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Biomedical subjects

K Berger

Publications and source records attributed to K Berger.

At least 127 records · Page 7Linked to original sources
PubMed1984

Effects of compliance alteration on healing of a porous dacron prosthesis in the thoracic aorta of the dog.

In our study, the results reveal that a marked reduction in the compliance of an external-velour, weft-knit Dacron prosthesis did not impair healing of either the graft wall or of the anastomoses when these grafts were implanted in the upper part of the descending thoracic aorta of the dog for 56 days. These observations are clinically relevant, since they are important to the design of noncrimped fabric prostheses which are resistant to kink and compression when used for axillofemoral, femoropopliteal and femorotibial bypass. However, experimental studies of the influence of compliance disparity should be extended to such grafts implanted for several years.

Animals↗
PubMed1981

Late fiber deterioration in Dacron arterial grafts.

The occurrence of late fiber deterioration was examined in 493 Dacron arterial prostheses. Grafts implanted were of four types: 137 Meadox Wesolowski Weavenit (WN), 71 Golaski Microknit (MK), 70 USCI Sauvage(Tm) external velour non-crimped (EVNC), and 215 USCI Sauvage external velour random-crimped (EVRC). Prostheses had been implanted for three to 15.3 years; no defects were detected prior to three years. Deterioration occurred in 15 of 493 grafts (mean incidence: 3%). Between 4.9% and 5.8% of patients had graft deterioration-nearly the same incidence in all four types of grafts. Deterioration consisted of thinning and breakage of yarn filaments, causing development of holes and, in some cases, graft dilatation. Dilatation did not always precede filament breakage. Broken filament ends were either tapered or square-ended, suggesting that modes of breakage. Tensile strength tests howed that fibers sometimes weakened nonuniformly within a specimen. Fiber breakage was associated with crimp ridges. The findings suggest that manufacturing variations probably reduce fiber resistance to mechanical fatigue. Other contributing factors may include storage conditions, sterilization methods, handling, and the degradative effects of tissue fluids and enzymes.

Aneurysm↗
PubMed1980

Experimental comparison of the thrombogenicity of fibrin and PTFE flow surfaces.

Two types of 4 mm ID prostheses were studied in the carotid arteries of the dog. These were noncrimped polypropylene-supported filamentous velour knitted Dacron (PPSFV) and expanded polytetrafluoroethylene (e-PTFE, Gore-Tex). Thrombus-"Free" Surface TFS) areas and patency rates were determined at the end of the implant periods. One series of implants was subjected to controlled low flow rates for six hours; another was exposed to physiologic flow rates and observed at seven days, 14 days, and 12 weeks. At six hours the filamentous Dacron, preclotted according to a specific regimen utilizating heparin, performed as well as, and possibly better than, e-PTFE. The Gore-Tex developed surface coagulum in an irregular fashion which was related to graft wetting and blood soakage. Seven-day TFS scores and patency rates of the two graft types were comparable at physiologic flow rates. At two weeks, TFS scores and patency rates of the two graft types were comparable at physiologic flow rates. At two weeks, TFS scores and patency rates dropped. This was sufficiently marked in the case of e-PTFE that longer-term implants were not done. However, PPSFV grafts were implanted for 12 weeks, and all grafts examined at that time had closed. It appears that patency of 4 mm ID grafts of this construction will not be reliably attained in the dog carotid artery without the use of platelet-inhibitory drugs until complete healing has occurred.

Animals↗
PubMed1980

A healable filamentous Dacron surgical fabric. Experimental studies and clinical experience.

A strong, lightweight, highly compliant Dacron surgical fabric of warp-knit, velour construction has been developed as an outgrowth of research on filamentous tubular vascular prostheses. This material has excellent suturability and conformability, high preclotting efficiency, and is imprinted with calibration marks at 2 cm intervals. Experimentally, iliac artery and descending thoracic aorta patch grafts of this material were completely healed 28 days after implantation in dogs. Light and electron microscopy showed excellent healing. This paper reports clinical results of 119 patches implanted in 109 patients who have been followed for a mean of 26.4 months (range: 16--34 months). Of these, 20 patches were used in arterial reconstructions, and 99 were used in the heart for repair of 95 congenital and four acquired defects. The 20 patch angioplasties were performed in the carotid artery (four patches), subclavian artery, (one patch), common femoral artery, profunda femoris artery, or superficial femoral artery (10 patches), and in the popliteal artery (five patches). This new surgical fabric is easily adaptable to complex angioplasties and for repair of intracardiac abnormalities. No complications intrinsic to the surgical fabric have been observed in clinical use of this material in 109 patients.

Adolescent↗
PubMed1979

Current arterial prostheses. Experimental evaluation by implantation in the carotid and circumflex coronary arteries of the dog.

Five types of 4-mm diameter arterial prostheses (three Dacron, one expanded Teflon, one preserved umbilical vein) were studied in the dog to assess graft thrombogenicity. Separate experiments involving six hours of controlled blood flow, one-week carotid implantation, and aortocoronary implantation were performed. In general, graft thrombogenicity derived from controlled flow study was more predictive of a graft's long-term implantation success than were one-week implantation results. In order of increasing thrombogenicity, we ranked grafts studied as follows: noncrimped Dacron, expanded Teflon, crimped Dacron, umbilical vein. Results of 19 experimental left coronary artery implantations using Dacron or Teflon prostheses are reported that indicate grafts with low measured thrombogenicity are most likely to succeed in this site. Data presented in this report suggest there is reason to evaluate noncrimped, kink-resistant, porous Dacron grafts for use both in the left coronary artery and below the knee when there is compelling clinical indication and no autogenous vessels are available.

