Catheter

Abstract

The invention relates to a catheter with an elongated catheter shaft, wherein the catheter shaft consists of a hydrogel or is provided with a layer of a hydrogel, wherein the hydrogel is designed to expand and / or contract under the action of at least one stimulus, whereby the catheter shaft can be transferred between a first state and a second state under the action of the at least one stimulus, wherein in the first state the hydrogel is contracted and the catheter shaft has a first outer diameter, and wherein in the second state the hydrogel is expanded and the catheter shaft has a larger second outer diameter.

Description

The invention relates to a catheter.Catheters are well known in the clinical art and are used for various therapeutic applications, particularly for the withdrawal of body fluids or for the administration of medical fluids to a patient. For example, a urinary catheter is known whose elongated catheter shaft is provided with a coating of a hydrogel. In the known urinary catheter, the coating formed from hydrogel is configured to reduce the sliding friction during the placement of the urinary catheter.It is an object of the invention to provide a catheter having improved properties. In particular, the fixing of the catheter in the patient's body is to be improved in order to avoid dislocations and leaks.This object is achieved by providing a catheter having the features of claim 1. Advantageous embodiments are specified in the dependent claims. The wording of the claims is made the subject matter of the description by reference.The catheter of the invention has an elongated catheter shaft. The catheter shaft consists of a hydrogel or is provided with a layer of a hydrogel. The hydrogel is configured to expand and / or contract under the action of at least one stimulus. As a result, the catheter shaft can be transferred between a first state and a second state under the action of the at least one stimulus. In the first state, the hydrogel is contracted and the catheter shaft has a first outer diameter. In the second state, the hydrogel is expanded and the catheter shaft has a larger second diameter. By means of the solution according to the invention, the catheter can be easily placed and fixed in the body of the patient in a particularly reliable manner. The placement takes place in the first state of the catheter shaft, in which the hydrogel is contracted and the catheter shaft has said first outer diameter. After the placement has taken place, the catheter shaft is transferred under the action of the at least one stimulus from the first state, increasing its outer diameter, into the second state. Under the action of the at least one stimulus, the hydrogel expands, whereby the outer diameter of the catheter shaft increases from the first outer diameter to the second larger outer diameter. As a result of the enlargement of the outer diameter, the catheter shaft is placed tightly against the body tissue of the patient surrounding it. This achieves an improved fixation that counteracts dislocations of the catheter shaft. In addition, by increasing the outer diameter, a sealing effect is achieved between the catheter shaft and the surrounding body tissue, which counteracts leaks. The term "hydrogel" refers to a gel of a polymer that undergoes an increase in volume (expansion) and / or a decrease in volume (contraction) under the action of a stimulus. For example, the polymer may be configured to bind and / or deliver water, wherein said stimulus in this case is an ambient humidity and / or a change in the ambient humidity. Molecules constituting the gel of the polymer are chemically and / or physically linked to a network. The chemical linkage can be formed by covalent, supramolecular and / or ionic bonds. The physical linkage can be formed in particular by a running of polymer chains of the polymer. If the hydrogel is configured to expand and / or contract upon a change in the ambient moisture, the hydrogel comprises hydrophilic polymer components. These hydrophilic polymer components swell (expand) under the action of moisture and / or liquid with a considerable increase in volume, without losing their material cohesion. Hydrogels are usually soft and elastic. Different types of hydrogels with different mechanical and / or chemical properties are conceivable and possible. Depending on the chemical composition of the polymer and / or a degree of crosslinking of the polymer chains, the hydrogel can be softer or more rigid in particular. In order to ensure functionally appropriate mechanical properties of the catheter shaft, the hydrogel is preferably configured in such a way that the catheter shaft is, on the one hand, sufficiently dimensionally stable and, on the other hand, sufficiently soft. The sufficient dimensional stability ensures that the catheter shaft can be introduced, i.e. applied, into the body tissue of the patient without any lateral buckling or other undesirable deformations. The sufficient elasticity ensures that the catheter shaft can be removed, i.e. pulled