NO752465L - - Google Patents

Description

A main problem in vascular surgery is to ensure the supply of blood to organs and tissues where the blood vessels are poor or insufficient either as a result of congenital defects or acquired conditions such as injuries, atherosclerosis or other diseases. Initially homografts from arteries were used to restore blood flow in these organs but limited supply, insufficient size selection, development of<*>aneurysm and atherosclerosis made it necessary to look for a better substitute.

Artificial grafts in the form of porous, flexible

plastic sheeting has been made, but these suffer from the following defects:

1. Infection in a graft from a foreign body is catastrophic and often leads to bleeding, septicemia and death. 2. The lining in these grafts is thrombosis-forming and predisposed to blood clotting and subsequent blood clots in distant areas of the organism. 3. Such cloth grafts are stiff and often lead

to twisting and looping, especially in areas where they cross a joint.

k. Due to difficulties with blood clotting vii artificial grafts of smaller caliber often be a poor solution.

Other types of grafts that have been tried with greater or lesser success are heterografts from guinea pigs, collagen tubes formed inside the recipient patient, venous arches in the foot, knee and thigh (saphenous veins) both as auto-grafts where the patient is a donor and allo- transplant or homo-transplant where another person is the donor. These various substitutes are also plagued with problems of difficult delivery, small size, uneven size, long collection time, vein flaps, tendency to twist leading to clogging and narrowing in the wrong direction. The latter problem is particularly acute when saphenous veins are used since the veins must be reversed with regard to the direction of blood flow when they replace arteries. In light of these difficulties, it is obvious that there is a great need for a vascular prosthesis which is without the above problems. Furthermore, it would be highly desirable if such prostheses could be stored and kept available in many different sizes and shapes that were immediately usable.

The human umbilical cord consists of structures

which can be used as grafts in vascular systems or other fluid-carrying channels in mammals including humans. The umbilical cord contains a vein and two arteries, surrounded by ¥harton's jelly. Both the arteries and the vein are suitable for use as surgical materials. Compound transplants and area transplants can be done in different sizes and shapes.

Arteries and veins from the umbilical cord can be used fresh or as stored homo-graft, either in frozen-late or chemically preserved form. Treatment with antibiotics or other sterilization agents can be carried out. Although the antigenic effect of the proposed grafts is small, enzyme treatments can be carried out to remove any antigenic substances.

Usually the umbilical cord is somewhat spirally twisted and the arteries twisted around the vein. Accordingly, mechanical or chemical methods of straightening the veins and arteries may be necessary.

When preparing the vein and arteries for use, the aforementioned Wharton's gel can be removed either manually or by flushing with saline solution. A sleeve, which can optionally be specially shaped, preferably conical, can be introduced into the vein, after which the vein and arteries can be dissected in a simple way out of the umbilical cord itself. As mentioned, the vein or arteries can be used fresh or frozen. In addition, a hardening treatment such as aldehyde is used to stiffen the material and an advantage of this treatment is that the hardened part will retain its sleeve shape. Glutaraldehyde is a preferred curing agent. Before using such a hardened graft part, traces of glutaraldehyde are removed by treatment with suitable chemical reagents, preferably glutamic acid. It has been found that such treatment with curing agent or tanning mite egg and a reagent that removes remaining residues of the curing agent gives a product with low antigen and thrombogenic effect.

The advantages of using umbilical cord vessels in fresh or preserved condition as vessel conduits or area reinforcement are the following:

1. They can be easily obtained.

2. They are very flexible with no tendency to curl.

3. They carried considerable strength, especially vessels of smaller size

diameter.

k. The tubs are very smooth with a natural inner lining

with an extremely low blood clotting tendency.

5. They have little tendency to become infected.

6. Low antigenic effect.

7. Adjustable diameter.

8. Size selection possible for both larger and smaller vessels. 9. Sufficient length for practically all purposes. 10. Possibility of adaptation to many forms, i.a. narrowing and curvilinear shapes. 11. Compatibility with an outer support layer in the form of a network for strengthening larger vessels to be used in connection with arteries.

12. Application as a coating for accelerated healing

of surface damage such as wounds and burns.

