Bypass Device Research Articles

Management of mini-cardiopulmonary bypass devices: is it worth the energy?

To address the role of mini-cardiopulmonary bypass systems in cardiac operations, with specific respect to clinical outcome. Mini-cardiopulmonary bypass systems are not accompanied by major complications, even if some safety concerns have been raised. Randomized controlled trials and large retrospective trials suggest that they can induce a beneficial effect in terms of morbidity reduction, shortening of mechanical ventilation time, ICU, and hospital stay, whereas mortality seems not to be affected. Studies failing to demonstrate significant differences were generally underpowered. A meta-analysis focused on allogeneic blood products transfusion rate demonstrates that mini-cardiopulmonary bypass systems reduce the transfusion rate (odds ratio 0.4, 95% confidence interval 0.26-0.63, P < 0.001). This may be because of containment in hemodilution during cardiopulmonary bypass. The better outcome may be related to both this mechanism and the consequent reduction in transfusional needs. Mini-cardiopulmonary bypass systems reduce the need for allogeneic blood transfusions. Other improvements in postoperative outcome are more debated. They require a long learning curve and are more expensive. A cost analysis based on a large randomized controlled trial is still needed to clarify the potential future role of these systems in clinical practice.

Implantable endoscopic gastric bypass – device and experimental procedure

Malabsorptive bariatric surgery is an effective treatment option for morbid obesity, but may be associated with complications and side effects. We have developed a new experimental approach to creating a gastric bypass through an intraluminal access. The goal is to reduce postoperative complications and to reduce mid-term side-effects of malabsorptive bypass food passage and to allow easy reversion of the procedure. The new procedure is based on an implantable gastric bypass device, installed by combined transoral flexible and minimally invasive abdominal access. The newly developed device and procedure were studied in a pilot experimental trial in the porcine animal model (n=8). Endpoints were the feasibility of the technical procedure, the ability of the animal to eat and digest food, the implant functionality over the survival period and the absence of major complications over a short-term follow-up (one week). The procedure was technically successful in all eight animals. Animals were able to take in food and water till sacrifice. Four animals had major complications (one abdominal wall dehiscence, one invagination ileus of the small bowel, one dehiscence of the gastro-jejunal anastomosis and one myocardial infarction) and did not complete follow-up. In two cases migration of the device into the stomach was observed. The difference between our experimental technique and the gold standard surgical methods for gastric bypass consists of the endoluminal approach by implanting an intraluminal gastric bypass device. This concept avoids gastric transsection and an additional anastomosis and enables an adjustable food passage between the bypass and the natural duodenal passage. Further long-term follow-up studies are required.

Complicações após cirurgia de revascularização miocárdica em pacientes idosos

Due to the increasing longevity of the and high prevalence of coronary heart disease in the aged , coronary artery bypass graft surgery has become frequent in older patients. The purpose of this study is to describe operative features, length of stay, complications and short term outcomes after coronary artery bypass graft in such patients. From February 2005 to October 2007, 269 patients underwent coronary artery bypass graft. Demographic data, comorbidities, prognostic scores, coronary artery bypass graft elective versus urgent indication, intensive care unit length of stay, postoperative complications and intensive care unit mortality were recorded. Intra-operative characteristics, such as total surgery time, use of bypass device, on-pump time, urine output, fluid balance, use of blood products and number of grafts, were analyzed. Patients were divided in four age groups: group I (< 60 n = 68), II (60 to 69 n = 86), III (70 to 79 n = 93) IV and older than 80 years (n = 22). Group IV patients were more frequently submitted to coronary artery bypass graft combined with valve replacement, emergency surgery, and had longer stay in the intensive care unit (p < 0.01). The incidence of at least one postoperative complication was also higher among patients older than 80 (p < 0.001). Multivariate analysis identified age and on-pump time as independent risk factors for development of complications. Mortality increased in patients older than 70 years (p = 0.03). Octogenarian patients undergoing coronary artery bypass graft have longer intensive care unit length of stay, incidence of complications and mortality. Age and on-pump time were independent risk factors associated with the incidence of postoperative complications.

