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Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis
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Pediatrics and Neonatology (2017) xx, 1e8
Available online at www.sciencedirect.com
ScienceDirect journal homepage: http://www.pediatr-neonatol.com
Original Article
Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis Ju Sun Heo a,b, Ee-Kyung Kim a,*, Young Hun Choi c, Seung Han Shin a, Jin A Sohn a, Jung-Eun Cheon c, Han-Suk Kim a a
Department of Pediatrics, Seoul National University College of Medicine, Seoul, South Korea Department of Pediatrics, CHA Gangnam Medical Center, CHA University School of Medicine, Seoul, South Korea c Department of Radiology, Seoul National University College of Medicine, Seoul, South Korea b
Received Sep 13, 2016; received in revised form Mar 30, 2017; accepted Jul 28, 2017
Available online - - -
Key Words infant; extremely premature; sepsis; white matter
Background: Systemic infection is a major upstream mechanism for white matter abnormality (WMA). Our aim was to evaluate the risk factors for moderate-to-severe WMA in extremely premature infants (gestational age < 28 weeks) with neonatal sepsis. Methods: Extremely premature infants with culture-proven sepsis between 2006 and 2015 in a tertiary neonatal intensive care unit were classified as having none-to-mild or moderate-tosevere WMA based on WM scores of brain magnetic resonance imaging at the termequivalent age. Various risk factors for WMA were analyzed. Results: Sixty-three infants (87.5%) had none-to-mild WMA, and nine infants (12.5%) had moderate-to-severe WMA. Multivariate logistic regression analysis revealed that postmenstrual age (PMA) at sepsis diagnosis (OR: 0.640, 95% CI: 0.435e0.941, p Z 0.023) and PMA at sepsis diagnosis <28 weeks (OR: 9.232, 95% CI: 1.020e83.590, p Z 0.048) were independently associated with moderate-to-severe WMA. PMA at sepsis diagnosis had a significant negative correlation with WM scores (r Z 0.243, p Z 0.039). Conclusion: PMA at sepsis diagnosis might be an important risk factor for moderate-to-severe WMA in extremely premature infants with postnatal sepsis, especially before PMA 28 weeks. Infants who suffer from sepsis before PMA 28 weeks might need additional therapy for neuroprotection. Copyright ª 2017, Taiwan Pediatric Association. Published by Elsevier Taiwan LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).
* Corresponding author. Department of Pediatrics, Seoul National University College of Medicine, Seoul National University Children’s Hospital, 101 Daehak-ro, Jongno-gu, Seoul, 03080, South Korea. Fax: þ82 2 743 3455. E-mail address: [email protected] (E.K. Kim). http://dx.doi.org/10.1016/j.pedneo.2017.07.008 1875-9572/Copyright ª 2017, Taiwan Pediatric Association. Published by Elsevier Taiwan LLC. This is an open access article under the CC BYNC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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1. Introduction Although the survival of premature newborns has improved over past decades, it has been accompanied by an increase in the number of infants affected by long-term neurodevelopmental morbidities.1e3 The neuropathologies underlying these morbidities are diverse, although the primary type of lesion appears to be white matter abnormality (WMA),4 which is characterized by deep focal areas of cystic necrosis and more diffuse cell-specific WM injury.5e7 Importantly, the severity of WMA is strongly correlated with the degree of neurodevelopmental impairment.8 One of the major upstream mechanisms of WMA is systemic infection/inflammation,5,7,9 and the majority of preterm infants develop at least one neonatal infection during their hospital stay.10 In particular, early- or lateonset sepsis, meningitis and necrotizing enterocolitis (NEC) cause overwhelming systemic inflammation, often resulting in brain injury.11 Multiple clinical studies have demonstrated an association between WMA and postnatal sepsis.12e17 Few reports, however, have described the risk factors for WMA in the context of neonatal sepsis. In this study, we analyzed data from extremely premature infants diagnosed with neonatal sepsis who underwent brain magnetic resonance imaging (MRI) prior to discharge to identify clinical risk factors for moderate-to-severe WMA in septic neonates. Identifying the cause of WMA in infants with sepsis will be important for predicting neurodevelopmental outcomes and may lead to more advanced therapies for intervention and prevention.
2. Methods 2.1. Study design and population The study subjects were extremely premature infants born before 28 weeks of gestation who were admitted to the
J.S. Heo et al neonatal intensive care unit of the Seoul National University Children’s Hospital between January 1, 2006 and December 31, 2015. The medical records of all neonates with a positive blood culture who underwent brain MRI before discharge were retrospectively reviewed. A total of 335 infants were born before 28 weeks of gestation during the study period (Fig. 1). One hundred-four infants (31.0%) were diagnosed with postnatal sepsis during their hospital stay, and 74 infants (71.1%) underwent brain MRI before discharge. Among the 30 infants who did not undergo brain MRI, four had intraventricular hemorrhage (IVH) grade 3 (classified by Papile et al.,18) and three had significantly increased echogenicity of WM according to cranial sonography. Among the 74 infants who underwent brain MRI, two were excluded from the study due to the presence of IVH grade 4 not concurrent with sepsis. These two cases had IVH grade 4 before the septic event. In total, the medical records of 72 infants, including clinical investigations and treatment, were reviewed in this study.
2.2. Ethics statement The study protocol was approved by the institutional review board (IRB) of the Seoul National University Hospital (IRB No. 1508-137-697) with a waiver of informed consent. Patient records/information were anonymized and deidentified prior to data analysis.
2.3. Clinical data collection A trained neonatologist collected data from maternal and infant medical charts. The data collected included variables that could be associated with WMA. The diagnosis of neonatal sepsis required the isolation of a microorganism from a blood culture and at least one of the following clinical signs or symptoms: apnea, bradycardia, hypothermia (core temperature of <36.5 C), fever (core
Figure 1 Cohort flow diagram depicting study population selection. IVH, Intraventricular hemorrhage; MRI, Magnetic resonance imaging; WMA, White matter abnormality.
Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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Sepsis and white matter abnormality
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temperature of >38.0 C), hypoglycemia (blood glucose of <40 mg/dL) and hyperglycemia (blood glucose of >140 mg/ dL). Apnea and bradycardia were included as clinical signs of sepsis only when the episodes were newly developed or the frequency and duration of the episodes increased. Sepsis of coagulase-negative Staphylococcus (CONS) was reviewed using the modified specific criteria of the Centers for Disease Control and Prevention defined by Bizzarro et al.19 Clinical chorioamnionitis (CAM) was diagnosed by the presence of maternal fever (>37.8 C) and at least two of the following criteria: maternal tachycardia (>100 beats/min), maternal leukocytosis (white blood cell count > 15,000 cells/mm3), uterine tenderness, fetal tachycardia (>160 beats/min), or foul-smelling amniotic fluid.20 Placental histological examinations were reviewed by a specialized pathologist for a variety of lesions (chorion, decidua, amnion and umbilical cord), including histological inflammation (graded on a scale of 0e4).21 CAM was histologically diagnosed as the presence of grade 2 in the chorion, decidua, or amnion, and histological funisitis was diagnosed as grade 1 in the umbilical cord. Postnatal morbidities included treated patent ductus arteriosus (PDA) (by medication, operation or both), moderate-to-severe bronchopulmonary dysplasia (need for > 21% oxygen or positive pressure at 36 weeks postmenstrual age (PMA) or discharge), IVH grade 2, retinopathy of prematurity stage 3 (classified by the International Committee for the Classification of retinopathy of prematurity22), NEC stage 2 (classified by modified Bell’s staging criteria23), surgical NEC and hypotension (use of inotropics or systemic steroids for low blood pressure). For sepsis-related factors, sepsis was classified as early-onset (4 days of life), late-onset (5e30 days of life), and late, late-onset (>30 days of life).19 Multidrug-resistant bacteria were defined as organisms resistant to three or more antimicrobial classes. Combined meningitis was defined as bacterial growth in the cerebrospinal fluid (CSF) and blood. Recurrent sepsis was defined as more than two episodes of sepsis, including at least one episode occurring before PMA of 28 weeks. The presence of a central vascular catheter was included in the study only when the device was emplaced before the onset of sepsis and was in place at the time of positive blood culture. Surgery as a potential risk factor for sepsis was included only when the procedure occurred seven days before the onset of positive blood culture.19 PMA and postnatal day (PND) at sepsis diagnosis and sepsis onset time were recorded at the first event of sepsis.
