Simultaneous Control of Venous Reservoir Level and Arterial Flow Rate in Cardiopulmonary Bypass With a Centrifugal Pump.

Cardiopulmonary bypass (CPB) is an indispensable technique in cardiac surgery, providing the ability to temporarily replace cardiopulmonary function and create a bloodless surgical field. Traditionally, the operation of CPB systems has depended on the expertise and experience of skilled perfusionists. In particular, simultaneously controlling the arterial and venous occluders is difficult because the blood flow rate and reservoir level both change, and failure may put the patient's life at risk. This study proposes an automatic control system with a two-degree-of-freedom model matching controller nested in an I-PD feedback controller to simultaneously regulate the blood flow rate and reservoir level. CPB operations were performed using glycerin and bovine blood as perfusate to simulate flow-up and flow-down phases. The results confirmed that the arterial blood flow rate followed the manually adjusted target venous blood flow rate, with an error of less than 5.32%, and the reservoir level was maintained, with an error of less than 3.44% from the target reservoir level. Then, we assessed the robustness of the control system against disturbances caused by venting/suction of blood. The resulting flow rate error was 5.95%, and the reservoir level error 2.02%. The accuracy of the proposed system is clinically satisfactory and within the allowable error range of 10% or less, meeting the standards set for perfusionists. Moreover, because of the system's simple configuration, consisting of a camera and notebook PC, the system can easily be integrated with general CPB equipment. This practical design enables seamless adoption in clinical settings. With these advancements, the proposed system represents a significant step towards the automation of CPB.

Modifying priming techniques in cardiopulmonary bypass circuit in known case of sickle-cell trait undergoing open heart surgery.

Modifying cardiopulmonary bypass (CPB) circuit's priming technique before the onset of CPB in cardiac patients known with sickle-cell disease or sickle cell trait has been observed to be of substantial significance in dealing with such challenges without having any life-threatening consequences. We modified our routine heparinized crystalloid priming of the CPB circuit with partial exchange transfusion by adding donor blood (packed red blood cells), fresh frozen plasma (FFP), and bicarbonate. This has helped us bring down the overall sickle cell hemoglobin in the blood thereby reducing its risk of sickling.

A New Evaluation Q-Factor to Be Calculated for Suction Geometries as a Basis for Smooth Suction in the Operating Field to Ensure the Highest Possible Blood Integrity for Retransfusion Systems.

Blood hemolysis caused by mechanical impact is a serious problem in medicine. In addition to the heart-lung machine (artificial surfaces, flow irritating connection points) which contributes to hemolysis, blood suction and surgical suction devices are influencing factors. Goal of our research is to develop best flow optimizing suction geometry that represents the best compromise between all influencing effects. Based on data that negative pressure and turbulence have a negative impact on blood components, 27 surgical suction tips have been examined for acoustic stress and negative pressure behavior. Furthermore, a dimensionless factor Q was introduced to assess the overall performance of the suction tips investigated.

Overcoming perioperative inflammation as a hurdle for successful preclinical orthotopic cardiac xenogeneic transplantations - particular in regard of the mandatory use of heart-lung machines.

INTRODUCTION: After orthotopic cardiac xenotransplantation, the combination of both the inflammatory responses to the exposure of a recipient to the xenogeneic organ and the use of cardiopulmonary bypass has been assumed to cause detrimental side effects. These have been described not only to affect the transplanted organ (heart) itself, but also the recipient's lungs. In this article, we summarize how these possible detrimental processes can be minimized or even avoided. METHODS: Data from eight pig-to-baboon orthotopic cardiac xenotransplantation experiments were analyzed with a special focus on early (within the first week) postoperative organ dysfunction and systemic inflammatory responses. Non-ischemic heart preservation and the careful management of the heart-lung machine were deemed essential to guarantee not only the immediate function of the transplanted xenogeneic organ but also the prompt recovery of the recipient. RESULTS: After weaning from cardiopulmonary bypass, very low catecholamine amounts were needed to ensure an adequate pump function and cardiac output. Central venous oxygen saturation and serum lactate levels remained within normal ranges. All animals were successfully weaned from ventilation within the first postoperative hours. Serum parameters of the transplants and native kidneys and livers were initially slightly elevated or always normal, as were hemoglobin, LDH, and platelet measurements. Markers of systemic inflammation, C-reactive protein, and IL-6 were slightly elevated, but the reactions caused no lasting damage. CONCLUSION: Consistent short-term and long-term results were achieved after orthotopic cardiac pig-to-baboon transplantation without detrimental inflammatory responses or signs of multiorgan failure. In comparison to allogeneic procedures, non-ischemic heart preservation was important for successful immediate organ function, as was the management of the heart-lung machine. Thus, we believe that genetically modified porcine hearts are ready for use in the clinical setting.

