US 3422816 A
Description (OCR text may contain errors)
Jan. 21, 1969 RQBINSQN ETAL 3,422,816
SURGICAL DRESSING Filed Nqv. 12. 1965 United States Patent Us. 01. 128-296 Int. Cl. A61b 19/00,- 17/52 Claims ABSTRACT OF THE DISCLOSURE A surgical sponge that will cause a discernible change in a monitored electromagnetic field. The sponge contains a relatively flexible electromagnetic responsive element that comprises a plastic carrier and a nonradioactive magnetic material dispersed in the carrier.
This invention relates to surgical dressings used in the body such as the so-called surgical sponges used during surgical operations.
During surgery, it is a well known risk that surgical sponges or the like may accidentally be left behnd in the body. While, of course, every effort is made to prevent such accidents, it is desirable for some method to be provided for giving a final check to the patient just before he leaves the operating room to ascertain whether any sponges are remaining inside his body.
X-ray opaque elements have previously been inserted into surgical sponges in order that the presence of the sponges in the patient may be detected. Portable X-ray equipment has been brought into the operating room and an X-ray picture taken of the incision area prior to the closing of the incision in those cases where the sponge count indicates the possible leaving behind of a sponge.
In many cases it is undesirable to subject the patient to X-ray radiation. In addition, where X-ray opaque elements are used for sponge detection, it is frequently difficult to obtain a clear picture before the incision is closed. Since the patient, being still under the effects of anesthesia, cannot control his breathing, movement occurs which results in the blurring of the X-ray picture. This blurring often makes it difficult to distinguish the X-ray opaque element in the sponge from surrounding body bones and tissue.
According to this invention a surgical sponge is provided which, when inside the body, can be detected by electromagnetic detecting means thus eliminating the exposure of the patient to radiation. In addition, the patients breathing does not affect the certainty with which the sponge can be detected.
Specifically, the sponges contain a relatively flexible electromagnetic responsive element. The electromagnetic responsive element comprises a plastic carrier and a paramagnetic or ferromagnetic material dispersed in the plastic carrier. The surgical sponges thus provided produce a discernible changes in a monitored electromagnetic field when the sponge is placed in the electromagnetic field.
The inventive concept is best understood by reference to the following description and the accompanying drawings. In the drawings,
FIG. 1 is a plan view of a sheet of gauze containing an electromagnetic responsive element 11,
FIG. 2 is a view in perspective of a surgical sponge which has been obtained by folding the gauze sheet of FIG. 1 along the indicated fold lines 12,
FIG. 3 and FIG. 4 are views in perspective of other surgical sponges utilizing electromagnetic responsive inserts in accordance with this invention.
3,422,816 Patented Jan. 21, 1969 ice Each of the sponges illustrated in the drawings comprises an absorbent body .10 and an electromagnetic responsive element 11 of various shapes and sizes. By electromagnetic responsive element, it is meant an element which when placed in a primary electromagnetic field will temporarily or permanently become magnetized, thus causing a distortion in the primary electromagnetic field. Thus, if the primary electromagnetic field is of known intensity or is part of a tuned circuit, the existence of the electromagnetic responsive element in the electromagnetic field may easily be detected by the monitoring device.
The electromagnetic responsive element comprises a plastic carrier and a paramagnetic or ferromagnetic material dispersed therein. Paramagnetic and ferromagnetic materials are hereinafter collectively referred to as magnetic materials. By magnetic it is meant that the magnetic permeability of the material is greater than unity and thus the specific magnetic susceptibility of the material is positive. Magnetic materials become magnetized temporarily or permanently when placed in an electromagnetic field, thus causing a distortion of the field. The more highly magnetic a material is the greater is the distortion of an electromagnetic field caused by its presence in the electromagnetic field.
While all magnetic materials will distort an electromagnetic field when placed in the field, the particular magnetic material chosen should have a sufficiently high permeability and specific susceptibility that when the material is dispersed in the plastic carrier in the form of a very fine particles the overall composition will still have a sufficiently high permeability and specific susceptibility so the electromagnetic responsive element composed of carrier and finely divided and dispersed magnetic material can be detected when placed in a monitored electromagnetic field.