out of the patient's body, without injury to the surrounding body tissue. Preferably, the catheter shaft consists of the hydrogel. Alternatively, the catheter shaft is provided with a layer formed from the hydrogel. In one configuration, the layer is formed as a coating. In a further embodiment, the layer is formed by means of coextrusion.In one embodiment of the invention, a ratio between the second outer diameter and the first outer diameter is at least 1.10, preferably at least 1.15, more preferably at least 1.20.In a further embodiment of the invention, the hydrogel is configured to expand and / or contract in the event of a change in ambient moisture. In this embodiment, the at least one stimulus is said change in ambient humidity. As the ambient moisture increases, the hydrogel expands. As the ambient moisture decreases, the hydrogel contracts. In this embodiment, the catheter is placed in the first state of the catheter shaft, which can also be referred to here as a dry state. When applied, the moisture of the body tissue surrounding the catheter shaft acts on the hydrogel, thereby expanding the hydrogel. It is also conceivable and possible for the catheter to be flushed and / or flushed with liquid in order to expand the hydrogel and to transfer the catheter shaft into the second state.In a further embodiment of the invention, the hydrogel is configured to expand and / or contract in the event of a change in an ambient temperature. In this embodiment, said at least one stimulus is the change in the ambient temperature. As the ambient temperature increases, the hydrogel expands. As the ambient temperature decreases, the hydrogel contracts. The catheter is again placed in the first state of the catheter shaft, which can also be referred to here as a cold state. Under the effect of the patient's body temperature, the hydrogel expands and the catheter shaft is transferred to the second state. A reverse interaction between the ambient temperature and the resulting volume change of the hydrogel is also conceivable and possible.In a further embodiment of the invention, the hydrogel is configured to expand and / or contract in the event of a change in ambient brightness. In this embodiment, the at least one stimulus is the said change in the ambient brightness. As the ambient brightness increases, the hydrogel expands. As the ambient brightness decreases, the hydrogel contracts. A reverse interaction between the ambient brightness and the resulting volume change of the hydrogel is also conceivable and possible. In order to effect the expansion of the hydrogel in the applied state of the catheter, a light guide or another light source can be introduced, for example, into a lumen extended longitudinally through the catheter shaft.In a further embodiment of the invention, the hydrogel is configured to expand and / or contract in the event of a change in a pH value of the environment. In this embodiment, the at least one stimulus is the said change in the pH of the environment. As the pH increases, the hydrogel expands. As the pH decreases, the hydrogel contracts. In addition, an interaction which is the reverse of this between the change in the pH and the resulting volume change of the hydrogel is conceivable and possible. In this embodiment, the catheter is again placed in the contracted state of the hydrogel. During the installation, the hydrogel comes into contact with the surrounding body tissue. The resulting change in pH causes the said expansion of the hydrogel and thus the enlargement of the outer diameter of the catheter shaft starting from the first outer diameter to the second outer diameter.In a further embodiment of the invention, the hydrogel is configured to expand and / or contract in the event of a change in a salt concentration of the environment. In this embodiment, the at least one stimulus is the said change in the salt concentration of the environment. The salt concentration may be, for example, the concentration of NaCl. As the salt concentration increases, the hydrogel expands. As the salt concentration decreases, the hydrogel contracts. Moreover, an interaction which is the reverse of this is conceivable and possible between the change in the salt concentration and the resulting volume change of the hydrogel. In this embodiment, the catheter is again placed in the contracted state of the hydrogel. During the installation, the hydrogel comes into contact with the surrounding body tissue. The change in salt concentration resulting therefrom causes the said expansion of the hydrogel and thus the enlargement of the outer diameter of the catheter shaft starting from the first outer diameter to the second outer diameter.In a further embodiment of the invention, the hydrogel comprises a medicinal active substance. In the applied state of the catheter, the medical active substance can be absorbed by the surrounding body tissue and act in medical fashion. In one embodiment, the medicinal active ingredient is a component of a composition of matter of the hydrogel. Alternatively or additionally, the