Origins and Evolution of Extracorporeal Circulation: JACC Historical Breakthroughs in Perspective.

Midway through the 20th century, direct open-heart operations were not yet a reality, awaiting safe methods to support the cardiopulmonary circulation during cardiac surgery. The scientific advancements collectively leading to safe cardiopulmonary bypass are considered some of the most impactful advances of modern medicine. Stimulated by the work of physiologists and engineers in the late 19th century, primitive pump and oxygenator designs were the forerunners of major work by DeBakey and others in roller pump design and by Gibbon in oxygenator development. Following Gibbon's historic successful closure of an atrial septal defect in 1953 with his heart-lung machine, it was left to Lillehei and Kirklin to first successfully repair large series of cardiac malformations. The history leading to these historic events and the subsequent evolution of cardiopulmonary bypass machines for short- and longer-term support is filled with engineering and surgical brilliance, daring innovations, and serendipity.

The Design and Implementation of a Convertible Extracorporeal Circuit for Lung Transplantation.

Intraoperative management for patients during orthotopic lung transplantation may be performed without mechanical circulatory support, with veno-arterial extracorporeal membrane oxygenation (VA-ECMO), or cardiopulmonary bypass (CPB). For certain patients, an intraoperative conversion from VA-ECMO to CPB may be indicated. If a VA-ECMO patient requires CPB conversion, the previous model at our institution used two separate machines and was overall inefficient. The primary aim of this project was to develop a CPB pack modification to create a circuit that easily converts from VA-ECMO to CPB if indicated. The secondary aim was to create new supportive protocols and a comprehensive education and training curriculum for our large perfusion department to enhance patient safety. The new circuit was carefully designed and evaluated to minimize changes to the current CPB circuit while allowing for the safest configuration of VA-ECMO. A new protocol was designed with multi-disciplinary collaboration. A comprehensive education and training curriculum, as well as an objective competency assessment tool, were created. The circuit was subjectively evaluated by perfusionists and outscored our previous model in the areas of ease of setup, use, and CPB conversion. It received positive feedback from cardiothoracic surgeons and anesthesiologists as well. Lastly, it provided a financial benefit to our institution.

Sequestration of Dexmedetomidine in Ex Vivo Cardiopulmonary Bypass Circuits.

Dexmedetomidine (DEX) is a sedative used in combination with other drugs in neonates and infants undergoing cardiac surgery using cardiopulmonary bypass (CPB). This study aimed to evaluate the disposition of DEX after administration to the ex vivo CPB circuits following different bolus doses and continuous infusion of DEX, including the effect of circuit coating, temperature, and modified ultrafiltration (MUF). Cardiopulmonary bypass circuits were setup ex vivo and primed with reconstituted blood. Dexmedetomidine was administered to the circuit (as a single bolus or single bolus along with continuous infusion). The circuit was allowed to equilibrate during the first 5 minutes, blood samples were collected at multiple time points (5-240 minutes). Blood samples were processed to collect plasma and analyzed for DEX with a validated assay. The majority of DEX sequestration in ex vivo CPB circuits occurred within the first 15 minutes. The percent of DEX remained in plasma pre-MUF (16-71%) and post-MUF (22-92%) varied depending on the dose and dosing scheme. Modified ultrafiltration significantly increased the plasma concentration of DEX in 19 of 23 circuits by an average of 12.1 ± 4.25% (p < 0.05). The percent sequestration of DEX was lower in CPB circuits at lower DEX doses compared to higher doses. A combination of DEX initial loading dose and continuous infusion resulted in steady concentrations of DEX over 4 hours. At therapeutically relevant concentrations of DEX (485-1,013 pg/ml), lower sequestration was observed in ex vivo CPB circuits compared to higher doses. The sequestration of DEX to circuits should be considered to achieve the optimal concentration of DEX during CPB surgery.

