| 1. |
- Hellström, Ann, 1959, et al.
(author)
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Retrospective evaluation of ophthalmological and neurological outcomes for infants born before 24 weeks gestational age in a Swedish cohort
- 2022
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In: Bmj Open. - : BMJ. - 2044-6055. ; 12:8
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Journal article (peer-reviewed)abstract
- Objectives To retrospectively evaluate ophthalmological and neurological outcomes in a Swedish cohort of infants born before 24 weeks gestational age (GA) and explore risk factors for visual impairment. Setting Eye and paediatric clinics in Sweden. Participants Infants screened for retinopathy of prematurity (ROP) (n=399), born before 24 weeks GA, 2007-2018. Cases were excluded if ophthalmological follow-up records could not be traced. Primary and secondary outcome measures Primary outcomes were ophthalmological, including visual acuity (VA), refractive error, strabismus, nystagmus and cerebral visual impairment (CVI). Secondary outcomes comprised neonatal and neurological morbidities. Data were retrospectively retrieved from medical records. Results The 355 assessed children had a median GA of 23 weeks and 2 days and a median birth weight of 565 g. At the last available ophthalmological examination, the median age was 4.8 years (range 0.5-13.2 years). Nystagmus was recorded in 21.1%, strabismus in 34.8%, and 51.0% wore spectacles. Seventy-three of 333 (21.9%) were visually impaired, defined as being referred to a low vision clinic and/or having a VA less than 20/60 at 3.5 years of age or older. ROP treatment was a significant risk factor for visual impairment (OR 2.244, p=0.003). Visually impaired children, compared with children without visual impairment, more often had neurological deficits such as intellectual disability 63.8% versus 33.3% (p<0.001), epilepsy 21.1% versus 7.5% (p=0.001) and autism spectrum disorders 32.8% versus 20.9% (p=0.043). Nine of the 355 children had been diagnosed with CVI. Conclusions Children born before 24 weeks GA frequently had visual impairment in association with neurological deficits. CVI was rarely diagnosed. A multidisciplinary approach for the evaluation and habilitation of these vulnerable infants is warranted. National follow-up guidelines need to be developed and implemented.
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| 2. |
- Lundgren, Pia, 1967, et al.
(author)
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National cohort of infants born before 24 gestational weeks showed increased survival rates but no improvement in neonatal morbidity
- 2022
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In: Acta Paediatrica. - : Wiley. - 0803-5253 .- 1651-2227. ; 111:8, s. 1515-1525
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Journal article (peer-reviewed)abstract
- Aim To describe survival and neonatal morbidities in infants born before 24 weeks of gestation during a 12-year period. Methods Data were retrieved from national registries and validated in medical files of infants born before 24 weeks of gestation 2007-2018 in Sweden. Temporal changes were evaluated. Results In 2007-2018, 282 live births were recorded at 22 weeks and 460 at 23 weeks of gestation. Survival to discharge from hospital of infants born alive at 22 and 23 weeks increased from 20% to 38% (p = 0.006) and from 45% to 67% (p < 0.001) respectively. Caesarean section increased from 12% to 22% (p = 0.038) for infants born at 22 weeks. Neonatal morbidity rates in infants alive at 40 weeks of postmenstrual age (n = 399) were unchanged except for an increase in necrotising enterocolitis from 0 to 33% (p = 0.017) in infants born at 22 weeks of gestation. Bronchopulmonary dysplasia was more common in boys than girls, 90% versus 82% (p = 0.044). The number of infants surviving to 40 weeks doubled over time. Conclusion Increased survival of infants born before 24 weeks of gestation resulted in increasing numbers of very immature infants with severe neonatal morbidities likely to have a negative impact on long-term outcome.
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| 3. |
- Hellgren, Gunnel, 1961, et al.
