Comparison of three infant venous reservoirs with vacuum-assisted venous drainage during varying levels of cardiotomy suction

Background: Vacuum-assisted venous drainage has gained widespread use within the pediatric perfusion community for use during cardiopulmonary bypass. It is questioned whether its efficiency may be compromised with application of excessive cardiotomy suction to the infant hard-shell venous reservoir. An in vitro simulation circuit was used to research this phenomenon. A comparison of three different infant hard-shell venous reservoirs also took place to determine if one reservoir type was more advantageous when handling cardiotomy suction. The reservoirs tested were the Maquet VHK 11000, Medtronic Affinity Pixie, and Terumo Capiox FX05. Methods: The in vitro simulation circuit consisted of a 1 L reservoir bag that was cannulated at one access point with an Edwards Lifesciences 10Fr aortic cannula and the other access area with an Edwards Lifesciences 10Fr right angle venous cannula and 12Fr right angle venous cannula that were joined together. Key points of measurement and response variables were the pressures on the connection of the venous cannulas, inlet of the venous reservoir, and flow through the venous line. Vacuum was applied and manipulated with a Maquet VAVD Controller to settings of −20 mmHg, −30 mmHg, –40 mmHg, −50 mmHg, and −60 mmHg. Cardiotomy suction was added at settings of 1 LPM, 2 LPM, 3 LPM, and 4 LPM. Values from each response variable were monitored and recorded. These data were utilized to compare the reservoirs with a random coefficient model for each response variable. Conclusions: There is an adverse effect of excessive cardiotomy suction on the efficacy of vacuum-assisted venous drainage in infant hard-shell venous reservoirs. There is no significant difference between the VHK 11000, Pixie, and FX05 regarding their ability to handle this occurrence. An important discovery was that the FX05 showed a greater transfer of vacuum to the venous cannulas and reservoir inlet.

Improving hemolysis levels associated with cardiotomy suction

Background: The major source of hemolysis during cardiopulmonary bypass (CPB) remains the cardiotomy suction.1 Previous research has shown that the combination of negative pressures and the massive air-blood interface exponentially increases hemolysis in suctioned blood. Objective: This research aims to decrease hemolysis by eliminating the air-to-blood interface by implementing the Venturi effect to create powerful suction. This research effort hypothesizes that the Venturi suction will result in less hemolysis, indicated by lower plasma free hemoglobin levels (PFH) compared to current vacuum suction. Method: The research hypothesizes that a paradigm approach to cardiotomy suction that utilizes the Venturi effect with shorter tubing lengths and weighted sucker tips will further reduce hemolysis. Results: The vacuum-suctioned blood showed PFH levels significantly increased from baseline levels (p=0.0039). Neither the Venturi nor paradigm groups showed PFH levels significantly increased from baseline levels (p=0.0625 and p=0.125, respectively). There was a significant difference in PFH levels among the three conditions (p<0.0001). The vacuum condition showed significantly higher levels of PFH compared to both the Venturi and the paradigm conditions (p<0.001 for both). There was no significant difference in the PFH levels between the Venturi and the paradigm groups (p=1.00). Conclusion: This study concludes that vacuum suction causes excessive hemolysis. A Venturi-powered suction system does not cause hemolysis and can be employed to reduce the damaging effects of vacuum suction on blood.

The effect of air exposure on leucocyte and cytokine activation in an in-vitro model of cardiotomy suction

Introduction: Cardiopulmonary bypass (CPB) is known to cause a systemic inflammatory and immune response. Objective: An in-vitro model of cardiotomy suction was designed to quantify the effects of incrementally increased air-blood exposure on leucocyte marker CD11b and cytokine activation in two common anticoagulants, heparin and citrate. Methods: Fresh human blood was exposed to increasing amounts of air flow for ten minutes. Leucocyte and cytokine levels were measured prior to and after ten minutes of air flow. Cytokine levels were also measured after air exposure when incubated for 24 hours at 37oC. Results: Leucocyte activation, measured by CD11b, was elevated between baseline and air flow rates up to 50 mL/min. After 10 minutes of air exposure, no measured cytokine levels were elevated. After 24 hours of incubation, cytokine levels of TNFα, IL-10, IL-6, and IL-8 were elevated. However, only IL-8 was significantly elevated in citrated blood, but not in heparinized blood, when compared to baseline samples that were also incubated for 24 hours. Conclusion: This study investigates CD11b levels in response to an air stimulus in blood that was anticoagulated with citrate or heparin. Exposure to an air stimulus activates leucocytes. Activation of CD11b was less when using heparin as an anticoagulant compared to citrate. Cytokine activation occurs with air stimulation, but levels do not immediately rise, indicating that time is required to generate free cytokines.

