Pulsatile Augmentation Device for Extracorporeal Circulation

Abstract: A device has been designed, constructed, and tested to provide pulsatile pressure/flow to a standard extracorporeal bypass circuit. The pulsatile augmentation device is pneumatically driven similar to an artificial heart ventricle except that there are no valves. It is constructed of polyurethane by vacuum forming and high frequency welding. Drivers used are a modified Arrow-Kontron in-traaortic balloon pump or the Utah artificial heart driver. In vitro testing with fresh bovine blood demonstrated acceptable blood compatibility and hemodynamic function. In vivo testing for 4 h in a right and left heart extracorporeal bypass circuit showed good pulse augmentation in pulmonary and systemic bypass circuits. The device shows promise for adding pulse to standard cardiopulmonary bypass and to extracorporeal right heart circulatory assist circuits.     

Activation of coagulation during hemodialysis: effect of blood lines alone and whole extracorporeal circuit

Activation of coagulation during hemodialysis (HD) is a relevant clinical problem, especially when patients at risk of bleeding are treated. However, little is known about the relative contribution of the various components of the circuit to the thrombotic process. Thus, an experimental model was developed that is aimed at evaluating biochemical markers of coagulation activation at different times and sites throughout the HD circuit. A HD blood-tubing set with integrated arterial and venous chambers (cartridge-line set) was used, which was added with the following sampling points: at the beginning of the arterial line (P1), before the blood pump (P2), after the blood pump (P3), and at the end of the venous line (P4). A bypass system allowed us to circulate the blood only into the blood lines for the first 20 min of the extracorporeal circulation. The extracorporeal circuit was rinsed with 1.7 L of heparinized saline (2,500 IU/L) that was completely discarded before patient connection. A continuous administration of unfractionated heparin (500-800 IU/h) without a starting bolus was adopted as a low heparin extracorporeal treatment. Samples were collected before the start of the extracorporeal circulation from the fistula needle (T0P0), after 5 (T1), 10 (T2), and 20 min (T3) from P1, P2, P3, and P4. After 20 min, the blood was returned to the patient using only saline and HD was then started, circulating the blood through the dialyzer. Further samples were obtained from P1 and P4 after 5 (T4) and 210 min (T5). Plasma levels of coagulation activation markers-thrombin-antithrombin complex (TAT) and prothrombin fragment 1 + 2 (F1 + 2)-were evaluated in all the samples in 12 stable HD patients. In each patient, the activated partial thromboplastin time (APTT) was measured at T0P0 and T1-T5 from P1. No significant changes were found at any time as far as F1 + 2 is concerned. However, TAT levels increased over time only after the start of HD, suggesting that the latter test could be more useful in order to detect coagulation activation during HD. The same experiments performed with nonheparin-primed extracorporeal circuit showed similar results. The blood lines used did not significantly activate coagulation during the first 20 min, whereas only 5 min of blood circulation throughout the whole circuit increased TAT values, which still remained lower than previous reports, even after 210 min of treatment.     

Hematological effects of a low-prime neonatal cardiopulmonary bypass circuit utilizing vacuum-assisted venous return in the porcine model

Limiting hemodilution in neonates is difficult when extracorporeal circuits require priming volumes that are 2 to 3 times the blood volume of the newborn patient. This extreme hemodilution contributes to the development of significant postbypass coagulation disturbances. The purpose of this project was to design a low-prime neonatal bypass circuit and evaluate the coagulation status after reduced hemodilution. The null hypothesis stated there is no significant difference in the measured coagulation parameters between the low-prime circuit and the standard high-prime circuit. Four neonatal piglets (2-4 kg) were divided into two groups and placed on cardiopulmonary bypass using either a low- (200 ml) or high-prime (500 ml) circuit. Both groups were cooled to 20 degrees C, and, following cardioplegic arrest, underwent circulatory arrest for 20 minutes. The low-prime circuit used vacuum-assisted venous drainage, which permitted the circuit to be at the patient level. The high-prime circuit required fresh washed donor red blood cells to maintain the hematocrit in the desired range of 15-20%. The platelet count on bypass decreased by 60 +/- 1.0% in the low-prime group versus 79.6 +/- 0.1% in the high-prime group. Following bypass, the platelet count was reduced by 38.3 +/- 14.3% in the low-prime versus 60.2 +/- 2.6% in the high-prime group. During rewarming, the mean heparinase activated clotting time (ACT) increased 5.1% above baseline in the low-prime group and 53.5% above baseline in the high-prime group. Mean plasma-free hemoglobin levels increased 40.4 mg/dl in the low-prime group versus 62.1 mg/dl in the high-prime group during bypass. This laboratory evaluation of a low-prime neonatal circuit demonstrates that coagulation disturbances often present in neonates can be reduced with the use of a low-prime circuit.     

