Influence on retrolental fibroplasia of intramuscular vitamin E administration during respiratory distress syndrome

Effects of Antioxidants in Human Milk on Bronchopulmonary Dysplasia Prevention and Treatment: A Review

Bronchopulmonary dysplasia (BPD) is a severe chronic lung illness that affects neonates, particularly premature infants. It has far-reaching consequences for infant health and their families due to intractable short- and long-term repercussions. Premature infant survival and long-term quality of life are severely harmed by BPD, which is characterized by alveolarization arrest and hypoplasia of pulmonary microvascular cells. BPD can be caused by various factors, with oxidative stress (OS) being the most common. Premature infants frequently require breathing support, which results in a hyperoxic environment in the developing lung and obstructs lung growth. OS can damage the lungs of infants by inducing cell death, inhibiting alveolarization, inducing inflammation, and impairing pulmonary angiogenesis. Therefore, antioxidant therapy for BPD relieves OS and lung injury in preterm newborns. Many antioxidants have been found in human milk, including superoxide dismutase, glutathione peroxidase, glutathione, vitamins, melatonin, short-chain fatty acids, and phytochemicals. Human milk oligosaccharides, milk fat globule membrane, and lactoferrin, all unique to human milk, also have antioxidant properties. Hence, human milk may help prevent OS injury and improve BPD prognosis in premature infants. In this review, we explored the role of OS in the pathophysiology of BPD and related signaling pathways. Furthermore, we examined antioxidants in human milk and how they could play a role in BPD to understand whether human milk could prevent and treat BPD.

Vitamin E and preterm infants

In evaluating vitamin E (VE) nutritional status of preterm infants, it is essential that any data should be compared with those of healthy term infants, and never with those of adults. Moreover, it should be evaluated in terms of gestational age (GA), not birth weight (BW), because placental transfer of most nutrients from mother to fetus is dependent on GA, not BW. Judging from the limited data during the last 75 years, there was no significant correlation between GA and VE concentrations in circulation or in the red blood cells (RBCs), leukocytes, and buccal mucosal cells. In addition, the oxidizability of polyunsaturated fatty acids (PUFAs) in plasma or RBCs, as targets for protection by VE chain-breaking ability, was lower in preterm infants. However, because of the minimal information available about hepatic VE levels, which is considered a key determinant of whole body VE status, the decision on whether VE status of preterm infants is comparable with that of term infants should be postponed. Clinical trials of VE supplementation in preterm infants were repeatedly undertaken to investigate whether VE reduces severity or inhibits development of several diseases specific to preterm infants, namely retinopathy of prematurity (ROP), bronchopulmonary dysplasia (BPD), and germinal matrix hemorrhage - intraventricular hemorrhage (GMH-IVH). Most of these trials resulted in a misfire, with a few exceptions for IVH prevention. However, almost all these studies were performed from 1980s to early 1990s, in the pre-surfactant era, and the study populations were composed of mid-preterm infants with GAs of approximately 30 weeks (wks). There is considerable difference in 'preterm infants' between the pre- and post-surfactant eras; modern neonatal medicine mainly treats preterm infants of 28 wks GA or less. Therefore, these results are difficult to apply in modern neonatal care. Before considering new trials of VE supplementation, we should fully understand modern neonatal medicine, especially the recent method of oxygen supplementation. Additionally, a deeper understanding of recent progress in pathophysiology and therapies for possible target diseases is necessary to decide whether VE administration is still worth re-challenging in modern neonatal intensive care units (NICUs). In this review, we present recent concepts and therapeutic trends in ROP, BPD, and GMH-IVH for those unfamiliar with neonatal medicine. Numerous studies have reported the possible involvement of reactive oxygen species (ROS)-induced damage in relation to supplemental oxygen use, inflammation, and immature antioxidant defense in the development of both BPD and ROP. Various antioxidants effectively prevented the exacerbation of BPD and ROP in animal models. In the future, VE should be re-attempted as a complementary factor in combination with various therapies for BPD, ROP, and GMH-IVH. Because VE is a natural and safe supplement, we are certain that it will attract attention again in preterm medicine.

Retinopathy of Prematurity

Retinopathy of prematurity (ROP), formerly called retro-lental fibroplasia (RLF), has increased in the 1980s due to a high incidence of premature, low birthweight infants. Apparently, oxygen administration alone does not account for all these ROP babies. Birth-weight, gestational age, and duration of administration of oxygen are primary contributors to ROP development. The stages of severity range from no visual damage to total blindness. Treatments are either pharmacological or surgical. Vitamin E therapy, photocoagulation procedures, cryotherapy, scleral buckling procedures, and vitrectomy are common treatments, but none is totally successful in ameliorating this condition. The educational problems of children with ROP parallel those of other visually impaired children, with deficits found primarily in exploration, mobility, and language. Referral to early intervention programs can provide a comprehensive structured learning situation and support to the entire family.

