Method and Apparatus for Detecting Sepsis Causation in a Catheter

1. FIELD OF THE INVENTION

The present invention relates to a method and an apparatus for detecting whether a catheter is the cause of sepsis in a patient without unnecessarily removing the catheter from a patient.

2. ART BACKGROUND

For a number of years, central venous catheters have been used widely in medicine in the critical care area. These catheters are commonly used to perform a number of different, but equally important functions, among which include (a) measuring central pressure; (b) monitoring and modifying fluid volume; (c) administering one or more therapeutic substances simultaneously; (d) providing a secure site of intravenous ("IV") access; and (e) conducting blood therapy. Furthermore, these catheters also are used in long-term treatment, such as chemotherapy and parenteral nutrition (so called "Hickman catheter").

Venous catheters are inserted into a patient "peripherally" through a cephalic or basilic vein, or "centrally" through the internal jugular, external jugular, subclavian or saphenous vein. Determining which type of insertion is based on many factors; however, any type insertions typically causes at least some discomfort and pain to the patient, and requires a reasonable amount of skill, and each insertion is subject to certain inherent risks and costs. In addition to venous catheters, there are also peritoneal catheters, urethral catheters, such as the Foley catheter, and arterial catheters in the prior art.

According to various studies, approximately 4-15% of the venous catheters are the cause of secondary infections. On the average, in about 60% of the cases in which there is sepsis, the catheter cannot be ruled out as the cause, and the catheter is removed to make a determination if it is the cause, as described in more detail below. Even though only a small percentage of catheters are the cause of such infections, hospitals are required to continuously monitor catheters for possible catheter sepsis (i.e., infections within an indwelling line of a catheter) which may cause complications in a patient's treatment leading to sickness or even death.

The current diagnostic techniques used to detect catheter sepsis are problematic. If a physician or nurse suspects that an infection is being caused by the catheter, the suspect catheter is removed and replaced with a new catheter. The tip of the suspect catheter is removed under sterile conditions and sent to the lab for contamination testing. If the catheter is found to be infected, physicians can provide treatment in accordance with standard medical procedures for such infection.

This procedure, called a "tip culture", offers a number of disadvantages. The primary disadvantage is that since only a small percentage of the catheters become infectious, patients quite often experience additional pain and discomfort due to the unnecessary removal of the catheters. Also, the insertion of a new catheter can be associated with additional risks of infection, such as bleeding, pneumothorax, and infection. Moreover, the removal of non-infected catheters contributes to rising medical costs.

One prior art method of identifying and locating dental microorganisms is disclosed in U.S. Pat. No. 4,368,272 comprising a flexible strip of material with a sterile velvet material that is contacted with the teeth and then cultured.

Another prior art test method and apparatus for testing whether there is any infectious material in the contents in syringe is described in U.S. Pat. No. 4,397,945, which teaches the use of a sampling device for sampling a portion of the contents of the syringe..

Also in the prior art are cytology brushes which are used to collect cells for analysis. It is not believed that such a brush has heretofore been used for a sampling system for microbial infection.

Another prior art method previously developed by the present inventor is described in a publication entitled Markus, Stan and Buday, Stephen, "Culturing Indwelling Central Venous Catheters In Situ," Infections in Surgery, May 1989, pp. 157-160, and a review article Beam, Thomas, "Vascular Access, Catheters and Infections," Infections in Surgery, May 1989, pp. 156; 161-162. The Markus, et al. article teaches a method and apparatus for assessing whether central venous catheters is causing catheter sepsis in situ. The apparatus comprises a thin wire with either a stop or separate handle on or near one end, and a brush at the other end. The apparatus is specifically designed so that it cannot protrude through the end of the catheter. The brush is designed to fit the exact length of the catheter in situ, and a metal stopper ensures that the brush does not go beyond the catheter tip and does not damage the vein wall during sampling. (See FIG. 2 at p. 158).

Thus, there is a need for a better method and apparatus for determining the existence of infections being caused by an indwelling catheter, which method and apparatus do not have the drawbacks of the prior art.