medical active substance can be applied to the hydrogel and / or the catheter shaft in the form of a coating.In a further embodiment of the invention, the hydrogel has at least one antimicrobial active substance. When the catheter is in the applied state, the antimicrobial agent can be released to the surrounding body tissue. Antimicrobial active ingredients are chemical substances which reduce a proliferative capacity and / or infectivity of microorganisms and / or destroy microorganisms. In one embodiment, the antimicrobial active ingredient is a constituent of a composition of matter of the hydrogel. In a further embodiment, the antimicrobial active ingredient is designed in the form of a coating.In a further embodiment of the invention, the antimicrobial active substance comprises silver particles, a quaternary ammonium compound and / or a biguanide compound. Alternatively, the antimicrobial active substance can be the silver particles, the quaternary ammonium compound and / or the biguanide compound. The above-mentioned antimicrobial active ingredients have proven to be particularly advantageous for the present use.In a further embodiment of the invention, the hydrogel has at least one thromboseo-inhibiting active substance. Thrombosis-inhibiting active substances are chemical substances which reduce blood clotting. This can reduce the attachment of clotted blood to the catheter shaft and thus the formation of blood clots, thus increasing patient safety. When the catheter is in the deployed state, the thromboethrosive agent can be delivered to the surrounding body tissue to reduce blood clotting. In one embodiment, a composition of matter of the hydrogel comprises said thromboseoactive agent. In a further embodiment, the thrombosis-inhibiting active substance is designed in the form of a coating.In a further embodiment, the thrombosis-inhibiting active substance comprises polyethylene glycol. Alternatively, the thromboseoactive agent may be polyethylene glycol. Polyethylene glycol has proven to be a particularly advantageous thrombosis-inhibiting active ingredient for the present use.Further advantages and features of the invention are evident from the claims and from the following description of preferred exemplary embodiments of the invention, which are illustrated on the basis of the drawings. FIG. 1 shows a schematic and partially cut side view of an embodiment of a catheter according to the invention, FIGS. 2, 3 each show a cross section of the catheter according to FIG. 1, wherein its catheter shaft assumes a contracted first state (FIG. 2 ) and an expanded second state (FIG. 3 ), and FIGS. 4 to 7 are schematic views illustrating the use of the catheter of FIGS. 1 to 3.According to FIG. 1, a catheter 1 has an elongated catheter shaft 2. The catheter shaft 2 is elongated between a proximal end 21 and a distal end 22. The proximal end 21 is cut off in the present case and therefore not shown in detail.In the embodiment shown, the catheter shaft 2 consists of a hydrogel H.In an embodiment not shown in the figures, the catheter shaft is instead provided with a layer formed from the hydrogel. This layer can be formed, for example, as a coating or by means of coextrusion. The layer is preferably disposed on an outer diameter of the catheter shaft. The layer is disposed over an entire length of the catheter shaft in one embodiment. In a further embodiment, the layer is arranged only over a part of the total length of the catheter shaft, for example at the distal end, i.e. the catheter tip.The hydrogel H is configured to expand and / or contract under the action of at least one stimulus S 1 to S 4 (see FIG. 2 ). An expansion is to be understood as an increase in volume. A contraction is understood to mean a decrease in volume.By means of said device of the hydrogel H for expansion and / or contraction, the catheter shaft 2 can be transferred between a first state Z 1 (FIG. 2 ) and a second state Z 2 (FIG. 3 ) under the action of the at least one stimulus S 1 to S 4.In the first state Z 1, the hydrogel H is contracted and the catheter shaft 2 has a first outer diameter D 1.In the second state Z 2, the hydrogel H is expanded and the catheter shaft 2 has a larger second outer diameter D 2.The first state Z 1 may also be referred to as a contracted, shrunk, and / or shrunk state.The second state Z 2 can also be referred to as an expanded, enlarged and / or swollen state.In the embodiment shown, the catheter 1 also has a lumen 3. The lumen is elongate through the catheter shaft 2 between the proximal end 21 and the distal end 22. In addition, embodiments are conceivable and possible in which more than one lumen is present, so that a multilumen catheter can thus be referred to. Incidentally, the presence or number of lumens as well as the remaining configuration of the catheter is not essential with respect to the present invention. The catheter can also be placed in a wide variety of ways, for example using a customary catheter-through-the-needle technique (catheter through the needle) or a catheter-through-the-capillary