There are relatively few materials which have a magnetic permeability much greater than unity, especially in divided or powder form. Most magnetic materials have a permeability of between 1 and about 1.0001. Likewise, these same materials generally have a specific magnetic susceptibility of between 0 and about 1X10- While the use of these weakly magnetic materials is within the inventive concept, in order to be sure that the response of the electromagnetic field is not confused with a distortion caused by other slightly magnetic materials in the operative area, the magnetic materials used should preferably have a permeability somewhat greater than this. Iron, cobalt and nickel are particularly suitable for use in the dressings of the present invention since they are strongly magnetic. These metals in powdered form have a permeability of or more and a susceptibility of 4 or more when placed in an electromagnetic field of 20 gauss intensity. While the permeability and susceptibility of the salts of these metals are somewhat lower, the same being in the order of about 1.005 and 5() 1() respectively, they are still substantially more strongly magnetic than most other materials. From the standpoint of cost, ease of compounding and toxicity, the preferred magnetic materials are iron, such as iron filings, and iron oxide preferably in the form of ferric oxide or ferrosoferric oxide.
The electromagnetic responsive element in the surgical sponge must be nontoxic under the conditions of use. As the magnetic material is in finely divided form and dispersed in a carrier and will generally be completely coated with the carrier material it is important that the carrier be nontoxic. Numerous extrudable resinous materials are available which are suitable for the purpose.
The carrier used may be a natural or synthetic resin which has or may be compounded to have flexible or elastic rubber-like properties. Thermoplastic resins have the advantage that the electromagnetic responsive element can readily be bonded to the fibers of the sponge through heat and pressure. However, if thermoplastic resins are used they should have suificiently high softening points to withstand sterilization of the sponge. Particularly suitable carrier resins are polyisobutylene, vinyl acetate, vinyl chloride copolymers and polyvinyl chloride. The electromagnetic responsive elements can be molded, cast, extruded, drawn or formed in any one of a number of conventional ways.
The degree of distortion of the electromagnetic field depends not only on the permeability and susceptibility of the magnetic material dispersed in the plastic carrier, but also on the concentration of the magnetic material in the carrier. It is preferable to have a small element with a high concentration of magnetizable material rat-her than a large element with a low concentration of magnetizable material. This is true even though the larger element may have many times the absolute amount of magnetic material than the smaller element.
When iron or iron oxide is used as the magnetic material, good detection is obtained when the iron is present in an amount of about to about 90 parts by weight for every 100 parts of combined iron or iron oxide and carrier although the higher concentrations are preferred.
Referring to the drawings in FIGS. 1 and 2 the electromagnetic responsive element is in the form of a thin cylindrical monofilament 11, while in FIG. 3 the element is a thin tape 11A of magnetic material and carrier. A small thin circular sheet 11B is the electromagnetic detectable element of the sponge illustrated in FIG. 4. While the element may be of any shape, the maximum distortion of the primary electromagnetic field occurs when an electromagnetic responsive element having a given density of magnetic material per unit volume has its surface area minimized for a given uniform cross sectional area. Since a cylinder has the minimum surface area possible for a given uniform cross sectional area, a cylindrical monofilament is used in the preferred embodiments of the sponges of this invention. The thin monofilament is also preferred in that it does not substantially hnider the flexibility and absorbancy of the sponge.
The electromagnetic responsive element may be secured to the sponge by any appropriate method such as by stitching or sealing, the sealing being preferably affected by heat sealing. If the plastic carrier can be tackified by the use of a solvent, the filament may be wetted with the solvent and set in contact with the dressing. If solvent sealing is used, a solvent should be used which is highly volatile at room temperature and sufiiciently solvent for the carrier so as to make the surface of the latter fairly adhesive. The electromagnetic responsive element may be so applied that it is present in only a few of the gauze layers. However, it will most often be located in a multiplicity of the gauze layers.
