Evidence for the safety of ascorbic acid administration to the premature infant

Antioxidants: Role the in prevention and treatment of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is one of the major causes of chronic respiratory diseases among infants. Both pharmacological and nonpharmacological approaches have been proposed for its management. Since oxidative stress is known to play a pivotal role in the pathogenesis of BPD, it is reasonable to consider the potential of antioxidant strategies in the prevention and treatment of this condition. Indeed, antioxidants can prevent or inhibit substrate oxidation. Some studies have evaluated the efficacy of the exogenous administration of vitamins and micronutrients in reducing the propagation of free radicals through their scavenging capacity. Nonetheless, encouraging preclinical results did not translate into effective preventive and/or therapeutic interventions. This narrative review evaluates the current evidence about the antioxidants that are potentially useful for preventing and treating BPD and explores the most relevant issues affecting their implementation in clinical practice, as well as their associated evidence gaps and research limitations.

Metabolic resuscitation in pediatric sepsis: a narrative review

Sepsis, defined as infection with associated organ dysfunction, accounts for most childhood deaths due to infection globally. Evidence for the optimal support of children with septic shock refractory to the initial sepsis management bundle remains minimal. There is an urgent need for more effective interventions. Administration of hydrocortisone in children with septic shock might fasten shock resolution, and has been shown to dampen the systemic host immune response, augment adrenergic effects, and support the stress response. Ascorbic acid (vitamin C) is one of the most powerful naturally occurring antioxidants and has beneficial effects on multiple pathways which are severely deranged during septic shock. A regimen combining hydrocortisone, ascorbic acid, and thiamine termed "metabolic resuscitation" or "HAT therapy" has been tested in large trials in critically ill adults with sepsis with conflicting results. Available information on intravenous ascorbic acid indicates an excellent safety profile even at very high doses both in adults and children. Given the pharmacological properties and beneficial effects shown both in vitro and in animal studies, and its safety profile, ascorbic acid either as a single therapy or as part of HAT treatment represents a promising candidate for future pediatric sepsis treatments. While pediatric age groups may be more susceptible to ascorbic acid deficiency during sepsis, there is a lack of high-quality trial data on HAT therapy in this age group. A single centre retrospective study identified potential for mortality benefit in children with septic shock, and the results from a randomized controlled pilot trial are being awaited. It is imperative for pediatric research on ascorbic acid and HAT in children with sepsis to critically investigate key questions related to pharmacology, dosing, timing, feasibility, safety, effects on short- and long-term outcomes, and generalisability in view of the global burden of sepsis.

Efficacy and Safety of Parenteral High-Dose Vitamin C Therapy in Pediatric Patients: A Scoping Review

OBJECTIVES

Recently, several adult trials have investigated the potential benefit of high-dose vitamin C therapy in critically ill patients. In pediatric patients, little is known on the efficacy, safety, and risk of high-dose vitamin C therapy. We aimed to review the efficacy and potential harm associated with high-dose vitamin C treatment.

DATA SOURCES

We searched MEDLINE, EMBASE, Cochrane Library, and National Institute of Health Clinical Trials Register.

STUDY SELECTION

We included studies in neonatal and pediatric patients who received IV or intra-arterial high-dose vitamin C (ascorbic acid) defined as greater than or equal to 75 mg/kg/d.

DATA EXTRACTION

Two independent investigators screened articles and extracted data.

DATA SYNTHESIS

We found 1,364 articles, assessed 193 full texts for eligibility, and identified 12 eligible studies. These studies included 855 patients, with 194 receiving high-dose vitamin C. The age of patients who received high-dose vitamin C ranged from 2 hours after delivery to 8.4 years (median 2.4 yr), and the vitamin C dose ranged from 100 to 1,500 mg/kg/d (median 260.5 mg/kg/d). Four studies were double-blind randomized controlled trials, and no clinical efficacy outcome was reported in favor of or against vitamin C. Furthermore, no adverse event or signal of harm was reported with high-dose vitamin C.

