Evaluation of the effects of esophageal varicosclerosants on local vascular occlusion and systemic blood coagulation

Vascular effects induced by combined 1-MHz ultrasound and microbubble contrast agent treatments in vivo

Previous in vivo studies have demonstrated that microvessel hemorrhages and alterations of endothelial permeability can be produced in tissues containing microbubble-based ultrasound contrast agents when those tissues are exposed to MHz-frequency pulsed ultrasound of sufficient pressure amplitudes. The general hypothesis guiding this research was that acoustic (viz., inertial) cavitation, rather than thermal insult, is the dominant mechanism by which such effects arise. We report the results of testing five specific hypotheses in an in vivo rabbit auricular blood vessel model: (1) acoustic cavitation nucleated by microbubble contrast agent can damage the endothelia of veins at relatively low spatial-peak temporal-average intensities, (2) such damage will be proportional to the peak negative pressure amplitude of the insonifying pulses, (3) damage will be confined largely to the intimal surface, with sparing of perivascular tissues, (4) greater damage will occur to the endothelial cells on the side of the vessel distal to the source transducer than on the proximal side and (5) ultrasound/contrast agent-induced endothelial damage can be inherently thrombogenic, or can aid sclerotherapeutic thrombogenesis through the application of otherwise subtherapeutic doses of thrombogenic drugs. Auricular vessels were exposed to 1-MHz focused ultrasound of variable peak pressure amplitude using low duty factor, fixed pulse parameters, with or without infusion of a shelled microbubble contrast agent. Extravasation of Evans blue dye and erythrocytes was assessed at the macroscopic level. Endothelial damage was assessed via scanning electron microscopy (SEM) image analysis. The hypotheses were supported by the data. We discuss potential therapeutic applications of vessel occlusion, e.g., occlusion of at-risk gastric varices.

Efeitos do oleato de etanolamina na parede venosa, de cães

OBJETIVO: Avaliar a resposta biológica que o oleato de etanolamina possa desencadear na parede de veias superficiais normais de cães. MÉTODOS: Utilizados 39 cães, sem raça definida, adultos, machos, com peso variando entre 10 a 18 kg, distribuídos de modo aleatório em três grupos: grupo 1, avaliados após 7 dias, grupo 2, 14 dias e grupo 3, 21 dias. O procedimento foi realizado em duas fases. A primeira constou da injeção de 2 ml do oleato de monoetanolamina a 5%, por punção única na veia cefálica do membro torácico do cão. A segunda, realizada 7, 14 e 21 dias após, constou da retirada da peça operatória, tendo sido executada em três tempos diferentes, conforme o grupo a que pertencia o animal. As veias contralaterais foram extraídas como controle. Para estudo histológico utilizaram-se os métodos de hematoxilina-eosina e tricrômio de Masson. RESULTADOS: A trombose venosa e a organização do trombo ocorreram em todos animais estudados. A recanalização do trombo não foi observada de modo estatisticamente significante, até 21 dias de exame. Encontrou-se lesão de túnica média, que não foi acompanhada de correspondente processo inflamatório. Na túnica adventícia este processo foi visto nos três períodos de tempo estudados. Depósitos de hemossiderina em fagócitos ocorreram aos 14 e 21 dias de experimento. Extravasamento de esclerosante foi observado somente na primeira semana de estudo. Material hialino fibrinóide foi encontrado aos 21 dias de experimento. CONCLUSÕES: O oleato de etanolamina em contato com a parede interna da veia superficial produziu trombose venosa, a qual se organizou em todos os casos, não se observando sua recanalização durante o tempo deste ensaio. Houve lesão da túnica média venosa em todos animais estudados, sem que houvesse processo inflamatório reativo nesse local. Na túnica adventícia venosa surgiu processo inflamatório, além de sinais de extravasamento do esclerosante, da presença de hemossiderina e de material hialino externos à veia.

2-Octyl-cyanoacrylate (Dermabond), a new glue for variceal injection therapy: results of a preliminary animal study

BACKGROUND

Endotherapy of bleeding gastric varices is problematic. The aim of this descriptive study in an animal model was to compare 2-octyl-cyanoacrylate (Dermabond), a Food and Drug Administration-approved agent for superficial wound closure, to N-butyl-2-cyanoacrylate (Histoacryl), an agent available outside of the United States for the endoscopic treatment of bleeding gastric varices.

METHODS

Eight New Zealand white rabbits were randomly assigned to either the study agent Dermabond or the control agent, Histoacryl. Both active agents were equally mixed with ethiodized poppy seed oil (Ethiodol) and injected into the auricular vein. The animals were euthanized at various time intervals after injection. A 2 cm strip of tissue on either side of the injection site along with the adjacent perivascular tissues were resected for histologic evaluation.

RESULTS

The use of 0.5 mL of Dermabond effectively induced vascular occlusion compared with 0.2 mL of Histoacryl. The histologic changes acutely and at 1 week were similar with each mixture.

CONCLUSION

Dermabond may be useful in the treatment of gastric variceal bleeding, but further studies are necessary to determine dose response rates in animals and humans.