Leukocyte filtration of the cardiotomy suction. Does it affect systemic leukocyte activation or pulmonary function?

Background: Cardiopulmonary bypass is thought to propagate a global systemic response through contact with the non-physiological surfaces of the extracorporeal circuit, leading to the stimulation of leukocytes, their adherence to endothelial cells and the release of cytotoxic molecules. This, in turn, has been shown to accelerate pulmonary injury. This study tested a new leukocyte-filtration system (RemoweLL) against a conventional system with no leukocyte-depleting capacity to determine the efficacy of the filtration system and its effects on pulmonary function. Methods: Thirty patients underwent coronary artery bypass graft surgery using either the RemoweLL filtration system (15 patients) or a conventional cardiopulmonary bypass circuit (15 patients). Data were collected on the total number of leukocytes, their differentiation and activation, using the leukocyte adhesion integrin CD11b as a surrogate marker. Pulmonary function was assessed using the Alveolar-arterial Oxygenation Index (AaOI) and patients were categorized using the Berlin definition of acute respiratory distress syndrome (ARDS). Results: Both groups showed significant increases in leukocyte numbers during CPB (p<0.001), with no differences noted between the groups. CD11b showed a significant increase in both groups, with peak activation occurring at the end of CPB, but no difference between the groups (p=0.8). There was a trend towards lower AaOI increases in the filtration group, but this did not reach significance (p=0.075) and there was no difference in ARDS definitions (p=0.33). Conclusions: Leukocyte filtration of cardiotomy suction did not influence total leukocyte counts or activation as measured by CD11b upregulation. Furthermore, no evidence could be found to suggest improved pulmonary function.

The Early Inflammatory Response in a Mini–Cardiopulmonary Bypass System a Prospective Randomized Study

Objective The aim of this study was to compare the early systemic inflammatory response of the Resting Heart System (RHS; Medtronic, Minneapolis, MN USA), a miniaturized cardiopulmonary bypass (CPB) system, with two groups using a standard extracorporeal circulation system during on-pump coronary artery bypass grafting (CABG) surgery. Methods A total of 60 consecutive patients requiring CABG were prospectively randomized to undergo on-pump CABG using conventional CPB without cardiotomy suction (group A), conventional CPB with cardiotomy suction (group B), or the RHS (group C). Blood samples were collected at five time points: immediately before CPB, 30 minutes into CPB, immediately at the end of CPB, 30 minutes post-CPB, and 1 hour post-CPB. Inflammation was analyzed by changes in (a) levels of plasma proteins, including inflammatory cytokines (interleukin-6 [IL-6], IL-10, and tumor necrosis factor-α), chemokines (IL-8, monokine induced by interferon-γ, monocyte chemotactic protein-1, regulated on activation normal T cell expressed and secreted, and interferon-inducible protein-10), and acute phase proteins (C-reactive protein and complement protein 3); (b) biochemical variables (cardiac troponin I, hematocrit, and immunoglobulin G); and (c) cell numbers (leukocytes, neutrophils, and thrombocytes). Results The RHS showed more delayed secretion of the cytokines tumor necrosis factor-α and IL-10, chemokines monokine induced by interferon-γ (P < 0.001); IL-8, and interferon-inducible protein-10; and complement protein 3 than conventional CPB systems did. Median thrombocyte numbers were higher in the RHS group. Levels of cardiac troponin I, monocyte chemotactic protein-1, and IL-6 were lower in both the RHS and conventional CPB without suction than with suction. Levels of C-reactive protein and regulated on activation normal T cell expressed and secreted, plus leukocyte and neutrophil numbers, were similar in all groups. Conclusions The Medtronic RHS may induce less systemic inflammation than conventional CPB systems, particularly when cardiotomy suction was used, but it did not result in improved clinical benefit.