A simplified technique for the cryopreservation of vein allografts.

OBJECTIVES: we assessed the effects of cryopreservation on smooth-muscle cell injury in human vein. MATERIALS AND METHODS: long saphenous vein was collected during surgery and cryopreserved. Smooth-muscle cell damage was assessed after thawing by in situ detection of fragmented DNA. The presence of cryoprotectant (10% dimethyl sulphoxide, DMSO), cooling and warming rates, and the rate of cryoprotectant removal after thawing were examined. RESULTS: control veins exhibited damage in 8.5% (95% confidence interval (CI) 4.7 to 13.4%,n=13) of smooth-muscle cells compared with 27.7% (95% CI 23.2 to 32.4%, n=115) in vein frozen in 10% DMSO (p=0.001). In the presence of DMSO, damage to smooth-muscle cells was independent of the rates of cooling (p=0.72) and warming (p=0.45). The rate of dilution to remove the cryoprotectant after thawing also had no effect on cell damage (p=0.64). In the absence of cryoprotectant, cell damage was doubled to approximately 50% by slow rather than rapid warming (p=0.01). CONCLUSION: cooling rate, and the presence of a cryoprotectant, has little effect on smooth-muscle damage, provided that the tissue is warmed rapidly. Slow warming, in the absence of DMSO, causes substantial damage. These results suggest that simplified methods of vein cryopreservation are feasible.

The morbidity of secondary vascular access. A lifetime of intervention.

OBJECTIVES: to examine the outcome and incidence of access-related procedures in patients who dialyse via PTFE secondary access grafts. DESIGN: retrospective case note study. RESULTS: recipients of secondary access procedures face a lifetime of haemodialysis access interventions. In total, 639 access-related procedures were performed on the 72 patients studied. At the end of the study five patients were wholly reliant on central venous catheters for dialysis access. Patients with secondary access grafts have little hope of transplantation; only six of 72 patients received a transplant after a secondary access procedure. CONCLUSION: the increasing number of patients coming to synthetic access-graft procedures and the morbidity of such procedures mean that surgeons should adopt strategies to minimise the use of grafts and limit the number of interventions performed. Careful planning will also reduce the number of central line placements and help to reduce the morbidity associated with long-term haemodialysis. Increasing resources will be required to meet the rising demand for secondary access provision.

Venous allografts prepared from stripped long saphenous vein. Is there a need for antibiotic sterilisation?

AIM: Can useful lengths of vein be retrieved from varicose vein stripping procedures; is it necessary to sterilise this tissue prior to use as vein allografts? METHOD: Stripped long saphenous vein was retrieved at operation. Vein samples were cultured using direct plate inoculation and enrichment culture. Further samples were immersed in two low concentration antibiotic solutions and recultured. Smooth muscle viability was assessed after antibiotic immersion and storage by cryopreservation. RESULTS: High quality vein could be retrieved by vein stripping. Vein segments grew skin commensals on enrichment culture despite negative cultures with standard media plate inoculation (Chi-squared = 53.34 1 d.f. p < 0.001). Low concentration antibiotic solutions sterilised processed vein. Smooth muscle cell viability was reduced by cryopreservation, Mann-Whitney p = 0.008 (control 98% S.E. 0.93 vs. cryopreserved 64% S.E. 6.58), but prior exposure to antibiotics did not compound this effect. CONCLUSION: Useful lengths of vein grafts can be retrieved from varicose vein stripping procedures. Venous segments are frequently contaminated by skin commensals. Enrichment culture is required to detect contamination. Low concentration antibiotics sterilise venous-tissue without affecting smooth muscle cell viability.

Estimation of prevalence of Helicobacter pylori infection in an asymptomatic elderly population comparing [14C] urea breath test and serology.

A non-invasive serological assay devised in this laboratory had a sensitivity and specificity of 100% as determined by culture and confirmed by histology in a group of 47 patients who had undergone endoscopy. The correlation between serology and the non-invasive [14C] breath test was very good. Only one of 24 culture positive patients was, while all 23 culture negative patients were, breath test negative. In a group of 46 healthy elderly persons, however, significant anomalies between serology and breath test were observed. Only 83% of the breath test negative persons were seronegative, while only 68% of the breath test positive persons were seropositive. These results can be explained in terms of age related atrophic gastritis and immune incompetence, causing reduced colonisation and decreased antibody production, respectively. These investigations suggest that non-invasive tests for H pylori infection may not be reliable in the elderly.