Karl Woitas

Clinical Real-Time Monitoring of Gaseous Microemboli in Pediatric Cardiopulmonary Bypass

We describe the occurrence and distribution of gaseous microemboli with real-time monitoring in a pediatric cardiopulmonary bypass (CPB) circuit and in the cerebral circulation of patients using the Emboli Detection and Classification (EDAC) system and transcranial Doppler (TCD). Four patients (weights 3.2-13.8 kg) were studied. EDAC monitors were located on the venous line and on the postfilter arterial line to measure gaseous microemboli in the CPB circuit. TCD was used to measure high-intensity transient signals (HITS) in the middle cerebral artery. Before the initiation of CPB, EDAC detected gaseous microemboli in two cases when giving volume through the arterial line. At the initiation of CPB, gross air appeared in the venous line and gaseous microemboli were detected in the arterial line in all patients. EDAC detected a total of 3192-14 699 gaseous microemboli in the arterial line during the whole CPB period, more than 99% of which were smaller than 40 microns. After cessation of CPB, EDAC detected gaseous microemboli in the arterial line in all cases. The TCD detected HITS in two cases (25 and 315), and detected no HITS in two cases. We observed that the venous line acted as a principal source of gaseous microemboli, particularly when using vacuum-assisted venous drainage, and that a significant number of these gaseous microemboli smaller than 40 microns were subsequently transferred to the patient. Using EDAC and TCD together could strengthen the monitoring of gaseous microemboli in the extracorporeal circuit and cerebral circulation.

Successful treatment of peripartum cardiomyopathy with extracorporeal membrane oxygenation

A 24-year-old female developed heart failure within four months of delivering her first child. Echocardiogram revealed a moderately dilated left ventricle with severely reduced systolic function. She continued to decompensate, requiring intubation and inotropic support. When the use of an intra-aortic balloon pump failed to stabilize the patient, the decision was made to place her on ECMO. The circuit consisted of a Quadrox D membrane oxygenator and a CentriMag® centrifugal pump. After 11 days of support, the patient met the weaning criteria and was successfully removed from ECMO. She was discharged one month after her admission. The new technology available allows for ECMO to be considered as an earlier option for the treatment and management of these patients as a bridge to recovery.

Microemboli detection and classification during pediatric cardiopulmonary bypass.

Microemboli may be a cause of postoperative neurological morbidity. Improved detection of microemboli may lead to better strategies to minimize embolization and improve neurological outcomes. Transcranial Doppler may have limited sensitivity for very small microemboli. The Emboli Detection and Classification (EDAC) Quantifier offers increased sensitivity (10 μm) and potentially improved capability for microemboli monitoring. EDAC was used to measure microemboli in the cardiopulmonary bypass circuit during 33 pediatric heart operations. More microemboli were detected in the venous than the arterial line (median, 11,830 vs 1298). Venous microemboli tended to be larger in size than arterial microemboli (>40 μm; 59% vs 7%). Increased venous and arterial microemboli were seen at the onset of bypass; increased venous microemboli were also seen with clamp removal. Thousands of microemboli <40 μm are transmitted to pediatric patients during heart surgery. Initiation of bypass may be a key offender and may result from air in the venous line. Although the significance of microemboli remains unknown, increased awareness may lead to improved techniques to minimize microemboli, with improvement in neurological outcomes.

Translational Research in Pediatric Extracorporeal Life Support Systems and Cardiopulmonary Bypass Procedures: 2011 Update

Over the past 6 years at Penn State Hershey, we have established the pediatric cardiovascular research center with a multidisciplinary research team with the goal to improve the outcomes for children undergoing cardiac surgery with cardiopulmonary bypass (CPB) and extracorporeal life support (ECLS). Due to the variety of commercially available pediatric CPB and ECLS devices, both in vitro and in vivo translational research have been conducted to achieve the optimal choice for our patients. By now, every component being used in our clinical settings in Penn State Hershey has been selected based on the results of our translational research. The objective of this review is to summarize our translational research in Penn State Hershey Pediatric Cardiovascular Research Center and to share the latest results with all the interested centers.

