Impact of oxygenator design on hemolysis, shear stress, and white blood cell and platelet counts.

OBJECTIVE: To determine whether relative pressure drop, shear stress, hemolysis, and white blood cell and platelet counts are influenced by different oxygenator designs. To compare the oxygenator results with the average shear stress over an arterial cannula. DESIGN: Prospective; patients enrolled consecutively. SETTING: University hospital. PARTICIPANTS: Three groups of 12 adults patients, scheduled for routine cardiac surgery. INTERVENTIONS: Each group was submitted to a different oxygenator design: group 1 to a high-pressure hollow-fiber membrane oxygenator (Sarns Turbo); group 2 to a medium-pressure hollow-fiber membrane oxygenator (Cobe optima); and group 3 to a flat-sheet membrane oxygenator (Cobe Duo). MEASUREMENTS AND MAIN RESULTS: Although the investigated oxygenators have important differences in pressure drop and shear stress, no statistical differences were found in hemolysis generation or blood handling among the different groups. Actually, the study shows much higher shear stress levels over an average arterial cannula than over any of the evaluated oxygenators. CONCLUSIONS: The pressure drop over an oxygenator does not correlate well with shear stress and hemolysis because the dimensions of the system (radius and length) must be included in the calculation of shear stress from pressure drop.

D-901 neonatal oxygenator: a new perspective.

Five infants with congenital heart disease were perfused with the D-901 neonatal oxygenator at the time of their cardiac surgery. The ability to reduce the prime volume below the blood volume as well as the blood handling and gas transfer characteristics were studied. In all cases the prime volume was less than or equal to the blood volume of the patient. This resulted in a reduction in the use of homologous blood products. Due to the concept of the D-901 it was possible to adapt the tubing in such a way that a complete prime of 220 ml was obtained. The device had a maximum oxygen transfer of 45 ml/min. The maximum carbon dioxide removal was 50 ml/min at a blood gas ratio of one. The mean platelet count post bypass decreased to 91% of the baseline value. Mean free haemoglobin levels increased to 86 mg/100 ml at 120 minutes of bypass. We conclude that the D-901 oxygenator opens new perspectives for perfusion in small babies in terms of priming volume and use of homologous blood products while maintaining good gas transfer characteristics. However, larger series are necessary to expand our experience with this device and its limitations. No specific problems related to the device were encountered and all infants had an uneventful postoperative course.

Clinical evaluation of a new hollow fibre membrane oxygenator.

Twelve consecutive patients undergoing elective cardiac surgery were perfused with the Cobe Optima hollow fibre oxygenator. Gas transfer characteristics and blood handling were studied. The device had a maximum oxygen transfer of 315 ml/minute. The average shunt fraction was 4.5%, and was not influenced by blood-flow rate. Mean platelet count declined slightly to 91% of the baseline at the end of the study period. Haemolysis was evaluated by monitoring serum-free haemoglobin, serum haptoglobin and serum haemopexin. The evolution was as follows: free haemoglobin increased from 14 +/- 5 mg/100 ml to 85 +/- 0.8/100 ml (p = 0.01) at the end of bypass; haptoglobin decreased from 1.33 +/- 0.90 g/l to 0.89 +/- 0.15 g/l (p = 0.01); and haemopexin decreased from 0.84 +/- 0.13 g/l to 0.74 +/- 0.15 g/l (p = nonsignificant). In all patients the residual capacity of serum haptoglobin to protect against haemolysis was satisfactory. All patients had an uneventful postoperative course.