A method and apparatus are disclosed which overcome the disadvantages and limitations associated with prior art tip culture testing techniques used to detect the presence of infections within the indwelling line of the catheter.

It is the object of the present invention to provide a method and an apparatus for detecting whether an infectious microbiological culture is present within an indwelling line of a catheter without removing the catheter from the patient.

It is also an object of the present invention to provide a method and an apparatus which would greatly reduce morbidity caused by an infection within a catheter by allowing physicians and nurses to easily monitor the suspect catheter.

It is a further object of the present invention to provide a cost-efficient method and apparatus for detecting an infection within a catheter without unnecessary removal and subsequent disposal of the catheter.

It is also an object of the present invention to avoid unnecessary pain and discomfort to a patient caused by removing a suspect catheter and replacing it with a new catheter.

These and other objects of the present invention are provided in a method and an apparatus for detecting an infection within a catheter without removing the catheter from the patient. The present invention provides a method for detecting an infection in a catheter comprising the steps of (i) supplying a specimen collection means adapted to fit within the interior of a catheter and collect any infectious microorganisms from the inside as well as the exterior of the end of the catheter; (ii) inserting said specimen collection means into said catheter to collect said microorganisms disposed with the catheter and the outside of the tip of the catheter; (iii) advancing said specimen collection means through said catheter towards the end of said catheter within the vein to a point where a portion of the specimen collection means passes through the end of the catheter and contacts the outer end of the catheter in order to sample the outside of the catheter as well as the inside; (iv) removing said specimen collection means from said catheter under sterile conditions so that a microbial specimen may be obtained on said specimen collection means; and (v) culturing said specimen to determine whether infectious microorganisms are present and identify the same.

The specimen collection means collects fibrin which may be coating inside and outside the tip of the catheter, the fibrin having mixed therein microbes which may then be cultured and identified. The fibrin along with the captured microbial sample can be plated under sterile conditions which are commonly known in the art and the cultures which may grow from the sample can be identified by known microbiological techniques.

Further, in one embodiment, the apparatus comprises a loop handle, and means for collecting said specimen within a catheter. The means for collecting said specimen is preferably a brush made of thin synthetic bristles. The length of the bristles is greater for the bristles at the end of the brush so that they protrude out the end of the catheter to take a sample outside the end of the catheter. The tip of the brush is blunted, rounded or otherwise dulled so that if it contacts the wall of the vein it does not damage the vein wall (or the wall of any other tissue which it may contact if used with other types of catheters.) The handle consists of a twisted wire loop in a manner so that the apparatus is advanced through the catheter a limited amount and prevented from passing through the catheter and beyond the proximal end. This prevents any chance of fragmentation with loss of brush within the catheter or vein.

The present apparatus can be used with a number of diferent types of catheters including indwelling venous catheters, Foley catheters, Hickman catheters, parenteral catheters, arterial catheters and the like.

The objects of the present invention will be described with respect to the following figures in which:

FIG. 1 is an illustration of a central venous catheter in the prior art.

FIG. 2 is a sectioned view of a prior art embodiment of the fibrin sampling device of the prior art.

FIG. 3 is a flowchart illustrating a method for determining the existence of an infection by sampling inside the catheter and outside the tip of a catheter.

FIG. 4 is a more detailed flowchart of the method for testing the existence of an infection by sampling inside the catheter and outside the tip of a catheter.

FIG. 5 is a side view of an alternative embodiment of a microbiological fibrin sampling brush of the present invention.

FIG. 6 is a side view of an alternative embodiment of a microbiological fibrin sampling brush of the present invention.

FIG. 7 is a side view of the embodiment of FIG. 5 and a schematic view of a catheter.

FIG. 8 is a side schematic view of the catheter and brush of FIG. 7, with the brush being inserted into the catheter.

FIG. 9 is a side schematic view of the catheter and brush of FIG. 7, where the brush is fully inserted into the catheter.

