Cardiopulmonary bypass

The primary function of the cardiopulmonary bypass (CPB) machine is maintaining systemic perfusion while the heart is under manipulation, its chambers are open or it suffers severe dysfunction. The CPB circuit consists of a reservoir, blood pump, oxygenator, heat exchanger, arterial filter, cardioplegia delivery device and cannulae, interconnected by various sized tubing.     

Oxygenation of the cerebral and coronary circulation with right axillary artery perfusion during venoarterial bypass in primates.

The effectiveness of right axillary artery perform in delivering oxygenated blood to the cerebral and coronary circulation during venoarterial bypass in primates was studied. Both right and left common carotid flow measurements and arterial gas measurements revealed high flows and elevated PO2 levels. Incomplete mixing in the ascending aorta was observed from cineangiograms taken at various pump oxygenator flows in 1 animal. The results demonstrated that the brain receives excellent oxygenation at all bypass levels. However, the coronary circulation is perfused primarily by blood ejected from the left ventricle and receives only minimal contribution of well-oxygenated blood from the pump oxygenator circuit. Therefore, the heart may suffer prolonged hypoxemia during long-term venoarterial bypass for acute respiratory insufficiency.     

Establishment of an animal model of non-transthoracic cardiopulmonary bypass in rats

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Postoperative care of adult cardiac surgery patients

Over 35,000 cardiac operations are performed in the UK each year, with the majority requiring cardiopulmonary bypass (CPB). CPB replaces the heart and lung function temporarily by providing non-pulsatile oxygenated blood flow in order to facilitate arrested heart surgery. The use of an extracorporeal circuit and cardioplegia causes the release of pro-inflammatory cytokines inducing a systemic inflammatory response, coagulation cascade activation, haemodilution and transient myocardial depression among other effects. These manifest as a series of typical pathophysiological derangements, which require the adoption of a standard management strategy. The aim of this article is to provide an overview of the key issues including cardiac, respiratory, neurological, renal and haemostatic complications, which may arise while managing the postoperative cardiac surgical patient.     

In Vitro Hemodynamic Evaluation of Five 6 Fr and 8 Fr Arterial Cannulae in Simulated Neonatal Cardiopulmonary Bypass Circuits

The objective of this study was to evaluate five small‐bore arterial cannulae (6Fr and 8Fr) in terms of pressure drop and hemodynamic performance in simulated neonatal cardiopulmonary bypass (CPB) circuits. The experimental circuits consisted of a Jostra HL‐20 roller pump, a Terumo Capiox Baby FX05 oxygenator with integrated arterial filter, an arterial and a venous tubing (1/4, 3/16, or 1/8 in × 150 cm), and an arterial cannula (Medtronic Bio‐Medicus 6Fr and 8Fr, Maquet 6Fr and 8Fr, or RMI Edwards 8Fr). The circuit was primed using lactated Ringer's solution and heparinized packed human red blood cells (hematocrit 30%). Trials were conducted at different flow rates (6Fr: 200–400 mL/min; 8Fr: 200–600 mL/min) and temperatures (35 and 28°C). Flow and pressure data were collected using a custom‐based data acquisition system. Higher circuit pressure, circuit pressure drop, and hemodynamic energy loss across the circuit were recorded when using small‐bore arterial cannula and small inner diameter arterial tubing in a neonatal CPB circuit. The maximum preoxygenator pressures reached 449.7 ± 1.0 mm Hg (Maquet 6Fr at 400 mL/min), and 395.7 ± 0.4 mm Hg (DLP 8Fr at 600 mL/min) when using 1/8 in ID arterial tubing at 28°C. Hypothermia further increased circuit pressure drop and hemodynamic energy loss. Compared with the others, the RMI 8Fr arterial cannula had significantly lower pressure drop and energy loss. Maquet 6Fr arterial cannula had a greater pressure drop than the DLP 6Fr. A small‐bore arterial cannula and arterial tubing created high circuit pressure drop and hemodynamic energy loss. Appropriate arterial cannula and arterial tubing should be considered to match the expected flow rate. Larger cannula and tubing are recommended for neonatal CPB. Low‐resistance neonatal arterial cannulae need to be developed.     

Hematologic and endocrinologic effects of pulsatile cardiopulmonary bypass using a centrifugal pump]

The effects of pulsatile and nonpulsatile flow during cardiopulmonary bypass (CPB) with of centrifugal pump (Sarns) and membrane oxygenator, on blood cells, hemodynamics, and hormonal response were studied. In the pulsatile group (group P) in which pulsatile flow was generated by centrifugal pump and a 20 Fr arterial cannula was used, hemolysis and reduction of platelet count during CPB were more marked than in the nonpulsatile group (group NP), in which the same type of circuit was used. When the 20 Fr arterial cannula was replaced with a 24 Fr cannula (group Pc), the rate of hemolysis during CPB was significantly reduced compared with that in group P (p less than 0.05). The rate of rise in plasma free hemoglobin from 10 to 70 minutes CPB in group Pc was 15.0 mg/dl/hr, this value did not exceed that in either group NP or in group Pr, in which a roller pump rather than centrifugal pump was used to generate pulsatile flow. These findings show that pulsatile CPB with a centrifugal pump produces no deleterious hematologic effect in clinical use. The rise in the level of angiotensin II in group P was significantly smaller than that in group NP (p less than 0.05), and the rise in plasma renin activity and levels of angiotensin I, adrenalin and noradrenaline were smaller than those in group NP, although these differences were no significance. These findings indicate that the centrifugal pump generates pulsatile flow effectively, although not so effectively as to prevent the rise in peripheral vascular resistance. During CPB, there was no change in levels of thyroid hormones, including free T3, free T4 and reverse T3, in either pulsatile groups P and Pc or nonpulsatile group. TSH level in group Pc was significantly elevated in contrast with that in the nonpulsatile group (p less than 0.05), in which no change in TSH level was seen. It is suggested that pulsatile perfusion using a centrifugal pump might maintain sufficient hypothalamic-pituitary function to permit secretion of TSH in response to various stimuli.     

