Gloria B. Valencia

Caffeine impact on neonatal morbidities

Caffeine is a silver bullet in neonatology. This ubiquitous trimethylxanthine, pervasively used in the human diet and beverages, significantly impacts on major acute neonatal morbidities including apnea of prematurity, bronchopulmonary dysplasia, patent ductus arteriousus with or without surgical ligation and post-operative apnea. Potential uses in respiratory distress syndrome as suggested by improved lung function in primate models is supported by the decreased time on mechanical ventilation and need for oxygen therapy. Improved later outcomes at 18 to 22 months include clinically significant decreases in cerebral palsy, cognitive impairment, and severe retinopathy of prematurity in those babies who received caffeine during the neonatal period compared to non-caffeine treated placebo neonates. Ongoing and future research studies focus on optimizing current dose regimens to determine whether benefits can be maximized while maintaining an impressive safety profile. Molecular pharmacologic studies focused on the molecular and the biochemical mechanisms underlying the protective effects of caffeine are also being done to optimize treatment regimes and to target potential molecular pathways leading to further decreases in acute and long term neonatal morbidities. Since its use in newborns three decades ago, caffeine is now one of the safest, most cost-beneficial and effective therapies in the newborn.

Effects of probiotics, prebiotics, and synbiotics on messenger RNA expression of caveolin-1, NOS, and genes regulating oxidative stress in the terminal ileum of formula-fed neonatal rats.

Necrotizing enterocolitis (NEC) afflicts extremely low birth weight neonates, and probiotics reduces its incidence and severity. NO is involved in the pathogenesis of NEC, and caveolin-1 regulates NO signaling. We tested the hypothesis that intestinal caveolin-1 and NOS are deficient in formula-fed neonatal rats and that supplementation with “Florastar Kids” and/or galacto-oligosaccharides and fructo-oligosaccharides preserves caveolin-1 and NOS. At birth (P0), neonatal rat pups were maternally fed or hand-gavaged with or without supplemented formula. Samples from the terminal ileum were analyzed for total NO metabolites, growth factors, and gene expression of caveolin-1, NOS isoforms, and antioxidants. Our data showed that formula feeding with and without supplementation resulted in significant growth restriction. Despite suboptimal nutrition, growth factors involved in intestinal repair and regeneration were increased in the neonatal rat ileum. Caveolin-1, endothelial NOS, and neuronal NOS were simultaneously down-regulated with formula feeding while inducible NOS was up-regulated. Superoxide dismutase and glutathione peroxidase were up-regulated with supplementation. These data provide a probable mechanism for the benefits of supplemented formula for decreasing the severity of NEC by preserving the antioxidant systems.

Population pharmacokinetics of meropenem in plasma and cerebrospinal fluid of infants with suspected or complicated intra-abdominal infections

Background: Suspected or complicated intra-abdominal infections are common in young infants and lead to significant morbidity and mortality. Meropenem is a broad-spectrum antimicrobial agent with excellent activity against pathogens associated with intra-abdominal infections in this population. The purpose of this study was to determine the pharmacokinetics (PK) of meropenem in young infants as a basis for optimizing dosing and minimizing adverse events. Methods: Premature and term infants <91 days old hospitalized in 24 neonatal intensive care units were studied. Limited PK sampling was performed following single and multiple doses of meropenem 20 to 30 mg/kg of body weight every 8 to 12 hours based on postnatal and gestational age at birth. Population and individual patient (Bayesian) PK parameters were estimated using NONMEM. Results: In this study, 200 infants were enrolled and received the study drug. Of them, 188 infants with 780 plasma meropenem concentrations were analyzed. Their median (range) gestational age at birth and postnatal age at PK evaluation were 28 (23–40) weeks and 21 (1–92) days, respectively. In the final PK model, meropenem clearance was strongly associated with serum creatinine and postmenstrual age (clearance [L/h/kg] = 0.12*[(0.5/serum creatinine)**0.27]*[(postmenstrual age/32.7)**1.46]). Meropenem concentrations remained >4 &mgr;g/mL for 50% of the dose interval and >2 &mgr;g/mL for 75% of the dose interval in 96% and 92% of patients, respectively. The estimated penetration of meropenem into the cerebrospinal fluid was 70% (5–148). Conclusions: Meropenem dosing strategies based on postnatal and gestational age achieved therapeutic drug exposure in almost all infants.