Update on Vitamin E and Its Potential Role in Preventing or Treating Bronchopulmonary Dysplasia

Vitamin E is obtained only through the diet and has a number of important biological activities, including functioning as an antioxidant. Evidence that free radicals may contribute to pathological processes such as bronchopulmonary dysplasia (BPD), a disease of prematurity associated with increased lung injury, inflammation and oxidative stress, led to trials of the antioxidant vitamin E (α-tocopherol) to prevent BPD with variable results. These trials were all conducted at supraphysiologic doses and 2 of these trials utilized a formulation containing a potentially harmful excipient. Since 1991, when the last of these trials was conducted, both neonatal management strategies for minimizing oxygen and ventilator-related lung injury and our understanding of vitamin E isoforms in respiratory health have advanced substantially. It is now known that there are differences between the effects of vitamin E isoforms α-tocopherol and γ-tocopherol on the development of respiratory morbidity and inflammation. What is not known is whether improvements in physiologic concentrations of individual or combinations of vitamin E isoforms during pregnancy or following preterm birth might prevent or reduce BPD development. The answers to these questions require adequately powered studies targeting pregnant women at risk of preterm birth or their premature infants immediately following birth, especially in certain subgroups that are at increased risk of vitamin E deficiency (e.g., smokers). The objective of this review is to compile, update, and interpret what is known about vitamin E isoforms and BPD since these first studies were conducted, and suggest future research directions.

Vitamin D and regulation of vascular cell function

Vitamin D deficiency is linked to pathogenesis of many diseases including cardiovascular, cancer, and various eye diseases. In recent years, important roles for vitamin D in regulation of immune function, inflammation, angiogenesis, and aging have been demonstrated. Thus, vitamin D and its analogs have been evaluated for the treatment of various types of cancer and chronic diseases. We have previously shown that the active form of vitamin D [1,25(OH)₂D₃] is a potent inhibitor of angiogenesis. This activity is consistent with the important role proposed for vitamin D and its analogs in the mitigation of tumor growth through inhibition of angiogenesis. Here, we review the important nutritional value of vitamin D and the abnormalities linked to its deficiency. We will explore its potential role as a regulator of angiogenesis and vascular cell function and the role vitamin D receptor (VDR) expression plays in these activities during vascular development and neovascularization. Our studies have established an important role for 1,25(OH)₂D₃ and VDR in the regulation of perivascular supporting cell function. In addition, the interaction of 1,25(OH)₂D₃ and VDR is essential for these activities and inhibition of neovascularization. Delineating the signaling pathways involved and identification of genes that are the target of 1,25(OH)₂D₃ regulation in vascular cells will allow us to identify novel pathways that are targets for regulation of vascular function and angiogenesis.

Pharmacologic interventions for the prevention and treatment of retinopathy of prematurity

Retinopathy of prematurity (ROP), a significant morbidity in prematurely born infants, is the most common cause of visual impairment and blindness in children and persists till adulthood. Strict control of oxygen therapy and prevention of intermittent hypoxia are the keys in the prevention of ROP, but pharmacologic interventions have decreased risk of ROP. Various drug classes such as methylxanthines (caffeine), VEGF inhibitors, antioxidants, and others have decreased ROP occurrence. The timing of pharmacologic intervention remains unsettled, but early prevention rather than controlling disease progression may be preferred. These drugs act through different mechanisms, and synergistic approaches should be considered to maximize efficacy and safety.

Interventions To Prevent Retinopathy of Prematurity: A Meta-analysis

CONTEXT

The effectiveness of many interventions aimed at reducing the risk of retinopathy has not been well established.

OBJECTIVE

To estimate the effectiveness of nutritional interventions, oxygen saturation targeting, blood transfusion management, and infection prevention on the incidence of retinopathy of prematurity (ROP).

DATA SOURCES

A comprehensive search of several databases was conducted, including Medline, Embase, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Scopus through March 2014.

STUDY SELECTION

We included studies that evaluated nutritional interventions, management of supplemental oxygen, blood transfusions, or infection reduction and reported the incidence of ROP and mortality in neonates born at <32 weeks.

DATA EXTRACTION

We extracted patient characteristics, interventions, and risk of bias indicators. Outcomes of interest were any stage ROP, severe ROP or ROP requiring treatment, and mortality.

RESULTS

We identified 67 studies enrolling 21 819 infants. Lower oxygen saturation targets reduced the risk of developing any stage ROP (relative risk [RR] 0.86, 95% confidence interval [CI], 0.77-0.97) and severe ROP or ROP requiring intervention (RR 0.58, 95% CI, 0.45-0.74) but increased mortality (RR 1.15, 95% CI, 1.04-1.29). Aggressive parenteral nutrition reduced the risk of any stage ROP but not severe ROP. Supplementation of vitamin A, E, or inositol and breast milk feeding were beneficial but only in observational studies. Use of transfusion guidelines, erythropoietin, and antifungal agents were not beneficial.

LIMITATIONS

Results of observational studies were not replicated in randomized trials. Interventions were heterogeneous across studies.

CONCLUSIONS

At the present time, there are no safe interventions supported with high quality evidence to prevent severe ROP.

Risk factors for acute retinopathy of prematurity

We prospectively studied the risk factors and the incidence of retinopathy of prematurity (ROP) in 195 consecutive preterm infants. Birth weight and duration of mechanical ventilation were the only factors that were significantly associated with the incidence of ROP. While indomethacin increases the risk of developing ROP, maternal antenatal steroids have a protective effect against the development of severe stages of ROP. The presence of intraventricular hemorrhage increases the risk of severe ROP.

