Modified Ultrafiltration Should Not Be Routinely Used in Adult Cardiac Surgery
Abstract
Pediatric Literature
As the practice of ultrafiltration arose from pediatric cardiac surgery, much of the evidence to support MUF is from low-powered pediatric studies. Some early, single-center literature, as published by Schlünzen et al., observed that MUF, when compared with CUF, increased systolic blood pressure, hematocrit, arterial oxygen, and carbon dioxide levels when weaning from CPB, and prevented postoperative fluid overload.16 However, many others have reported mixed results. Sever et al., looking at
Protocol
One aspect of MUF that continues to remain nebulous is a clear-targeted clinical endpoint of when to stop ultrafiltration. Individual institutional practices and even individual perfusionist practices may vary greatly; a commonly reported target is a hematocrit of 35%-to-40%, although this is far from standardized.22 Additional uniformity is lacking in how to perform MUF in regard to vascular access, infusion ports, circuit configurations, filter types, and other strategies. The multiple
Inflammatory Mediators
Although much of the laboratory data supporting MUF arise from decreases in inflammatory mediators, much of the pediatric clinical evidence has failed to show a decrease in serum levels of complement activation (C3a levels) and tumor necrosis factor. as seen in laboratory animal models.27 In a series of 18 children undergoing cardiac surgery, Chew et al. found no differences in serum tumor necrosis factor-a, interleukin (IL)-1b, IL-1ra, complement and coagulation markers between children who
Anesthetic Impact
Modified ultrafiltration can alter the pharmacokinetics of drugs, such as antibiotics, in ways that are not expected with a standard traditional pharmacokinetic CPB model.30 A different ex vivo study demonstrated potentiation of dexmedetomidine, increasing circulating levels up to 16% after MUF compared with pre-MUF values.31 These alterations need to be taken into account in dosing regimens, but this is not commonly done. Another study demonstrated that MUF significantly increases plasma
Adult Literature
In the adult population, the data to support MUF over CUF are mixed. In a study of 18 patients, MUF has been shown to reduce levels of IL-8 implicated in acute respiratory distress syndrome after cardiac surgery.39 This same group, not surprisingly, found no differences in mortality outcomes or major complication rates, nor time to extubation or postoperative inotrope use. Another group found that, while proinflammatory cytokines, IL-6 and IL-8 were reduced in patients who had undergone MUF.
Conclusion
In conclusion, the authors argue that the clinical benefits of MUF remain elusive. Despite promising laboratory and patient data showing decreased serum inflammatory mediators, the highest-powered clinical trials and meta-analysis have not shown consistently improved outcomes in regard to time on ventilator, lung injury, other organ dysfunction, or length of stay in patients receiving MUF. Furthermore, minimizing transfusion by using MUF as a blood-conservation technology provided much promise