An experimental study was conducted to investigate whether a segment of autogenous esophagus with its lumen supported by an expandable metallic stent (EMS) could be successfully used as a tracheal substitute. Seven rings of the cervical trachea were circumferentially removed and reconstructed by interposing a pedicled segment of the esophagus with an EMS in six mongrel dogs. The interposed esophagus was observed endoscopically at various stages after the operation. By 1 month, the EMS was found to be buried under the esophageal mucosa, and the lumen was patent. The dogs died 5, 17, 61, 92, 210, and 478 days after the operation, but the cause of death could not be determined by postmortem examination and no respiratory tract complications were detected. The results of this study indicated that a segment of the esophagus with its lumen supported by an EMS could work as a reliable tracheal substitute, though its practical use is not clinically feasible. Nevertheless, we conclude that some autogenous material other than the esophagus with its lumen supported by an EMS could provide a feasible method for tracheal replacement.
We have succeeded in synthesizing a new type of totally artificial oxygen carrier which was produced by covering oil droplets (microsphere) with synthetic hemes (LH-M). We studied its oxygen-transporting ability in hemorrhagic dogs. Four beagles weighing about 8 kg were studied. Under controlled ventilation, exchange-transfusion of 30 ml/kg was carried out. Cardiac output, hemoglobin and LH-M concentration in the blood, and blood gas were measured to 5 hours after intravenous injection of LH-M solution. LH-M delivered 15.7 to 22.3 ml/min (11 to 16%) of oxygen to the tissue and 5.5 to 8.2 ml/min (11 to 17%) of oxygen was consumed from LH-M to 5 hours after intravenous injection. Its half-life time in the blood stream was about 12 hours. It was confirmed that LH-M transported oxygen and released it to the tissue in vivo.
Two types of totally artificial oxygen carriers were produced (1)by embedding synthetic lipidhemes (as oxygen carriers) in bilayers of liposomes as vehicles of lipidhemes (L/H) and (2)by covering clinically available fat droplets (triglyceride microspheres) with synthetic lipidhemes (LHM). Fat droplets were used as vehicles of lipidhemes. Their oxygen carrying ability in vivo was examined in beagles undergoing hemorrhagic shock. L/H delivered 15.7 to 19.2% of total oxygen delivery. From 12.7 to 24.4% of total oxygen consumption was from L/H. LHM delivered 11.6 to 7.3% of total oxygen delivery. From 13.1 to 16.4% of total oxygen consumption was from LHM. These totally synthetic red blood cell substitutes can be candidates for future clinical testing.
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