Accordingly, it is an object of the present invention to provide improved material for use as vascular prostheses, reinforcement for organs, in the form of patches, for strengthening anastomosis (establishment of connection between two vascular organs or two separate structures) and for accelerated healing of surface injuries .

Another feature of the invention is a method for using veins and arteries from the umbilical cord, for surgical purposes.

Another feature of the invention is a method for forming veins and arteries from an umbilical cord, in preparation for use in surgical operations.

An important aspect of the present invention consists in a method for preparing and preserving veins and arteries from umbilical cords so that they can be stored and be ready for use for surgical operations.

Furthermore, an important feature according to the invention consists of a material in the form of a tube or patch preparation from veins and arteries originating from umbilical cords, which material has a low antigenic and thrombogenic effect and is highly resistant to infection.

The invention will be explained in the following by reference to the attached drawings where: fig. 1 perspective shows an umbilical cord before treatment,

fig. 2 is a section through a tube-vessel from an umbilical cord on a cylindrical sleeve,

fig. 3 shows, partially in section, an umbilical tube vessel pressed hydraulically against the walls of an outer mold,

fig. h is a section through an umbilical vessel on a conically tapering cylinder,

fig. 5 shows in perspective a patch part of an umbilical cord,

fig. 6 shows, seen from the side, a vessel reinforced in a vessel seam with a portion in the form of a patch,

fig. 7 shows in average an anastamosis-reinforced with

a party in the form of a strip and

fig. 8 shows in perspective an eyeball where the attachment part for the retina to the inside of the eyeball is reinforced with an eye loop in the form of a band of umbilical cord vessels according to the present invention.

The following example illustrates the technique of vascular surgical insertion of an umbilical cord vessel taken from humans into the abdominal aorta of an animal. The animal, in this case a baboon, was given total sterile anesthesia in preparation for an abdominal incision. The baboon was shaved and a longitudinal incision made along the midline of the abdomen. The incision extended from the xytoid area to the pubic area, down through the midline and into the abdominal cavity. Bleeding veins were ligated with 3x0 polyglycolic acid suture. The abdominal cavity was entered and the viscera and intestine were explored to find other diseases. The animal was found to be normal. The intestine and viscera were clamped aside and the peritoneum over the aorta was cut through and the aorta retained by sharp and pointed dissection. The lumbar arteries were each

simply clamped and tied with 3-0 silk suture so that it parti

of the peritoneal aorta extending from the internal renal arteries to the aortic bifurcation was retained. The entire segment of the peritoneal aorta was thus available for transplantation with the umbilical cord. While preparing the baboon's abdominal aorta, another researcher had taken the umbilical cord from a child (human) born two hours earlier. The umbilical cord was taken in its entirety and transported in sterile saline packed in ice. The purpose of freezing the umbilical cord in ice was to prevent further degradation of the umbilical cord's structure. Before use, the umbilical cord was washed and drained several times with sterile Collins solution containing antibiotics, in this case 1$ cephalosporin solution and 25,000 units of baeitracin per 1 resolution. The blood was thoroughly washed out of the umbilical cord blood vessels and the cord flushed with 1% anticoagulant heparin solution. After this thorough cleaning of the umbilical cord, one end of the umbilical vein in the cord to be used as a graft was clamped and through the other end a red rubber catheter, type French catheter No. 14, was inserted, and the vein was pulled loose. At this point, a suitable part of the umbilical cord graft, with a length of approx. 5 cm, selected for carving. A sleeve was placed in the vein and the rest of the string was cut away. The vein segment was handled sterilely and placed in the operating field. At this point, the animal was given heparin in an amount of 2500 units of aqueous heparin, intravenously. The abdominal aorta was clamped proximal and distal to the segment that was selected. A lot with a length of approx.

