Lower oxygen saturation alarm limits decrease the severity of retinopathy of prematurity

Nonclinical Bench Performance Testing of a Very Low-Cost Nonelectric Bubble Continuous Positive Airway Pressure (bCPAP) and Blenders Device Designed for Newborn Respiratory Support

Purpose

Bubble continuous positive airway pressure (bCPAP) is often used to treat respiratory distress experienced by some 15 million preterm infants born globally every year. In low- and middle-income countries, improvised bCPAP devices are used, often without a blender that protects the infant from the sequelae of excessive oxygen exposure.

Materials and Methods

The aim of this bench testing was to assess the mechanical safety and performance of the PATH bCPAP and blenders device, which provides a stable and reliable source of pressurized blended gas without the requirement for a source of compressed medical air or electricity. The device includes two fixed ratio blenders: a "low" blend that provides 37% oxygen and a "high" blend that provides 60% oxygen. We performed bench testing to characterize the performance of the bCPAP and blenders, including respiratory circuit verification, blender verification, conditioned humidity testing, and sound measurement.

Results

Test results for all performance variables met the acceptance criteria of our product requirement specification. The device provides a fixed ratio of air and oxygen that is consistent over the entire range of clinically relevant pressures (4 to 8 cmH2O) and remains consistent despite changes in flow (2 to 7 liters per minute). The blend is stable within ± 5% of the blenders' nominal blend ratio when used with a 100% oxygen source, irrespective of the flow and pressure from the oxygen source or the flow and pressure of the blended gas delivered to the neonate. Sound and humidity test results were within specifications.

Conclusion

This very low-cost nonelectric bCPAP and blenders device is optimally designed to deliver a stable and reliable source of pressurized blended gas.

Unmet Need for ROP Screening in Peripheral Rural Areas

Aim

To study the incidence and risk factors associated with retinopathy of prematurity (ROP) at a tertiary care centre in Western India.

Methods

A retrospective review of records of both referred and babies born in our hospital who were screened for ROP within the last 21 months at a tertiary care centre was done. The newborns were screened as per National Neonatology Forum of India guidelines. ROP was classified according to the International Classification for Retinopathy of Prematurity criteria.

Results

A total of 167 neonates were screened with an incidence of ROP of 26.9%. The mean gestational age (GA) and mean birth weight (BW) were 31.89 ± 2.824 weeks and 1538.11 ± 530.84 gm. The mean BW of neonates having any ROP was significantly lower (1296.98gm, p < 0.001), and the mean GA was also significantly lower in ROP babies (30.67 weeks, p < 0.001). O2 supplementation, RDS, IVH, and NEC were the systemic risk factors that significantly correlated with ROP p-value <0.001. On analysis of the correlation of stage of ROP with BW and GA, a significant correlation of −0.307 (p < 0.001) and −0.283 (p < 0.001) was found.

Conclusion

The incidence of ROP in this study is similar to that reported in the literature from other regions. Other than LBW and GA, oxygen supplementation, RDS, IVH, and NEC were significant risk factors associated with ROP.

Comparative cohorts of retinopathy of prematurity outcomes of differing oxygen saturation: real-world outcomes

Objective

An ongoing third epidemic of retinopathy of prematurity (ROP) is contributed largely by developing nations. We describe a cohort of infants in a single neonatal unit where two limits of oxygen saturation were administered, to show real-world outcomes from trend in neonatology for higher oxygen to improve survival.

Methods and analysis

This retrospective, comparative study of prospectively collected data in an ROP screening programme included infants indicated by gestational age ≤32 weeks, birth weight <1501 g, ventilation for 7 days or requiring oxygen >1 month, who underwent dilated fundoscopic examination from age 4 weeks, every 2 weeks until full retinal vascularisation. Infants with ROP were examined weekly and treated where indicated. Data were divided into two epochs. Epoch 1 oxygen saturation targets were [88–92%], epoch 2 targets [90–95% (99%)] with allowance of increase to 20% for several hours after procedures. Outcome measures included development of ROP, treatment, mortality, sepsis and intraventricular haemorrhage.

Results

A total of 651 infants underwent examination between 2003 and 2016. The incidence of ROP in epoch 1 was 29.1% and epoch 2 was 29.3% (p=0.24). ROP progression doubled in epoch 2 (5 vs 11%, p=0.006), proportion of cases treated halved (14% vs 6%, p=0.0005), sepsis was halved (78.5% vs 41.2%, p<0.0001) and intraventricular haemorrhage doubled (20.2% vs 43.8%, p=0.0001) in epoch 2. Mortality was 4% and 0% in epochs 1 and 2, respectively.

Conclusion

Incidence of ROP did not differ, although ROP cases that worsened doubled with higher oxygen targets. ROP cases requiring treatment decreased, as did sepsis and mortality. Intraventricular haemorrhage cases doubled.

Survival rate dependent variations in retinopathy of prematurity treatment rates in very low birth weight infants

As increased oxidative stress causes increased mortality and morbidities like bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP) in very low birth weight infants (VLBWIs), the conundrum of improved survival but increased ROP observed with the high oxygen saturation target range of 91–95% is difficult to explain. To determine the survival rate-dependent variation in ROP treatment rate, 6292 surviving eligible VLBWIs registered in the Korean Neonatal Network were arbitrarily grouped according to the survival rate of infants at 23–24 weeks’ gestation as group I (> 70%, n = 1626), group II (40–70%, n = 2984) and group III (< 40%, n = 1682). Despite significantly higher survival and lower BPD rates in group I than in groups II and III, the ROP treatment rate was higher in group I than in groups II and III. However, the adjusted odds ratios for ROP treatment were not significantly different between the study groups, and the ROP treatment rate in the infants at 23–24 weeks’ gestation was 21-fold higher than the infants at ≥ 27 weeks’ gestation. The controversial association between improved survival and reduced BPD reflecting quality improvement of neonatal intensive care but increased ROP treatment rate might be primarily attributed to the improved survival of the most immature infants.

Adherence to oxygen saturation targets increased in preterm infants when a higher target range and tighter alarm limits were introduced

AIM

European consensus guidelines published in May 2013 recommended a target peripheral capillary oxygen saturation (SpO₂ ) range of 90-95% for preterm infants. These were incorporated into guidelines at the Karolinska University Hospital, Sweden, in November 2013. This study compared clinical practice before and after those local guidelines.

METHODS

We included infants who were born between 23 + 0 and 30 + 6 weeks from January 1, 2013 to December, 31 2015 and received intensive care in two Karolinska units. The lower saturation target of 88-92% and alarm limits of 85-95% used before November 2013 were compared to the new higher saturation target of 90-95% and alarm limits of 89-96%.

RESULTS

Data from 399 infants were analysed. The mean SpO₂ was 92.4% with the higher target (n = 301) and 91.1% with the lower target (n = 98). Using the higher instead of lower target meant that the SpO₂ was within the prescribed target range more frequently (51% versus 30%) and the proportion of time with SpO₂ >95% was increased by 9% (95% confidence interval 7-11%, p < 0.001).