CONCLUSIONS

In 12 studies with 194 children treated with parenteral high-dose vitamin C, there was no evidence of clinical efficacy or inferior clinical outcomes in double-blind randomized controlled trials, and no reported harmful effects. These findings justify further investigations of this treatment in children.

New antioxidant drugs for neonatal brain injury

The brain injury concept covers a lot of heterogeneity in terms of aetiology involving multiple factors, genetic, hemodynamic, metabolic, nutritional, endocrinological, toxic, and infectious mechanisms, acting in antenatal or postnatal period. Increased vulnerability of the immature brain to oxidative stress is documented because of the limited capacity of antioxidant enzymes and the high free radicals (FRs) generation in rapidly growing tissue. FRs impair transmembrane enzyme Na⁺/K⁺-ATPase activity resulting in persistent membrane depolarization and excessive release of FR and excitatory aminoacid glutamate. Besides being neurotoxic, glutamate is also toxic to oligodendroglia, via FR effects. Neuronal cells die of oxidative stress. Excess of free iron and deficient iron/binding metabolising capacity are additional features favouring oxidative stress in newborn. Each step in the oxidative injury cascade has become a potential target for neuroprotective intervention. The administration of antioxidants for suspected or proven brain injury is still not accepted for clinical use due to uncertain beneficial effects when treatments are started after resuscitation of an asphyxiated newborn. The challenge for the future is the early identification of high-risk babies to target a safe and not toxic antioxidant therapy in combination with standard therapies to prevent brain injury and long-term neurodevelopmental impairment.

Ascorbic acid combined with ibuprofen in hypoxic ischemic encephalopathy: a randomized controlled trial

OBJECTIVE

Free oxygen radicals and proinflammatory cytokines are important causes for brain injury in neonates with hypoxic ischemic encephalopathy (HIE). Our objectives were to test the hypothesis that a combination of antioxidants (ascorbic acid) and anti-inflammatory agents (ibuprofen) can ameliorate the brain injury in HIE and improve neurodevelopmental outcomes when given to term infants immediately after birth.

STUDY DESIGN

In a prospective, randomized, double-blinded controlled trial, 60 asphyxiated term infants were assigned to one of two groups, intervention and control. The intervention group (n=30) received intravenous ascorbic acid and oral ibuprofen for 3 days; and the control group (n=30) received similar volumes of a placebo. We measured a panel of cytokines at enrollment and administered the treatment drugs within 2 h after birth. Neurological evaluations and developmental screenings were performed for all survivors at 6 months of age.

RESULT

The Intervention and Control groups did not differ in the severity of HIE at enrollment, the concentrations of IL-1 beta and IL-6, the incidence of mortality (37 vs 33%), the incidence of neurological abnormalities at hospital discharge (47 vs 55%) and the incidence of developmental delay at 6 months of age (32 vs 40%), respectively. None of the observed complications were related to intervention. Serum interleukin (IL)-1 beta and IL-6 concentrations correlated positively with the severity of HIE at birth (P<0.01), whereas only serum IL-6 correlated with neurodevelopmental outcome at 6 months (P<0.001).

CONCLUSION

Early administration of ascorbic acid and ibuprofen did not affect outcomes in infants with perinatal asphyxia. This study does not explain whether our intervention was not effective in blocking free radicals and inflammatory cytokines, if the dosing and route of administration were inadequate, or if other mediators existed that could have a more powerful role in brain injury during hypoxia-ischemia.