(author)
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Decreased Platelet Counts and Serum Levels of VEGF-A, PDGF-BB, and BDNF in Extremely Preterm Infants Developing Severe ROP
- 2021
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In: Neonatology. - : S. Karger AG. - 1661-7800 .- 1661-7819. ; 118, s. 18-27
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Journal article (peer-reviewed)abstract
- Introduction: Thrombocytopenia has been identified as an independent risk factor for retinopathy of prematurity (ROP), although underlying mechanisms are unknown. In this study, the association of platelet count and serum platelet-derived factors with ROP was investigated. Methods: Data for 78 infants born at gestational age (GA) <28 weeks were included. Infants were classified as having no/mild ROP or severe ROP. Serum levels of vascular endothelial growth factor A, platelet-derived growth factor BB, and brain-derived neurotrophic factor were measured in serum samples collected from birth until postmenstrual age (PMA) 40 weeks. Platelet counts were obtained from samples taken for clinical indication. Results: Postnatal platelet counts and serum concentrations of the 3 growth factors followed the same postnatal pattern, with lower levels in infants developing severe ROP at PMA 32 and 36 weeks (p < 0.05-0.001). With adjustment for GA, low platelet counts and low serum concentrations of all 3 factors at PMA 32 weeks were significantly associated with severe ROP. Serum concentrations of all 3 factors also strongly correlated with platelet count (p < 0.001). Conclusion: In this article, we show that ROP, platelet counts, and specific pro-angiogenic factors correlate. These data suggest that platelet-released factors might be involved in the regulation of retinal and systemic angiogenesis after extremely preterm birth. Further investigations are needed.
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| 4. |
- Hellström, Pia, 1960-, et al.
(author)
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A comparative study of enzymatic and Fenton pretreatment applied to a birch kraft pulp used for MFC production in a pilot scale high-pressure homogenizer
- 2016
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In: TAPPI Journal. - : TAPPI Press. - 0734-1415. ; 15:6, s. 375-381
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Journal article (peer-reviewed)abstract
- Microfibrillated cellulose (MFC) was produced in pilot scale from a bleached birch (Betula verrucosa) kraft pulp that was pretreated with either Fenton's reagent or with a combined mechanical and enzymatic method used at the Centre Technique du Papier (CTP; Grenoble, France). The change in fiber fibrillation during the homogenization treatment was monitored by analyzing the fiber and the fines content, size fractionation, rheological properties and visualization by light-and scanning electron microscopy (SEM). The Fenton pretreatment resulted in MFC suspensions that contained a high amount of small sized elements. After five passes through the high-pressure homogenizer, the amount of particles smaller than 20 mu m was 37% for the Fenton pretreated MFC compared to 13% for the enzymatically (endoglucanase) pretreated MFC. Altogether, the Fenton pretreatment enabled preparation of MFC with a higher degree of fibrillation after the same number of passes through the high-pressure homogenizer. Another option is to produce MFC of the same amount of fibrillation as after an enzymatic stage, but at significantly lower energy consumption.
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| 5. |
- Hellström, Pia, 1960-, et al.
(author)
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Fenton pre-treated microfibrillated cellulose evaluated as a strength enhancer in the middle ply of paperboard
- 2014
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In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 29:4, s. 732-740
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Journal article (peer-reviewed)abstract
- Microfibrillated celluloses (MFCs), produced by various pre-treatments of a fully bleached birch kraft pulp, were evaluated as strength enhancers in test sheets representing the middle ply of paperboard. The furnish consisted of hydrogen peroxide bleached high temperature spruce chemithermomechanical pulp (HT-CTMP), MFC and a retention system containing cationic starch and an anionic silica sol. The MFC was prepared via a mechanical treatment in a colloid mill after pretreatment with Fenton's reagent, monocomponent endoglucanase or acidic hydrogen peroxide. Addition of 5% MFC, produced with Fenton pre-treatment, resulted in improved HT-CTMP properties with respect to increased tensile index (similar to 35%), z-directional strength (similar to 50%), tensile stiffness index (similar to 25%) compared to HT-CTMP test sheets prepared without MFC addition. The strength improvement was linearly correlated to the density of the tests sheet, to the surface area (BET) and to the surface charge of the enzymatic or chemically pre-treated MFCs.