CONCLUSION

The higher saturation target and tighter alarm limits led to higher mean oxygen saturation, increased adherence to the target and increased time with hyperoxaemia.

Retinal microglia - A key player in healthy and diseased retina

Microglia, the resident immune cells of the brain and retina, are constantly engaged in the surveillance of their surrounding neural tissue. During embryonic development they infiltrate the retinal tissues and participate in the phagocytosis of redundant neurons. The contribution of microglia in maintaining the purposeful and functional histo-architecture of the adult retina is indispensable. Within the retinal microenvironment, robust microglial activation is elicited by subtle changes caused by extrinsic and intrinsic factors. When there is a disturbance in the cell-cell communication between microglia and other retinal cells, for example in retinal injury, the activated microglia can manifest actions that can be detrimental. This is evidenced by activated microglia secreting inflammatory mediators that can further aggravate the retinal injury. Microglial activation as a harbinger of a variety of retinal diseases is well documented by many studies. In addition, a change in the microglial phenotype which may be associated with aging, may predispose the retina to age-related diseases. In light of the above, the focus of this review is to highlight the role played by microglia in the healthy and diseased retina, based on findings of our own work and from that of others.

Advances in understanding and management of retinopathy of prematurity

The understanding, diagnosis, and treatment of retinopathy of prematurity have changed in the 70 years since the original description of retrolental fibroplasia associated with high oxygenation. It is now recognized that retinopathy of prematurity differs in appearance worldwide and as ever smaller and younger premature infants survive. New methods are being evaluated to image the retina, diagnose severe retinopathy of prematurity, and determine windows of time for treatment to save eyes and improve visual and neural outcomes. New treatments to promote physiologic retinal vascular development, vascular repair, and inhibit vasoproliferation by regulating proteins involved in vascular endothelial growth factor, insulin-like growth factor, or erythropoietin signaling. Reducing excessive oxidative/nitrosative stress and understanding progenitor cells and neurovascular and glial vascular interactions are being studied.

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.

Very long apnea events in preterm infants

Apnea is nearly universal among very low birth weight (VLBW) infants, and the associated bradycardia and desaturation may have detrimental consequences. We describe here very long (>60 s) central apnea events (VLAs) with bradycardia and desaturation, discovered using a computerized detection system applied to our database of over 100 infant years of electronic signals. Eighty-six VLAs occurred in 29 out of 335 VLBW infants. Eighteen of the 29 infants had a clinical event or condition possibly related to the VLA. Most VLAs occurred while infants were on nasal continuous positive airway pressure, supplemental oxygen, and caffeine. Apnea alarms on the bedside monitor activated in 66% of events, on average 28 s after cessation of breathing. Bradycardia alarms activated late, on average 64 s after cessation of breathing. Before VLAs oxygen saturation was unusually high, and during VLAs oxygen saturation and heart rate fell unusually slowly. We give measures of the relative severity of VLAs and theoretical calculations that describe the rate of decrease of oxygen saturation. A clinical conclusion is that very long apnea (VLA) events with bradycardia and desaturation are not rare. Apnea alarms failed to activate for about one-third of VLAs. It appears that neonatal intensive care unit (NICU) personnel respond quickly to bradycardia alarms but not consistently to apnea alarms. We speculate that more reliable apnea detection systems would improve patient safety in the NICU. A physiological conclusion is that the slow decrease of oxygen saturation is consistent with a physiological model based on assumed high values of initial oxygen saturation.

A randomised controlled trial of an automated oxygen delivery algorithm for preterm neonates receiving supplemental oxygen without mechanical ventilation

Aim

Providing consistent levels of oxygen saturation (SpO₂) for infants in neonatal intensive care units is not easy. This study explored how effectively the Auto-Mixer® algorithm automatically adjusted fraction of inspired oxygen (FiO₂) levels to maintain SpO₂ within an intended range in extremely low birth weight infants receiving supplemental oxygen without mechanical ventilation.

Methods

Twenty extremely low birth weight infants were randomly assigned to the Auto-Mixer® group or the manual intervention group and studied for 12 h. The SpO₂ target was 85–93%, and the outcomes were the percentage of time SpO₂ was within target, SpO₂ variability, SpO₂ >95%, oxygen received and manual interventions.

Results

The percentage of time within intended SpO₂ was 58 ± 4% in the Auto-Mixer® group and 33.7 ± 4.7% in the manual group, SpO₂ >95% was 26.5% vs 54.8%, average SpO₂ and FiO₂ were 89.8% vs 92.2% and 37% vs 44.1%, and manual interventions were 0 vs 80 (p < 0.05). Brief periods of SpO₂ < 85% occurred more frequently in the Auto-Mixer® group.

Conclusion

The Auto-Mixer® effectively increased the percentage of time that SpO₂ was within the intended target range and decreased the time with high SpO₂ in spontaneously breathing extremely low birth weight infants receiving supplemental oxygen.

Preclinical screening for retinopathy of prematurity risk using IGF1 levels at 3 weeks post-partum

Following current recommendations for preventing retinopathy of prematurity (ROP) involves screening a large number of patients. We performed a prospective study to establish a useful screening system for ROP prediction and we have determined that measuring serum levels of IGF1 at week three and the presence of sepsis have a high predictive value for the subsequent development of ROP. A total of 145 premature newborn, with birthweight <1500 g and/or <32 weeks gestational age, were enrolled. 26.9% of them showed some form of retinopathy. A significant association was found between the development of retinopathy and each of the following variables: early gestational age, low birthweight, requiring mechanical ventilation, oxygen treatment, intracranial haemorrhage, sepsis during the first three weeks, bronchopulmonary dysplasia, the need for erythrocyte transfusion, erythropoietin treatment, and low levels of serum IGF1 in the third week. A multiple logistic regression analysis was used to obtain curves for the probability of developing ROP, based on the main factors linked with ROP, namely serum levels of IGF1 and presence of sepsis. Such preclinical screening has the ability to identify patients with high-risk of developing retinopathy and should lead to better prediction for ROP, while at the same time optimising the use of clinical resources, both human and material.

The pathophysiology of retinopathy of prematurity: an update of previous and recent knowledge

Retinopathy of prematurity (ROP) is a disease that can cause blindness in very low birthweight infants. The incidence of ROP is closely correlated with the weight and the gestational age at birth. Despite current therapies, ROP continues to be a highly debilitating disease. Our advancing knowledge of the pathogenesis of ROP has encouraged investigations into new antivasculogenic therapies. The purpose of this article is to review the findings on the pathophysiological mechanisms that contribute to the transition between the first and second phases of ROP and to investigate new potential therapies. Oxygen has been well characterized for the key role that it plays in retinal neoangiogenesis. Low or high levels of pO2 regulate the normal or abnormal production of hypoxia-inducible factor 1 and vascular endothelial growth factors (VEGF), which are the predominant regulators of retinal angiogenesis. Although low oxygen saturation appears to reduce the risk of severe ROP when carefully controlled within the first few weeks of life, the optimal level of saturation still remains uncertain. IGF-1 and Epo are fundamentally required during both phases of ROP, as alterations in their protein levels can modulate disease progression. Therefore, rhIGF-1 and rhEpo were tested for their abilities to prevent the loss of vasculature during the first phase of ROP, whereas anti-VEGF drugs were tested during the second phase. At present, previous hypotheses concerning ROP should be amended with new pathogenetic theories. Studies on the role of genetic components, nitric oxide, adenosine, apelin and β-adrenergic receptor have revealed new possibilities for the treatment of ROP. The genetic hypothesis that single-nucleotide polymorphisms within the β-ARs play an active role in the pathogenesis of ROP suggests the concept of disease prevention using β-blockers. In conclusion, all factors that can mediate the progression from the avascular to the proliferative phase might have significant implications for the further understanding and treatment of ROP.

