The role of red cell aggregation as a cause of ultrasonic echogenicity in flowing blood was evaluated by in vitro experiments using fresh human blood. Blood was circulated in tubes of varying diameter (12 mm to 6 mm). In all experiments, echogenicity increased as blood approached static conditions. Echogenicity was greater in tubes with a larger diameter over the same range of blood velocity. However, echogenicity in tubes of various diameters was the same when evaluated in terms of shear rate. Thus, shear rate and not velocity is the flow condition that determines echogenicity. Since shear rate determines the degree of red cell aggregation, while other conditions affecting red cell aggregation (hematocrit, erythrocyte membrane conditions, and plasma macromolecules) are held constant, we conclude that these results provide additional evidence that red cell aggregation is a cause of echogenicity in flowing blood. Furthermore, a red cell aggregation mechanism for blood-flow echogenicity would explain the increased prominence of internal echoes in lower shear rate venous blood flow compared with those of higher shear rate arterial blood flow.

RESUMO As hérnias inguinais são um problema frequente e o seu reparo representa a cirurgia mais comumente realizada por cirurgiões gerais. Nos últimos anos, novos princípios, produtos e técnicas têm mudado a rotina dos cirurgiões que precisam reciclar conhecimentos e aperfeiçoar novas habilidades. Além disso, antigos conceitos sobre indicação cirúrgica e riscos de complicações vêm sendo reavaliados. Visando criar um guia de orientações sobre o manejo das hérnias inguinais em pacientes adultos, a Sociedade Brasileira de Hérnias reuniu um grupo de experts com objetivo de revisar diversos tópicos, como indicação cirúrgica, manejo perioperatório, técnicas cirúrgicas, complicações e orientações pós-operatórias.

In contmdistinction to the widespread use of imaging ultrasound in exmnining many other l'egions of the body, ultrasonography of the centralnervow; system has been seriously limited because high· frequency ultrasound dues not readily penetrate the bon y covering of this organ system. The difl'iculty in using ultrasound to visualize lm1in and spinal cord structm·es is a paradox in the history of medical ultr:•sonogmphy hecause much of the interest in the early days of this field of diagnostic imaging was in the central nervous system. ~lore than 30 years ago, French et a!. used A-mode s<:anning to localize il subcortical brain tumor in an e:\+ cised postmortem specimen. U! Advances in central nervous system ultrasonography have been made, however, in applic.ltions in which the skull or vertebral bodies have not impeded the pasage of ultrasound waves. There have been three pl'incipal areas of such applkations: postoperative scanning through craniectomy portals, : l .~ imaging through the fontanels of infants,5·6 and intraoperative ultrasonography.Operative use of imaging ultrasound for brain disease was first employed in the 1960s. ' :' "-II However, the A-mode scanning available then presented problems of interpretation which prevented widespread applkation of this dia~nostic tool. ~lore recent adnmces in ultrasound technology, particularly the development of high-resolution real-time B-mode scanners, have eliminated manv of the em~ lier difHculties in operative imaf,ting. This IHL'i re· suited in u renewed trial of ultrasonic scanning in various types of operations on the hrain 1 :2 -:H and spinal cord. ~. 2l iAs part of a pro~ra m to assess the utility of op· erative ultrasonography in a number of surgical dis· ciplines. we employed ultrasound imaging during brain and spinal cord surgery. \Ve have reviewed our experience of spedfic applications in terms of the impact of ultrasonography on management during opemtion. From this analysis we have de· termined the situations in which ultrasonograph~· during neurosurgery can be most helpful. This analvsis has enabled us to establish criteria for the most productive use of ultrasound during brain and spinal cord surgery and is the basis of this report. METHODSOperative ultrasonography during neurosurgical procedures was performed with real-time B-mode instruments employing mechanically driven sectorscanning transducers. High Stoy. Philips, and Dia-155

We conclude that an accurate open preperitoneal approach using mesh prosthesis for complex inguinal hernias is safe, with very low recurrent rates and low morbidity. Progressive preoperative pneumoperitoneum for giant hernias was shown to be an important factor in accomplishing good intraoperative and immediate postoperative results.