Darren Barnes provides advice on the principles of placement and management of drains within a small animal practice environment.
Darren Barnes
Job Title
Figures 7 and 8. Cover the drain exit with a sterile dressing to prevent contamination of the wound.
A surgical drain is a temporary implant used for removing fluid or air from within a wound or body cavity; and maintenance of tissue apposition and obliteration of dead space.
Table 1. Comparison of Penrose drains and closed suction drains.
Dead space may alternatively be managed by using tacking sutures or pressure bandages – or a combination of these techniques. If a seroma forms when tacking sutures are used, it may form numerous smaller pockets. Hence in some circumstances, drains and dressings may be more appropriate.
Fluid accumulation within a wound may occur where it cannot be completely debrided, is contaminated, or where fluid production may be expected to continue following surgery. Fluid accumulation within a wound increases susceptibility to infection, and hence wound dehiscence, by the following mechanisms:
reducing opsonising activity of phagocytes
compromising vascular supply to the wound
compromising phagocyte access to the wound
substrate accumulation for bacterial growth
The ideal surgical drain would have these properties:
be soft and malleable, to avoid trauma to the tissue and allow ease of placement
contain a radiographic marker to aid postoperative visualisation
induce minimal tissue reaction
be cheap
efficiently prevent fluid accumulation
prevent wicking of bacteria and debris into the wound
Many forms of surgical drainage system are available.
Active drains
A vacuum is used to suction fluid from the wound or body cavity. Suction may be applied through the following methods.
By a closed or a vented system. Vented suction systems also draw air through the wound. These systems are the most efficient at fluid removal, but may lead to tissue trauma and contamination.
Continuously or intermittently. Frequency of drainage with intermittent suctions systems varies with fluid volume production, but should usually be at least every six hours. The advantage of intermittent systems is not having a permanently attached suction system connected to the patient. However, this may disrupt tissue apposition.
Passive drains
Passive drains function by a combination of capillary action, overflow and gravitational and muscular movement to remove fluid from the wound or body cavity. This group includes Penrose drains as well as sump drains, sump-Penrose, corrugated drains and dental dams.
Drainage may also be achieved by open wound drainage or fenestration of the skin over a wound, or by utilisation of the omentum as a natural active drainage system.
The most commonly used and readily available surgical drainage implants are Penrose drains and closed suction systems (Table 1).
Drain placement and management
Drains do not preclude attention to general principles of wound management. Where heavy contamination or necrotic tissue is present, debridement should be employed and delayed wound closure may be preferable to primary closure over a drain. Halstead’s Principles should always be observed.
Having acknowledged that surgical drainage is necessary to prevent fluid accumulation within a wound, it is imperative an appropriate drain is selected for the wound, given its location and expected fluid output. The drain should be placed and managed correctly to prevent wound healing complications as a result of the drain’s presence, and to reduce morbidity.
Penrose drains
A Penrose drain is a tube of soft, malleable, radiopaque latex. Fluid flows predominantly over the external surface of the drain by capillary action and exits the wound under gravity, and may be assisted be muscle movement. The drain provides a path of least resistance. These drains are useful for small wounds with low-volume fluid drainage.
Preoperatively, the patient requires adequate clipping and aseptic preparation of skin around the wound and the proposed exit point for the drain.
The drain should be placed following debridement, lavage and haemostasis of the wound.
The drain is secured within the wound with a single simple interrupted suture. The suture should be placed through the last 1mm of the drain on one side, to gently secure the drain within the wound, but not impede its removal when required (Figure 1).
The drain should not be fenestrated as this will reduce the surface area for capillary flow and increase the risk of tearing at the time of removal.
A single exit point – one-and-a-half to two times the diameter of the drain – should be positioned at a dependent part of the wound. Multiple exit points increase the air and bacteria drawn into the wound, thus risking contamination. Exit points in non-dependent areas of the wound will not allow fluid exit under gravity (Figure 2).
The exit point should be adjacent to, but separate from, the wound, but also not too far away, to promote ease of drainage without impeding healing of the primary wound. This will also allow ongoing drainage following removal of the drainage implant. It may also be necessary to include the drain exit point in a contaminated field requiring further surgery or radiation therapy following oncological resections.
The drain should be cut so 1cm to 2cm exits through the skin. Make sure the drain is slack enough that it won’t be retracted internally or pulled out with limb movement (Figure 3).
The drain’s length should be recorded and checked on removal.
Secure the drain to the skin at the exit point with a single simple interrupted suture.
The exit of the drain should be covered with a sterile, absorbent dressing. This requires changing as often as necessary to prevent strikethrough of the dressing and to maintain asepsis.
In rare cases where the drain exit cannot be covered, the exit should be regularly cleaned with dilute chlorhexidine or saline, and the surrounding skin protected with petroleum jelly.
