Medical-surgical Dressing For Burns And The Like

Abstract

A medical-surgical dressing is provided for topical application as a conforming cover for the therapy and protection of burns and the like. The dressing which has a porous laminated construction includes a facing layer of thrombogenic open-cell foam material and a coextensive gas-permeable backing. When applied to the body the facing layer serves as a receptacle for debris and liquid exudate. The backing is impermeable to liquids and to bacteria whereby the dressing serves to conserve vital body fluids, facilitate clot formation, confine the debris and exudate, and expose confined bacteria to phagocytic invasion.

Parent Case Text

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of application Ser. No. 6466, filed Jan. 28, 1970, and now abandoned.

Description

SUMMARY AND DETAILED DESCRIPTION

This invention relates to a new and useful type of medical-surgical dressing adapted for adhesion to the surface of the wound without additional support while protecting the covered area with a skin-like membrane. The invention is applicable to many types of injury but is of particular use in the active therapy and dressing of the thermal, chemical, electrical, and similar wounds conventionally classified as "burns."

The American Illustrated Medical Dictionary by Dorland classifies burns as follows: "Burns of the first degree show redness, of the second degree, vesication, of the third degree, necrosis through the entire skin, and fourth degree, more or less charring."

Thermal injuries require a unique combination of therapy and dressing. The physiologic functions of the skin are absent or, at best, materially impaired:

A. body fluids and their essential components are lost continuously;

B. the barrier characteristics preventing invasion of harmful micro-organisms and other noxious agents are no longer intact, and potential fatal Pseudomonas infection is a continuous serious threat to the patient's life;

C. the debris reservoir of necrotic tissue saturated with seeping blood components remains in place on the wound site harboring and nourishing agents of infection whose presence and by-products interfere with the regeneration of viable, functioning, epithelial tissue having skin organ properties.

Basic tenets of therapy require:

A. the removal of the necrotic products of injury;

B. providing a barrier to bacterial invasion from the environment while controlling the contamination already present; and

C. stemming the loss of vital body fluids from the already seriously weakened patient.

Prior to the present invention, burn injuries and the like have been treated at various stages by application of sterile coverings in the form of pastes or creams, gauze wrappings, natural and synthetic membranes or skin materials, films, sponges, or the like. Except in the case of skin grafting, the approach has been to prevent adhesion of the covering materials to the wound surface. On the other hand, a review of the burn literature shows that a number of substances have been used experimentally to adhere to the exudating wound contaminated with necrotic products of thermal injury. Such adherence is undesirable, however, since bacterial contamination will grow luxuriantly upon the surface of the dressing, nourished by the products of injury and seepage. Examples of such prior art materials are nylon velour and polyvinyl alcohol sponge. Attempts to prevent such bacterial contamination from the environment have involved the use of any of various synthetic impermeable barrier membranes. In this way, invasion of external micro-organisms is avoided but invariably anaerobic infection takes place within the dressing. As a result, there is gas formation, and the dressing tends to slough away so that any temporary benefits give way to a reversal. In any case, the need for wound debridement as indicated has heretofore been a substantial problem. It has generally required a painful surgical procedure accomplished in the operating room, occupying full staff for several hours at significant expense.

It is therefore an object of the invention to provide an improved low-cost medical-surgical dressing for application in a course of treatment to burns and the like.

It is another object of the invention to provide a fabricated medical-surgical dressing which functions as a skin-like integument for protection and healing of burns and the like.

Still another object is to provide a dressing which is thrombogenic in action and which can be removed when appropriate to accomplish mechanical debridement in a convenient economical manner.

Yet another object is to provide a dressing capable of conserving vital body fluids and serving to facilitate spontaneous local decontamination by means of phagocytic action.

These and other objects, features and advantages of the invention will be seen from the following description and the accompanying drawing in which:

FIG. 1 is a representation of a medical-surgical dressing of the invention in laminated sheet form including an open-cell sponge facing layer and a backing layer;

FIG. 2 is an enlarged view of a typical cell of the open-cell sponge facing material of the dressing of FIG. 1;

FIGS. 3a, and 3b, and 3c are sectional views of a burn wound segment showing successive stages in healing when covered in face-to-face relation by the dressing of the invention; and

FIG. 4 is an illustration of a typical burn area.

