US 3825007 A
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United States Patent 7 11 1 Crowe 156/148 g a r Rand July 23, 1974  PLEDGETS 3,399,671 9/1968 Satas 128/296 Inventor: Robe" w. Rand, 521 N Bristol 3,523,536 8/1970 Ruffo 128/296 1 Los Angeles Calif. 90049 Primary Examiner-George F. Lesmes Filed: 1972 Assistant Examiner-James J. Bell  Appl No; 216,077 Attorney, Agent, or Firm-Edward D. O'Brian 52 us. or 128/296, 117/140, 117/163, 1571 ABSTRACT 161/ 161/ 5, 161/410 A pledget" is disclosed which comprises a piece of Int. Cl. an absorbent fiberous material having a urface v- Field of Search 161/39, 160, ered by a covering of a flexible, resilient polymer ma- 161/170, 244, 410, 265; 117/140, 16 terial which extends over and around and into the in- 128/290 w, 296 terstices of the fibers at the surface of the piece of material. Such a structure can be created by contacting References Cited the surface with a layer of a latex of the polymer ma- UNITED STATES PATENTS terial for a sufficient period so that the liquid vehicle 2,339,562 1 1944 EUStlS 128/296 within the latex will be absorbed into the fibemus 21826643 4/1953 Knapp 128/296 terial, resulting in the formation of the covering on the 2,899,337 8/1959 Bird et a1... 128/296 fibers at the surface of the material, and then remov- 3,122,l40 I 2/1964 Crowe.... 156/148 ing the liquid vehicle from the material and from the 3,122,141 211964 Cl'0W6.... 156/148 covering 3,122,142 2/1964 Cr0we.... 156/148 3,156,242 2 Claims, 3 Drawing Figures 1 PLEDGETS BACKGROUND OF THE INVENTION The term pledget is primarily a medical term utilized to designate small, generally felt masses of absorbent fibers such as cotton fibers which are utilized in connection with various operations on living bodies and in various types of medical treatment procedures. A complete understanding of the use of these pledgets is unnecessary to an understanding of the present invention. Their use and their advantages and disadvantages are well established in the medical field. However, a brief review of their utilization is important in understanding the reasons for the present invention and how the present invention provides pledgets which are more desirable than various different known pledgets.
One utilization of pledgets is in various different brain and spinal cord operations. They are utilized in such operations to protect neural tissue as operations are continued, and so as to absorb fluids which might interfere with the operating procedures and treatments. As such operations are being finished the pledgets used are, of course, removed from the body where they are employed. Such removal of known pledgets has been acknowledged to cause problems and complications detrimentally affecting treatment.
This is best further explained by referring to known pledgets. Most generally, these structures have been pieces of pure, absorbent cotton felt. In many pledgets the fibers within a material of this type are chemically bonded to one another so as to give the felt a relatively high wet strength. In such structures the surface of the felt applied to living tissue contains various absorbent fibers. As a pledget is left in place such fibers will tend to be permeated by the fluid present and will tend to adhere to a degree to the body tissue contacted by the pledget. As a consequence of this when a pledget is removed there is a significant degree of danger of the tissue adhering to the pledget. Such adherence can be extremely detrimental. As an example of this, a pledget utilized in brain surgery may be utilized against the arachnoid in the brain. After such a known pledget has been left in place during an operation, it tends to adhere to a sufficient extent so that there is a danger of it producing a subarachnoid hemorrhage as it is lifted off the brain surface. In general, the longer a pledget is left in the place the more pronounced the adherence between it and the living tissue and the greater thepotential of damage when the pledget is removed.
A recognition of the danger of such damage has lead to various proposed solutions to minimize such damage. As an example of one such proposed solution it has been common for surgeons such as neurosurgeons to attempt to facilitate the release of pledgets from tissue contacted by the pledgets by liberally applying a physiological saline solution to the regions where the pledgets are utilized. This type of procedure is considered to have obvious disadvantages growing out of the fact that an extra step the irrigation is necessary with it and growing out of the obvious disadvantages of the use of significant amounts of saline solution.
