Paracorporeal artificial lung: perioperative management for survival study in sheep

An artificial lung may offer a bridge to recovery or transplant. Utilizing our recently developed paracorporeal artificial lung (PAL) in survival studies in sheep, we critically review our perioperative/anesthetic protocol. Adult Suffolk ewes (n = 15) underwent general anesthesia induced by ketamine (7-15 mg/kg, im) and isoflurane by mask, then intubated and maintained by 4.0-5.0% isoflurane titrated to mean arterial pressure (MAP) 70-110 mm Hg. After a latissimus-sparing thoracotomy and systemic heparinization (200 IU/kg), arterial grafts were anastomosed to the proximal and distal main pulmonary artery in an end-of-graft to side-of-artery fashion. A snare was passed around the pulmonary artery between anastomoses. When the snare was tightened, full pulmonary blood flow was diverted through the cannulae and immediately through the PAL. Perioperative crystalloids included a 500-mL prime, lactated Ringer's (LR) titrated to CVP 5-7 mm Hg, and a heparin infusion (activated clotting time [ACT] 250-300 s). Buprenorphine (0.3 mg im tid) controlled postoperative pain. Hemodynamic parameters, arterial blood gases (ABGs), and ACTs were measured every 6 h. Thirteen of 15 sheep survived the operation and were extubated in less than 20 min. Two groups were studied for up to 7-day survival. Both groups underwent immediate connection to the PAL diverting full pulmonary blood flow. Group 1 (n = 8) underwent immediate connection to a rigidly housed PAL, and 4 of 8 demonstrated immediate right heart failure. In Group 2 a compliance chamber was added to the PAL inflow, and 6 of 7 had stable hemodynamic function for the duration of the study. Incremental improvements in the PAL and our anesthetic and perioperative care have resulted in reliable survival in adult sheep allowing for artificial lung development.