Experimental arterial allografting under low and therapeutic dosages of cyclosporine for immunosuppression.

The aim of this study was to investigate performance of preserved arterial allografts under the protection of a high-dose and a low-dose immunosuppressive regimen, with cyclosporine (CsA). Dog carotid arteries were harvested and stored for 14 days at 4 degrees C in University of Wisconsin organ preservation solution. Segments (6 cm) of carotid artery were orthotopically and bilaterally implanted in mongrel dogs (n = 18). CsA was given in two dosage regimens: 25 mg/kg/day (group I, n = 7) and 10 mg/kg/day (group II, n = 7). The control group received no CsA (group III, n=4). After 3 months of implantation, patency was assessed by angiography. The grafts were excised for investigation of vessel wall and endothelial function and morphology. For assessment of function in vitro, slices of arterial segments were connected as ring preparations to an isometric force transducer and immersed in a 5 ml organ bath (37 degrees C) containing Tyrode's solution. The contractile response was examined by adding 40 mM KCl and phenylephrine (100 microM) to the organ bath; endothelium-dependent relaxation was examined by adding methacholine (100 microM). Morphology was assessed semiquantitatively. The functional responses to KCl, phenylephrine (Phe) and methacho- line (Met) after 14 days of storage in UW, were 30.2 +/- 1.2 mN, 26.9 +/- 1.0 and 45 +/- 1.2% (means +/- SEM, n=9), respectively. Patency after three months of implantation for group I was 100% (14/14), for group II 50% (7/14), and for group III 75% (6/8). In vitro functional responses of preserved arteries, after 3 months of implantation in group I were 58.5 +/- 10.6 mN (KCl), 36.5 +/- 5.8 mN (Phe), and 57.4 +/- 9.7% (Met), respectively. Functions in group II were 1.2 +/- 0.1 mN (KCl, 0.0 mN (Phe), and 0.0% (Met). Grafts in group III showed no function. Measurement of medial thickness showed significant thinning (P <0.05) in groups II and III. Patency and function of arterial allografts under a therapeutic dose of CsA were superior to grafts implanted under low-dose CsA or no immunosuppressive treatment.

Preservation of canine liver grafts using HTK solution.

HTK (histidine-tryptophane-ketoglutarate) organ preservation solution has been shown to be effective in human kidney transplantation, but the efficacy of HTK for extended liver preservation has not been determined. In this study, canine livers were preserved in HTK and compared with livers preserved in University of Wisconsin solution. First, the right and left liver lobes in dogs were flushed separately with cold HTK and UW, respectively, according to a double-flush method. After splitting the liver, the right and left lobes were stored at 4 degrees C in either solution for 24 hr and 48 hr and assessed microscopically for parenchymal cell swelling, and enzyme histochemically for 5'-nucleotidase (5'-NT) as a marker of ischemic liver injury. Unlike livers preserved in UW (n = 5), HTK-preserved livers (n = 5) showed progressive parenchymal cell swelling after 24-hr and 48-hr storage. The 5'-NT scores in HTK livers were lower than in UW livers, indicating increased storage injury (0-5% and 66-85% in HTK- and UW-preserved livers, respectively, after 48-hr storage). Second, graft function was tested in an orthotopic liver transplantation model in the dog. Whole livers were flushed in situ with cold HTK or UW and stored at 4 degrees C for 24 hr or 48 hr. Liver grafts stored in HTK were not washed out prior to reflow in the recipient, in contrast to grafts stored in UW. Livers preserved for 24 hr using HTK showed life-supporting function after transplantation (n = 5, survival 12 hr-8 days). All grafts preserved for 48 hr in HTK did not function (n = 5, survival < 10 hr). UW-preserved grafts all functioned after 24-hr storage (n = 5, survival > 6 days), as well as after 48-hr storage (n = 6, survival > 6 days). Peak serum glutamic oxaloacetic transaminase (SGOT) values after transplantation of 24-hr and 48-hr HTK-preserved livers did not differ from peak SGOT values of UW-preserved livers after similar preservation times. In conclusion, UW solution is more effective than HTK solution in extended preservation of canine liver grafts: 24-hr storage of livers preserved with HTK solution is feasible, whereas 48-hr storage results in a nonfunctioning graft.

Microvascular surgery and diseased vessels.

