine transfer across the placenta occurs predominantly during the third trimester. Unless L-carnitine is provided, very preterm infants develop carnitine deficiency. Although breast milk and infant formulas contain L-carnitine, parenteral nutrition solutions do not routinely provide L-carnitine. We hypothesized that prolonged L-carnitine supplementation in very preterm infants would improve weight gain and shorten length of stay in the hospital.

STUDY DESIGN

The study was a double-blind parallel placebo-controlled randomized clinical trial. Eligible patients were <29 weeks of gestation, <72 hours of age, and did not have a potentially life-threatening congenital malformation or hereditary metabolic disorder. Patients were stratified by gestational age (23 to 25(6/7) and 26 to 28(6/7) weeks), and randomized to receive, either L-carnitine at a dose of 50 mumol/kg/day, or placebo. Carnitine was provided intravenously until the infants tolerated 16 ml/day of feeds. The sample size was calculated to have 80% power to detect a 10% increase in weight gain from birth until 36 weeks of postmenstrual age or discharge from the hospital. Secondary outcome variables included food efficiency (defined as weight gain divided by caloric intake), weight gain at 4 weeks of age, time to regain birth weight and length of stay.

RESULTS

Among the 63 infants enrolled in the trial, 32 were randomized to L-carnitine and 31 to placebo. L-Carnitine supplementation did not significantly affect average daily weight gain from birth until 36 weeks or hospital discharge, or any of the secondary outcome variables.

CONCLUSION

Prolonged supplementation of L-carnitine did not improve long-term weight gain in very preterm infants.

Carnitine supplementation for preterm infants with recurrent apnea

BACKGROUND

Apnea of prematurity is a common problem in preterm infants in the neonatal intensive care setting (NICU), often delaying their discharge home or transfer to a step down unit. Premature infants are at increased risk of carnitine deficiency. Carnitine supplementation has been used for both prevention and treatment of apnea.

OBJECTIVES

To determine whether treatment with carnitine will reduce the frequency of apnea, the duration of ventilation and the duration of hospital stay in preterm infants with recurrent apnea.

SEARCH STRATEGY

Computerised searches were carried out by two reviewers independently. Searches were made of MEDLINE (1966 to May 2004), EMBASE (1980 to May 2004), CINAHL (1982-2004 June 2004,1st week), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2004), abstracts of annual meetings of the Society for Pediatric Research (1995-2004), and contacts were made with the subject experts.

SELECTION CRITERIA

Only randomized or quasi-randomized treatment trials of preterm infants with a diagnosis of recurrent apnea of prematurity were considered. Trials were included if they involved treatment with carnitine compared to placebo or no treatment, and measured at least one of the following outcomes: failure of resolution of apneas, the duration of ventilation and the duration of hospital stay.

DATA COLLECTION AND ANALYSIS

Two reviewers evaluated the papers for inclusion criteria and quality. Corresponding authors were contacted for further information where needed.

MAIN RESULTS

No eligible trials were identified.

REVIEWERS' CONCLUSIONS

Despite the plausible rationale for the treatment of apnea of prematurity with carnitine, there are insufficient data to support its use for this indication. Further studies are needed to determine the role of this treatment in clinical practice.

Role of carnitine supplementation in apnea of prematurity: a systematic review

OBJECTIVE

To determine the role of carnitine supplementation in premature infants on apnea of prematurity, length of ventilation and duration of hospital stay.

METHODS

Two reviewers independently conducted a literature search for relevant studies. No language restrictions were applied. Decisions to include studies for the review, and methodological quality of the included studies were assessed in duplicate based on predetermined criteria.

RESULTS

Three studies met the selection criteria (reproducibility-kappa 0.76+/-SE 0.122). One study was later excluded. Both included studies were randomized double-blind placebo control prevention trials among babies <1500 g of weight. There was no difference among the groups for outcomes of bedside nurse recorded frequency of apnea episodes, continuous objective recording of apnea, length of ventilation (WMD -3.24 days, 95% CI -8.39, 1.92) or length of hospital stay (WMD -5.4 days, 95% CI -15.53, 4.72).

CONCLUSION

Present evidence does not support the regular use of carnitine for the prevention of apnea of prematurity.

Sleep and breathing disturbances in infancy and early childhood

The nature of sleep-related breathing problems varies with age. Ventilatory function may be compromised at the level of the brainstem, the autonomic nerves, or the upper airway musculature. These disorders are state-dependent, being impacted by both rapid eye movement and non-rapid eye movement sleep, and also by the degree of maturation of the nervous system. Many are treatable. An understanding of the molecular basis of these disorders is just now becoming apparent.

L-carnitine reduces brain injury after hypoxia-ischemia in newborn rats

Perinatal hypoxia-ischemia remains a significant cause of neonatal mortality and neurodevelopmental disability. Numerous lines of evidence indicate that cerebral ischemic insults disrupt normal respiratory activity in mitochondria. Carnitine (3-hydroxy-4-N-trimethylammonium-butyrate) has an essential role in fatty acid transport in the mitochondrion and in modulating potentially toxic acyl-CoA levels in the mitochondrial matrix. There are no naturally occurring esterases available to reduce the accumulation of acyl-CoA but this process can be overcome by exogenous carnitine. We used a newborn rat model of perinatal hypoxia-ischemia to test the hypothesis that treatment with l-carnitine would reduce the neuropathologic injury resulting from hypoxia-ischemia in the developing brain. We found that treatment with l-carnitine during hypoxia-ischemia reduces neurologic injury in the immature rat after both a 7- and 28-d recovery period. We saw no neuroprotective effect when l-carnitine was administered after hypoxia-ischemia. Treatment with d-carnitine resulted in an increase in mortality during hypoxia-ischemia. Carnitine is easy to administer, has low toxicity, and is routinely used in neonates as well as children with epilepsy, cardiomyopathy, and inborn errors of metabolism. l-Carnitine merits further investigation as a treatment modality for the asphyxiated newborn or as prophylaxis for the at-risk fetus or newborn.