RESUMO
BACKGROUND: The Norwood procedure consists of three palliative operations, performed in neonates with hypoplastic left heart syndrome. Especially the first stage (Norwood I) is associated with the highest mortality rates in paediatric cardiac surgery (up to 25%). During surgery, the aorta is reconstructed and a systemic-to-pulmonary shunt is applied. Originally the modified Blalock-Taussig shunt was used, but recently the right-ventricle-to-pulmonary-artery shunt is increasingly being employed. We reviewed the results of our operative strategy, where an individualised choice of shunt is made. Furthermore, attempts to reduce interstage mortality (between Norwood I and II) were assessed. METHODS: All neonates who underwent Norwood stage I palliation from August 2004 until November 2010 were included in this retrospective analysis. Mortality rates and management strategies were compared. RESULTS: Thirty-six patients were available for analysis. Overall 30-day mortality was 5.6% (2 patients) and interstage mortality after discharge was 14% (5 patients). In 2006, a novel clinical protocol was introduced, aimed at reduction of mortality during the interstage period. This resulted in reduction of interstage mortality from 23% to 9% (3 of 13 infants, versus 2 of 23), with a cumulative survival of 82% (maximum follow-up 4 years). CONCLUSION: Early surgical results following the Norwood procedure using an individualised shunt choice are favourable.
RESUMO
Illicit trafficking of fissionable material in container cargoes is recognized as a potential weakness in Nuclear Security. Triggered by the attacks of 11 September 2001, measures were undertaken to enhance maritime security in extension to the Safety Of Life At Sea Convention and in line with the US Container Security Initiatives. Effective detection techniques are needed that allow the inspector to intercept illicit trafficking of nuclear weapons components or components of other nuclear explosive devices. Many security measures focus on active interrogation of the container content by X-ray scan, which might be extended with the newly developed tagged neutron inspection system. Both active interrogation techniques can, with the current huge volume of container traffic, only be applied to a limited number of selected containers. The question arises whether a passive detection technique can offer an alternative solution. This study investigates if containers equipped with a small passive detector will register during transport the neutron irradiation by fissionable material such as plutonium in a measurable way. In practice, 4/5 of the containers are about 1/8 filled with hydrogenous material and undergo a typical 2 months route. For this reference case, it was found that the most compatible passive detector would be an activation foil of iridium. Monte-Carlo simulations showed that for the reference case the activity of a 250 microm thin foil with 6 cm(2) cross-section would register 1.2 Bq when it is irradiated by a significant quantity of Reactor-Grade PuO(2). However this activity drops with almost two orders of magnitude for other fillings and other isotopic compositions and forms of the Pu-source. The procedure of selecting the target material for Pu detection is detailed with the theoretical methods, in order to be useful for other applications. Moreover the value of such additional passive sensors for securing maritime container transport is situated within the global framework of the First, Second and Third Line of Defense against illicit trafficking.