Drains are often used to help treatment of infected wounds, but they can also be very helpful after excision of large skin or subcutaneous masses. This is not a new idea; early surgeons, during the 19th century, thought of using glass tubes to drain infected wounds.
Indications for drain placement include reduction of dead space and prevention or reduction of fluid collection. This in turn decreases the risk of infection, since inflammatory fluid, necrotic tissues and blood are excellent culture media. Respecting some basic guidelines will help speed up the healing process.
There are two main types of drains: passive and active.
Passive latex drains are most often Penrose drains, although a sterile piece of IV tubing or a red rubber catheter can be used in a pinch. Fluids leak along the outer surface of the drain, so cutting fenestrations into it actually reduces its efficacy and makes the drain more likely to tear.
Passive drains rely on gravity and therefore must exit ventrally. Letting a drain exit through a dorsal incision defeats its purpose. Moreover, it creates a second opening through which bacteria can enter and cause an infection.
It is, however, a great idea to suture the drain dorsally to prevent its slippage, -usually in a blind fashion. The dorsal end of the drain can be held at the tip of a long pair of hemostats. By applying outward pressure, the skin is tented, and a suture is passed through the drain. Leaving the ends of the suture 2-3 cm long will make it easier to identify it at the time of removal.
A wide, ventral skin incision is created to allow ample fluid drainage. The extremity is secured with a loose, simple interrupted suture. A potentially embarrassing complication could occur if the Penrose drain is caught by the needle while subcutaneous sutures are placed. The only way to remove the drain would be to reopen the wound to find and release the culprit.
Penrose drains are inexpensive (less than $1) and come in various diameters (3/8, 1/4, 1/2 inch). By the way, the Penrose drain was named after an American gynecologist, Charles Bingham Penrose (1862-1925).
|A Penrose drain is placed in a bite wound in the neck of a 2-year-old male Beagle mix. It is sutured dorsally, and exits ventrally. (Courtesy of Dr. Zeltzman)|
A drain reduces the number of bacteria needed to cause an infection by a factor of 10,000. In addition, it is very important to plan a Penrose drain placement so that the ventral end will be covered by a sterile bandage.
Should an ascending infection occur, bacteria are often multi-resistant to antibiotics and aggressive. After the exit wound of the drain is gently cleaned, the bandage is changed aseptically as often as needed, depending on the amount of drainage. Some areas are notoriously difficult to bandage, such as the inguinal area in a male dog. In such cases, in may be preferable to use an active drain.
The most common type of active, or closed, suction drain is the Jackson-Pratt drain. It comes with a fenestrated silicone drain and a lemon-shaped container. This reservoir is sometimes poetically called a “grenade.” The distal end of the drain can be cut so that, once it is placed in the wound, no holes are present outside the patient.
The drain exits through a stab incision in the skin with the metal trocar provided. It is secured to the skin with a purse-string and a Chinese-finger trap, and attached to the clear container. Where the drain exits is not as important as with a passive drain since an active drain doesn’t rely on gravity.
In other words, an active drain could exit dorsally to the wound. Air is squeezed out of the grenade, which is then closed with the cap provided. The negative pressure generated will pull fluids into the container. When it is about half-way full, the pressure gradient is reduced. In order to maintain continuous negative pressure, the fluid must be emptied, air is squeezed out, and the drain becomes active again.
This can be done at the hospital, or can be shown to an adventurous and compliant owner to do at home. Either way, the amount of fluid is recorded in a dated log. When drainage subsides, the drain can be removed.
10 tips for Placing a Penrose:
1. Place aseptically (clip and scrub skin)
Since the full container can become quite heavy, small pieces of tape can be placed around the catheter. In turn, the tape can be sutured to the skin. Alternatively, the grenade can be attached to a collar or a harness.
Active drains are often preferred in large, highly-exudative wounds or after excision of large skin masses. Even though the active drain is more costly (around $25), quite a bit of money can be saved in bandage material as few if any bandages are required.
Alternatively, cheaper, home-made drain systems can be made. One concept involves partially fenestrated IV tubing connected to a three-way stop-cock ($1) and a large syringe. Negative pressure is established by pulling on the plunger, and maintained by holding it in place with a large injection needle or a safety pin placed through a pre-drilled hole.
Another system can be used for very small wounds: After cutting off the syringe adapter, the needle of a partially fenestrated butterfly catheter is placed in a blood-collection tube. Negative pressure is exerted by the vacuum inside the tube. Once the tube is full, it is simply discarded and replaced.
Whichever type you choose, it is important to follow a few guidelines:
- Place a drain in an aseptic fashion; the hair is clipped and the skin (not the wound) is scrubbed.
- A drain should not be placed just under the suture line in order to allow normal healing.
- Drain placement is from the wound to the outside. This is facilitated by clamping the end of the drain with a long hemostat, and creating a tunnel until the exit point is chosen. That point is at least 1 cm away from the suture line.
- After drain removal, the exit wound is left open, as it will heal by second intention within a few days. If some drainage continues, a bandage can be applied, but it should never be sutured closed.
- To prevent premature removal and the always-annoying missing piece of drain inside the wound, it is wise to place an Elizabethan collar or similar device on the patient. If a patient does chew a drain, it is helpful to remember that most drains are radio opaque.
The exact time of drain removal is variable. A drain acts as a foreign body, which will generate some inflammatory fluid. When the drainage becomes sero-sanguineous, or the amount of drainage decreases significantly or seems to stabilize, the drain can be removed. Drain removal can typically done within two to five days. But rather than relying on a magic number of days, the clinician should make an informed decision as to when to remove a drain.
Next time you remove a large skin mass, consider using a drain. Used properly, a drain is an easy, affordable and effective way to speed up the healing process. Use it to your patient’s advantage. <HOME>
Phil Zeltzman, DVM, Dipl. ACVS, is a small-animal, board-certified surgeon at Valley Central Veterinary Referral Center in Whitehall, Pa. His website is www.DrPhilZeltzman.com.