Benefits of pulsatile flow in pediatric cardiopulmonary bypass procedures: from conception to conduction

This review on the benefits of pulsatile flow includes not only experimental and clinical data, but also attempts to further illuminate the major factors as to why this debate has continued during the past 55 years. Every single component of the cardiopulmonary bypass (CPB) circuitry is equally important for generating adequate quality of pulsatility, not only the pump. Therefore, translational research is a necessity to select the best components for the circuit. Generation of pulsatile flow depends on an energy gradient; precise quantification in terms of hemodynamic energy levels is, therefore, a necessity, not an option. Comparisons between perfusion modes should be done after these basic steps have been taken. We have also included experimental and clinical data for direct comparisons between the perfusion modes. In addition, we included several suggestions for future clinical trials for other interested investigators.

The new role of the perfusionist in adult extracorporeal life support

Adult and pediatric extracorporeal life support (ECLS) has been transformed by the European1 and Australian 2 experiences with a reduction of the circuit to its most basic form (Figure 1). Many factors have converged at this point in time to allow us to offer this support. The availability in the U.S.A. of an advanced oxygenator (QuadroxD) (Maquet Inc., Bridgewater, NJ), long-term centrifugal pumps and circuit coatings offers us the means to provide ECLS. The other equally important factor is the intensivist trained in extracorporeal therapies. Once the intensive care unit registered nurse (ICU RN) is trained to safely and effectively manage both the patient and ECLS circuit, this support may be offered. The perfusionist is in an unique position to educate and mentor the ICU RN in ECLS. There is, perhaps, no one in a better position to explain this equipment and its uses in an interdisciplinary-oriented pediatric and adult ECLS program than a perfusionist.

Evaluation of Hemodynamic Performance of a Combined ECLS and CRRT Circuit in Seven Positions With a Simulated Neonatal Patient

As it is common for patients treated with extracorporeal life support (ECLS) to subsequently require continuous renal replacement therapy (CRRT), and neonatal patients encounter limitations due to lack of access points, inclusion of CRRT in the ECLS circuit could provide advanced treatment for this population. The objective of this study was to evaluate an alternative neonatal ECLS circuit containing either a Maquet RotaFlow centrifugal pump or Maquet HL20 roller pump with one of seven configurations of CRRT using the Prismaflex 2000 System. All ECLS circuit setups included a Quadrox-iD Pediatric diffusion membrane oxygenator, a Better Bladder, an 8-Fr arterial cannula, a 10-Fr venous cannula, and 6 feet of ¼-inch diameter arterial and venous tubing. The circuit was primed with lactated Ringers solution and packed human red blood cells resulting in a total priming volume of 700 mL for both the circuit and the 3-kg pseudopatient. Hemodynamic data were recorded for ECLS flow rates of 200, 400, and 600 mL/min and a CRRT flow rate of 50 mL/min. When a centrifugal pump is used, the hemodynamic performance of any combined ECLS and CRRT circuit was not significantly different than that of the circuit without CRRT, thus any configuration could potentially be used. However, introduction of CRRT to a circuit containing a roller pump does affect performance properties for some CRRT positions. The circuits with CRRT positions B and G demonstrated decreased total hemodynamic energy (THE) levels at the post-arterial cannula site, while positions D and E demonstrated increased post-arterial cannula THE levels compared to the circuit without CRRT. CRRT positions A, C, and F did not have significant changes with respect to pre-arterial cannula flow and THE levels, compared to the circuit without CRRT. Considering hemodynamic performance, for neonatal combined extracorporeal membrane oxygenation (ECMO) and CRRT circuits with both blood pumps, we recommend the use of CRRT position A due to its hemodynamic similarities to the ECMO circuit without CRRT.

Impact of Translational Research on Optimization of Neonatal Cardiopulmonary Bypass Circuits and Techniques-The Penn State Health Approach.