Risk factors for acute retinopathy of prematurity

We prospectively studied the risk factors and the incidence of retinopathy of prematurity (ROP) in 195 consecutive preterm infants. Birth weight and duration of mechanical ventilation were the only factors significantly associated with the incidence of ROP. While indomethacin increases the risk of developing ROP, maternal antenatal steroids have a protective effect against the development of severe stages of ROP. The presence of intraventricular hemorrhage increases the risk of severe ROP.

Effect of dexamethasone therapy on serum vitamin E concentrations in premature infants with bronchopulmonary dysplasia

OBJECTIVE

To investigate the effect of dexamethasone therapy on serum vitamin E concentrations in premature infants with bronchopulmonary dysplasia.

STUDY DESIGN

A total of 10, 24 to 29 weeks' gestational age, infants enrolled in a prospective study designed to evaluate the effect of dexamethasone on lipid intolerance were eligible for the study. Eight of these 10 infants had serum vitamin E concentrations measured simultaneously with serum triglyceride concentrations before the start of dexamethasone therapy (baseline) and within 5 days of the initiation of dexamethasone therapy. Charts were reviewed for vitamin E intake at baseline and on dexamethasone therapy for each of these eight infants.

RESULTS

All eight infants had physiological serum vitamin E concentrations (1 to 3 mg/dl) at baseline, while six of eight infants had pharmacological serum vitamin E concentrations (> or =3 mg/dl) on dexamethasone therapy. All infants with an increase in serum vitamin E concentration also had a simultaneous increase in serum triglyceride concentrations with a significant correlation between vitamin E and triglyceride concentrations (Spearman's rho=0.92). There was a significant difference in mean serum vitamin E concentration between baseline and post-dexamethasone therapy (P=0.01, Wilcoxon's signed-rank test). There was no significant difference in vitamin E intake between baseline and post-dexamethasone therapy.

CONCLUSION

Dexamethasone therapy in premature infants induces significant increase in serum vitamin E concentrations to pharmacological levels independent of vitamin E intake.

Vitamin E supplementation for prevention of morbidity and mortality in preterm infants

BACKGROUND

Treating very low birth weight (VLBW) infants with pharmacologic doses of vitamin E as an antioxidant agent has been proposed for preventing or limiting retinopathy of prematurity, intracranial hemorrhage, hemolytic anemia, and chronic lung disease. However, excessive doses of vitamin E may result in side effects.

OBJECTIVES

The aim of this systematic review was to assess the effects of vitamin E supplementation on morbidity and mortality in preterm infants.

SEARCH STRATEGY

We searched MEDLINE (October 2002), EMBASE (March 2002), the Cochrane Controlled Trials Register (CCTR) from the Cochrane Library, 2003, Issue 1, and personal files for clinical trials assessing vitamin E in preterm infants.

SELECTION CRITERIA

We selected trials analyzing primary outcomes (mortality or combined long-term morbidity) or secondary outcomes (other morbidity) in infants with gestational age less than 37 weeks or birth weight less than 2500 grams. The intervention was allocation to routine supplementation with vitamin E in the treatment group versus placebo, no treatment or another type, dose or route of administration of vitamin E.

DATA COLLECTION AND ANALYSIS

We used standard methods of the Cochrane Collaboration and of the Cochrane Neonatal Review Group.

MAIN RESULTS

Twenty-six randomized clinical trials fulfilled entry criteria. No study assessed combined long-term morbidity. Routine vitamin E supplementation significantly reduced the risk of germinal/intraventricular hemorrhage (typical relative risk [RR] 0.85, 95% confidence interval [CI] 0.73, 0.99), increased the risk of sepsis (typical RR 1.52, CI 1.13, 2.04) and increased hemoglobin concentration by a small amount, but did not significantly affect mortality and other morbidity. In VLBW infants, vitamin E supplementation increased the risk of sepsis, and reduced the risk of severe retinopathy and blindness among those examined. Subgroup analyses in VLBW infants showed (1) an association between serum tocopherol levels greater than 3.5 mg/dl and increased risk of sepsis and reduced risk for severe retinopathy among those examined; and (2) an association between intravenous, high-dose administration of vitamin E and increased risk of sepsis.

REVIEWER'S CONCLUSIONS

Vitamin E supplementation in preterm infants reduced the risk of intracranial hemorrhage but increased the risk of sepsis. In very low birth weight infants it increased the risk of sepsis, and reduced the risk of severe retinopathy and blindness among those examined. Evidence does not support the routine use of vitamin E supplementation by intravenous route at high doses, or aiming at serum tocopherol levels greater than 3.5 mg/dl.

