Abstract:
A method for employing a pre-assembled drainage catheter assembly for the insertion of a drainage catheter percutaneously. The assembly includes a trocar, a cannula, a catheter stiffener, and a catheter. The drainage catheter assembly is operated between a pre-assembled condition, a first step condition and a second step condition. In the first step insertion the trocar and cannula are inserted into a patient&#39;s body for obtaining a specimen fluid before the catheter is inserted. In the second step the catheter is inserted for collecting fluid.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to catheters, and more particularly to a catheter assembly which facilitates the percutaneous drainage of abnormal fluid collections from the human body in an efficient and relatively non-traumatic manner. The invention is applicable to fluid collections located within the thoracic, abdominal, or pelvic cavities, or within organs of the human body. 
   2. Discussion of the Related Art 
   A drainage catheter is generally a flexible tube with multiple side openings near the distal end, and is widely recognized as an efficient and effective device for removing fluid collections from the human body. Conventional procedures for placing the drainage catheter inside the human body are time-consuming and require the assistance of other devices including a puncture needle, guide wire, and dilator sheath. The puncture needle consists of an outer cannula having an elongated tube and an inner trocar with a sharpened tip projecting through the distal tip of the cannula. 
   In use, the puncture needle is first punctured into the human body to reach the fluid collection. The trocar needle is then removed. A specimen of the fluid is obtained by aspiration through the cannula so that the fluid nature of the collection can be confirmed before the actual drainage procedure. This collection is typically obtained before such specimen has been contaminated by an operating instrument. 
   A guide wire is then positioned to reach the fluid collection through the cannula. Once the guide wire is property positioned, the cannula is removed. A number of dilator sheaths with tapered distal tip ends, one at a time, are then inserted over the guide wire to dilate the stricture until the size of the drainage catheter is reached. The drainage catheter is then inserted over the guide wire to reach the fluid collection. 
   Once the drainage catheter is properly positioned, the drainage catheter is fixed externally onto the skin with a fixation device. Abnormal fluid can be removed by suction or drained or siphoned through the drainage catheter into a collection bag. 
   One disadvantage of this conventional method is that it involves redundant steps of inserting the guide wire and dilator sheaths to dilate the stricture, which can be eliminated by an assembled device specially designed for the drainage of the fluid collections from the human body. 
   A one-step drainage catheter has been designed to simplify the above procedure. The one-step drainage catheter is a device which includes a trocar preloaded within the catheter. The trocar has a sharp distal tip that protrudes out of the catheter. The trocar and the catheter are locked together at the hub, at the proximal end, so that they function as a unit. 
   When the one-step drainage catheter is in use, the combined unit of the trocar and catheter is inserted into the collection cavity. The trocar is then disengaged from the catheter and removed. The catheter remains with its distal end positioned for draining the fluid collection. 
   Although the one-step drainage catheter has greatly simplified the conventional procedure, there are two main disadvantages. First, forceful advancement of the combined unit of the trocar and catheter is required to bring the unit into the human body and to overcome the friction between the body tissue and the catheter tip. The catheter tip is positioned slightly behind the trocar tip, creating an abutment surface on the catheter tip against the body tissue. The abutment surface on the catheter tip is subject to substantial pressure during insertion into the body tissue, which causes great trauma for the patient. 
   Second, no fluid specimen can be obtained by simply applying the one-step drainage catheter, which is a crucial step to ensure that the catheter tip is properly positioned and the abnormal fluid drained. In some circumstances, the one-step drainage catheter is improperly positioned and no fluid can be drained after insertion. The one-step drainage catheter has to be reinserted and the patient has to suffer another puncture. 
   It is also helpful to extract the fluid specimen when the fluid collection is still uncontaminated by any instruments or device. Without the cannula being part of the device, the lumen now being occupied by the trocar, the specimen fluid can only be obtained by a separate needle puncture before the use of the one-step drainage catheter. In that case, the patient will suffer two punctures during the procedure. 
   U.S. Pat. No. 5,205,830 discloses a catheter assembly comprising a catheter, a cannula, and a dilator. According to the &#39;830 patent, the cannula and dilator are preloaded inside the catheter. An introducer needle (also known as a trocar) is first inserted into the cavity to be drained. A guide wire is then inserted into the introducer needle and the introducer needle is removed. The catheter assembly device is then inserted over the guide wire to reach the fluid collection. 
