Kinetics of D-dimer after general surgery.

D-dimers may be elevated after surgery. However, the kinetics of postoperative D-dimers remains unknown hampering the use of D-dimer testing in surgical patients with suspected venous thromboembolism. D-dimer levels were prospectively measured in 154 patients after general surgery at predefined time points (kinetics were determined in an initial cohort of 108 patients; for validation, these findings were applied to a second cohort of 46 patients). Clinical factors influencing the peak of D-dimers were analyzed using multivariate regression. Surgical operations were stratified based on severity (type I: not entering abdominal cavity; type II: intraabdominal; type III: retroperitoneal/liver surgery). D-dimer levels increased postoperatively reaching a peak on day 7. After type I surgery, peak D-dimer levels did not exceed normal range (300 ng/ml, 100-500). After type II procedures, peak D-dimer level was 1500 ng/ml (200-7800) and returned to normal values after 25 days (+/-14). Peak level was 4000 ng/ml (500-14 400) after type III surgery normalizing within 38 days (+/-11). Clearance of D-dimer was exponential after having reached the peak with 6.0% per day (95% confidence interval 4.8-7.1%). By this clearance, D-dimer values could be adequately predicted in the validation cohort after day 7 (r2 = 0.63). Peak D-dimer levels were independently influenced by the type of surgery (P < 0.001), the operation time (P < 0.001) and by preoperatively elevated D-dimer levels (P < 0.001). Based on this data, duration of postoperative D-dimer elevation after abdominal surgery is predictable. This study indicates for the first time when D-dimers may be used again in the diagnostic algorithm for venous thromboembolism exclusion after surgery in patients with low or moderate clinical probability.

Human umbilical cord cells for cardiovascular tissue engineering: a comparative study.

OBJECTIVE: Tissue engineering of viable, autologous cardiovascular replacements with the potential to grow, repair and remodel represents an attractive approach to overcome the shortcomings of available replacements for the repair of congenital cardiac defects. Currently, vascular myofibroblast cells represent an established cell source for cardiovascular tissue engineering. Cell isolation requires the invasive harvesting of venous or arterial vessel segments prior to scaffold seeding, a technique which may not be preferable, especially in pediatric patients. This study evaluates cells isolated from human umbilical cord artery, umbilical cord vein and whole cord as alternative autologous cell sources for cardiovascular tissue engineering. METHODS: Cells were isolated from human umbilical cord artery (UCA), umbilical cord vein (UCV), whole umbilical cord (UCC) and saphenous vein segments (VC), and were expanded in culture. All three expanded cell groups were seeded on bioabsorbable copolymer strips and grown in vitro for 28 days. Isolated cells were characterized by flow cytometry, histology, immunohistochemistry, proliferation assays and compared to VC. Morphological analysis of the seeded polymer strips included histology, immunohistochemistry, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and uniaxial stress testing. RESULTS: UCA, UCV and UCC demonstrated excellent cell growth properties comparable to VC. Following isolation, all three cell groups showed myofibroblast-like morphology and characteristics by staining positive for alpha-smooth muscle actin (ASMA) and vimentin. Histology and immunohistochemistry of seeded polymers showed good tissue and extracellular matrix formation containing collagen I, III and elastin. TEM showed viable myofibroblasts and the deposition of collagen fibrils and progressive growing tissue formation, with a confluent surface, was observed in SEM. No difference was found among the mechanical properties of UCA, UCV, UCC and VC tissue engineered constructs. CONCLUSIONS: Tissue engineering of cardiovascular constructs by using UCA, UCV and UCC is feasible in an in vitro environment. Cell growth, morphology, characteristics and tissue formation were comparable between UCA, UCV, UCC and VC. UCC represent an attractive, readily available autologous cell source for cardiovascular tissue engineering offering the additional benefits of utilizing juvenile cells and avoiding the invasive harvesting of intact vascular structures.