Improvement of bypass circuit biocompatibility: comparison and combination of heparin-coated circuit and nitric oxide gas infusion

OBJECTIVES: Nitric oxide (NO) gas infusion to the oxygenator, as well as heparin-coated bypass circuits, have been reported to attenuate blood activation induced by the interaction with the artificial surfaces of an extracorporeal bypass circuit. Using a mock circulation model, we compared the effect of each and also evaluated the effect of their combination on attenuating bypass-induced blood activation. METHODS: A miniature closed bypass circuit was primed with diluted fresh human blood and perfused for 180 minutes using a centrifugal pump. NO gas (0, 50, or 100 ppm) was infused to the oxygenator sweep gas of either a non-heparin-coated or a heparin-coated circuit. Platelet counts, beta-thromboglobulin, platelet factor 4, complement-3 activation products and granulocyte elastase were measured at 0, 30, 60, 120, and 180 minutes after starting the perfusion. RESULTS: One hundred ppm of NO was statistically equivalent to the heparin-coated circuit for attenuating bypass-induced blood activation, and a combination of the two significantly surpassed the results of either modification alone. Fifty ppm of NO alone provided only a slight attenuation of blood activation as compared with the non-heparin-coated circuit, though the difference was not significant. A combination of 50 ppm NO and the heparin-coated circuit did not significantly enhance the effects of the heparin-coated circuit alone. CONCLUSIONS: The combination of NO gas infusion and heparin-coated circuits appears to be a useful and promising modification for enhancing the attenuation of bypass-induced blood activation, though the optimal dose of NO infusion in terms of effectiveness and adverse effects to the whole body remains to be established.     

A failure mode effect analysis on extracorporeal circuits for cardiopulmonary bypass

Although many refinements in perfusion methodology and devices have been made, extracorporeal circulation remains a contributor to neurological complications, bleeding coagulopathies, use of blood products, as well as systemic inflammatory response. With the exposure of these adverse effects of cardiopulmonary bypass, the necessity to re-examine the safety of extracorporeal circuits is vital. A failure mode effect analysis (FMEA) is a proven proactive technique developed to evaluate system effect or equipment failure. FMEA was used to evaluate the six different types of extracorporeal circuits based on feedback from five clinical experts. Cardiovascular device manufacturers, the Veteran's Administration National Center for Patient Safety, and the Joint Commission on Accreditation of Healthcare Organizations recommend the use of FMEA to assess and manage risks in current and developing technologies and therapies. This analysis investigates the safety of six types of extracorporeal circuits used in coronary revascularization, including the newer miniaturized extracorporeal circuits. The FMEA lists and ranks the hazards associated with the use of each cardiopulmonary bypass extracorporeal circuit type. To increase the safety of extracorporeal circuits and minimize the effects associated with cardiopulmonary bypass, perfusionists must incorporate FMEA into their clinical practice.     