Temporal quantification of oxygen saturation ranges: an effort to reduce hyperoxia in the neonatal intensive care unit

OBJECTIVE

To reduce exposure to hyperoxia and its associated morbidities in preterm neonates.

STUDY DESIGN

A multidisciplinary group was established to evaluate oxygen exposure in our neonatal intensive care unit. Infants were assigned target saturation ranges and signal extraction technology implemented to temporally quantify achievement of these ranges. The outcomes bronchopulmonary dysplasia/death, retinopathy of prematurity (ROP)/death, severe ROP and ROP requiring surgery were compared in a pre- versus post-intervention evaluation using multivariate analyses.

RESULT

A total of 304 very low birth weight pre-initiative infants were compared with 396 post-initiative infants. Multivariate analyses revealed decreased odds of severe ROP (adjusted odds ratio (OR): 0.41; 95% confidence interval (CI): 0.24-0.72) and ROP requiring surgery (adjusted OR 0.31; 95% CI: 0.17-0.59) post-initiative. No differences in death were observed.

CONCLUSION

Significant reductions in severe ROP and ROP requiring surgery were observed after staff education and implementation of new technology to quantify success in achieving targeted saturations and reinforce principles and practices.

Chronic morbidities of premature newborns

The most important chronic morbidities of premature newborns, deeply influencing quality of life, are retinopathy of prematurity, bronchopulmonary dysplasia, intraventricular hemorrhage and periventricular leukomalacia. Since the rate of premature birth has not decreased in recent years in Hungary, and treatments of these end stage disorders are extremely difficult, prevention gains tremendous significance. Effective prevention is based on detailed knowledge of the pathophysiological mechanisms of these special diseases having multifactorial nature sharing several common risk factors, and one is the pathological angiogenesis. This sensitive system is affected by several stress situations which are the consequences of prematurity leading to abnormal vascular growth. After birth, relative hyperoxia, compared to intrauterine life, and decreasing concentrations of vascular growth factors result in vascular injury, moreover, may cause vessel apoptosis. The consequence of this phenomenon is the activation of hypoxia responsible genes resulting in robust pathological neovascularization and organ damage during the later phase. Saving normal angiogenesis and inhibiting reactive neovascularization may lead to better quality of life in these premature infants. Orv. Hetil., 2013, 154, 1498–1511.

Adherence to oxygenation and ventilation targets in mechanically ventilated premature and sick newborns: a retrospective study

Background

Ventilator treatment exposes newborns to both hyperoxemia and hyperventilation. It is not known how common hyperoxemia and hyperventilation are in neonatal intensive care units in Norway. The purpose of this study was to assess the quality of current care by studying deviations from the target range of charted oxygenation and ventilation parameters in newborns receiving mechanical ventilation.

Methods

Single centre, retrospective chart review that focused on oxygen and ventilator treatment practices.

Results

The bedside intensive care charts of 138 newborns reflected 4978 hours of ventilator time. Arterial blood gases were charted in 1170 samples. In oxygen-supplemented newborns, high arterial pressure of oxygen (PaO₂) values were observed in 87/609 (14%) samples. In extremely premature newborns only 5% of the recorded PaO₂ values were high. Low arterial pressure of CO₂ (PaCO₂) values were recorded in 187/1170 (16%) samples, and 64 (34%) of these were < 4 kPa. Half of all low values were measured in extremely premature newborns. Tidal volumes above the target range were noted in 22% of premature and 20% of full-term newborns.

Conclusions

There was a low prevalence of high PaO₂ values in premature newborns, which increased significantly with gestational age (GA). The prevalence of low PaCO₂ values was highest among extremely premature newborns and decreased with increasing GA. Further studies are needed to identify whether adherence to oxygenation and ventilation targets can be improved by clearer communication and allocation of responsibilities between nurses and physicians.

Effects of oxygen on the development and severity of retinopathy of prematurity

In 1942, when retinopathy of prematurity (ROP) first manifested as retrolental fibroplasia, the technology to monitor or regulate oxygen did not exist, and a fundus examination of preterm infants was not routinely performed. Supplemental, uncontrolled oxygen at birth has since been found to cause retrolental fibroplasia. At the same time, technological advances have made it possible to regulate oxygen and detect early forms of ROP. Nevertheless, despite our better understanding of ROP and ongoing investigations of supplemental therapeutic oxygen, including recent clinical trials (Surfactant, Positive Airway Pressure, Pulse Oximetry Randomized Trial [SUPPORT] and Benefits of Oxygen Saturation Targeting [BOOST]), the best oxygen profiles to reduce ROP risk while optimizing preterm infant health and development remain unknown. This article reviews major studies on oxygen use in preterm infants and the effects on the development of ROP.

The toxigen initiative: targeting oxygen saturation to avoid sequelae in very preterm infants

Supplemental oxygen plays a critical role in the care of infants born at the lower limits of viability, but not without the risk of morbidity resulting from high levels or prolonged exposure.

PURPOSE

The purpose of this quality improvement project was to reduce exposure to hyperoxia as evidenced by SpO2 values within the established target range (88%-92%) among very preterm infants (VPIs) in a level 3 neonatal intensive care unit (NICU). Reducing exposure to hyperoxia in this population of exquisitely vulnerable infants has been associated with reduced morbidity, including retinopathy of prematurity, chronic lung disease, and brain injury.

SUBJECTS

Two populations of interest were identified: VPIs receiving supplemental oxygen and NICU clinicians.

DESIGN

Interventions were employed to (1) improve knowledge regarding hyperoxia and associated outcome sequelae in an interdisciplinary sample of clinicians (pretest posttest design) and (2) reinforce content of the educational intervention by triggering caregiver behaviors to reduce time the VPIs is above target SpO2 range while receiving supplemental oxygen (cohort design).

METHODS

: Retrospective chart review, baseline clinician knowledge assessment, education, posteducation assessment, collaborative rounds with regular feedback citing time VPIs spent above target oxygen saturation levels (SpO2), and evaluation of impact on time infants spent above target SpO2 range aligned with the project purpose.

OUTCOME MEASURES

Pre- and postintervention dependent variables included clinician knowledge of hyperoxia and related evidence as measured by a 24-item multiple-choice Knowledge Assessment Tool before and after attending an educational presentation. Time VPIs were exposed to hyperoxia was evaluated using SpO2 readings and calculating the percentage of time readings were above target range before and after the introduction of educational and behavioral interventions.

