Five‐Year Experience With Mini‐Volume Priming in Infants ≤5 kg: Safety of Significantly Smaller Transfusion Volumes

Reducing the cardiopulmonary bypass (CPB) priming volume in congenital cardiac surgery is important because it is associated with fewer transfusions. This retrospective study was designed to compare safety and transfusion volumes between the mini‐volume priming (MP) and conventional priming (CP) methods. Between 2007 and 2012, congenital heart surgery using CPB was performed on 480 infants (≤5 kg): the MP method was used in 331 infants (MP group, 69.0%), and the CP method was used in 149 infants (CP group, 31.0%). In the MP group, narrow‐caliber (3/16″) tubing was used, and the pump heads were vertically aligned to shorten the tubing lengths. The smallest possible oxygenators and hemofilters were used, and vacuum drainage was applied. Ultrafiltration was vigorously applied during CPB to avoid excessive hemodilution. The mean age and body weight of the patients were 48 ± 41 (0–306) days and 3.8 ± 0.8 (1.3–5.0) kg, respectively. The total priming and transfusion volumes during CPB were lower in the MP group than in the CP group (141 ± 24 mL vs. 292 ± 50 mL, P < 0.001, and 82 ± 40 mL vs. 162 ± 82 mL, P < 0.001, respectively). In the MP group, the smallest priming volume was 110 mL. However, there was no significant difference in the lowest hematocrit level during CPB between the two groups (22 ± 3% vs. 22 ± 3%, P = 0.724). The incidence of postoperative neurological complications was not significantly different between the MP and CP groups (1.8% vs. 2.7%, P = 0.509). After adjustment for the Risk Adjustment for Congenital Heart Surgery category, body surface area, and age, MP was not an independent risk factor of postoperative neurological complications or early mortality (P = 0.213 and P = 0.467, respectively). The MP method reduced the priming volume to approximately 140 mL without increasing the risk of morbidity or mortality in infants ≤5 kg. The total transfusion volume during CPB was reduced by 50% without compromising hematocrit levels. We recommend the use of mini‐volume priming, which is a safe and effective method for reducing transfusion volumes.     

Apolipoprotein E Levels in Pediatric Patients Undergoing Cardiopulmonary Bypass

Apolipoprotein E (apoE) may play a critical role in modulating the response to neurological injury after cardiopulmonary bypass (CPB) in children. Plasma samples were collected from 38 pediatric patients. Half of the patients received nonpulsatile flow and the other half underwent pulsatile flow during CPB. Plasma samples were collected at three time points: at baseline prior to incision (T1), 1 h after CPB (T2), and 24 h after CPB (T3). The study included 38 pediatric patients undergoing heart surgery (mean age 2.5 ± 2.1 years). Baseline apoE levels were low (<30 μg/mL) in 21 patients (55%). ApoE levels were significantly decreased at 1 h after CPB compared with baseline (22 ± 14 vs. 34 ± 18 μg/mL, P = 0.001). At 24 h after CPB, apoE levels were significantly increased compared with baseline (47 ± 25 vs. 34 ± 18 μg/mL, P = 0.002). Pulsatile mode was associated with lower apoE levels at 24 h after CPB compared with nonpulsatile mode (38 ± 14 vs. 57 ± 29 μg/mL, P = 0.018). ApoE levels correlated negatively with pump time (r = ?0.525, P = 0.021) and cross‐clamp time (r = ?0.464, P = 0.045) at 24 h following CPB for the nonpulsatile group but not for the pulsatile group. In this cohort of young children with congenital heart disease, baseline apoE levels were low in the majority of patients prior to surgery. ApoE levels decreased further at 1 h after CPB, and then significantly increased by 24 h. The mode of perfusion and the duration of pump time and clamp time influence the apoE levels after CPB. An improved understanding of these mechanisms may translate into the development of new techniques to improve the clinical outcomes after pediatric CPB.     

The Effect of Cardiopulmonary Bypass and Hypothermic Circulatory Arrest on Hepatic Histology in Newborn Animals: An Experimental Study

Still little is known about the effect of cardiac surgery on neonatal hepatic tissue. We examined the effect of cardiopulmonary bypass (CPB) and the effect of deep hypothermic circulatory arrest (DHCA) on neonatal hepatic tissue. Liver biopsies of neonatal piglets were taken after CPB (n = 4), after DHCA (n = 5), and after surgery without CPB (non‐CPB; n = 3). Additionally, findings were compared to those of control piglets (n = 9). The liver specimens were fixed, stained with hematoxylin and eosin, and scored regarding inflammatory reaction, hepatocellular edema, and apoptosis. Inflammation score of treated groups was higher than in control; CPB 2.5 ± 0.5, DHCA 1.6 ± 0.4, non‐CPB 1.2 ± 0.6, control 0.4 ± 0.3 (P < 0.001 CPB and DHCA vs. control; P < 0.05 non‐CPB vs. control). Hepatic cell edema was more evident after DHCA (score 2.0 ± 0.4 vs. 0.2 ± 0.3 in control and 0.6 ± 0.5 after CPB; P < 0.001 and P < 0.05, respectively). The highest apoptotic cell count was in the non‐CPB group (22.3 ± 6.3 vs. 11.4 ± 3.6 in control and 8.9 ± 5.4 after CPB; P < 0.05). The present study showed that (i) surgical trauma induces hepatic cell apoptosis; (ii) CPB increases hepatic inflammatory reaction; and (iii) DHCA amplifies hepatic cell edema.     