Blood conservation in cardiac operations. Cell separation versus hemofiltration

The effects of hemoconcentration performed during and after extracorporeal circulation by either centrifugation (cell separation group, n = 20) or hemofiltration (n = 20) were investigated in 40 patients undergoing elective aorta-coronary bypass grafting. Interest was focused on the quality of the blood concentrated from the blood remaining in the extracorporeal circuit and on the reaction of the patients after retransfusion of the concentrated products. Hemofiltration was easy to perform and produced whole blood quicker than the cell separation technique. Coagulation studies revealed no significant differences in heparin concentration, levels of fibrinogen and antithrombin III, or platelet counts. Various coagulation parameters tended to normalize completely and more quickly after hemofiltration than after centrifugation. None of the patients had severe bleeding postoperatively. Free hemoglobin levels were not affected by hemofiltration; elastase concentration was higher only immediately after retransfusion of the concentrated blood, with no effect on organ function. We conclude that both methods were effective means of hemoconcentration during extracorporeal circulation and in salvaging the diluted pump blood after extracorporeal circulation. Loss of plasma fraction is an important disadvantage in the centrifugation technique, which can be avoided by hemofiltration; derangement in colloid osmotic pressure and coagulation parameters was less pronounced after hemofiltration. Costs were lower, as well. Therefore, when a high volume of cardioplegic solution and two-stage cannulation are used, hemofiltration seems to be the method of choice for blood conservation during cardiac operations.     

Veno-right ventricular bypass as total extracorporeal lung assistance. An experimental study

Efficacy of veno-right ventricular bypass as a total extracorporeal lung assistance was studied for a period of 24 hours in six healthy pigs with a mean weight of 60 kg. A covalently bonded heparin-coated extracorporeal membrane oxygenation system and a roller pump were used for the bypass. No local or systemic heparin was administered. The bypass was established with an open chest with two 28F venous cannulas and one 24F arterial cannula. The arterial cannula was placed in the right ventricle across the tricuspid valve. With the lung function totally disabled, this extracorporeal lung assistance maintained normal systemic arterial and mixed venous blood gases during the entire 24-hour period in all the animals. No significant tricuspid insufficiency was observed, and the animals maintained normal central hemodynamics. There was no hemolysis, and the platelet counts remained essentially unaltered. Multiple foci of clot formation were observed in all the oxygenators, but no macroscopic thrombosis or embolization was seen either in the heart or in the lungs. A veno-right ventricular bypass offers total extracorporeal lung assistance in 60 kg juvenile pigs for a period of 24 hours. Tricuspid valve competence is an important prerequisite for the success of this procedure.     

Coating of extracorporeal circuit with heparin does not prevent sequestration of propofol in vitro

Propofol is sequestered in extracorporeal circuits, but the factors responsible for the phenomenon are mostly unknown. We have compared two extracorporeal circuits (oxygenators, reservoirs and tubings) coated with heparin with two corresponding uncoated circuits for their capacity to sequester propofol in vitro. Three experiments were conducted with each circuit. The circuit was primed with a mixture of Ringer's acetate solution and whole blood, and the study conditions (pump flow, temperature, pH) were standardized. Propofol was added to the solution to achieve a concentration of 2 micrograms ml-1. These studies were followed with concentrations of 10- and 100-fold to assess possible saturation of propofol binding. Serial samples were obtained from the circulating solution for measurement of propofol concentration. Propofol concentrations decreased to 22-32% of the initial predicted concentration of 2 micrograms ml-1 in the circuits (no significant difference between circuits). With greater concentrations, the circuits did not become saturated with propofol, even with the highest predicted concentration of 200 micrograms ml-1. We conclude that propofol was sequestered in extracorporeal circuits in vitro, irrespective of coating the circuit with heparin.      

A Simplified Single Pump Circuit for Cardiac Bypass with Autogenous Oxygenation

A simplified extracorporeal circulation (ECC) assemblage with autogenous oxygenation (AO) using a single centrifugal pump was tested in dogs. The transpulmonary gradient was obtained by increasing pressure in the right atrium through volume expansion and decreasing it in the left atrium by collecting the blood from the pulmonary veins in a reservoir placed below the level of the animal, generating a siphon effect. This arrangement dispenses with a right side pump. The heart was electrically fibrillated after perfusion was started and defibrillated at the end of the bypass. This ECC circuit allowed the maintenance of adequate hemodynamic and blood gas parameters during the bypass. The operating field and the mobility of the heart were equivalent to that of conventional cardiopulmonary bypass (CPB). We conclude that the use of a single centrifugal pump simplifies the autogenous oxygenation approach, making it a practical choice for the coronary artery bypass graft (CABG) procedure.     

