Improving Cardiopulmonary Bypass: Heparin-Coated Circuits

Heparin-coated circuits have been repeatedly proven to reduce the inflammatory response and foreign surface activation triggered upon initiation of cardiopulmonary bypass (CPB). In recent years, increasing numbers of studies are proving significant reductions in postoperative blood loss and transfusion requirements and improvements in clinical outcomes as a result of heparin-coated circuits. These results are promising steps in our efforts to improve CPB, as our patient population gets older and more complicated

An In Vitro Evaluation of an Automatic Clamp for Use with Centrifugal Pumps

The risk of air emboli is a concern for all perfusionists. A new clamping device for use with centrifugal pumps is designed to clamp both the arterial and venous lines at the first indication of air or retrograde flow, thereby allowing the perfusionist to evaluate the situation and correct the problem before entraining air into the arterial pump head. After evaluating this device in our lab, we conclude that this new safety device should be added to the heart lung machine by all perfusionists using centrifugal pumps

Unique Considerations for the Spinal Cord Injured Patient Undergoing Cardiac Surgery Utilizing Cardiopulmonary Bypass

A 37-year-old male with mitral valve regurgitation presented for mitral valve replacement. He has been a C5 quadriplegic for 13 years. The patient had been discharged 2 months before to this admission after a complicated hospital course for Staphylococcus aureus infection of the left hip. His course was complicated by adult respiratory distress syndrome (ARDS) requiring prolonged intubation, acute renal failure (ARF) requiring dialysis, 10-day coma, and bacterial endocarditis now requiring mitral valve replacement. After initial stabilization with antibiotics and gradual improvement of the multiorgan system failure, the patient presented for valve replacement and worsening congestive heart failure (CHF). Para- and quadriplegic patients rarely undergo cardiac surgery requiring cardiopulmonary bypass (CPB). The explanation for this low incidence of heart surgery in this patient population ranges from physiologic changes from the spinal cord injury to their relatively short life span. Therefore, there is no vast knowledge of how these patients with spinal cord injury will physiologically respond to CPB. Chronic paraplegia presents unique anesthetic and perfusion challenges. General anesthesia for a patient with prolonged spinal cord damage can be difficult because of dysreflexia, muscle wasting, and potassium changes with depolarizing muscle relaxants. For the perfusionist, chronic paraplegia also accentuates hemodynamic responses to nonpulsatile flow with low peripheral vascular resistance common and difficult to treat. Dramatic increases in circulating catecholamine levels are a secondary result of the initiation of CPB that can cause a hypo- and hypertensive state. Depending on the level of spinal cord injury, one might expect acute hypo- or hypertension with the various phases of open-heart surgery and CPB. A viscous circle may occur because the hypertensive state is exaggerated because of inhibitory signals not passed below the spinal cord lesion and, therefore, the vasoconstrictive reflex continues unabated. The attack usually occurs abruptly and can lead to cerebrovascular hemorrhage and death if not controlled. Fortunately, we found this patient did not develop mass autonomic dysreflexia and was not difficult to wean from CPB. The problems associated with spinal cord injury present potential complications to this patient population. Numerous triggering mechanisms may lead to a variety of clinical complications. Consideration of a response/treatment management plan for potential problems must be exercised by the surgical team

Cardiopulmonary Bypass with Deep Hypothermic Circulatory Arrest for a Patient with Sickle Cell Anemia: A Case Report

A 36-year-old sickle cell anemia patient undergoing a pulmonary thromboendarterectomy required the use of cardiopulmonary bypass incorporating deep hypothermic circulatory arrest. Being aware of reported incidences of sickling crises, a team of the surgeon, anesthesiologist, hematologist, and perfusionist met to devise a plan of treatment. Treatment included preoperative and intraoperative exchange transfusion, optimal blood gas management, and increased blood flows during bypass. The surgical procedure was performed and was successful in reducing pulmonary hypertension, incorporating a team approach and utilizing these techniques. No incidence of adverse sickling events was observed during this procedure