Animals↗
PubMed1979

[Efficiency and limitations of Pickrell's anomyoplasty in treatment of postoperative incontinence in children with anorectal malformations (author's transl)].

Eight children with high or intermediate anorectal malformations and fecal incontinence after primary repair were operated according the Pickrell technique. In 3 patients, the result of the Pickrell plasty was clinically not sufficient and the opposite gracilis muscle was used in addition at a second operative session. The 8 children were studied clinically, radiologically, by electromyography and manometry. The results are presented in detail. All 8 patients had a good passive continence at rest, but an active physiological continence could not be achieved. This seems to be due mainly to the absence of the internal anal sphincter, but partially also to the incomplete or even lacking adaptation of the pulled through bowel, which showed a relative hyperactivity and did not function as a neorectal reservoir. Some therapeutic measures to overcome the problems due to the fact that we deal at the same time with smooth and with striated muscles are discussed in the limelight of the present study.

Adolescent↗
PubMed1978

Interaction of peripheral and central respiratory drives in cats. I. Effects of sodium cyanide as a peripheral chemoreceptor stimulus at different levels of CSF pH.

In cats anesthetized with chloralose-urethane, the central respiratory chemoreceptors were exposed to mock CSF of pH 7.02, 7.02, or 7.57. The right carotid body was simultaneously stimulated by intracarotid injections of 40, 80, or 160 microgram sodium cyanide in 200 microliter Ringer solution. The left carotid nerve and, in some animals, both vagosympathetic truncs were dissected. It could be demonstrated that the increase in ventilation produced by application of NaCN to the peripheral chemoreceptors is significantly larger at high than at low mock CSF pH (i.e. at low than at high central stimulus intensity). In vagotomized cats the responses of VT and V to NaCN similarly depend upon CSF pH; they are somewhat larger, though, than in intact animals. These results are discussed as compared with results reported by different authors.

Animals↗
PubMed1978

The preclotting of porous arterial prostheses.

A four-step preclotting method is presented for use with porous filamentous Dacron prostheses in the fully-heparinized patient. The method employs controlled fibrin formation within graft interstices, heparin neutralization of all thrombin remaining in the graft wall, and delay of systemic heparin neutralization until 15--20 minutes after clamp release. The resulting flow surface is impervious, smooth and hypothrombogenic. Experimental data are presented which support the rationale of this four-step preclotting method. Four years of clinical experience with the method are summarized, involving 300 prosthesis limbs used in aortic bifurcation, aortofemoral, femorofemoral, axillary-femoral and femoropopliteal positions in 192 patients. A clinical perspective of preclotting techniques is presented in which the proper use of this new method is suggested.

Animals↗
PubMed1978

Endovesical transurethral electrostimulation in the rehabilitation of neurogenic bladder in children. 4 Years clinical experience.

4 years of experience in the rehabilitation of neurogenic bladders by endovesical electrostimulation (ES) with 31 children permits us to judge the value and limitations of this treatment. 8 children (26%) reacted favorably to treatment and acquired continence approaching normal. 12 children (38%) showed modifications of bladder-sphincter equilibrium, without acquiring socially sufficient continence. 10 children (33%) showed no response to treatment. In 1 child ES may have precipitated bladder decompensation. An analysis of clinical, manometric, and radiological results in comparison to the underlying pathology permitted us to define the contraindications to ES therapy, criteria which should in the future permit a more efficient selection of patients.

Adolescent↗
PubMed1976

Histologic fate and endothelial changes of distended and nondistended vein grafts.

Sixty-two autogenous cephalic vein segments were grafted into the femoral arteries of 31 mongrel dogs, the left side receiving non-distended (control) grafts and the right side distended (experimental) grafts. Distending media were heparinized blood and saline. Veins were distended at 600 mm Hg for 2 minutes. Specimens were taken at intervals from 15 minutes to 3 months, and were studied by gross inspection, surface observations (light scanning stereoscope to X70 scanning electron microscope to X6,000) and routine histologic techniques (light microscope to X 1000). In general, grafting of veins in the arterial system was followed by progressive degenerative changes in all layers of the vein, including endothelial cell involution, desquamation and re-endothelialization. Often a variable degree of subendothelial fibrous and/or myoepithelial proliferation occurred which might compromise even a lumen lined by healthy endothelium. Distention caused these changes to occur earlier (2-4 weeks) and to be more pronounced. Distention with saline caused more damage to the endothelium than did distention with blood. We conclude that preimplant distention of vein grafts (to overcome spasm) should be employed sparingly, as it adversely affects the endothelial covering of the flow surface, accelerates the development of degenerative changes, and may predispose the graft to early thrombotic complications.

Animals↗
PubMed1975

Presence of endothelium in an axillary-femoral graft of knitted Dacron with an external velour surface.

An axillary-bilateral common femoral graft of knitted Dacron with an external velour surface was examined within one hour after the patient's death from non-graft-related causes. The prothesis, implanted for 20 months, was patent and was completely healed over 32% of the flow surface--that is, full wall fibrous tissue encapsulation of the graft had occurred, and 32% of the flow surface was endothelialized. The remaining flow surface was formed of fibrin, but fibrous tissue healing had reached the inner surface of the graft material, and the fibrin overlay was very thin. The healed protions of the graft included not only the areas adjacent to the anastomoses, but were scattered throughout the 45 cm length of the prosthesis. To our knowledge, this is the first report of complete healing (fibrous tissue encapsulation and endothelialization) documented at points beyond the plannus ingrowth at the prosthesis-artery anastomosis.

Aged↗