Continuous Coronary Sinus Perfusion Reverses Ongoing Myocardial Damage in Acute Ischemia

Acute cardiogenic shock or cardiac arrest (CS/CA) before cardiopulmonary bypass (CPB) installation are life‐threatening events in acute coronary syndromes. We evaluated whether continuous retrograde warm‐blood perfusion (CRWBP) before aortic cross‐clamping (ACC), with immediate CPB installation may improve hospital results in these dreadful events. Hospital outcome of 18 coronary artery bypass grafting (CABG) (Group A) with CS/CA before CPB, with immediate CPB installation and CRWBP, has been compared with 24 CABG (Group B) with CS/CA undergoing only immediate CPB installation. No differences have been detected in the mean time to establish CPB (P = 0.655). Electrocardiography normalized in a significantly higher number of CRWBP (P = 0.0001). Group B showed longer CPB (116.2 ± 21.2 min vs. 157.8 ± 32.4; P = 0.0001) and postoperative intra‐aortic balloon pumping time course (36.2 ± 5.9 h vs. 77.8 ± 13.2; P = 0.0001). CRWBP reduced postoperative acute myocardial infarction (P = 0.004) and damage (P = 0.033), death (P = 0.026), and need for high inotropic support (0% vs. 37.5%; P = 0.003). Troponin I was significantly lower in Group A (P = 0.013 from coronary sinus; P ≤ 0.0001 at 12, 24, and 48 h postoperatively; P = 0.008 at 72 h), never reaching values suggestive of acute myocardial infarction. Group A had also lower lactate release from aortic declamping to 48 h postoperatively (P ≤ 0.0001). CRWBP improved postoperative left ventricular ejection fraction (EF) (P = 0.017) and wall motion score index (P = 0.041), whereas Group B showed a significant worsening of EF (P = 0.0001) and wall motion score index (P = 0.002). Patients in Group A had shorter intubation time (P = 0.0001), intensive therapy unit (ITU) stay (P = 0.001), and hospital stay (P = 0.0001). CRWBP reverses myocardial damage in patients with CS/CA during acute coronary syndromes, adding a straightforward benefit to hospital survival.     

Quantification of Operational Learning in Minimal Invasive Extracorporeal Circulation

Minimal invasive extracorporeal circulation (MiECC) has initiated important new efforts within science and technology towards a more physiologic perfusion. In this study, we aim to investigate the learning curve of our center regarding MiECC. We studied a series of 150 consecutive patients who underwent elective coronary artery bypass grafting by the same surgical team during the initial phase of MiECC application. Patients were randomly assigned into two groups. Group A (n = 75) included patients operated on MiECC, while group B (n = 75) included patients operated with conventional cardiopulmonary bypass (cCPB). The primary end‐point of the study was to identify whether there is a learning curve when operating on MiECC. The following parameters were unrelated with increasing experience, even though the results favored MiECC use: reduced CPB duration (102.9 ± 25 vs. 122.2 ± 33 min, P <0.001), peak troponin release (0.07 ± 0.02 vs. 0.1 ± 0.04 ng/mL, P < 0.01), peak creatinine levels (0.97 ± 0.24 vs. 1.2 ± 0.3 mg/dL, P < 0.001), duration of mechanical ventilation (14.1 ± 7.2 vs. 36.9 ± 59.8 h, P < 0.01) and ICU stay (2.1 ± 0.7 vs. 4.4 ± 6.4 days, P < 0.01). However, need for intraoperative blood transfusion showed a trend towards a gradual decrease as experience with MiECC system was accumulating (R² = 0.094, P = 0.007). Subsequently, operational learning applied to postoperative hematocrit and hemoglobin levels (R² = 0.098, P = 0.006). We identified that advantages of MiECC technology in terms of reduced hemodilution and improved end‐organ protection and clinical outcome are evident from the first patient. Optimal results are obtained with 50 cases; this refers mainly to significant reduction in the need for intraoperative blood transfusion. Teamwork from surgeons, anesthesiologists, and perfusionists is of paramount importance in order to maximize the clinical benefits from this technology.     

