Kenneth Tan

An outbreak of necrotizing enterocolitis associated with norovirus genotype GII.3.

Background: Necrotizing enterocolitis (NEC) is an acute abdominal emergency of unknown etiology predominantly affecting preterm infants. We describe a cluster of NEC in a level III NICU involving 15 infants over a 6-month period. Cohorting and stringent infection control measures were associated with termination of the cluster. A case-control study was used to investigate potential risk factors associated with development of NEC. Methods: Stool samples were collected from 55 infants (10 of 15 NEC and 45 non-NEC controls). Enteric pathogens were identified by culture and/or molecular diagnostic techniques. For the case-control study, controls were selected from admitted neonates during the same time and in the preceding 6-month period, matched for gestation and birthweight. Results: Forty percent (4/10) of NEC infants had norovirus RNA detected compared with 9% (4/45) of non-NEC infants (OR: 6.83, 95% CI: 1.3–34.9, P = 0.021). A lower rate of prolonged rupture of membranes and a higher rate of maternal smoking was also observed in NEC infants than in controls. No significant differences in incidences of chorioamnionitis, intrapartum antibiotics, volume of feedings, time of first formula feeding, and rates of patent ductus arteriosus or intrauterine growth retardation were detected. Conclusions: Infants who developed NEC had an increased incidence of norovirus detection in their stool following diagnosis. This further strengthens the case for an etiologic role of norovirus in the pathogenesis of NEC.

Using cognitive task analysis to facilitate the integration of decision support systems into the neonatal intensive care unit

OBJECTIVE New medical systems may be rejected by staff because they do not integrate with local practice. An expert system, FLORENCE, is being developed to help staff in a neonatal intensive care unit (NICU) make decisions about ventilator settings when treating babies with respiratory distress syndrome. For FLORENCE to succeed it must be clinically useful and acceptable to staff in the context of local work practices. The aim of this work was to identify those contextual factors that would affect FLORENCEs success. METHODS A cognitive task analysis (CTA) of the NICU was performed. First, work context analysis was used to identify how work is performed in the NICU. Second, the critical decision method (CDM) was used to analyse how staff make decisions about changing the ventilator settings. Third, naturalistic observation of staffs use of the ventilator was performed. RESULTS A. The work context analysis identified the NICUs hierarchical communication structure and the importance of numerous types of record in communication. B. It also identified important ergonomic and practical requirements for designing the displays and positioning the computer. C. The CDM interviews suggested instances where problems can arise if the data used by FLORENCE, which is automatically read, is not manually verified. D. Observation showed that most alarms cleared automatically. When FLORENCE raises an alarm, staff will normally be required to intervene and make a clinical judgement, even if the ventilator settings are not subsequently changed. CONCLUSIONS FLORENCE must not undermine the NICUs hierarchical communication channels (A). The re-design of working practices to incorporate FLORENCE, reinforced through its user interface, must ensure that expert help is called on when appropriate (A). The procedures adopted with FLORENCE should ensure that the data the advice is based upon is valid (C). For example, FLORENCE could prompt staff to manually verify the data before implementing any suggested changes. FLORENCEs audible alarm should be clearly distinguishable from other NICU alarms (D); new procedures should be established to ensure that FLORENCE alarms receive attention (D), and false alarms from FLORENCE should be minimised (B, D). FLORENCE should always provide the data and reasoning underpinning its advice (A, C, D). The methods used in the CTA identified several contextual issues that could affect FLORENCEs acceptance. These issues, which extend beyond FLORENCEs capability to suggest changes to the ventilator settings, are being addressed in the design of the user interface and plans for FLORENCEs subsequent deployment.

Comparison of singleton and multiple-birth outcomes of infants born at or before 32 weeks of gestation

OBJECTIVE: To compare the outcomes of multiple-birth and singleton very preterm infants who were admitted to neonatal intensive care units (NICUs). METHODS: Three-level hierarchical generalized linear and hierarchical linear model analyses were used to compare the risk-adjusted outcomes of 3,242 infants born at or before 32 weeks of gestational age who were admitted to 24 Canadian NICUs in 2005. RESULTS: With the exception of respiratory distress syndrome (RDS), multiple-birth infants were not at a higher risk than singleton birth infants for death, patent ductus arteriosus, necrotizing enterocolitis, chronic lung disease, severe intraventricular hemorrhage, severe (stages 3 or higher) retinopathy of prematurity, or nosocomial infection, after adjusting for perinatal risks and neonatal illness severity. In addition, multiple-birth infants did not have a more prolonged duration of neonatal intensive care unit stay, duration of length of continuous positive airway pressure use, duration of ventilation, or duration of oxygen use than did singletons. Multiple-birth infants had a higher incidence of RDS (adjusted odds ratio 1.3, 95% confidence interval 1.0–1.6) and a lower incidence of severe retinopathy of prematurity (adjusted odds ratio 0.5, 95% confidence interval 0.3–0.9) than did singletons. CONCLUSION: Multiple-birth and singleton very preterm infants had similar outcomes, except for a higher incidence of RDS among multiple-birth infants. LEVEL OF EVIDENCE: II