Pharmacological inhibition of plasma coagulation and platelet activation during experimental long-term perfusion

OBJECTIVE: During extracorporeal circulation, initial contact between blood and the artificial surface of the circuit induces an overall activation of the hemostatic system. The objective of this study was to investigate the combined effect of epoprostenol (PGI (2) ), nitric oxide (NO) and nafamostat mesilate (FUT-175, a serine protease inhibitor), on plasma coagulation and platelet activation during experimental long-term perfusion. DESIGN: Two identical extracorporeal life support (ECLS) circuits were primed with fresh, heparinized human blood, and circulated for 24 h. FUT was given with a bolus dose of 85 mg/l blood at the initiation of the experiment and thereafter as a continuous infusion of 14 mg/l/h. PGI (2), at a rate of 2.4 microg/l/h, was also administered to the experimental circuit, and 120 ppm NO gas was added to the oxygenator sweep gas. The other circuit was used as a control. RESULTS: Higher platelet count and platelet membrane expression of GPIb were found in the experimental circuits as compared with control circuits. The levels of thrombin/antithrombin III complex (TAT) and prothrombin fragment 1 + 2 (F1 + 2) increased significantly over time in the control circuits but remained low in the experimental circuits. Plasma levels of plasminogen activator inhibitor 1 (PAI-1) decreased rapidly in both circuits but were higher in the control circuits at each time point studied. CONCLUSION: The activation of platelets and of the coagulation system encountered during extracorporeal perfusion is consistently inhibited by a combination of PGI (2), NO and FUT-175. The combination of these drugs appears to be more effective than each drug separately.     

Electrostatic potential generated during extracorporeal pump prime circulation before cardiopulmonary bypass initiation

The development of electrostatic potentials generated during cardiopulmonary bypass (CPB) procedures using polyvinylchloride (PVC) tubing in conjunction with roller pumps has been previously documented. The resulting damage from the electrostatic discharge (ESD) has been reported to affect gas transfer devices, but details of potential damage to electronic components commonly used during extracorporeal circulation have not been similarly described. The purpose of this study was to measure the ability of a triboelectric potential to be generated from a primed, circulating, adult CPB pump before the initiation of CPB. Two identical adult CPB circuits were assembled: one incorporating a roller pump and the second incorporating a centrifugal pump mechanism. Primed pumps were circulated (1-6 LPM), and evidence of generated triboelectric potentials was evaluated using a digital multimeter (Fluke 8062 A). The ESD generated from an adult CPB circuit using a roller head configuration elicited a charge in excess of 600 DC V. An identical circuit constructed with a centrifugal pump mechanism did not produce any measurable charge. Sensitive electrical components in the CPB hardware platform may be damaged by ESD potential spikes of this magnitude. Preventative measures, such as circuit charge dissipation, may reduce the potential for such damage when using PVC tubing.     

Single-cannula venovenous bypass for respiratory membrane lung support

Clinical use of a single cannula would make extracorporeal membrane oxygenation simpler and less aggressive. It would probably limit the occurrence of the complications of currently used techniques (double-cannula, venoarterial, or venovenous bypass). In this experimental study an original system is described that is composed of a single cannula, an alternating clamp, and a nonocclusive roller pump, the characteristics of which permit its use as a venous reservoir. To overcome the limitations of the oxygenation in any venovenous bypass, we used the method of "apneic oxygenation" through the natural lungs, which we previously proved efficient in infants and children. The optimal setting of the alternative clamp was first tested in vitro to obtain the maximal flow in the circuit and the minimal amount of recirculation. The single-cannula bypass then was compared with a two-cannula circuit regarding the efficiency of carbon dioxide removal and the hemodynamic consequences. At less than 50% of the maximal speed of the pump, flows were equivalent in both types of circuits. The efficiency of carbon dioxide removal was only slightly decreased by the use of a single cannula (30 +/- 2 ml/min versus 36 +/- 2 ml/min with two cannulas). This could easily be offset by increasing the gas flow/blood flow ratio in the oxygenator. Arterial carbon dioxide tension was maintained at normal levels in both types of circuits. Hemodynamic condition was only slightly affected by the alternative flow of the bypass. This system of single-cannula membrane lung support thus seems to be adequate for clinical use.     