In accordance with a preferred embodiment of the invention, a unitary surgical dressing 10 (FIG. 1) is provided having a facing layer 11 of neutral thrombogenic reticulated open-cell foam or sponge material 14 and a coextensive gas-permeable backing 12 mutually secured at interface 13 by adhesive means, thermal fusion or other suitable means. By way of introduction, the dressing of the invention has particular application for at least three typical wound situations:

1. the untreated necrotic burn surface,

2. the debrided burn surface, and

3. the donor site remaining after removal of skin graft.

APPLICATION FOR THE NECROTIC BURN SURFACE

As regards the necrotic exuding burn surface, the facing layer 11 having an open-cell structure serves as a receptacle for debris and liquid exudate when applied as intended with the facing contacting the surface of the body. The facing layer is thick enough to constitute a void space for absorption of liquid and yet is relatively thin so that the contained materials are maintained in close proximity to the body tissue with the result that the natural anti-infective phagocytic interaction can take place. The backing 12 in turn is impermeable to liquids and to bacteria so that the applied dressing serves to confine the debris and exudate within the facing layer 11. It is an unexpected advantage of the invention that the dressing eliminates or minimizes the fluid loss from the site of injury. The conventional step of concurrently administering fluid replacement to the patient is largely avoided. The dressing also favors the healing process. In this regard the facing layer serves to promote contact for phagocytic decontamination whereby infection is eliminated usually without the need for including antiseptic agents or antibiotics. Also it is found that removal of the dressing leaves a cleaner surface. With each repeated dressing change the nature of the wound surface 23 progressively improves so that in many cases later skin grafting is not required or if required may be accomplished in much shorter periods. In this connection, FIG. 3a illustrates the relationship existing between the dressing 10 when first applied to an open third degree burn 20 comprising subnecrotic viable tissue 21 and debris 22 interdelineated by a generally roughly uneven wound profile 23. FIG. 3b is a similar view illustrating the improvement resulting from prior dressing application, improved particularly as a smoother wound profile 23 and decreased thickness of the debris layer 22. FIG. 3c illustrates a later stage of therapy in which debris 22 is absent and islands 24 of epithelial skin have developed spontaneously.

For the facing layer 11 any of various neutral synthetic reticulated open-cell solid foam or sponge materials are satisfactory. The layer is conveniently fabricated in a single sheet as by extrusion, slicing from a larger sponge block or by other suitable means. FIG. 2 illustrates a typical cell 30 of the foam formed of connected strands 31 defining open faces 32 and constituting largely an open void. The layer 11 is reticulated, that is, the cells 30 form an open communicating network throughout the layer. Also, the sponge material for purposes of the invention is neutral, that is, physiologically compatible, nontoxic and nonirritating. A preferred material is reticulated polyurethane sponge or foam (Scottfoam, Scott Paper Company). The material and the method of its preparation are described in U.S. Pat. No. 3,171,120. A relatively small celled foam is preferred especially about 60-100 mesh foam. The foam structure which, as indicated above, is a skeletal strand lattice, has about 97 percent void volume, relatively high permeability and surface area, and is available in a variety of rigidities or textures. For purposes of the invention, the thickness of the facing layer 11 is critical. In general, the facing layer should be sufficiently thin so that debris, fluids, etc., contained therein are accessible for phagocytic invasion from the body surface. On the other hand, if the layer is too thick it is found that segregated exudate located, for example, at the interface 13 is not reached by the natural phagocytic action with the undesirable result that infection takes place and spreads within the dressing thereby delaying or preventing the healing process. In general, the preferred thickness for the facing layer is about one-sixteenth of an inch. The layer, on the other hand, should not be so thin that it lacks capacity for reception of debris and liquid.

