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

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.

Effects of L-carnitine supplementation on respiratory distress syndrome development and prognosis in premature infants: A single blind randomized controlled trial

The aim of the present study was to investigate the efficacy of L-carnitine therapy on the occurrence and prognosis of respiratory distress syndrome (RDS). A single blind, randomized controlled trial study was conducted on 130 infants with gestational ages of 28-36 weeks. Infants were assigned to experimental groups (groups 1 and 2) and control groups (groups 3 and 4). Groups 1 and 3 consisted of infants with RDS, and groups 2 and 4 groups were composed of infants without RDS. The experimental groups were treated with carnitine. No statistically significant differences in serum carnitine levels were detected between the study and the control groups on day 1 of treatment (P=0.06). However, on day 7 of treatment, serum carnitine levels in the experimental groups were significantly increased (P=0.02), as compared with the control groups. The surfactant requirement value, which is how many rounds of surfactant therapy were required, was 1.56±0.97 in group 1, and 2.12±0.99 in group 3 (P<0.001). The mean duration of mechanical ventilation required was 3.04±3.60 days in group 1, and 4.73±5.63 days in group 3 (P<0.001). The present results indicate that carnitine supplementation in premature infants with RDS may help to increase carnitine levels, thus decreasing the duration of mechanical ventilation and surfactant requirement.

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.

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.