Continuous Metabolic Monitoring in Infant Cardiac Surgery: Toward an Individualized Cardiopulmonary Bypass Strategy

Cardiopulmonary bypass (CPB) in infants is associated with morbidity due to systemic inflammatory response syndrome (SIRS). Strategies to mitigate SIRS include management of perfusion temperature, hemodilution, circuit miniaturization, and biocompatibility. Traditionally, perfusion parameters have been based on body weight. However, intraoperative monitoring of systemic and cerebral metabolic parameters suggest that often, nominal CPB flows may be overestimated. The aim of the study was to assess the safety and efficacy of continuous metabolic monitoring to manage CPB in infants during open‐heart repair. Between December 2013 and October 2014, 31 consecutive neonates, infants, and young children undergoing surgery using normothermic CPB were enrolled. There were 18 male and 13 female infants, aged 1.4 ± 1.7 years, with a mean body weight of 7.8 ± 3.8 kg and body surface area of 0.39 m². The study was divided into two phases: (i) safety assessment; the first 20 patients were managed according to conventional CPB flows (150 mL/min/kg), except for a 20‐min test during which CPB was adjusted to the minimum flow to maintain MVO₂ >70% and rSO₂ >45% (group A); (ii) efficacy assessment; the following 11 patients were exclusively managed adjusting flows to maintain MVO2 >70% and rSO2 >45% for the entire duration of CPB (group B). Hemodynamic, metabolic, and clinical variables were compared within and between patient groups. Demographic variables were comparable in the two groups. In group A, the 20‐min test allowed reduction of CPB flows greater than 10%, with no impact on pH, blood gas exchange, and lactate. In group B, metabolic monitoring resulted in no significant variation of endpoint parameters, when compared with group A patients (standard CPB), except for a 10% reduction of nominal flows. There was no mortality and no neurologic morbidity in either group. Morbidity was comparable in the two groups, including: inotropic and/or mechanical circulatory support (8 vs. 1, group A vs. B, P = 0.07), reexploration for bleeding (1 vs. none, P = not significant [NS]), renal failure requiring dialysis (none vs. 1, P = NS), prolonged ventilation (9 vs. 4, P = NS), and sepsis (2 vs. 1, P = NS). The present study shows that normothermic CPB in neonates, infants, and young children can be safely managed exclusively by systemic and cerebral metabolic monitoring. This strategy allows reduction of at least 10% of predicted CPB flows under normothermia and may lay the ground for further tailoring of CPB parameters to individual patient needs.     

Effect of a Miniaturized Cardiopulmonary Bypass System on the Inflammatory Response and Cardiac Function in Neonatal Piglets

The cognitive impairment and hemodynamic instability after neonatal cardiac surgery with cardiopulmonary bypass (CPB) might be exacerbated by hemodilution. Therefore, this study investigated the impact of different bloodless prime volumes on the hemodynamics and the inflammatory response by a miniaturized CPB system in neonatal piglets. The bypass circuit consisted of a Capiox RX05 (Capiox Baby RX, Terumo Corp., Tokyo, Japan) oxygenator and 3/16 internal diameter arterial and venous polyvinyl chloride tubing lines, with a minimum 75 mL prime volume. Twelve 1‐week‐old piglets were placed on a mild hypothermic CPB (32°C) at 120 mL/kg/min for 2 h. The animals were divided into two groups, based on the volume of the prime solution. The priming volume was 75 mL in Group I and 175 mL in Group II. No blood transfusions were performed, and no inotropic or vasoactive drugs were used. The interleukin‐6 (IL‐6) and thrombin‐antithrombin (TAT) complex levels, as well as right ventricular and pulmonary functions, were measured before and after CPB. Group I had low levels of IL‐6 and TAT immediately after CPB (4370 ± 2346 vs. 9058 ± 2307 pg/mL, P < 0.01 and 9.9 ± 7.7 vs. 25.1 ± 8.8 ng/mL, P < 0.01, respectively). Group I had significantly improved cardiopulmonary function, cardiac index (0.22 ± 0.03 vs. 0.11 ± 0.05 L/kg/min, P < 0.001), and pulmonary vascular resistance index (7366 ± 2860 vs. 28 620 ± 15 552 dynes/cm⁵/kg, P < 0.01) compared with Group II. The miniaturized bloodless prime circuit for neonatal CPB demonstrated that the influence of hemodilution can reduce the subsequent inflammatory response. In addition, a low prime volume could therefore be particularly effective for attenuating pulmonary vascular resistance and right ventricular dysfunction in neonates.     

Comparative Effects of Pulsatile and Nonpulsatile Flow on Plasma Fibrinolytic Balance in Pediatric Patients Undergoing Cardiopulmonary Bypass

In the brain, the components of the fibrinolytic system, tissue plasminogen activator (tPA) and its endogenous inhibitor plasminogen activator inhibitor‐1 (PAI‐1), regulate various neurophysiological and pathological responses. Fibrinolytic balance depends on PAI‐1 and tPA concentrations. The objective of this study is to compare the effects of pulsatile and nonpulsatile perfusion on fibrinolytic balance in children undergoing pediatric cardiopulmonary bypass (CPB). Plasma PAI‐1 antigen and tPA antigen were measured in 40 children (n = 20 pulsatile and n = 20 nonpulsatile group). Plasma samples (1.5 mL) were collected (i) prior to incision, (ii) 1 h after CPB, and (iii) 24 h after CPB. PAI‐1 and tPA levels were measured at each time point. PAI‐1 and tPA levels were significantly increased at 1 h after CPB, followed by a decrease at 24 h. Nonpulsatile but not pulsatile CPB lowered PAI‐1 : tPA ratio significantly at 24 h (median PAI‐1 : tPA ratio 4.63 ± 0.83:1.98 ± 0.48, P = 0.03, for the nonpulsatile group and 4.50 ± 0.92:3.56 ± 1.28, P = 0.2, for the pulsatile group). These results suggest that pulsatile flow maintains endogenous fibrinolytic balance after pediatric cardiopulmonary bypass. Further studies are needed to define the clinical significance of these differences.     