Another proposed solution to the problem of pledget adherence has involved the utilization of a release strip or layer on one side of a conventional pledget. It is considered that in all cases where this procedure has been attempted, the release strip has been a sheet of rubber, serving essentially as a dam tending to hold back the pledget so that it both will not stick to body tissue and also so as to isolate the pledget so that it'cannot do the effective job of absorbing fluid. Procedures of this type are considered to be disadvantageous because of prob lem of pledgets not fitting the sheets of release material used and/or tending to move to one side or another off of such sheets. Whenever this occurs there is of course danger of adherence.
SUMMARY OF THE INVENTION It is an intention of the present invention to provide pledgets which eliminate this danger of adherence and yet which still retain the desired ability to absorb fluids present. From this it will be seen that in effect a broad objective of the present invention is to provide new and improved pledgets. To avoid confusion it is to be understood that such pledgets are sometimes referred to by other names than-the specific term pledgets." At
times they are referred to as a type of surgical sponge" and occasionally they are designated as neuro sponges or patty.
Another broad objective of the present invention is to provide new and improved procedures for producing pledgets. In connection with this it is an objective of sepresent invention to provide a procdure as indicated which may be easily and conveniently carried out at a comparatively nominal cost utilizing inexpensive equipmenLA related objective of the invention is to provide pledgets as produced by this procedure which not only are effective, but which are also comparatively nominal in cost. 21
In accordance with this invention these and various other objectives of the present invention are achieved by the production of pledgets comprising a piece of absorbent, fiberous material having a surface covered by a cover of a flexible, resilient polymer material extending around, over and into the interstices of the fibers at this surface of the piece of material through the steps of contacting a surface of a piece of such material with a latex of a polymer material for a sufficient period so that the contact results in the liquid vehicle being absorbed into the fiberous material at the surface so as to form this covering and then removing the liquid vehicle from both the material and the covering.
BRIEF DESCRIPTION OF THE DRAWING A summary of this type is inherently incapable of indicating many important features and aspects of an invention. Items of this type will be apparent from a detailed consideration of the remainder of this specification, the appended claims and the accompanying drawing in which:
FIG. 1 indicates in a diagrammatic manner an initial step in creating a pledget in accordance with this invention;
FIG. 2 indicates in a diagrammatic manner a second step in creating such a pledget; and
FIG. 3 indicates in a diagrammatic manner a final step in creating this product.
For the purpose of clarifying the nature of the invention it is to be specifically noted that the accompanying drawing does not indicate the invention per se since the invention involves intangible concepts as are set forth and defined in the appended claims. The accompanying drawing is primarily intended for explanatory purposes in indicating the natureof a presently preferred pledget in accordance with the invention and a manner of making such a pledget. Y
DETAILED DESCRIPTION In accordance with this invention a pledget is formed utilizing a latex of a flexible, resilient polymer material. Where a pledget is intended to be utilized within a living body or in contact with living tissue, to avoid toxic effects it is considered necessary to utilize a polymer material which is inert or substantially inert with respect to the body and living tissue. To avoid the danger of the pledget causing damage the particular polymer material utilized should be flexible so as to be capable of conforming to particular tissue against which a pledget is to be utilized. The polymer materials should also be somewhat resilient or at least to a degree rubber-like in character so as to minimize the chances of the polymer material becoming damaged during the handling and use'of the pledget. I
A latex of any such polymer material is utilized in order to facilitate the application to a piece of fiberous, absorbent material as hereinafter indicated of the polymer material so that ultimately the polymer material will form a cover extending over and around fibers in the piece'and will extend into the interstices of such fibersqTo avoid question the term latex is used here to designate a collodial dispersion or a nearly collodial dispersion of a polymer material as indicated in a liquid vehicle-Normally such a vehicle is water, but on occasion other liquid carriers can be utilized for comparatively or fine particles of polymer material.
For best results in avoiding stratification or settling the latex it is considered that the particles within such a latex should be of no greater size than about microris in diameter. If desired, a latex to be used with this invention can include secondary agents such as known dispersing agents, emulsifying agents, stablizers, thickeners and wetting agents in amounts as are conventional in the latex industry. Such agents and the amounts of them which are commonly used are well established in the latex industry.