FIG. 9a is a left end view of the brush and catheter of FIG. 9.

FIG. 10 is a side schematic view of the catheter and brush of FIG. 7, where the brush is being removed from the catheter.

A method and an apparatus are described which are useful in detecting whether a catheter is causing an infection in a patient. The preferred embodiment of the present invention might best be described as an unique method for detecting an infection within a catheter through use of an apparatus (hereinafter referred to as a "culturing brush"), so that removal of the suspect catheter from a patient is not necessary unless it is determined that the catheter is the cause of the patient's infection. Such method and apparatus eliminates many disadvantages associated with using the conventional tip culture method for testing for infections within an indwelling line of a catheter. It should be borne in mind that the present invention need not be limited in use for central venous catheters, but may find wide application for testing any fluid conveying channel.

FIG. 1 shows an embodiment of a prior art central venous catheter. The catheter comprises a central line/connected to a flexible hub 2. The central line is a tubular structure with an inlet 3 at the proximal end, connected to the flexible hub 2 and at least one outlet 4 located at the distal end 5 of the central line 1. In FIG. 1, there are three outlets labeled 4a, 4b and 4c in which therapeutic fluids are passed through and injected into a patient's vein. A plurality of lumen extension tubes, shown as 5a, 5b and 5c, provide a connection between an intravenous supply 7 and the flexible hub 2 to allow therapeutic fluids to be given to a patient intravenously.

Referring now to FIG. 2, a prior art embodiment of a culturing brush described in the above-referenced Marcus, et al. article is illustrated. The culturing brush 10 has an overall length of 18 centimeters ("cms") with a tolerance of 0.50 cm. The brush tip 12 included a stem 13 and a plurality of bristles 14 and end 11. The stem 13 was a stainless steel wire having a diameter of 0.010 in. The plurality of bristles 14 protrude radially out from the stem 13 to collect the fibrin deposited on an inner surface of an indwelling line of a catheter. Each of the plurality of bristles is made of nylon material, such as Tynex.RTM., or other suitable bristle material, and has a diameter of about 0.005 in.. The overall brush has a diameter of 5 mm.+-.0.5 mm and a length of 13 mm.+-.1 mm. The brush stem 13 extends through a spring sheath 16 and is bonded into a handle 15.

FIG. 5 is the presently preferred embodiment of the present invention comprising a flexible stainless steel twisted wire 20 having a brush 22 on one end and a loop handle 24 made of the untwisted portion of the stainless steel on the other end. The end 21 is blunted or rounded for safety. In this embodiment, the preferred dimensions include the diameter of the wire being 0.038 inches.+-.0.003 inches, the overall length being 12, 14 or 18 inches, depending upon the size of the catheter in which it is used, and the bristles may be 0.003 Tynex, but are preferably 0.0025 inch width nylon. The longer bristle 25 display a 3 mm diameter D, and extend along the length of the brush for about 2 mm. The shorter bristles 26 have a diameter D' of 1.5 mm and extend along the length of the brush for about 6 mm for a total length of brush of about 8 mm. Another way of describing the length of the bristles is that the longer bristles are of sufficient length that their effective diameter (the apparent diameter when viewing the longer bristles from the end) is greater than the diameter of the catheter, or another way, is that the length of any such bristle is longer than the radius of the catheter. The shorter bristles have an effective diameter approximating the inner diameter of the catheter, or another way to describe it, is that the length of the shorter bristles is approximately the inner radius of the catheter.

FIG. 6 is yet another embodiment of the present invention comprising a flexible stainless steel twisted wire 30 having a brush 32 on one end 31, which is rounded, and a stop means 34 made of stainless steel, to stop the brush from passing too far through the catheter. Again, the brush 32 is made up a a longer bristle section 33 and a shorter bristle section 35.

Additional lengths of the device may be required for different lengths of catheters. For a standard indwelling venous catheter, lengths of 15, 20 and 30 cms are required. For a standard Hickman catheter, a length of 36 inches is required. It will be obvious to a person of ordinary skill in the art to modify the length, and adapt the brush diameter to accommodate various catheter sizes as required.

