Abstract:
The invention relates to a microcatheter set with a minimized dead space which has a medicine application and flushing device especially suitable for intensive paediatric-neonatologial medicine. It makes it possible not only to apply infusion therapy via a microcatheter inserted into a large body vein but also to administer drugs repeatedly without any danger via the medicine application and flushing device integrated within the set, even with highly pharmacologically effective additives to the general infusion solution, and/or to do away with partial and total catheter shut-offs. This thus excludes additional stress on and risk for the patient by the repeated application of peripheral infusions or the use of surgically inserted double-lumen central catheters for the intravenous administration of drugs.

Description:
BACKGROUND OF THE INVENTION 
     The invention refers to a microcatheter set in particular an epicutaneo cava microcatheter set, consisting of a microcatheter, an easy-lock catheter connection device with a hose and a standard Luer lock connector. 
     Above all in the field of neonatology, for the treatment of very undeveloped premature babies who cannot yet be fed orally with milk, it is necessary for modern intensive medical care that there exists the possibility of parenteral alimentation with high-percentage nutrient-rich infusion solutions which, however, can only be applied centrally by means of catheters through venous blood vessels of a wide lumen. A catheter technique which has proved a success in particular in the field of neonatology is the one according to Shaw which uses epicutaneo cava microcatheters. Respective catheters are available on the market in a set. Here the different infusion solutions are usually infused by means of accurately metering injection pumps via distributors and adapters through the connected microcatheter into a large central body vein. 
     However, in this connection, the following unsolved clinical/pharmacological problems occur: The microcatheter set consisting of a Luer lock adapter, connecting hose, easy lock catheter connection, and a microcatheter, has, as a whole, a dead space volume which is too large. And, in particular when highly effective pharmacological preparations with cardiovascular action (e.g. catecholamine) are added to the infusion fluid --which happens quite often in practice --this means, however, that when, for example, a partially or completely obstructed catheter is flushed or when drugs are administered, that the said large dead space fluid volume with pharmacological preparations influencing the circulatory system will get into the blood stream as a bolus within a very short time. Possible results thereof are severe circulation sensations which, in the case of small premature babies, are possibly followed by life-threatening cerebral hemorrhages. Thus, due to the aforesaid reasons, in the case of partial or complete obstructions, the microcatheters may only be flushed if infusion solutions are used which, pharmacologically, are as indifferent as possible. The same also applies to the administration of medicine. This means in practice, however, that a second access to a vein of the patient has to be created which means discomfort for the patient and the attending physician, in particular in the case of small premature babies and new-born babies. The same is also true for another alternative, namely the use of central double-lumen vein catheters. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to further develop a microcatheter set according to in particular an epicutaneo cava microcatheter, an easy-lock catheter connection device with a hose and a standard Luer lock connector such that the above-cited clinical problems can be solved. 
     Said object is solved by means of a microcatheter set of the generic type which shows the characterizing features of Luer lock connectors with a minimized dead space, micro-lumen hoses and an easy-lock catheter connection with a minimized dead space being used for the general reduction of the dead space of the microcatheter set, and adjacent to the patient and the catheter and closely to and in front of the easy-lock catheter connection with a small dead space, a flushing and medicine application device being additionally arranged. 
     Further advantageous aspects of the inventive solution result from the description herein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further details and advantages of the invention will be explained in detail by means of an embodiment illustrated in the drawings, wherein 
     FIG. 1 is a perspective view of a microcatheter set according to the invention, 
     FIG. 2 is a longitudinal section through a microcatheter with inserted tubule, and 
     FIG. 3 an embodiment of an easy-lock catheter connection device according to the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows in a perspective view the disposable sterile epicutaneo cava microcatheter set with a minimized dead space in an assembled state. It consists of a female standard Luer lock adapter 1 designed so that it has a small dead space and made of transparent plastics material, which has a tapering cylindrical cavity 2 for receiving the cone of a male standard Luer lock connector. Said cavity 2 has only such a depth that commercially available male Luer lock cones of slightly varying lengths can only just be locked in a safe and fluid-tight manner. Thereby the dead space forming between the cone end and the bottom of the cylindrical cavity 2 can be reduced to a minimum of 25 to 50 μl. From said bottom of the cylindrical cavity a small-lumen and thick-walled but, nevertheless, flexible transparent plastics hose 3 (inner diameter: 0.5 mm ; length: 100 through 200 mm) leads to a cuboid quadruple connecting piece 5 of transparent synthetic resin. Within the quadruple connecting piece 5 there are provided bores crossing each other at right angles. At one end of two opposing ends thereof the end 4 of hose 3 is inserted, and at the other end thereof a narrow-lumen short connecting hose piece 6 is inserted which belongs to the easy lock connection which is formed by screwing-together two parts 17, 18 and is associated with microcatheter 19. With one side of the horizontally extending bore of the quadruple connecting piece, a small narrow-lumen connecting hose 7 is connected at which a female Luer lock connector 8 with small dead space is attached, upon which a disposable syringe 9 is placed, and on the other side thereof a corresponding connecting hose 13 with connector 14 is attached. 
     From FIG. 1 it can be inferred that the male Luer lock cones 10 of the disposable syringe 9 or of the Luer lock plug 15 locked by rotating it, which are inserted into the female Luer lock connectors 8 or 14 having a small dead space, do not completely fill these up and therefore allow the creation of a dead space 12 or 16 of slightly differing size, in which the connecting hoses 7 or 13 end up. 
