Hemodialysis is a common treatment for kidney failure, especially when a kidney transplant cannot be performed. During hemodialysis, a patient's blood is removed (a small amount at a time) and circulated through a hemodialysis machine to remove impurities and regulate fluid and chemical balances. The purified blood is then returned to the patient. Blood can be removed from the patient through an access point to the patient's bloodstream. This access point is usually in the patient's arm, and allows blood to be removed and returned quickly, efficiently, and safely during hemodialysis or other procedures requiring frequent access to the patient's bloodstream.
The area within which an access point may be established may be formed by constructing an arteriovenous fistula (AV fistula), which is the surgical connection of an artery to a vein. AV fistulas are commonly used to form areas for access points because once formed, they can be used for years, and are less likely than other methods to produce clots or become infected. When an AV fistula is created, the connection between the artery and the vein increases blood flow through the vein, causing the vein to enlarge and strengthen. This change allows a greater amount of blood to pass through the vein, thereby increasing the efficiency of the hemodialysis, and also facilitates repeated insertions into the vein. The insertion of two needles (one to withdraw blood from the patient and one to return blood to the patient) into the area formed by the AV fistula are typically required for every hemodialysis treatment session. In some cases, a “ladder” methodology is used in which the access point for needle insertion in the AV fistula is gradually and systematically moved up the entire length of the AV fistula to prevent any one area from being weakened by excessive needle sticks in a short period of time.
An alternative approach is the constant site cannulation method in which the same needle insertion site is used for repeated hemodialysis treatment sessions. When a new needle insertion site is first selected, a sharp needle is used at an aseptic site to puncture the skin and vessel. Over time (e.g. after about six cannulations of the same site with a sharp needle), a mature needle insertion site will form with a “tunnel” or “track” of scar tissue. To properly form the mature site, the same needle insertion angle and depth of penetration is generally employed, usually by the same clinician. After a mature needle insertion site has been formed, subsequent site cannulations may be performed using a blunt needle. Prior to performing constant site cannulation with a blunt needle, the cannulation site must be prepared. First, aseptic techniques are utilized to cleanse the cannulation site (e.g. by washing the site with soap and water or an antimicrobial agent, preferably using circular movements). Next, the scab from the previous cannulation must be removed. (It should be understood that after the previous hemodialysis treatment session is completed and the needles are removed, a scab, or crust, will form at the entrance of the site).
Current practice for removing the scabs from constant sites differs widely from country to country and region to region. In the U.S., the scabs on sites are removed with sterile hypodermic needles, sterile or non-sterile devices (such as tweezers), or are scrubbed off with a water and soap solution. However, each of these practices creates potential problems. For example, the use of hypodermic needles carries a risk of damage to tissues surrounding the scab. Also, the use of needles or other devices requires additional sterilization procedures as well as the expense of the devices themselves. Non-sterile devices carry the risk of infection. In addition, the method of scrubbing off residual scabs does not work with all patients and may cause irritation of surrounding tissue. After the scab has been removed and the site is once again disinfected, the blunt needle is removed from its sterile packaging and its cover removed. The blunt needle is then advanced along the established scar tissue tunnel track using a consistent angle and depth of insertion. This technique has been shown to generally reduce the cutting of tissue surrounding the established scar tissue tunnel or track. Other potential advantages of the constant-site cannulation technique using blunt needles include reduced pain, hematoma, infections, thrombosis, infiltrations, and missed needle sticks.
Although the constant-site cannulation technique is believed to be advantageous for reasons such as those mentioned above, Applicant has recognized that removal of the scab in a sterile manner without requiring additional sterilization procedures, while reducing the risk of damage or irritation to tissues surrounding the scab, can be accomplished through the use of a needle cover with a site preparation tip.