An outstanding feature is the unique property of the reticulated foam layer 11 to accept the necrotic residue. The blood and serum saturated debris--once having become enmeshed by penetrating the foam layer--is held tenaciously in place by the natural physiologic property of coagulation. This is accomplished by leaving the dressing in place for relatively short periods up to about 24 hours. Afterwards, the necrotic debris can be effectively removed with the dressing, if desired, by immersion in water using, for example, a hydrobath. Experience has shown that a course of three such applications is adequate to debride the usual necrotic injury. It will be understood, however, that the number of dressing applications is not critical and can be varied according to circumstances. It is a particular advantage of the dressing that debridement is accomplished at no additional medical staff time since it is achieved progressively in the daily dressings change. Surgical services and an operating theater are not required. Further trauma is spared the patient and his progress is speeded accordingly.

An essential aspect of the invention, in addition to the means of nonsurgical debridement, is the provision of a physical barrier having the above-mentioned physiologic characteristics of liquid containment, skin-like apposition, and dermatologic gas permeability. In this regard, the barrier membrane must be positioned immediately adjacent to the wound surface (preferably about one-sixteenth inch as indicated above) and be retained there intimately and tenaciously. The apposition referred to has twofold importance; to minimize the loss of tissue fluids (which loss would waste the health of the patient) and to maximize effective phagocytic migration from subnecrotic, viable tissue throughout the wound within the restraining membrane. Phagocytes, as is known, the agents of healthy tissue origin, are the basic defense mechanisms of the normal body in controlling infections. They can operate by moving from the wound into surrounding liquid exudate where they engulf bacterial bodies. The dressing, according to the invention, must therefore adhere closely to the wound surface, maintaining the barrier film immediately adjacent to confine the liquid for phagocytic action.

The backing 12 of the invention can be any flexible or conformable microporous neutral film or web material which, under the conditions of use contemplated, is semi-impermeable, that is, impermeable to liquids and to bacteria and yet gas-permeable. A preferred material is a microporous polymer film of the kind described in U.S. Pat. No. 3,426,754. The term "microporous" as used herein refers to porosity of a structure having permeability equivalent to or not exceeding that of a porous film or web structure with an apparent density of about 50-98 percent and preferably about 50-90 percent such that the open pores in the structure range in dimension principally from 10.sup..sup.-5 to 5.times.10.sup..sup.-4 mm. One such preferred material is a microporous polypropylene film known as CDK Microporous Film supplied by the Celanese Corporation. The latter material typically has a water vapor transmission of 6.2 grams per square foot per hour per millimeter thickness, a gas permeability of 200-800 seconds per 10 c.c. flow per pressure drop of 4.88 inches, of water, and a calculated pore size distribution of 0.02 to 0.2 microns, that is, 2.times.10.sup..sup.-5 to 2.times.10.sup..sup.-4 mm. Gases to which the backing is permeable are, for example, oxygen, nitrogen carbon dioxide, ethylene oxide, and water vapor; liquids to which the backing is impermeable are water, saline, serum, blood, and similar liquids. The selected permeability of the backing 12 desirably makes for effective phagocytic control of infection under the dressing, prevention of invasion by disease agents from the environment, and aeration, that is, avoidance of anaerobic conditions conducive to establishing infection of "gas gangrene" and related anaerobes.

Another preferred material for construction of the microporous film backing 12 is elastomeric. Examples of such material are natural and synthetic-like material rubber such as vulcanized latex, silicone rubber and the like having microporous structure in the above-mentioned range and being impermeable to liquids and bacteria and yet gas-permeable. One such material, which is preferred, is vulcanized medical grade silicone rubber and in particular the material supplied as Silastic 370 by Dow-Corning Corporation, Midland, Michigan, U.S.A. Silicone rubber is well-tolerated by body tissue and is available in elastic, conforming sheets of suitable strength, weight, color and texture. Silicone rubber is permeable to gases of biological importance in the range specified above and restricts transmission of liquids and bacteria. As an example of the selected permeability of a preferred 5 mil thick vulcanized silicone rubber sheet, water vapor equivalent to 6.2 grams of liquid water will penetrate 1 square foot in 1 hour. Oxygen gas in the amount of approximately 20 liters will penetrate a 5 mil film of silicone rubber in 24 hours when an area of 100 square inches is exposed to the driving force of one atmosphere. To carbon dioxide gas the film is approximately 1/5 as permeable under the same conditions. Ethylene oxide gas mixtures with carbon dioxide diluent and water vapor, as prescribed for sterilizing atmosphere to destroy viable micro-organisms totally in their active and nonactive (spore) forms, likewise pass the backing film having the microporous structure described, as demonstrated by sterility test using standard spore test strips and viable agar slant preparations of a wide variety of test organisms in which test the organisms are killed or rendered sterile. Conversely, bacteria-laden air drawn through the backing film and then passed over sterile agar culture plates designed for culturing any airborne organism, fails to seed the culture plates indicating that no bacterial penetration occurs through the gas-permeable membrane.

