Development of a biomimetic microfluidic oxygen transfer device.

Blood oxygenators provide crucial life support for patients suffering from respiratory failure, but their use is severely limited by the complex nature of the blood circuit and by complications including bleeding and clotting. We have fabricated and tested a multilayer microfluidic blood oxygenation prototype designed to have a lower blood prime volume and improved blood circulation relative to current hollow fiber cartridge oxygenators. Here we address processes for scaling the device toward clinically relevant oxygen transfer rates while maintaining a low prime volume of blood in the device, which is required for clinical applications in cardiopulmonary support and ultimately for chronic use. Approaches for scaling the device toward clinically relevant gas transfer rates, both by expanding the active surface area of the network of blood microchannels in a planar layer and by increasing the number of microfluidic layers stacked together in a three-dimensional device are addressed. In addition to reducing prime volume and enhancing gas transfer efficiency, the geometric properties of the microchannel networks are designed to increase device safety by providing a biomimetic and physiologically realistic flow path for the blood. Safety and hemocompatibility are also influenced by blood-surface interactions within the device. In order to further enhance device safety and hemocompatibility, we have demonstrated successful coating of the blood flow pathways with human endothelial cells, in order to confer the ability of the endothelium to inhibit coagulation and thrombus formation. Blood testing results provide confirmation of fibrin clot formation in non-endothelialized devices, while negligible clot formation was documented in cell-coated devices. Gas transfer testing demonstrates that the endothelial lining does not reduce the transfer efficiency relative to acellular devices. This process of scaling the microfluidic architecture and utilizing autologous cells to line the channels and mitigate coagulation represents a promising avenue for therapy for patients suffering from a range of acute and chronic lung diseases.

Epidural anaesthesia for labour and caesarean section in a parturient with a single ventricle and transposition of the great arteries.

We describe a case of a 29-year-old parturient with a single ventricle and transposition of the great arteries who had lumbar epidural analgesia/anaesthesia with a local anaesthetic for labour, emergency Caesarean section and postoperative pain. Her outcome and that of her baby was successful. The anaesthetic techniques used in other parturients with similar congenital cardiac anomalies are reviewed.

Precordial Doppler diagnosis of haemodynamically compromising air embolism during caesarean section.

This is a report of a 39-year-old parturient who had a haemodynamically compromising venous air embolism during a repeat Caesarean section under lumbar epidural anaesthesia. The embolism occurred immediately after surgical incision during surgery in the superficial subcutaneous tissues. The diagnosis was made using intraoperative precordial ultrasonic Doppler monitoring which allowed early and successful treatment.