Hardly any data exist concerning the effects of arterial vessel disease on the results of microvascular surgery. As the scope of microvascular surgery expands, diseased vessels will surely be encountered more frequently. Therefore an experiment was performed in rabbits who were fed a cholesterol-enriched diet for 3 months. Then an anastomosis was made in both carotid and femoral arteries (total of 65 arteries) with microsurgical techniques. The diet was continued until the animals were killed at fixed times from 1 day to 4 months. The overall patency rate at the time of death was 91.8%. At the time of the operation two situations were present: hypercholesterolemia without any macroscopic changes and hypercholesterolemia with evident macroscopic atherosclerotic lesions. Atherosclerotic lesions in these small arteries present technical surgical difficulties, and direct results will depend on the skill and experience of the surgeon. Hypercholesterolemia without any macroscopic changes, in combination with the trauma of the operation, will lead to an accelerated formation of atherosclerotic changes. Lesions already present will progress in size. Both events lead to narrowing of the lumen at a later stage.

Morphologic changes of extrahepatic bile ducts during obstruction and subsequent decompression by endoprosthesis.

The morphologic changes of the extrahepatic biliary tract during obstruction and the effects of biliary decompression by means of an endoprosthesis on the bile duct wall were studied by light microscopy and scanning electron microscopy. Common hepatic duct biopsy specimens and bile cultures were obtained during surgery from 30 patients with a distal common bile duct obstruction caused by a tumor. Thirteen patients had obstructed bile ducts of 3 weeks' duration (group A). Seventeen patients had had jaundice for a period of 4 weeks and had subsequently undergone preoperative endoscopic biliary stenting for a period of 4 weeks (group B). Three autopsy specimens from patients without hepatobiliary disease served as controls. The results showed that the initial dilatation and thickening of the obstructed ducts in group A were associated with a mild inflammation, a moderate degree of fibrosis, and local epithelial disintegration. The presence of an endoprosthesis, however (group B), induced severe inflammatory changes with considerable fibrosis and ulcerative lesions, resulting in markedly thickened ducts with lumina approximating the diameter of the stent. Three of 13 (24%) bile cultures in group A were positive and 14 of 17 (82%) in group B were positive.

Performance of sliding knots in monofilament and multifilament suture material.

Three different sliding knots were tested using five recently developed monofilament and multifilament suture materials. The resorbable materials were polyglactin-910 (Vicryl), polyglycolic-acid (Dexon-Plus), polyglyconate (Maxon), and polydioxanone (PDS), and the nonresorbable material was polypropylene (Prolene). For each type of sliding knot, three or five throws of suture were tested. Knot strength was determined by the loop holding capacity, which was defined as the strength at which the knot broke, or at which slippage in the knot amounted to more than 2 mm. When the three kinds of sliding knots were compared, identical sliding knots with identical throws around a single suture were found to be the most unreliable. Nonidentical and parallel sliding knots differed little with respect to knot reliability. Five-throw knots were generally stronger than three-throw knots. However, the effect of adding two extra throws to three-throw sliding knots was only significant if monofilament suture material was used. Comparison of the different suture materials revealed major differences in knot holding ability. These findings indicate that knot strength is dependent on both the type of knot and the type of suture material, and surgeons should be cognizant of these variables.

A study of valve incompetence that developed in an experimental model of venous hypertension.

Surgical treatment of venous valve incompetence should be aimed at restoring the underlying valve defect. For a better definition of the structural anatomical defects in acquired valve incompetence, an experimental study was performed with 40 rats. Venous valves were subjected to hemodynamic stress by creating femoral arteriovenous fistulas. The resulting valve incompetence was studied by using descending phlebography and a casting technique, which allowed for an accurate description of leaking valves when the scanning electron microscope was employed. A three-dimensional insight of the morphology of incompetent venous valves was obtained. A description of short- and long-term (two to four months) changes in valve architecture was also obtained; initially, there was retrograde passage of fluid through a separation of the cusps' free border. The cusps' bulgings were still clearly defined after two months, and, at this stage, commissures had started to widen. After a four-month period, commissures were lost and no recognizable valve sinus was present.

Chest wall reconstruction with degradable processed sheep dermal collagen in dogs.