Still another preferred type of backing film is semipermeable Teflon membrane or sheeting available in a variety of specifications differing in thickness, porosity, stretchability, etc. For advantage in tolerance, permeability and stretch, a Teflon film of choice is one supplied as No. 21-81-A by Gore & Associates, Newark, Delaware, U.S.A. This material is 3.9 mils in average thickness, porosity 52 percent, air permeability 0.002 metric units, and maximum pore size about 0.33 microns or 3.3.times.10.sup..sup.-4 mm. (being approximately 10 times more gas-permeable than the above-specified CDK Microporous Film).

For purposes of the invention, a significant advantage of elastomeric film is that it can be cast in the desired depth of uniform thickness and made an integral part of the open cell facing layer 11 without requiring supplemental adhesive for lamination.

APPLICATION FOR THE BURN LESION

As indicated above, the dressing of the invention can be used upon the burn lesion remaining after the necrotic products of injury have been removed. This relatively clean area, which might indeed constitute one-half or more of the surface area of the patient, must be covered during either the period of epithelial regeneration or the period preliminary to the surgical procedure of skin replacement or grafting. By covering the third-degree injury surfaces (now clean) with the dressing and allowing it to remain in place for a period of about 72 to 96 hours between changes, several beneficial results are obtained. First, infection is controlled. Second, fluid loss is limited to the capacity of the facing layer 11. Third, a surface is provided for the comfort and protection of the patient who can now become ambulatory weeks ahead of the conventional treatment and procedures. Fourth, islands of epithelialization appear throughout the wound that rapidly expand to form a near normal, healthy, viable skin covering. Previous to this invention, serious wounds were always eventually covered with skin replacement moved from other areas of the body, under laborious and costly surgical procedures that often had to be repeated several times. The ability to avoid the laborious skin-grafting procedure has materially reduced the hospitalization time, the hospital staff commitment in surgery, and the patient discomfort while he now waits for his donor site to heal.

APPLICATION FOR THE DONOR SITE

The dressing of the invention can also be applied usefully to the donor site of patients requiring skin grafting for any purpose, such as reconstructive surgery, etc. The cleaned wound created by the surgeon taking skin from one area of the body to place on another area generates an exposed surface subject to invasion of infection, and similar perils, during the 3 to 4 week healing process. By providing an immediate semipermeable cover for the new wound, the patient is more comfortable and is physiologically protected from infection.

The invention contemplates the facing layer 11 and backing 12 as a pliable unitary structure laminated together. To this end, the backing and facing layer can be secured together in any suitable way--for example, by means of an applied adhesive interlayer or by thermoplastic fusion. One preferred means of securing the facing and the backing is the adhesive means described in U.S. Pat. No. 3,400,095, a specific example of which is Scotch Grip 3M-77 adhesive. Another adhesive of choice is self-curing acrylic resin in a sprayable liquid form. An example of the latter is Gelva multipolymer solution RA-858 supplied by the Monsanto Company. Other preferred adhesives are a silicone adhesive known as Medical Adhesive B MDX-4-4037 (Dow-Corning Corporation) and the adhesive means described in U.S. Pat. No. 3,426,754.