Translational research is a “bench-to-bedside and beyond” approach which transforms scientific discoveries during engineering and basic science research in the laboratory and preclinical studies into clinical applications to improve the quality of healthcare. The goal of translational research is to provide scientific evidence for decision-making on actions to improve health. The experimental design, conduct, analysis, and conclusion of the study must strictly follow the scientific method. More importantly, experiments must have the ability to be duplicated. Additionally, translational research must be conducted at independent institutions without financial incentive or other personal benefit from the projects. Therefore, regarding the selection of components of cardiopulmonary bypass (CPB) circuitry, translational research is mandatory, not optional, both for the safety of neonatal and pediatric cardiac patients undergoing CPB procedures as well as for saving the institutional resources. Over the past 13 years at Penn State Health Children’s Hospital and College of Medicine, our multi-disciplinary research team has established the Pediatric Cardiovascular Research Center with the goal of improving the outcomes for children undergoing cardiac surgery with CPB procedures. Currently, every CPB component used in our clinical setting at Penn State Health has been selected based on the results of our translational research projects. This editorial will summarize these translational research projects for neonatal CPB patients in the Penn State Health Pediatric Cardiovascular Research Center and will share the latest results with all interested readers.

Building a Better Neonatal Extracorporeal Life Support Circuit: Comparison of Hemodynamic Performance and Gaseous Microemboli Handling in Different Pump and Oxygenator Technologies: THOUGHTS AND PROGRESS

Neurologic complications during neonatal extracorporeal life support (ECLS) are associated with significant morbidity and mortality. Gaseous microemboli (GME) in the ECLS circuit may be a possible cause. Advances in neonatal circuitry may improve hemodynamic performance and GME handling leading to reduction in patient complications. This study compared hemodynamic performance and GME handling using two centrifugal pumps (Maquet RotaFlow and Medos Deltastream DP3) and polymethylpentene oxygenators (Maquet Quadrox-iD and Medos Hilite 800LT) in a neonatal ECLS circuit model. The experimental circuit was primed with Lactated Ringers solution and packed human red blood cells (hematocrit 40%) and arranged in parallel with the RotaFlow and DP3 pump, Quadrox-iD and Hilite oxygenator, and Better-Bladder. Hemodynamic trials evaluating pressure drops and total hemodynamic energy (THE) were conducted at 300 and 500 mL/min at 36°C. GME handling was measured after 0.5 mL of air was injected into the venous line using the Emboli Detection and Classification Quantifier System with unique pump, oxygenator, and Better-Bladder combinations. The RotaFlow pump and Quadrox oxygenator arrangement had lower pressure drops and THE loss at both flow rates compared to the DP3 pump and Hilite oxygenator (P < 0.01). Total GME volume and counts decreased with Better-Bladder at both flow rates with all combinations (P < 0.01). Hemodynamic performance and energy loss were similar in all of the circuit combinations. The Better-Bladder significantly decreased GME. All four combinations of pumps and oxygenators also performed similarly in terms of GME handling.

Does an Open Recirculation Line Affect the Flow Rate and Pressure in a Neonatal Extracorporeal Life Support Circuit With a Centrifugal or Roller Pump

The objective of this study is to evaluate the impact of an open or closed recirculation line on flow rate, circuit pressure, and hemodynamic energy transmission in simulated neonatal extracorporeal life support (ECLS) systems. The two neonatal ECLS circuits consisted of a Maquet HL20 roller pump (RP group) or a RotaFlow centrifugal pump (CP group), Quadrox-iD Pediatric oxygenator, and Biomedicus arterial and venous cannulae (8 Fr and 10 Fr) primed with lactated Ringers solution and packed red blood cells (hematocrit 35%). Trials were conducted at flow rates ranging from 200 to 600 mL/min (200 mL/min increments) with a closed or open recirculation line at 36°C. Real-time pressure and flow data were recorded using a custom-based data acquisition system. In the RP group, the preoxygenator flow did not change when the recirculation line was open while the prearterial cannula flow decreased by 15.7-20.0% (P < 0.01). Circuit pressure, total circuit pressure drop, and hemodynamic energy delivered to patients also decreased (P < 0.01). In the CP group, the prearterial cannula flow did not change while preoxygenator flow increased by 13.6-18.8% (P < 0.01). Circuit pressure drop and hemodynamic energy transmission remained the same. The results showed that the shunt of an open recirculation line could decrease perfusion flow in patients in the ECLS circuit using a roller pump, but did not change perfusion flow in the circuit using a centrifugal pump. An additional flow sensor is needed to monitor perfusion flow in patients if any shunts exist in the ECLS circuit.