The presence of the sponges of this invention can be detected by any one of a number of electromagnetic detection means which are capable of detecting small changes in an electromagnetic field. Needless to say, whatever detecting means are used the operating table or surface upon which the patient is reclining must be nonmetallic. Many types of electromagnetic detectors are well known in the art and any specific descriptions herein should not be interpreted as to in any way limit the scope of the invention. 7
A particular instrument used in the development of the present invention is the Lomar Metal Detector manufactured by the Lindar Automation Company of England. This detector contains a pair of tuned coils which detect the existence of the sponges of this invention when the recumbent patient is placed between the arms containing the two coils.
The following examples are given to illustrate the invention and should in no way be interpreted to circumscribe the scope thereof.
Example I A 20% solution of polyvinyl chloride/ polyvinyl acetate copolymer is prepared by dissolving 64 grams of the copolymer in 256 grams of warm tetrahydrofurane. 65 grams of this solution is then pasted with 20.7 grams of fine iron filing. The resulting paste is then poured into a flat bottomed dish and solvent allowed to evaporate overnight at a temperature of 100 F. The resulting film has an iron content of 60% by weight. The iron content per square inch of film is calculated to be 0.514 gram. Pieces are then cut from the film with the following areas: 9.74, 6.50, 4.88 and 3.25 square inches giving absolute iron contents of: 5.0, 3.34, 2.5 and 1.67 grams respectively. These pieces are then secured into 4" x 4" 32 ply sponges by stitching. All sponges so produced are detectable by the aforesaid Lomar Metal Detector.
Example II A 20% solution of polyvinyl chloride/ polyvinyl acetate copolymer in tetrahydrofurane is prepared as described above. grams of finely divided ferrosoferric oxide are then pasted with 100 grams of this solution. The resultant paste is then poured into a flat bottomed receiver and the solvent evaporated at a temperature of 100 F. This produces a film of 0.63 inch thickness containing 80% ferrosoferric oxide by weight. The film is then slit into widths of .0625 inch, .0738 inch and .0938 inch, all strips being cut to a length of 8 inches. These strips are then heat sealed into 4" x 4" 32 ply gauze sponges to give dressings with a ferrosoferric oxide content of 1.0, 1.25 and 1.5 grams respectively. All dressings are found to be detectable by the aforesaid Lomar Metal Detector.
Example III The procedure of Example II is repeated substituting ferric oxide for ferrosoferric oxide. The procedure is otherwise identical. The dressings produced are again detectable by the aforesaid Lomar Metal Detector.
Example IV The procedure of Example If is repeated substituting a plasticized polyvinyl chloride polymer for the polyvinyl chloride/ polyvinyl acetate copolymer. This material is cut into strips as previously described, but this material is also equally suitable for melt extrusion in the form of filaments or ribbon. Dressings produced are readily detectable by the aforesaid Lomar Metal Detector.
While the invention has been described with particular reference to specific embodiments, it is to be understood that it is not to be limited thereto but is to be construed broadly and restricted solely by the scope of the appended claims.
What is claimed:
1. A surgical sponge containing a relatively flexible electromagnetic responsive element, said electromagnetic responsive element comprising a plastic carrier and a nonradioactive magnetic material dispersed in said carrier, said magnetic material has a specific magnetic susceptibility of greater than about 1.0 10 and a magnetic permeability of greater than about 1.0001 and being chosen from the group of magnetic materials consisting of iron, cobalt, nickel and the salts of iron, cobalt and nickel, whereby a surgical sponge is provided which will cause a discernible change in a monitored electromagnetic field when the sponge is placed in said electromagnetic field.
2. The surgical sponge of claim 1 in which said magnetic material is a ferrous material.
3. The surgical sponge of claim 2 in which said magnetic material is iron oxide.
4. The surgical sponge of claim 2 in which the magnetic material is present in the electromagnetic responsive element in an amount of from about 20 to about parts References Cited UNITED STATES PATENTS Speaker 128-15 Berman 128-1.4 10 Mesek 128-296 Riordan 128-296 6 3,074,406 1/1963 Numerof et a1. 128-296 3,097,649 7/1963 Gray 128-296 3,133,538 5/1964 Pratt et a1 128-296 FOREIGN PATENTS 333,980 8/1930 Great Britain.
884,143 12/ 1961 Great Britain.
229,962 3/ 1959 Australia.
CHARLES F. ROSENBAUM, Primary Examiner.
US. Cl. X.R. 128-13