Fraction of expired oxygen: an additional safety approach to monitor oxygen delivery to the heart lung machine oxygenator.

BACKGROUND: Monitoring oxygen delivery to the oxygenator of a heart lung machine (HLM) is typically accomplished with an O2 analyzer connected to the gas inflow line. It is assumed when the FiO2 is greater than 21% that oxygen is being delivered to the oxygenator. However, this assumption is imperfect because the connection of the inflow line to the oxygenator is downstream from the O2 analyzer. FiO2 monitoring will not alert the perfusionist if the inflow line is not actually connected to the oxygenator. Measuring the fraction of expired oxygen (FEO2) is a more reliable way of monitoring O2 delivery. METHODS: An O2 analyzer was placed on the scavenging line that is attached to the exhaust port of oxygenator (FEO2). RESULTS: Whenever the FiO2 is greater than 21%, and the inflow line is properly connected, the FEO2 exiting the oxygenator is greater than 21%. The FEO2 falls to 21% when the inflow line is not functioning. CONCLUSION: Monitoring the FEO2 is a more reliable way to verify O2 delivery to an oxygenator. An alarm can be set on the FEO2 monitor to alert the perfusionist if the FEO2 falls below a predetermined threshold so any issue with O2 delivery will always be recognized.

A Novel Method to Safely De-Air a HeartWare System in a Single-Ventricle Patient by Utilizing ECMO and a Minimized CPB Circuit.

The survival of congenital heart disease (CHD) patients with single-ventricle (SV) physiology has markedly increased as a result of advances in operative techniques and postsurgical management. Nonetheless, these patients remain highly susceptible to end-stage heart failure requiring cardiac replacement therapies at early ages. Given a worldwide shortage of transplantable organs, mechanical circulatory support (MCS) represents an alternative treatment option. The significant heterogeneity of the SV population presents unique indications for MCS that have begun to be evaluated. This case study describes a 12-year-old female with heterotaxy syndrome and an SV condition, previously palliated with a Fontan operation at another institution. The patient was placed on veno-arterial (VA) extracorporeal membrane oxygenation (ECMO) during prolonged cardiopulmonary resuscitation, and later underwent HeartWare ventricular assist device (HVAD) implantation as a bridge to transplantation (BTT). A novel method was chosen to optimize careful de-airing of the heart through a minimized cardiopulmonary bypass (CPB) setup, during full ECMO support and surgical insertion of the HeartWare. The ascending aorta was vented proximal to the HVAD outflow graft anastomosis through a minimized CPB circuit at <10% of the ECMO flow rate. This circuit adaption allowed for euvolemic resuscitation via connection from the minimized CPB circuit to the venous limb of the ECMO circuit. The transition from VA-ECMO to the HeartWare was well tolerated despite a challenging sternotomy and cardiac anomaly. A minimized bypass circuit proved efficacious for the benefit of volume resuscitation and safe de-airing of the HVAD while on ECMO support. The literature is limited concerning safe practices for implantation of durable VADs in complex SV patients coupled with those transitioning from varying modalities of MCS. As SV survivability regresses to heart failure, it is essential that we share techniques that aim to improve the long-term outcomes for successful BTT or bridge to decision (BTD).

Weaning from cardiopulmonary bypass, decannulation, and closure.