undergo MRI using this ventilator device. The brain MRI studies included the following sequences: axial T2weighted turbo spin-echo, axial fluid-attenuated inversion recovery, axial T1-weighted spin-echo, three-dimensional magnetization-prepared rapid acquisition with gradient echo, and axial diffusion-weighted imaging sequences. The detailed parameters for the sequences are presented in a supplementary table (Table S1). When necessary, infants were sedated according to institutional protocols. A pediatric radiologist who was blinded to the clinical condition of the subjects interpreted each MRI study. We used a standardized scoring system consisting of threepoint scales.8,12,24 WMA was graded according to five scales that assessed 1) the nature and extent of WM signal abnormality, 2) the loss in volume of the periventricular WM, 3) the extent of any cystic abnormalities, 4) ventricular dilatation, and 5) thinning of the corpus callosum. Composite WM scores were calculated and used to categorize the infants based on the extent of cerebral abnormality. WMA was categorized as none (score of 5e6), mild (score of 7e9), moderate (score of 10e12), or severe (score of 13e15). The infants were then grouped as either none-tomild or moderate-to-severe WMA.
2.4. MRI studies
3.1. Moderate-to-severe white matter abnormality
In our unit, all infants with a birth weight below 1 kg were recommended to undergo brain MRI scans, regardless of sonographic findings. In cases of a birth weight above 1 kg, brain MRIs were conducted when sonographic findings were abnormal. MRI scans were obtained at term-equivalent age or before discharge. MRI scans were acquired using a 1.5T scanner (Avanto; Siemens Healthcare, Erlangen, Germany) and a specialized high-sensitivity neonatal array coil built into an MR-compatible incubator with a ventilation device (LMT nomag IC; Lammers Medical Technology, Lu ¨beck, Germany). Patients who were intubated could
Among the 72 infants included in this study, 63 (87.5%) had none-to-mild WMA and nine (12.5%) had moderate-tosevere WMA. Table 1 shows the characteristics of infants with moderate-to-severe WMA. There were five infants with IVH grade 2. Two infants had IVH grade 4, and the others had IVH grade 2. Gram-positive organisms were the most common pathogens of sepsis (four methicillin-resistant Staphylococcus aureus [MRSA] and two CONS). Gramnegative organisms (one Enterobacter aerogenes, one imipenem-resistant Acinetobacter baumannii, and one Escherichia coli) and fungi (two Candida glabrata) were
2.5. Statistical analysis The SPSS version 22.0 statistical software package (SPSS, Inc., Chicago, IL, USA) was used for data analysis. ManneWhitney U test was used to compare continuous variables. Fisher’s exact test (two-sided) was used to compare categorical variables. Logistic regression analysis with backward stepwise selection was performed considering collinearity to analyze the predictors of moderate-tosevere WMA. WMA status was the dependent variable, and all the variables with p-value lower than 0.2 in the ManneWhitney U test or Fisher’s exact test entered in the regression model as independent variables. In the regression model, clinical or histological CAM, NEC, bronchopulmonary dysplasia and recurrent sepsis were considered confounders. Variables were entered at an entry level of significance of p < 0.1 and remained in the model at an exit level of p < 0.05. A Pearson correlation analysis was performed to detect the correlation between PMA at sepsis diagnosis and WM scores. Statistical significance was defined as p < 0.05.
3. Results
Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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BPD, Bronchopulmonary dysplasia; BW, Birth weight; CONS, Coagulase-negative Staphylococcus; CSF, Cerebrospinal fluid; F, Female; GA, Gestational age; IRAB, Imipenem-resistant A. baumannii; IVH, Intraventricular hemorrhage; M, Male; med, Medication; MRI, Magnetic resonance imaging; MRSA, Methicillin-resistant S. aureus; NA, Not available; NEC, Necrotizing enterocolitis; op, Operation; PDA, Patent ductus arteriosus; PMA, Postmenstrual age; PND, Postnatal day; ROP, Retinopathy of prematurity; VP, Ventriculo-peritoneal; WMA, White matter abnormality.
Negative Negative E. coli (26þ5 and 3) MRSA (24þ1 and 6) IVH Grade 2 11 (38þ6) 10 (36þ2) GA 26þ3; F; singleton; BW 1020 GA 23þ3; M; twin; BW 550 8 9
NA CONS (24þ3 and 8) 11 (35þ5) GA 23þ4; M; singleton; BW 620 7
IVH Grade 2
11 (38þ5) GA 24þ0; M; twin; BW 730 6
IVH Grade 4 eVP shunt IVH Grade 4 10 (37þ2) 15 (47þ4) GA 25þ6; M; singleton; BW 870 GA 25þ1; M; twin; BW 820
IVH Grade 2
4 5
NA
NEC (op), BPD, PDA (op), ROP (op) BPD, PDA (med þ op), ROP (op) BPD, PDA (op) BPD, ROP (op)
PDA (med) NEC (op), BPD, PDA (op), ROP Negative NA
NA Negative Negative 10 (36þ1) 12 (40þ1) 11 (47þ1) GA 25þ3; F; singleton; BW 620 GA 23þ6; M; twin; BW 730 GA 23þ5; M; twin; BW 650 1 2 3
MRSA (25þ6 and 4) MRSA (27þ5 and 27) C. glabrata (24þ6 and 9), CONS (25þ6 and 16), CONS (29þ4 and 40) E. aerogenosa (29þ4 and 27) MRSA (26þ0 and 7), C. glabrata (26þ5 and 12) IRAB (24þ4 and 5)
CSF test results Scores of WMA in MRI (PMA, weeks) General characteristics (GA, weeks; BW, g) Patient
Other cerebral findings
Characteristics of nine infants with moderate-to-severe white matter abnormality. Table 1
Pathogens of sepsis (PMA and PND at sepsis diagnosis, weeks and days)
BPD, PDA (op), ROP (op) NEC, BPD, PDA (med þ op) BPD, PDA (med), ROP (op)
J.S. Heo et al
Co-morbidities
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also identified as causative organisms. Only five infants underwent spinal tap, and the results were all negative. Patient 5, who had the highest WM score, underwent recurrent septic events due to MRSA and C. glabrata. The IVH that developed during a septic event progressed to grade 4, and the patient subsequently underwent a ventriculo-peritoneal shunt operation. There were no laboratory data on the CSF analysis for this patient.
3.2. Risk factors for moderate-to-severe white matter abnormality The clinical characteristics of the infants by WMA status are listed in Table 2. The mean gestational age (GA) was 25þ3 weeks, and the mean birth weight was 727 g. GA, Apgar score at 1 min, Apgar score at 5 min, PMA at sepsis diagnosis, and PND at sepsis diagnosis showed a tendency of a negative association with moderate-to-severe WMA (p < 0.2), whereas the incidence of male sex, IVH grade 2, PMA at sepsis diagnosis <28 weeks, and days of mechanical ventilation showed a tendency of a positive association with moderate-to-severe WMA (Table 2). The incidence of PMA at sepsis diagnosis <28 weeks was significantly higher in infants with moderate-to-severe WMA (88.9 vs. 46.0%, p Z 0.028 by Fisher’s exact test), and WM scores were significantly higher in infants diagnosed with sepsis before PMA 28 weeks than in infants diagnosed with sepsis after PMA 28 weeks (mean standard deviation, 7.3 2.47 vs. 6.2 1.40, p Z 0.031). For the multivariate logistic regression analysis including independent variables and confounders, PMA at sepsis diagnosis (OR: 0.640, 95% CI: 0.435e0.941, p Z 0.023) and PMA at sepsis diagnosis <28 weeks (OR: 9.232, 95% CI: 1.020e83.590, p Z 0.048), respectively, were retained as independently associated variables with moderate-to-severe WMA (Table 3). The correlation analysis showed that the PMA at sepsis diagnosis had a significant negative correlation with WM scores (r Z 0.243, p Z 0.039) (Fig. 2).