The management of retinopathy of prematurity

Retinopathy of prematurity (ROP) is a major problem in both highly developed countries and countries with emerging technology. The incidence of ROP has been stable over the last 2 decades despite improvements in neonatology. Threshold ROP occurs in about 5% of premature infants in the US with birthweights <1.25kg. Despite treatment, a sizable minority will become blind (up to 20 to 30%). The pathophysiology of ROP can be separated into 2 phases. Phase I is hyperoxia-vasocessation. Phase II is hypoxia-vasoproliferation. The former occurs immediately following premature birth. The provision of supplemental oxygen causes retinal hyperoxia, a down regulation of vascular endothelial growth factor (VEGF) and a consequent cessation of normal retinal vascularisation. Systemic factors and increasing retinal metabolic demands cause a shift to phase II when a relative retinal hypoxia develops. This hypoxia stimulates VEGF production, leading to renewed vascularisation. This can be the resumption of normal vascularisation or abnormal neovascularisation, depending on local retinal responses. The management of ROP begins with a reliable evidence-based screening protocol. All interested parties must cooperate in developing and implementing foolproof screening protocols. Hospital officials, nursery personnel, neonatologists and ophthalmologists all have areas of responsibility in ensuring adequate screening. ROP management involves prevention, interdiction and correction. Prevention includes: adequate prenatal care which minimises premature birth, and appropriate systemic intensive care which lessens the tissue hyperoxia/hypoxia swings. Pharmacological vitamin E supplementation has largely been abandoned and ambient light reduction has been shown to be ineffective. The value of inositol supplementation and angiogenesis inhibitors in preventing ROP is presently under investigation. Interdiction concentrates on ablation of the peripheral avascular retina, thus dramatically decreasing VEGF production. Both cryotherapy and laser photocoagulation are effective; however, unfortunately, poor outcomes persist despite treatment. Supplemental oxygen administration has so far proven ineffective in limiting ROP progression. Finally, correction focuses on vitrectomy/retinal detachment repair. While anatomically successful, this procedure is often unsuccessful in terms of restoration of vision (<5% success rate). In conclusion, despite improvements in neonatology, ROP, potentially leading to blindness, continues to be a common problem associated with prematurity. Future management success must concentrate on discovering new modes of treatment, especially prevention.

Results of screening low-birth-weight infants for retinopathy of prematurity

Retinopathy of prematurity (ROP) continues to be an important cause of potentially preventable blindness worldwide. The pattern of visual impairment from ROP in some middle-income countries--high rates affecting larger and more mature infants--resembles that seen in more developed countries two decades ago and has been called a "third epidemic" of the disease. Expert bodies in the United Kingdom and the United States have recently issued new guidelines for screening for ROP that utilize both birth weight and gestational age criteria. Studies in both countries suggest these criteria might be further revised to decrease time spent on screening without missing any significant disease. Population-based follow-up studies of extremely preterm infants suggest that although more preterm infants are surviving, with adequate screening and treatment, rates of blindness from ROP may be declining. Further information on the longer-term impact of ROP comes from a number of studies and particularly the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity (CRYO-ROP) study. The risk of both myopia and strabismus is increased with any and each higher stage of ROP. Evidence is emerging that laser therapy for threshold disease may be associated with better visual outcome than cryotherapy, although complications following the former remain a concern. The fight against ROP may be enhanced by new information on the pathogenesis, including possible genetic predisposition and the role of vascular endothelial growth factor.

Intraventricular hemorrhage: emphasis on prevention

Germinal matrix/intraventricular hemorrhage is a common type of cerebral injury in premature newborns. Based on the improved understanding of underlying pathogenetic mechanisms, numerous interventional strategies for prevention have been proposed. This article summarizes and evaluates the efficacy and safety of major interventions that are currently under consideration for the prevention of germinal matrix/intraventricular hemorrhage.

Vitamin E prophylaxis to reduce retinopathy of prematurity: a reappraisal of published trials

OBJECTIVE

We conducted a meta-analysis of the published randomized clinical trials of vitamin E prophylaxis designed to reduce retinopathy of prematurity (ROP) to determine whether increased serum concentrations of vitamin E reduced the incidence of severe, threshold (Stage 3+) ROP in the very low birth weight (VLBW) infant subset.

STUDY DESIGN

Among the six trials considered eligible for analyses, the incidence for all stages of ROP and for Stage 3+ ROP was computed for all randomly assigned infants (intention-to-treat analysis) and for those infants completing the trials. Odds ratios (ORs) and pooled estimates for event rate reductions (and the respective 95% confidence intervals [CIs]) were calculated for these outcome end points.

RESULTS

There were 704 VLBW infants in the vitamin E prophylaxis groups and 714 in control groups; 536 (76.1%) infants in the vitamin E and 551 (77.2%) in the control groups completed the trials. In all trials the mean serum vitamin E concentrations were within or above the physiologic range in the vitamin-treated groups and at or below the physiologic ranges in the control groups. The overall incidence of any stage ROP was similar between the groups: 39.8% in the vitamin E group and 43.5% in the control group. The overall incidence for Stage 3+ ROP was lower in the vitamin E-treated groups than in the control group (2.4% in vitamin E vs 5.3% in control). The pooled OR for developing Stage 3+ ROP with vitamin E prophylaxis was 0.44 (95% CI, 0.21, 0.81, p < 0.02). The reciprocal of the pooled estimate of mean risk reduction (2.8%, 95% CI: 0.55%, 5.1%) for Stage 3+ ROP revealed that on average, vitamin E prophylaxis given to 35 VLBW infants would prevent one case of threshold, Stage 3+ ROP.

CONCLUSIONS

Considering that there was a 52% reduction in the incidence of Stage 3+ ROP, we suggest that the role of vitamin E in reducing severe ROP be re-evaluated. We could not assess the adverse effect rates from vitamin E therapy in the trials analyzed; therefore, we recommend a well-controlled and focused trial in which the issues of benefit, adverse effects, and cost can be assessed with vitamin E prophylaxis in extremely low birth weight (< 1000 gm) infants.