COMPLEMENT ACTIVATION AND BIOINCOMPATIBIUTY

The degree of biocompatibility of biomaterials can be evaluated using various assay systems detecting activation of the blood cascade systems, leukocytes or platelets. Activation of complement is one mechanism associated with adverse effects observed when bioincompatible materials are used. We present data showing that the terminal complement complex, an indicator of terminal pathway activation, is suitable for evaluation of biocompatibility of biomaterials such as cardiopulmonary bypass devices. Furthermore, our results suggest that bioincompatibility is improved when artificial surfaces are modified with end point attached functionally active heparin.

Successful resuscitation of an elderly man with deep accidental hypothermia using portable extracorporeal circulation in the emergency department: a case report

IntroductionDeep accidental hypothermia (body temperature below 28°C) is rare and has a high mortality rate. Successful resuscitation usually occurs in the young, but a prompt intervention using a portable extracorporeal cardiopulmonary circulation device can also provide a good outcome for older persons.Case presentationWe report the successful resuscitation of an 82-year-old male from deep accidental hypothermia using portable extracorporeal circulation in the emergency department.ConclusionThis successful resuscitation of an 82-year-old patient demonstrates that a prompt intervention by a medical team that trains together, using a mobile cardiopulmonary bypass device via a percutaneous approach, can potentially provide good outcomes for all victims of deep accidental hypothermia, both in the operating suites and the emergency department.

Automated control of the velocity of in-tube diagnostic tools for main gas pipelines: II. Electronic equipment of a bypass device

The design and operation of electronic in-tube nondestructive-testing equipment containing a bypass device are described. The electronic equipment designed for the bypass device is built in the general system of onboard electronic equipment and performs automatic control of the preset velocity of a flaw detector or other diagnostic pigs moving through a pipeline.

Automated control of the velocity of in-tube diagnostic tools for main gas pipelines: I. Development, design, and operating principle of a bypass device

The study considers the development, design, and operating principle of a bypass device integrated into existing in-tube diagnostic tools. The bypass device is designed for automated control of the velocity of in-tube pig flaw detectors in main gas pipelines. Equipment of in-tube diagnostic tools with an automated-control system for the velocity provides performance of in-tube inspection without decreasing gas transportation. This facilitates the flaw detection of main pipelines substantially and makes a dispatcher of a gas-compressor station free of controlling the velocity of passage of in-tube diagnostic tools. The results of assembling a bypass device used for automated control of the velocity of in-tube diagnostic tools for main gas pipelines are considered. Arrangement of the bypass device in existing diagnostic tools for nondestructive testing is based on the experience of development, design, and exploitation of pig flaw detectors, which make it possible to locate the elements of the bypass device without any substantial restructuring of the pig flaw detectors.

Near-fatal betaxolol self-poisoning treated with percutaneous extracorporeal life support

We present a case of successful treatment of near-fatal beta-blocker self-poisoning but requiring extracorporeal circulatory support with severe complications. A 38-year-old woman ingested a mixture of tablets including betaxolol (5.32 g). Despite intensive treatment with fluid, dobutamine, isoprenaline, epinephrine, nor-epinephrine and glucagon, sustained cardiogenic shock occurred with almost complete hypokinesia of the left ventricular 14 h later. Therefore, a cardiac support was performed with a percutaneous cardiopulmonary bypass device at bedside. We review the literature with emphasis on both the best time to start this technique and its complications.

In Vitro Evaluation of Flow Divertors in an Elastase-Induced Saccular Aneurysm Model in Rabbit

Endovascular coiling is an acceptable treatment of intracranial aneurysms, yet long term follow-ups suggest that endovascular coiling fails to achieve complete aneurysm occlusions particularly in wide-neck and giant aneurysms. Placing of a stentlike device across the aneurysm neck may be sufficient to occlude the aneurysm by promoting intra-aneurysmal thrombosis; however, conclusive evidence of its efficacy is still lacking. In this study, we investigate in vitro the efficacy of custom designed flow divertors that will be subsequently implanted in a large cohort of animals. The aim of this study is to provide a detailed database against which in vivo results can be analyzed. Six custom designed flow divertors were fabricated and tested in vitro. The design matrix included three different porosities (75%, 70%, and 65%). For each porosity, there were two divertors with one having a nominal pore density double than that of the other. To quantify efficacy, the divertors were implanted in a compliant elastomeric model of an elastase-induced aneurysm model in rabbit and intra-aneurysmal flow changes were evaluated by particle image velocimetry (PIV). PIV results indicate a marked reduction in intra-aneurysmal flow activity after divertor implantation in the innominate artery across the aneurysm neck. The mean hydrodynamic circulation after divertor implantation was reduced to 14% or less of the mean circulation in the control and the mean intra-aneurysmal kinetic energy was reduced to 29% or less of its value in the control. The intra-aneurysmal wall shear rate in this model is low and implantation of the flow divertor did not change the wall shear rate magnitude appreciably. This in vitro experiment evaluates the characteristics of local flow phenomena such as hydrodynamic circulation, kinetic energy, wall shear rate, perforator flow, and changes of these parameters as a result of implantation of stentlike flow divertors in an elastomeric replica of elastase-induced saccular aneurysm model in rabbit. These initial findings offer a database for evaluation of in vivo implantations of such devices in the animal model and help in further development of cerebral aneurysm bypass devices.