4. Discussion In the present study, PMA at sepsis diagnosis was an important risk factor for moderate-to-severe WMA. In particular, if sepsis occurred before PMA 28 weeks, the risk of moderate-to-severe WMA was potentially higher. In recent studies using MRI to determine the spectrum of WMA in premature newborns, the incidence of focal cystic necrosis with loss of all cellular elements has distinctly decreased, whereas non-cystic WMA has become the most prevalent pattern of brain injury in premature newborns.25 Non-cystic WMA is a cell-specific lesion with acute loss of early differentiating oligodendrocytes, also known as premyelinating oligodendrocytes (pre-OLs).7 Pre-OLs represent a specific phase of the oligodendroglial lineage that is highly susceptible to hypoxia-ischemia and systemic infection/inflammation.26 Pre-OLs are present as early as 18 weeks and comprise approximately 90% of the total oligodendroglial population until approximately 28 weeks gestation.7,9,27 After 28 weeks gestation, expansion of the immature OL population is prominent.27 Therefore, the timing of insults to the developing brain is a critical factor
Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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Sepsis and white matter abnormality Table 2
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Comparison of the characteristics based on severity of white matter abnormality.
Demographics and perinatal factors Gestational age, weeks, mean SD Birth weight, grams, mean SD Male, n (%) C-section delivery, n (%) Clinical or histological chorioamnionitis, n (%) Histological funisitis, n (%) Prenatal medications Glucocorticoids, n (%) Antibiotics, n (%) Apgar score, 1 min, mean SD Apgar score, 5 min, mean SD Cord blood pH, mean SD Cord blood base excess, mmol/L, mean SD Postnatal factors Treated PDA, n (%) Moderate to severe BPD, n (%) Use of systemic steroids for BPD, n (%) IVH Grade 2, n (%) IVH Grade 2 IVH Grade 3 IVH Grade 4 ROP stage 3, n (%) NEC stage 2, n (%) Surgical NEC, n (%) Hypotension during hospitalization, n (%) Mechanical ventilation, days, mean SD Hospital stay, days, mean SD PMA at brain MRI, weeks, mean SD Sepsis-related factors PMA at sepsis diagnosis, weeks, mean SD PMA at sepsis diagnosis <28 weeks, n (%) PND at sepsis diagnosis, days, mean SD Sepsis onset time Early onset sepsis, n (%) Late onset sepsis, n (%) Late, late onset sepsis, n (%) Pathogen Gram positive, n (%) Gram negative, n (%) Fungus, n (%) MDR bacteria, n (%) Combined meningitis, n (%) Recurrent sepsis, n (%) Hypotension during sepsis, n (%) Central vascular catheter, n (%) Surgery, n (%) Duration of positive to negative conversion of blood culture results, hours, mean SD Duration from sepsis onset to use of susceptible antibiotics, hours, mean SD
None-to-mild (n Z 63)
Moderate-to-severe (n Z 9)
p-value
25þ4 1.473 726 151 31 (49.2) 35 (55.6) 34 (54.0) 11 (17.5)
24þ4 1.120 734 147 7 (77.8) 5 (55.6) 5 (55.6) 1 (11.1)
0.043a 0.952a 0.158b >0.99b >0.99b >0.99b
52 (82.5) 36 (58.1) 3.2 1.726 5.6 1.485 7.303 0.089 3.4 3.965
6 (66.7) 4 (44.4) 2.3 1.581 5.0 0.866 7.282 0.118 5.5 5.848
0.363b 0.490b 0.119a 0.099a 0.883a 0.466a
56 (88.9) 48 (76.2) 9 (14.3) 13 (20.6) 12 (19.0) 1 (1.6) 0 (0) 31 (49.2) 17 (27.0) 15 (23.8) 53 (84.1) 48 34.375 114 34.065 38þ5 2.784
8 (88.9) 8 (88.9) 2 (22.2) 5 (55.6) 3 (33.3) 0 (0) 2 (22.2) 6 (66.7) 4 (44.4) 3 (33.3) 7 (77.8) 68 28.403 131 44.011 39þ5 4.545
>0.99b 0.673b 0.619b 0.038b
0.480b 0.433b 0.682b 0.639b 0.114a 0.250a 0.878a
28þ2 3.001 29 (46.0) 19 17.044
25þ6 1.783 8 (88.9) 10 9.488
0.011a 0.028b 0.054a
7 (11.1) 46 (73.0) 10 (15.9)
2 (22.2) 7 (77.8) 0 (0.0)
0.312b >0.99b 0.343b
46 (73.0) 13 (20.6) 13 (20.6) 34 (54.0) 1/42 (2.4) 13 (20.6) 27 (42.9) 54 (85.7) 10 (15.9) 88 51.025
6 (66.7) 3 (33.3) 2 (22.2) 7 (77.8) 0/4 (0.0) 2 (22.2) 3 (33.3) 8 (88.9) 0 (0.0) 72 38.502
0.701b 0.406b >0.99b 0.283b >0.99b >0.99b 0.667b >0.99b 0.343b 0.438a
34 29.803
50 40.453
0.217a
Bold values indicate p-value < 0.2. BPD, Bronchopulmonary dysplasia; IVH, Intraventricular hemorrhage; MDR, Multi-drug resistant; MRI, Magnetic resonance imaging; NEC, Necrotizing enterocolitis; PDA, Patent ductus arteriosus; PMA, Postmenstrual age; PND, Postnatal day; ROP, Retinopathy of prematurity; SD, Standard deviation. a ManneWhitney U test. b Fisher’s exact test.
Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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J.S. Heo et al Table 3
Logistic regression analysis for predicting moderate-to-severe white matter abnormality.
Variable
PMA at sepsis diagnosis, weeks PMA at sepsis diagnosis <28 weeks
Adjusted modela
Unadjusted model OR
95% CI
p-value
OR
95% CI
p-value
0.637 9.379
0.432e0.939 1.107e79.486
0.023 0.040
0.640 9.232
0.435e0.941 1.020e83.590
0.023 0.048
CI, Confidence interval; OR, Odds ratio; PMA, Postmenstrual age. a Dependent variable þ independent variables þ confounders (including clinical or histological chorioamnionitis, necrotizing enterocolitis stage 2, bronchopulmonary dysplasia and recurrent sepsis).
contributing to WMA. Our data demonstrating that PMA at sepsis diagnosis, particularly before 28 weeks, correlates with moderate-to-severe WMA are consistent with these findings. Although many animal studies correspond well with this hypothesis,28e30 there have been few clinical studies analyzing the relationship between the timing of sepsis and the severity of WMA. The present study has considerable value, in that the results suggest a significant effect of the timing of systemic infection on WMA in extremely preterm infants. In the present study, hypotension during sepsis or hospitalization was not correlated with moderate-to-severe WMA. A potentiating interaction between hypoxia-ischemia and systemic infection/inflammation has been demonstrated in previous studies,31,32 although our results contradict those results. We can think of two reasons for this discrepancy. First, hypotension itself is not well defined. Generally, most neonatologists consider hypotension present if the infant’s mean arterial pressure is less than the GA in weeks.33,34 However, by this definition,
hypotension does not always accompany cerebral hypoperfusion. Lightburn et al.35 observed no significant difference in cerebral blood flow velocity between extremely low birth weight infants with hypotension and infants with normal blood pressure. Moreover, in a study by Bonestroo et al.,36 antihypotensive treatment did not induce any significant change in regional cerebral oxygen saturation or fractional tissue oxygen extraction in hypotensive preterm infants without PDA. Therefore, hypoperfusion may not have occurred in the hypotensive infants in the present study, resulting in no hypoxia-ischemia in the brain. Second, the potentiation between systemic infection/inflammation and hypoxia-ischemia depends on the relative timing of the insults.7 In the rat pup model employed by Eklind et al.,37 lipopolysaccharide enhanced vulnerability during both the acute and chronic phases after administration, whereas an intermediate interval between lipopolysaccharide treatment and hypoxia-ischemia resulted in tolerance rather than potentiation. In the present study, we did not consider the timing of the insults between
Figure 2 Scatter plot and linear line showing white matter scores as a function of postmenstrual age at sepsis diagnosis. PMA, Postmenstrual age; WM, White matter.
Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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Sepsis and white matter abnormality systemic infection and hypoxia-ischemia, and the time intervals between these insults were likely heterogeneous. According to the Fisher’s exact test in the present study, IVH combined with sepsis was correlated with moderate-tosevere WMA. When IVH develops, the amount of nonprotein-bound iron in the CSF increases, and this free iron could be used to convert hydrogen peroxide to hydroxyl radical via the Fenton reaction.38 Free radical generation is the most important downstream mechanism of WM injury, as free radical attack appears to be the principal final common pathway to injury.7 In addition, increased methemoglobin formation in the intraventricular space following IVH induces expression of pro-inflammatory cytokines.39 These cytokines potentiate maturationdependent toxicity, affecting pre-OLs.13 Therefore, we conducted IVH grade 2, 3-adjusted analysis, and IVH grade 4 cases were excluded, unless occurring during the septic events, due to significant impacts on WMA scores. In the present study, recurrent postnatal sepsis was not associated with moderate-to-severe WMA. Furthermore, including NEC and prenatal CAM as additional inflammatory events did not affect the results. In recurrent systemic infection, the development of pre-OLs can be inhibited by toxicity or by direct activation of receptors on pre-OLs such as Toll-like receptors or interferon-g,7 and this inhibition of pre-OL development may be associated with progressive WM injury in preterm infants.15 However, in a study by Glass et al.,15 seven of 12 infants with progressive WM injury exhibited progression from none to minimal WM injury, and no progression to moderate or severe injury was observed. In the present study, we compared none-to-mild WMA with moderate-to-severe WMA, as we could not investigate the progression of WMA due to the lack of serial brain MRI studies. The WM scores were higher in infants with recurrent postnatal sepsis than in infants without recurrent sepsis, although this difference was not significant (mean standard deviation, 7.0 2.71 vs. 6.7 1.89, p Z 0.847). There were several limitations to this study. First, the small sample size and relative rarity of moderate-to-severe WMA limited our statistical analyses, which were insufficient to confirm the effects of hypotension and recurrent sepsis on WMA. Despite this limitation, PMA at sepsis diagnosis, especially before 28 weeks, was identified as a risk factor for moderate-to-severe WMA. Second, the data on combined meningitis were imprecise, as many infants did not undergo lumbar puncture based on the decision of the treating physician. This lack of precision could explain why meningitis was not associated with WMA. Third, several infants experienced recurrent septic events. In the statistical analysis, the pathogen, the presence of combined meningitis, hypotension during sepsis, central vascular catheters, surgery, duration of positive to negative conversion of blood culture results, and duration from sepsis onset to use of susceptible antibiotics were determined for each individual episode of sepsis. These factors were different for each episode in patients with recurrent sepsis, and therefore, it is difficult to evaluate the precise risk factors in such cases. Finally, we have no data on long-term neurodevelopmental outcomes relative to the severity of WMA in our study. Further investigations of the associations between WMA and neurodevelopmental outcomes are needed.
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5. Conclusions This study suggests that PMA at sepsis diagnosis might be an important risk factor for moderate-to-severe WMA in extremely premature infants with neonatal sepsis. Infants diagnosed with sepsis before PMA 28 weeks represent a high-risk group for moderate-to-severe WMA. These findings could be considered when determining the target of neuroprotective treatments in premature infants with sepsis.
Funding This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2012R1A1A2044109).
Conflicts of interest None declared.
References 1. Moore T, Hennessy EM, Myles J, Johnson SJ, Draper ES, Costeloe KL, et al. Neurological and developmental outcome in extremely preterm children born in England in 1995 and 2006: the EPICure studies. BMJ 2012;345:e7961. 2. Synnes AR, Anson S, Arkesteijn A, Butt A, Grunau RE, Rogers M, et al. School entry age outcomes for infants with birth weight 800 grams. J Pediatr 2010;157:989e994.e1. 3. Wilson-Costello D, Friedman H, Minich N, Fanaroff AA, Hack M. Improved survival rates with increased neurodevelopmental disability for extremely low birth weight infants in the 1990s. Pediatrics 2005;115:997e1003. 4. Shane AL, Hansen NI, Stoll BJ, Bell EF, Sa ´nchez PJ, Shankaran S, et al. Methicillin-resistant and susceptible Staphylococcus aureus bacteremia and meningitis in preterm infants. Pediatrics 2012;129:e914e22. 5. Volpe JJ. Postnatal sepsis, necrotizing entercolitis, and the critical role of systemic inflammation in white matter injury in premature infants. J Pediatr 2008;153:160e3. 6. Miller SP, Ferriero DM, Leonard C, Piecuch R, Glidden DV, Partridge JC, et al. Early brain injury in premature newborns detected with magnetic resonance imaging is associated with adverse early neurodevelopmental outcome. J Pediatr 2005; 147:609e16. 7. Volpe JJ, Kinney HC, Jensen FE, Rosenberg PA. The developing oligodendrocyte: key cellular target in brain injury in the premature infant. Int J Dev Neurosci 2011;29:423e40. 8. Woodward LJ, Anderson PJ, Austin NC, Howard K, Inder TE. Neonatal MRI to predict neurodevelopmental outcomes in preterm infants. N Engl J Med 2006;355:685e94. 9. Back SA. Cerebral white and gray matter injury in newborns: new insights into pathophysiology and management. Clin Perinatol 2014;41:1e24. 10. Stoll BJ, Hansen NI, Adams-Chapman I, Fanaroff AA, Hintz SR, Vohr B, et al. Neurodevelopmental and growth impairment among extremely low-birth-weight infants with neonatal infection. JAMA 2004;292:2357e65. 11. American College of Obstetricians and Gynecologists. ACOG practice bulletin: clinical management guidelines for obstetrician-gynecologists: number 38, September 2002. Perinatal care at the threshold of viability. Obstet Gynecol 2002; 100:617e24.
