GB2371490A - Space filling medicinal absorbant articles - Google Patents

Description

SPACE FILLING MEDICINAL ARTICLES

The present invention relates to improved dressings for the treatment of cavity wounds, and to methods of use of the dressings in the treatment of such wounds.

There is a need in clinical practice for absorbent medicinal articles that can be inserted into deep wounds to absorb wound exudate and provide cavity filling.

Such dressings should be highly absorbent, conformable to the shape of the wound, and inexpensive.

It is known to provide textile or foam-based absorbent structures for dressing deep wounds. Those structures are insufficiently conformable to fit every deep wound, unless they are cut into shape. Furthermore, such absorbent structures can be relatively difficult to remove from a deep wound after use without causing further trauma.

US-A-4837285 describes the use for soft tissue cavity filling of resorbable collagen sponge beads having diameters of from 0.1 to 4.0 mm. The beads have pore sizes of from 50 to 350 micrometers. Such beads can be difficult to handle, and are not suitable for use as a removable, absorbent dressing for deep wounds.

DE-A-4037931 describes a deep medicinal article structure consisting of a cavity filling plug of resorbable collagen foam containing an array of hollow resorbable filaments. The filaments are bundled together at one end, and connected to a drain for wound fluid, whereby the wound fluid is continuously drained from the wound cavity through the hollow filaments. Such a structure is relatively expensive to construct, and insufficiently conformable to a wide range of wound cavity shapes.

EP-A-0171268 describes absorbent, non-adherent wound dressings for use in the treatment of deep wounds, wherein the dressing comprises a porous bag containing individual pieces of a conformable, resilient, absorbent hydrophilic foam.

It is an objective of the present invention to provide a highly conformable absorbent dressing for a deep wound. It is a further object of the present invention to provide such a dressing for a deep wound that is inexpensive and simple to construct.

It is a further object of the present invention to provide such a dressing for the deep wound that is easy to remove after use.

It is a further object of the present invention to provide structures for soft tissue cavity filling that are highly conformable and inexpensive.

The present invention provides a medicinal article comprising a substantially tetrahedral liquid-permeable bag and at least one elongated absorbent body contained within the bag.

The liquid-permeable bag is formed from flexible sheet material. Preferably, the sheet material is highly conformable to enable the bag to be inserted comfortably into a wide variety of wounds. Suitable sheet materials include woven and nonwoven fabrics and perforated thermoplastic sheet materials. Preferred sheet materials include spun-bonded fabrics (such as spun bonded nylon) and vacuum perforated thermoplastic films. Preferably, the sheet material is conformable and it may be elastomeric. Preferably, the sheet material is hydrophilic. Suitable materials include, but are not limited to, polyethylene, polypropylene, polyester, polyamides such as nylons, fluoropolymers such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE), and mixtures thereof. The currently preferred film-forming thermoplastic polymer is ethylene methyl acrylate (EMA).

The bag may comprise more than one layer of sheet material. Preferably, the sheet materials include at least sufficient fusible material to permit heat sealing of the sheet materials to form the bag.

The term liquid-permeable signifies that aqueous liquids such as wound fluids can pass freely through at least a region of the bag under physiological conditions. At the same time, the bag should effectively prevent escape of the absorbent body from inside the bag, and therefore preferably there are substantially no apertures in the bag of area greater than 5 mm2, and preferably there are substantially no apertures of diameter area greater than 2 mm2. Preferably, the bag is substantially uniformly liquid-permeable, for example it may consist essentially of a liquid permeable sheet material.

Preferably, the bag is formed from a single piece of sheet material. For example, the bag may be formed from a single piece of sheet material in form-fill-seal packaging equipment in known fashion. It is especially easy to make tetrahedral bags in such equipment by providing top and bottom transverse sealing jaws oriented at substantially 900 to one another in the same plane perpendicular to the direction of travel of the sheet material. This results in substantially perpendicular transverse seals on opposite sides of the tetrahedron. It is thought that the advantages of the present invention can also be achieved if the transverse seals are oriented at lesser angles to one another, for example at an angle in the range 600 to 900, or even at an angle in the range from 300 to 900 to one another.

The bag is substantially tetrahedral. That is to say, it preferably has substantially the shape of a polyhedron having four substantially triangular faces. The tetrahedron preferably has at least one two-fold axis of symmetry, and more preferably it is substantially a regular tetrahedron. The maximum dimension of the bag is preferably from 1 to 20 cm, more preferably from 2 to 10 cm.