   One disadvantage of the &#39;830 patent is that the catheter is inserted into the human body with the cannula, before the specimen fluid can be obtained. Such insertion will encounter more resistance from the body tissue because of the relatively larger diameter of the catheter. If the catheter assembly is not positioned at the desired body cavity location and does not reach the fluid collection, which can be discovered only after insertion of the catheter assembly, the catheter assembly has to be re-inserted and the patient will suffer another puncture. An alternative is to obtain the fluid specimen by a separate needle puncture before insertion of the catheter assembly as described above, but the patient is still forced to suffer two punctures. 
   Known guide wires are used to guide the insertion of the catheter to reach the drainage system within the organs. A disadvantage is that the guide wire has to be separately held in a relatively stable position during the insertion of the catheter. 
   SUMMARY OF THE INVENTION 
   An embodiment of the present invention provides an easy drainage catheter assembly which comprises a trocar, a cannula, a catheter, and a catheter stiffener for removing abnormal fluid collections from cavities, or within organs of the human body. 
   Another embodiment of the present invention provides an easy drainage catheter assembly which removes abnormal fluid collections from cavities or within organs of the human body in an effective, efficient, and comparatively non-traumatic manner. 
   Another embodiment of the present invention provides an easy drainage catheter assembly which includes means to obtain fluid specimen from the fluid collection before the actual drainage of fluid. 
   Yet another embodiment of the present invention provides an easy drainage catheter assembly of which the easy drainage catheter assembly is inserted into the human body by a two-step approach. The first step being the insertion of the trocar and the cannula together and the second step being the insertion of the catheter stiffener and the catheter together. 
   Still yet another embodiment of the present invention provides an easy drainage catheter assembly which encounters comparatively less resistance from the body tissue during the insertion of the trocar and the catheter. 
   Another embodiment of the present invention provides an easy drainage catheter assembly which minimizes the damage on the body tissue if the first puncture does not reach the desired location and another puncture is required. 
   Yet another embodiment of the present invention provides an easy drainage catheter assembly of which the trocar can detach from the easy drainage catheter assembly after the easy drainage catheter assembly has been inserted into human body. 
   Still yet another embodiment of the present invention provides an easy drainage catheter assembly which consists of a catheter stiffener located between the outer catheter and the inner cannula for enhancing and maintaining the stiffness of the flexible catheter lengthwise during the insertion of the easy drainage catheter assembly into the human body. 
   Another embodiment of the present invention provides an easy drainage catheter assembly which consists of a guide wire with a torque device which can be secured with the cannula as a unit, thus eliminating the need for the operator to separately hold the guide wire during the insertion of the catheter. 
   Another embodiment of the present invention provides an easy drainage catheter assembly of which the catheter and the catheter stiffener as a unit can advance over the cannula to be inserted into the human body. 
   Another embodiment of the present invention provides an easy drainage catheter assembly of which the catheter consists of a tapered distal tip to minimize the resistance and friction encountered at the tip of the catheter during the insertion into body tissue. 
   Another embodiment of the present invention provides an easy drainage catheter assembly of which the catheter stiffener can advance further into the fluid collection beyond the cannula in the body cavity. 
   Yet another embodiment of the present invention provides an easy drainage catheter assembly of which the catheter can advance further into the fluid collection beyond the cannula in the body cavity. 
   Still yet another embodiment of the present invention provides an easy drainage catheter assembly with connectors at the proximal end for locking the various components of the easy drainage catheter assembly into a set unit to be advanced together. 
   Another embodiment of the present invention provides an easy drainage catheter assembly with connectors of different numbers, shapes, or colors of gripper wings to assist the user to distinguish the components of the easy drainage catheter assembly. 
   Yet another embodiment of the present invention provides a simpler, safer, and faster method of placing drainage catheters into the human body for removing abnormal fluid collections from cavities or within organs of human body. 
   An alternative embodiment of the present invention provides a method for assembling an easy drainage catheter, which includes a trocar, a cannula, a catheter stiffener, and a catheter, for removing abnormal fluid collections from cavities or within organs of human body. 