Chest wall defects resulting from oncological operations often require prosthetic repair. The objectives of prosthetic repair are to provide a cosmetically acceptable substitute, prevent paradoxical chest wall movement, and protect vital organs. Of the many materials that have been used in these repairs, none have proved to be ideal. The aim of our study was to investigate the application of a biodegradable material--processed sheep dermal collagen--as a chest wall prosthesis. A full-thickness chest wall defect of 10 x 10 cm was created in 12 dogs; 10 had repair with a processed sheep dermal collagen prosthesis and 2, the controls, with polypropylene mesh. In this study, the biomaterial fulfilled its function as a chest wall prosthesis at 24 weeks' follow-up. No respiratory problems were seen, the chest wall remained stable with minimal and decreasing respiratory paradoxical movement, and the processed sheep dermal collagen slowly degraded and was replaced by the host collagen. Processed sheep dermal collagen offers long-term advantages because it is degradable. Late complications from a nonabsorbable prosthesis, ie, infection or disintegration of the material possibly causing extrusion or fistula formation, are avoided.

Effects of biliary endoprostheses on the extrahepatic bile ducts in relation to subsequent operation of the biliary tract.

Despite the widespread use of transpapillary biliary endoprostheses, little is known about their effect on the extrahepatic bile ducts. In an experimental study in dogs, we induced inflammatory changes in the bile ducts by stent insertion and studied the reversibility of these changes after stent removal. In addition, the consequences of a period of preoperative stenting for subsequent operation of the biliary tract and the eventual detrimental effects of stenting on the histologic factors of the liver were studied. Twenty-six mongrel dogs were randomly divided into four groups: group 1, stenting during four weeks; group 2, after four weeks stenting, construction of a hepaticojejunostomy; group 3, four days of common bile duct (CBD) ligation, four weeks stenting and hepaticojejunostomy, and group 4, four days of CBD ligation and hepaticojejunostomy. All dogs were sacrificed two months after the last procedure. Hepatic biopsies were obtained during each procedure and bile duct biopsies during hepaticojejunostomy and upon sacrifice. Four weeks of stenting of a normal or obstructed CBD resulted in fibrosed bile ducts, showing severe chronic inflammation with papillary hyperplasia of the epithelium. All bile cultures grew fecal bacteria. Two months after stent removal, inflammation was still present, albeit less severe. Stenting and subsequent surgical treatment resulted in a higher incidence of postoperative complications (54 percent) compared with the control group (14 percent), although this did not reach statistical significance. Hepatic histologic factors were not markedly changed after transpapillary endoprosthesis placement, but after hepaticojejunostomy cholangiolitis was observed. Whenever transpapillary biliary endoprostheses are used, the local effects on the extrahepatic bile ducts and the subsequent bacterial contamination of the bile should be considered.

Biomechanical measurements on scaphoid bone screws in an experimental model.

A number of screws commonly used for internal fixation in scaphoid bone fractures and nonunions are compared regarding biomechanical properties and clinical applicability. The experiments were carried out on models made of ash-wood, representing a reconstruction and fixation as is performed in a cortico-cancellous inlay bone graft for scaphoid non-union. For fixation use was made of 2.7 and 3.5 AO/ASIF cortical screws respectively, 4.0 AO/ASIF cancellous screws, Herbert screws, and a newly designed screw called the three components screw (D.K.S.). The models with implanted screws were tested for bending strength, tensile strength and torsion stability. No large differences between the various screws were found regarding the measured parameters, so that a small intra-osteal implant such as the Herbert screw and the D.K.S., which can be inserted easily and which gives a certain amount of interfragmentary compression, will be sufficient for osteosynthesis of the scaphoid bone. In case an intra-osteal implant is not available a single 3.5 AO/ASIF cortical screw, inserted following lag-screw principles, is recommended.

Protection from stress in bone and its effects. Experiments with stainless steel and plastic plates in dogs.

In a preliminary experiment the paired radii and femora of dogs were tested for bone mineral mass and mechanical properties including the load at break, the ultimate bending strength and the modulus of elasticity; symmetry was observed for most of the parameters determined. The influence of the elasticity of materials used for the internal splintage of bone and its relationship to bone remodeling were then investigated for stainless steel and plastic plates applied to the femora of dogs. A significant decrease in bone mineral mass per centimetre length of bone and in mechanical properties was demonstrated for the femora plated with steel, and microradiography showed that this was due to massive endosteal resorption. A model for determining the influence of protection from stress in bone is presented.