The tetrahedral format combines ease of manufacture with a three-dimensional shape that is especially suitable to maximise absorbency, liquid permeability and conformability. The tetrahedral format offers a more versatile presentation that can easily be molded to the contours of an irregularly shaped wound. Absorption of exudate allows gentle expansion to form a highly flexible tetrahedron that can mold to the contours of the wound bed.

The elongated absorbent body is flexible to enable the dressing to take up the shape of the cavity into which it is inserted. Preferably, the elongated absorbent body has a length at least 5 times its mean diameter, more preferably at least 10 times its mean diameter. For example, the elongated absorbent body may be in the form of a strip or string. The dry basis weight of the absorbent strip may be in the range of 0.5-5g/m, such as 1-4g/m. The uncompressed thickness of the absorbent strip may be in the range of from 0.5mm to 10mm, such as 1mm to 4mm. The free (uncompressed) liquid absorbency measured for physiological saline may be in the range of 5 to 30 g/g at 25OC.

The elongated absorbent body may be made from any suitable hydrophilic material, such as woven or nonwoven textiles, hydrophilic foams, hydrogels, or composite structures comprising more than one of these.

In certain embodiments, the absorbent body is formed from a woven or nonwoven textile strip or rope, for example a rope of viscose staple fibers. Preferably, short (staple) textile fibers are avoided because they may shed from the article into the wound. The textile filaments may be melt bonded to increase their integrity in use.

In other embodiments, the absorbent body comprises a layer of absorbent hydrophilic foam. Preferably, the hydrophilic foam has a density of from 0.28 to 0.5 g/cm3, and more preferably from 0.32 to 0.48 g/cm3. Preferably, the foam has an elongation to break of at least 150%, more preferably from 500% to 1000%.

The foam is hydrophilic and absorbs aqueous fluids such as wound exudate with swelling. However, the foam is preferably highly cross-linked and substantially insoluble in water. Preferably, the foam has an absorbency of at least 3 g saline/g, and preferably a swellability in water of at least 200%.

Preferably, the foam comprises less than 10% water prior to use as an absorbent, more preferably less than 5% water and more preferably it contains less than 2% of water before use. The hydrophilic foam provides enhanced absorbency for liquid exudate. This is because the initial substantially anhydrous condition and porous structure of the foam enable it to absorb a larger amount of

water by both chemical and physical absorption. Furthermore, the porous structure of the foam provides for rapid uptake of liquid exudate, in contrast to pure hydrogel dressings. Preferably, the hydrophilic foam strip has a thickness of from 1 to 20 mm, more preferably from 1.5 to 5 mm.

Especially preferred are the open celled hydrophilic polyurethane foams prepared in accordance with EP-A-0541391, the entire content of which is expressly incorporated herein by reference. Briefly, these polyurethane foams are formed by reacting an isocyanate-capped polyether prepolymer with chain extending and terminating reagents in the presence of sufficient water to produce foaming.

Preferably, the isocyanate-capped polyether prepolymer comprises an isocyanatecapped ethyleneoxy/propyleneoxy prepolymer. For example, one of the prepolymers available under the Registered Trade Mark HYPOL from Dow Chemical Company, 2 Heathrow Boulevard, 284 Bath Road, West Drayton, UK.

The foam may be cast in a layer and then cut into strips to provide the desired elongate absorbent body.

The absorbent body may comprise a strip or coating of a hydrogel. The hydrogel helps to maintain a moist but not wet wound surface by reversibly absorbing and retaining aqueous wound fluid. The hydrogel can be formed from medically acceptable macromolecular materials that preferably have the ability to swell and absorb fluid while maintaining a strong integral structure. Preferably, the hydrogel composition forms a gel or emulsion that is substantially insoluble in water under physiological conditions, whereby the hydrogel is not washed away by the wound fluid. The hydrogel may be a biopolymer, and/or it may be bioabsorbable. That is to say, it may undergo gradual resorption in vivo.

Exemplary insoluble gels include certain cross-linked polyacrylate gels, calcium alginate gels, cross-linked hyaluronate gels, gels formed from vinyl alcohols, vinyl esters, vinyl ethers and carboxy vinyl monomers, meth (acrylic) acid, acrylamide, N-vinyl pyrrolidone, acylamidopropane sulphonic acid, PLURONIC (Registered Trade Mark) (block polyethylene glycol, block polypropylene glycol) polystyrene-, maleic acid, NN-dimethylacrylamide diacetone acrylamide, acryloyl morpholine,

and mixtures thereof. Preferably, the gel is coated onto to the surface of a sponge or textile material to resist washing off by wound fluid. In certain embodiments the gel may be chemically bonded to the surface.

Preferably, the hydrogel comprises a hydrogel material selected from polyurethane gels, biopolymer gels, carboxymethyl cellulose gels, hydroxyethyl cellulose gels, hydroxy propyl methyl cellulose, modified acrylamide and mixtures thereof.