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8 12. Inder TE, Wells SJ, Mogridge NB, Spencer C, Volpe JJ. Defining the nature of the cerebral abnormalities in the premature infant: a qualitative magnetic resonance imaging study. J Pediatr 2003;143:171e9. 13. Graham EM, Holcroft CJ, Rai KK, Donohue PK, Allen MC. Neonatal cerebral white matter injury in preterm infants is associated with culture positive infections and only rarely with metabolic acidosis. Am J Obstet Gynecol 2004;191:1305e10. 14. Shah DK, Doyle LW, Anderson PJ, Bear M, Daley AJ, Hunt RW, et al. Adverse neurodevelopment in preterm infants with postnatal sepsis or necrotizing enterocolitis is mediated by white matter abnormalities on magnetic resonance imaging at term. J Pediatr 2008;153:170e5. 175.e1. 15. Glass HC, Bonifacio SL, Chau V, Glidden D, Poskitt K, Barkovich AJ, et al. Recurrent postnatal infections are associated with progressive white matter injury in premature infants. Pediatrics 2008;122:299e305. 16. Hofer N, Mu ¨ller W, Resch B. White matter damage and neonatal sepsis. Acta Paediatr 2011;100:e1; author reply e1e2. 17. Chau V, Brant R, Poskitt KJ, Tam EW, Synnes A, Miller SP. Postnatal infection is associated with widespread abnormalities of brain development in premature newborns. Pediatr Res 2012;71:274e9. 18. Papile LA, Burstein J, Burstein R, Koffler H. Incidence and evolution of subependymal and intraventricular hemorrhage: a study of infants with birth weights less than 1,500 gm. J Pediatr 1978;92:529e34. 19. Bizzarro MJ, Raskind C, Baltimore RS, Gallagher PG. Seventyfive years of neonatal sepsis at Yale: 1928e2003. Pediatrics 2005;116:595e602. 20. Tita AT, Andrews WW. Diagnosis and management of clinical chorioamnionitis. Clin Perinatol 2010;37:339e54. 21. Salafia CM, Minior VK, Rosenkrantz TS, Pezzullo JC, Popek EJ, Cusick W, et al. Maternal, placental, and neonatal associations with early germinal matrix/intraventricular hemorrhage in infants born before 32 weeks’ gestation. Am J Perinatol 1995;12: 429e36. 22. International Committee for the Classification of Retinopathy of Prematurity. The International classification of retinopathy of prematurity revisited. Arch Ophthalmol 2005;123:991e9. 23. Walsh MC, Kliegman RM. Necrotizing enterocolitis: treatment based on staging criteria. Pediatr Clin North Am 1986;33: 179e201. 24. Woodward LJ, Mogridge N, Wells SW, Inder TE. Can neurobehavioral examination predict the presence of cerebral injury in the very low birth weight infant? J Dev Behav Pediatr 2004; 25:326e34. 25. Chau V, Poskitt KJ, McFadden DE, Bowen-Roberts T, Synnes A, Brant R, et al. Effect of chorioamnionitis on brain development and injury in premature newborns. Ann Neurol 2009;66: 155e64. 26. Favrais G, van de Looij Y, Fleiss B, Ramanantsoa N, Bonnin P, Stoltenburg-Didinger G, et al. Systemic inflammation disrupts
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the developmental program of white matter. Ann Neurol 2011; 70:550e65. Back SA, Luo NL, Borenstein NS, Levine JM, Volpe JJ, Kinney HC. Late oligodendrocyte progenitors coincide with the developmental window of vulnerability for human perinatal white matter injury. J Neurosci 2001;21:1302e12. Reddy K, Mallard C, Guan J, Marks K, Bennet L, Gunning M, et al. Maturational change in the cortical response to hypoperfusion injury in the fetal sheep. Pediatr Res 1998;43:674e82. Hagberg H, Peebles D, Mallard C. Models of white matter injury: comparison of infectious, hypoxic-ischemic, and excitotoxic insults. Ment Retard Dev Disabil Res Rev 2002;8:30e8. Buser JR, Segovia KN, Dean JM, Nelson K, Beardsley D, Gong X, et al. Timing of appearance of late oligodendrocyte progenitors coincides with enhanced susceptibility of preterm rabbit cerebral white matter to hypoxia-ischemia. J Cereb Blood Flow Metab 2010;30:1053e65. Wang X, Stridh L, Li W, Dean J, Elmgren A, Gan L, et al. Lipopolysaccharide sensitizes neonatal hypoxic-ischemic brain injury in a MyD88-dependent manner. J Immunol 2009;183: 7471e7. Wang LW, Chang YC, Lin CY, Hong JS, Huang CC. Low-dose lipopolysaccharide selectively sensitizes hypoxic ischemiainduced white matter injury in the immature brain. Pediatr Res 2010;68:41e7. Seri I. Cardiovascular, renal, and endocrine actions of dopamine in neonates and children. J Pediatr 1995;126:333e44. Roze ´ JC, Tohier C, Maingueneau C, Lefe `vre M, Mouzard A. Response to dobutamine and dopamine in the hypotensive very preterm infant. Arch Dis Child 1993;69:59e63. Lightburn MH, Gauss CH, Williams DK, Kaiser JR. Cerebral blood flow velocities in extremely low birth weight infants with hypotension and infants with normal blood pressure. J Pediatr 2009;154:824e8. Bonestroo HJ, Lemmers PM, Baerts W, van Bel F. Effect of antihypotensive treatment on cerebral oxygenation of preterm infants without PDA. Pediatrics 2011;128:e1502e10. Eklind S, Mallard C, Arvidsson P, Hagberg H. Lipopolysaccharide induces both a primary and a secondary phase of sensitization in the developing rat brain. Pediatr Res 2005;58:112e6. Iida K, Takashima S, Ueda K. Immunohistochemical study of myelination and oligodendrocyte in infants with periventricular leukomalacia. Pediatr Neurol 1995;13:296e304. Gram M, Sveinsdottir S, Ruscher K, Hansson SR, Cinthio M, Akerstro ¨m B, et al. Hemoglobin induces inflammation after preterm intraventricular hemorrhage by methemoglobin formation. J Neuroinflamm 2013;10:100.
Appendix A. Supplementary data Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.pedneo.2017.07.008.
Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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Pediatrics and Neonatology (2017) xx, 1e8
Available online at www.sciencedirect.com
ScienceDirect journal homepage: http://www.pediatr-neonatol.com
Original Article
Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis Ju Sun Heo a,b, Ee-Kyung Kim a,*, Young Hun Choi c, Seung Han Shin a, Jin A Sohn a, Jung-Eun Cheon c, Han-Suk Kim a a
Department of Pediatrics, Seoul National University College of Medicine, Seoul, South Korea Department of Pediatrics, CHA Gangnam Medical Center, CHA University School of Medicine, Seoul, South Korea c Department of Radiology, Seoul National University College of Medicine, Seoul, South Korea b
Received Sep 13, 2016; received in revised form Mar 30, 2017; accepted Jul 28, 2017
Available online - - -
Key Words infant; extremely premature; sepsis; white matter
Background: Systemic infection is a major upstream mechanism for white matter abnormality (WMA). Our aim was to evaluate the risk factors for moderate-to-severe WMA in extremely premature infants (gestational age < 28 weeks) with neonatal sepsis. Methods: Extremely premature infants with culture-proven sepsis between 2006 and 2015 in a tertiary neonatal intensive care unit were classified as having none-to-mild or moderate-tosevere WMA based on WM scores of brain magnetic resonance imaging at the termequivalent age. Various risk factors for WMA were analyzed. Results: Sixty-three infants (87.5%) had none-to-mild WMA, and nine infants (12.5%) had moderate-to-severe WMA. Multivariate logistic regression analysis revealed that postmenstrual age (PMA) at sepsis diagnosis (OR: 0.640, 95% CI: 0.435e0.941, p Z 0.023) and PMA at sepsis diagnosis <28 weeks (OR: 9.232, 95% CI: 1.020e83.590, p Z 0.048) were independently associated with moderate-to-severe WMA. PMA at sepsis diagnosis had a significant negative correlation with WM scores (r Z 0.243, p Z 0.039). Conclusion: PMA at sepsis diagnosis might be an important risk factor for moderate-to-severe WMA in extremely premature infants with postnatal sepsis, especially before PMA 28 weeks. Infants who suffer from sepsis before PMA 28 weeks might need additional therapy for neuroprotection. Copyright ª 2017, Taiwan Pediatric Association. Published by Elsevier Taiwan LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).
* Corresponding author. Department of Pediatrics, Seoul National University College of Medicine, Seoul National University Children’s Hospital, 101 Daehak-ro, Jongno-gu, Seoul, 03080, South Korea. Fax: þ82 2 743 3455. E-mail address: [email protected] (E.K. Kim). http://dx.doi.org/10.1016/j.pedneo.2017.07.008 1875-9572/Copyright ª 2017, Taiwan Pediatric Association. Published by Elsevier Taiwan LLC. This is an open access article under the CC BYNC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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1. Introduction Although the survival of premature newborns has improved over past decades, it has been accompanied by an increase in the number of infants affected by long-term neurodevelopmental morbidities.1e3 The neuropathologies underlying these morbidities are diverse, although the primary type of lesion appears to be white matter abnormality (WMA),4 which is characterized by deep focal areas of cystic necrosis and more diffuse cell-specific WM injury.5e7 Importantly, the severity of WMA is strongly correlated with the degree of neurodevelopmental impairment.8 One of the major upstream mechanisms of WMA is systemic infection/inflammation,5,7,9 and the majority of preterm infants develop at least one neonatal infection during their hospital stay.10 In particular, early- or lateonset sepsis, meningitis and necrotizing enterocolitis (NEC) cause overwhelming systemic inflammation, often resulting in brain injury.11 Multiple clinical studies have demonstrated an association between WMA and postnatal sepsis.12e17 Few reports, however, have described the risk factors for WMA in the context of neonatal sepsis. In this study, we analyzed data from extremely premature infants diagnosed with neonatal sepsis who underwent brain magnetic resonance imaging (MRI) prior to discharge to identify clinical risk factors for moderate-to-severe WMA in septic neonates. Identifying the cause of WMA in infants with sepsis will be important for predicting neurodevelopmental outcomes and may lead to more advanced therapies for intervention and prevention.
