The systemic inflammatory response (SIR) induced by CPB is the result of the activation of both cellular and humoral components. Inflammatory response activation may contribute to myocardial dysfunction, respiratory failure, renal insufficiency, confusion or stroke, atrial fibrillation and coagulopathy [1, 2]. Multiple studies noted a decrease in the inflammatory response with Mini-Bypass circuits [2, 13, 19, 25, 26].
The rationale of miniaturization of extracorporeal circuits is to reduce foreign surfaces as well as priming volume and, therefore, to limit SIR and alterations in perioperative hemostasis. This is achieved through suction blood separation, biocompatible coating, reduction of the total length of the circuit and reduction of prime volume. The mini-bypass system includes an integrated venous bubble trap, centrifugal pump, heat exchanger, and oxygenator and is designed for use with an autotransfusion/cell saving system for sequestration of aspiration blood.
Several studies have shown that in coronary bypass surgery, the mini-bypass system, used as a total CPB, reduces SIRS compared to standard CPB circuit [1, 10, 27, 28]. Whether the reduction of inflammatory response with the use of Mini-Bypass systems would result in improved clinical outcomes is still controversial. A systematic review and meta-analysis were conducted by Zangrillo and colleagues and they showed that the use of Mini-Bypass system results in decreased transfusion rate and cardiac and neurologic damage [29]. On the other hand, another meta-analysis by Winkler and colleagues and other prospective studies showed no difference in clinical outcomes with the use of Mini-Bypass [10, 19, 24, 30].
This heterogeneity in the results of Mini-Bypass pumps illustrates the need to study it use in high-risk patients to tease out its real benefit. We investigated in our study the effects of using the Mini-Bypass pump in diabetic patients and we showed that it decreased the use of vasogenic support postoperatively which can be explained by the initially illustrated studies that it decreases inflammatory response. Additionally, there was less use of Inotropic support postoperatively despite including patients with lower EF in this group that may indicate better myocardial protection. Although some of these findings have been shown previously, this is the first report of these findings in diabetic patients. This has a significant clinical impact since diabetic patients has more extensive vasculopathy and can benefit significantly from reduction of vasogenic drugs postoperatively. Reduction of inotropic support in diabetic patients with low EF also is very important since these hearts are chronically depleted from energy stores and exposing them to high doses of inotropic drugs may further increase their injury and delay their recovery. Although it did not reach statistical significance, the incidence of perioperative MIs showed a trend toward less MI rate in the Mini-Bypass group. This an important signal that need to be studies in the future in this diabetic high-risk group. Multiple pathophysiological explanation could be responsible for this finding including reduction of myocardial edema and the inflammatory response that may improve early graft patency. Another important signal detected in our study was the lower dose of intravenous insulin that was administered intraoperatively in the Mini-Bypass group to maintain normoglycemia, which could be explained by the reduction of insulin resistance as a result of the reduced inflammatory response with the use of these Mini-Bypass pumps.
This study has multiple limitations due to the nature of retrospective studies in addition to its small sample size but it focuses on a specific group of high-risk patients and its sheds the light on important clinical findings that need to be investigated on a higher scale.