Severe retinopathy of prematurity in infants with birth weights less than 1250 grams: incidence and outcome of treatment with pharmacologic serum levels of vitamin E in addition to cryotherapy from 1985 to 1991

OBJECTIVE

To determine the effect of vitamin E prophylaxis and treatment on the sequelae of severe (threshold) retinopathy of prematurity (ROP) in infants treated with cryotherapy at Pennsylvania Hospital from 1985 to 1991.

STUDY DESIGN

Beginning on day 0, all infants with birth weights < or = 1250 gm received supplements of vitamin E using standard preparations. Serum E levels of 23 to 58 mumol/L (1 to 2.5 mg/dl) were targeted for infants with immature retinal vasculature or ROP of stage 2 or less in severity, and levels of 58 to 81 mumol/L (2.5 to 3.5 mg/dl) for infants with prethreshold ROP. At diagnosis of threshold ROP, treatment with a parenteral investigational new drug preparation of alpha-tocopherol was begun to raise serum levels to the pharmacologic range (93 to 116 mumol/L or 4 to 5 mg/dl). Within 3 days of diagnosis, and at the discretion of the retinal specialist, one or both eyes were treated with cryotherapy. Visual outcome at 4 years was compared with the 42-month outcome reported for eyes in the infants randomly assigned to treatment in the 1986-1987 Multicenter Trial of Cryotherapy for ROP (CRYO-ROP).

RESULTS

Threshold ROP developed in 22 of 450 surviving infants (age 3 months). All were treated with pharmacologic serum levels of vitamin E; 17 infants were also treated with cryotherapy (10 in one eye and 7 in both eyes). These 17 infants, in comparison with infants in the CRYO-ROP trial (n = 187), were at least at equal risk for poor visual outcome on the basis of birth weight, gestational age, the percentage of zone 1 ROP, and mean interval from appearance of ROP to diagnosis of prethreshold ROP, which was shorter at Pennsylvania Hospital (4.1 days for the Pennsylvania Hospital group, 10.3 days for the CRYO-ROP group). However, on the basis of the mean number of days from diagnosis of prethreshold to threshold ROP (12.5 days for Pennsylvania Hospital, 10.5 days for CRYO-ROP) and the extent of extraretinal neovascularization at threshold (mean 7.9 sectors for Pennsylvania Hospital, 9.7 for CRYO-ROP), progression of retinopathy beyond the prethreshold stage had slowed and visual outcome in the eyes of infants at Pennsylvania Hospital treated with both cryotherapy and vitamin E (worse eye used for those treated with bilateral cryotherapy) was better than that reported for the treated eye of infants in the CRYO-ROP group (percentage of favorable visual acuity, 76% vs 48%, p = 0.04; percentage of normal structure posterior retinal pole, 71% vs 38%, p < or = 0.02).

CONCLUSIONS

In this small case series, the combination of cryotherapy with anti-oxidant prophylaxis and treatment appeared to decrease the severity and sequelae of threshold ROP. This hypothesis deserves testing in a large, randomized clinical trial.

Pharmacologic management of neonatal cerebral ischemia and hemorrhage: old and new directions

New developments in pharmacologic management of cerebral ischemia and hemorrhage are reviewed. A number of agents with diverse modes of action have now been shown to be neuroprotective in adult and neonatal animal models when administered either before or after a hypoxic-ischemic insult. As experience improves with these agents in hypoxic-ischemic injury and periventricular-intraventricular hemorrhage in human neonates, there is reason to be optimistic that effective neuroprotective strategies will soon be clinically available.

Current concepts in retinopathy of prematurity

Significant advances regarding understanding the etiology and treatment of retinopathy of prematurity have occurred in the 50 years since its discovery. Nevertheless, there is still a great deal to be learned. In spite of major technological advances in neonatal care, retinopathy of prematurity is a multi-factorial disease and probably cannot be completely prevented. Early intervention in the diagnosis and management of these infants has greatly improved their visual prognosis. Further studies may help pediatricians and neonatologists to understand and control associated risk factors. Ophthalmologists must continue to examine these patients early and follow them closely to control the associated treatable aspects of the disease, such as strabismus and amblyopia.

Retinopathy of prematurity

ROP is a common disorder among extremely low-birth-weight premature infant survivors and may cause total vision loss in as many as 2% to 4% of those weighing less than 2 lb (1 kg) at birth. Regular examinations begun in the intensive care unit permit early detection and treatment of progressive ROP, reducing visual impairment. Ongoing research into antioxidants, angiogenesis, light exposure, and newer surgical techniques may offer new approaches for preventing and treating established ROP. Infants who have had ROP that regressed should continue regular ophthalmologic follow-up to detect and treat myopia, strabismus, and if they have cicatricial sequelae, late retinal detachments as teens or adults. Infants who develop retinal detachments should be referred for early intervention and special education programs and remain in regular ophthalmologic follow-up for the detection and treatment of further ophthalmic complications.

Vitamin E therapy in retinopathy of prematurity

Vitamin E is a fat soluble antioxidant and as a result it is able to scavenge free radicals derived from oxygen. The premature infant and the retina are likely to be particularly vulnerable to the deleterious effects of these oxygen derived free radicals, and as a result prophylactic vitamin E has been suggested for the management of retinopathy of prematurity (ROP). However, despite numerous trials, prophylactic supplementation with vitamin E remains controversial. This paper will critically review the use of vitamin E in ROP and consider the risk/benefit relationship of such treatment in premature infants.