PRINCIPAL RESULTS

Outcome 1 was to increase knowledge about hyperoxia among clinician caregivers. Paired-samples t test showed a significant difference between preintervention and postintervention Knowledge Assessment Tool scores (P = .000). Outcome 2 measured reduction in time spent with SpO2 readings above target range. An independent-samples t test was used to compare outcomes in preintervention and postintervention VPI cohorts. Mean time spent with SpO2 greater than target range increased in the postintervention cohort, reaching statistical significance with P = .047.

CONCLUSIONS

Knowledge acquisition on the subject of hyperoxia in VPIs was achieved. Decreasing the percent time VPIs were exposed to hyperoxia was not attained. The postintervention VPI cohort spent more time above the target saturation range despite greater knowledge among clinicians.

Optimal oxygen saturations in preterm infants: a moving target

PURPOSE OF REVIEW

New evidence is emerging to address the continued uncertainty regarding the optimal range to target oxygen saturation levels in preterm infants.

RECENT FINDINGS

A recently published systematic review summarized the existing evidence for currently used oxygen saturation targets in preterm infants and highlighted the paucity of randomized trials addressing this topic. It appears that higher oxygen saturation levels increase the risk of severe retinopathy of prematurity and pulmonary morbidities. However, data regarding the effects of various target ranges on early mortality and long-term neurodevelopmental outcomes are lacking. A collaborative group of investigators from five independent randomized trials was established to answer this question definitively. Although the final analysis will not be available until 2014, interim results from four of these trials revealed an increase in early mortality when the lower oxygen saturation range is targeted. At present, it may be prudent not to target oxygen saturation levels below 90%. Whatever the optimal range, consistently maintaining the newborn's oxygen saturation levels within target proves an additional challenge for providers. Both technological advancements and optimized patient--caregiver ratios may be useful in achieving targeted oxygen saturation goals.

SUMMARY

Defining and maintaining optimal oxygen saturations in preterm infants remains a challenge for clinicians caring for preterm infants. However, ongoing investigative collaborations may soon provide guidance.

Analysis of risk factors for progression to treatment-requiring ROP in a single neonatal intensive care unit: is the exposure time relevant?

OBJECTIVE

Retinopathy of prematurity (ROP) is a multifactorial disease whose pathogenesis is organized in two phases. We hypothesized that postnatal risk factors may differently exert their effect in a phase dependent way.

METHODS

Data obtained from medical records of 93 very low birth weight neonates with stage ≥ 3 ROP were analyzed. Perinatal ROP risk factors were compared between infants with stage 3 ROP not requiring surgery and infants with treatment-requiring ROP with relation to newborn's lifetime exposure.

RESULTS

In the first two weeks and in the whole first month of life length of oxygen administration was an independent risk factor for treatment-requiring ROP. In the first month of life also sepsis was identified as independent risk factor for surgical ROP. Sepsis and Candida pneumonia in the time frame from birth to ROP diagnosis and prolonged mechanical ventilation from diagnosis to prethreshold ROP were associated to treatment-requiring ROP. Blood transfusions are the only risk factor for treatment-requiring ROP identified in all the periods analyzed.

CONCLUSION

Risk factors for ROP play their role since birth. Beside scrupulous oxygen-administration monitoring and prevention of infections, blood transfusions are of primary importance in the development of treatment-requiring ROP.

Effect of the oxygen saturation target on clinical characteristics of early- versus late-onset retinopathy of prematurity

PURPOSE

To investigate the relationship between postmenstrual age of onset of retinopathy of prematurity (ROP) and the need for treatment, while examining the effects of two different neonatal oxygen saturation protocols on this relationship.

METHODS

A retrospective chart review was conducted for eligible inborn infants born before and after the institution of a new oxygen protocol adjusting target oxygen saturation from 90%-99% to 85%-93%. Early versus late-onset ROP was defined as first presence of any stage disease on examination at <36 versus ≥ 36 weeks' postmenstrual age, respectively.

RESULTS

The median birth weight/postmentrual age of infants was 840 g per 26.1 weeks (early-onset ROP) versus 952.5 g per 28 weeks (late-onset ROP; P < 0.01 vs P < 0.01). ROP developed in 119 of 369 (32.2%) of high oxygen target infants, and 100 of 373 (26.8%) infants in the low-target group (P = 0.11). Cumulatively, 35 of 144 (24.3%) of early-onset and 8 of 69 (11.6%) of late-onset patients required treatment (P = 0.03). Maximal severity of disease after treatment, including retinal detachment frequency, was similar in early- and late-onset patients, independent of the oxygen protocol (P = 1.00).

CONCLUSIONS

The clinical behavior of type 1 ROP is similar in early-and late-onset disease, regardless of oxygen saturation targets. Type 1 ROP disease occurred in 11.6% of patients with late-onset ROP.

Hyperoxia in very preterm infants: a systematic review of the literature

Supplemental oxygen plays a critical role in the management of infants born at the lower limit of viability, but not without the risk of complications resulting from high levels or prolonged exposure. Longitudinal studies of very premature infants, born at less than 28 weeks' gestation, establish a clear relationship between pulse oximetry saturation readings above 92%, or hyperoxia, and development of severe retinopathy of prematurity, chronic lung disease, and brain injury. Hyperoxia is neither natural nor random. It is an unintended consequence of intervention. A comprehensive review of the literature reveals a strong association between exposure to hyperoxia and subsequent expression of comorbidities. Owing to this knowledge, eradication of hyperoxia, and consequent reduction of sequelae, is a significant public health concern that deserves attention by the neonatal community. Although prospective, collaborative meta-analyses will soon provide needed additional data to inform practice, existing compelling evidence supports urgent practice change to reduce exposure to hyperoxia in very preterm infants.

Infection, oxygen, and immaturity: interacting risk factors for retinopathy of prematurity

BACKGROUND

Interactions among known risk factors for retinopathy of prematurity (ROP) remain to be clarified.

OBJECTIVES

The aim of this study was to identify risk factors associated with ROP and to explore the interrelationships between prominent risk factors for ROP.

METHODS

From an institutional cohort of 1,646 very preterm newborns with gestational age <30 weeks or birth weight <1,501 g, we selected infants with a gestational age <30 weeks who met the criteria for ROP screening (n = 622) for a nested case-control analysis.

RESULTS

Of the 622 eligible newborns, 293 (47%) were diagnosed with ROP. From multivariable analyses, gestational age <26 weeks (OR 2.9, CI 1.7-4.9), oxygen exposure at 28 days (OR 1.7, CI 1.0-2.7), and neonatal sepsis (OR 2.1, CI 1.4-3.2) emerged as prominent risk factors for ROP. Oxygen- associated ROP risk was more prominent among infants of 23-25 weeks' gestational age, while infection-associated ROP risk was higher among infants born at 28-29 weeks. The OR for the joint effect of all 3 risk factors (23.5) was higher than would have been expected under the additive (8.6) and the multiplicative (16.5) patterns of interaction.