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| 6. |
- Hellström, Pia, 1960-
(author)
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Fenton Pre-treatment of a Birch Kraft Pulp for MFC preparation
- 2015
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Licentiate thesis (other academic/artistic)abstract
- The potential to use acidic hydrogen peroxide in the presence of ferrous ions (Fenton’s reagent) as a pre-treatment when producing microfibrillar cellulose (MFC) from a fully bleached birch (Betula verucosa) kraft pulp was investigated and the properties of the produced MFC was compared to the properties of a MFC produced with enzymatic pre-treatment with a monocomponent endoglucanase (FiberCare® R). The mechanical treatment to MFC was performed in a laboratory colloid mill or in a pilot high-pressure homogeniser and the pre-treated pulps as well as the produced MFCs were chemically and morphologically characterised. Additionally, the MFCs produced in the colloid mill were evaluated as strength enhancers in test sheets representing the middle ply of paperboard.From the chemical characterisation, it was concluded that the Fenton pre-treatment caused a decrease in the degree of polymerisation (DP) and an increase in both carboxyl- and carbonyl groups. The increase in carbonyl groups could not be explained by the formation of new reducing end groups due to depolymerisation which indicates that carbonyl groups are introduced along the cellulose chain. The enzymatic pre-treatment as performed in this study caused less impact on the cellulosic material, i.e. resulted in a pulp with a higher DP and a much lower amount of carbonyl- and carboxylic groups compared with the Fenton pre-treated pulps. In the subsequent mechanical treatment in a colloid mill, the Fenton pre-treated pulps were easier to process mechanically i.e. reached a higher specific surface area and a higher surface charge at a given mechanical treatment time compared to enzymatic pre-treated pulps and pulps not subjected to any pre-treatment. These findings were confirmed when MFCs were produced by homogenisation at high pressure in multiple passes; the birch kraft pulp was either pre-treated with Fenton’s reagent or the combined mechanic and enzymatic pre-treatment methodology used at the Centre Technique du Papier (CTP, France). By size fractionation, rheological measurements and scanning electron microscopy, it was revealed that Fenton pre-treatment resulted in MFC suspension containing a significantly higher proportion of small sized material (< 0.2 mm).When the MFCs were evaluated as strength enhancers in test sheets produced from a furnish consisting of a spruce (Picea abies) chemithermomechanical pulp, MFC and a retention system containing cationic starch and an anionic silica sol, Fenton pre-treated MFCs increased the strength properties more than the enzymatic pre-treated MFCs. Addition of 5 wt% Fenton pre-treated MFC resulted in an increase in z-directional strength of about 50%, an increase in tensile stiffness index of about 25% and an increase in tensile index of 35% compared to test sheets prepared without MFC addition.
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| 7. |
- Hellström, Pia, 1960-, et al.
(author)
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The effect of Fenton chemistry on the properties of microfibrillated cellulose
- 2014
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In: Cellulose. - : Springer. - 0969-0239 .- 1572-882X. ; 21:3, s. 1489-1503
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Journal article (peer-reviewed)abstract
- A fully bleached birch kraft pulp was treated with acidic hydrogen peroxide in the presence of ferrous ions (Fenton's reagent) and thereafter treated mechanically in a colloid mill to produce a product containing microfibrillated cellulose (MFC). The produced MFC products were chemically and morphologically characterized and compared with MFC products produced without pretreatment as well as with enzymatic hydrolysis. Fenton treatment resulted in an increase in total charge and number of carbonyl groups while the intrinsic viscosity decreased. The Fenton treated pulps were easier to process mechanically i.e. they reached a higher specific surface area at a given mechanical treatment time and the MFC produced had a stable water-fibre suspension for at least 8 weeks compared to enzymatic pretreated pulps and pulps not subjected to any pretreatment.