Suitable biopolymer gels include alginates, pectins, galactomannans, chitosan, gelatin, hyaluronates and mixtures thereof. Some of these biopolymer materials also promote wound healing.

Preferably, the gels are cross-linked, and the cross-linking may be either covalent or ionic. It will be appreciated that the degree of cross linking will influence the physical properties and rate of resorption of the hydrogel layer in vivo.

Preferably, the hydrogel material further comprises from 5 to 50% by weight on a dry weight basis of one or more humectants such as glycerol.

Preferably, the hydrogel comprises a hydrogel material of the kind described in WOOO/07638, the entire content of which is incorporated herein by reference.

Preferably, the density of the hydrogel is greater than 0.5 g/cm3, more preferably

3 greater than 0. 8 g/cm3, and most preferably from 0. 9 to 1. 1 g/cm3. Preferably, the thickness of the hydrogel strip is from 1 mm to 10 mm, more preferably from 2 mm to 5 mm.

Preferably, the hydrogel layer comprises or consists essentially of a polyurethane, and preferably this is cross-linked and preferably it is substantially insoluble in water at ambient temperature. Preferably, the gel can absorb 1 to 10 g/g of physiological saline at 200, more preferably 2 to 5 g/g. The saline absorbency is determined by the steps of: weighing the hydrogel, submerging the hydrogel in 0. 9% saline for 24 hours, draining for 30 seconds, and reweighing.

Preferably, the hydrogel comprises from 1 to 30% of water, more preferably from 10 to 20% by weight of water before use. Preferably, the hydrogel contains from 1 to 40%, more preferably from 5 to 15%, by weight of one or more humectants, preferably selected from the group consisting of glycerol, propylene glycol, sorbitol, mannitol, polydextrose, sodium pyrrolidine carboxylic acid (NaPCA), hyaluronic acid, aloe, jojoba, lactic acid, urea, gelatin, lecithin and mixtures thereof. in certain preferred embodiments, the absorbent body is a strip of layered material comprising a hydrophilic foam layer, such as first polyurethane foam layer, and a hydrogel layer, such as a polyurethane hydrogel layer, wherein the hydrogel layer is laminated to the hydrophilic foam layer. That is to say, it is applied to and at least partially covers one surface of the foam layer. Preferably, the hydrogel layer is bonded to the foam layer, for example by an adhesive or by radiation crosslinking. More preferably, the hydrogel layer is bonded to the foam layer by urethane or urea linkages. This can be achieved easily by applying a polyurethane foam layer to a polyurethane hydrogel layer (substantially without mixing) before polyurethane curing is complete, as described in more detail below.

The maximum length of the elongated absorbent body is preferably from 3 to 20 cm, more preferably from 5 to 10 cm.

In certain preferred embodiments, the one or more elongated absorbent bodies are entangled or otherwise form a bundle. More preferably, the one or more elongated absorbent bodies are the form of a single bundle.

Preferably, the bag contains from one to three elongated absorbent bodies.

Preferably, the bag contains no more than ten elongated absorbent bodies.

The elongated bodies provide high liquid absorbency and also ease of manufacture and optimised conformability. The pressure to the wound bed is minimised and evenly distributed. Furthermore, the elongated absorbent bodies are less likely to shed particles through the sides of the bag.

Preferably, the medicinal article according to the invention further comprises a medicament or mixture of medicaments. Suitable medicaments include antimicrobials, growth factors, steroids, antifungal agents, spermicidal agents, and anaesthetics. Suitable antimicrobials include antibiotics, silver salts, povidone iodine and chlorhexidin. Preferred amounts of the antimicrobials are from 0.01 to 100 mg, more preferably from 0.1 to 10 mg. The medicament may be introduced into the dressing, for example, by impregnating the dressing or the absorbent bodies only with a dispersion of the medicament in a solvent such as water, followed by drying.

In certain embodiments the absorbent bodies may comprise a layer, strip or string comprising a therapeutically active biopolymer such as collagen, an alginate or hyaluronic acid (to promote wound healing), or oxidized regenerated cellulose (a haemostat).

In certain embodiments the absorbent bodies may comprise a layer, strip or string comprising activated charcoal for odor absorption. Optionally the activated charcoal containing strip may include an antimicrobial agent such as iodine or silver. Suitable materials are the silver containing charcoal cloth described in GB A-2127389 and the elastomeric foam impregnated with charcoal and iodine described in EP-A-0053936.

An external string or loop may be attached to the bag to assist removal after use.

