Drains are sometimes necessary for managing fluid accumulations or prophylactically when postoperative fluid accumulation is likely due to dead space or wounds in high-motion areas. Although drain placement can be beneficial, drains increase the risk for infection in clean wounds, as they are foreign bodies and interfere with normal host defense mechanisms.1,2 Drains are categorized as passive or active.
Passive (ie, open) drains draw fluid from the wound via a combination of a typically higher pressure in the wound in combination with gravity and capillary action along the drain surface.1,3 Dependent drainage must be established for these drains to work effectively. The most common passive drain used in veterinary medicine is the Penrose drain, which is composed of soft latex or silicone tubing and available in widths from ¼ in to 1 in. Because fluid flows along the outside of the drain rather than through it, fenestrating Penrose drains decreases their effectiveness. Tubing with stiffer walls can be used but offers no real advantage because the fluid still flows along the drain surface. Passive drain materials are readily available and typically cost less than active drainage systems but are less efficient in evacuating fluid and may cause skin irritation at the exit site due to moisture accumulation. In addition, sterile dressings used to cover the drains may need to be changed multiple times daily, depending on the amount of drainage, and can quickly offset the initial lower cost.
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