FIG. 3 illustrates procedure for determining whether an infection exists in the indwelling of the central line of the central venous catheter. The first step is to obtain the culturing brush as illustrated in FIGS. 5 or 6 (Step 1). A brush of the proper size must be selected so that the brush can be advanced to, and just through the tip of the catheter. The patient is then prepared and draped, and the physician gloved with sterile gloves. The IV is then disconnected. Next the distal end of the catheter is sterilized. Next, the culturing brush is inserted into the flexible hub of the catheter (Step 2). By applying force to the culturing brush, the brush tip passes through an inlet of the indwelling central line towards the tip of the catheter (Step 3). As a result, the plurality of bristles of the brush tip come into contact with the inner surface of the indwelling line of the catheter. As the brush tip approaches the tip of the catheter, the handle permits the brush tip to just protrude through the tip of the catheter because the diameter of the handle is larger than the diameter of the catheter end. In the embodiments shown in FIGS. 5 and 6, the loop handle 24 and the stop means 34 serve the same purpose at the end of the catheter. Thereafter, the brush is removed from the indwelling line of the catheter (Step 4) bringing with it a sample of fibrin collected on the interior wall of the catheter and the outer tip of the catheter, said fibrin having captured within it a sampling of any microbiological contamination which may exist in the catheter. The brush tip is then cultured by applying the brush to a culture media under sterile conditions (Step 5). Alternatively, the brush is secured in a sterile container and sent to a laboratory for culturing. The IV is then reconnected and restarted.

Referring to FIG. 4, another embodiment of the present invention is illustrated. The first step is to obtain the culturing brush (Step 1). Next, unhook a catheter from an intravenous supply so that the culturing brush can be inserted within said indwelling line with the brush tip inserted first (Step 2). It may be helpful, but is not required, that the line be held in a straight angle in order to lessen the resistance of said culturing brush. The third step is to swab the flexible hub of the catheter with alcohol in order to sterilize the catheter before inserting the brush (Step 3). Thereafter, follow Steps 2-5 as shown in FIG. 3, but before culturing the brush tip, reconnect the catheter to the intravenous supply and restart the intravenous fluids (Steps 4-8).

The method is also demonstrated in FIGS. 7-10. FIG. 7 shows a brush 40 and catheter 42 in generally schematic form. FIG. 8 shows the brush 40 being inserted into the catheter 42 in the direction A depicted by the arrow. It is noted that the larger bristles 44 are folded and the smaller bristles 46 are sized to generally touch the inside surfaces of the catheter. As shown in FIG. 9, the larger bristles 44 are outside the end 48 of the catheter 42, and the handle 49 of the brush 40 is abutting the other end 43 of the catheter, preventing the brush from being pushed further through the catheter. In this position, the larger bristles 44 can sample the outer portion of the end 48 of the catheter 42. As shown in FIG. 10, the brush 40 is then removed from the catheter in direction A', taking with it a sample of fibrin from the outer surface of the end catheter as well as from the inner surface of the catheter. FIG. 9a shows an end view of the catheter and brush of FIG. 9, and particularly, the handle 49, the catheter 42, the larger bristles 44 outside the catheter, and the smaller bristles 46 inside the catheter.

If it is determined that infectious microbes are present in the culture, the catheter can then be removed and replaced, and the microbes can be identified, and the patients treated with the requisite antibiotics or the like. If it is determined that there is no infection, there is no need to remove the catheter, and other sources of the infection can be explored.

The apparatus described herein may be manufactured by many different materials and many different sizes. For example, the device can be manufactured as a single unit or as a plurality of units coupled together. Moreover, it can be made of stainless steel, plastic or any other material which can be sterilized.

While the method and apparatus have been described in terms of various embodiments, other embodiments may come to mind to those skilled in the art without departing from the spirit and scope of the present invention. The invention should, therefore, be measured in terms of the claims which follow.