3 cm was cut loose from the abdominal aorta and a vessel ligation was performed end to end between the patient's aorta and the donor's umbilical vein, first using a continuous 6-0 Prolene suture, which is a nylon single-thread suture. The distal vessel ligation was performed and the aorta then flushed to remove clotted blood and other matter. After this anastamosis, the distal and proximal clamps were removed. No bleeding was observed between the suture stitches, which is unusual, and this is assumed to be due to the strength and self-sealing property of the gelatinous umbilical cord structure. Outstanding blood pulse took place 1 the graft and in distal pelvic arteries. The area was washed with salt water and vacuumed clean. The retroperitoneum was closed with clipped 3-0 polyglycolic acid suture and the viscera reinserted. During this phase, the animal had been stable, breathing and vital signs normal. The peritoneum wall was closed in layers with continuous O-silk for the posterior fascia and peritoneum and cut open 2-0 silk suture for the anterior fascia. The skin incision was sutured together with continuous 3-0 nylon suture. Nembu-tal anesthesia was used. The estimated blood loss was approx. 50 to 75 ml. The animal tolerated the procedure well and woke up after 30 minutes. Post-operatively on the following day the animal was able to sit and walk in the cage and on the third day after the operation it was eating normal food and was released from the cage and was running around and climbing up and down the walls, in general it seemed to be in excellent shape. The legs were warm and the pulse intact in the extremities.

Many different applications and techniques will then appear to professionals. If desired or necessary, the umbilical vein or artery can be cut lengthwise and assembled into segments of larger diameter. The umbilical cord vessel or part of it, in fresh or hardened (tanned) condition, can be used to strengthen, support or close a weakened area or a defective part of body organs such as the heart, heart valves or urinary bladder, or to cover a surface wounds to accelerate healing under the patch. Such methods are covered by the present invention.

Before the blood vessels are taken out of the umbilical cord, they, especially the vein, appear to be almost closed and rather small, as can be seen from fig. 1 which on an enlarged scale and in perspective shows a part of the umbilical cord. The umbilical vein has the reference number 11 and the arteries the reference number 12. These veins are surrounded by ¥harton's gel as previously mentioned. Furthermore, the arteries 12 are twisted around the vein 11 and also contain Hoboken valves. These are some of the factors that made it remote to use these blood vessels as vascular grafts. It has already been mentioned that inserting a sleeve 1 into the vein 11 facilitates the removal of the rest of the umbilical cord. However, the arteries 12 can also be carefully dissected from the umbilical cord and threaded onto sleeves. When this is done and the veins are properly cured or tanned, the Hoboken flaps are eliminated and vessels less than 1 mm internal diameter can be easily fabricated and permanently shaped using a suitable curing solution. The umbilical vein is significantly larger than the arteries and can be stretched

a sleeve so that you can produce vessels up to 1 cm in inner diameter. Such vessels can of course be cut open and laid out flat, and in this state they are suitable as patches for strengthening

organs, supplementation of tube dressings and coating of surface lesions.

After having dissected out the desired vessel or vessels and cleaned them and removed residual blood and the like, they are cured for several minutes with a curing agent, preferably 3-10 minutes. This step causes a partial removal of the Hoboken flaps

from the arteries. The most*suitable hardener is aldehydes. Examples are formaldehyde, glyoxal, dialdehyde-starch and glutaraldehyde*, where glutaraldehyde is best with regard to the elimination of all traces of antigenic and thrombogenic effects and with regard to ease of processing, and a solution of dialdehyde-starch is second best. The concentration of the glutaraldehyde solution should be between approx. 0.15 and 0.7$» The concentration of the dialdehyde starch should be between approx. 0.5 and 2.0 wt-$. At lower concentrations, the glutaraldehyde solution does not make the material in question antigenic, while at higher concentrations the reaction is too fast and makes the vessel wall brittle.

After filling the container with hardening solution, the blood vessel is pulled onto a sleeve of suitable shape and size. The vessel on the sleeve is placed in a container (not shown) containing hardening solution for approx. 15 to 45 minutes and during this time the blood vessel forms into the shape of the sleeve. A preferred solution for hardening the blood vessel is 0.5% glutaraldehyde buffered with 1% sodium bicarbonate to a pH of between 7"5 and 8.5". A vein 11 is shown on a cylindrical sleeve 15 in fig. 2.