Intimal hyperplasia in reversed and in situ vein grafts: an intra-individual canine study.

The apparent superiority of the in situ vein graft over the reversed vein graft in long arterial reconstructions has been explained by a superior hemodynamic performance and a reduction of intimal hyperplasia in the in situ graft. To examine this, an intracomparative canine study was performed with respect to the progression of intimal and medial changes in both in situ and reversed vein grafts. Paired femoropopliteal artery grafts were inserted in six dogs using the in situ technique in the right leg and the reversed technique in the left leg. The grafts were excised at 1 day, 3 months, and 6 months after operation. Substantial changes were shown both in histologic structure and in absolute intimal and medial thickness, without a significant intra-individual difference between in situ and reversed grafts. The intima-to-media ratio increased in the first 3 months and stabilized in the 3- to 6-month interval. In this intra-individual canine study preservation of adventitia and vasa vasorum had no biologic effect on the development of the same intimal changes in the midsection of reversed and in situ vein grafts.

Knot security of synthetic absorbable suture material; a comparison of polyglycolic acid and polyglactin-910.

To compare the knot reliabilities of two kinds of synthetic absorbable suture material, twelve different knots commonly used in surgical practice were tested. Twenty tests were performed on each knot, i.e., ten with Dexon-S (uncoated) and ten with Vicryl (coated). The knots made with Dexon-S were found to slip less frequently, to be significantly stronger, more consistent, and more reproducible than those made with Vicryl. It was concluded that uncoated Dexon-S is superior to coated Vicryl with respect to know reliability. The practical implications of these findings for surgical performance are discussed. It is emphasized that surgeons should be more aware of the relationship of the holding power of surgical knots to not only the knot-typing technique but also the kind of suture material used.

Evaluation of boiled potato peel as a wound dressing.

In a series of experiments full thickness skin defects in 68 rats were covered with dressings made of boiled potato peels according to the method developed in Bombay. The wounds closed within 14 days and histologically complete repair of epidermis was found. The cork layer of the potato peel prevents dehydration of the wound and protects against exogenous agents. Experiments with homogenates revealed that a complete structure of the peel is necessary. Steroidal glycosides may have contributed to the favourable results.

Comparison of lymphatic and venous interpositional autografts in experimental microsurgery of the canine lymphatics.

In mongrel dogs, 56 autologous lymphatic and vein grafts were interpositioned to bridge a defect in the femoral collecting lymphatics. In one group, 26 lymphatic autografts were interpositioned with good results. No obstruction was observed over 6 months. In another group, 20 venous autografts were interpositioned after irrigation with heparinized saline and another 10 autografts were interpositioned without irrigation. After 1 week, four irrigated grafts were partially occluded with a red thrombus; after 6 months, all grafts were totally occluded. In a third group, 15 lymphaticolymphatic anastomoses were enveloped by a silicone sheet to provoke prolonged devascularization. None of the vessels was patent. Anastomotic patency was inspected in vivo postoperatively. The specimens were studied with light microscopy and scanning and transmission electron microscopy. Prolonged devascularization damaged the endothelial cells. The results show that the lymphatic vessel autograft is the best choice for an interpositional autografting to bridge a defect in lymphatic vessels.

Healing of microvascular arterial anastomoses, as seen on corrosion casts by scanning electron microscopy.

We made 44 microsurgical anastomoses in the femoral artery in rats. The healing was studied from one day to 4 months, by making an acrylic cast of the lumen of the femoral artery and the surrounding vessels, and examining the cast by scanning electron microscopy. The method proved to be easy and relatively quick, and it limited the possibility of artifacts. The high depth of focus permitted simultaneous study of the main lumen and of the perivascular structures after microvascular anastomoses.

Continuous tissue oxygenation assessment during bloodflow alterations in an isolated hindlimb model of the pig.

A continuous intramuscular oxygen tension sensor was compared, with transcutaneous oximetry and laser Doppler flowmetry, during periods of arterial flow alterations in an isolated hindlimb model in the pig. The intramuscular oxygen tension sensor correlated well with bloodflow and was superior to the other two methods.