A Small Scale Oxygenator for Cardiopulmonary Bypass in Rats

Cardiopulmonary bypass (CPB) devices replace transiently the function of both heart and lungs, allowing the investigator to work safely on a stopped heart. Although this technology has greatly improved since its first applications in the early 1950's there is still no definitive rat CPB model, various experiments reporting drawbacks like pulmonary edema, large priming volumes,etc. We present a new oxygenator that can be used in cardiopulmonary bypass experiments in rats, simple in design and efficient in function,in which the process of blood oxygenation takes place in a vertical cylinder filled up with air or oxygen, with blood being spread onto the wall and then trickling down in a thin layer that facilitates the oxygen transfer. The oxygenation is efficient, the pO2 reaches levels of almost 150 mmHg (physiological level is around 100 mmHg) in conditions of oxygen saturation of over 99% (normal levels 95%-98%).

Pediatric Cardiopulmonary Bypass Devices: Trends in Device Use for Cardiopulmonary Bypass and Postcardiotomy Support

Cardiopulmonary bypass (CPB) devices and techniques have continuously evolved. We have conducted surveys that chronicle the changes in CPB devices and techniques used at North American pediatric cardiac surgery centers since 1989. The aim of this article is to describe trends in cardiopulmonary bypass device use during cardiac surgery and changes in the devices used for extracorporeal life support (ECLS) following cardiac surgery for pediatric patients. The diffusion of innovation in pediatric cardiovascular surgery has not been solely driven by the availability of scientific evidence to support change but rather it has often been related to other factors that influence clinicians willingness to change including; tradition, ease of use, and cost related pressures. The current CPB systems used for cardiac surgery are more homogenous than in previous years. Most centers use a heparin coated or modified surface system comprised of a "hard shell" open venous reservoir, a roller pump, a hollow fiber membrane oxygenator, and arterial line filter. ECLS systems comprised of hollow fiber oxygenators and centrifugal pumps for are gradually replacing the classical ECLS circuit, servo regulated roller pumps and silicone rubber membranes. Nearly 40% of centers use these alternate components in their ECLS systems. Costs, utility, safety and measurable benefit to the patient should guide decisions related to device selection.

Less-Invasive Surgical Extraction of Problematic or Infected Permanent Transvenous Pacemaker System

The best management of problematic or infected transvenous permanent pacemaker system is complete surgical or percutaneous intravascular extraction of the pacemaker leads and removal of the generator. We present our experiences in 13 such patients in whom the leads were removed with the less-invasive technique. From 1996 to 2003, 13 patients, from 31 to 83 years of age (mean, 66.9 +/- 14.0 years), with problematic or infected transvenous permanent pacemaker systems were referred to our department for surgical treatment. In 6 patients, the original pacemakers were dual-chamber. A subxiphoid pericardiotomy was used as the monitoring port during the ventricular lead extraction. In addition, a right parasternal pericardiotomy through the third intercostal space was used as the monitoring port during the atrial lead extraction. Pacemaker systems were completely removed in all patients. Three bleeding episodes (23%), including two right atrial tears and one right ventricular rupture, were successfully circumvented through these monitoring ports. Concomitantly, a new epicardial single-chamber device was implanted through the subxiphoid pericardiotomy whenever indicated in 9 patients. All patients recovered and were discharged uneventfully. At a mean follow-up of 24.8 months (range, 1 to 90 months), no recurrent infections were observed. A less-invasive technique for explantation of the complete pacemaker system is feasible. This is a reliable method to eradicate infection. Neither cardiopulmonary bypass nor specific intravascular lead extraction devices, such as locking stylets or laser-assisted sheath, are needed.