Is routine vitamin E administration justified in very low-birthweight infants?

Analysis of nine randomised controlled trials of prophylactic vitamin E supplementation in very low-birthweight infants (less than 1500g) showed no statistically significant reduction in the incidence of acute retinopathy of prematurity. There was a significant reduction (49 per cent) in the incidence of intraventricular haemorrhage, but no clear evidence for a corresponding reduction in intracerebral haemorrhage and no reduction in the incidence of haemorrhage confined to the germinal matrix. By combining the estimated reduction with the known incidence of long-term neurological disability associated with intracranial haemorrhage alone, it was shown that only 1.5 per cent (point estimate) and not more than about 4 per cent of all very low-birthweight infants are likely to benefit from routine vitamin E supplementation. In view of this, and data suggesting toxicity of vitamin E at concentrations close to those considered therapeutic, the routine use of vitamin E in very low-birthweight infants is not justified on present evidence. Only large randomised trials can establish whether currently used vitamin E preparations do more good than harm.

Effect of sustained pharmacologic vitamin E levels on incidence and severity of retinopathy of prematurity: a controlled clinical trial

The incidence and severity of retinopathy of prematurity (ROP) as affected by vitamin E prophylaxis at pharmacologic serum levels (5 mg/dl) were evaluated in a double-masked clinical trial of infants with a birth weight less than or equal to 2000 gm or a gestational age less than or equal to 36 weeks. The infants were enrolled by age 5 days and randomly assigned to receive parenterally administered, and later orally administered, free alpha-tocopherol (vitamin E) or its placebo. Study medication was continued until retinal vascularization was complete or active ROP had subsided, except in infants with a diagnosis of severe disease, in whom vitamin E was substituted for study medication. Acute ROP data were collected on 755 infants. Logistic regression analysis, with control for immaturity, oxygen exposure, and other illness risk factors, showed a decrease in incidence of ROP in vitamin E-treated infants (p = 0.003, all infants; p = 0.035, infants weighing less than or equal to 1500 gm at birth). Among the 424 infants weighing less than or equal to 1500 gm at birth, the age at enrollment influenced treatment effect (age day 0 to 1, p = 0.006 (n = 288) vs age day 2 to 5, p greater than 0.1 (n = 136]. Overall, 77.6% of infants with ROP had mild disease. Moderate to severe ROP was confined to infants weighing greater than or equal to 1500 gm at birth (25 given placebo, 25 given vitamin E), with progression to severe disease in nine placebo-treated versus three vitamin E-treated infants (p = 0.048). The incidence of severe ROP per se was not significantly decreased (all birth weights, p = 0.086; less than or equal to 1500 gm birth weight, p = 0.080); the sample size was too small, however, to assess this end point adequately. An increased incidence of sepsis and late-onset necrotizing enterocolitis was found among vitamin E-treated infants weighing less than or equal to 1500 gm at birth who received study medication for greater than or equal to 8 days (p = 0.006). Because most ROP is mild in degree and regresses completely, the risk/benefit ratio of pharmacologic prophylaxis for ROP is unfavorable. Treatment of moderate and severe ROP with vitamin E above physiologic serum levels (greater than 3 mg/dl) appears promising and should be further investigated. The interpretation of cicatricial outcome was confounded by the small number of patients involved and by subsequent treatment of severe ROP in placebo-treated infants with vitamin E.

Retinopathy of prematurity

Over the last decade major advances have been made in the understanding of the pathogenesis and evolution of retinopathy of prematurity (ROP). The increased survival of very small premature infants in modern neonatal intensive care units has led to the resurgence of this potentially blinding disease. ROP appears to be a multifactorial disease, the prevention of which is probably impossible even now, with the most accurate methods of blood gas monitoring and oxygen restriction. In addition to oxygen, there are a number of significant risk factors, such as birth weight and gestational age, ventilator hours, hyper and hypocarbia, hypoxia and acidosis, xanthine therapy and probably bright light. Current data suggest that the level of antioxidants in the immature retina is relatively low and therefore oxygen radicals which accumulate in the preterm baby's retina may play an important role in the pathogenesis of ROP. The treatment of the disease in both its "active" and "cicatricial" stages emphasizes the need for a new classification which could serve as a common international language through which results may be compared. Vitamin E was suggested in some studies to be helpful in preventing the severe stages of the disease, but its efficacy has yet to be proved. Treatment modalities such as photocoagulation, cryotherapy and vitrectomy are being tried as a means of therapy in the more advanced stages of the disease. Preliminary results of a large multicenter study support the efficacy of cryotherapy.

Retinopathy of prematurity

ROP is a challenging disease of the decade of the 1980s. Answers, even partial answers, to many of its questions may provide information bearing on those same questions in other blinding vascular retinopathies, such as diabetes and sickle cell disease. Answers more clearly defining the role of oxygen, ventilation, antioxidants, blood transfusions, and a host of diseases of the premature infant will lead to better care of that infant. I have tried in this article to present the boundaries of the problem, a theory of its genesis and progression, and a review of the major issues to be confronted by the pediatric, ophthalmologic, and basic science communities through its recurrence today. I have tried to make it clear to the reader when I was so doing. I have used information liberally from studies both under way and in the planning stages to make the reader aware of what is being done, even if these have not yet reached fruition, for the field is a rapidly growing one. Finally, I have tried to point out directions that I believe clinical and experimental work should take on certain critical issues.