Veno-venous bypass without systemic heparinization using a centrifugal pump: a blind comparison of a heparin bonded circuit versus a non heparin bonded circuit.

Veno-venous bypass without the use of systemic heparinization has recently become of increasing interest for application during liver transplantation and surgery on the large abdominal veins. However, possible adverse effects on blood components as demonstrated by means of hematologic and hemostatic parameters or on the occurrence of thromboembolic complications are until now not excluded. No consensus has been reached as to the efficacy of heparin coated circuits in those procedures. In the present study veno-venous bypass was performed for four hours in ten dogs using heparin coated and non coated circuits without further heparinization in a randomized blind fashion. No changes or significant intergroup differences were noted in the hematological and coagulation parameters. Macroscopic evaluation of the circuits revealed small strands of fibrin on all connector rims and clots in the center part of the pump head and at the cannula tips. The lungs showed two small emboli in large size pulmonary arteries and also two minor emboli in small size arteries. In four animals the emboli were equally divided between the two groups. As expected regarding the size of the clots no influences could be seen on hemodynamic or respiratory parameters. With Scanning Electronic Microscopy a monolayer of activated thrombocytes was observed on the surface of the bypass circuits in the coated as well as in the uncoated group. This study suggests that a veno-venous bypass without systemic heparinization is possible without serious damage to blood cellular elements or impressive activation of the coagulation system.(ABSTRACT TRUNCATED AT 250 WORDS)

Three-dimensional pressure profilometry of the anal sphincter.

Single channel manometry is of limited value in determining the cause of sphincter dysfunction. This is due mainly to the recording variability caused by radial pressure asymmetry. Multi-channel manometry does not have this disadvantage, but is complicated and difficult to interpret. We report on computerized eight-channel manometry which permits three-dimensional reconstruction of the sphincter. Fifteen subjects were measured. At rest, lower pressures were recorded in the left, left-dorsal, and dorsal directions. Sphincter length was shortest in the right direction and ventral directions. The graphic reconstruction showed marked indentations in the right- and right anterior direction, and one indentation on the opposite side. At maximal squeeze the graphic reconstruction showed the same indentations, but they were more pronounced. In conclusion, computerized eight-channel manometry proved to be an efficient technique which could be routinely applicable. The graphic reconstruction provides insight into radial and axial pressure asymmetry.

Pressure and X-ray recording of reflux into the thoracic stomach.

Anastomotic leakage, pulmonary aspiration and reflux-esophagitis might be induced or aggravated by the increased duodenogastric reflux observed in the thoracic stomach. In this study, the effect of respiration on the reflux-promoting pressure gradient in the intrathoracally located stomach was assessed. In nine patients pressure recording was done in the duodenum and the abdominal and thoracic part of the stomach. Intrapleural pressure was determined by recording mouth pressure during inspiratory occlusion. In addition, the course of injected contrast was examined fluoroscopically. The mean end-expiratory pressure gradient in the thoracic part of the stomach was 0.8 cm H2O, increasing up to 6.0 cm H2O and 21.3 cm H2O during normal and forced inspiration, respectively. Fluoroscopic examination showed reflux of contrast that coincided with the downward movement of the diaphragm. From this study, we conclude that reflux into the thoracic stomach is promoted by intraluminal pressure fluctuations induced by voluntary breathing. Performing a pyloroplasty or -myotomy after intrathoracic esophagogastrostomy destroys the integrity of the pyloric sphincter as a barrier to reflux, thus promoting duodenogastric reflux.

A scanning electron microscopic study of the common bile duct epithelium in the rabbit during experimental biliary tract obstruction.

Complete biliary obstruction was induced in rabbits by distal ligation of the common bile duct (CBD). The epithelial surface of the CBD was studied with scanning electron microscopy (SEM) at 1-6 days post-ligation. Concomitant biochemical assessments and pressure measurements in the CBD were performed. SEM of non-ligated CBD showed that the epithelium is arranged in folds and clefts, the latter displaying interdigitating cellular processes. At 2 days post-ligation, the epithelial clefts were focally distended showing marked dehiscence of the cellular processes with exposure of the subepithelial connective tissue layer. At 4-6 days post-ligation, extensive defects in the epithelium were observed, frequently with a sharp demarcation between intact epithelium and exposed connective tissue stroma.