Docosahexaenoic Acid and Bronchopulmonary Dysplasia in Preterm Infants

BACKGROUND Studies in animals and in humans have suggested that docosahexaenoic acid (DHA), an n‐3 long‐chain polyunsaturated fatty acid, might reduce the risk of bronchopulmonary dysplasia, but appropriately designed trials are lacking. METHODS We randomly assigned 1273 infants born before 29 weeks of gestation (stratified according to sex, gestational age [<27 weeks or 27 to <29 weeks], and center) within 3 days after their first enteral feeding to receive either an enteral emulsion providing DHA at a dose of 60 mg per kilogram of body weight per day or a control (soy) emulsion without DHA until 36 weeks of postmenstrual age. The primary outcome was bronchopulmonary dysplasia, defined on a physiological basis (with the use of oxygen‐saturation monitoring in selected infants), at 36 weeks of postmenstrual age or discharge home, whichever occurred first. RESULTS A total of 1205 infants survived to the primary outcome assessment. Of the 592 infants assigned to the DHA group, 291 (49.1% by multiple imputation) were classified as having physiological bronchopulmonary dysplasia, as compared with 269 (43.9%) of the 613 infants assigned to the control group (relative risk adjusted for randomization strata, 1.13; 95% confidence interval [CI], 1.02 to 1.25; P=0.02). The composite outcome of physiological bronchopulmonary dysplasia or death before 36 weeks of postmenstrual age occurred in 52.3% of the infants in the DHA group and in 46.4% of the infants in the control group (adjusted relative risk, 1.11; 95% CI, 1.00 to 1.23; P=0.045). There were no significant differences between the two groups in the rates of death or any other neonatal illnesses. Bronchopulmonary dysplasia based on a clinical definition occurred in 53.2% of the infants in the DHA group and in 49.7% of the infants in the control group (P=0.06). CONCLUSIONS Enteral DHA supplementation at a dose of 60 mg per kilogram per day did not result in a lower risk of physiological bronchopulmonary dysplasia than a control emulsion among preterm infants born before 29 weeks of gestation and may have resulted in a greater risk. (Funded by the Australian National Health and Medical Research Council and others; Australian New Zealand Clinical Trials Registry number, ACTRN12612000503820.)

Prevention of central venous catheter-related infection in the neonatal unit: a literature review

Abstract Central venous catheter infections are the leading cause of healthcare-associated bloodstream infections and contribute significantly to mortality and morbidity in neonatal intensive care units. Moreover, infection poses significant economic consequence which increased hospital costs and increased length of hospital stay. Prevention strategies are detailed in guidelines published by the Centers for Disease Control and Prevention (CDC) in the United States; nevertheless, recent surveys in neonatal units in the United States, and Australia and New Zealand demonstrate these are not always followed. This review discusses the numerous evidence-based strategies to prevent catheter infections including hand hygiene, maximal sterile barriers during insertion, skin disinfection, selection of insertion site, dressings, aseptic non-touch technique, disinfection of catheter hubs/ports, administration set management, prompt removal of catheter, antibiotic locks, systemic antibiotic prophylaxis and chlorhexidine bathing. Furthermore, it will describe different strategies that can be implemented into clinical practice to reduce infection rates. These include the use of care bundles including checklists, education and the use of CVC teams.

Spectral Doppler waveforms in systemic arteries and physiological significance of a patent ductus arteriosus

Patent ductus arteriosus in extremely premature babies is associated with major neonatal morbidities, such as necrotizing enterocolitis and intraventricular hemorrhage. This may be attributable, at least in part, to systemic hypoperfusion secondary to ductal steal. A hemodynamically significant ductus arteriosus (HSDA) is known to be associated with altered systemic blood flow and end-organ hypoperfusion. Although descending aorta blood flow profiles may show abnormal diastolic retrograde flow, Doppler studies of blood flow in the systemic arteries may help improve our understanding of the relationship of a HSDA with these morbidities. In this article, we discuss aspects of diastolic blood flow reversal in the systemic arteries in premature infants with a hemodynamically significant duct. Whether these hemodynamic effects are significant enough to form the basis for initiating treatment is still unclear; these should form the basis for prospective studies.