Platelet Activating Factor and Thromboxane B2 Production After Cardiopulmonary Bypass

Platelet-activating factor (PAF) is believed to have a central role in the pathogenesis of ischemia-reperfision injury. The purpose of this study was to investigate the relationships among production of PAF, thromboxane B₂ (T_αB2), and cardiopulmonary sequelae in patients undergoing coronary artery bypass graft surgery (CABGS). Venous blood from nine patients (eight men, one woman) undergoing scheduled CABGS, was sampled from central venous catheters before anesthetic induction, pre-cardiopulmonary bypass (CPB), 10 and 30 minutes post-CPB, 10 and 30 minutes post-aortic declamping, and 120 minutes and 24 hours after the conclusion of CPB. Plasma levels of PAF and T_αB2 were determined by radioimmunoassay kits (Amersham Canada Ltd.). PAF and T_αB2 were significantly different between high-risk patients (group I; Canadian Cardiovascular Society class 3-4; n = 4) and low-risk patients (group II; Canadian Cardiovascular Society class 2; n = 5): group I PAF = 960 pg/mL, group II PAF = 159 pg/mL (P = 0.0029); group I T_αB2 = 320 pg/mL, group II T_αB2 = 229 pg/mL (P = 0.0262). Group I PAF was significantly greater than group II PAF: before CPB = 825 pg/mL (group I), 138 pg/mL (group II); during initiation of CPB = 1600-2015 pg/mL (group I), 158-200 pg/mL (group II) (P = 0.0143). Correlations between duration of CPB and peak PAF (r = 0.7049, P = 0.0339), peak PAF level, and time to extubation (r = 0.8863, P = 0.0079) were significant. PAF levels were different in patients requiring postoperative epinephrine (2124 ± 700 pg/mL) or dopamine (667 ± 266 pg/mL) (P = 0.0042). The production of PAF is determined by preoperative patient characteristics and duration of CPB. Increased levels of PAF in patients with unstable angina, left main coronary artery disease, or recent myocardial infarction are associated with the need for increased inotropy and prolonged ventilatory support following CABGS. The degree of PAF production during CPB may be a factor in postoperative instability in high-risk patients.     

Clinical Evaluation of New Generation Oxygenators With Integrated Arterial Line Filters for Cardiopulmonary Bypass

New generation oxygenators with integrated arterial line filters have been marketed to improve the efficacy of cardiopulmonary bypass (CPB). Differences in designs, materials, coating surfaces, pore size of arterial filter, and static prime exist between the oxygenators. Despite abundant preclinical data, literature lacks clinical studies. From September 2010 to March 2011, 80 consecutive patients were randomized to CPB using Terumo Capiox FX25 (40 patients, Group‐T) or Sorin Synthesis (40 patients, Group‐S) oxygenators. Pressure drop and gas exchange efficacy were registered during CPB. High‐sensitivity C‐reactive protein (hs‐CRP), white blood cells (WBCs), fluid balance, activated clotting time, international normalized ratio (INR), activated partial thromboplastin time (aPTT), fibrinogen, platelets (PLTs), serum albumin, and total proteins were measured perioperatively at different timepoints. Clinical outcome was recorded. Repeated measure analysis of variance and nonparametric statistics assessed between‐groups and during time differences. The two groups showed similar baseline and intraoperative variables. No differences were recorded in pressure drop and gas exchange (group‐P and group*time‐P = N.S. for all) during CPB. Despite similar fluid balance (P = N.S. for static/dynamic priming and ΔVolume administered intraoperatively), Group‐T showed higher hs‐CRP (group‐P = 0.034), aPTT (group‐P = 0.0001), and INR (group‐P = 0.05), with lower serum albumin (group‐P = 0.014), total proteins (group‐P = 0.0001), fibrinogen (group‐P = 0.041), and PLTs (group‐P = 0.021). Group‐T also showed higher postoperative bleeding (group‐P = 0.009) and need for transfusions (P = 0.008 for packed red cells and P = 0.0001 for fresh frozen plasma and total transfused volumes). However, clinical outcome was comparable (P = N.S. for all clinical endpoints). Both oxygenators proved effective and resulted in comparable clinical outcomes. However, Sorin Synthesis seems to reduce inflammation and better preserve the coagulative cascade and serum proteins, resulting in lower transfusions and post‐CPB inflammatory response.     

