Residual blood in neonatal oxygenators after drainage

The objective of this investigation was to measure the quantity of residual blood remaining in neonatal cardiopulmonary bypass (CPB) circuits after they had been drained and to assess the overall significance with regards to total patient blood volume. The residual blood volume left in three infant/neonatal CPB circuits-Medtronic Minimax 3381 (Group MM; n = 5), Polystan Safe Micro (Group SM; n = 6), and Terumo Capiox 308 (Group CX; n = 3)--after they had been drained was determined. This was done by using an electronic scale to weigh the circuit before setup and after CPB when all possible blood was recovered from it. Total priming volume, estimated patient blood volume, residual blood volume, surgical blood loss in theater, and autogeneic blood usage were recorded in each case. Mean residual blood volumes measured were MM = 161 ml (SD 27 ml), SM = 103 ml (SD 19 ml), and CX = 133 ml (SD 15 ml). These volumes were significant, because calculations show that the volume of red cells lost in the circuit is equivalent to fourteen percent of the total patient blood volume. In view of this, neonatal oxygenator design should be minimized to reduce the priming volume and more consideration should be given to ease of residual blood recovery.