Oxygen Monitoring Reduces the Risk for Retinopathy of Prematurity in a Mexican Population.
- Clinic of Retinopathy of Prematurity and Blindness Prevention, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, Mexico.
Retinopathy of prematurity (ROP), a potentially blinding disease, affects preterm infants. High levels of oxygen saturation are a well-known risk factor for ROP.
To assess the frequency of ROP type 1 needing treatment after improved oxygen monitoring (2011) in a Mexican preterm population selected for WINROP analyses and to retrospectively revalidate WINROP, an online surveillance system identifying infants at risk of developing ROP type 1.
Preterm infants born with birth weight (BW) <1,750 g and/or at gestational age (GA) ≤34 weeks, screened for ROP in 2012-2014 at the Hospital Civil de Guadalajara, Mexico were included (n = 151). Eighty-five infants with GA <32 weeks qualified for WINROP analyses. GA, BW, maximal ROP stage, ROP treatment and weekly weights were recorded. The results in the present study were compared to those of a previous WINROP study in the same hospital (2005-2010; n = 352).
In the present WINROP cohort, 11.8% of the infants born at GA <32 weeks received treatment compared to 51.0% of the infants in the previous WINROP cohort. One infant (3%) born at GA ≥32 weeks received treatment during the present study period compared to 35.6% during the previous period. WINROP displayed 80.0% sensitivity in infants born at GA <32 weeks in the present study compared to 84.7% in the previous study.
Uncontrolled oxygen supplementation is the major risk factor for severe ROP in infants born at GA ≥32 weeks. After improved oxygen monitoring, the frequency of ROP treatment was dramatically reduced at the Hospital Civil de Guadalajara, Mexico.
© 2016 S. Karger AG, Basel.
- PMID: 27088589
Retinopathy of prematurity (ROP) arises when abnormal vascularization occurs in the maturing retina in preterm infants. ROP causes blindness or severe visual impairment in approximately 20 000 infants each year around the world . In most cases, blindness caused by ROP is preventable by timely detection and treatment. Gestational age (GA) and birth weight (BW) are well-known major risk factors for ROP that reflect the infants’ degree of immaturity  and most commonly used ROP screening guidelines are based on GA and/or BW. However, while the quality of neonatal care is improving, not all neonatal intensive care units (NICUs) have ROP screening programs, adequate screening equipment, and ophthalmologists who are trained to detect and treat ROP . Zepeda-Romero et al. reported that in Guadalajara city, Mexico, only 50% of the NICU’s had a regular ROP program. In schools for the visually impaired in Guadalajara city more than 40% of the children (under the age of 5 years) were blind due to ROP. The majority of these infants had not been treated for ROP .
Excessive oxygen supplementation was the first identified and best-known risk factor for ROP  and caused the “first epidemic” of ROP in the 1950’s. A “new epidemic” of ROP is presently being seen in middle income regions, such as Latin America, Asia and Eastern Europe, where neonatal care is still developing [3,6]. ROP is increasing around the world again due to lack of basic equipment for administration/ monitoring of oxygen and insufficient training. However several studies have showed the favorable impact of improved oxygen administration and personal education on ROP rates [7,8].
In settings with advanced neonatal care, poor pre- and postnatal weight gain have been found to predict severe ROP [9-11]. Based on these findings, WINROP (weight, insulin-like growth factor-1, and neonatal ROP) was developed in Gotheburg, Sweden, as a prediction tool for severe ROP based on postnatal weight development. By recording the infant’s BW and GA along with weekly weight measurements, WINROP accumulates and calculates the infant’s risk of developing severe ROP that requires treatment. The WINROP system has an alarm function that signals if an infant is at high risk of developing ROP requiring treatment. Even if WINROP does not give this signal, weekly weight measurements must be performed until the infant is at PMA 33–34 weeks. Not until then can the infant be completely free of risk as evaluated by WINROP. WINROP is free of charge. The sensitivity and specificity of WINROP varies slightly between the cohorts; this is proposed to be due to the characteristics of the infants that are born preterm. WINROP could predict severe ROP with high sensitivity in settings with highly developed neonatal care, [12-14] but with lower sensitivity in settings with poor oxygen control . It has been suggested that WINROP could be more useful if it was adapted to the characteristics of different populations . WINROP is meant to be a supplement to rather than a substitute for established ROP screening practices. The aim of WINROP is to safely minimize the number of ROP screening examinations in infants at low risk of ROP requiring treatment and to alert physicians to infants who are at high risk.
The study presented was initiated as a consequence of a previously performed study; a WINROP validation of infants screened for ROP at the NICU at the Hospital Civil de Guadalajara, Mexico in 2005˗2010. This prior WINROP study (2005˗2010) alerted the clinicians to the high ROP rates at the NICU, and the infants exposure to high levels of oxygen saturations were evaluated. Several implements and improvements concerning monitoring and control of oxygen supplementation were initiated at the NICU in 2011, such as installation of individual infant oxygen pulse oximeters for constant surveillance (in 2005-2010 oxygen saturations were monitored but not on an individual constant basis). In 2011 the target saturation was set to 85-95% and alarms were set to ring when oxygen saturationns reached 90-95% (in 2005-2010 oxygen saturation was set at a minimum of 85% and most infants reached 100% oxygen saturation). Additional education to the neonatologists and nurses at the NICU was initiated.
In the present study, including infants screened for ROP at NICU at the Hospital Civil de Guadalajara, Mexico in 2012-2014 the frequency of ROP treatment was dramatically reduced to 9.3% compared to 44.0% at the same NICU in 2005-2010. In 2012-2014 only one infant (3%) over the GA of 32 weeks needed ROP treatment compared to 36% in 2005-2010. We believe that the dramatic reduction in ROP frequency reflects that unrestricted oxygen supplementation is a major risk factor for ROP, especially for the more mature infants. The WINROP sensitivity was similar between the study cohorts and lower than in earlier studies performed in Sweden and in North America. We suspect that innacurate dating of GA could contribute to the lower sensitivity. And discrepancies in constitutions of the infants screened at the NICU at the Hospital Civil de Guadalajara during borth study periods compared to from whom WINROP was developed and validated (Sweden and North America).
The first WINROP study drew attention to the high frequency of ROP at the NICU at the Hospital Civil de Guadalajara, Mexico in 2005˗2010. Improved control of oxygen supplementation in 2011 lead to a significant reduction in ROP rates in the present study in 2012-2014. We can only speculate what impact this dramatic reduction in ROP treatment frequency might have for the individual infants and from a socioeconomic viewpoint. Using WINROP in different populations of preterm infants predicts ROP and also alert clinicians to outcome differences in study populations, which may initiate improvements in neonatal care.
Figure 1: Percentage of infants developing ROP type 1, requiring treatment, during the previous (2005-2010) and the present (2012-2014) study period.
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