25, 122- 128 (1978)


C. WILLIAM HALL, M.D.,* *Institute Medical Scientist, tDepartment of Pathology,

Cannula AND


Construction1 J. GHIDONI, M.D.-F

Southwest Research Institute, P. 0. Drawer 28510, San Antonio, Texas 78284, and The University of Texas Medical School at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78229 Submitted

for publication

The thoracic and abdominal cavities have two well-defined needs for a percutaneous cannula: (1) the requirement to transmit power to implanted artificial hearts and heart-assist devices and (2) the requirement to permit peritoneal dialysis. Both of these applications require long-term (in excess of 2 years) retention of the cannula’s position. Successful applications have demonstrated the relative ease of interfacing nonviable, woven fabrics to mesodermal tissues (vascular grafts) because the interface retains dimensional stability. However, endodermal and ectodermal tissue surfaces characteristically undergo a maturation process that produces cellular migration toward the surface, with subsequent death and sloughing of the detritus, creating dimensional instability of any inter-facial bond that has been attained. Skin is of ectodermal origin and is, therefore, affected by this process [ 11. Many materials have been fabricated into implantable prosthetic devices in various configurations for tissue interfacing applications. Highly polished, nonreactive materials are usually selected when a weak bond (or no bond) is required. Conversely, strong interfacial attachments require a porous surface (fabric or foam-like structures), usually fabricated from a reactive material, reactive to the point that it adsorbs protein. I This project supported by Southwest Research Institute Internal Research funding: Project No. 13-9208. 0022.4804/78/0252-0122$01.00/0 Copyright 0 1978 by Academic Press, Inc. All rights of reproduction in any form reserved.

July 26, 1977

Cannulae laminated with a velour (dacron or nylon) outer surface exhibit a “growth phenomenon” when used as percutaneous implants [2]. Basal cells adhere and maintain their bonded relationship with the monofilament material throughout their lifespan. As the basal cells mature, their natural course of migration is toward the skin’s surface carrying the monofilament fiber along with them, which presumably accounts for the catheter’s appearance of “growing” from the skin, Cannulae whose outer surface is fabricated from a nonporous, nonreactive material allow downgrowth of epithelium to the point that either a sinus tract develops or the device becomes completely marsupialized. These dicta leave one with the following dilemma: “If good skin interfacing is accomplished, the percutaneous implant will eventually become extruded. If good skin interfacing is not accomplished, a sinus tract will form through which bacteria can gain entrance.” OBJECTIVE To solve this dilemma, it was apparent that a radical departure from the direct skin interfacing approach was necessary. This realization led to a pilot study to test the feasibility of an indirect method for exteriorizing implantable cannulae. Such an indirect approach would require the skin to interface with a viable biologic tissue and the nonbiologic material to interface with mesodermal tissue.






\ \




b exkrnel energizing



to im lanted

bloo if pump

FIG. 1. Construction of a standard ileal conduit is illustrated, showing the method of bringing the serosa into apposition with the velour band that has been laminated to the Mastic cannula.



It was concluded that one alternative would be to bring fabric-covered cannula through an isolated segment of gut so that the mucosa interfaces with the skin and the fabric interfaces with the serosa. Because the small bowel contains fewer microorganisms, the terminal ileum was considered preferable. Since this was to be a pilot study to test the feasibility of this approach, only three animals were used: two mongrel dogs and one Spanish goat. Simple mock cannulae were fabricated from Silastic tubing having an i.d. of 5 mm, an o.d. of 7 mm, and a length of 10 cm. A band of nylon velour 2 cm in width was bonded to the surface of the tubing near one end, leaving a 2-cm portion of that end exposed. A piece of uncured Silastic was used to plug the cannula’s bore because patency of this structure

would allow direct external communication with the peritoneal cavity. The cannulae were then cured in a steam autoclave. After inspecting the finished fabrication, the cannulae were wrapped and sterilized by steam autoclave. Using standard operating room conditions, and with the animals under general endotracheal anesthesia, the prepared abdomens were opened with a subumbilical midline incision. In the canine models, it was possible to isolate a lo-cm segment of ileum near the ileocecal valve, but in the goat, the terminal 20 cm of ileum has a mesentery that is too short to allow segmental isolation. After some difficulty, a segment of the goat’s ileum was isolated where the mesentery broadens near its junction with the jejunum. After selecting a suitable arcade, the bowel was divided between crushing clamps. The distal end of the isolated segment



FIG. 2. Gross photograph of bivalved formalin-fixed specimen of an ileal conduit housing a Silastic rod that passes in two stages from outside the body (right) into the peritoneal cavity (left). The ileostomy site is not present in this picture. The Silastic rod passes into the lumen of the ileal conduit through the ileostomy, exits from this lumen (midportion of photo at *), and enters the free peritoneal cavity. Just proximal to its point of entrance into the ileum, the rod is covered with velour fabric seen in the illustration as fine white lines (arrows).

was brought through a separate ileostomy incision, and a standard ileostomy was fashioned (Fig. 1). A running ooo0 catgut suture was used for hemostasis in closing the proximal end. This was reinforced by imbricating interrupted oooo silk sutures. The two ends of the remaining ileum were then anastamosed to reestablish ileal continuity. About 2 cm from the closed proximal end of the isolated segment, and on the antimesentery side, a longitudinal incision was made between two stay sutures. The cannula was inserted in this incision so that the velour collar came to rest at the

ileostomy. Imbricating sutures of oooo silk brought the serosa into contact with the entire velour surface, leaving the small uncoated end of the cannula lying free within the abdominal cavity. Tissue from the serosal surface was thereby encouraged to grow into the interstices of the velour fabric to create a bacterial barrier along the cannula’s pathway. After approximating the mesentery edges to prevent internal herniation, the abdominal incision was closed in layers. About 2 cm of the cannula protruded from the ileostomy and was easily monitored postoperatively by visual inspection. Cornbiotic


FIG. 3. Low magnification of a well-healed ileostomy. and cutaneous epithelia is indicated (*). H and E, x380.