   An alternative embodiment of the present invention provides a simpler, safer, and faster method of placement of an easy drainage catheter assembly into a human body for removing abnormal fluid collections from cavities or within organs of human body. As an example, such a method may include the following: 
   (a) inserting the trocar and the cannula of the pre-assembled easy drainage catheter assembly as one set unit into a human body to reach the fluid collection; 
   (b) detaching and slideably removing the trocar from the easy drainage catheter assembly; 
   (c) removing specimen fluid from the fluid collection through the cannula by aspiration; 
   (d) slideably inserting the catheter and the catheter stiffener along the cannula into a human body to reach the fluid collection; 
   (e) slideably further inserting the catheter into the fluid collection; 
   (f) detaching and slideably removing the catheter and the catheter stiffener from the easy drainage catheter assembly; and 
   (g) fixing the catheter externally onto the skin of the human body. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The above and other aspects, features, and advantages of the present invention will become more apparent upon consideration of the following description of preferred embodiments, taken in conjunction with the accompanying drawing figures, wherein: 
       FIG. 1A  is a side view of an easy drainage catheter assembly assembled in accordance with an embodiment of the present invention; 
       FIG. 1B  is a cross-sectional view of the easy drainage catheter assembly of  FIG. 1A , taken along line  1 B- 1 B; 
       FIG. 1C  is a cross-sectional view of the easy drainage catheter assembly of  FIG. 1A , taken along line  1 C- 1 C; 
       FIG. 2  is a side view of a trocar of the easy drainage catheter assembly in accordance with an embodiment of the present invention; 
       FIG. 3  is a side view of a cannula of the easy drainage catheter assembly in accordance with an embodiment of the present invention; 
       FIG. 4A  is a side view of a catheter stiffener of the easy drainage catheter assembly in accordance with an embodiment of the present invention; 
       FIG. 4B  is a cross-sectional view of the catheter stiffener of  FIG. 4A , taken along line  4 B- 4 B; 
       FIGS. 5A and 5B  are side views of a catheter of the easy drainage catheter assembly in accordance with an embodiment of the present invention; and 
       FIGS. 6 ,  7 A- 7 C, and  8 - 10  illustrate use of the easy drainage catheter assembly in accordance with an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   In the following detailed description, reference is made to the accompanying drawing figures which form a part hereof and which show by way of illustration specific embodiments of the invention. It is to be understood by those of ordinary skill in this technological field that other embodiments may be utilized, and structural, as well as procedural, changes may be made without departing from the scope of the present invention. 
   One embodiment of easy drainage catheter assembly  20  according to the present invention is illustrated in  FIGS. 1A-1C . The easy drainage catheter assembly includes trocar  22 , cannula  24 , catheter stiffener  26 , and catheter  28 . Although described herein as a preferred device and method for removing fluid collections out of the human body, the embodiment may be utilized to perform other functions such as providing drainage to obstructed drainage systems in body organs such as, for example, the biliary system in the liver or urinary system in the kidney. 
   Various components of easy drainage catheter assembly  20  are described below in more detail, and further illustrated in  FIGS. 2 ,  3 ,  4 A,  4 B, and  5 A- 5 C. As shown in  FIG. 2 , trocar  22  includes proximal end  30 , intermediate portion  32 , and distal end  34 . The proximal end is shown attached to conventional male Luer connector  36  for rotatably connecting with the proximal end of cannula  24 . Distal end  34  forms a sharply pointed tip  38  for inserting through body tissue. The trocar may be formed from a sufficiently hard material such as steel, nitinol, metallic alloy, and the like. 
   By way of non-limiting example, trocar  22  has a diameter of approximately 1 mm, and a length of approximately 19 to 32 cm. However, the diameter and length may vary according to the site of the body cavity or organ inside the human body on which the easy drainage catheter assembly is to be applied. 
   As shown in  FIG. 3 , cannula  24  includes proximal end  40 , intermediate portion  42 , and distal end  44 . The proximal end is attached to conventional Luer connector  46 , with male end  48  rotatably connecting with the proximal end of the catheter stiffener  26  and female end  50  receiving the male Luer connector  36  of trocar  22 . The length of the cannula extending from proximal end  40  to distal end  44  is sized to receive intermediate portion  32  of the trocar  22  such that tip  38  of the trocar extends as shown in  FIG. 1A , for instance, 1-3 mm beyond distal end  44  of the cannula  24 . The central lumen (not shown) of the cannula is appropriately sized to slideably receive the trocar and is preferably about 1 mm in diameter, but may vary depending on the size of the trocar. As described further below, cannula  24  provides a mechanism for catheter stiffener  26  and catheter  28  to slideably insert over when entering into the human body, and also permits obtaining a fluid specimen from the fluid collection by aspiration. The cannula may be made of a hard material such as steel, nitinol, or metallic alloy, among others. 
   By way of non-limiting example, cannula  24  has a length of approximately 19-32 cm. However, the length of the cannula may vary according to the site of the body cavity or organ inside the human body on which the easy drainage catheter assembly is to be applied. 