2. Methods 2.1. Study design and population The study subjects were extremely premature infants born before 28 weeks of gestation who were admitted to the
J.S. Heo et al neonatal intensive care unit of the Seoul National University Children’s Hospital between January 1, 2006 and December 31, 2015. The medical records of all neonates with a positive blood culture who underwent brain MRI before discharge were retrospectively reviewed. A total of 335 infants were born before 28 weeks of gestation during the study period (Fig. 1). One hundred-four infants (31.0%) were diagnosed with postnatal sepsis during their hospital stay, and 74 infants (71.1%) underwent brain MRI before discharge. Among the 30 infants who did not undergo brain MRI, four had intraventricular hemorrhage (IVH) grade 3 (classified by Papile et al.,18) and three had significantly increased echogenicity of WM according to cranial sonography. Among the 74 infants who underwent brain MRI, two were excluded from the study due to the presence of IVH grade 4 not concurrent with sepsis. These two cases had IVH grade 4 before the septic event. In total, the medical records of 72 infants, including clinical investigations and treatment, were reviewed in this study.
2.2. Ethics statement The study protocol was approved by the institutional review board (IRB) of the Seoul National University Hospital (IRB No. 1508-137-697) with a waiver of informed consent. Patient records/information were anonymized and deidentified prior to data analysis.
2.3. Clinical data collection A trained neonatologist collected data from maternal and infant medical charts. The data collected included variables that could be associated with WMA. The diagnosis of neonatal sepsis required the isolation of a microorganism from a blood culture and at least one of the following clinical signs or symptoms: apnea, bradycardia, hypothermia (core temperature of <36.5 C), fever (core
Figure 1 Cohort flow diagram depicting study population selection. IVH, Intraventricular hemorrhage; MRI, Magnetic resonance imaging; WMA, White matter abnormality.
Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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Sepsis and white matter abnormality
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temperature of >38.0 C), hypoglycemia (blood glucose of <40 mg/dL) and hyperglycemia (blood glucose of >140 mg/ dL). Apnea and bradycardia were included as clinical signs of sepsis only when the episodes were newly developed or the frequency and duration of the episodes increased. Sepsis of coagulase-negative Staphylococcus (CONS) was reviewed using the modified specific criteria of the Centers for Disease Control and Prevention defined by Bizzarro et al.19 Clinical chorioamnionitis (CAM) was diagnosed by the presence of maternal fever (>37.8 C) and at least two of the following criteria: maternal tachycardia (>100 beats/min), maternal leukocytosis (white blood cell count > 15,000 cells/mm3), uterine tenderness, fetal tachycardia (>160 beats/min), or foul-smelling amniotic fluid.20 Placental histological examinations were reviewed by a specialized pathologist for a variety of lesions (chorion, decidua, amnion and umbilical cord), including histological inflammation (graded on a scale of 0e4).21 CAM was histologically diagnosed as the presence of grade 2 in the chorion, decidua, or amnion, and histological funisitis was diagnosed as grade 1 in the umbilical cord. Postnatal morbidities included treated patent ductus arteriosus (PDA) (by medication, operation or both), moderate-to-severe bronchopulmonary dysplasia (need for > 21% oxygen or positive pressure at 36 weeks postmenstrual age (PMA) or discharge), IVH grade 2, retinopathy of prematurity stage 3 (classified by the International Committee for the Classification of retinopathy of prematurity22), NEC stage 2 (classified by modified Bell’s staging criteria23), surgical NEC and hypotension (use of inotropics or systemic steroids for low blood pressure). For sepsis-related factors, sepsis was classified as early-onset (4 days of life), late-onset (5e30 days of life), and late, late-onset (>30 days of life).19 Multidrug-resistant bacteria were defined as organisms resistant to three or more antimicrobial classes. Combined meningitis was defined as bacterial growth in the cerebrospinal fluid (CSF) and blood. Recurrent sepsis was defined as more than two episodes of sepsis, including at least one episode occurring before PMA of 28 weeks. The presence of a central vascular catheter was included in the study only when the device was emplaced before the onset of sepsis and was in place at the time of positive blood culture. Surgery as a potential risk factor for sepsis was included only when the procedure occurred seven days before the onset of positive blood culture.19 PMA and postnatal day (PND) at sepsis diagnosis and sepsis onset time were recorded at the first event of sepsis.
undergo MRI using this ventilator device. The brain MRI studies included the following sequences: axial T2weighted turbo spin-echo, axial fluid-attenuated inversion recovery, axial T1-weighted spin-echo, three-dimensional magnetization-prepared rapid acquisition with gradient echo, and axial diffusion-weighted imaging sequences. The detailed parameters for the sequences are presented in a supplementary table (Table S1). When necessary, infants were sedated according to institutional protocols. A pediatric radiologist who was blinded to the clinical condition of the subjects interpreted each MRI study. We used a standardized scoring system consisting of threepoint scales.8,12,24 WMA was graded according to five scales that assessed 1) the nature and extent of WM signal abnormality, 2) the loss in volume of the periventricular WM, 3) the extent of any cystic abnormalities, 4) ventricular dilatation, and 5) thinning of the corpus callosum. Composite WM scores were calculated and used to categorize the infants based on the extent of cerebral abnormality. WMA was categorized as none (score of 5e6), mild (score of 7e9), moderate (score of 10e12), or severe (score of 13e15). The infants were then grouped as either none-tomild or moderate-to-severe WMA.
2.4. MRI studies
3.1. Moderate-to-severe white matter abnormality
In our unit, all infants with a birth weight below 1 kg were recommended to undergo brain MRI scans, regardless of sonographic findings. In cases of a birth weight above 1 kg, brain MRIs were conducted when sonographic findings were abnormal. MRI scans were obtained at term-equivalent age or before discharge. MRI scans were acquired using a 1.5T scanner (Avanto; Siemens Healthcare, Erlangen, Germany) and a specialized high-sensitivity neonatal array coil built into an MR-compatible incubator with a ventilation device (LMT nomag IC; Lammers Medical Technology, Lu ¨beck, Germany). Patients who were intubated could
Among the 72 infants included in this study, 63 (87.5%) had none-to-mild WMA and nine (12.5%) had moderate-tosevere WMA. Table 1 shows the characteristics of infants with moderate-to-severe WMA. There were five infants with IVH grade 2. Two infants had IVH grade 4, and the others had IVH grade 2. Gram-positive organisms were the most common pathogens of sepsis (four methicillin-resistant Staphylococcus aureus [MRSA] and two CONS). Gramnegative organisms (one Enterobacter aerogenes, one imipenem-resistant Acinetobacter baumannii, and one Escherichia coli) and fungi (two Candida glabrata) were
2.5. Statistical analysis The SPSS version 22.0 statistical software package (SPSS, Inc., Chicago, IL, USA) was used for data analysis. ManneWhitney U test was used to compare continuous variables. Fisher’s exact test (two-sided) was used to compare categorical variables. Logistic regression analysis with backward stepwise selection was performed considering collinearity to analyze the predictors of moderate-tosevere WMA. WMA status was the dependent variable, and all the variables with p-value lower than 0.2 in the ManneWhitney U test or Fisher’s exact test entered in the regression model as independent variables. In the regression model, clinical or histological CAM, NEC, bronchopulmonary dysplasia and recurrent sepsis were considered confounders. Variables were entered at an entry level of significance of p < 0.1 and remained in the model at an exit level of p < 0.05. A Pearson correlation analysis was performed to detect the correlation between PMA at sepsis diagnosis and WM scores. Statistical significance was defined as p < 0.05.
