Drains are used to direct fluid out of a wound or body cavity. Passive drainage techniques require gravity or capillary action to draw fluid from the wound or cavity. Penrose drains are soft, flat, commonly used passive drains made from latex. These drains must be placed in gravity-dependent locations to ensure proper function. A firmer passive drain can be constructed from a red rubber or silicone tube. Active drains require some type of negative pressure to pull fluid from the wound. Red rubber or silicone drains can be used with a closed system, and low-pressure suction can be maintained with the intermittent use of low-pressure pumps or handheld rechargeable devices. Negative-pressure wound therapy is based on this theory to remove purulent debris and speed closure of an open wound. The use of active, closed-drain systems decreases the likelihood of ascending infection that can be associated with passive drains. Drains should be left in place until the draining fluid decreases in quantity and no longer appears purulent. The fluid can be evaluated by cytologic examination.
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