technique (catheter in capillary). The installation using one of these two techniques will be explained in detail below with reference to FIGS. 4 to 7.In embodiments with lumens and a layer of hydrogel on the outer diameter, the inner diameter of the catheter shaft, i.e. the diameter of the lumen, remains unchanged in the swollen state of the hydrogel.The catheter is in principle placed in the first state Z 1 regardless of the placement technology used. The first outer diameter D 1 of the catheter shaft 2 (reduced) in the first state Z 1 allows the catheter 1 to be fitted in a particularly simple manner. In the fitted state, the catheter shaft 2 is transferred starting from the first state Z 1 into the second state Z 2. This takes place under the action of the at least one stimulus S 1 to S 4.The hydrogel H can in principle be configured to expand and / or contract under the action of different stimuli.A first stimulus S 1 is in the present case a change in ambient humidity. A second stimulus S 2 is in the present case a change in an ambient temperature. A third stimulus S 3 is a change in ambient brightness in the present case. A fourth stimulus S 4 is in the present case a change in a pH value of the environment.In various embodiments, the hydrogel H responds to one of the aforementioned stimuli S 1 to S 4 or to any combination of the aforementioned stimuli S 1 to S 4.Specifically, stimuli S 1 to S 4 herein denote an increase in ambient humidity S 1, an increase in ambient temperature S 2, an increase in ambient brightness S 3, and an increase in the pH of environment S 4. Under the action of the stimuli S 1 to S 4 described above, in the embodiment shown, an expansion of the hydrogel H and thus an increase of the outer diameter takes place starting from the first outer diameter D 1 to the second outer diameter D 2. In other words, the catheter shaft 2 swells and / or swells.In the present case, inverted stimuli S1' to S4' have the effect that the catheter shaft 2 is transferred from the second state Z2 into the first state 1 or else is returned. The reverse stimuli S1' to S4' herein denote a decrease in the ambient humidity S1', a decrease in the ambient temperature S2', a decrease in the ambient brightness S3', and a decrease in the pH of the environment S4'.The first stimulus S1 can be generated by moistening the catheter shaft 2 with a liquid. For this purpose, for example, the lumen 3 can be flushed with liquid. The first stimulus S 1 is also generated when the catheter shaft 2 comes into contact with body tissue G of the patient (see also FIGS. 4 to 7 ). The inverted first stimulus S1' can be generated by drying the catheter shaft 2.The second stimulus S2 can be generated by heating the catheter shaft 2, for example by contact of the catheter shaft 2 with the surrounding body tissue G. The reversed second stimulus S2' can be generated by cooling the catheter shaft 2.The third stimulus S 3 can be generated by irradiating the catheter shaft 2 with a light source. For this purpose, it is conceivable and possible, for example, for a light guide to be introduced into the lumen 3 of the catheter 1. The expansion of the hydrogel H is effected in this case under the action of light emitted by means of the light guide.The fourth stimulus S4 can be generated by increasing the pH of the environment of the catheter shaft 2. Such an increase in pH occurs, for example, in contact with the body tissue G. Alternatively or additionally, a non-pH-neutral liquid can be introduced into the lumen 3.Another stimulus may be the change of a salt concentration of the environment of the catheter shaft.In the embodiment shown, the hydrogel H is configured such that the catheter shaft 2 does not undergo any significant increase in its outer diameter under the action of at least one of the stimuli S 1 to S 4. A ratio between the second outer diameter D 2 and the first outer diameter D 1 is at least 1.10, preferably at least 1.15, more preferably at least 1.20 in different embodiments.Furthermore, in the embodiment shown, the hydrogel H comprises at least one medical active substance M. In the embodiment shown, the medicinal active substance M is a constituent of a composition of matter of the hydrogel H. In an embodiment not shown in the figures, the medicinal active substance can be formed in the form of a coating.In the embodiment shown, the hydrogel H has at least one antimicrobial active substance A. The antimicrobial active substance A is in the present case a constituent of the composition of matter of the hydrogel H. In an embodiment not shown in the figures, the antimicrobial active substance is formed in the form of a coating.The antimicrobial active substance A can be, for example, silver particles, a quaternary ammonium compound and / or a biguanide compound.In the embodiment shown, the hydrogel H additionally has a thrombosehibitive active ingredient T. In the present case, the thrombosis-inhibiting active ingredient T is a constituent of the composition of matter of the hydrogel H. In an embodiment not shown in the figures, the