Figure 1. Correct positioning of the suture.
Figure 2. Use a single exit point.
Figure 3. Leave 1.0cm to 2cm outside the skin.
Close suction drains
Several different systems of closed suction drains are available (Figures 4 to 6), relying on either a pre-evacuated solid container or collapsible collection chamber with an inherent tendency to re-inflate, hence applying negative pressure to the drain. Alternatively, a simple system may be constructed with a length of tubing and a 20ml syringe, maintaining negative pressure in the syringe by locking the plunger in a drawn-back position with the use of a hypodermic needle passing through the syringe casing.
Preoperatively, the patient requires adequate clipping and aseptic preparation of skin around the wound and the proposed exit point for the drain.
The drain should be placed following debridement, lavage and haemostasis of the wound.
The drain should not be secured within the wound.
The drain should be fenestrated, as this will increase drainage efficiency and reduce risk of occlusion. Fenestrations should not be more than one third of the circumference of the drain as this may increase the risk of tearing at the time of removal.
A single exit point should, where possible, be positioned at a dependent part of the wound. This will allow residual fluid to drain following the drain’s removal.
The exit point should be adjacent to, but separate from, the wound, but also not too far away, to promote ease of drainage without impeding healing of the primary wound. This will also allow ongoing drainage following drainage implant removal. It may also be necessary to include the drain exit point in a contaminated field requiring further surgery or radiation therapy following oncological resections.
The length of drain used should be recorded and checked on removal.
Secure the drain to the skin at the exit point with a Chinese finger-trap suture with or without tape butterflies sutured to the skin. The drain exit should be covered with a sterile dressing to prevent contamination of the exit wound. (Figures 7 and 8).
The collecting chamber should be secured to the patient but out of its reach. This may be by inclusion within a dressing, or by attachment to an Elizabethan collar.
The suction should not be activated immediately if the wound does not have an airtight seal, as it will suck air into the wound and may lead to contamination. Instead, where possible, wait for four to six hours to allow a fibrin clot to form and seal the wound before activating suction.
The drain should be handled wearing gloves to reduce the risk of contamination when emptying the collection chamber.
Clamps should be used to prevent reflux into the wound during emptying of the collection chamber. These may be haemostats, gate clamps or slide clamps as commonly used with drip tubing.
The chamber should be emptied as often as necessary to maintain negative pressure (when the chamber is half full).
Figures 4 to 6. Different systems of closed suction drains.
Figures 4 to 6. Different systems of closed suction drains.
Figures 4 to 6. Different systems of closed suction drains.
Drain removal
Figure 7. Cover the drain exit with a sterile dressing to prevent contamination of the wound.
A surgical drain should be removed as soon as possible to prevent contamination of the wound and sinus tract formation, but not before fluid accumulation ceases.
Generally, this will take two to five days, but may be longer with heavily traumatised tissue, hygromas or aural haematomas. In a large wound, up to 2ml/kg/day of fluid production may be expected as a result of the inflammatory foreign body reaction to the drain itself.
Penrose drains are removed by cutting the single external simple interrupted suture, then swiftly tugging the drain to release the tube from its internal anchorage point. Closed suction drains are removed by cutting the external Chinese finger-trap and gently sliding the drain from the wound. In either case, the removed drain should be measured and inspected to ensure complete removal.
The exit hole should not be closed, but instead allowed to heal by second intention. The opening may need to be kept clean with saline until it seals.
Complications
Drains may increase the risk of wound contamination. Infection may track along the drain into the wound. This risk is much lower with closed suction drains compared to Penrose drains. Zero per cent and 34% respective contamination rates of the internal tip of the drain have been reported after 24 hours. Infection rates also increase with duration of drainage, and so drains should be removed as early as possible. Drains should not be used to flush the wound, as this will significantly increase the risk of wound contamination.
Figure 8. Cover the drain exit with a sterile dressing to prevent contamination of the wound.
Wound dehiscence may result if the drain is placed directly under the suture line, resulting in a decreased rate of wound healing.
Premature removal of the drain by the patient can be an issue. The number, length and location of drains should be recorded and checked at the time of removal. Drains should also be fixed securely and adequate measures taken to prevent the patient interfering with them.
A further complication may be a longer stay in hospital.
Drains may cause a degree of pain, irritation and elevated temperature, which is known as “drain fever”.
Drains should be placed away from neurovascular structures to prevent trauma to, and erosion through, these structures.
Drainage may fail for a number of reasons, including:
improper placement
inadequate diameter
overfilling of reservoir
loss of negative pressure because of suction system detachment
obstruction of the drain
Drains are a very useful surgical tool to be used appropriately in combination with other techniques to reduce fluid accumulation and closed dead space. They are not a substitute for proper haemostasis, gentle tissue handling and adequate debridement and lavage of the wound.
