In vitro degradation of a biodegradable polyurethane foam, based on 1,4-butanediisocyanate: a three-year study at physiological and elevated temperature.

Biodegradable polyesterurethanes (PUs) may be used as scaffold materials for tissue regeneration applications, because of their excellent mechanical properties. In this study, the degradation of highly porous PU foams was evaluated in vitro. The PU had amorphous soft segments of DL-lactide/epsilon-caprolactone and uniform hard segments, synthesized from 1,4-butanediisocyanate and butanediol. The foams were degraded for 3 years in a Sörensen buffer solution (pH 7.4) at 37 and 60 degrees C. Dimensions of the foams, intrinsic viscosity, mass loss, thermal properties, and composition of the remaining material were evaluated. Copolyester (CP) foams of DL-lactide/epsilon-caprolactone served as controls. The PU foams kept their dimensions for 20 weeks at 37 degrees C, whereas CP foams collapsed after 3 weeks. PU mass loss reached a maximum of 80% at both 37 and 60 degrees C. CP mass loss reached 99.9% at 60 degrees , and 92% at 37 degrees C after 3 years. The degradation processes at 37 and 60 degrees C are initially the same, but eventually degradation products with different thermal properties are being formed. (1)H NMR studies showed that the hard urethane segments of the PU do not degrade in vitro at pH 7.4. It was concluded that the PU material has favorable characteristics for a scaffold material. Compared to long-term in vivo results of the same PU these in vitro results are not representative for the in vivo situation and therefore total resorption has to be investigated in long-term in vivo studies.

Local anesthesia for endovascular abdominal aortic aneurysm repair.

OBJECTIVES: This study reports the results of a prospective continuous cohort of patients treated for endovascular aneurysm repair (EVAR) with a unified anesthetic strategy based on the use of local anesthesia (LA) in all patients, while reserving regional (RA) or general anesthesia (GA) only for those with predefined individually or surgically specific indications. METHODS: All patients treated by EVAR for an elective aortic abdominal aneurysm (AAA) between April 1998 and December 2003 were included. The strategy of treatment generated three cohorts of patients (LA, RA, or GA). Primary outcome included all-cause mortality, nonfatal cardiac morbidity, respiratory complications, and renal failure. Secondary outcome measures included conversion to general anesthesia, use of analgesics, and time-related outcomes (operating time, length of stay in intensive care unit and hospital, time required to resume oral intake, and time to ambulation). RESULTS: A total of 239 patients underwent EVAR: 170 LA, 31 RA, and 38 GA. Overall mortality was one patient (0.4%). LA was associated with a lower incidence of complications compared with GA (P < .001). In the LA group, two patients had to be converted to GA, one because of a dissection and one because of anxiety. In 13% of the patients in the LA group, additional intravenous sedation or analgesia was required. Operating time and length of stay in intensive care was shorter in the LA and RA groups than in the GA group (P < .001). Length of stay in hospital and time to ambulation and regular diet was shorter in the LA group compared with the RA and GA groups (P < .001). CONCLUSIONS: A strategy based on the preferential use of LA for EVAR restricting RA or GA only to those with predefined contraindications is feasible and appears to be well tolerated.