Preferably, the medicinal article according to the invention is sterile and packaged in a microorganism-impermeable pack. Sterilization may be achieved after packaging, for example by gamma-irradiation.

It will be appreciated that the medicinal articles according to the present invention have many uses, not only for filling and treatment of deep wounds, but also for insertion into and removal from other body cavities such as the mouth, gastrointestinal tract and vagina for therapeutic and prophylactic purposes.

Preferably, the medicinal articles according to the present invention are suitable for use as a dressing for a deep wound.

Accordingly, the present invention further provides a medicinal article according to the present invention for the preparation of a medicament for use in the treatment of wounds. In particular, for use in the treatment of deep and exuding wounds such as decubitis ulcers, pressure sores, venous ulcers, deep and open wounds and bums.

In another aspect the present invention provides a method of treatment of a deep wound in a mammal by applying to the wound a medicinal article according to the invention for a time sufficient to promote healing of the wound.

A specific embodiment of the present invention will now be described further by way of example, with reference to the accompanying drawing, in which : Figure 1 shows a perspective view of a medicinal article according to the present invention with part of one side wall of the bag cut away to show the interior.

Example 1 A laminated absorbent strip is prepared from the following constituents: Foam Layer: HYPOL a 50g Water 32g Acrylic copolymer" 12g Methanol 6g Hydrogel Layer HYPOL a 25g Water 100g a HYPOL PreMA G60 from Dow Corning Ltd. b PR MAL B-15J or RHOPLEX N-560 (Registered Trade Marks).

The components of each layer are mixed and spread individually to make flat sheets of nominal thickness 1 to 5 mm. The sheets are allowed to cure partially for about 90 seconds at ambient temperature, and are then pressed gently together. The resulting laminate strip has a polyurethane foam layer laminated to a hydrogel layer. A spiral cut is made in the laminate to cut it into a single strip of length about 10 cm, width about 0.5 cm and depth about 0.5 cm. The spiral-cut strip is placed in an oven at 100 C for about 15 minutes for curing and drying. The process includes an additional drying and curing step at 40 C for about 30 minutes. The laminate spiral curls and entangle during the final curing and drying step to produce a three-dimensional bundle of the laminate strip.

The medicinal article 1 according to the invention is assembled as follows.

A sheet of medical grade spunbonded nylon fabric is formed into a tube having a longitudinal heat bonded lap seal on a vertical form-fill-seal apparatus in conventional fashion. A transverse heat seal 2 is formed at the bottom of the tube by means of a pair of heated sealing and cutting jaws, again in conventional fashion. The curled laminate strip 3 is dropped into the bag, and a transverse heat seal 4 is formed at the bottom of the tube by means of a pair of heated sealing and cutting jaws oriented at 900 to the lower jaws so as to give a substantially tetrahedral bag 5.

The bag is then packaged in a microorganism-impermeable pouch (not shown) and sterilized with gamma irradiation.

The above embodiment has been described by way of example only. Many other embodiments falling within the scope of the accompanying claims will be apparent to the skilled reader.

Claims (14)

1. A medicinal article comprising a substantially tetrahedral liquid-permeable bag and at least one elongated absorbent body contained within the bag.

2. A medicinal article according to claim 1, wherein the bag consists essentially of a liquid-permeable sheet material.

3. A medicinal article according to claim 1 or 2, wherein the bag is formed from a single piece of sheet material.

4. A medicinal article according to claim 3, wherein the bag is provided with substantially perpendicular transverse seals on opposite sides of the tetrahedron.

5. A medicinal article according to any preceding claim, wherein the elongated absorbent body has a length at least 5 times its maximum cross-sectional dimension.

6. A medicinal article according to claim 5, wherein the elongated absorbent body has a length at least 10 times its maximum cross-sectional dimension.

7. A medicinal article according to any preceding claim wherein the one or more elongated absorbent bodies are entangled or form a bundle.

8. A medicinal article according to any preceding claim wherein the bag contains no more than ten elongated absorbent bodies.

9. A medicinal article according to any preceding claim wherein the bag contains from one to three elongated absorbent bodies.

10. A medicinal article according to any preceding claim wherein the bag contains a plurality of elongated absorbent bodies in the form of a single bundle.

11. A medicinal article according to any preceding claim wherein the elongated absorbent bodies comprises a hydrophilic foam.

12. A medicinal article according to claim 11, wherein the elongated absorbent bodies comprises a layer of a hydrophilic foam laminated to a layer of a hydrogel

13. A medicinal article according to any preceding claim, further comprising an effective amount of a medicinal substance.

14. A medicinal article according to any preceding claim, wherein the article is sterile and packaged in a microorganism-impermeable pack.