Another method for shaping the blood vessel appears in fig. 3 where a vein 11 is led into a tube 18 and the end 19 of the vein 11 is closed with a cork 21. The other end 22 of the vein is connected to a hose 23 for introducing curing solution 16 under moderate pressure. The pressure of the curing solution presses the vein 11 against the inside of the forming tube 18 so that the blood vessel takes a corresponding shape. In this way, you get a vessel with a smooth exterior.

The method of crimping a vein or artery on a cylindrical sleeve or core 15 as shown in fig. 2 or a conically tapering sleeve 25 as shown in fig. 4, has the advantage that any internal irregularities such as Hoboken valves are eliminated, and reference numeral 24 shows a blood vessel portion which can be either a vein or an artery. Small-diameter arteries are particularly suitable and of great value as substitutes for blood vessels in the body. In this context, umbilical cords from larger mammals, although these cannot be obtained as easily as from humans, will contain larger blood vessels so that larger and thicker-walled vessels and lobes can be obtained from this source. In the same way, smaller mammals will give vessels with a smaller diameter, as such blood vessels may be necessary for special applications such as e.g. in fingers and toes.

It should be mentioned that when using segments treated as indicated according to the invention as arteries smaller than approx. 2 mm inner diameter, reinforcement with artificial mesh is unnecessary.

This is not only because pipes with a smaller diameter can withstand higher pressure in general, but also because during compression of the blood vessels the wall thickness will increase. Immersing the blood vessel in alcohol before the aldehyde treatment results in a stiffer blood vessel.

After curing the blood vessel, it is due to remove most of the curing agent. One can use a l$-ug NaHCO^ solution. It is then beneficial to treat the blood vessel for 30 to 5 minutes with a compound that reacts with the remaining aldehyde. Suitable compounds are amino acids, their alkali salts, as well as oxidizers in diluted form such as peroxides, peracids and hypochlorites. Amino acids such as sodium salts, preferably L-sodium glutamate, L-netrulalanine, L-sodium phenylalanine and L-cysteine are particularly suitable for this purpose because they are antithrombogenic, the best of the above compounds being the glutamate. The mechanism is believed to depend on condensation of the amino groups in the amino acid at the aldehyde's carbonyl group. This means that the carboxyl group on the condensate is free to ionize and transfer a negative charge to the surface of the blood vessel. Negatively charged surfaces are known to be antithrombogenic.

Although the preferred method for storage after curing and shaping the blood vessel is in a dilute solution of an aldehyde, it is an advantage to treat the blood vessel with an amino acid after curing, to remove aldehyde as indicated above.

A suitable storage method for cured vessel segments is a dilute solution of aldehyde, preferably 0.5% glutaraldehyde. Some further hardening of the segments takes place within k to 6 days. However, the degree of curing during storage is low and can easily be taken into account in the main curing step.

When preparing for transplantation, after storage, the pigment is rinsed in e.g. sterile saline or l$-ig NaHC^ solution. The segment is preferably re-treated with sodium L-glutamate or one of the aforementioned compounds to remove residual aldehyde.

An alternative storage method is storage in a solution of kO to 50% aqueous alcohol containing approx. 1$ propylene oxide. Treatment of segments stored in this way with aldehyde-removing reagent is of course unnecessary.

As will be appreciated, a large number of variations of the proposed methods are possible. After thus flushing out the vein from the umbilical cord, a mandrel or sleeve, either conical or straight, can be inserted into the vein, the cord can be frozen, the sleeve can be clamped in a drill holder and all components other than the vein are turned away in a lathe. With such a method, the outside of the vein can be turned so that the wall thickness is uniform or possibly tapered if desired. As expected, the blood vessel or segment must be sterilized after undergoing this treatment. Common non-destructive methods such as irradiation, treatment with antibiotics or heating are used. A temperature increase of up to 60°C during the curing or tanning reaction will also increase the curing rate. The same technique can be used to remove residual hardener.