Mycoplasma hominis and Ureaplasma urealyticum in neonates with suspected infection

The role of genital mycoplasmas in the pathogenesis of neonatal infection is incompletely understood. We performed nasopharyngeal, blood and cerebrospinal fluid (CSF) cultures for Mycoplasma hominis and Ureaplasma urealyticum in 69 neonates who underwent a diagnostic workup for suspected sepsis. The mean gestational age was 35.9 weeks (range, 25 to 42 weeks) with a mean birth weight of 2386 g (range, 652 to 4420 g). Twenty-seven infants (39.1%) had positive nasopharyngeal cultures; 6 were positive for M. hominis, 10 for U. urealyticum and 11 for both organisms. Seven (26%) of these 27 patients developed chronic lung disease compared with 2 (4.7%) infants in the non-colonized group. Nine infants had positive CSF cultures for M. hominis and one infant had a positive CSF culture for U. urealyticum. All blood cultures were sterile. One of the infants with a positive CSF culture for M. hominis had clinical evidence of systemic infection. All of the infants were treated with antibiotic agents that were not active against mycoplasmas. These data indicate that genital mycoplasmas can be found commonly in the CSF and nasopharynx of infants with suspected sepsis. Their etiologic role in the causation of infection and chronic lung disease, however, remains unclear.

Safety and effectiveness of meropenem in infants with suspected or complicated intra-abdominal infections.

BACKGROUND Intra-abdominal infections are common in young infants and lead to significant morbidity and mortality. Meropenem is a broad-spectrum antimicrobial with excellent activity against pathogens associated with intra-abdominal infections. The purpose of this study was to determine the safety and effectiveness of meropenem in young infants with suspected or complicated intra-abdominal infections. METHODS Preterm and term infants <91 days of age with suspected or confirmed intra-abdominal infections hospitalized in 24 neonatal intensive care units were studied in an open-label, multiple-dose study. Adverse events and serious adverse events were collected through 3 and 30 days following the last meropenem dose, respectively. Effectiveness was assessed by 3 criteria: death, bacterial cultures, and presumptive clinical cure score. RESULTS Of 200 subjects enrolled in the study, 99 (50%) experienced an adverse event, and 34 (17%) had serious adverse events; no adverse events were probably or definitely related to meropenem. The most commonly reported adverse events were sepsis (6%), seizures (5%), elevated conjugated bilirubin (5%), and hypokalemia (5%). Only 2 of the serious adverse events were determined to be possibly related to meropenem (isolated ileal perforation and an episode of fungal sepsis). Effectiveness was evaluable in 192 (96%) subjects, and overall treatment success was 84%. CONCLUSIONS Meropenem was well tolerated in this cohort of critically ill infants, and the majority of infants treated with meropenem met the definition of therapeutic success. CLINICAL TRIALS REGISTRATION NCT00621192.

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.

Hydrogen Peroxide Accumulation in the Choroid During Intermittent Hypoxia Increases Risk of Severe Oxygen-Induced Retinopathy in Neonatal Rats

PURPOSE Extremely low gestational age neonates (ELGANs) requiring oxygen therapy often experience frequent episodes of intermittent hypoxia (IH) and are at high risk for severe retinopathy of prematurity (ROP). Using an established model for oxygen-induced retinopathy (OIR), we examined the hypothesis that there is a critical number of daily brief IH episodes which will result in irreversible retinal oxidative damage. METHODS Newborn rats were exposed to increasing daily clustered IH episodes (12% O₂ with 50% O₂) from postnatal day (P) 0 to P7 or P0 to P14, or placed in room air (RA) until P21 following 7- or 14-day IH. RA littermates at P7, P14, and P21 served as controls. A group exposed to constant 50% O₂ (CH) served as a second control. Blood gases, eye opening at P14, retinal, and choroidal oxidative stress and lipid peroxidation (8-isoPGF(2α)), oxidants (H₂O₂) and antioxidants (catalase and SOD), retinal pathology (adenosine diphosphatase (ADPase)-stained retinal flatmounts), and mitochondria-related genes were assessed. RESULTS pO₂ levels were higher with increasing IH episodes and remained elevated during the reoxygenation period. High SO₂ levels were associated with most severe OIR. Levels of all measured biomarkers peaked with six IH episodes and decreased with 8 to 12 episodes. H₂O₂ accumulated in the choroid during the reoxygenation period with irreversible retinal damage. CONCLUSIONS Our data suggest that six is the maximum number of IH episodes that the retina can sustain. Accumulation of H₂O₂ in the choroid may result in high levels being delivered to the entire retina, ultimately resulting in irreversible retinal oxidative damage.

Comparative effects of probiotics, prebiotics, and synbiotics on growth factors in the large bowel in a rat model of formula-induced bowel inflammation.