Vitrectomy for advanced stages of retinopathy of prematurity

We did a retrospective review of the consecutive vitrectomies for traction retinal detachment associated with retinopathy of prematurity performed at our institution. Fifty-eight eyes were operated on in 46 patients at less than 1 year of age, including 12 eyes with partial retinal detachments and 46 eyes with total retinal detachments. Only patients with at least six months follow-up were considered for success. Twenty-five eyes (43%) were anatomically reattached. Factors associated with good anatomic outcome included greater mean preoperative pupillary dilation, absence of posterior synechiae, deep anterior chamber, partial detachment or open-funnel total detachment configuration, and adequate posterior membrane removal. Of the 25 eyes with attached retinas, 11 had fixing and following visual acuities or better. Three eyes with attached retinas had no light perception and 11 eyes with attached retinas had light perception only. To maximize anatomic and functional results we emphasize the need to operate early, when the retinal funnel is still open.

An interpretation of retinopathy of prematurity in terms of spindle cells: relationship to vitamin E prophylaxis and cryotherapy

Spindle cells in the hyperoxygenated, avascular, vanguard retina are proposed to be the peripheral inducers of the neovascularization associated with retinopathy of prematurity (ROP). The induction of ROP is conceptualized in terms of three basic events. First, activation of spindle cells results initially in the increase in gap junctions between adjacent spindle cells, secondarily in the increase in cytoplasmic volume of rough endoplasmic reticulum, and ultimately in the synthesis and secretion of angiogenic factors Second, maturation of spindle cells is associated with a decrease in gap junctions, a diminished cytoplasmic volume of rough endoplasmic reticulum, and a cessation of synthesis and secretion of angiogenic factors. Third, myofibroblasts invade the vitreous concomitantly with spindle cell maturation and provide the tractional force that can produce retinal separation. The extent of interstitial retinol binding protein within the subretinal space explains the gestational-age-dependent efficacy of vitamin E in suppressing the development of severe ROP. The kinetics of both spindle cell activation/maturation and myofibroblast invasion predict the efficacy of appropriately timed and placed transretinal cryotherapy.

Cryotherapy for retinopathy of prematurity: timing of intervention

This is a retrospective study of the results of cryotherapy for retinopathy of prematurity in 30 eyes of 17 patients from November 1976 to March 1983. The report is in the language of the international classification of retinopathy of prematurity. Ten eyes were treated at stage 4 disease, seven eyes at severe or late stage 3 'plus' disease, and 13 eyes at moderate or mid-stage 3 'plus' disease. All eyes had the cryotherapy applied to the ridge and the extraretinal fibrovascular proliferation contiguous with the ridge, some with additional treatment of the avascular retina. The results show that this method of treatment must be applied before severe stage 3 'plus' disease is established in order to prevent visual disability and minimise retrolental fibroplasia. The treatment of the selected cases of progressive moderate stage 3 'plus' disease accomplished those objectives.

Controversies in neonatal nutrition

The assessment of growth parameters remains one of the most practical and valuable tools to estimate nutritional status in neonates. Growth assessment in full-term infants is performed by using charts developed by the National Center for Health and Statistics. The assessment of post-natal growth in premature infants is controversial and can be performed by using either intrauterine or extrauterine standards. The selection of appropriate growth charts should be based on clinical, demographic, ethnic, and socioeconomic similarities of the population used for reference. Daily energy intakes ranging from 100 to 120 kcal/kg/day have been recommended for full-term infants, while higher intakes ranging from 114 to 181 kcal/kg/day have been recommended for premature neonates. Full-term infants should be nursed or nipple fed on demand; however, premature infants should ideally be tube fed by intermittent gastric feeding (gavage). Continuous gastric and transpyloric feedings are indicated in selected infants. Human milk is a preferred food for full-term infants during the first six months of life; however, this precept does not suggest that all infants who are exclusively breast-fed will grow adequately. Preterm human milk is also a preferred food for the low birthweight infant, provided nutritional supplements are used. It is unclear whether the supplementation of vitamin D, iron, and fluoride in full-term breast-fed infants should be started at birth, at the time of initiation of solid foods, or at the age of six months. The routine supplementation of multivitamins, folic acid, and vitamin E to all low birthweight infants is controversial. Most investigators suggest vitamin supplementation be given until the intake of formula or breast milk is sufficient to meet daily requirements. Vitamin E appears to exert a protective effect in premature infants against the development of severe retinopathy. The supplementation of vitamin E should be dependent upon the serum vitamin E concentration. It is controversial whether iron supplementation for premature infants should be initiated soon after birth or at two months of age, or whether higher doses of iron should be given to very low birthweight infants. If iron supplementation is started at birth, vitamin E status should be closely monitored. Although the optimal intakes of calcium and phosphorus in infant feedings have not been firmly established, the levels of calcium and phosphorus in human milk appear to be inadequate for the growing low birthweight infant.(ABSTRACT TRUNCATED AT 400 WORDS)

Disposition of intravenously administered pharmacologic doses of vitamin E in newborn rabbits