By-pass Devices as Effective Means of Protection from the Hydraulic Hammer

Switching-off the parallel working pump units causes sudden discharge changes in parallel pipe lines, as a result of that hydraulic shocks takes place. The damping of these shocks can be achieved by the installation of the by-pass devices between the parallel lines of the piping system. The analytical calculations demonstrate that the reduction in hydraulic shocks reaches 40% and considerable part of the electric power (from 5 up to 21%) is economized by using the by-pass devices, the duration of pressure decline decreases by more than 1,5 times. Comparison of the calculations based on the developed algorithm with the results of practical studies at the pumping station (Syrdarya) has shown good convergence of analytical and experimental outcomes.

Modeling and Control of a Magnetic Bearing System for the Magnetically Suspended Centrifugal Blood Pump

We have developed a centrifugal blood pump with a magnetically suspended impeller to reduce the hemolysis level for long-term use. The main advance we have made was simplifying the traditional 5 axes controlled magnetic bearing system, since the total device should ultimately be small enough to implant into a human body. A simplified magnetic bearing system with only 3 actively controlled axes was designed to levitate the impeller. The state equations of the magnetic bearing plant were established using Lagrange's methods, and using the results, a linear quadratic optimal controller was designed to regulate the position of the impeller. Flow rate and differential pressure of 5L/min and 300 mmHg, respectively at a motor speed of 2750 rpm was achieved from a mock circulation setup. These results show satisfactory performance as a cardiopulmonary bypass device. The lowering of pumping efficiency as the clearance between the impeller and pump housing increased was negligible. Thus for power efficiency, the smallest gap not leading to a hemolysis level rise can be determined as a feasible operation clearance.

King of hearts: the true story of the maverick who pioneered open-heart surgery

King of hearts: the true story of the maverick who pioneered open-heart surgery

Anesthesia for Tracheal Resection: A New Technique of Airway Management in a Patient with Severe Stenosis of the Midtrachea

Anesthesia for Tracheal Resection: A New Technique of Airway Management in a Patient with Severe Stenosis of the Midtrachea

Anesthesia for Tracheal Resection: A New Technique of Airway Management in a Patient with Severe Stenosis of the Midtrachea

We report the combined use of a Fogarty catheter (FC), a 3.5-mm fiberoptic bronchoscope (FOB), and a 6.0 endotracheal tube (ETT) to intubate the lower trachea of a patient with a primary upper- and midtracheal tumor causing a 66% stenosis of the tracheal lumen at the level of the thoracic inlet. Initially, the 6.0 ETT, with the FOB and the FC fed to its tip, was placed above the tumor and rotated 90° counterclockwise. The FOB and the FC were advanced through the stenosis, and the FC cuff was inflated just above the carina. The ETT was advanced over the FOB toward the FC cuff, and the ETT cuff was inflated below the tumor and above the FC cuff. After inspection for blood and tumor debris through the FOB’s eyepiece, the FC cuff was deflated, both the FOB and FC were withdrawn, and intermittent positive pressure ventilation (IPPV) was begun.

Quantification of device adherent, circulating, and organ pool of thrombin and fibrinogen after cardiopulmonary bypass in a pig model.