3. Results
Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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BPD, Bronchopulmonary dysplasia; BW, Birth weight; CONS, Coagulase-negative Staphylococcus; CSF, Cerebrospinal fluid; F, Female; GA, Gestational age; IRAB, Imipenem-resistant A. baumannii; IVH, Intraventricular hemorrhage; M, Male; med, Medication; MRI, Magnetic resonance imaging; MRSA, Methicillin-resistant S. aureus; NA, Not available; NEC, Necrotizing enterocolitis; op, Operation; PDA, Patent ductus arteriosus; PMA, Postmenstrual age; PND, Postnatal day; ROP, Retinopathy of prematurity; VP, Ventriculo-peritoneal; WMA, White matter abnormality.
Negative Negative E. coli (26þ5 and 3) MRSA (24þ1 and 6) IVH Grade 2 11 (38þ6) 10 (36þ2) GA 26þ3; F; singleton; BW 1020 GA 23þ3; M; twin; BW 550 8 9
NA CONS (24þ3 and 8) 11 (35þ5) GA 23þ4; M; singleton; BW 620 7
IVH Grade 2
11 (38þ5) GA 24þ0; M; twin; BW 730 6
IVH Grade 4 eVP shunt IVH Grade 4 10 (37þ2) 15 (47þ4) GA 25þ6; M; singleton; BW 870 GA 25þ1; M; twin; BW 820
IVH Grade 2
4 5
NA
NEC (op), BPD, PDA (op), ROP (op) BPD, PDA (med þ op), ROP (op) BPD, PDA (op) BPD, ROP (op)
PDA (med) NEC (op), BPD, PDA (op), ROP Negative NA
NA Negative Negative 10 (36þ1) 12 (40þ1) 11 (47þ1) GA 25þ3; F; singleton; BW 620 GA 23þ6; M; twin; BW 730 GA 23þ5; M; twin; BW 650 1 2 3
MRSA (25þ6 and 4) MRSA (27þ5 and 27) C. glabrata (24þ6 and 9), CONS (25þ6 and 16), CONS (29þ4 and 40) E. aerogenosa (29þ4 and 27) MRSA (26þ0 and 7), C. glabrata (26þ5 and 12) IRAB (24þ4 and 5)
CSF test results Scores of WMA in MRI (PMA, weeks) General characteristics (GA, weeks; BW, g) Patient
Other cerebral findings
Characteristics of nine infants with moderate-to-severe white matter abnormality. Table 1
Pathogens of sepsis (PMA and PND at sepsis diagnosis, weeks and days)
BPD, PDA (op), ROP (op) NEC, BPD, PDA (med þ op) BPD, PDA (med), ROP (op)
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Co-morbidities
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also identified as causative organisms. Only five infants underwent spinal tap, and the results were all negative. Patient 5, who had the highest WM score, underwent recurrent septic events due to MRSA and C. glabrata. The IVH that developed during a septic event progressed to grade 4, and the patient subsequently underwent a ventriculo-peritoneal shunt operation. There were no laboratory data on the CSF analysis for this patient.
3.2. Risk factors for moderate-to-severe white matter abnormality The clinical characteristics of the infants by WMA status are listed in Table 2. The mean gestational age (GA) was 25þ3 weeks, and the mean birth weight was 727 g. GA, Apgar score at 1 min, Apgar score at 5 min, PMA at sepsis diagnosis, and PND at sepsis diagnosis showed a tendency of a negative association with moderate-to-severe WMA (p < 0.2), whereas the incidence of male sex, IVH grade 2, PMA at sepsis diagnosis <28 weeks, and days of mechanical ventilation showed a tendency of a positive association with moderate-to-severe WMA (Table 2). The incidence of PMA at sepsis diagnosis <28 weeks was significantly higher in infants with moderate-to-severe WMA (88.9 vs. 46.0%, p Z 0.028 by Fisher’s exact test), and WM scores were significantly higher in infants diagnosed with sepsis before PMA 28 weeks than in infants diagnosed with sepsis after PMA 28 weeks (mean standard deviation, 7.3 2.47 vs. 6.2 1.40, p Z 0.031). For the multivariate logistic regression analysis including independent variables and confounders, PMA at sepsis diagnosis (OR: 0.640, 95% CI: 0.435e0.941, p Z 0.023) and PMA at sepsis diagnosis <28 weeks (OR: 9.232, 95% CI: 1.020e83.590, p Z 0.048), respectively, were retained as independently associated variables with moderate-to-severe WMA (Table 3). The correlation analysis showed that the PMA at sepsis diagnosis had a significant negative correlation with WM scores (r Z 0.243, p Z 0.039) (Fig. 2).
4. Discussion In the present study, PMA at sepsis diagnosis was an important risk factor for moderate-to-severe WMA. In particular, if sepsis occurred before PMA 28 weeks, the risk of moderate-to-severe WMA was potentially higher. In recent studies using MRI to determine the spectrum of WMA in premature newborns, the incidence of focal cystic necrosis with loss of all cellular elements has distinctly decreased, whereas non-cystic WMA has become the most prevalent pattern of brain injury in premature newborns.25 Non-cystic WMA is a cell-specific lesion with acute loss of early differentiating oligodendrocytes, also known as premyelinating oligodendrocytes (pre-OLs).7 Pre-OLs represent a specific phase of the oligodendroglial lineage that is highly susceptible to hypoxia-ischemia and systemic infection/inflammation.26 Pre-OLs are present as early as 18 weeks and comprise approximately 90% of the total oligodendroglial population until approximately 28 weeks gestation.7,9,27 After 28 weeks gestation, expansion of the immature OL population is prominent.27 Therefore, the timing of insults to the developing brain is a critical factor
Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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Sepsis and white matter abnormality Table 2
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Comparison of the characteristics based on severity of white matter abnormality.
Demographics and perinatal factors Gestational age, weeks, mean SD Birth weight, grams, mean SD Male, n (%) C-section delivery, n (%) Clinical or histological chorioamnionitis, n (%) Histological funisitis, n (%) Prenatal medications Glucocorticoids, n (%) Antibiotics, n (%) Apgar score, 1 min, mean SD Apgar score, 5 min, mean SD Cord blood pH, mean SD Cord blood base excess, mmol/L, mean SD Postnatal factors Treated PDA, n (%) Moderate to severe BPD, n (%) Use of systemic steroids for BPD, n (%) IVH Grade 2, n (%) IVH Grade 2 IVH Grade 3 IVH Grade 4 ROP stage 3, n (%) NEC stage 2, n (%) Surgical NEC, n (%) Hypotension during hospitalization, n (%) Mechanical ventilation, days, mean SD Hospital stay, days, mean SD PMA at brain MRI, weeks, mean SD Sepsis-related factors PMA at sepsis diagnosis, weeks, mean SD PMA at sepsis diagnosis <28 weeks, n (%) PND at sepsis diagnosis, days, mean SD Sepsis onset time Early onset sepsis, n (%) Late onset sepsis, n (%) Late, late onset sepsis, n (%) Pathogen Gram positive, n (%) Gram negative, n (%) Fungus, n (%) MDR bacteria, n (%) Combined meningitis, n (%) Recurrent sepsis, n (%) Hypotension during sepsis, n (%) Central vascular catheter, n (%) Surgery, n (%) Duration of positive to negative conversion of blood culture results, hours, mean SD Duration from sepsis onset to use of susceptible antibiotics, hours, mean SD
None-to-mild (n Z 63)
Moderate-to-severe (n Z 9)
p-value
25þ4 1.473 726 151 31 (49.2) 35 (55.6) 34 (54.0) 11 (17.5)
24þ4 1.120 734 147 7 (77.8) 5 (55.6) 5 (55.6) 1 (11.1)
0.043a 0.952a 0.158b >0.99b >0.99b >0.99b
52 (82.5) 36 (58.1) 3.2 1.726 5.6 1.485 7.303 0.089 3.4 3.965
6 (66.7) 4 (44.4) 2.3 1.581 5.0 0.866 7.282 0.118 5.5 5.848
0.363b 0.490b 0.119a 0.099a 0.883a 0.466a
56 (88.9) 48 (76.2) 9 (14.3) 13 (20.6) 12 (19.0) 1 (1.6) 0 (0) 31 (49.2) 17 (27.0) 15 (23.8) 53 (84.1) 48 34.375 114 34.065 38þ5 2.784
8 (88.9) 8 (88.9) 2 (22.2) 5 (55.6) 3 (33.3) 0 (0) 2 (22.2) 6 (66.7) 4 (44.4) 3 (33.3) 7 (77.8) 68 28.403 131 44.011 39þ5 4.545
>0.99b 0.673b 0.619b 0.038b
0.480b 0.433b 0.682b 0.639b 0.114a 0.250a 0.878a
28þ2 3.001 29 (46.0) 19 17.044
25þ6 1.783 8 (88.9) 10 9.488
0.011a 0.028b 0.054a
7 (11.1) 46 (73.0) 10 (15.9)
2 (22.2) 7 (77.8) 0 (0.0)
0.312b >0.99b 0.343b
46 (73.0) 13 (20.6) 13 (20.6) 34 (54.0) 1/42 (2.4) 13 (20.6) 27 (42.9) 54 (85.7) 10 (15.9) 88 51.025
6 (66.7) 3 (33.3) 2 (22.2) 7 (77.8) 0/4 (0.0) 2 (22.2) 3 (33.3) 8 (88.9) 0 (0.0) 72 38.502
0.701b 0.406b >0.99b 0.283b >0.99b >0.99b 0.667b >0.99b 0.343b 0.438a
34 29.803
50 40.453
0.217a
Bold values indicate p-value < 0.2. BPD, Bronchopulmonary dysplasia; IVH, Intraventricular hemorrhage; MDR, Multi-drug resistant; MRI, Magnetic resonance imaging; NEC, Necrotizing enterocolitis; PDA, Patent ductus arteriosus; PMA, Postmenstrual age; PND, Postnatal day; ROP, Retinopathy of prematurity; SD, Standard deviation. a ManneWhitney U test. b Fisher’s exact test.
Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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J.S. Heo et al Table 3
Logistic regression analysis for predicting moderate-to-severe white matter abnormality.
Variable
PMA at sepsis diagnosis, weeks PMA at sepsis diagnosis <28 weeks
Adjusted modela
Unadjusted model OR
95% CI
p-value
OR
95% CI
p-value
0.637 9.379
0.432e0.939 1.107e79.486
0.023 0.040
0.640 9.232
0.435e0.941 1.020e83.590
0.023 0.048
CI, Confidence interval; OR, Odds ratio; PMA, Postmenstrual age. a Dependent variable þ independent variables þ confounders (including clinical or histological chorioamnionitis, necrotizing enterocolitis stage 2, bronchopulmonary dysplasia and recurrent sepsis).
contributing to WMA. Our data demonstrating that PMA at sepsis diagnosis, particularly before 28 weeks, correlates with moderate-to-severe WMA are consistent with these findings. Although many animal studies correspond well with this hypothesis,28e30 there have been few clinical studies analyzing the relationship between the timing of sepsis and the severity of WMA. The present study has considerable value, in that the results suggest a significant effect of the timing of systemic infection on WMA in extremely preterm infants. In the present study, hypotension during sepsis or hospitalization was not correlated with moderate-to-severe WMA. A potentiating interaction between hypoxia-ischemia and systemic infection/inflammation has been demonstrated in previous studies,31,32 although our results contradict those results. We can think of two reasons for this discrepancy. First, hypotension itself is not well defined. Generally, most neonatologists consider hypotension present if the infant’s mean arterial pressure is less than the GA in weeks.33,34 However, by this definition,
hypotension does not always accompany cerebral hypoperfusion. Lightburn et al.35 observed no significant difference in cerebral blood flow velocity between extremely low birth weight infants with hypotension and infants with normal blood pressure. Moreover, in a study by Bonestroo et al.,36 antihypotensive treatment did not induce any significant change in regional cerebral oxygen saturation or fractional tissue oxygen extraction in hypotensive preterm infants without PDA. Therefore, hypoperfusion may not have occurred in the hypotensive infants in the present study, resulting in no hypoxia-ischemia in the brain. Second, the potentiation between systemic infection/inflammation and hypoxia-ischemia depends on the relative timing of the insults.7 In the rat pup model employed by Eklind et al.,37 lipopolysaccharide enhanced vulnerability during both the acute and chronic phases after administration, whereas an intermediate interval between lipopolysaccharide treatment and hypoxia-ischemia resulted in tolerance rather than potentiation. In the present study, we did not consider the timing of the insults between
Figure 2 Scatter plot and linear line showing white matter scores as a function of postmenstrual age at sepsis diagnosis. PMA, Postmenstrual age; WM, White matter.
Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008
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Sepsis and white matter abnormality systemic infection and hypoxia-ischemia, and the time intervals between these insults were likely heterogeneous. According to the Fisher’s exact test in the present study, IVH combined with sepsis was correlated with moderate-tosevere WMA. When IVH develops, the amount of nonprotein-bound iron in the CSF increases, and this free iron could be used to convert hydrogen peroxide to hydroxyl radical via the Fenton reaction.38 Free radical generation is the most important downstream mechanism of WM injury, as free radical attack appears to be the principal final common pathway to injury.7 In addition, increased methemoglobin formation in the intraventricular space following IVH induces expression of pro-inflammatory cytokines.39 These cytokines potentiate maturationdependent toxicity, affecting pre-OLs.13 Therefore, we conducted IVH grade 2, 3-adjusted analysis, and IVH grade 4 cases were excluded, unless occurring during the septic events, due to significant impacts on WMA scores. In the present study, recurrent postnatal sepsis was not associated with moderate-to-severe WMA. Furthermore, including NEC and prenatal CAM as additional inflammatory events did not affect the results. In recurrent systemic infection, the development of pre-OLs can be inhibited by toxicity or by direct activation of receptors on pre-OLs such as Toll-like receptors or interferon-g,7 and this inhibition of pre-OL development may be associated with progressive WM injury in preterm infants.15 However, in a study by Glass et al.,15 seven of 12 infants with progressive WM injury exhibited progression from none to minimal WM injury, and no progression to moderate or severe injury was observed. In the present study, we compared none-to-mild WMA with moderate-to-severe WMA, as we could not investigate the progression of WMA due to the lack of serial brain MRI studies. The WM scores were higher in infants with recurrent postnatal sepsis than in infants without recurrent sepsis, although this difference was not significant (mean standard deviation, 7.0 2.71 vs. 6.7 1.89, p Z 0.847). There were several limitations to this study. First, the small sample size and relative rarity of moderate-to-severe WMA limited our statistical analyses, which were insufficient to confirm the effects of hypotension and recurrent sepsis on WMA. Despite this limitation, PMA at sepsis diagnosis, especially before 28 weeks, was identified as a risk factor for moderate-to-severe WMA. Second, the data on combined meningitis were imprecise, as many infants did not undergo lumbar puncture based on the decision of the treating physician. This lack of precision could explain why meningitis was not associated with WMA. Third, several infants experienced recurrent septic events. In the statistical analysis, the pathogen, the presence of combined meningitis, hypotension during sepsis, central vascular catheters, surgery, duration of positive to negative conversion of blood culture results, and duration from sepsis onset to use of susceptible antibiotics were determined for each individual episode of sepsis. These factors were different for each episode in patients with recurrent sepsis, and therefore, it is difficult to evaluate the precise risk factors in such cases. Finally, we have no data on long-term neurodevelopmental outcomes relative to the severity of WMA in our study. Further investigations of the associations between WMA and neurodevelopmental outcomes are needed.
7
5. Conclusions This study suggests that PMA at sepsis diagnosis might be an important risk factor for moderate-to-severe WMA in extremely premature infants with neonatal sepsis. Infants diagnosed with sepsis before PMA 28 weeks represent a high-risk group for moderate-to-severe WMA. These findings could be considered when determining the target of neuroprotective treatments in premature infants with sepsis.
Funding This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2012R1A1A2044109).
Conflicts of interest None declared.
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Appendix A. Supplementary data Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.pedneo.2017.07.008.
Please cite this article in press as: Heo JS, et al., Timing of sepsis is an important risk factor for white matter abnormality in extremely premature infants with sepsis, Pediatrics and Neonatology (2017), http://dx.doi.org/10.1016/j.pedneo.2017.07.008