Further information relative to latices is foundin a number of different texts. In this connection reference is made to the text, Rubber Technology by Morton, published by the Reinhold Publishing Corp., N.Y., 1959, pages 441 to 454, inclusive. The disclosures of these pages of this text are incorporated herein by reference for the purpose of supplementing this disclosure.
One of the most common polymer materials easily obtained in the form of a latex and possessing the physical properties indicated in the preceding is natural rubber. As supplied for use a latex of this material contains particles referred to as gel and sol rubber particles varying in size from between about 0.1 to about 2microns. A normal rubber latex as sold for use will contain' from about 60 to about 70 percent by weight solids in a water vehicle, and will contain minor amounts of ammonia serving as a stablizer. A natural rubber latex of this type is preferably employed with the invention because of its availability, its cost and the physical properties of the rubber material itself.
Within the broad scope of the present invention it is possible to utilize latices 'of other materials such as butadiene-styrene latices, nitrile latices, polychloroprene latices and the like. The applicability of any such polymer material for use in a pledget of this invention will, of course, depend upon the inertness of the specific polymer material under the intended use of the specific pledget. Thus, for example, pledgets using a polymer material of a specific character or type may not be suitable for one use, and yet may be suitable for another ultimate application. So far as is now known, pledgets made utilizing natural rubber may be satisfactorily employed in any pledget application.
In general, a latex of any material as indicated should contain as high'a solids concentration as reasonably practical to obtain in order to facilitate the application of the polymer material to a piece of absorbent fiberous material in an amount necessary to accomplish a desired physical structure in an ultimate pledget of this invention. If the solids concentration is too high, the application of the latex will tend to be relatively difficult while if the solids concentration is too low the latex used may not completely cover fiber surfaces as hereinafter indicated.
Broadly it is considered that this objective can be achieved using a latex containing from about 20 to 80 percent by weight solids, but that the application of desired amounts of the polymer material is facilitated using a latex of from about 50 to about percent by weight of the polymer material. It is to be realized that these percentage ranges of latex concentrations are rough approximations inasmuch as because of inherent physical properties it is impossible to use exactly the same latex concentrations with all polymer materials. It is considered that the amounts given are rough approximations which will be sufficient to enable others to practice ,the invention with a minimum of difficulty.
.In the presently preferred manner of practicing the invention. a latex as indicated in the preceding discussion is sprayed so as to form a layer 10 of this latex on a surface 12 of a sheet 14 of an imporous material such as glass in much the way in which a coat of paint is sprayed upon a surface to receive such a coating. The thickness of the layer created in this manner is important to the physical properties of the ultimate pledget created, but is not critical in the sense that a certain temperature or a certain pH maybe critical in connection with various chemical reactions.
The layer formed should be a continuous layer with no obvious spaces containing only carrier between the particles so as to make sure that there will be solid polymer material opposite a piece of absorbent fiberous material 16 used in the second step in practicing the invention. It is considered that this layer 10 should, however, be sufficiently thin so that it will not run off of the sheet 14 when this sheet 14 is tilted at an angle to the horizontal. In other words, the layer 10 should be sufficiently thin so that it willnot run like paint will run when applied in too great a quantity for all of it to adhere toa surface.
If more than this amount of latex material is utilized it is considered that in general the surface of a pledget produced will tend to unnecessarily imporous. While for some applications this may not be critical, for others it is considered to be relatively important. Because of the variations in polymer materials and latices of such materials these limitations are not to be considered absolute in a physical sense. They are indicated herein primarily to facilitate a clear understanding as to how to practice the present invention. In general, the thickness referred to corresponds to thicknesses corresponding to these of from about one sheet to about four sheets of common bond paper.
Once a layer such as the layer has been created the next step is to apply a piece of material such as the piece 16 to this layer. This piece 16 may conveniently be formed of any known fiberous material such as is commonly utilized in forming pledgets. Because of absorbency and physical strength it is, however, considered preferable that this piece 16 be of a cotton felt of a high wet strength character having individual fibers within the felt bonded together by a known resinous material in accordance with established techniques.