CONCLUSIONS

Our study suggests that neonatal sepsis, oxygen exposure, and low gestational age are not only independently associated with a significantly increased risk of ROP, but also interact beyond additive and even multiplicative patterns.

Blood gases and retinopathy of prematurity: the ELGAN Study

OBJECTIVE

This study tested the hypothesis that preterm infants who had a blood gas derangement on at least 2 of the first 3 postnatal days are at increased risk for more severe retinopathy of prematurity (ROP).

METHOD

1,042 infants born before 28 weeks' gestational age (GA) were included. An infant was considered to be exposed if his/her blood gas measure was in the highest or lowest quartile for GA on at least 2 of the first 3 postnatal days.

RESULTS

Multivariable models adjusting for confounders indicate that exposure to a PCO(2) in the highest quartile predicts ROP (stage 3, 4 or 5: OR = 1.6, 95% CI = 1.1-2.3); zone 1: 2.0, 1.1-3.6; prethreshold/threshold: 1.9, 1.2-3.0; plus disease: 1.8, 1.1-2.9). Estimates are similar for a low pH for zone 1 (2.1, 1.2-3.8), prethreshold/threshold (1.8, 1.1-2.8), but did not quite achieve statistical significance for ROP stage 3, 4, or 5 (1.4, 0.9-2.0) and plus disease (1.5, 0.9-2.4). A PaO(2) in the highest quartile for GA on at least 2 of the first 3 postnatal days was associated with a doubling of the risk of ROP in zone 1 (2.5, 1.4-4.4) and of prethreshold/threshold disease (2.1, 1.4-3.3), a 70% risk increase for plus disease (1.7, 1.04-2.8), while a 40% risk increase for ROP stage 3 or higher did not achieve statistical significance (1.4, 0.96-2.0).

CONCLUSION

Infants exposed to high PCO(2), low pH and high PaO(2) appear to be at increased risk of more severe ROP.

Effect of decreasing target oxygen saturation on retinopathy of prematurity

INTRODUCTION

The authors of previous studies suggest that the oxygenation status of premature infants contributes to the development of retinopathy of prematurity (ROP). In this study we compared the incidence and severity of ROP before and after institution of a new neonatal intensive care unit oxygen protocol.

METHODS

A retrospective chart review was performed of all eligible inborn patients screened for ROP during the 2 years immediately before (Group 1) to and the 2 years after (Group 2) the initiation of a new oxygen protocol. In the new protocol, target oxygen saturation was adjusted from 90%-99% to 85%-93%. Treatment criteria adhered to Early Treatment for Retinopathy of Prematurity guidelines for the study's duration.

RESULTS

There were 387 infants in Group 1 and 386 infants in Group 2 (descriptive statistics adjusted for correlation due to multiple births). Mean birth weights (BWs) and gestational ages were 1,194 g and 29.2 weeks (ranges, 525-2,085 g; 23 2/7-39 6/7 weeks) for Group 1 and 1,139 g and 28.9 weeks (ranges, 520-2,500 g; 22 6/7-35 3/7 weeks) for Group 2 (p = 0.02/0.10). ROP developed in 32.7% of infants in Group 1 and 27.8% in Group 2 (p = 0.17). The incidence of ROP requiring treatment was 19.9% in Group 1 and 20.5% in Group 2 (p = 0.91). Subanalysis of infants with BW ≤ 1,000g (Group 1, n = 119; Group 2, n = 141) revealed ROP incidence of 75.1% versus 57.1%, respectively (p < 0.01); treatable disease occurred in 37.5% and 21.9% of affected infants (p = 0.19).

CONCLUSIONS

Lowering target oxygen saturation for inborn premature infants was associated with decreased incidence of ROP only in infants with BW ≤ 1,000 g. Severity of disease, including need for treatment, was similar in both groups.

High or low oxygen saturation and severe retinopathy of prematurity: a meta-analysis

CONTEXT

Low oxygen saturation appears to decrease the risk of severe retinopathy of prematurity (ROP) in preterm newborns when administered during the first few weeks after birth. High oxygen saturation seems to reduce the risk at later postmenstrual ages (PMAs). However, previous clinical studies are not conclusive individually.

OBJECTIVE

To perform a systematic review and meta-analysis to report the association between severe ROP incidence of premature infants with high or low target oxygen saturation measured by pulse oximetry.

METHODS

Studies were identified through PubMed and Embase literature searches through May 2009 by using the terms "retinopathy of prematurity and oxygen" or "retinopathy of prematurity and oxygen therapy." We selected 10 publications addressing the association between severe ROP and target oxygen saturation measured by pulse oximetry. Using a random-effects model we calculated the summary-effect estimate. We visually inspected funnel plots to examine possible publication bias.

RESULTS

Low oxygen saturation (70%-96%) in the first several postnatal weeks was associated with a reduced risk of severe ROP (risk ratio [RR]: 0.48 [95% confidence interval (CI): 0.31-0.75]). High oxygen saturation (94%-99%) at > or = 32 weeks' PMA was associated with a decreased risk for progression to severe ROP (RR: 0.54 [95% CI: 0.35-0.82]).

CONCLUSIONS

Among preterm infants with a gestational age of < or = 32 weeks, early low and late high oxygen saturation were associated with a reduced risk for severe ROP. We feel that a large randomized clinical trial with long-term developmental follow-up is warranted to confirm this meta-analytic result.

The influence of early postnatal nutrition on retinopathy of prematurity in extremely low birth weight infants

BACKGROUND

Retinopathy of prematurity(ROP) is the most common serious ophthalmic disease in preterm infants. Human milk may provide a protective effect for ROP; however, beneficial effects of human milk preclude randomized trials. Therefore, we conducted a retrospective analysis comparing early postnatal nutrition with ROP development.

OBJECTIVE

Evaluate relationship between early postnatal nutriture and ROP surgery.

DESIGN/METHODS

Nutrition data was collected for inborn AGA infants, BW 700-1000 g. ROP surgery was the primary outcome variable. A single pediatric ophthalmologist supervised examinations. All infants received triweekly IM vitamin A as chronic lung disease prophylaxis (Tyson: NEJM, 1999).

RESULTS

BW and gestational age were 867+/-85 g and 26.3+/-1.2 weeks (n=77, mean+/-1SD). ROP surgery infants(n=11) received more parenteral nutrition, 1648 mL, and less human milk, 13.8 mL/kg-day, and vitamin E, 1.4 mg/kg-day, during the second postnatal week. Human milk was a negative predictor for ROP surgery, odds ratio=0.94. Both groups met vitamin A recommendations; however, 74% was administered via IM injections. Neither group met vitamin E recommendations.

CONCLUSIONS

Human milk feeding, parenteral nutrition volume and vitamin E intake were predictors for ROP surgery. IM vitamin A injections provided the majority of vitamin A; vitamin E administration was insufficient. Improving human milk feeding rates and vitamin dosing options may affect ROP surgery rates.

