Cardiotomy Defoaming

The whole assembly should preferably remove from blood any bubbles or detritus of size 20 microns. We should, however, note here that, in an ultrasonic study of the relative efficiency of blood defoamer/filters, Pearson et al. [65] argue that 20-micron filters are desirable if microbubbles of size 20 microns are to be removed. The device of Servas et al. [44] could clearly be improved by use of a finer filter. 

FIGURE 11.5 Simplified plan view of defoamer and filter elements in typical cardiotomy reservoir. Both defoamer elements are sponge-like open-celled polyurethane foams coated with PDMS-hydrophohed silica antifoam. Inner particle filter has pore sizes in range of 50-90 microns and outer filter has pore size of 40 microns. (After Servas, F.M., Gremel, R.F., Ryan, T.C. (assigned to Shiley Inc.), US 4,743,371 10 May 1988, filed 28 February, 1986.) 

Despite use of these defoamer/fllters, the presence of lipids, PDMS antifoam particles, and microbubbles of air conspire to make cardiotomy blood the major canse of emboli in modem cardiopulmonary bypass surgery when nsing membrane oxygenators [67]. Superior outcomes can often be achieved by simply discarding that blood [67], although this is not usnally a practical option. 

Circuits, Which Include Membrane Oxygenators AND Cardiotomy/Venous Reservoirs 

Cardiopulmonary bypass snrgery also involves return of cardiotomy blood to the patient. Unlike the venons blood snpplied to the oxygenator, cardiotomy blood is, as we have discussed, likely to be both aerated and contain snrgical detritns. It is also likely to be flowing at a significantly slower rate than venous blood. 

---

Friedman [73] makes similar claims to those of Sacco et al. [72] but for an antifoam composed of lecithin and inorganic particles, including hydrophobed silica. Again it is used to coat a sponge-like defoamer element in a cardiotomy reservoir using a solution in ethanol or isopropanol or an emulsion in water. In practice, the reported antifoam performance in a cardiotomy defoamer appeared inconsistent unless admixed with PDMS-hydrophobed silica antifoam. 

FIGURE 11.6 Simplified schematic of typical combined cardiotomy and venous blood defoamer/reservoir assembly. Cardiotomy blood is both foamy and contaminated with surgical detritus and therefore requires more extensive defoaming/filtration. Deflector plates direct the flow of cardiotomy blood to minimize aeration. (After Raneri, J.J., Buckler, K.E., Stanley, C.L., Intoccia, P. (assigned to C.R.Bard Inc.), US 5,849,186 15 December 1998, filed 15 November 1996.)... 

---