The effects of reactive hyperemia on stimulation of endothelium-derived nitric oxide in on-pump and off-pump coronary artery bypass surgeries

The purpose of this study is to compare the effects of cardiopulmonary bypass (CPB) on the endothelium‐derived nitric oxide (NO) levels in on‐pump and off‐pump coronary artery bypass surgeries. Forty consecutive patients were divided randomly into two groups depending on use of CPB in coronary artery bypass graft surgery (group 1: n = 20, off‐pump, and group 2: n = 20, on‐pump). The plasma endothelium‐derived NO levels were determined at baseline and after reactive hyperemia before and after surgery. Reactive hyperemia was induced by inflating a blood pressure cuff placed on the upper forearm, for 5 min at 250 mm Hg followed by a rapid deflation. Blood was collected at 1 min after cuff deflation from the radial artery on the same side. Preoperative use of all medications was recorded. The baseline plasma NO levels before operation were 17.10 ± 7.58 in group 1 and 15.49 ± 5.26 nmol/L in group 2. Before operation after reactive hyperemia, the plasma NO levels were 26.97 ± 11.49 in group 1 and 26.57 ± 12.87 nmol/L in group 2. Two hours after surgery, the plasma NO levels at baseline and after reactive hyperemia were not significantly different from each other (group 1: 18.03 ± 6.37 and group 2: 19.89 ± 9.83 nmol/L; group 1: 27.89 ± 18.36 and group 2: 39.13 ± 23.60 nmol/L, respectively; P > 0.05). A positive correlation was shown between preoperative nitroglycerine use and the postoperative plasma NO levels after reactive hyperemia (r = 0.51, P = 0.001). Linear regression analysis was performed (F = 4.10, R = 0.56, R² = 0.32, P = 0.008) and the only independent parameter that had an effect on postoperative plasma NO levels after reactive hyperemia was found to be preoperative nitroglycerine use (t = 3.68, P = 0.001). Coronary artery bypass surgery with CPB does not have significant effect on plasma endothelial derived NO levels. The postoperative plasma NO levels after reactive hyperemia significantly correlated with preoperative nitroglycerine use.     

Enhanced Blood Conservation and Improved Clinical Outcome After Valve Surgery Using Heparin-Bonded Cardiopulmonary Bypass Circuits

Abstract Background: Recently, heparin-bonded (HBC) cardiopulmonary bypass circuits (CPB) were formed to be associated with improved outcome after coronary artery bypass grafting. There are very few reports on the efficacy and safety of these circuits in valve surgery. Methods: A retrospective cohort study of all patient populations undergoing first time valve surgery from 1992 to 1995 in a tertiary teaching hospital. Outcomes of 120 patients undergoing valve surgery using HBC and lower anticoagulation HBC were compared to 232 patients treated with conventional circuits and full heparinization (nonheparin-bonded-circuit [NHBC]). Results: Postoperative 24-hour chest tube drainage (558 ± 466 mL vs 1054 ± 911 mL, p < 0.00001), and reoperation for bleeding (2.5% vs 8.2%, p = 0.04) were lower in the HBC group. HBC patients required significantly less transfusions (total donor exposure of 6.9 ± 13.0 units vs 18.6 ± 26.2 units, p < 0.00001). Multiple linear regression analysis identified CPB time as a predictor of increased homologous blood transfusions, and the use of HBC, a large body surface area, and elective procedure as predictors of decreased transfusions. Perioperative mortality was similar (HBC 2.5%, NHBC 4.7%, p = 0.24). Overall complications were lower in the HBC group (42% vs 56.2%, p = 0.02). Perioperative myocardial infarction (0.8% vs 1.3%, p = 0.58) and cerebrovascular accident (3.3% vs 3.9%, p = 0.53) were similar. Two (1.7%) HBC patients had valve re-replacement compared to none in the NHBC (p = 0.22). Multiple logistic regression model revealed that age and CPB time were associated with increased complications, and the use of HBC with reduced complications. Conclusion: Use of HBCs with lower anticoagulation in valve surgery resulted in a significant reduction of transfusion requirements and improved clinical outcome. Because of a potential for early mechanical valve thrombosis, until further data is available, conventional levels of systemic anticoagulation should be achieved when using HBC in valve surgery.     

The Benefits of High‐flow Management in Children With Pulmonary Atresia

The high‐flow management of cardiopulmonary bypass (CPB; ≥2.4 L/min/m²) is a standard strategy used at this institute for children with pulmonary atresia (PA) due to a fear that the blood flow may be diverted by the major/minor aortopulmonary‐collateral‐arteries and hypervascularization due to long‐term hypoxia. The purpose of this study was to describe the validity of high‐flow management in children with PA. The CPB records of 23 children with PA who underwent a definitive biventricular repair between Feb 2006 and Nov 2008 were retrospectively reviewed. The mean age at the operation was 33 ± 22 months. The blood‐pressure during bypass was controlled with the same protocol. The mean cooling‐temperature was 28.4 ± 3.7°C. The mean minimum hematocrit was 25.0 ± 3.4%. The mean maximum bypass flow index at the initiation, the mean maximum flow index during aortic cross‐clamping, the mean minimum flow index during aortic cross‐clamping, and the mean maximum flow index after rewarming were 3.1 ± 0.5, 3.1 ± 0.5, 2.6 ± 0.4, and 3.2 ± 0.4 L/min/m², respectively. The higher bypass flow indexes significantly correlated with the lower serum lactate levels. The lowest oxygen delivery during CPB had significant influences on the urine output during bypass (R = 0.547, P = 0.007), the serum lactate levels at the end of CPB (R = ?0.442, P = 0.035), and the postoperative thoracic effusion (R = ?0.459, P = 0.028). A bypass flow index of 2.4 L/min/m² may not be sufficient and the maximum requirement of bypass flow index may be 3.2 L/min/m² or more in this patient population.     

