Early blood pressure, antihypotensive therapy and outcomes at 18–22 months’ corrected age in extremely preterm infants

Investigate relationships between early blood pressure (BP) changes, receipt of anti-hypotensive therapy, and 18 – 22 month corrected age (CA) outcomes for extremely preterm infants

Structural design of the DIII-D radiative divertor

The divertor of the DIII-D tokamak is being modified to operate as a slot type, dissipative divertor. This modification, called the Radiative Divertor Program (RDP) is being carried out in two phases. The design and analysis is complete and hardware is being fabricated for the first phase. This first phase consists of an upper divertor baffle and cryopump to provide some density control for high triangularity, single or double null discharges. Installation of the first phase is scheduled to start in October, 1996. The second phase provides pumping at all four divertor strike points of double null high triangularity discharges and baffling of the neutral particles from transport back to the core plasma. Studies of the effects of varying the slot length and width of the divertor can be easily accomplished with the design of RDP hardware. Static and dynamic analyses of the baffle structures, new cryopumps, and feedlines were performed during the preliminary and final design phases. Disruption loads and differential thermal displacements must be accommodated in the design of these components. With the full RDP hardware installed, the plasma current in DIII-D will be a maximum of 3.0 MA. Plasma disruptions induce toroidal currents in the cryopump, producing complex dynamic loads. Simultaneously, the vacuum vessel vibrations impose a sinusoidal base excitation to the supports for the cryopump. Static and dynamic analyses of the cryopump demonstrate that the stresses due to disruption and thermal loadings satisfy the stress and deflection criteria

Early Blood Gas Predictors of Bronchopulmonary Dysplasia in Extremely Low Gestational Age Newborns

Aim. To determine among infants born before the 28th week of gestation to what extent blood gas abnormalities during the first three postnatal days provide information about the risk of bronchopulmonary dysplasia (BPD). Methods. We studied the association of extreme quartiles of blood gas measurements (hypoxemia, hyperoxemia, hypocapnea, and hypercapnea) in the first three postnatal days, with bronchopulmonary dysplasia, among 906 newborns, using multivariable models adjusting for potential confounders. We approximated NIH criteria by classifying severity of BPD on the basis of the receipt of any O 2 on postnatal day 28 and at 36 weeks PMA and assisted ventilation. Results. In models that did not adjust for ventilation, hypoxemia was associated with increased risk of severe BPD and very severe BPD, while infants who had hypercapnea were at increased risk of very severe BPD only. In contrast, infants who had hypocapnea were at reduced risk of severe BPD. Including ventilation for 14 or more days eliminated the associations with hypoxemia and with hypercapnea and made the decreased risk of very severe BPD statistically significant. Conclusions. Among ELGANs, recurrent/persistent blood gas abnormalities in the first three postnatal days convey information about the risk of severe and very severe BPD

Early postnatal hypotension and developmental delay at 24 months of age among extremely low gestational age newborns

To evaluate, in extremely low gestational age newborns (ELGANs), relationships between indicators of hypotension during the first 24 postnatal hours and developmental delay at 24 months of age

Early postnatal hypotension is not associated with indicators of white matter damage or cerebral palsy in extremely low gestational age newborns

ObjectivesTo evaluate, in extremely low gestational age newborns (ELGANs), relationships between indicators of early postnatal hypotension and cranial ultrasound indicators of cerebral white matter damage imaged in the nursery and cerebral palsy diagnoses at 24 month follow-up.MethodsThe 1041 infants in this prospective study were born at < 28 weeks gestation, were assessed for 3 indicators of hypotension in the first 24 postnatal hours, had at least one set of protocol cranial ultrasound scans, and were evaluated with a structured neurologic exam at 24 months corrected age. Indicators of hypotension included: 1) lowest mean arterial pressure (MAP) in the lowest quartile for gestational age; 2) treatment with a vasopressor; and 3) blood pressure lability, defined as the upper quartile of the difference between each infant’s lowest and highest MAP. Outcomes included indicators of cerebral white matter damage, i.e. moderate/severe ventriculomegaly or an echolucent lesion on cranial ultrasound, and cerebral palsy diagnoses at 24 months gestation. Logistic regression was used to evaluate relationships among hypotension indicators and outcomes, adjusting for potential confounders.ResultsTwenty-one percent of surviving infants had a lowest blood pressure in the lowest quartile for gestational age, 24% were treated with vasopressors, and 24% had labile blood pressure. Among infants with these hypotension indicators, 10% percent developed ventriculomegaly and 7% developed an echolucent lesion. At 24-months follow-up, 6% had developed quadriparesis, 4% diparesis, and 2% hemiparesis. After adjusting for confounders, we found no association between indicators of hypotension, and indicators of cerebral white matter damage or a cerebral palsy diagnosis.ConclusionsThe absence of an association between indicators of hypotension and cerebral white matter damage and or cerebral palsy suggests that early hypotension may not be important in the pathogenesis of brain injury in ELGANs