Objectives: Supplementation with probiotics has been shown to prevent gastrointestinal damage possibly through preservation of growth factors. We tested the hypothesis that probiotics, prebiotics, or synbiotics supplementation preserves intestinal insulin-like growth factors (IGFs) and epidermal growth factors (EGFs) in formula-fed neonatal rats. Materials and Methods: At birth (postnatal day 0 [P0]), neonatal rat pups (n = 18 pups/group) were either maternally fed or hand-gavaged with formula supplemented with probiotics (Pro-Fed), prebiotics, or synbiotics from P0 to P3. A formula-fed control group received formula without supplementation. At P4, large bowel samples were assessed histologically and assayed for vascular endothelial growth factor (VEGF), soluble VEGF receptor-1, IGF-I, IGF-II, and EGF. Results: All formula-fed groups were severely growth suppressed with comparable mortalities. Moderate preservation of bowel integrity was noted in the Pro-Fed group. In contrast, severe inflammation was seen in all of the other formula groups. This was associated with significant increases in VEGF levels in all of the formula groups (P < 0.05) except the Pre-Fed group. Similar elevations in soluble VEGF receptor-1 (P < 0.05), IGF-I (P < 0.05), and EGF (P < 0.05) were noted, but statistical significance was achieved only in the Pro-Fed group. Conclusions: Induction of IGF-I and EGF with moderate bowel integrity may represent a protective effect of probiotics against formula-induced inflammation. These data, taken collectively, suggest that probiotics may provide more beneficial effects on the developing large bowel than prebiotics and synbiotics.

Pharmacologic synergism of ocular ketorolac and systemic caffeine citrate in rat oxygen-induced retinopathy

Background:Caffeine or ketorolac decrease the risk of retinopathy of prematurity and may act synergistically to improve beneficial effect. Combination of caffeine (Caff) and ketorolac (Keto) to prevent oxygen-induced retinopathy was studied.Methods:Newborn rats exposed to room air (RA) or intermittent hypoxia (IH) consisting of 12% O2 during hyperoxia (50% O2) from birth (P0) had single daily IP injections of Caff from P0-P13 or saline; and/or ocular Keto (Acuvail, 0.45% ophthalmic solution) administered subcutaneously over the eyes from P5-P7. Pups were studied at P14 or placed in RA for recovery from IH (IHR) until P21. Eyes were examined for neovascularization, histopathology, growth factors, and VEGF-signaling genes.Results:Severe retinal damage noted during IHR in the untreated groups evidenced by hemorrhage, neovascularization, and oxygen-induced retinopathy (OIR) pathologies were prevented with Keto/Caff treatment. Keto and/or Caff treatment in IH also promoted retinal neural development evidenced by eye opening (92%, P < 0.001 vs. 31% in the placebo-treated IH group). No corneal pathologies were noted with Keto.Conclusion.Caff or Keto given individually reduced retinal neovascularization, but the two drugs given together prevented severe OIR.

Exogenous Superoxide Dismutase Mimetic Without Scavenging H2O2 Causes Photoreceptor Damage in a Rat Model for Oxygen-Induced Retinopathy

PURPOSE Frequent, brief intermittent episodes of hypoxia (IH) during hyperoxia increase reactive oxygen species in the immature retina with compromised antioxidant systems, thus leading to oxygen-induced retinopathy (OIR). We examined the hypothesis that early exposure to a mimetic of superoxide dismutase (SOD), the first line of defense against oxidative stress, will decrease IH-induced reactive oxygen species (ROS) and prevent severe OIR in our rat model. METHODS To test this hypothesis, newborn rats (P0) were exposed to IH consisting of alternating cycles of 50% O₂ with brief hypoxia (12% O₂) until P14 during which they were treated with a single daily intraperitoneal (IP) dose of MnTBAP (a SOD mimetic) at 1.0, 5.0, or 10.0 mg/kg on P0, P1, and P2. A saline-treated group served as vehicle controls. Groups were analyzed following IH at P14 or allowed to recover in room air (RA) until P21. Control littermates were raised in RA with all conditions identical except for inspired O₂. Ocular assessment of OIR severity, oxidative stress, angiogenesis, antioxidant activity, and oxidative phosphorylation (OXPHOS) were conducted at P14 and P21. RESULTS Collectively, the data show increased oxidative stress and angiogenesis with MnTBAP, which was associated with photoreceptor damage, retinal characteristics consistent with severe OIR, and changes in genes regulating OXPHOS. CONCLUSIONS In the setting of IH, the use of exogenous SOD mimetics must be combined with H₂O₂ scavengers in order to prevent photoreceptor damage and severe OIR.