Improved adherence of genetically modified endothelial cells to small-diameter expanded polytetrafluoroethylene grafts in a canine model.

PURPOSE: A significant limitation to using genetically modified endothelial cells (ECs) to seed prosthetic grafts before implantation has been poor cell adherence to the graft lumen. Methodologic changes to improve cell adherence were evaluated in a canine carotid interposition graft model using 4 mm interior diameter expanded polytetrafluoroethylene. METHODS: ECs harvested from external jugular veins were grown in culture, with 80% of the cells from each culture transduced by incubation with an LXSN-type retroviral vector carrying a gene for human prourokinase and a neomycin resistance gene for selection in antibiotic G418. Control grafts had passive luminal coating with fibronectin and were seeded with transduced ECs immediately after G418 selection; these grafts were incubated for 2 days before implantation. Experimental grafts had fibronectin forcefully squeezed through the interstices and were seeded with ECs that had recovered in culture for 5 days after G418 selection; these grafts were incubated for 4 days before implantation. For each control (n = 9) and experimental (n = 12) graft, a graft prepared in the same fashion but seeded with the remaining autologous nontransduced cells was placed in the contralateral carotid artery. Grafts were explanted after 30 days and were evaluated for patency, thrombus-free surface area, and cell-free surface area. RESULTS: No significant differences in patency rates were seen between any groups. The thrombus-free surface area was improved for experimental grafts (90%) compared with control grafts (76%), but this improvement did not achieve statistical significance. The cell-free surface area for transduced cells on experimental grafts was 65% compared with 96% for control grafts (p = 0.021) and was comparable with that for nontransduced cells on both control grafts (62%) and experimental grafts (51%; p = 0.201). CONCLUSIONS: Adherence of genetically modified endothelial cells to small-diameter expanded polytetrafluoroethylene grafts in an in vivo physiologic flow model is significantly improved when cells have a more prolonged recovery from G418 selection, when the graft lumen is more uniformly coated with fibronectin before EC seeding, and when seeded grafts are left longer in culture before implantation to develop cell lining stability. The short-term patency rate of these seeded grafts is not affected by increased cell retention; long-term graft patency data and luminal healing require further evaluation.

Bedside tracheostomy in the intensive care unit.

OBJECTIVE: To prove that tracheostomy performed at the bedside in the intensive care unit is a safe, cost-effective procedure. DESIGN: Retrospective review of all adult patients undergoing elective bedside tracheostomy in the intensive care unit between January 1983 and December 1988. Two hundred four patients were identified. SETTING: A private 1200-bed tertiary care center with a 120-bed critical care facility. MAIN OUTCOME MEASURES: Major and minor perioperative complications, cost savings, and comparison of risk between bedside tracheostomy and that performed in the operating room. RESULTS: There were six major complications (2.9%): one death due to tube obstruction, two bleeding episodes requiring reoperation, one tube entrapment requiring operative removal, one nonfatal respiratory arrest, and one bilateral pneumothorax; and seven minor complications (3.4%): five episodes of minor bleeding, one tube dislodgement in a tracheostomy with a well-developed tract, and one episode of mucus plugging. One late complication (tracheal stenosis) was identified. CONCLUSIONS: Bedside tracheostomy in the intensive care unit can be performed with morbidity and mortality rates comparable to operative tracheostomy. In addition, it provides a significant cost savings for the patient.