In 1952, John Gibbon performed the first successful cardiac procedure using cardiopulmonary bypass, which turned out to be one of the most important clinical advances of that year. Cardiopulmonary bypass has also been described as "One of the most impressive evidences of the role of investigative surgery in the history of medicine in the persevering efforts of Dr. Gibbon for more than 20 years, which finally culminated in a practical heart-lung machine," at the first John H. Gibbon, Jr, Lecture at the annual meeting of the American College of Surgeons [1]. Due to the subsequent advancement of cardiopulmonary bypass, many patients with complex heart disease requiring surgical care undergo cardiac surgery while the other organs remain adequately oxygenated and perfused.

Synthetic Material Abdominal Swabs Reduce Activation of Platelets and Leukocytes Compared to Cotton Materials.

During surgical procedures, cotton abdominal swabs with their high absorptive capacity and malleability are used to retain organs and absorb blood or other body fluids. Such properties of the natural material cotton are advantageous for most operations, but in cardiopulmonary bypass (CPB) surgery, a high blood volume can accumulate in the thoracic cavity that is quickly retransfused via the heart-lung machine (HLM). This common practice is supposed to be safe due to the high anticoagulation. However, in vitro analyses showed that blood cells and plasma proteins were activated despite a high anticoagulation, which can propagate especially an inflammatory response in the patient. Thus, we investigated patients' blood during CPB surgery for inflammatory and coagulation-associated activation after contact to the HLM and either cotton or synthetic abdominal swabs. Contact with cotton significantly increased thrombocyte and neutrophil activation measured as ß-thromboglobulin and PMN-elastase secretion, respectively, compared to synthetic abdominal swabs. Both inflammatory cytokines, interleukin (IL) 1ß and IL6, were also significantly increased in the cotton over the synthetic patient group, while SDF-1α was significantly lower in the synthetic group. Our data show for the first time that cotton materials can activate platelets and leukocytes despite a high anticoagulation and that this activation is lower with synthetic materials. This additional activation due to the material on top of the activation exerted by the tissue contact that blood is exposed to during CPB surgery can propagate further reactions in patients after surgery, which poses a risk for this already vulnerable patient group.

Neonatal Cardiopulmonary Bypass Circuit Blood Prime Quality Analysis.

Blood-primed cardiopulmonary bypass circuits are frequently necessary to achieve safe support during pediatric open-heart surgery. Literature is lacking regarding suitable prime constituents or methods for achieving a physiologically appropriate blood-primed circuit. We examined the chemistry and hematology of neonatal blood-primed circuits from the conclusion of the priming procedure until the initiation of bypass. Base deficit/excess, pH, pO2, pCO2, HCO3, glucose, sodium, potassium, calcium, hematocrit, lactate, and osmolality were analyzed. Any deviation over time from the original prime value was compared for significance. Statistically significant changes were found between T0 and all time points for all parameters, except for pH and pO2 out to 1 hour. Among all parameters, various rates of change were observed. Although most changes in the parameters were found to be statistically significant, those changes may not be clinically significant based on clinician interpretation. Attention to the prime quality beyond the immediate post-priming period may be beneficial. Should the time period between validation of the prime quality and initiation of bypass be extended, it may be advisable to reevaluate the prime quality.

Bernard J. Miller: MD, ScD. (Hon), FACS: Lifelong Surgeon-Scientist and Critical Contributor to the Gibbon Heart-Lung Machine.

Bernard J. Miller, MD, ScD. (Hon), FACS, is known as a critical contributor for his work in the John H. Gibbon, MD, laboratory for his work on the heart-lung machine (HLM). In this setting, Dr. Miller developed the fluid control servo system, which was necessary to prevent malfunctioning of the HLM and prevent air emboli. Additionally, Dr. Miller assisted in conceiving and testing the left ventricular vent, the positive-negative pressure ventilator, and the HLM oxygenator; these inventions were all the product of extensive collaboration between the International Business Machines Corporation and the members of Dr. Gibbon's laboratory. Furthermore, Dr. Miller was a surgical assistant and perfusionist in the first successful open-heart surgery. Herein, we seek to describe Dr. Miller's story and his contributions to the HLM, as well as the contributions that were developed by the laboratory at that time. Additionally, we describe critical events leading up to the first successful use of the HLM on May 6, 1953, including a previously unreported use of the HLM for partial bypass of the right heart at Pennsylvania Hospital in 1952. Finally, we present the rest of Dr. Miller's professional and personal successes after his work on the HLM ended.