An alternative material for the backing 12 of the invention is microporous surgical adhesive tape of the type described in U.S. Pat. No. 3,121,021. For purposes of the invention, the backing 12 is coextensive with the facing layer 11, that is, it preferably matches the layer 11 but, if desired, it can overlap or extend beyond edges of the facing layer. In the usual case, the dressing adheres well without further support. However, if desired, the dressing can be fastened in place by adhesive tapes or by gauze strapping or other suitable means. Any open margins 14 can be covered over by gauze or other suitable sterile cover or barrier. The lateral dimensions of the dressing can be varied widely and, where appropriate, several dressings can be laid down together in a covering mosaic or patchwork. For professional use, the dressing, available in a range of sizes and forms and in sterile packaged form, can be dispensed and cut to size exceeding or approximating the burn area to be treated. The dressing is then placed upon the burn area. Referring to FIG. 4, the dressing 10 (in dotted outline) can be blanketed over an area including second, third, and fourth degree burns. In this case, the dressing does not adhere to the vesicated area since the latter is free of exudate. Advantageously, the dressing serves to debride the necrotic area selectively thereby avoiding the need for the staff to attempt to debride the same surgically. The surgeon accordingly does not need to make a decision as to the location of the line of demarcation between the necrotic and vesicated areas.

For purposes of illustration, the following exemplifies the production of dressings according to the invention. A microporous polypropylene film is selected having about 30 percent voids of uniform pore size ranging from 1.times. 10.sup..sup.-5 to 5.times.10.sup..sup.-4 mm., thickness about 1 mil and width 4 feet. The film in roll form is first laminated onto an adhesive-coated release liner as described in Example III of U.S. Pat. No. 3,426,754. As an alternate procedure, liquid adhesive (Gelva RA858) is sprayed directly on the film at the rate of 3 grams per square foot. The resulting laminate is then drawn away from the liner and passed through opposed calender rolls with a matching web of polyurethane foam roll stock (Scottfoam, 50 to 150 cells per lineal inch, one-sixteenth inch thickness, 4 feet width). The calendar rolls are adjusted press the foam against the exposed adhesive moving at equal speed, and the resulting adhesively bonded laminate web is then wound onto a takeup roll. Alternately, individual matching sheets of permeable film and polyurethane foam stock, as opposed to rolls, can be laminated together. The dressing stock is finally subdivided into sizes suitable as dressing units, and these are packaged and sterilized by conventional means. The invention contemplates that the dressings may include antibiotics, proteolytic enzymes, or other similar agents for debridement and control of infection. For example, a sterile dressing measuring 12.times.13 inches is treated with 3 grams of sterile enzymatic ointment (Elase) by applying the same under aseptic conditions uniformly to the facing. Each such dressing contains one unit of fibrinolysin and 666 units of desoxyribonuclease. The latter ointment can be substituted or supplemented by an antibiotic ointment (e.g., chloramphenicol ointment containing 10 mg. of the antibiotic). Other antibiotics can also be used such as bacitracin, neomycin, polymyxin, and paromomycin.

Claims

I claim:

1. A unitary surgical dressing adapted for topical application as a conforming thrombogenically adherable cover for burns and the like, comprising a facing layer of neutral thrombogenic reticulated open-cell foam material and a mutually secured coextensive gas-permeable microporous backing,

the facing layer serving as a receptacle for debris and liquid exudate when applied to the body for an extended period and being sufficiently thin and sufficiently small celled when so applied as to maintain any such debris and exudate in close proximity to the body for phagocytic invasion and to promote rapid coagulation,

the backing being non absorbent and impermeable to liquids and being impermeable to bacteria whereby the dressing when applied to the body serves to conserve vital body fluids, facilitate thrombogenic coagulation, confine any such debris and exudate, and expose confined bacteria to phagocytic invasion.

2. A surgical dressing according to claim 1 wherein the thickness of the facing is not more than about one-sixteenth of an inch.

3. A surgical dressing according to claim 1 wherein the foam material of the facing layer is a reticulated polyurethane foam.

4. A surgical dressing according to claim 1 wherein the foam material of the facing layer is 60-100 mesh reticulated polyurethane foam.

5. A surgical dressing according to claim 1 wherein the backing is a polyolefin film backing.

6. A surgical dressing according to claim 1 wherein the backing is a polypropylene film backing.

7. A surgical dressing according to claim 1 wherein the facing and backing are mutually secured by gas-permeable adhesive means.

8. A surgical dressing according to claim 1 wherein the backing is a microporous polypropylene film having open pores less than about 5.times.10.sup..sup.-4 mm. in dimension.