The optimal flow rate for antegrade cerebral perfusion during deep hypothermic circulatory arrest

The aim of this study is to compare cerebral protection using antegrade cerebral perfusion (ACP) with various flow rates during deep hypothermic circulatory arrest (DHCA) in a piglet model. Twenty‐three piglets were randomized to five groups: the control group (n = 3), DHCA group (n = 5), ACP25 group (n = 5), ACP50 group (n = 5), and ACP80 group (n = 5). Three control piglets did not undergo operations. Twenty piglets underwent cardiopulmonary bypass (CPB) and DHCA for 60 min at 20°C. ACP was conducted at 0, 25, 50, and 80 mL/kg/min in the DHCA, ACP25, ACP50, and ACP80 group, respectively. Serum S‐100B protein and neuron‐specific enolase were monitored, and brain tissues were assayed for the activities of caspase‐3 and stained for the evidence of apoptotic cellular injury. Rise in serum S‐100B level (post‐CPB—pre‐CPB) in the ACP50 group was significantly lower than that in the ACP80 group (P = 0.001). Caspase‐3 levels were significantly elevated in the ACP80 group compared with the ACP25 (P = 0.041) and ACP50 group (P = 0.01), while positive terminal deoxyneucleotidyl transferase‐mediated biotin‐dUTP nick end labeling reaction scores in the ACP80 group were significantly higher than those in the ACP25 (P = 0.043) and ACP50 group (P = 0.023). Cerebral protection effects of ACP at 25 and 50 mL/kg/min were superior to that of ACP at 80 mL/kg/min as determined by cerebral markers, immunology, and histology.     

Inhaled iloprost to control pulmonary artery hypertension in patients undergoing mitral valve surgery: a prospective, randomized-controlled trial

Background: Pulmonary hypertension (PHT) is common in patients undergoing mitral valve surgery and is an independent risk factor for the development of acute right ventricular (RV) failure. Inhaled iloprost was shown to improve RV function and decrease RV afterload in patients with primary PHT. However, no randomized‐controlled trials on the intraoperative use of iloprost in cardiac surgical patients are available. We therefore compared the effects of inhaled iloprost vs. intravenous standard therapy in cardiac surgical patients with chronic PHT. Methods: Twenty patients with chronic PHT undergoing mitral valve repair were randomized to receive inhaled iloprost (25 μg) or intravenous nitroglycerine. Iloprost was administered during weaning from cardiopulmonary bypass (CPB). Systemic and pulmonary haemodynamics were assessed with pulmonary artery catheterization and transoesophageal echocardiography. Milrinone and/or inhaled nitric oxide were available as rescue medication in case of failure to wean from CPB. Results: Inhaled iloprost selectively decreased the pulmonary vascular resistance index after weaning from CPB (208 ± 108 vs. 422 ± 62 dyn·s/cm⁵/m², P<0.05), increased the RV‐ejection fraction (29 ± 3% vs. 22 ± 5%, P<0.05), improved the stroke volume index (27 ± 7 vs. 18 ± 6 ml/m², P<0.05) and reduced the transpulmonary gradient (10 ± 4 vs. 16 ± 3 mmHg, P<0.05). In all patients receiving inhaled iloprost, weaning from CPB was successful during the first attempt. In contrast, three patients in the control group required re‐institution of CPB and had to be weaned from CPB using rescue medication. Conclusions: In patients with pre‐existing PHT undergoing mitral valve surgery, inhaled iloprost is superior to intravenous nitrogylycerine by acting as a selective pulmonary vasodilator, reducing RV afterload and moderately improving RV‐pump performance.     

Does multi-vessel off-pump coronary artery bypass grafting reduce post operative morbidity compared to on-pump CABG?

