Clinical evaluation of the Sarns membrane oxygenator

A new membrane oxygenator, developed by Travenol Laboratories, has been introduced by Sarns/3M. The oxygenator is constructed of microporous polypropylene hollow fibres wound into a gas transfer module with an effective surface area of 1.8m2 and a total priming volume of 320ml. This was made possible by using computer-aided design techniques. Blood flow is perpendicular over the fibre in the module while the gas flow is directed within the fibres. The unit contains an integral stainless steel heat exchanger mounted beneath the fibre module. A selection of collapsible venous reservoirs is available to fulfil various patient requirements. The oxygenator and venous reservoir bag are mounted on a wire frame holder that can be arranged in any direction on the heart lung machine. The circuit was primed with 1800ml of a balanced electrolyte solution, 200ml of 25% albumin and 200ml of 25% mannitol, to which 4000 units of beef lung heparin were added. The 1000ml reservoir was used in all cases. Seventeen consenting adult patients undergoing elective cardiac surgery participated in the clinical evaluation. Haematology and organ function studies indicated no significant changes attributable to the oxygenator. The mean postbypass plasma-free haemoglobin elevation was 8.2mg/dl. The mean postbypass haematocrit and platelet count reduction were 21 % and 27% respectively, indicating that platelet count tended to follow haemodilution with minimal loss. There were no gas exchange nor acid-base problems encountered. The mean PaO2 and PaCO 2 were 267mmHg and 42mmHg respectively with a maximum O2 transfer of 241 ml/min during the study.