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| 8. |
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| 9. |
- Lundgren, Pia, 1967-, et al.
(author)
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Erythropoietin serum levels, versus anaemia as risk factors for severe retinopathy of prematurity
- 2019
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In: Pediatric Research. - : Nature Publishing Group. - 0031-3998 .- 1530-0447. ; 86:2, s. 276-282
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Journal article (peer-reviewed)abstract
- Background: Preterm infants with anaemia are treated with recombinant human erythropoietin (rhEPO). It is debated whether rhEPO treatment is a risk factor for retinopathy of prematurity (ROP). We evaluated longitudinal EPO and haemoglobin levels, blood transfusions and neonatal morbidities as risk factors for severe ROP.Method: This prospective study included 78 Swedish infants, born <28 weeks gestational age (GA), screened for ROP. We tested serum EPO levels on postnatal days 1, 7, 14 and 28 and at postmenstrual ages 32, 36 and 40 weeks. Haemoglobin levels and blood transfusions were recorded during postnatal weeks 1-4. Anaemia was defined as haemoglobin ≤110 g/L.Results: During postnatal week 1, infants with severe ROP requiring treatment (28%) more frequently developed anaemia (42.9% versus 8.0%, P = 0.003) and had higher mean EPO levels (postnatal day 7: 14.2 versus 10.8 mIU/mL, P = 0.003) compared to infants with no or less severe ROP not requiring treatment. In multivariable analyses, GA and anaemia during week 1 remained significant risk factors, but elevated EPO level postnatal day 7 was no longer significant.Conclusions: Among infants born <28 weeks GA, anaemia during week 1 was a significant risk factor for severe ROP requiring treatment but not elevated EPO levels.
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| 10. |
- Lundgren, Pia, 1967, et al.
(author)
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Visual outcome at 2.5 years of age in ω-3 and ω-6 long-chain polyunsaturated fatty acid supplemented preterm infants: a follow-up of a randomized controlled trial
- 2023
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In: Lancet Regional Health-Europe. - 2666-7762. ; 32
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Journal article (peer-reviewed)abstract
- Background We investigated ophthalmological outcomes at 2.5 years of corrected age in children born extremely preterm (EPT) to evaluate the effects of postnatal enteral supplementation with omega-3 and omega-6 long-chain polyunsaturated fatty acids.Methods In the Mega Donna Mega clinical trial, EPT infants born at less than 28 weeks of gestation were randomized to receive an enteral supplementation of docosahexaenoic acid (DHA) and arachidonic acid (AA) from birth to 40 weeks postmenstrual age. In this exploratory follow-up at 2.5 years of corrected age, we assessed visual acuity (VA), refraction, manifest strabismus, and nystagmus. Satisfactory VA was defined as >= 20/63. Multiple imputation (MI) was used to address the issue of missing data.Findings Of 178 children in the trial, 115 (with median gestational age (GA) of 25 + 4/7 weeks and median birth weights of 790 g) were ophthalmologically assessed at a median corrected age of 2.7 years (range 2.0-3.9 years). VA assessment was missing in 42.1% (75/178), in 41.7% (35/84) of the AA/DHA supplemented infants, and in 42.6% (40/94) of the control infants. After MI and adjustments for GA, study center, plurality, and corrected age at VA exam, no significant effect of AA/DHA supplementation was detected in VA outcome (>= 20/63) (odds ratio 2.16, confidence interval 95% 0.99-4.69, p = 0.053).Interpretation In this randomized controlled trial follow-up, postnatal supplementation with enteral AA/DHA to EPT children did not significantly alter VA at 2.5 years of corrected age. Due to the high loss to follow-up rate and the limited statistical power, additional studies are needed.
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