Background Cardiopulmonary bypass (CPB) may contribute to the complications and it is assumed that eliminating cardiopulmonary bypass has the potential of reducing post operative morbidity after coronary artery bypass grafting (CABG). The study was carried out to compare mortality and morbidity in the off-pump and on-pump CABG groups. Methods We prospectively analysed 200 patients undergoing CABG. Group A consists of 100 patients underwent multi-vessel off-pump CABG and group B consists of 100 patients underwent CABG with CPB. The incidence of complications (mortality, re-exploration for bleeding, myocardial infarction, atrial fibrillation, neurological events, new onset renal failure (s. creatinine>1.6 mg/dL) pulmonary complications, length of ICU stay and hospital stay were recorded, analysed and compared. Results OPCAB patients received 2.73±0.61 grafts/patient and on-pump CABG patients received 3.39±0.75 grafts/patient (p value<0.00001). There was no significant statistical difference in mortality, incidence of stroke between OPCAB and CABG with CPB patients. Length of ICU stay was 32.84±4.22 vs 44.85±7.18 hrs (p value<0.00001) and hospital stay was 6.52±0.69 vs 7.94±0.92 days (p value<0.00001) between group A and group B respectively. Incidence of atrial fibrillation was less in OPCAB group 7% vs 12% although it was statistically not significant (p value 0.33). It was observed in our study that there was no significant deference in worsening of existing renal failure between on-pump CABG and OPCAB 6% vs 2% (P value 0.28). Blood utilization was significantly less in OPCAB group (p value<0.001). Conclusion There was no statistically significant difference in terms of mortality, incidence of stroke and new onset renal failure in both groups. But there was lesser incidence of post operative atrial fibrillation, worsening of existing renal failure in off-pump group though statistically not significant. There was significant reduction in blood utilization, length of ICU and hospital stay in OPCAB group.     

Effect of modified ultrafiltration on bivalirudin elimination and postoperative blood loss after on-pump coronary artery bypass grafting: assessment of different filtration strategies

Abstract Objective: Bivalirudin has a short elimination half‐life of approximately 25 to 30 minutes, but no antidote is available. We assessed the effect of four different strategies of modified ultrafiltration after cardiopulmonary bypass on the bivalirudin elimination and postoperative blood loss. Methods: Five groups of seven patients undergoing elective “on‐pump” coronary artery bypass grafting were enrolled in this controlled randomized investigation. The filtration strategies varied with regard to the filtration flow, the filtrate volume, the addition of vacuum suction to the filter system, and the performance of hemodiafiltration. Filtration was started after weaning from cardiopulmonary bypass (CPB). The cumulative postoperative blood drainage at 12 hours was recorded. Results: Bivalirudin half‐life in the control group was 0.6 ± 0.11 hours, and the blood loss was 958 ± 472 mL. Hemofiltration with a constant flow of 300 mL/m² body surface area/min and a filtrate volume of 3000 mL reduced the elimination half‐life significantly to 0.47 ± 0.11 hours. Adding the process of dialysis to hemofiltration resulted in a half‐life of 0.52 ± 0.04 hours and reduced the 12‐hour postoperative blood loss significantly, compared to the control group, to 444 ± 220 mL. The other strategies failed to augment the bivalirudin elimination and postoperative drainage effectively. Conclusion: Zero‐balanced modified hemodiafiltration without addition of vacuum suction is effective in improving the elimination of bivalirudin after CPB and reducing the postoperative blood loss. Zero‐balanced hemodiafiltration should be considered for the augmented elimination of bivalirudin in complex surgical procedures with a high risk of bleeding complications. However, larger investigations are warranted to confirm these results.     

Cystatin C: influence of perfusion and myocardial injury on early (<24 h) renal function after pediatric cardiac surgery

Background: Cardiopulmonary bypass (CPB)‐associated renal dysfunction following cardiac surgery is well recognized. In patients with renal disease, cystatin C has emerged as a new biomarker which in contrast to creatinine (Cr) is sensitive to minor changes in glomerular filtration rate (GFR). Aim: We utilized cystatin C to investigate the association of CPB perfusion parameters with acute renal injury after pediatric cardiac surgery. Methods: Twenty children, aged 4–58 months (AVSD, n = 7; VSD, n = 9; and ASD, n = 4), were prospectively studied. Glomerular filtration rate was quantified postoperatively by creatinine clearance (first and second 12‐h periods; CrCl_0–12 and CrCl_12–24). Serum cystatin C and Cr were measured preoperatively and on days 0–3. Recorded CPB parameters included bypass duration (BP), perfusion pressure (PP), lowest pump flow (Q_min), lowest hematocrit, and corresponding lowest oxygen delivery (DO_{2 min}). Myocardial injury was determined by troponin‐I. Results: Postoperatively, GFR remained unchanged (CrCl_0–12 63.6 ± 37.0 vs CrCl_12–24 65.1 ± 27.5; P = 0.51) and only correlated with cystatin C (CrCl_0–12 vs cystatin C_Day0 [r = 0.58, P = 0.018] and Cr_Day0 [r = 0.09, P = 0.735]). Cr and cystatin C increased postoperatively to peak on days 2 and 3, respectively (Cr_PreOp 31 ± 6.9 vs Cr_Day2 36.9 ± 12.2, P = 0.03; cystatin C_Day0 0.83 ± 0.27 vs cystatin C_Day3 1.45 ± 0.53, P = 0.02). Increased cystatin C was significantly associated with BP (P = 0.001), mean PP (P = 0.029), Q_min (P = 0.005), troponin‐I (P < 0.001), and DO_2min <300 ml·min^?1·m^?2 (P = 0.007). Receiver–operator cutoff >1.044 mg·l^?1 for cystatin C exhibited 100% sensitivity and 67% specificity for detecting renal dysfunction, defined as GFR <55 ml·min^?1·1.73 m^?2. Conclusions: Cystatin C is a sensitive marker of early renal dysfunction following pediatric heart surgery. Variations in bypass parameters, myocardial injury, and ultimately critical oxygen delivery are significantly associated with the degree of renal impairment.     