Conversion from extracorporeal membrane oxygenation to total cardiopulmonary bypass: a simplified method

Pediatric patients who have preoperative hemodynamic instability or postoperative cardiac decompensation may frequently require the use of extracorporeal membrane oxygenation (ECMO) for stabilization of cardiac and respiratory function. While ECMO can be a therapeutic treatment for the congenital pediatric patient, it does not allow the additional functions of a complete cardiopulmonary bypass (CPB) circuit should subsequent surgical revision in the operating room be required. This paper will discuss our approach to converting the ECMO circuit to total cardiopulmonary bypass allowing the use of cardioplegia, cardiotomy suction, and modified ultrafiltration. This technique allows the conversion to CPB without ceasing support to the critically ill patient or exposing them to additional blood products or surface area in the priming of a new extracorporeal circuit. In addition, this circuit design allows for the resumption of ECMO support utilizing the same circuit if the patient necessitates it.     

Nafamostat mesilate reduces blood cell adhesion to cardiopulmonary bypass circuits: an in-vitro study

Nafamostat mesilate (FUT-175) is a protease inhibitor, working as an inactivator of coagulation, fibrinolysis and platelet aggregation. Although FUT-175 directly blocks contact factors in coagulation, it also may decrease activation of humoral cascade systems when used in cardiopulmonary bypass circuits. We performed an in vitro study using fresh human blood in the following cardiopulmonary bypass circuits: standard circuit (C), biosurfaced circuit (B) and standard circuit containing FUT-175 (F). Each circuit was primed with 500 ml of electrolyte solution and 500 ml of fresh blood. Cardiopulmonary bypass was performed using a roller pump for four hours in two sets of each circuit configuration. Platelet factors (platelet count and beta-thromboglobulin), coagulation factors (thrombin-antithrombin III complex and fibrinopeptide A), fibrinolysis factors (alpha 2-plasmin inhibitor complex and alpha 2-plasmin inhibitor), complement factors (C3a, C4a), free hemoglobin, and granulocyte elastase were measured at the beginning and end of the study. Hemocytograms were measured concurrently. The FUT-175 group showed significantly lower levels of the measured indices than the biosurfaced group in thrombin-antithrombin III complex (7.4 +/- 2.1 vs. 54.9 +/- 38.1 ng/ml), fibrinopeptide A (7.2 +/- 2.0 vs. 20.2 +/- 14.6 ng/ml), beta-thromboglobulin (1940 +/- 250 vs. 2438 +/- 314 ng/ml) and free hemoglobin (25.2 +/- 14.3 vs. 73.8 +/- 18.4 mg/dl). There were no significant differences between Group F and Group B in platelet count, C3a, C4a and granulocyte elastase, although these indices were significantly lower in Groups F and B when compared to Group C.(ABSTRACT TRUNCATED AT 250 WORDS)     

Heparin-coated circuits and reduced systemic anticoagulation applied to 2500 consecutive first-time coronary artery bypass grafting procedures