Another variation is to split the vein and unfold it flat. Use of a flattened core facilitates the production of such flat segments. The blood vessel can then be cut into segments of the type 20, of any size, as shown in fig. 5" and the segments can be used as reinforcing tensile structures or patches. An application for such a patch is shown in fig. 6 where a vessel 26, which may be a portion of an intestine which is sewn together forming a seam 27 with the stitches 28. This repair of the vessel 26 can be reinforced by placing a portion 29 as a patch over the seam 27 and sewing the patch fixed on the vessel 26.

The function of such a patch is more extensive than just a reinforcement. When suturing wall parts from body organs, it is known that it is necessary that the stitches are not pulled too tightly and that the stitches are not too tight either, otherwise there is a risk that the blood supply to the organ wall can be cut off, resulting in gangrene. Using normal methods, you will thus easily be able to get leakage through the wall's suture seam. For this reason, drainage pipes are so often used. Reinforcement of the seam with a patch as shown in fig. 6 will substantially reduce this risk.

Another application of a segment produced according to the present invention is shown in fig. 7 which shows anastamosis in an intestine Jl, According to normal surgical practice, the two ends 32 and 33 of the intestine 31 are turned inward and the ends are sewn together with the stitches 34. Then a band 36 is sewn around the joint between the intestinal ends 32 and 33 so that one eliminates or in greatly reduces the risk of intestinal contents leaking into the abdominal cavity. It goes without saying that although fig. 7 shows only a single layer of the vessel material around the intestine, two or more layers can be used.

Several parts or segments can be used for certain designs such as e.g. lining of the heart's pericardium or a heart valve or to cover an artificial organ such as a "pacemaker". Segments can also be used for plastic surgery and as an internal reconstruction material.

Although the tensile strength of a hardened vessel of the aforementioned type is only moderate, the treated vessels have other characteristics that make it very well suited for surgical use. These characteristic features are the aforementioned lack of antigenic and thrombogenic effects and flexibility, smoothness and complete compatibility with the body's organs and vessels.

There are many different surgical interventions. whereby such vessel segments can be used with great advantage. It has already been mentioned that a segment can be used to reinforce a seam and for anastamosis. The vessel segments can also be used to strengthen weak parts or defects in the wall of an organ such as, for example. the urinary bladder. A part can be shaped as an artificial channel between the urinary bladder and the skin. A very important application is as an eye band around the retina. The need for such a strap arises during surgery to repair a damaged retina. The manner in which such an eyeball strap is used appears in fig. 8 where the reference number 47 generally shows the eyeball. The pupil 48 in the eyeball is shown at 4.7©r and the area where the operation has been performed surgically shown at 49» The repaired area must be kept under pressure until the retina has permanently attached to the eyeball. For this purpose, a band 51 is wrapped around the eyeball so that the eyeball is pressed against the inner retina. This usually requires the internal pressure of the eyeball to be increased by approx. 30 mm mercury. Until now, retina eye straps have been made of silicone plastic or fascia lata.

The first will be able to injure the eyeball and cause infection. A certain proportion of such interventions will therefore fail and in these cases the patient may become blind. Using the fascia lata, on the other hand, requires a prior operation to release this material. A manufactured segment according to the present invention will remove these difficulties. The segment is completely compatible with the body and has no tendency to wear on or injure the eyeball.

Another important application for flaps taken from an umbilical cord blood vessel is in connection with skin transplantation.

A patch can be placed in position over a burned or injured area, also during infection. In many cases, no dressing is necessary as the patch fastens. Healing takes place quickly under the patch, including elimination of the underlying infection without the need for the usual changing of wound dressings. The applied patch will peel off when healing has progressed sufficiently. It is of the utmost importance that such skin grafts will remain in place for several months while healing takes place.

The use of umbilical cord vessels, whether from humans or other mammals, will, as can be seen from the above, have many advantages. The supply is unlimited and the treatment required to make the blood vessels suitable for surgical use is simple. There are also many variations to meet special and varied needs. Therefore, sterile umbilical cord segments can be produced in large quantities and relatively cheaply. They can be stored for an unlimited time and in different shapes and thicknesses to meet every practical need. If stored in dilute glutaraldehyde solution, they only need to be rinsed in sterile water or saline or dilute NaHCO^ before use. If desired, they can be further rinsed in sodium L-glutamate to remove residual aldehyde.