Intraventricular ascorbic acid administration decreases hypoxic-ischemic brain injury in newborn rats

Neuronal cell damage following hypoxic-ischemic (HI) brain injury is partly caused by production of free radicals and reactive oxygen species (ROS). Ascorbic acid (AA) is a potent antioxidant, which scavenges various types of ROS. Some studies have shown that it is neuroprotective, however, the issue is still controversial. In this study, we examined the effect of intraventricular AA administration on immature HI brain using the Rice-Vannucci model. After unilateral carotid artery ligation under isoflurane anesthesia, 7-day-old rat pups received varying concentrations of AA (0.04, 0.2, 1 and 5 mg/kg) by intraventricular injection and were exposed to 8% oxygen for 90 min. Vehicle controls received an equal volume of phosphate saline buffer. We assessed the neuroprotective effect of AA at 7 days post-HI. The percent brain damage measured by comparing the wet weight of the ligated side of hemisphere with that of contralateral one was reduced in both 1 and 5 mg/kg groups but not in either 0.04 or 0.2 mg/kg groups compared to vehicle controls (5 mg/kg 16.0 +/- 4.3%, 1 mg/kg 10.9 +/- 5.0%, vs. controls 36.7 +/- 3.6%, P < 0.05). Macroscopic evaluation of brain injury revealed the neuroprotective effect of AA in both 1 and 5 mg/kg groups (5 mg/kg 1.1 +/- 0.4, 1 mg/kg 0.4 +/- 0.3, vs. controls 2.9 +/- 0.3, P < 0.05). Western blots of fodrin on the ligated side also showed that AA significantly suppressed 150/145-kDa bands of fodrin breakdown products, which suggested that AA suppressed activation of calpain. Neuropathological quantitative analysis of cell death revealed that 1 mg/kg of AA injection significantly reduced the number of necrotic cells in cortex, caudate putamen, thalamus and hippocampus CA1, whereas that of apoptotic cells was only reduced in cortex. These findings show that intraventricular AA injection is neuroprotective after HI in immature rats.

Vitamin C supplementation in very preterm infants: a randomised controlled trial

OBJECTIVE

To determine whether regulating vitamin C (ascorbic acid: AA) intake to achieve higher or lower plasma concentrations was associated with improved clinical outcome.

DESIGN

A double blind, randomised controlled trial.

SETTING

Neonatal intensive care unit at Christchurch Women's Hospital.

PATIENTS

Infants with birth weight <1500 g or gestation <32 weeks, admitted to the unit within 48 hours of birth.

INTERVENTION

Infants were randomised to one of three protocols with regard to AA supplementation for the first 28 days of life: group LL received low supplementation throughout; group LH received low until day 10 and then high: group HH received high throughout.

MAIN OUTCOME MEASURES

Primary outcome measures were oxygen requirement at 28 days and 36 weeks postmenstrual age, total days supplemental oxygen, and retinopathy of prematurity. AA concentrations were measured at study entry (day 2), and days 10, 21, and 28.

RESULTS

A total of 119 infants were enrolled over 24 months (mean gestation 28.4 weeks; birth weight 1161 g). Six infants died, and these had significantly higher AA concentrations before randomisation than surviving infants (116 micromol/l (95% confidence interval 90 to 142) v 51 micromol/l (45 to 58), p<0.0001). There were no significant differences in primary outcomes between the groups. However, the proportion of surviving infants with an oxygen requirement at 36 weeks postmenstrual age in group HH (19%) was half that in group LL (41%) (p=0.06).

CONCLUSIONS

In a randomised controlled trial, no significant benefits or harmful effects were associated with treatment allocation to higher or lower AA supplementation throughout the first 28 days of life.

