Poor Outcome at Discharge Among Extremely Premature Infants; a National Population Based Study
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Poor Outcome at Discharge among Extremely Premature Infants; A National Population Based Study. Arch Pediatr Adolesc Med. 2012;166(6):543-50. Amir Kugelman,1 David Bader,1 Liat Lerner-Geva,2, 3 Valentina Boyko,2 Orna Levitzki,2 Arieh Riskin,1 and Brian Reichman2, 3 in Collab oration with th e Israel Neonatal Network 1Department o f Neo na to logy, BnaiZiooda,n Medical Center, The B& R Rappaport Faculty of Medicine, Technion – Haifa, Israel 2Women and Children's Health Research Unit, Gertner Institute, Tel Hashome 3Sackler School of Medicine, Tel Aviv University, Israel ItIntro duc tion The outcome of extremely preterm infants at the time of discharge from NICUs has been determined by several studies. (Costeloe Pediatrics. 2000; Chan Am J Obstet Gynecol. 2001; Vanhaesebrouck Pediatrics. 2004; Markestad Pediatrics. 2005; EXPRESS Group JAMA. 2009; Stoll BJ Pediatrics. 2010). Common to all: - The use of infants‘ GA as the basis for reporting the outcomes. GA alone however, does not appear to be an adequate predictor of outcome …(Tyson NEJM. 2008; Lee PditiPediatrics. 2010). Mortality in ELBW Infants (Bader & Kugelman, et al. Pediatrics. 2010, 125:696–703) ItIntro duc tion Our ability to predict long-term outcome is however limited at birth and duringgy the first days (Ambalavanan J Pediatr. 2006) ELBW infants are at ongoing risk for medical morbidities that may greatly influence their prognosis. Unimpaired survival of ELBW infants at 18-22 months was found to be strongly associated with the absence of major neonatal morbidities and interventions (Ambalavanan J Pediatr. 2006; Doyle Pediatrics. 2001; Schmidt JAMA. 2003; Bassler D Pediatrics. 2009; Gargus Pediatrics. 2009.) Stud y Aim To assess risk factors To develop a simple estimate for poor neonatal outcome including -Death - Severe neonatal morbidity - At the time o f disc harge for spec ific groups of extremely premature infants. Patients and Methods Participants This study is based on analysis of data collected by the Israel Neonatal Network on VLBW infants (<1500 g) born in Israel from January 1995 to December 2008. All 28 neonatal departments in Israel are included in data collection, which comprises the Israel national VLBW infant database. Included were all live births of infants born at 23 to 26 weeks completed weeks of gestation. Data were prospectively collected on a pre-structured form. DfiitiDefinitions Severe neurological morbidity: - Periventricular-intraventricular hemorrhagg(e (P-IVH))g grade 4, - Post hemorrhagic hydrocephalus (PHH), - Periventricular leukomalacia (PVL) - Retinopathy of prematurity (ROP) grade 4. Severe pulmonary morbidity: - Oxygen supplementation at 40 weeks post menstrual age (PMA) - Home oxygen therapy. BPD Bronchopulmonary dysplasia (BPD) is a chronic pulmonary condition that usually evolves after premature birth and respiratory distress syndrome (RDS). Jobe and Bancalari (Am J Respir Crit Care Med 2001) have defined BPD byyy its severity in infants <32 weeks ggg()estational age (GA): – Mild - supplemental oxygen for 28 days and room air at 36 weeks corrected GA or at discharge; – Moderate - supplemental oxygen for 28 days and FiO2 <0.30 at 36 weeks corrected GA or at discharge; – Severe - supplemental oxygen for 28 days and FiO2 ≥0.30 or positive pressure support at 36 weeks corrected GA or at discharge. BPD Because of varied use of supplemental oxygen and saturation targeting in preterm infants, Walsh et al. (J Perinatol 2003) suggested the term “physiological BPD”, based on a timed room-air challenge at 36±1 weeks’ postmenstrual age (PMA) in an attempt to compare incidence of BPD among different centers. Physiological BPD – Preterm infants receiving mechanical ventilation or requiring >30% oxygen to maintain oxygen saturation between 90 and 96% were considered to have “physiological BPD”. – Infants receiving ≤30% oxygen or >30% oxygen with >96% oxygen saturation were given room-air challenges for 30 minutes. Infants in whom oxygen saturation decreased to <90% were cons sdeedidered t o h av e “ ph ysoogcaysiological BPD”. BPD The actual definition of BPD remains problematic and differences in practice and methods for assessing the need for supplemental oxygen are not standardized between NICUs and among physicians. We chose for poor outcome severe forms: – Oxygen supplementation at 40 weeks post menstrual age (PMA) – Home oxygen therapy . RltResults During the period 1995-2008, 20,970 VLBW ( ≤1500 g) infants were recorded in the Israel VLBW infant database, - Accounting for >99% of all live born VLBW infants in Israel. The study population comprised all 4,408 infants of GA 23-26 weeks. Table 1: Clinical Characteristics of Infants (N=4408) Born During the Period 1995 to 2008 According to