Kevin McCusker

Clinical evaluation of minimized extracorporeal circulation in high-risk coronary revascularization: impact on air handling, inflammation, hemodilution and myocardial function

Objective: We examined intraoperative microembolic signals (GME), inflammatory response, hemolysis, perioperative regional cerebral oxygen saturation (rSO2), myocardial protection and desorbed protein amount on oxygenator fibers in high-risk patients undergoing coronary revascularization (CABG) with minimized and conventional cardiopulmonary bypass (CPB). Methods: Over a ten-month period, 40 Euroscore 6+ patients undergoing CABG were prospectively randomized to one of the two perfusion protocols (N=20): Group 1: minimized extracorporeal circuits (Mini-CPB) (ROCsafe MPC, Terumo, Ann Arbor, MI, USA) and Group 2: conventional extracorporeal circuits (CECC) (Capiox SX18, Terumo, USA). Serum creatinine kinase-MB (CKMB), free hemoglobin, interleukin-6 (IL-6) and C3a levels were measured. Blood samples were collected at T1: following induction of anesthesia; T2: thromboelastography control; T3:15 min after commencement of CPB; T4: before cessation of CPB; T5: 15 min after protamine reversal and T6: ICU. Results: Serum IL-6 levels were significantly lower in the Mini-CPB group at T4 and T5 and C3a levels were significantly less in the Mini-CPB group at T3, T4 and T5 vs. CECC (p<0.01). CKMB levels in coronary sinus blood demonstrated well preserved myocardium in the Mini-CPB group. Percentage expression of neutrophil CD11b/CD18 levels were significantly lower in the Mini-CPB group at T4 and T5 (p<0.05). There were no significant differences in air handling characteristics or free plasma hemoglobin levels in either circuit. rSO2 measurements were significantly better at T3 and T4 in the Mini-CPB vs. CECC (p<0.05) and always higher in the Mini-CPB during follow-up. Blood protein adsorption analysis of oxygenator membranes demonstrated a significantly increased amount of microalbumin on CECC fibers (p<0.05). Conclusion: Mini-CPB provided a comfort and safety level similar to conventional control via satisfactory air handling, attenuated inflammatory response and hemodilution, with a better clinical outcome in patients undergoing high-risk CABG.

Influence of hematocrit and pump prime on cerebral oxygen saturation in on-pump coronary revascularization

Background: The couplings between cerebral oxygenation (rSO2), on-pump hematocrit and circuit prime are explored in this study. Methods: Thirty-eight consecutive patients undergoing coronary revascularization with cardiopulmonary bypass (CPB) were matched on preoperative hematocrit < 40% and >40% (n=16). Similarly, six blood prime patients were matched with six crystalloid prime patients. Hematocrit and rSO2 levels were then compared on CPB. Results: The pre-operative hematocrit >40% group retained higher levels on pump run (p < 0.01) and significantly higher rSO2 prior to CPB (64.8±9.6 versus 73.2±7.3), and on and off CPB (61.1±8.8 versus 67.4±6.4). Blood priming increased absolute rSO2 (2.3± 6.3 versus − 10.9±5.9) and% rSO2 (4.7±11.8 versus −14.2±7.4%) in the low hematocrit group. Conclusion: Blood primes are instrumental in high-risk and low preoperative hematocrit patients in preventing cerebral oxygen desaturation during initiation and maintenance of CPB.

Clinical and biomaterial evaluation of hyaluronan-based heparin-bonded extracorporeal circuits with reduced versus full systemic anticoagulation in reoperation for coronary revascularization.

Objective This prospective randomized study compares full and reduced heparinization on novel hyaluronan-based heparin-bonded circuits vs. uncoated controls under challenging clinical setting including biomaterial evaluation. Methods 100 patients undergoing reoperation for coronary artery bypass grafting were allocated into two equal groups (n = 50): Group one was treated with hyaluronan-based heparin bonded preconnected circuits (Vision HFOGBS, Gish, California, USA) and Group two with identical uncoated controls (Vision HFO, Gish, USA). In the study group, half of the patients (n = 25) received low-systemic heparin (125 IU/kg, ACT >250 s) or full dose like control group. Blood samples were collected after induction of anesthesia (T1) and heparin administration before cardiopulmonary bypass (CPB) (T2), 15 min after initiation of CPB (T3), before cessation of CPB (T4), 15 min after reversal with protamine (T5), and the first postoperative day at 08: 00 h (T6). Results Platelet counts were preserved significantly better at T5, T6 in hyaluronan groups (P < 0.05 vs. control). Serum IL-2 levels were significantly lower at T4, T5 in both hyaluronan groups and C3a levels at T4 and T5 only in low-dose group (P < 0.05). Troponin-T levels in coronary sinus blood demonstrated well preserved myocardium in hyaluronan groups. No significant differences in thrombin–antithrombin levels were observed between full and low-dose heparin groups at any time point. Amount of desorbed protein was 1.41 ± 0.01 in full and 1.43 ± 0.01 in low dose vs. 1.78 ± 0.01 mg/dl in control (P < 0.05). Conclusion Hyaluronan-based heparin-bonded circuits provided better clinical outcome and less inflammatory response compared with uncoated surfaces. Reduced systemic heparinization combined with hyaluronan-based heparin-bonded circuits is feasible and clinically well tolerated.