Contemporary Oxygenator Design: Shear Stress‐Related Oxygen and Carbon Dioxide Transfer

Design of contemporary oxygenators requires better understanding of the influence of hydrodynamic patterns on gas exchange. A decrease in blood path width or an increase in intraoxygenator turbulence for instance, might increase gas transfer efficiency but it will increase shear stress as well. The aim of this clinical study was to examine the association between shear stress and oxygen and carbon dioxide transfer in different contemporary oxygenators during cardiopulmonary bypass (CPB). The effect of additional parameters related to gas transfer efficiency, that is, blood flow, gas flow, sweep gas oxygen fraction (FiO₂), hemoglobin concentration, the amount of hemoglobin pumped through the oxygenator per minute—Qhb, and shunt fraction were contemplated as well. Data from 50 adult patients who underwent elective CPB for coronary artery bypass grafting or aortic valve replacement were retrospectively analyzed. Data included five different oxygenator types with an integrated arterial filter. Relationships were determined using Pearson bivariate correlation analysis and scatterplots with LOESS curves. In the Capiox FX25, Fusion, Inspire 8F, Paragon, and Quadrox‐i groups, mean blood flows were 4.8 ± 0.9, 5.3 ± 0.7, 4.9 ± 0.7, 5.0 ± 0.6, and 5.7 ± 0.6 L/min, respectively. The mean O₂ transfer/m² membrane surface area was 44 ± 14, 51 ± 9, 60 ± 10, 63 ± 14, and 77 ± 18, respectively, whereas the mean CO₂ transfer/m² was 26 ± 14, 60 ± 22, 73 ± 29, 74 ± 19, and 96 ± 20, respectively. Associations between oxygen transfer/m² and shear stress differed per oxygenator, depending on oxygenator design and the level of shear stress (r = 0.249, r = 0.562, r = 0.402, r = 0.465, and r = 0.275 for Capiox FX25, Fusion, Inspire 8F, Paragon, and Quadrox‐i, respectively, P < 0.001 for all). Similar associations were noted between CO₂ transfer/m² and shear stress (r = 0.303, r = 0.439, r = 0.540, r = 0.392, and r = 0.538 for Capiox FX25, Fusion, Inspire 8F, Paragon, and Quadrox‐i, respectively, P < 0.001 for all). In addition, O₂ transfer/m² was strongly correlated with FiO₂ (r = 0.633, P < 0.001), blood flow (r = 0.529, P < 0.001), and Qhb (r = 0.589, P < 0.001). CO₂ transfer/m² in contrast was predominately correlated to sweep gas flow (r = 0.567, P < 0.001). The design‐dependent relationship between shear stress and gas transfer revealed that every oxygenator has an optimal range of blood flow and thus shear stress at which gas transfer is most efficient. Gas transfer is further affected by factors influencing the O₂ or CO₂ concentration gradient between the blood and the gas compartment.     

Evaluation of Membrane Oxygenators and Reservoirs in Terms of Capturing Gaseous Microemboli and Pressure Drops

An increasing amount of evidence points to cerebral embolization during cardiopulmonary bypass (CPB) as the principal etiologic factor of neurologic complications. In this study, the capability of capturing and classification of gaseous emboli and pressure drop of three different membrane oxygenators (Sorin Apex, Terumo Capiox SX25, Maquet QUADROX) were measured in a simulated adult model of CPB using a novel ultrasound detection and classification quantifier system. The circuit was primed with 1000 mL heparinized human packed red blood cells and 1000 mL lactated Ringer's solution (total volume 2000 mL, corrected hematocrit 26–28%). After the injection of 5 mL air into the venous line, an Emboli Detection and Classification Quantifier was used to simultaneously record microemboli counts at post‐pump, post‐oxygenator, and post‐arterial filter sites. Trials were conducted at normothermic (35°C) and hypothermic (25°C) conditions. Pre‐oxygenator and post‐oxygenator pressure were recorded in real time and pressure drop was calculated. Maquet QUADROX membrane oxygenator has the lowest pressure drops compared to the other two oxygenators (P < 0.001). The comparison among the three oxygenators indicated better capability of capturing gaseous emboli with the Maquet QUADROX and Terumo Capiox SX25 membrane oxygenator and more emboli may pass through the Sorin Apex membrane oxygenator. Microemboli counts uniformly increased with hypothermic perfusion (25°C). Different types of oxygenators and reservoirs have different capability of capturing gaseous emboli and transmembrane pressure drop. Based on this investigation, Maquet QUADROX membrane oxygenator has the lowest pressure drop and better capability for capturing gaseous microemboli.