thrombosis-inhibiting active ingredient is formed in the form of a coating.In the present case, the thromboseoactive active ingredient T is polyethylene glycol.In the following, the installation of the catheter 1 according to FIGS. 1 to 3 will be described with reference to FIGS. 4 to 7. The description serves to explain the mode of operation of the catheter 1 further. It is also conceivable and possible to use a catheter-by-capillary technique.According to FIG. 4, in a first step, a cannula 100 is first introduced into the body tissue G of the patient, i.e. the body tissue G is punctured with the cannula 100. Cannula 100 is elongated between proximal end 101 and abraded distal end 102, and has lumen 103 elongated between proximal end 101 and distal end 102. The cannula 100 can also be referred to as a hollow needle.Referring to Fig. 5, the catheter 1 is advanced through the cannula 100 into the body tissue G. For this purpose, the catheter shaft 2 is introduced with its distal end 22 leading into the proximal end 101 of the cannula 100 and advanced distally. The catheter 1 is introduced into the cannula 100 in the first state Z 1 and thus in the contracted state of the hydrogel H. The catheter shaft 2 consequently has the (reduced) first outer diameter D 1. Due to the reduced outer diameter, the catheter shaft 2 can be advanced in the cannula 100 as free of friction as possible.Thereafter, the cannula 100 is pulled proximally out of the body tissue G, so that the state shown in FIG. 6 is established. According to FIG. 6, the catheter 2 remains within the puncture channel formed by the cannula 100. In this case, the catheter shaft 2 initially still has its first outer diameter D 1. This means that the catheter shaft 2 is still shrunk at first.As a result of the contact with the surrounding naturally moist body tissue G, the catheter shaft 2 is transferred from the first state (FIG. 6 ) into the second state (FIG. 7 ). By contact with the wet body tissue G, the hydrogel H expands, the catheter shaft 2 swells to increase its outer diameter, and finally assumes the second outer diameter D2. In the swollen state of the catheter shaft 2, the latter bears particularly closely and fluid-tightly against an inner wall of the puncture channel formed by means of the cannula 100. As a result, the catheter shaft 2 is fixed against undesired dislocations, in particular against undesired proximal withdrawal. In addition, an improved sealing effect results and a leakage along the outer diameter D 2 is avoided.

Claims

Catheter (1) having an elongate catheter shaft (2), wherein the catheter shaft (2) consists of a hydrogel (H) or is provided with a layer of a hydrogel (H), wherein the hydrogel (H) is configured to expand and / or contract under the action of at least one stimulus (S1 to S4; S1' to S4'), whereby the catheter shaft (2) is configured to expand and / or contract under the action of the at least one stimulus (S1 to S4; S1' to S4') can be transferred between a first state (Z1) and a second state (Z2), wherein in the first state (Z1) the hydrogel (H) is contracted and the catheter shaft (2) has a first outer diameter (D1), and wherein in the second state (Z2) the hydrogel (H) is expanded and the catheter shaft (2) has a larger second outer diameter (D2).The catheter (1) according to claim 1, wherein a ratio between the second outer diameter (D2) and the first outer diameter (D1) is at least 1.10, preferably at least 1.15, more preferably at least 1.20.The catheter (1) according to claim 1 or 2, wherein the hydrogel (H) is configured to expand and / or contract upon a change of an ambient humidity (S1, S1').Catheter (1) according to any one of the preceding claims, wherein the hydrogel (H) is configured to expand and / or contract upon a change of an ambient temperature (S2, S2').Catheter (1) according to one of the preceding claims, wherein the hydrogel (H) is configured to expand and / or contract upon a change in an ambient brightness (S3, S3').Catheter (1) according to any one of the preceding claims, wherein the hydrogel (H) is configured to expand and / or contract upon a change of a pH of the environment (S4, S4').Catheter (1) according to any one of the preceding claims, wherein the hydrogel (H) is configured to expand and / or contract upon a change of a salt concentration of the environment.Catheter (1) according to any one of the preceding claims, wherein the hydrogel (H) comprises a medicinal agent (M).Catheter (1) according to one of the preceding claims, wherein the hydrogel (H) comprises at least one antimicrobial active ingredient (A).Catheter (1) according to claim 9, wherein the antimicrobial active ingredient (A) comprises or is silver particles, a quaternary ammonium compound and / or a biguanide compound.Catheter (1) according to one of the preceding claims, wherein the hydrogel (H) comprises at least one thromboseoactive agent (T).Catheter (1) according to claim 11, wherein the thromboseoactive agent (T) comprises or is polyethylene glycol.

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