BACKGROUND: In contrast to the widespread popularity of off-pump techniques for coronary artery bypass grafting, our institution has chosen a different strategy, emphasizing improvements in the technology for extracorporeal circulation, as well as simplifying surgical and clinical management. The clinical short-term results of this approach were analyzed. METHODS: The on-pump strategy includes routine use of heparin-coated circuits combined with low systemic heparinization (activated coagulation time of more than 250 seconds), intention of total revascularization within limited ischemic times and pump times, minimal use of blood transfusions, early extubation, and rapid postoperative recovery. The data from the first 2,500 consecutive first-time coronary artery bypass grafting patients (January 1998 to February 2002) treated with this protocol were retrospectively analyzed. RESULTS: There were 487 female (median age 68 years) and 2013 male (median age 64 years) patients. A median of four (one to nine) (mean 4.5 +/- 1.2) distal anastomoses were created, and the median aortic cross-clamp time and pump time were 34 and 54 minutes, respectively. At least one internal mammary artery was used in 99.7% of the patients. Blood or bank blood products were given to 118 patients (4.7%). Median extubation time was 1.5 hours. The stroke rate was 0.8%, transient neurologic deficits occurred in 0.6% of the patients, and the incidence of perioperative myocardial infarction was 1.1%. By the fifth day, 91% of the patients were ready for discharge. Seven patients (0.28%) died during their hospital stay. CONCLUSIONS: Coronary artery bypass grafting with heparin-coated cardiopulmonary bypass circuits and reduced systemic anticoagulation resulted in excellent clinical results, with minimal blood transfusions and rapid postoperative mobilization. The high number of grafted coronary arteries indicates complete revascularization in most patients, which is known to be a significant predictor of long-term event-free survival.     

Optimizing the Circuit of a Pulsatile Extracorporeal Life Support System in Terms of Energy Equivalent Pressure and Surplus Hemodynamic Energy

Abstract: The nonpulsatile blood flow obtained using standard cardiopulmonary bypass (CPB) circuits is still generally considered an acceptable, nonphysiologic compromise with few disadvantages. However, numerous reports have concluded that pulsatile perfusion during CPB achieves better multiorgan response postoperatively. Furthermore, pulsatile flow during CPB has been consistently recommended in pediatric and high‐risk patients. However, most (80%) of the total hemodynamic energy generated by a pulsatile pump is absorbed by the components of the extracorporeal circuit and only a small portion of the pulsatile energy is delivered to the patient. Therefore, we considered that optimizations of CPB unit and extracorporeal life support (ECLS) system circuit components were needed to deliver sufficient pulsatile flow. In addition, energy equivalent pressure, surplus hemodynamic energy, and total hemodynamic energy, calculated using pressure and flow waveforms, were used to evaluate the pulsatilities of pulsatile CPB and ECLS systems.     

Pulsatility Produced by the Hemodialysis Roller Pump as Measured by Doppler Ultrasound

Microbubbles have previously been detected in the hemodialysis extracorporeal circuit and can enter the blood vessel leading to potential complications. A potential source of these microbubbles is highly pulsatile flow resulting in cavitation. This study quantified the pulsatility produced by the roller pump throughout the extracorporeal circuit. A Sonosite S‐series ultrasound probe (FUJIFILM Sonosite Inc., Tokyo, Japan) was used on a single patient during normal hemodialysis treatment. The Doppler waveform showed highly pulsatile flow throughout the circuit with the greatest pulse occurring after the pump itself. The velocity pulse after the pump ranged from 57.6 ± 1.74 cm/s to ?72 ± 4.13 cm/s. Flow reversal occurred when contact between the forward roller and tubing ended. The amplitude of the pulse was reduced from 129.6 cm/s to 16.25 cm/s and 6.87 cm/s following the dialyzer and venous air trap. This resulted in almost nonpulsatile, continuous flow returning to the patient through the venous needle. These results indicate that the roller pump may be a source of microbubble formation from cavitation due to the highly pulsatile blood flow. The venous air trap was identified as the most effective mechanism in reducing the pulsatility. The inclusion of multiple rollers is also recommended to offer an effective solution in dampening the pulse produced by the pump.     

Autotransfusion in coronary artery bypass grafting: disparity in laboratory tests and clinical performance.