When preparing with regard to hardening (tanning) and shaping, cleaning or rinsing solutions can be passed through the vein or artery in the umbilical cord, as the solutions can consist of water, sterile saline, Ringer<»>'s lactate solution, hydrogen peroxide solution, sodium bicarbonate solution, alcohol and transplant perfusate solutions. Antithrombogenic agents that can be used to treat the graft include L-sodium glutamate, L-alanine, L-phenylalanine, L-cysteine and L-lysine. These compounds are also suitable for treating vessel segments after curing to remove remaining curing residues.

¥harton<*>'s gel around the umbilical cord can be removed mechanically or chemically with hyaluronidase to dissolve the hyaluronic acid of which the gel is made. Incidentally, salt water solution is also effective for this purpose.

The mentioned sleeves or cores for forming the vessels can be made of glass, silicone plastic, stainless steel or other substances that are unreactive towards the graft vessel and the chemicals used in the process* The sleeve can be straight or chrome, compact or hollow, cylindrical or conically tapered and smooth or rough on the surface, according to practical needs.

Among aldehydes suitable as curing or tanning agents are glutaraldehyde, dialdehyde starch and formaldehyde as well as anhydrous alcohol, glyoxal and chromium oxide.

In addition to the above-mentioned amino acids suitable for removing aldehyde residues, weak oxidation agents can also be effective. Examples of such are diluted hypochlorite solution and diluted peroxide.

Especially when large vessels are to be used, especially those over approx. 5 atm internal diameter, it is desirable to reinforce the blood vessel. Usually, the blood vessel is reinforced using an outer coating of mesh material. Both polyesters and carbon fluoride plasters can be used, the former being preferred. Marketed "Mersilene" cloth with a large mesh width (O.5-2.0 mm) can be wrapped around the blood vessel to give the graft greater strength, as the cloth will be pressed down into the graft's outer wall. A preferred fabric form is a pre-formed sleeve.

Graft reinforced with cloth can be tested for leaks and strength by placing it in a pulse machine and circulating solution through the machine at a pressure of 150 to 300 mm Hg.

Claims (12)

1. Flexible part of a mammalian umbilical cord vessel for use as a prosthesis in mammals, free of antigen and thrombogenic effect. 2. Flexible part as specified in claim 1, characterized in that said vessel which is used as a prosthesis lies inside 1 the umbilical cord. 3. Flexible part as specified in claim 1, characterized in that it is in a shaped and hardened state. 4. Flexible part as stated in claim 1, characterized in that it is tubular and reinforced with flexible, open-mesh fabric around the tube. 5« Method for producing a flexible part of an umbilical cord for. use as a prosthesis, according to claim 1, characterized in that one (a) separates and removes at least one of the main blood vessels from an umbilical cord; (b) stiffens (hardens) the blood vessel using a chemical reagent, (c) shapes the vessel. 6. Method as stated in claim 5i, characterized in that said part is cured using one of the aldehydes: glutaraldehyde, formaldehyde, dialdehyde starch and glyoxal. 7. Method as set forth in claim 5" characterized in that said part is hardened by being brought into contact with a solution of glutaraldehyde with a concentration of 0.15 to 0.6% by weight, for a period of from 15 to 45 minutes. 8. Procedure as specified in claim 7"characterized by the fact that the following steps are also carried out: washing the aldehyde-treated part with water, saline or dilute sodium bicarbonate to remove the aldehyde, and then with a reagent that removes residual aldehyde, which reagent is an amino acid, an alkali salt of an amino acid, an amine, a hydro- sylamine, a peracid, a peroxide or a hypochlorite. 9" Method as stated in claim 5" characterized in that said part is also stored in a sterile, closed container. 10. Procedure for repairing, enlarging or replacing a vessel conductor or organ in the body by means of suture or in another way, characterized by a part of an umbilical cord vessel being fixed in or on the wall of the vessel conductor or organ. 11. Method as stated in claim 10, characterized in that said part of the umbilical cord is in a hardened and shaped state. 12. Method as stated in claim 10, characterized in that said part is tubular and reinforced with open mesh textile on the outside of the part.