Processing of small volumes in blood salvage devices

New technical developments such as a small Latham bowl, a continuous autotransfusion system, and a dynamic disk designed for postoperative autotransfusion raise hopes for a possible application of blood salvage in young children. However, the minimal blood volume for effective processing under clinically relevant conditions has yet to be determined.

Fresh blood from volunteer donations adjusted to a hematocrit (Hct) of 10% was used to test ELECTA (Sorin) equipped with a 55-mL bowl, C.A.T.S (Fresenius) in the pediatric program mode, and OrthoPAT (Haemonetics). Twenty-milliliter portions of red blood cells (RBCs) were added and processed under various conditions, including clinically relevant first filling and intermittent emptying. RBC recovery and availability and plasma elimination were calculated from the Hct, free hemoglobin, and total protein.

The main impediment to recovery and availability was the first filling. There, RBC recovery was significantly reduced, while it subsequently varied between 93 and 98%. To produce the first 30 mL of RBCs, ELECTA required 42 mL and C.A.T.S and OrthoPAT 62 mL owing to the dead space of the separation chamber or reservoir, respectively. RBC availability was much higher in subsequent processes, with only minimal differences between the three devices. They all consistently provided high plasma elimination rates.

The continuous system showed no advantage over a small Latham bowl. From the results it can be calculated that the limit for feasible cell salvage at present is an infant of 6 months. All three devices are suitable for the processing of small volumes, but have the scope for further optimization.