Crossing the quality chasm in neonatal-perinatal medicine

The "Quality Chasm" exists in neonatal intensive care. Despite years of clinical research in neonatology, therapies continue to be underused, overused, or misused. A key concept in crossing the quality chasm is system redesign. The unpredictability of human factors and the dynamic complexity of the neonatal ICU are not amenable to rigid reductionist control and redesign. Change is best accomplished in this complex adaptive system by use of simple rules: (1) general direction pointing, (2) prohibitions, (3) resource or permission providing. These rules create conditions for purposeful self-organizing behavior, allowing widespread natural experimentation, all focused on generating the desired outcome.

Comprehensive Oxygen Management for the Prevention of Retinopathy of Prematurity: the pediatrix experience

Comprehensive oxygen management, focused on avoiding hyperoxia and repeated episodes of hypoxia-hyperoxia in very low birth weight infants, has been successfully used for the reduction of retinopathy of prematurity. Building on this experience, the Comprehensive Oxygen Management for the Prevention of Retinopathy of Prematurity quality improvement initiative was developed to facilitate the spread and refinement of these techniques. The initiative focused on staff education and evaluation and redesign of the processes and practices involving oxygen use. Monitoring of the effectiveness of the system changes was supported through audits of clinical practice changes, use of oxygen saturation trending data, and the incidence of retinopathy of prematurity.

The effects of oxygen stresses on the development of features of severe retinopathy of prematurity: knowledge from the 50/10 OIR model

The objective of this study is to determine growth factor expression and activation of signaling pathways associated with intravitreous neovascularization and peripheral avascular retina using a model of retinopathy of prematurity (ROP) relevant to today with oxygen monitoring in neonatal units. Studies using 50/10 oxygen-induced retinopathy (OIR) and 50/10 OIR+SO models were reviewed. Repeated fluctuations in oxygen increased retinal vascular endothelial growth factor (VEGF) even while peripheral avascular retina persisted and prior to the development of intravitreous neovascularization. Repeated fluctuations in oxygen increased VEGF(164) expression but not VEGF(120). Neutralizing VEGF bioactivity significantly reduced intravitreous neovascularization and arteriolar tortuosity without interfering with ongoing retinal vascularization. Repeated oxygen fluctuations led to retinal hypoxia and increased reactive oxygen species (ROS). Inhibiting ROS with NADPH oxidase inhibitor, apocynin, reduced avascular retina by interfering with apoptosis. Supplemental oxygen reduced retinal VEGF concentration and exacerbated NADPH oxidase activation to contribute to intravitreous neovascularization through activation of the JAK/STAT pathway. Oxygen stresses relevant to those experienced by preterm infants today trigger signaling of different pathways to cause avascular retina and intravitreous neovascularization. Increased signaling of VEGF appears important to the development of both avascular retina and intravitreous neovascularization.

Reduced oxygen protocol decreases the incidence of threshold retinopathy of prematurity in infants of <33 weeks gestation

BACKGROUND

The relationship between oxygen and retinopathy of prematurity (ROP) has been studied frequently, and a pulse oximeter has the potential to facilitate the control of oxygen fluctuation in neonates. The objective of the present study was to compare the incidence of threshold ROP (stage 3 requiring laser treatment and stage 4) in infants of <33 weeks gestation after implementing a new clinical O(2) management practice.

METHODS

A retrospective study of data from the Kyoto First Red Cross Hospital neonatal intensive care unit (NICU) from 1 July 2004 to 31 October 2007 (closed 1 December 2006-30 March 2007 for reconstruction). A reduced oxygen protocol was implemented to maintain oxygen saturation (SpO(2)) values using a pulse oximeter between 88% and 92%. The incidence of threshold ROP in the earlier period (1 July 2004-31 December 2005) and the later period (1 January 2006-31 October 2007) were compared.

RESULTS

The incidence of threshold ROP significantly decreased from 32.2% to 16.7%, after changing to the reduced oxygen protocol (P < 0.05).

CONCLUSION

A significant decrease in the rate of threshold ROP in infants of <33 weeks gestation was observed after implementation of the new clinical O(2) management practice.

The neurovascular retina in retinopathy of prematurity

The continuing worldwide epidemic of retinopathy of prematurity (ROP), a leading cause of childhood visual impairment, strongly motivates further research into mechanisms of the disease. Although the hallmark of ROP is abnormal retinal vasculature, a growing body of evidence supports a critical role for the neural retina in the ROP disease process. The age of onset of ROP coincides with the rapid developmental increase in rod photoreceptor outer segment length and rhodopsin content of the retina with escalation of energy demands. Using a combination of non-invasive electroretinographic (ERG), psychophysical, and image analysis procedures, the neural retina and its vasculature have been studied in prematurely born human subjects, both with and without ROP, and in rats that model the key vascular and neural parameters found in human ROP subjects. These data are compared to comprehensive numeric summaries of the neural and vascular features in normally developing human and rat retina. In rats, biochemical, anatomical, and molecular biological investigations are paired with the non-invasive assessments. ROP, even if mild, primarily and persistently alters the structure and function of photoreceptors. Post-receptor neurons and retinal vasculature, which are intimately related, are also affected by ROP; conspicuous neurovascular abnormalities disappear, but subtle structural anomalies and functional deficits may persist years after clinical ROP resolves. The data from human subjects and rat models identify photoreceptor and post-receptor targets for interventions that promise improved outcomes for children at risk for ROP.

Retinopathy of prematurity

This article briefly reviews the history of ROP followed by a discussion of the pathogenesis of this complex disorder. We describe the International Classification System for ROP and identify risk factors and screening recommendations. Finally, we discuss some of the measures that have been used in an attempt to both prevent and treat ROP.

Effects of low oxygen saturation limits on the ductus arteriosus in extremely low birth weight infants

OBJECTIVE

Postnatal increase in oxygen promotes constriction of the patent ductus arteriosus (PDA). According to the findings of prospective observational studies, the clinical practice of targeting lower fractional oxygen saturation between 70 and 90% has been associated with a reduced incidence of severe retinopathy of prematurity (ROP) without affecting survival or neurodevelopmental disability at 1 year of age. Our objective was to investigate the impact of the use of a lower oxygen saturation target range on the incidence of early hemodynamically significant PDA (hsPDA) and the need for ductal ligation in extremely low birth weight (ELBW, <1000 g) infants.

STUDY DESIGN

In this retrospective study, we analyzed data from 263 ELBW infants managed 4 years before (episode I: target oxygen saturation 89 to 94%) and after (episode II: target oxygen saturation 83 to 89%) implementation of the use of lower oxygen saturation limits in two neonatal intensive care units. Infants with a birth weight of 1000 to 1500 g were managed with the same oxygen saturation target range (89 to 94%) during both episodes, and they served as controls. Parametric and nonparametric tests were used as appropriate and multivariate logistic regression models were used to correct for confounders.

RESULTS

There was an increase in the incidence of hsPDA (63.2 vs 74.8%, P=0.043), without an increase in the need for surgical ligation (24.2 vs 29.9%, P=0.3) after implementation of the lower oxygen saturation target range policy. After adjusting for confounders, there was an increase in the odds of having an hsPDA (odds ratio (OR) 1.77, 95% confidence interval (CI) (1.03 to 3.06), P=0.04) but the odds for ductal ligation did not change in episode II (OR 1.25, 95% CI (0.70 to 2.25), P=0.4). The incidence of ROP > or = stage III (50.7 vs 15.7%; P<0.0001) and the need for laser ablation (33.8% vs 8.7%; P<0.0001) were significantly reduced. There was no change in the incidence of hsPDA or ductal ligation in the control group.

