Ординатура / Офтальмология / Английские материалы / Basic Principles of Ophthalmic Surgery_Arnold_2006

chapter 13 I hemostasis

MECHANICAL TAMPONADE

Mechanicaltamponaderefersto the direct application of physicalforce to staunchblood flow from a bleedingvessel.Raisingintraocular pressureis the most common and effective way to mechanicallycontrol intraocular bleeding. Increasedintraocular pressureis translatedinto increasedtransmuralpressure of the blood vesselwall that causescollapseor slowing down of blood flow. This is readily accomplishedbe raisingthe level of the infusion bottle. Elevating the intraocular pressurerisks ocularischemiaand stressto surgicalrepair of surgicalwounds.

Fluid-gas exchangemechanicallyachieveshemostasisby elevatingintraocularpressurevia control of pump pressure.Intraocular gashasa higher surfacetension than intraocular salineand impedesblood flow. Fluid trapped behind a gasbubble has higher concentration of coagulationfactors, which contributes to hemostasis.Intraocular gasesunfortunately canimpedevisibility during surgery,and this techniqueis usually reservedfor the lastminutes of the operation.

Other intraocular substancescanhelp control intraoperative bleeding.Perfluorooctane may control intraocular bleedingduring vitreoretinal surgery by direct compressionor concentration of clotting factors nearthe bleedingsite. Silicone oil controls bleedingby two mechanisms:first, by physicalcompression and secondby concentratingclotting factors in a smallerspace.Silicone oil interferes with other intraocular maneuversand is used typically at the end of surgery.Sodiumhyaluronate mechanicallyconfinesblood and enhances visualization. It unfortunately alsohasmild antiplateletand anticoagulation

properties.

Gelfoam (absorbablegelatinsponge),Surgicel(oxidized regeneratedcellulose), and Avitene (microfibrillar collagen)are useful mechanicalmeasuresto control and confine intraoperative bleedingin ocular adnexalsurgery.

Wound closureis a straightforward technique of mechanicallycontrolling intraoperative bleeding. Direct compressionto bleedingvortex veinsis useful in strabismusand retinal surgerywhere vortex vein injury canoccur.

EMBOLIZATION

arteriography and embolization with polyvinyl alcohol foam,metrizamide dissolvedin dimethyl sulfoxide, steelcoils, gelfoamparticles,and

n-butyl cyanoacrylatehasbeenreported to be useful preoperatively in minimizing hemorrhageduring excisionof orbital lymphangiomasand arte-

Preoperative