We investigated the flow rates of 25-G and 27-G spinal needles, of 90-mm and 120-mm lengths, from Vygon, BD, B. Braun and Pajunk; the needles had either a Luer connector, or a Surety or UniVia non-Luer connector. We used a bench-top model of entering the spinal space, pressurised to 35 cmH O to simulate cerebrospinal fluid pressure in the sitting position. We examined the time to first appearance of simulated cerebrospinal fluid in the needle hub, as well as the amount of fluid collected over 120 s after the needle was introduced. The mean (SD) times to first appearance of fluid in the needle hub of Luer spinal needles varied from 0.36 (0.22) s for the 25-G 90-mm BD to 3.14 (0.72) s for the 27-G 120-mm B. Braun, and in the non-Luer spinal needles from 0.22 (0.17) s for the 25-G 90-mm B. Braun to 2.99 (0.71) s for the 27-G 120-mm Pajunk. There was a significant difference in the time to first appearance of fluid in the needle hub between Luer and non-Luer needles of the same type for seven of 14 comparisons made, of which four showed slower appearance of fluid in the non-Luer version. In some of these cases, the time to appearance of fluid was nearly twice as long with the non-Luer counterpart. The mean (SD) weight of fluid collected in 120 s using the Luer spinal needles varied from 0.21 (0.05) g for the 27-G 120-mm Pajunk to 1.21 (0.18) g for the 25-G 90-mm Vygon, and using the non-Luer spinal needles from 0.25 (0.05) g for the 27-G 120-mm Pajunk to 1.55 (0.05) g for the 25-G 90-mm B. Braun. All of the needle types showed a greater weight of fluid collected using the non-Luer compared with the Luer version, with six of the 14 needle types showing a significant difference. Significant variations in flow were also seen between the same needle type from different manufacturers. We conclude that changing from Luer to non-Luer versions of spinal needles does not merely change the hub design and connection, but may introduce important differences in function.

We investigated the strength of commonly used spinal needles in relation to the amount of deformation, and registered forces during standardised testing. We investigated differences between manufacturers for the same length and gauge of Luer and non-Luer needles, and examined the effect of the internal stylet in terms of needle strength. A specialised rig was designed to perform the testing in both the horizontal and axial plane, reflecting common industrial tests and clinical use. Needles from four commonly used manufacturers were used (Vygon, Becton Dickinson, B Braun, and Pajunk). Needles of 25 G and 27 G were tested in 90-mm and 120-mm lengths. We found significant differences in terms of the size of final deformation and 'toughness'/resistance to deformation between needles of different brands. There were also significant differences between horizontal tests conducted as an industry standard and our own axial test. This may have bearing on clinical use in terms of the incidence of bending and breakage. The presence of the internal stylet resulted in significantly greater toughness in many needles, but had little effect on the degree of deformation. Comparison of Luer and non-Luer needles of the same brand and size showed few significant differences in strength. This result is reassuring, given the imminent change from Luer to non-Luer needles that is to occur in the UK.

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RESUMOO artigo aborda a redução do volume de pasta em concretos autoadensáveis (CAA) com diferentes composições de agregados, verificando o atendimento às propriedades de autoadensabilidade e resistência à compressão. Estudos têm mostrado que as composições de agregados influenciam no volume de pasta necessário para o alcance da autoadensabilidade. Porém, elevados volumes de pasta têm sido utilizados na obtenção de CAA sem nenhum critério de avaliação. Neste contexto, o estudo avalia as propriedades de autoadensabilidade e de resistência à compressão de CAA com diferentes volumes de pasta e composições de agregados. Os CAAs com diferentes composições (binária, ternária e quaternária) de agregados foram inicialmente obtidos com 40 % de pasta, em seguida, novos CAAs foram obtidos com a redução do volume de pasta para 38 %, 35 % e 33 %. Nestes concretos, as propriedades de autoadensabilidade foram avaliadas através dos ensaios de espalhamento (slump flow), Funil V e caixa L. Para os CAA, com 40 % de pasta, foram obtidas curvas experimentais obtendo o módulo de distribuição (q) do modelo de Alfred, o que mostrou que nem sempre o CAA atendem aos "q" indicados na literatura. Os resultados mostraram que o CAA com composição quaternária de agregados atendeu aos parâmetros de autoadensabilidade praticamente em todos os volumes de pasta utilizados, e que o atendimento com as composições binária e ternária, depende do volume de pasta. A resistência à compressão tornou-se maior com o aumento do volume de pasta e do número de combinações de agregados.PALAVRAS CHAVE: composição de agregados, volume de pasta, concreto autoadensável.

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