CONCLUSION

Targeting lower oxygen saturation limits to minimize periods of hyperoxemia in ELBW infants reduced the incidence of severe ROP and the need for laser ablation. The incidence of early hsPDA was increased; however, final closure rate and the incidence of surgical ligation of the ductus arteriosus were not affected.

[Risk factors and prevention of retinopathy of prematurity]

The history of retinopathy of prematurity (ROP) gives a prime example of how dangerous the uncontrolled introduction of a new medical treatment--particularly in the field of neonatology--may be. The most important risk factors for the development of ROP are the immaturity of premature infants as well as uncontrolled and/or inadequate treatment with oxygen. In comparison to the fetus, the premature infant is exposed to a nonphysiologically high oxygen concentration. This hyperoxia leads to formation of aggressive oxygen radicals on the one hand and, on the other hand, to temporarily reduced production of growth factors such as vascular endothelial growth factor and erythropoietin, which both play an important role in the pathogenesis of ROP. The most important measure to prevent ROP is restrictive and carefully monitored oxygen treatment. Medical treatment to prevent ROP includes injection of D-penicillamine and retinol, but the available data are still limited, particularly with regard to the long-term effects of this treatment. A higher oxygenation in prethreshold ROP does not lead to recovery of ocular findings, but it increases the incidence of pulmonary complications. A reduction of light intensity in neonatal intensive care units proved not to be efficient for preventing ROP. To avoid blindness, standardized screening of the risk group is needed.

Oxygen saturation monitoring for the preterm infant: the evidence basis for current practice

Many of the morbid conditions associated with extreme immaturity are potentiated by an excess of free radicals occurring in infants who developmentally have decreased levels of antioxidants. The optimal oxygen saturation values for the resuscitation, stabilization, and ongoing care of the very low birth weight infant remain largely undefined. We have reviewed the currently available evidence for clinical oxygen use in the newborn period. Until the results of further studies are available, a reasonable approach to resuscitation would include initial resuscitation with 30-40% oxygen for very preterm infants using targeted SpO2 values and blended oxygen during the first 10 min. For ongoing management of preterm infants, SpO2 targets of 85-93% seem to be most appropriate, with alarm limits set within 1 to 2% of these targets with intermittent audits to ensure compliance. There is no strong evidence to support the use of altered limits for the infant who develops early evidence of retinopathy of prematurity. Further prospective studies are required to evaluate the effects of varied oxygen targets on long-term outcome.

The role of supplemental oxygen and JAK/STAT signaling in intravitreous neovascularization in a ROP rat model

PURPOSE

To investigate whether oxygen stresses experienced in retinopathy of prematurity (ROP) trigger signaling through reactive oxygen species (ROS) and whether the Janus kinase-signal transducer and activator of transcription (JAK/STAT) pathway lead to intravitreous neovascularization (IVNV) in an oxygen-induced retinopathy (OIR) rat model.

METHODS

Newborn rat pups exposed to repeated fluctuations in oxygen and rescued in supplemental oxygen (28% O(2), 50/10 OIR+SO) were treated with apocynin, an NADPH oxidase and ROS inhibitor (10 mg/kg/d), AG490, a JAK2 inhibitor (5 mg/kg/d), or phosphate-buffered saline. Intraperitoneal injections were given from postnatal day (P)12 to P17 (apocynin), or from P3 to P17 (AG490). Outcomes were intravitreous neovascularization and avascular/total retinal areas, vascular endothelial growth factor, phosphorylated JAK2, and phosphorylated STAT3.

RESULTS

Apocynin significantly reduced phosphorylated STAT3 in 50/10 OIR+SO (P = 0.04), in association with previously reported inhibition of the IVNV area. Inhibition of JAK with AG490 significantly reduced phosphorylated JAK2 (P < 0.001), phosphorylated STAT3 (P = 0.002), and IVNV area (P = 0.033) in the 50/10 OIR+SO model compared with control.

CONCLUSIONS

Activation of NADPH oxidase from supplemental oxygen works through activated STAT3 to lead to IVNV. In addition, inhibition of the JAK/STAT pathway reduces IVNV. Further studies are needed to determine the effects and relationships of oxygen stresses on JAK/STAT and NAPDH oxidase signaling.

Retinal degenerative and hypoxic ischemic disease

A broad spectrum of retinal diseases affects both the retinal vasculature and the neural retina, including photoreceptor and postreceptor layers. The accepted clinical hallmarks of acute retinopathy of prematurity (ROP) are dilation and tortuosity of the retinal vasculature. Additionally, significant early and persistent effects on photoreceptor and postreceptor neural structures and function are demonstrated in ROP. In this paper, we focus on the results of longitudinal studies of electroretinographic (ERG) and vascular features in rats with induced retinopathies that model the gamut of human ROP, mild to severe. Two potential targets for pharmaceutical interventions emerge from the observations. The first target is immature photoreceptors because the status of the photoreceptors at an early age predicts later vascular outcome; this approach is appealing as it holds promise to prevent ROP. The second target is the interplay of the neural and vascular retinal networks, which develop cooperatively. Beneficial pharmaceutical interventions may be measured in improved visual outcome as well as lessening of the vascular abnormalities.

Pulse oxygen saturation levels and arterial oxygen tension values in newborns receiving oxygen therapy in the neonatal intensive care unit: is 85% to 93% an acceptable range?

OBJECTIVE

Our aim was to define the relationship of PaO(2) and pulse oxygen saturation values during routine clinical practice and to evaluate whether pulse oxygen saturation values between 85% and 93% were associated with PaO(2) levels of <40 mmHg.

METHODS

Prospective comparison of PaO(2) and pulse oxygen saturation values in 7 NICUs at sea level in 2 countries was performed. The PaO(2) measurements were obtained from indwelling arterial catheters; simultaneous pulse oxygen saturation values were recorded if the pulse oxygen saturation values changed <1% before, during, and after the arterial gas sample was obtained.

RESULTS

We evaluated 976 paired PaO(2)/pulse oxygen saturation values in 122 neonates. Of the 976 samples, 176 (18%) from infants breathing room air had a mean pulse oxygen saturation of 93.9 +/- 4.3% and a median of 95.5%. The analysis of 800 samples from infants breathing supplemental oxygen revealed that, when pulse oxygen saturation values were 85% to 93%, the mean PaO(2) was 56 +/- 14.7 mmHg and the median 54 mmHg. At this pulse oxygen saturation level, 86.8% of the samples had PaO(2) values of 40 to 80 mmHg, 8.6% had values of <40 mmHg, and 4.6% had values of >80 mmHg. When the pulse oxygen saturation values were >93%, the mean PaO(2) was 107.3 +/- 59.3 mmHg and the median 91 mmHg. At this pulse oxygen saturation level, 39.5% of the samples had PaO(2) values of 40 to 80 mmHg and 59.5% had values of >80 mmHg.