   As shown in  FIGS. 4A and 4B , catheter stiffener  26  includes proximal end  52 , intermediate portion  54 , and distal end  56 . The proximal end is attached to a conventional Luer connector  58  with male end  60  rotatably connecting with the proximal end of catheter  28 , and female end  62  receiving male end  48  of Luer connector  46  of cannula  24 . Catheter stiffener  26  extends from proximal end  52  to distal end  56 , and the outer diameter is sized to fill up the lumen of catheter  28 , which will be further illustrated below. By way of non-limiting example, the outer diameter of the catheter stiffener is about 1.5-2.5 mm, but may vary depending on the size of the catheter. 
   The length of catheter stiffener  26  covers a proximal portion of cannula  24 , and typically remains outside the human body when trocar  22  is inserted into the body cavity. The length of the distal portion of the cannula not covered by catheter stiffener  26  varies, for instance, from 7-13 cm, depending on the site of the fluid collection. Distal end  56  of the catheter stiffener may be tapered to match with the tapered distal end of the catheter. 
   The central lumen (not shown) of catheter stiffener  26  is appropriately sized to slideably receive cannula  24  and includes a diameter of about 1.5 mm or less, but may vary with the size of the cannula. The catheter stiffener may be formed from a stiff material such as, for example, nylon, polyester, or silicon. 
   By way of non-limiting example, the catheter stiffener may have a length of approximately 13-19 cm. However, the length may vary according to the site of the body cavity or organ inside the human body on which the easy drainage catheter assembly is applied. 
   As shown in  FIGS. 5A and 5B , catheter  28  includes proximal end  64 , intermediate portion  66 , and distal end  68 . The proximal end is attached to a conventional female Luer connector  70  and receives male end  60  of Luer connector  58  of the catheter stiffener. Catheter  28  extends from proximal end  64  to distal end  68 . The diameter of the central lumen (not shown) of the catheter is appropriately sized to slideably receive the catheter stiffener. Distal end  68  forms tapered tip  72 , which reduces resistance encountered when entering body tissue, thereby making it easier to insert over the cannula into the body tissue. 
   A plurality of longitudinally spaced ports or openings  74  are formed in intermediate portion  66 , proximal to tapered distal tip  72 , and at axially spaced locations. Each opening directly communicates with the central lumen of the catheter for the drainage of fluid. Radiopaque markings may be formed along intermediate portion  66  at predetermined locations. These marking assist in fluoroscopically determining the positioning of the catheter. 
   Catheter  28  may be formed from soft pliable material such as polyurethane. To enhance and maintain the stiffness of intermediate portion  66  during insertion over cannula  24  into the human body, and to prevent the soft material of catheter  28  from bunching up, intermediate portion  54  of catheter stiffener  26  extends lengthwise to fill up the space between catheter  28  and cannula  24 . Note that intermediate portion  54  of the catheter stiffener includes an outer diameter that is approximately sized to slideably insert into the central lumen of catheter  28 . Stiffening catheter  28  eliminates the tendency of the soft material to bunch up, which would make it difficult for the catheter to be inserted into body tissue and cause trauma to the patient. 
   By way of non-limiting example, catheter  28  has a diameter of 2-4 mm, and a length of approximately 13-19 cm. However, the diameter may vary with the body cavity or organ to which the easy drainage catheter assembly is applied, and the length may vary according to the site of the body cavity or organ inside the human body. 
     FIG. 1A  shows the pre-assembled easy drainage catheter assembly  20  ready for insertion as a unit. Trocar  22 , cannula  24 , catheter stiffener  26 , and catheter  28  are coupled together by the Luer connectors located at the proximal end of the assembly. 
     FIGS. 6 ,  7 A- 7 C, and  8 - 10  illustrate a procedure using the easy drainage catheter assembly  20  to drain body fluid from a body cavity. As shown in  FIG. 6 , a first step is to insert the distal portion of trocar  22  and cannula  24  into the body cavity or the drainage system of the organ to be drained. Catheter stiffener  26  and catheter  28  remain outside the human body. 
   As shown in  FIG. 7A , trocar  22  is then detached from cannula  24  by disengaging male Luer connector  36  of the trocar and female end  50  of Luer connector  46  of the cannula, and slideably retrieving trocar  22  out of the lumen of cannula  24 . A specimen may then be obtained from the fluid collection in the body cavity by aspiration through the lumen of cannula  24 . This step is to ensure that the cannula has been inserted into the desired location. Otherwise, the previous steps may be repeated. In that case, catheter stiffener  26  and catheter  28  have not yet been inserted into the body tissue, which saves the body tissue from being further torn apart by the catheter stiffener and the catheter of larger diameter. 