     FIG. 2 is a longitudinal section through a microcatheter 19 having a ring marking 20 and longitudinal markings 32. The microcatheter 19 can b e made of a soft silicone rubber or polyurethane with radiographic properties. The microcatheter 19 is slipped under pressure over a tubule made of stainless steel 21, wherein the front fifth part 22 of the tubule with respect to the total length is left free. Said front part is used for pushing it into the easy lock connector 17, 18. 
     FIG. 3 shows a longitudinal section through the easy lock catheter connection in the mounted state. Connecting hose 6 is inserted into part 17 of the easy lock connector. In its narrow lumen 26 there is located the front part 22 of the stainless steel tubule 21. At its lower end, part 17 of the easy lock connection has a threaded connecting piece 23 which, centrally, has a wide guiding channel 29 for the microcatheter 19 slipped over the stainless steel tubule, which continues in an insertion funnel 27 which finally terminates in the lumen of the connecting hose 6. As the microcatheter 19 is pressed into said insertion funnel 27 during the screwing-together of the connector 17, 18, it forms a sealing bead 28 therein. The lower part 18 of the easy lock connector represents a tapped bush made of synthetic resin which tapers in the downward direction and receives a conical rubber plug 24 with a central bore 25 in said part. Into said central bore 25, the microcatheter is inserted with its part 21 to such a degree that its ring marking 20 is still visible at the edge of the lower opening of part 18. 
     The function of the microcatheter set in operation can be described by means of FIGS. 1 through 3 as follows. The sterile microcatheter set with integrated flushing and medicine application device is connected with its female Luer lock connector 1 with reduced dead space to a syringe pump infusion system with a male Luer lock connecter (not shown). As already described, after the locking of female and male connectors a remaining dead space volume is always created which depends on the accuracy of fit of the male connector cone and amounts to approximately 25 through 50 μl. The attached narrow-lumen connecting hose 3 (with an inner diameter of 0.5 mm) adds further 38 μl, the quadruple connecting piece 5 adds further 7 μl, the connecting hose 6 adds further 4 μl, and, finally, the easy lock connector 17, 18 with its minimized dead space adds further 5 μl. The result is a total dead space volume of approximately 54 μl. In this case, depending on the length and the inner diameter of the microcatheter, a further dead space volume must be added thereto which is caused by said microcatheter. When the used microcatheter has, for example, a length of 150 mm, then 10.5 μl of volume must be added. When, for instance, a partially obstructed microcatheter is flushed free, within a very short time a total of approximately 90 through 120 μl of infusion liquid with possibly added highly effective pharmacological preparations from the dead space volume will be supplied to the patient, which can result in life-threatening overdoses. In comparison thereto, in the microcatheter sets available today in which all the mentioned special measures for reducing the dead space volume are not implemented, at least 240 μl of dead space volume has to be expected. 
     In order to avoid said mentioned large dead space volumes which, from the clinical aspect, substantially do not only forbid a flushing of the catheter set, but also any drug application, the quadruple connecting piece 5 has been inserted in the microcatheter set according to the invention adjacent to the patient and the catheter for flushing and medicine application, as can be seen in FIG. 1. If the microcatheter 19 is, for instance, to be flushed free or, which is also very often desired, is used for the administration of drugs, this can be performed in the following manner without any risk to the patient (see FIG. 1). 
     From the female Luer lock connector 8 the Luer lock plug (not shown) is removed and, instead thereof, e.g. a disposable 2 ml syringe 9 filled with physiological saline solution is placed thereupon. Now two sliding hose clamps 30, 31 provided at the hoses 3 and 6 are closed and the Luer lock plug 15, which is closed by turning it, is loosened, and, thus, the Luer connector 14 is opened. First the dead space 12 is filled with the infusion liquid, i.e. approximately 25 through 50 μl, then the connecting hose 7, i.e. approximately 7 μl, a part of the horizontal bore in the distributor 5, i.e. approximately 7 μl, the connecting hose 13, i.e. approximately 7 μl, and the dead space 16 of the Luer connector 14, i.e. 25 through 50 μl. That means finally approximately 75 through 175 μl dead space volume liquid, are flushed by means of the syringe 9 with the physiological saline solution. 
     When now the Luer lock plug is again locked and the sliding hose clamp 31 is opened, then the flushing or the desired medicine administration can be carried out slowly and continuously via the microcatheter 19 through the Luer connector 8 in one or several minutes, at best by means of an infusion syringe pump now connected therewith. In this case, the dead space volume filled with infusion solution of now 19 μl results from the dead space volume of the used microcatheter with a length of 150 mm with 10.5 μl, of the easy lock connector with 5 μl and of the connecting hose 6 with 3.5 μl (see FIG. 1). 
     When, for instance, an infusion rate of 1 ml per hour is set for the first one or two minutes after the start of the infusion at the infusion syringe pump connected with the connector 8, then, in practice, catheter medicine applications and flushings can be carried out even where the smallest premature babies are concerned without any risk to the patient. Here, now only 19 μl of infusion solution will be administered into the vascular system of the patient even in a protracted manner within said period. 
     If the general infusion therapy is to be continued after the administering of medicine or after flushing, then the drug infusion pump can be disconnected from the Luer lock connector 8 which then can be closed by a Luer lock plug which corresponds to plug 15. Subsequently thereto, the sliding hose clamp 30 is opened and thereby the infusion flow via the Luer lock adapter 1 and the connecting hose 3 is again set free.