As the piece 16 is applied, the surface 18 of this piece is preferably layed upon the layer 10 so as to not to physically disrupt or mop this layer in order to disturb its uniform character. As this occurs the liquid vehicle in the latex will tend to be absorbed into the fibers exposed at this surface 18 so as to form a covering extending over and around these fibers into the interstices of them. This is essentially a physical process and the time that it will require will depend upon a number of factors such as'the nature of the liquid vehicle, the amount of the vehicle present in the latex used, the absorption characteristics of the fibers for this vehicle and the like. When as preferred a natural rubber latex is used, in general satisfactory results can be achieved in a period of from about 10 minutes to about 1 hour, and this period can be shortened to within the lower end of this range by coupling the period allowed for this absorption with the removal of the, liquid vehicle used.
Thus, for example, a piece 16 located against a layer 10 of a commercial latex as described containing about 62 percent by weight natural rubber solids may, immediately after the application of the piece 16 be inserted into a drying oven such as an oven at 200 F. for a period of from about to minutes or until it is determined that a change is taking place within the polymer material. This will remove the liquid vehicle from within the piece 16 and a covering 20 of the character previously indicated is created from within the material of the layer 10 by the absorption of this vehicle. In most cases this vehicle may also be removed by simple air drying or the like techniques which will result in vehicle evaporation.
After removal of the vehicle in the latex a final ultimate pledget 22 in accordance with this invention may be obtained by the simple steps as indicated in FIG. 3 of the drawing of pulling up the edge of the piece 16 and blowing the pledget 22 off of this sheet through the use of a compressed air gun. The pledget 22 obtained in this manner can be cut to any desired size or shape using a conventional cutting instrument so as to be ready to use.
In the event a pledget such as the pledget 22 is created using a polymer system such as an elastomer system, which because of its physical characteristics and- /or its ultimate utilization should be physically stronger than is normally considered necessary, the latex used in forming this pledget may contain one or more vulcanizing agents, cure activators and/or accelerators in accordance with conventional practice. When such materials are used it is considered preferable that a pledget produced as described be treated under conventional vulcanizing conditions so as to develop the final physical properties desired in a polymer composition used. At times this can be accomplished concurrently with the removal of the liquid vehicle.
In a pledget of the invention such as the pledget 22 the necessary physical properties desired are essentially related to a physical blocking off of the exposed surfaces of the fibers at the surface 18 of the piece 16 so that they cannot contact tissue or tissue-like materials so as to tend to adhere to the same. When a pledget 22 is created as described the polymer material forms a covering which extends over and around the fibers of the piece 16 and into the interstices of such fibers which are exposed to or adjacent to the surface 18 so as to penetrate such a surface to a sufficient extent to isolate the piece 16 from whatever is contacted by the pledget 22 as it is used.
This action is accomplished in a pledget such as the pledget 22 without forming a film which will destroy the porosity of the pledget 22 when it is created as described in the preceding discussion. Normally such porosity is important in obtaining a desired absorbent action during the use of a pledget such as the pledget 22.
If for any reason a completely imporous covering 20 is desired, such a covering may be obtained by continuously repeating the process steps indicated in the preceding discussion.
These same process steps can be carried out in various different ways which will be apparent to those in the coating art on the basis of the disclosure embodied within this specification. Thus, for example, the sheet 14 utilized is essentially employed as a means of applying the layer 10 to the piece 16. Other known substantially equivalent or related application procedures can be used instead of the precise procedure herein indicated to apply a layer as described to a surface of a piece of material such as the piece 16.
1. A pledget which comprises:
a piece of an absorbant, fibrous material in which the fibers are prebonded together having surfaces, one of said surfaces being covered by a covering of a continuous, porous, flexible, resilient, elastomeric polymer material which is inert with respect to living tissue, said polymer material in said covering extending over, around and into the interstices of the fibers of said pieceadjacent to said surface so as to physically block off the exposed surfaces of said fibers at said surface so that said piece is isolated from anything contacting said surface.
2. A pledget as claimed in claim 1 wherein:
said absorbent, fiberous material is cotton felt, said polymer material is natural rubber and said covering is porous so as to permit the absorption of fluids by said piece through said covering.