Development of a real-time blood damage monitoring device for cardiopulmonary bypass system using near-infrared spectroscopy.

The optical properties of hemoglobin could indicate the degree of hemolysis. We aimed to utilize this to develop a real-time blood damage monitoring device for cardiopulmonary bypass (CPB) systems. The real-time blood damage monitoring device comprised a near-infrared spectroscopy optical module with a fiber spectrometer and monitoring platform and computer software developed using LabVIEW 2017. The fiber spectrometer operated at wavelengths of 545, 660, and 940 nm and contained a detector fiber bundle (source-detector distance = 1.0-2.5 cm). CPB operation was simulated using an artificial heart-lung machine with a flow rate of 3, 4, or 5 L/min. Four hundred milliliter of anticoagulated porcine blood was continuously rotated for 4 h. The transmittance, reflectivity, and absorbance of the blood were measured using the optical device at a frequency of 25 Hz and then digitally averaged into 1-s interval. Samples of damaged blood were collected at regular intervals for in vitro hemolysis tests to calculate the normalized index of hemolysis (NIH). All experiments were repeated three times. We prepared 28 blood bags containing 400 ml of anticoagulant. Paired t test was used to examine the test-retest reliability of the differences between the three methods and control samples. Statistical tests revealed significant differences in the mean values between the test and control groups over time (P < 0.01). Relationship was established between the real-time monitoring results and the NIH values. An effective blood damage detection method that combined in vitro hemolysis tests and near-infrared spectroscopy was achieved. The results demonstrate the clinical potential of a real-time, low-cost, and reliable blood damage monitoring device to improve the safety of CPB operation.

First in vivo assessment of RAS-Q technology as lung support device for pulmonary hypertension.

OBJECTIVES: To assess the in vivo hemodynamic effects on the pressure overloaded right ventricle of RAS-Q® technology, the world's first gas exchanger with a fully integrated compliance. METHODS: In six acute in vivo trials RAS-Q was implanted in sheep between the pulmonary artery and left atrium. Right ventricular pressure overload was induced by pulmonary artery banding. Pressures and flows were recorded in baseline, moderate and severe pulmonary hypertension conditions. In one trial, RAS-Q was benchmarked against the pediatric Quadrox-i®. RESULTS: With 1.00 and 1.17 L/min, RAS-Q delivered 31% and 39% of the total cardiac output in moderate and severe pulmonary hypertension, respectively. Pulmonary artery pressures and mean pulmonary artery pressure/mean arterial blood pressure ratio successfully decreased, implying a successful right ventricular unloading. Cardiac output was restored to normal levels in both pulmonary hypertension conditions. With both devices in parallel, RAS-Q provided three times higher flow rates and a 10 times higher pressure relief, compared to the pediatric Quadrox-i. CONCLUSION: A gas exchanger with a fully integrated compliance better unloads the right ventricle compared to a non-compliant gas exchanger and it can restore cardiac output to normal levels in cases of severe pulmonary hypertension.

Modified cardiopulmonary bypass circuit for the use of the AngioVac® system in a case with high paradoxical embolization risk.

The AngioVac® is a vacuum-assisted percutaneous thrombectomy suction system. In critically ill patients, the sudden volume shift can result in abrupt hemodynamic changes thus leading to a cardiac right-left shunt with a high risk of paradoxical embolization. We describe a modified cardiopulmonary bypass circuit for the use of the AngioVac® system that enables full cardiopulmonary support and reduces paradoxical thromboembolic risk.