Nutrient requirements for preterm infant formulas

Achieving appropriate growth and nutrient accretion of preterm and low birth weight (LBW) infants is often difficult during hospitalization because of metabolic and gastrointestinal immaturity and other complicating medical conditions. Advances in the care of preterm-LBW infants, including improved nutrition, have reduced mortality rates for these infants from 9.6 to 6.2% from 1983 to 1997. The Food and Drug Administration (FDA) has responsibility for ensuring the safety and nutritional quality of infant formulas based on current scientific knowledge. Consequently, under FDA contract, an ad hoc Expert Panel was convened by the Life Sciences Research Office of the American Society for Nutritional Sciences to make recommendations for the nutrient content of formulas for preterm-LBW infants based on current scientific knowledge and expert opinion. Recommendations were developed from different criteria than that used for recommendations for term infant formula. To ensure nutrient adequacy, the Panel considered intrauterine accretion rate, organ development, factorial estimates of requirements, nutrient interactions and supplemental feeding studies. Consideration was also given to long-term developmental outcome. Some recommendations were based on current use in domestic preterm formula. Included were recommendations for nutrients not required in formula for term infants such as lactose and arginine. Recommendations, examples, and sample calculations were based on a 1000 g preterm infant consuming 120 kcal/kg and 150 mL/d of an 810 kcal/L formula. A summary of recommendations for energy and 45 nutrient components of enteral formulas for preterm-LBW infants are presented. Recommendations for five nutrient:nutrient ratios are also presented. In addition, critical areas for future research on the nutritional requirements specific for preterm-LBW infants are identified.

Ascorbic-acid transporter Slc23a1 is essential for vitamin C transport into the brain and for perinatal survival

The only proven requirement for ascorbic acid (vitamin C) is in preventing scurvy, presumably because it is a cofactor for hydroxylases required for post-translational modifications that stabilize collagen. We have created mice deficient in the mouse ortholog (solute carrier family 23 member 1 or Slc23a1) of a rat ascorbic-acid transporter, Svct2 (ref. 4). Cultured embryonic fibroblasts from homozygous Slc23a1(-/-) mice had less than 5% of normal ascorbic-acid uptake. Ascorbic-acid levels were undetectable or markedly reduced in the blood and tissues of Slc23a1(-/-) mice. Prenatal supplementation of pregnant females did not elevate blood ascorbic acid in Slc23a1(-/-) fetuses, suggesting Slc23a1 is important in placental ascorbic-acid transport. Slc23a1(-/-) mice died within a few minutes of birth with respiratory failure and intraparenchymal brain hemorrhage. Lungs showed no postnatal expansion but had normal surfactant protein B levels. Brain hemorrhage was unlikely to be simply a form of scurvy since Slc23a1(-/-) mice showed no hemorrhage in any other tissues and their skin had normal skin 4-hydroxyproline levels despite low ascorbic-acid content. We conclude that Slc23a1 is required for transport of ascorbic acid into many tissues and across the placenta. Deficiency of the transporter is lethal in newborn mice, thereby revealing a previously unrecognized requirement for ascorbic acid in the perinatal period.

Vitamin C function and status in chronic disease

Vitamin C is an essential dietary nutrient required as a co-factor for many enzymes, and humans are among the few animals that lack the ability to synthesize the compound from glucose. The reduced form of the vitamin, ascorbic acid, is an especially effective antioxidant owing to its high electron-donating power and ready conversion back to the active reduced form. Concentrations of the vitamin in body tissues and fluids are regulated through interactions of intestinal absorption, cellular transport, and excretion. The amount of vitamin C needed to prevent scurvy is very small and easily obtained in nearly all Western diets. There is great interest in the clinical roles of vitamin C because of evidence that oxidative damage is a root cause of, or at least associated with, many diseases. Population studies show that individuals with high intakes of vitamin C have lower risk of a number of chronic diseases, including heart disease, cancer, eye diseases, and neurodegenerative conditions. However, these results may simply reflect a more healthful diet or lifestyle for individuals with a high vitamin C intake. At present, data from controlled clinical trials have not established that higher intakes of vitamin C alone will help prevent chronic degenerative diseases. However, the evidence that ascorbic acid acts as an important antioxidant in many body tissues is convincing. The new higher Recommended Dietary Allowance (RDA) for vitamin C of 75 mg for women and 90 mg for men is, for the first time, based on the vitamin's role as an antioxidant as well as protection from deficiency. In healthy people, amounts greater than the RDA do not appear to be helpful. Vitamin C nutriture may be more important for people with certain diseases or conditions. High intakes of the vitamin are generally well tolerated; a Tolerable Upper Level was recently set at 2 g based on gastrointestinal upset that sometimes accompanies excessive intakes.

