Complications in Equine Surgery. Группа авторов

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Complications in Equine Surgery - Группа авторов


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a unit together into the vein to overcome skin friction or past valve leaflets or by injecting sterile saline into the catheter as it is being advanced to distend the vein. If the guidewire is verified to be in the vein but cannot be advanced, options include placement of the catheter in a different vein or more distally in the vein or securing an over‐the‐wire catheter without inserting it to its full length (which is allowed by the catheter clamp and fastener included in the kit). Catheter patency may be restored in some of these occluded catheters by aspirating the thrombus from the catheter, if possible. It is important to recognize that this may be an early sign of a more serious problem, such as bending or breakage if the catheter is composed of stiff materials, or early signs of thrombophlebitis. Therefore, catheter removal should be considered in these cases and if the catheter is maintained, strategies should be used to reposition the catheter (resuturing, catheter wraps or bandaging, maintaining the horse’s head in a more elevated position, etc.).

       Expected outcome

      Use of an alternate site or replacement of the catheter usually resolves the problem. In some cases, hematoma, swelling, thrombophlebitis or infection at the site may develop.

       Definition

      Thrombophlebitis, defined as nonseptic or septic inflammation of the vein, is a common complication of indwelling intravascular catheters.

       Risk factors

       Related to catheter placement: technique, duration of catheterization, orientation of catheter relative to direction of blood flow, and material, length, and diameter of the catheter [1, 2, 4, 11]

       Type of intravenous fluids or medications being administered (e.g. nonsterile fluids, hyperosmolar fluids (parenteral nutrition, 50% dextrose, hypertonic saline), undiluted irritating medications (chemotherapeutic agents, phenylbutazone, amphotericin B, etc.))

       Patient‐related: critical illness, gastrointestinal disease, hypoproteinemia, and endotoxemia are independent risk factors for thrombophlebitis [11]. Patient colonization with methicillin resistant staphylococcus is an anecdotal risk factor.

       Catheter materials ranked in order of decreasing risk of thrombosis are polypropylene > polyethylene > polytetrafluoroethylene > silicone rubber > nylon > polyvinyl chloride > polyurethane > silastic [1, 2, 4, 12].

       Catheter size: Longer and larger diameter catheters are more inflammatory than short, narrow catheters [8, 12].

       Catheter site handling: Catheter sites should be kept clean from environmental contamination, secured, and maintained with aseptic technique.

       Pathogenesis

      Development of thrombophlebitis is related to the inflammatory and pro‐coagulant environment present within the catheterized vessel [11]. Catheter‐related factors (type, duration, contamination, instability), patient‐related factors (concurrent disease, hypoproteinemia, endotoxemia, infection), and infusate characteristics (hyperosmolar, acidic, microparticulate) contribute to the degree of inflammation and coagulable state within the vessel. Bacterial colonization is not always associated with vascular changes [12, 13]; however, septic thrombophlebitis is a serious complication.

       Prevention

      Catheters should be placed and managed aseptically, adequately stabilized, and kept clean and protected from soiling or external trauma, with the caveat that daily inspection should continue despite protective wraps. Some clinicians advocate removal of all catheters after 48–72 hours and replacement in an alternate site if continued use is needed [12]; however, signs of thrombophlebitis can occur within 24 hours and repeated catheterization increases the risk of thrombophlebitis. Administration of low‐molecular weight heparin (dalteparin) in colic patients was associated with less subclinical (ultrasonographic) changes of thrombophlebitis than unfractionated heparin [14]. Non‐steroidal anti‐inflammatory treatment was found to be protective in another study [15]. Reduction in catheter flow may be caused by early development of a thrombus at the catheter tip.

       Diagnosis

       Monitoring

      Source: Courtesy of Pablo Espinosa.

      Source: Courtesy of Pablo Espinosa.

       Treatment


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