An In Vitro Comparison of Gas Transfer and Pressure Drop of the Bentley Duraflo Coated Spiral Gold and the Medtronic Carmeda Coated Maxima Hollow Fiber Membrane Oxygenators

Two models of heparin coated, hollow fiber membrane oxygenators were tested in vitro to compare gas transfer and transoxygenator pressure drop using an established protocol. Oxygen and carbon dioxide transfer rates were measured at blood flows of 2.5 and 5.0 liters per minute with gas flow : blood flow ratios of 1:1 and 2:1 at both blood flows. All testing was performed under normothermic conditions. The data shows that oxygen transfer increases as blood flow is increased in both oxygenators. Similarly, carbon dioxide transfer is increased by both increased blood and gas flows. Finally, the pressure drop was dependent on blood flow rate alone. This study demonstrated these two oxygenators to be comparable in both oxygen and carbon dioxide transfer and also in transoxygenator pressure drop

An In Vitro Protocol for Evaluation and Comparison of Membrane Oxygenators

With the trend in open heart surgery toward normothermic bypass and warm blood cardioplegia, greater demand is being placed on the perfusionist to select an oxygenator that will perform safely and efficiently under a variety of conditions. While manufacturers report performance parameters for their products, the data is often not comparable due to widely differing conditions. Recent in vitro evaluation techniques employed to characterize membrane oxygenators do not simulate the actual oxygenator conditions observed during cardiopulmonary bypass. Biocompatibility and drug delivery are reported but comparisons of different oxygenator performance parameters are not completely addressed. We have designed a test circuit and an evaluation protocol to simultaneously characterize the performance of multiple oxygenators under identical conditions. The test circuit is designed to simulate clinical conditions and to evaluate gas exchange, blood path pressures, gas path pressures, and hemolysis. Previously reported studies have relied on a comparison of a single membrane oxygenator and a single bubble oxygenator. Our protocol will compare multiple membrane oxygenators, in vitro, under similar clinically relevant conditions. Such testing would be done prior to animal or clinical trials. Furthermore in vitro tests should be more reproducible and more discriminating than are ex vivo tests

Role of Cytokine Hemoadsorption in Cardiopulmonary Bypass-Induced Ventricular Dysfunction in a Porcine Model

Little is known about the effect of cardiopulmonary bypass alone on cardiac function; in an attempt to illuminate this relationship and test a possible mechanism, we used Cytosorb™, a device capable of removing virtually all types of circulating cytokines to test the hypothesis that hemoadsorption of cytokines during bypass attenuates bypass-induced acute organ dysfunction. Twelve Yorkshire pigs (50–65 kg) were instrumented with a left ventricular conductance catheter. Baseline mechanics and cytokine expression (tumor necrosis factor [TNF], interleukin-6 [IL-6], and interleukin-10) were measured before and hourly after 1 hour of normothermic cardiopulmonary bypass. Animals underwent bypass without (cardiopulmonary bypass [CPB], n = 6) or with (CPB+HA, n = 6) the Cytosorb™ device. Data were compared with “historical” controls (n = 6) that were similarly instrumented but underwent observation instead of bypass. Five hours after separation from bypass (or observation), animals were euthanized. Myocardial water content was determined postmortem. Neither TNF nor IL-6 was significantly elevated in either experimental group versus controls at any time point. Preload recruitable stroke work and dP/dtmax were significantly depressed immediately after separation from bypass in both CPB+HA and CPB and remained depressed for the duration of the experiment. Although Tau remained unchanged, dP/dTmin was significantly diminished in both bypass groups at all time points after separation from bypass. Cytokine hemoadsorption had no effect on any measurable index of function. Differences in postmortem data were not evident between groups. One hour of normothermic CPB results in a significant and sustained decline in left ventricular function that appears unrelated to changes in cytokine expression. Because we did not appreciate a significant change in cytokine concentrations postbypass, the capacity of cytokine hemoadsorption to attenuate CPB-induced ventricular dysfunction could not be assessed