Recent advances in biocompatible surface-modifying additives for cardiopulmonary bypass.

The institution and conduct of cardiopulmonary bypass (CPB) have become safe and efficient over the past few decades and focus is now on reducing the deleterious inflammatory effects of CPB. The primary endpoint of current technological advances, at least for the present, would be to improve the biocompatibility of the CPB circuit to a level that matches the low systemic inflammatory response evoked when, for instance, coronary artery bypass grafting (CABG) is performed off pump. To borrow an example from the automotive sporting industry, each member of the pit crew of a Formula 1 racing team delivers undivided attention to improving and optimizing each component, while operating in a team spirit. As each component is refined to its maximum, the inevitable end result is a highly efficient product and service. Using a similar approach in our ‘quest for the ultimate CPB circuit’, the cardiovascular industry has made excellent strides over the past few years in improving every component of the CPB circuit, particularly in the area of condensation of the circuit and in surface-modifying agents (SMA). The circulating area of the circuit and nature of the contact surface presented to blood during CPB are the two most important determinants of the degree of systemic inflammatory response evoked. As improvements in one closely parallel advances in the other, we shall discuss briefly the recent developments in both to aid in understanding the current state-of-theart and future directions of CPB. Biochemical compatibility parameters for SMA

Comparison of polymethoxyethylacrylate-coated circuits with leukocyte filtration and reduced heparinization protocol on heparin-bonded circuits in different risk cohorts.

Objectives: The relative benefits of strategic leukofiltration on polymer-coated and low-dose heparin protocol on heparin-coated circuits were studied across EuroSCORE patient risk strata for three different cohorts. Methods: In a prospective, randomized study, 270 patients undergoing coronary artery bypass grafting were allocated into three groups (n = 90): Group 1 -polymethoxyethylacrylate-coated circuits+leukocyte filters; Group 2 -polypeptide-based heparin-bonded circuits with reduced heparinization; and Group 3 -Control: uncoated circuits. Each group was further divided into three subgroups (n = 30), with respect to low- (EuroSCORE 0-2), medium- (3-5), and high- (6+) risk patients. Blood samples were collected at T1: following induction of anesthesia; T2: following heparin administration; T3: 15 min after CPB; T4: before cessation of CPB; T5: 15 min after protamine reversal; and T6: ICU. Results: In high-risk cohorts, leukocyte counts demonstrated significant differences at T4 and T5 in Group 1, and at T4 in Group 2. Platelet counts were preserved significantly better at T4 and T5 in both groups (p <0.05 versus control). Serum IL-2 and C3a levels were significantly lower at T3, T4 and T5 in Group 1, and T4 and T5 in Group 2 (p <0.05). Postoperative bleeding, respiratory support time and incidence of atrial fibrillation were lower in the study groups versus control. Cell counts on filter mesh and heparin-coated fibers/circuits were significantly higher in the high-risk cohorts versus uncoated fibers. Phagocytic capacity increased on filter mesh, especially in high-risk specimens. SEM evaluation demonstrated better preserved coated circuits. Conclusion: Leukofiltration and coating reduced platelet adhesion, protein adsorption, atrial fibrillation and reduced heparinization acted via modulation of systemic inflammatory response in high-risk groups.

Perioperative blood conservation strategies in pediatric patients undergoing open-heart surgery: impact of non-autologous blood transfusion and surface-coated extracorporeal circuits

Background: The aim of this study was to explore the relative clinical and biomaterial effects of blood transfusions (Tx) and novel low-prime, surface-coated circuitry on perioperative outcome in a pediatric population undergoing cardiac surgery with cardiopulmonary bypass (CPB). Methods: Over a 12-month period, 80 patients weighing >10 kg undergoing ventricular septal defect (VSD) repair with CPB were prospectively randomized into two groups according to the type of CBP circuit used, then each randomized group was enrolled into two groups again, according to the need for transfusion (N=20): Group 1- Tx-free procedures on low-prime, surface-coated extracorporeal circuitry (FX05, Terumo); Group 2- procedures requiring Tx on coated circuitry; Group 3- Tx-free procedures with standard uncoated circuitry (D902, Sorin); Group 4 (Control)- procedures requiring Tx on uncoated circuitry. Blood samples were collected at baseline (T1), at the end of the CPB (T2) and 24 h (T3) postoperatively. rSO2 desaturation risk score >6000 (Invos, Somanetics) was calculated by multiplying rSO2 <50% by time. Results: IL-6 levels (pg/ml) were significantly lower in Groups 1 and 3 versus control at T2 (13±4; 17±5 versus 33±8; p<0.05). CD11b/CD18 levels (%) were significantly lower in Group 1 (12±4) versus control (25±8) at T2 (p<0.05). Respiratory support time (h) was significantly less in Group 1 (11.4±6) versus control (19.8±7) (p<0.05). rSO2 desaturation risk >6000 (%) was 15.7±9 in Group 1 and 26.8±11 in control (p<0.05). Conclusion: Allogenic Tx amplifies the CPB-related inflammatory response. It is feasible to do congenital procedures safely without Tx for patients weighing >10 kg by using combined blood management strategies.