Thiamine, riboflavin, pyridoxine, and vitamin C status in premature infants receiving parenteral and enteral nutrition

BACKGROUND

There is a paucity of data about water soluble vitamin status in low birthweight infants. Therefore, the authors' objective was to assess current feeding protocols.

METHODS

The authors measured serum concentrations for riboflavin, pyridoxine, and vitamin C and functional assays for thiamine and riboflavin longitudinally in 16 premature infants (birthweight, 1,336 +/- 351 g; gestational age, 30 +/- 2.5 weeks) before receiving nutrition (time 1, 2 +/- 1 days), during supplemental or parenteral nutrition (time 2, 16 +/- 10 days) and while receiving full oral feedings (time 3, 32 +/- 15 days). In plasma, vitamin C was measured colorimetrically, and riboflavin and pyridoxine were measured using high-performance liquid chromatography. The erythrocyte transketolase test as a functional evaluation of thiamine and the erythrocyte glutathione reductase test for riboflavin were measured colorimetrically.

RESULTS

At time 1, nutrient intake of vitamins were negligible because infants were receiving intravenous glucose and electrolytes only. Intakes differed between time 2 and time 3 for thiamine (510 +/- 280 and 254 +/- 115 microg. kg-1. d-1, respectively), riboflavin (624 +/- 305 and 371 +/- 193 microg. kg-1. d-1, respectively), and pyridoxine (394 +/- 243 and 173 +/- 85 microg/100 kcal, respectively), but not for vitamin C (32 +/- 17 and 28 +/- 12 mg. kg-1. d-1, respectively). Blood levels at times 1, 2, and 3 were for thiamine (4.9 +/- 2.7%, 3.3 +/- 6.6%, and 4.1 +/- 9% erythrocyte transketolase test, respectively), riboflavin (0.91 +/- 0.31, 0.7 +/- 0.3, 0.91 +/- 0.18 erythrocyte glutathione reductase test, respectively), riboflavin (19.5 +/- 17, 23.3 +/- 8.6, 17.6 +/- 10 ng/mL, respectively), pyridoxine (32 +/- 25, 40 +/- 16, 37 +/- 26 ng/mL, respectively), and vitamin C (5.2 +/- 3, 5 +/- 2.2, 10 +/- 5 microg/mL, respectively) and did not differ at those times.

CONCLUSIONS

Current intakes of these vitamins, except for possibly vitamin C, during parenteral and enteral nutrition seem to result in adequate plasma concentrations and normal functional indices.

Strategies for prevention of neonatal chronic lung disease

Chronic lung disease (CLD) of prematurity remains a substantial problem despite modern perinatal and neonatal care. CLD remains related to gestational age and lung immaturity, although it has become clear that severe initial lung disease is not a prerequisite for CLD to develop. Attempts to prevent CLD to date have not adequately addressed the multifactorial nature of the complex pathophysiology that leads to CLD. Thus, results have been modest at best. Prevention of CLD will require a multifaceted approach with specific interventions and care practices focused on different aspects of the pathway that leads to CLD. This review considers new information related to causation of CLD and the magnitude of the effect of prevention strategies tested to date. This article also advances the hypothesis that CLD is preventable with a global strategy of minimizing inciting events, optimizing management, and specific therapies aimed at intrinsic vulnerabilities.

Vitamin metabolism and requirements in the micropremie

Vitamin metabolism and requirements are reviewed for the micropremie (1000 Pounds g birthweight), for parenteral and enteral feedings. Recommendations are presented in table format. Human milk fortifiers and special formulas for the preterm infant are reviewed. For parenteral nutrition, only MVI Pediatric is currently available in the United States. Two millimeters per kilogram is recommended for the micropremie as the most satisfactory method of providing supplemental vitamins in total parenteral nutrition solutions.