The present invention relates to an improved dressing for use with percutaneous devices or catheters and more particularly with long term or other vascular access catheters, such as hemodialysis catheters. In a preferred form of the present invention, the dressing includes a portion thereof which extends into the catheter tract a short distance along the shaft of the catheter. The present invention may also include various layers, such as, a thin film or a mesh layer along the surface of the dressing which is adjacent to the skin of the patient.
The use of percutaneous devices, including long term or vascular access catheters has steadily increased in recent years. For example, various right atrial catheters or medication ports may be surgically placed in the patient and are intended to remain in the patient indefinitely. This use of relatively long term catheters or access devices may eliminate or minimize the need for multiple punctures of the blood vessels of the patient to obtain blood samples or to administer medications by providing prolonged access to the blood vessels of the patient. With these types of catheters, medical personnel are provided with convenient access to the blood vessels of the patient without concern for rotating IV sites or frequently reestablishing large vein access.
The increased use of the longer term catheters has also brought difficulties not typically encountered. Infections or various forms of skin irritation around the catheter or access site have now become a more common occurrence. The dressings used with short term catheters are typically either gauze and tape or transparent film dressings, depending on the preference of the clinician and/or the patient. With the shorter term catheters, infections are usually not a major concern because the catheter is in place for a relatively short period of time and it is not necessary to repeatedly change the dressing. Despite this, the occurrence of exit site infections, catheter tract infections and septicemia has been reported. The most common occurrence encountered with these dressings are an allergic reaction to the material or adhesive.
The area where the catheter or other percutaneous device enters or exits the skin of the patient is known as the exit site and is particularly sensitive to infections or irritation because it is essentially an open wound. As used herein, exit site is intended to refer to the area along the skin of the patient which is adjacent to the percutaneous device. The area beneath the skin of the patient along the shaft of the catheter or other percutaneous device is referred to herein as the catheter tract. Many of the currently available dressings are used to protect the patient from infections at the exit site and in the catheter tract by providing a physical barrier which prevents the infiltration of bacteria, debris or detritus into the body of the patient.
Under normal conditions, the inflammatory phase of the wound healing response will remove the cellular detritus or exudate and bacteria from the catheter tract or exit site. It is believed that the presence of the bacteria in the catheter tract or exit site in addition to the detritus or exudate may be a cause of exit site or catheter tract infections. Over an extended period of time, cellular turnover in the catheter tract may result in a buildup of cellular detritus or exudate along the shaft of the catheter or along a cuff on the catheter as described more fully below. The detritus is usually removed by phagocytic cells as part of the overall inflammatory response around an implanted device unless the rate of detritus or exudate formation exceeds the capacity for removal by the phagocytic cells. The detritus or exudate may also accumulate within small pores in the cuff which may be inaccessible to the phagocytic cells. If bacteria is also present in the cuff, an infection may then develop in the catheter tract. Additionally, the movement of the shaft of the catheter in the catheter tract caused by normal movement of the patient or dressing changes and also the initial tunneling or incision which is used for the original catheter placement may similarly increase the presence of detritus and bacteria in the catheter tract. Furthermore, the phagocytic activity of the phagocytic cells in immunocompromised patients, such as hemodialysis or chemotherapy patients, is significantly reduced. Therefore, because of the increased presence of detritus and bacteria in the catheter tract of the same patients that typically use longer term catheters, the normal reparative phase of wound repair either takes longer than in normal situations or does not occur at all.
Another factor which potentially contributes to the increasing incidence of catheter tract infections is the fact that many dressings must be changed at least daily or on a regular basis. The increased handling of the catheter during each dressing change may increase the movement of the catheter in the catheter tract. Additionally, the skin of the patient around the exit site is irritated because of the adhesives or other materials which are used to clean the skin and adhere the dressing to the skin of the patient.
One approach that is commonly used to reduce the likelihood of catheter tract infections is to use a cuff which is constructed of a felt or similar material on the portion of the catheter which is placed subcutaneously. These cuffs typically include a material which is designed to allow tissue ingrowth into the cuff to form a physical barrier which inhibits migration of bacteria along the catheter tract below the cuff. It is believed that the effectiveness of various cuffs may be adversely affected by the amount of debris or bacteria which works its way down the catheter tract from the exit site. Although studies have shown that the use of cuffs may decrease the likelihood of catheter tract infections during the use of longer term catheters, the tissue surrounding the catheter tract and the cuff requires a debris and bacteria free area for the optimal functioning of the cuff so that the tissue is able to satisfactorily grow into or infiltrate the cuff.
One current approach to reducing the incidence of exit site or catheter tract infections is for newly implanted or injured catheter exit sites to be wrapped with a square cotton gauze pad and the catheter and gauze pad are then sandwiched between two semipermeable polyurethane transparent films. The advantage in using a transparent film in this type of arrangement is that the film stabilizes the catheter, conforms easily to the skin and forms a physical bacterial barrier on the skin of the patient. The gauze in this type of dressing arrangement absorbs the exudate from the exit site. A disadvantage of this arrangement is that it is time consuming to apply the dressing to the patient and the transparent film is typically one-way permeable so that the skin of the patient remains dry while moisture is allowed to evaporate. This may increase the scarring along the exit site. Furthermore, this type of dressing does not remove cellular debris or bacteria in the exit site or along the catheter tract and the bacteria or tissue debris may build up along the shaft of the catheter or along a felt-type cuff as described below.
More recently, a number of studies have been performed using hydrocolloid dressings in an effort to improve exit site care and reduce the skin irritation which may occur with various other types of dressings. The hydrocolloid dressings include moisture reactive particles embedded in a polymer base. The moisture reactive particles are believed to react with the wound exudate and form a soft gel over the wound to actively remove bacteria and wound exudate from the exit site or catheter tract while protecting the newly formed tissue during the removal of the dressing. The idea of using hydrocolloid dressings is particularly attractive with longer term catheters because the hydrocolloid material provides a moist wound healing environment which encourages faster healing and less scarring around the exit site. Additionally, the hydrocolloid material forms a physical barrier on the skin to block the migration of bacteria into the catheter tract. The hydrocolloid material also creates a slightly acidic environment underneath the dressing which inhibits microbial growth.
Although the hydrocolloid type dressings have been shown to form an effective bacterial barrier on the skin of the patient, this type of dressing has a tendency to "melt" onto the skin of the patient as the wound exudate or other moisture is absorbed by the dressing. When the user attempts to remove the dressing from the exit site, some of the melted hydrocolloid material may continue to adhere to the exit site and the shaft of the catheter. This is considered to be undesirable because of the extra time necessary for the clinician to remove the hydrocolloid material that adheres to the exit site, catheter tract and the shaft of the catheter after the dressing is removed as well as the resulting damage caused to the newly formed epithelium by removal of the hydrocolloid material therefrom. Therefore, even though the hydrocolloid dressings provide an acceptable barrier and also promote healing of the wound, the need to remove portions of the hydrocolloid material after the dressing has been removed from the skin of the patient has limited the acceptance of this type of dressing for use with longer term catheters or similar devices.
Therefore, there is a need for a dressing which will inhibit or reduce the incidence of infections at the exit site and along the catheter tract so that the likelihood that the tissue will grow into the cuff is maximized.
There is a further need for a dressing that will easily fit around the catheter and which will protect and conform to the exit site. Additionally, a preferred form of the dressing of the present invention includes a portion thereof which extends into the catheter tract and assists in the removal of bacteria and debris therefrom while forming a physical barrier along a portion of the catheter shaft.