   If fluid collection is within the organ, conventional guide wire  78  may be slideably inserted through the lumen of cannula  24  and into the drainage system within the organ, such as that shown in  FIG. 7B . The guide wire often contains curved tip  80 , which is useful for moving through curved regions of an organ duct. 
   As shown in  FIG. 7B , conventional torque device  82  is secured on guide wire  78 , outside the human body. The torque device is useful for rotating the guide wire and turning curved tip  80 , which enables the guide wire to enter the desired duct at cross sections of multiple ducts. Torque device  82  may be secured along guide wire  78  at a convenient position for the operator to control the guide wire. According to an embodiment, the torque device may include male Luer connector  84  for securing with female end  50  of Luer connector  46  of the cannula. As shown in  FIG. 7C , the operator can therefore hold cannula  24  and guide wire  78  together in a stable position by holding one device. The operator is not required to handle these two devices separately during the insertion of catheter  28 . Guide wire  78  acts as a guiding agent to facilitate the insertion of catheter  28 , which will be described below. 
   As shown in  FIG. 8 , female end  62  of the Luer connector of catheter stiffener  26  is then disengaged from male end  48  of the cannula. Catheter  28  and catheter stiffener  26  are then inserted as a unit into the body cavity over cannula  24 . Distal end  56  of the catheter stiffener may extend distally beyond distal end  44  of the cannula to support catheter  28  if the catheter is to be further inserted to reach the fluid collection in the body cavity. As catheter stiffener  26  is made of a relatively stiff material, it typically does not extend more than 0.5 mm from cannula distal end  44 . The catheter stiffener may be covered with an extended length of catheter  28 , when it is advanced within the body, to prevent the catheter stiffener from accidentally damaging the soft tissue of the body cavity. 
   As shown in  FIGS. 7C and 9 , female Luer connector  70  of the catheter is disengaged from male end  60  of the stiffener. Intermediate portion  66  of the catheter is inserted beyond distal end  56  of catheter stiffener  26  to reach into the fluid collection, thus permitting openings  74  to contact the fluid collection. 
   If fluid collection is present within the organ, intermediate portion  66  may be further inserted over guide wire  78 , and into the drainage system within the organ. As described above and shown in  FIG. 7C , the locking of guide wire  78  and cannula  24  by torque device  82  frees the operator from holding the guide wire during the insertion of the catheter. The operator holds the cannula in a stable position and controls the insertion of the catheter, without separately holding the guide wire in place. 
   As shown in  FIG. 10 , cannula  24 , guide wire  78  if used, and catheter stiffener  26  are slideably retrieved from catheter  28 . Intermediate portion  66  of the catheter is fixed externally onto the skin surface with a fixation device or stitches. Finally, female Luer connector  70  is connected to a suction device or a connection tube of a drainage bag for the drainage of the abnormal fluid. 
   As shown in  FIG. 1A , each Luer connector may include gripper wings  99  to make it easier for the operator to connect or disconnect the Luer connectors from each other. Each Luer connector may have a different number, shape, or color of gripper wings so that the operator can distinguish the various components of the easy drainage catheter assembly. By way of non-limiting example, the female Luer connector of catheter  70  contains two gripper wings, the Luer connector of catheter stiffener  58  contains three gripper wings, the Luer connector of cannula  46  contains four gripper wings; the male Luer connector of trocar  36  contains five gripper wings, and torque device  82  contains six gripper wings. 
   The present invention provides a unique, simplified approach for placement of a drainage catheter. Time-consuming and redundant steps utilized in conventional procedures, such as the repeated insertion of dilator sheaths, are eliminated. 
   The insertion step of the trocar and cannula may be separated from the insertion step of the catheter so that the device will encounter less resistance when entering into the human body. The present invention also reduces the likelihood of mis-positioning the drainage catheter since the specimen of the fluid collection can be obtained before the actual drainage. Such step is taken without the catheter being inserted into the body tissue, which would further tear off the body tissue. This two-step approach therefore eliminates unnecessary insertion of the catheter when the trocar is found mis-positioned upon testing of the fluid specimen. The patient need not suffer trauma encountered when the catheter is unnecessarily inserted into the body tissue. 
   While the invention has been described in detail with reference to disclosed embodiments, various modifications within the scope of the invention will be apparent to those of ordinary skill in this technological field. It is to be appreciated that features described with respect to one embodiment typically may be applied to other embodiments. Therefore, the invention properly is to be construed only with reference to the claims.