A New Look at Bronchopulmonary Dysplasia: Postcapillary Pathophysiology and Cardiac Dysfunction

Pulmonary hypertension (PH) and right ventricular function are the focus of cardiovascular effects of bronchopulmonary dysplasia (BPD). We assessed cardiac indexes reflecting systemic afterload and pulmonary venous back pressure as pathophysiologic factors. Cardiac parameters were measured by conventional echocardiography in 20 preterm infants with severe BPD and compared with those of 10 preterm infants with no BPD and 20 healthy term infants. In infants with severe BPD, PH was noted in 5 (25%) by tricuspid regurgitation Doppler jet ≥2.8 m/s and in 15 (75%) by time to peak velocity/right ventricular ejection time <0.34. Among systemic cardiac indexes, significant impairment of diastolic measures was noted in the BPD group compared with infants with no BPD and term infants. The significance persisted after adjusting for gestational age and birth weight. These included transmitral E/A ratio (1.07 ± 0.07 vs. 0.91 ± 0.04 vs. 0.89 ± 0.09; P < 0.0001), isovolumic relaxation time (68.8 ± 3.9 vs. 58.5 ± 7.8 vs. 54.2 ± 5.7 ms; P < 0.0001), mitral valve stroke volume (4.7 ± 0.7 vs. 5.6 ± 0.6 vs. 5.9 ± 0.1; P = 0.002), and myocardial performance index (0.33 ± 0.05 vs. 0.28 ± 0.01 vs. 0.27 ± 0.05; P = 0.03). Left ventricular output was significantly lower in the BPD cohort (183 ± 45 vs. 189 ± 9 vs. 191 ± 32 mL/kg/min; P = 0.03). Altered systemic (left-sided) cardiac function was noted in infants with BPD, which may lead to pulmonary venous congestion contributing to a continued need for respiratory support.

Systemic arterial stiffness in infants with bronchopulmonary dysplasia: potential cause of systemic hypertension

Objective:Systemic hypertension is common among preterm infants with severe bronchopulmonary dysplasia (BPD); the exact cause is unknown. The objective of this preliminary hypothesis generating study was to examine systemic arterial structure and vasomotor function in a cohort of preterm infants with severe BPD, using a cohort of preterm infants without BPD and a cohort of term infants for comparison.Study Design:After obtaining informed consent, we measured aortic wall thickness and vasomotor function by ultrasonography in 20 infants with severe BPD, 7 infants with no BPD, and compared them with 20 healthy term infants.Results:Maximum aortic thickness was significantly higher in infants with BPD (827±163 μm) compared to those with no BPD (674±22 μm) and term infants (657±67 μm) (unadjusted P<0.0001). The input impedance was similarly elevated in the infants with BPD (574±127 dynes s cm−5) compared to those with no BPD (325±24 dynes s cm−5) or term infants (328±113 dynes s cm−5) (unadjusted P<0.0001). Stiffness index was significantly higher in the infants with BPD (3.4±0.6) compared to those with no BPD (2.6±0.3) or term infants (2.3±0.4) (unadjusted P<0.0001). Systemic vascular resistance was also significantly elevated in the infants with BPD. The results remained significant even after adjusting for gestational age and birth weight. Measures of vasomotor function significantly correlated with blood pressure.Conclusion:The aortic wall thickness and vasomotor function are significantly altered in preterm infants with severe BPD. These findings may explain the higher incidence of systemic hypertension in this population.

Phototherapy in transport for neonates with unconjugated hyperbilirubinaemia.

In Victoria, neonates with severe unconjugated hyperbilirubinaemia at risk of requiring exchange transfusion are retrieved by the Paediatric Infant Perinatal Emergency Retrieval Service and transferred to a Neonatal Intensive Care Unit where an exchange transfusion can be performed if necessary. Transfer may result in prolonged periods without phototherapy in neonates at risk of developing bilirubin encephalopathy. We aimed to describe our experience of the introduction of phototherapy using a portable phototherapy unit during transport.

Vasopressin as an adjunct therapy for pulmonary hypertension: a case report

Vasopressin is emerging as a therapeutic adjunct option towards treatment of shock states in the pediatric population. Its effects on pulmonary vasculature are less well understood. This report describes a 5-month-old infant with nitric oxide-unresponsive pulmonary hypertension, oxygenation failure, and systemic hypotension. Vasopressin therapy improved oxygenation and blood pressure and biventricular function, allowing weaning of nitric oxide and inotropic support. No decrease in coronary flow was noted. Conclusions: Vasopressin could be considered as an adjunct option in infants with pulmonary hypertension and systemic hypotension. Echocardiographic monitoring during treatment is recommended.