Newborn rabbits were given a single intravenous dose (100 mg/kg) of either alpha-tocopherol or alpha-tocopheryl acetate to compare disposition characteristics of these two forms of vitamin E. The resulting tissue concentrations of alpha-tocopherol and alpha-tocopheryl acetate differed significantly. Tissue concentrations of either form of vitamin E were much higher than those provided by normal nutrition, and remained unchanged (except in the liver) for 6 days after dose. alpha-Tocopheryl acetate was not completely converted to alpha-tocopherol, and only 50% of the dose was recovered 3 days after administration. The entire dose of alpha-tocopherol was recovered intact 3 days after administration. The persistence of very high tissue vitamin E concentrations after a single intravenous dosing, the disappearance from the body of half of the administered dose of alpha-tocopheryl acetate, and the lack of complete conversion of alpha-tocopheryl acetate to alpha-tocopherol when given intravenously have profound implications regarding the current clinical practice of giving repeated pharmacologic doses of vitamin E to newborn infants.

Vitamin E and retinopathy of prematurity. Follow-up at one year

Five hundred forty-five infants weighing less than 1501 g at birth were entered into a randomized, prospective study to determine the effect of high serum levels (5 mg/dL) of vitamin E used prophylactically to try to prevent or alter the natural course of retinopathy of prematurity (ROP) and its sequel, retrolental fibroplasia (RLF). Three hundred twenty-eight infants were available for the one- to two-year eye examination. Although there was a trend (P = 0.072) toward less severe RLF among vitamin E-treated infants, the incidence of RLF was 11/162 (6.8%) in the placebo treated (P) infants, and 12/166 (7.2%) in the vitamin E-treated (E) infants. The incidences of hyperopia, myopia, anisometropia, strabismus and amblyopia were also similar in both the P and E groups.

Observations on the retinopathy of prematurity

The fourfold to fivefold increased survival rate since 1950 of premature infants with birthweights of less than 1,000 g apparently explains the increase in cases of retinopathy of prematurity in recent years. A new international classification permits standardized grading of the retinopathy of prematurity based on severity, anterior-posterior location, and the meridians involved. Previously reported clinical trials on the role of vitamin E in the prevention of retinopathy of prematurity have given conflicting results.

The treatment of advanced retinopathy of prematurity by cryotherapy and scleral buckling surgery

Seventeen eyes of nine extremely premature infants with severe acute proliferative retinopathy of prematurity (ROP, Grades III-V) were treated. Cryotherapy alone was used in ten eyes to ablate extensive areas of avascular retina to thereby induce involution of widespread intravitreous neovascularization. No attempt was made to directly treat the arteriovenous shunt or neovascularization itself. Scleral buckling surgery was used in combination with cryotherapy in seven additional eyes to relieve diffuse vitreous traction to intravitreous neovascularization which had caused extensive traction retinal detachment. Cryotherapy was uniformly successful in causing involution of widespread intravitreous neovascularization in all patients treated. Scleral buckling surgery was initially effective in reattaching the retina in all cases but late manifestations of severe ongoing vitreoretinal traction required additional open-sky vitrectomy in two eyes and resulted in inoperable recurrent total traction retinal detachment in one eye and extensive macular scarring in another. A comparison is made between the proliferative retinopathies seen in ROP and diabetes mellitus and a rationale for effective cryotherapy in ROP is presented. In our clinical experience, the single most important prognostic factor determining the potential severity of ROP is the width and extent of the retinal avascular zone. The wider the zone, the greater the probability of rapid progression from early to advanced grades of disease.

Suppression of severe retinopathy of prematurity with vitamin E supplementation. Ultrastructural mechanism of clinical efficacy

Three clinical trials enrolling 418 infants (less than or equal to 1500 g birth weight) and an ultrastructural data base of 71 pairs of whole eye donations have elucidated the efficacy of vitamin E in suppressing the development of severe retrolental fibroplasia (ROP). Only continuous vitamin E supplementation to adult physiologic levels from the first hours of life suppresses the development of severe ROP. Supplementation does not increase the incidence of necrotizing enterocolitis, sepsis, intraventricular hemorrhage, or mortality. Only multivariate analysis, which considers all risk factors simultaneously, is appropriate when appraising the efficacy of supplementation since all the clinical risk factors uniquely impinge on the oxygen dynamics of the developing retina. Mesenchymal spindle cells are the cellular mediators of the induction of ROP by oxygen in which increased oxygen tension triggers extensive gap junction formation between adjacent spindle cells. This cellular event, which occurs as early as four days of life, halts the normal vasoformative process and triggers neovascularization, which becomes clinically evident some 8 to 12 weeks later.

Current concepts of the effect of oxygen on the developing retina

The role of oxygen in the development of retrolental fibroplasia and the mechanism of oxygen changes in the developing retina are discussed. The primary effect of oxygen is one of Vascular closure and the secondary response, which occurs after removal from increased oxygen, is retinal neovascularization. A brief discussion of recent observations on the potential role of vitamin E in the prevention of retrolental fibroplasia is presented.

Current therapy of retrolental fibroplasia. Retinopathy of prematurity

Retrolental fibroplasia, frequently referred to now as the "retinopathy of prematurity," has shown an increased incidence in recent years. This is apparently due to advances in neonatal care, which have resulted in a four- to five-fold improvement in the survival of the extremely low birthweight infants and it is these infants who are at the highest risk of developing retrolental fibroplasia. The use of large supplements of vitamin E, a known antioxidant, is discussed along with other forms of therapy.