OBJECTIVE: Autotransfusion during and after cardiac surgery is widely performed, but its effects on coagulation, fibrinolysis, and inflammatory response have not been known in detail. METHODS: Hemostatic and inflammatory markers were extensively studied in 40 coronary artery bypass patients undergoing a consistent intraoperative and postoperative autotransfusion protocol. An identical autotransfusion protocol was applied to 4916 consecutive coronary patients and the overall clinical results were evaluated in this large patient population. RESULTS: The autologous blood pooled before bypass remained nearly inactivated after storage. A slight elevation of thrombin-antithrombin complex and prothrombin fragment 1.2, as well as plasmin/alpha(2)-antiplasmin complex was found in the content of the extracorporeal circuit after surgery, indicating thrombin formation and fibrinolytic activity. Also some increase of beta-thromboglobulin was present. In the mediastinal shed blood, complete coagulation, as evidenced by the absence of fibrinogen, had taken place and all parameters described above were extremely elevated. However, no thrombin activity was detected. As for the inflammatory response, moderately increased levels of complement activation products, terminal complement complex, and interleukin-6 traced in the extracorporeal circuit reached very high levels in mediastinal shed blood. Autotransfusion of the residual extracorporeal circuit blood and the mediastinal drainage was followed by elevation of most of these markers in circulating plasma. On the other hand, no correlating harmful effects were recorded in the study patients or in the consecutive 4916 patients. Coagulation disturbances were rare and allogeneic transfusions were required in fewer than 4% of all patients. CONCLUSIONS: The hemostatic and immunologic systems were moderately activated in the autologous blood remaining in the extracorporeal circuit, whereas the mediastinal shed blood was highly activated in all aspects. However, autotransfusion had no correlating clinical side-effects and the subsequent exposure to allogeneic blood products was minimal.     

Changes in platelets and blood coagulation during prolonged ECLA with a heparin bonded hollow fiber membrane lung

Effects of the heparin bonded artificial membrane lung and circuit on blood coagulation were investigated during prolonged extracorporeal lung assist on goats. A veno-venous bypass ECLA was performed on 18 goats up to 10 days. Twelve of them (Group I) were with a heparin bonded device and the other six (Group II) were with the usual device. In Group I, heparin was continuously infused at a rate of 15.2 units.kg-1.hr-1 to maintain the activated coagulation time, ACT, at around 130 sec., while in Group II, 25.5 units.kg-1.hr-1 of heparin was necessary to maintain ACT at about 200 sec. to prevent blood coagulation in the bypass circuit. Platelets decreased significantly in Group I (by 50% of pre ECLA value) as well as in Group II, but aggregation activity in Group I was higher than in Group II. Fibrinopeptide A and antithrombin III showed no significant difference between the two groups. Autopsy showed no significant pathological findings. ECLA, with a heparin bonded surface, showed excellent blood compatibility and required only a little systemic administration of heparin. The heparin bonded bypass circuit will enable safer ECLA even in patients with some bleeding sites.     

Impact of heparin bonding on pediatric cardiopulmonary bypass: a prospective randomized study

BACKGROUND: Heparin-coated circuits reduce the inflammatory response to cardiopulmonary bypass in adult patients; however, little is known about its effects in the pediatric population. Two studies were performed to assess this technology's impact on inflammation and clinical outcomes. METHODS: In a pilot study, complement and interleukins were measured in 19 patients who had either uncoated cardiopulmonary bypass circuits or heparin-bonded circuits. Subsequently, 23 additional patients were studied in a randomized fashion. Respiratory function and blood product utilization were recorded. RESULTS: In the pilot study, heparin-bonded circuit patients had less complement 3a (p < 0.001) and interleukin-8 (p < 0.05) compared with uncoated cardiopulmonary bypass circuit patients. The randomized study revealed that the heparin-bonded circuit was associated with reduced complement 3a (p = 0.02). Multiple variable analysis revealed that the following postoperative variables were increased with bypass time (p = 0.01) and diminished with heparin-bonded circuits: interleukins (p = 0.01), peak airway pressures (p = 0.05), and prothrombin time (p = 0.03). CONCLUSIONS: Heparin-bonded circuits significantly reduce cytokines and complement during cardiopulmonary bypass and lower interleukin levels postbypass; they were also associated with improved pulmonary and coagulation function. Heparin-bonded circuits ameliorate the systemic inflammatory response in pediatric patients from cardiopulmonary bypass.