The point of juncture

between the ileal

FIG. 4. Higher magnification photomicrograph of the ileostomy site shown in Fig. 2. The uninterrupted nature of the epithelial covering at this site is apparent. H and E, x 1500.



FIG. 5. Low magnification photomicrograph of a full thickness section of ileal wall just distal to the entrance of the rod into the peritoneal cavity from the lumen of the conduit. The arrows point to a lush proliferation of granulation tissue from the serosa. This healing tissue has grown around and incorporated the loops of the velour fabric, thus providing secure mechanical attachment of the rod to the serosal surface of the exit tunnel. A tight seal around the exit hole in the ileal wall is also created. The irregular fragments of amorphous material (*) are from the Silastic rod to which the velour fabric is firmly attached. H and E, x 150.

weeks; the goat was sacrificed at 3 months; and the isolated ileal segment, ileostomy , and ileal anastamosis were removed en block. There were no signs of peritonitis, and adhesions were confined to those areas that were predictable. The isolated RESULTS ileal segment and contained cannula were None of the animals experienced any bivalved and grossly showed excellent tispostoperative difficulty, and all of the sue ingrowth into the velour (Fig. 2). Photomicrographs of sections taken at the cannulae remained in their original position. One dog was sacrificed at the end of 3 ileostomy site of the dog indicate a well-

was given daily during the first postoperative week. Food was withheld, but water was given ad libitum the first 3 postoperative days. On the fourth postoperative day, food was offered ad libitum.

FIG. 6. High magnification photomicrograph of the serosal granulation tissue seen in Fig. 4. The velour threads (*) are surrounded by histiocytic cells, including several multinucleated giant cells. The “empty” lacunae eccentrically positioned around each thread are all oriented in the same direction. These artificial spaces result from the different cutting properties of tissue and the velour threads. Spindle-shaped fibroblasts and capillaries arc also present in this tissue. H and E, x 1500. FIG. 7. An inflatable bulb bonded to the cannula depicts a method being proposed to stabilize the cannula below the abdominal wall. This would undoubtedly necessitate periodic deflation of the balloon and irrigation to rid the pouch of accumulated mucosal secretions, bacteria, and sloughed epithelial debris.



/ tube for filling




,,exteriorired ortion of smooth sur Paced conduit

bulb, * epidermis


. sh3cutaneous fat



elastic bulb

’ -- mesentery

bondedto canula ----segment


tacked to peritoneal

to prevent


of ileum

dacron or nylon velour


banded. --

to Silastic* tube

\ serosaf surface

in cDntact

with velour

’ intra ‘abdominal

portion of Sifastz * 5 conduit




healed ileostomy, which demonstrates the abrupt transition from intestinal epithelium to squamous epithelium (Figs. 3 and 4). Figures 5 and 6 demonstrate the successful results of the original premise. Tissue sections taken from the same areas in the goat showed an identical pattern. The interstices of the monofilament nylon velour are seen to have entrapped granulation tissue growing from the serosa, and since no infection was evident, a bacterial barrier was presumed to have been erected. The one remaining animal is now 6 months postoperative and appears quite normal. There is no evidence of mucosal erosion caused by the cannulae, which was the only theoretical objection offered to this approach. This animal will be retained for long-term observation. SUMMARY

The authors have described one alternative to a percutaneous catheter design applicable to either the thorax or abdomen. Although the catheter must exit from the abdominal wall, the proximal end can be

directed into the thorax via the peritoneal cavity. This indirect method for long-term cannula placement utilizing an isolated ileal segment has been designed for use either as a peritoneal dialysis or as an umbilical power transmission cord to power implanted artificial hearts or assist devices. The surgical procedure was technically simple and straightforward when using the canine as a model. The alternative animal model was the goat, which proved to be a poor selection for a variety of reasons. A possible method for cannula stabilization has been included in a diagram but has not yet been reduced to practice (Fig. 7). REFERENCES 1. Hall, C. W., Adams, L. M., and Ghidoni, J. J. Skin interfacing development. In Proceedings of the 5th Annual Contractors Conference of the ArtiJcial Kidney Program of the National Institute of Arthritis and Metabolic Diseases, National

Institutes of Health, Washington, D. C., January 1972, pp. 117-118. 2. Hall, C. W., Adams, L. M., and Ghidoni, J. J. Development of skin interfacing cannula. Trans. Amer. Sot. Artif. Intern. Organs 21: 281, 1975.

Indirect percutaneous cannula construction.

JOURNAL OF SURGICAL RESEARCH Indirect 25, 122- 128 (1978) Percutaneous C. WILLIAM HALL, M.D.,* *Institute Medical Scientist, tDepartment of Path...
5MB Sizes 0 Downloads 0 Views