Evolving blood pressure dynamics for extremely preterm infants

ObjectiveTo examine changes in arterial blood pressure (ABP) after birth in extremely preterm infants.Study DesignProspective observational study of infants 230/7 – 266/7 weeks gestational age (GA). Antihypotensive therapy use and ABP measurements were recorded for the first 24 hours.ResultsA cohort of 367 infants had 18,709 ABP measurements recorded. ABP decreased for the first three hours, reached a nadir at 4 – 5 hours, then increased at an average rate of 0.2 mmHg / hour. The rise in ABP from hour 4 – 24 was similar for untreated infants (n=164) and infants given any antihypotensive therapy (n=203), a fluid bolus (n=135), or dopamine (n=92). GA specific trends were similar. ABP tended to be lower as GA decreased, but varied widely at each GA.ConclusionArterial blood pressure increased spontaneously over the first 24 postnatal hours for extremely preterm infants. The rate of rise in ABP did not change with antihypotensive therapy

Design of the advanced divertor pump cryogenic system for DIII-D

The design of the cryogenic system for the D3-D advanced divertor cryocondensation pump is presented. The advanced divertor incorporates a baffle chamber and bias ring located near the bottom of the D3-D vacuum vessel. A 50,000 l/s cryocondensation pump will be installed underneath the baffle for plasma particle exhaust. The pump consists of a liquid helium cooled tube operating at 4.3{degrees}K and a liquid nitrogen cooled radiation shield. Liquid helium is fed by forced flow through the cryopump. Compressed helium gas flowing through the high pressure side of a heat exchanger is regeneratively cooled by the two-phase helium leaving the pump. The cooled high pressure gaseous helium is than liquefied by a Joule-Thomson expansion valve. The liquid is returned to a storage dewar. The liquid nitrogen for the radiation shield is supplied by forced flow from a bulk storage system. Control of the cryogenic system is accomplished by a programmable logic controller

Feasibility Study of Early Blood Pressure Management in Extremely Preterm Infants

To assess the feasibility of a randomized placebo controlled trial (RCT) of blood pressure (BP) management for extremely preterm infants

Effect of Catheter Dwell Time on Risk of Central Line-Associated Bloodstream Infection in Infants

Central venous catheters in the NICU are associated with significant morbidity and mortality because of the risk of central line–associated bloodstream infections (CLABSIs). The purpose of this study was to determine the effect of catheter dwell time on risk of CLABSI

Neonatal cerebrovascular autoregulation.

Cerebrovascular pressure autoregulation is the physiologic mechanism that holds cerebral blood flow (CBF) relatively constant across changes in cerebral perfusion pressure (CPP). Cerebral vasoreactivity refers to the vasoconstriction and vasodilation that occur during fluctuations in arterial blood pressure (ABP) to maintain autoregulation. These are vital protective mechanisms of the brain. Impairments in pressure autoregulation increase the risk of brain injury and persistent neurologic disability. Autoregulation may be impaired during various neonatal disease states including prematurity, hypoxic-ischemic encephalopathy (HIE), intraventricular hemorrhage, congenital cardiac disease, and infants requiring extracorporeal membrane oxygenation (ECMO). Because infants are exquisitely sensitive to changes in cerebral blood flow (CBF), both hypoperfusion and hyperperfusion can cause significant neurologic injury. We will review neonatal pressure autoregulation and autoregulation monitoring techniques with a focus on brain protection. Current clinical therapies have failed to fully prevent permanent brain injuries in neonates. Adjuvant treatments that support and optimize autoregulation may improve neurologic outcomes