The pool of thrombin and fibrinogen in circulation, in organs, and on cardiopulmonary bypass devices was quantified during and after cardiopulmonary bypass in four groups of 24 Yorkshire pigs (weight, 30-35 kg); two groups of 10 unoperated pigs were used as controls. Thrombin-alpha and fibrinogen were iodinated with 125iodide using an iodogen transfer technique; 250-300 microCi of these tracers were injected intravenously 1 hr before cardiopulmonary bypass. All pigs were systematically heparinized (activated clotting time > 400 sec); cardiopulmonary bypass was performed at 2.5-3.5 L/min at 28 degrees C using a centrifugal pump, oxygenator (Bentley Univox 1.8 m2; Bentley Inc., Irvine, CA), arterial filter (0.25 m2), and cardiotomy reservoir (BMR 3500) for 90 min, followed by a 90 min reperfusion and 180 min of cardiopulmonary bypass. Iodinated thrombin-alpha and fibrinogen in intact organs and samples of blood, organs, tissues, and oxygenator-arterial filter-cardiotomy reservoir were quantified with an ion chamber and a gamma counter, respectively. The percent of injected iodinated thrombin-alpha and fibrinogen dose (mean +/- SD) in organs and cardiopulmonary bypass devices of all groups of cardiopulmonary bypass pigs was calculated. Thrombin generated at the small area of surgical wounds (0.016-0.038 m2), and fibrin deposited on surfaces of cardiopulmonary bypass devices (2.59 m2), initiate and propagate thrombus formation and embolization. The protein level reached saturation values on all cardiopulmonary bypass devices at 180 min. High levels of thrombin and fibrinogen-fibrin circulate in blood and organs, and are adsorbed on cardiopulmonary bypass devices; this large blood pool of pro-coagulants in the cardiac cradle, tissues, and perfused organs may account for thrombi and emboli during and after cardiopulmonary bypass.

Valtrac-secured intracolonic bypass device: an experimental study.

The intracolonic bypass tube has been used both experimentally and clinically to protect the anastomotic site. A newly designed intracolonic bypass, the Valtrac-secured intracolonic bypass, which consisted of a biofragmentable anastomosis ring (BAR) and was connected with a soft, thin vinyl tube, was used in the colon approximately 5 to 10 cm proximal to the anastomotic site. The distal end of the vinyl tube is passed through the colonic anastomosis to the anus to bypass the fecal stream. Eighteen piglets were divided into three groups of six each. Group A piglets underwent colon resection and rough anastomosis with large gaps between sutures, followed by Valtrac-secured intracolonic bypass. Group B piglets underwent the same procedures, but a colonic outlet obstruction also was done with pursestring sutures tied over the anus. Group C piglets underwent colon resection and rough anastomosis, but no intracolonic bypass tube was inserted (as in the control group). All Group A and Group B piglets survived. Passage of the BARs occurred approximately two weeks later. As the barium enema passed through the bypass tube, it showed a patent BAR-secured tube and intact anastomosis with no leakage. In Group C, anastomotic leakage occurred in four of six piglets, three of which died. Barium enema showed leakage at the anastomotic site. In the animal model we used, our new intracolonic bypass device proved to be a simple, safe, reliable means of protecting the anastomotic site and, thereby, eliminated the need for a diverting colostomy. Still we need further steps to test its potential in clinical use.

Monitoring of r-Hirudin Anticoagulation during Cardiopulmonary Bypass – Assessment of the Whole Blood Ecarin Clotting Time

The use of recombinant (r) hirudin as an anticoagulant in performing extracorporeal circulation systems including cardiopulmonary bypass (CPB) devices requires a specific and easy to handle monitoring system. The usefulness of the celite-induced activated clotting time (ACT) and the activated partial thromboplastin time (APTT) for r-hirudin monitoring has been tested on ex vivo blood samples obtained from eight patients treated with r-hirudin during open heart surgery. The very poor relationship between the prolongation of the ACT and APTT values and the concentration of r-hirudin as measured using a chromogenic factor IIa assay indicates that both assays are not suitable to monitor r-hirudin anticoagulation. As an alternative approach a whole blood clotting assay based on the prothrombin-activating snake venom ecarin has been tested. In vitro experiments using r-hirudin-spiked whole blood samples showed a linear relationship between the concentration of hirudin added and the prolongation of the clotting times up to a concentration of r-hirudin of 4.0 micrograms/ml. Interassay coefficients (CV) of variation between 2.1% and 5.4% demonstrate the accuracy of the ecarin clotting time (ECT) assay. Differences in the interindividual responsiveness to r-hirudin were analyzed on r-hirudin-spiked blood samples obtained from 50 healthy blood donors. CV-values between 1.8% and 6% measured at r-hirudin concentrations between 0.5 and 4 micrograms/ml indicate remarkably slight differences in r-hirudin responsiveness. ECT assay results of the ex vivo blood samples linearily correlate (r = 0.79) to the concentration of r-hirudin. Moreover, assay results were not influenced by treatment with aprotinin or heparin. These findings together with the short measuring time with less than 120 seconds warrant the whole blood ECT to be a suitable assay for monitoring of r-hirudin anticoagulation in cardiac surgery.