CONCLUSIONS

High PaO(2) occurs very rarely in neonates breathing supplemental oxygen when their pulse oxygen saturation values are 85% to 93%. This pulse oxygen saturation range also is infrequently associated with low PaO(2) values. Pulse oxygen saturation values of >93% are frequently associated with PaO(2) values of >80 mmHg, which may be of risk for some newborns receiving supplemental oxygen.

Clinical practices in neonatal oxygenation: where have we failed? What can we do?

INTRODUCTION

Oxygen is among the most frequently used therapies in neonates worldwide. Nevertheless, many times it is used unnecessarily. Neonatal practices have changed over the last several years; treatments originally believed to be beneficial have been discarded.

STUDY DESIGN

Oxygen utilized 'just in case' or 'prophylactically' can lead to great damage previously ignored and/or unseen by healthcare providers. It is imperative to improve education on neonatal oxygenation and saturation monitoring. It is also important not to depend on old assumptions, which were not based on evidences. The potential for unseen damage at the cellular and tissue levels cannot be ignored. Therapies that prove to be outdated or even dangerous must be eliminated while further research and confirmation of the best practices are determined. Freedom to choose can come at a price.

Retinopathy of prematurity: the disease process, classifications, screening, treatment, and outcomes

Retinopathy of prematurity (ROP) is the cessation of normal eye development and subsequent abnormal vessel growth that occurs exclusively in premature infants. ROP was first discovered in the 1940s and was for two decades the leading cause of blindness in children. Currently, the disease causes about 500 new cases of blindness per year. The severity of the disease increases with decreasing gestational age. The pathogenesis of ROP involves disruption of normal retinal vascularization. Vessel endothelial growth factor, insulin-like growth factor, and oxygen play important roles in its development. ROP is classified using an international classification system that provides direction for screening and treatment of premature infants. Examinations are performed by ophthalmologists, who identify the scope of vascularization, the degree of abnormal vessel growth, and the amount of the eye that is affected. Treatment modalities include cryosurgery and laser photocoagulation. Long-term outcomes include both structural and functional vision problems.

Pulmonary artery hypertension in formerly premature infants with bronchopulmonary dysplasia: clinical features and outcomes in the surfactant era

BACKGROUND

Although abnormal pulmonary vascular structure and function in preterm infants with bronchopulmonary dysplasia may predispose infants to pulmonary artery hypertension, little is known about the characteristics and outcomes of bronchopulmonary dysplasia-associated pulmonary artery hypertension in the surfactant era.

METHODS

We studied 42 premature infants (< 32 weeks of gestation) with bronchopulmonary dysplasia who were diagnosed as having pulmonary artery hypertension > or = 2 months after birth, between 1998 and 2006, at a median age of 4.8 months. Pulmonary artery hypertension was graded through echocardiography for all patients; 13 patients also underwent cardiac catheterization.

RESULTS

Eighteen (43%) of 42 patients had severe pulmonary artery hypertension (systemic or suprasystemic right ventricular pressure). Among 13 patients who underwent catheterization, the mean pulmonary artery pressure was 43 +/- 8 mmHg and the pulmonary vascular resistance index was 9.9 +/- 2.8 Wood units. In 12 patients, pulmonary artery pressure and pulmonary vascular resistance improved with 100% oxygen and 80 ppm inhaled nitric oxide but remained elevated. The pulmonary vascular resistance index decreased to 7.9 +/- 3.8 Wood units in 100% oxygen and to 6.4 +/- 3.1 Wood units with the addition of nitric oxide. Sixteen patients (38%) died during the follow-up period. Estimated survival rates were 64% +/- 8% at 6 months and 53% +/- 11% at 2 years after diagnosis of pulmonary artery hypertension. In multivariate analyses, severe pulmonary artery hypertension and small birth weight for gestational age were associated with worse survival rates. Among 26 survivors (median follow-up period: 9.8 months), pulmonary artery hypertension was improved, relative to its most severe level, in 24 patients (89%).

CONCLUSION

Premature infants with bronchopulmonary dysplasia and severe pulmonary artery hypertension are at high risk of death, particularly during the first 6 months after diagnosis of pulmonary artery hypertension.

Anatomical and visual outcome of stages 4 and 5 retinopathy of prematurity

AIM

To describe our experience in surgical management of stages 4 and 5 retinopathy of prematurity (ROP) and assess its anatomical and visual outcome.

MATERIALS AND METHODS

This study is a retrospective, interventional, consecutive case series. It involved 33 eyes of 29 infants. The data were retrieved retrospectively for each case from their medical records. All the eyes underwent primary vitrectomy with additional procedures like scleral buckling (two eyes), lensectomy (14 eyes), subretinal fluid drainage (two eyes), and one case of corneal transplant (open sky vitrectomy). The anatomical and visual outcome was reviewed at the final follow-up.

RESULTS

The mean gestational age was 29.7 weeks (range 25-34 weeks) and mean birth weight was 1332 g (range 650-2050 g). Anatomical success for stage 4A was defined as complete retinal attachment with undistorted or minimally distorted posterior pole. For stage 4B, partial residual retinal detachment and for stage 5 at least posterior pole attachment. Visual acuity was measured in anatomically successful eyes that were cooperative. The anatomical outcome was 90% (9/10 eyes) for stage 4A, 44.4% (4/9 eyes) for stage 4B, and 14.3% (2/14) for stage 5. The mean follow-up was 19.1 months. Posterior retinotomy was the commonest complication for stage 4B (66.7%).

CONCLUSION

Anatomical and visual success was the best for stage 4A ROP. Surgery for stage 4A can halt progression to stages 4B or 5 ROP. Aggressive peeling of posterior membranes should be avoided for stage 4B. Anatomical and visual outcome is very poor for stage 5.

Hyperoxia inhibits several critical aspects of vascular development

Normal human retinal vascular development uses angiogenesis and vasculogenesis, both of which are interrupted in the vaso-obliteration phase of retinopathy of prematurity (ROP). Canine oxygen-induced retinopathy (OIR) closely resembles human ROP. Canine retinal endothelial cells (ECs) and angioblasts were used to model OIR and characterize the effects of hyperoxia on angiogenesis and vasculogenesis. Cell cycle analysis showed that hyperoxia reduced the number of G1 phase cells and showed increased arrest in S phase for both cell types. Migration of ECs was significantly inhibited in hyperoxia (P < 0.01). Hyperoxia disrupted the cytoskeleton of angioblasts but not ECs after 2 days. Differentiation of angioblasts into ECs (determined by acetylated low-density lipoprotein uptake) was evaluated after basic fibroblast growth factor treatment. Differentiation of angioblasts into pericytes was determined by smooth muscle actin expression after treatment with platelet-derived growth factor. Differentiation into ECs was significantly inhibited by hyperoxia (P < 0.0001). The percentage of CXCR4(+) cells (a marker for retinal vascular precursors) increased in both treatment groups after hyperoxia. These data show novel mechanisms of hyperoxia-induced disruption of vascular development.