Gestational Age Gestational age 23 weeks 24 weeks 25 weeks 26 weeks (N=640) (N=1009) (N=1203) (N=1556) Gender, n (%) Males 367 (57) 561(56) 668 (56) 848 (54) Females 273 (43) 448 (44) 535 (44) 708 (46) Birth weight (g) ,median All infants 570 650 734 850 Males 584 669 750 875 Females 560 625 710 820 P * 0.0007 <0.0001 <0.0001 <0.0001 Birth weight z- score, median All infants -0.077 -0.232 -0.303 -0.202 Males -0.123 -0.224 -0.340 -0.191 Females -0.042 -0.256 -0.289 -0.215 p * 0.06 0.90 0.94 0.71 Prenatal steroid , n (%) 156 (25) 506 (51) 729 (61) 1021 (66) C.S., n (%) 108 (17) 375 (37) 651 (54) 1013 (65) Multiple births, n (%) 283 (44) 412 (41) 409 (34) 542 (35) D.R.Resusc., n (%) 388 (61) 839 (83) 1028 (85) 1258 (81) Comfort care, n (%) 226 (35) 68 (7) 20 (2) 7 (0.4) ___________________________________________________________________________________ * p values reflects comparisons between male and female infants for each gestational week. Table 2: Mortalityyy and Severe Morbidity Rates in Survivors According to Gestational Age Gestational age 23 weeks 24 weeks 25 weeks 26 weeks p value N=640 N=1009 N=1203 N=1556 for trend n(%)n (%) n(%)n (%) n(%)n (%) n(%)n (%) Mortality Died 600 (93.8) 742 (73.5) 633 (52.6) 466 (29.9) <0.0001 Survived 40 (6.2) 267 (26.5) 570 (47.4) 1090 (70.1) <0.0001 Severe morbidity in survivors Neurological morbidity Peri-IVH grade 4 4 (10.0) 23 (8.7) 40 (7.2) 74 (7.0) 0.28 Post hemorrhagic hydrocephlus 6 (15.0) 22 (8.3) 46 (8.1) 104 (9.5) 0.80 PVL 4 (10.5) 38 (14.7) 59 (10.6) 113 (10.9) 0.25 ROP grade 4 2 (5.1) 18 (6.8) 8 (1.4) 11 (1.0) <0.0001 Any severe neurological morbidity 12 (30.0) 67 (25.1) 112 (19.6) 206 (18.9) 0.01 Respiratory morbidity O2 at 40 weeks 18 (45.0) 63 (23.6) 104 (18.2) 114 (10.5) 0.0001 O2 at discharge 13 (32.5) 71 (26.6) 92 (16.1) 101 (9.3) <0.0001 Any severe respiratory morbidity 21 (52.5) 87 (32.6) 135 (23.7) 144 (13.2) <0.0001 Severe neurological and/or respiratory morbidity 25 (62.5) 120 (44.9) 221(38.8) 314(28.8) <0.0001 Mortality or severe morbidity 625 (97.7) 862 (85.4) 854 (71.0) 780 (50.1) <0.0001 ____________________________________________________________________________________________ RltResults Since the outcome was poor for almost all infants at 23 weeks GA - Only 15 infants or 2.3% were discharged alive without severe morbidity, - Further analysis included only infants of 24, 25 and 26 weeks gestation. Factors Associated with Poor Neonatal Outcome Stepwise logistic regression analyses identified factors significantly associated with poor neonatal outcome for each of the three gestational week groups. Female infants were significantly lighter than males in each gestational week (Table 1), and therefore analysis was undertaken including gender-specific birth weight z- scores instead of BW. Observed Poor Neonatal Outcome Rates Poor neonatal outcome rates improved siifitl(ignificantly (p<0.0001)f) for inf an ts o f 24-26 weeks gestation in the years 2000-2008 (64.1%) compared t o 1995-1999 (70.7%). Thus, further analyses for more recent data was performed on data from the 2544 infants born in the years 2000-2008. Observed Poor Neonatal Outcome Rates Combined poor outcome of death or severe morbidity by GA. Observed Poor Neonatal Outcome Rates Combined poor outcome of death or severe morbidity for by gender. Observed Poor Neonatal Outcome Rates Combined poor outcome of death or severe morbidity by birth weight percentile group . Observed Poor Neonatal Outcome Rates Combined poor outcome of death or severe morbidity by prenatal steroid therapy. Estimation of Poor Neonatal Outcome On the basis of these analyses, we developed a model for estimatinggp the rates of poor neonatal outcome using data for the period 2000-2008 (n=2544). The model was based on four predictors of poor outcome: – Gestational(l age (24, 25, 26 week)ks) – Gender-specific birth weight percentile group (<25th, 25th-75th, >75th) – Plidh(Prenatal steroid therapy (any or none) – Gender Table 4: Multivariate Linear Regression Analysis of Rates of Combined Poor Outcome of Mortality or Severe Morbidity at Discharge Home of Infants Born at 24 to 26 Weeks Gestation During the Period of 2000-2008 (N=2544) _____________________________________________________________ Predictor Parameter p value Rounded Estimate (95% CI)* Estimate(%) _______________________________________________________________________ Decrease per 1 weekik in GA* 16.6 (13.2-19.9) <0.0001 17 Decrease per 1 level in BW* Quartile 13.0 (9.6-16.4) <0.0001 13 No prenatal steroid therapy 16.4 (10.9-21.9) <0.0001 16 Male 6.7 (1.2-12.2) 0.02 7 Intercept 24.6 (17.8-31.3) <0.0001 25 _______________________________________________________________________ * CI – confidence interval, BW – birth weight, GA – gestational age Estimation of Poor Neonatal Outcome Estimated poor outcome was calculated as the sum of the percent determined for each of the four parameters.