Partial cardiopulmonary bypass in rats using a hollow fibre oxygenator

Despite new minimally invasive techniques, cardiopulmonary bypass (CPB) is still necessary for many major operations in the field of cardiac surgery. Unwanted side effects of CPB are well known but poorly understood. We therefore developed a rodent model to study the pathophysiology of these potential complications. Male Fischer rats were anaesthetized, intubated and ventilated. The carotid artery and jugular vein were cannulated. The blood was actively drained from the venous circulation and further transferred by a miniaturized roller pump to a hollow fibre oxygenator and back to the animal via the carotid artery. The roller pump produces a pulsatile blood flow between 5 and 40 ml/min. The surface of the hollow fibre oxygenator is 0.025 m2. The priming volume (Ringer solution) of the whole system is 12 ml. Animals were catheterized and brought in partial bypass for a mean of 50+/-15 min. Normal cardiac function after successful weaning was confirmed by electrocardiography and blood pressure measurements. This technical study demonstrates the feasibility of a small animal model of CPB. The main improvement over existing techniques is the use of a highly effective hollow fibre oxygenator with a minimized priming volume. Therefore, no additional animals are needed as blood donors.     

Pediatric cardiopulmonary bypass adaptations for long-term survival of baboons undergoing pulmonary artery replacement

Cardiopulmonary bypass (CPB) protocols of the baboon (Papio cynocephalus anubis) are limited to obtaining experimental data without concern for long-term survival. In the evaluation of pulmonary artery tissue engineered heart valves (TEHVs), pediatric CPB methods are adapted to accommodate the animals' unique physiology enabling survival up to 6 months until elective sacrifice. Aortic access was by a 14F arterial cannula and atrial access by a single 24F venous cannula.The CPB circuit includes a 3.3 L/min flow rated oxygenator, 1/4" x %" arterial-venous loop, 3/8" raceway, and bubble trap. The prime contains 700 mL Plasma-Lyte, 700 units heparin, 5 mL of 50% dextrose, and 20 mg amiodarone. Heparinization (200 u/kg) targets an activated clotting time of 350 seconds. Normothermic CPB was initiated at a 2.5 L/m2/min cardiac index with a mean arterial pressure of 55-80 mmHg. Weaning was monitored with transesophageal echocardiogram. Post-CPB circuit blood was re-infused. Chest tubes were removed with cessation of bleeding. Extubation was performed upon spontaneous breathing. The animals were conscious and upright 3 hours post-CPB. Bioprosthetic valves or TEHVs were implanted as pulmonary replacements in 20 baboons: weight = 27.5 +/- 5.6 kg, height = 73 +/- 7 cm, body surface area = 0.77 m2 +/- 0.08, mean blood flow = 1.973 +/- .254 L/min, core temperature = 37.1 +/- .1 degree C, and CPB time = 60 +/- 40 minutes. No acidosis accompanied CPB. Sixteen animals survived, four expired. Three died of right ventricular failure and one of an anaphylactoid reaction. Surviving animals had normally functioning replacement valves and ventricles. Baboon CPB requires modifications to include high systemic blood pressure for adequate perfusion into small coronary arteries, careful CPB weaning to prevent ventricular distention, and drug and fluid interventions to abate variable venous return related to a muscularized spleno-splanchnic venous capacity.     

Evaluation of Different Diameter Arterial Tubing and Arterial Cannulae in Simulated Neonatal/Pediatric Cardiopulmonary Bypass Circuits

The objective of this study is to evaluate three different diameters of arterial tubing and three diameters of arterial cannulae in terms of pressure drop, and hemodynamic energy delivery in simulated neonatal/pediatric cardiopulmonary bypass (CPB) circuits. The CPB circuit consisted of a Terumo Capiox Baby FX05 oxygenator (Terumo Corporation, Tokyo, Japan), arterial tubing (1/4 in, 3/16 in, or 1/8 in × 150 cm), and a Medtronic Bio‐Medicus arterial cannula (8, 10, or 12 Fr; Medtronic, Inc., Minneapolis, MN, USA). The pseudo patient's pressure was maintained at 50 mm Hg. The circuit was primed using lactated Ringer's solution and heparinized packed human red blood cells (hematocrit 30%). Trials were conducted at different flow rates and temperatures (35 and 28°C). Flow and pressure data were collected using a custom‐based data acquisition system. Using 8 Fr arterial cannula at 500 mL/min, small diameter arterial tubing generated higher circuit pressure (294.6 ± 0.1 mm Hg [1/8 in], 213.5 ± 0.5 mm Hg [3/16 in], 208.4 ± 0.4 mm Hg [1/4 in] at 35°C) and arterial line pressure drop (158.3 ± 0.1 mm Hg [1/8 in], 79.6 ± 0.1 mm Hg [3/16 in], 62.1 ± 0.1 mm Hg [1/4 in] at 35°C). Using 10 Fr arterial cannula at 1000 mL/min, pre‐oxygenator pressures were 266.8 ± 0.2 mm Hg (3/16 in) and 248.0 ± 0.3 mm Hg (1/4 in); arterial line pressure drops were 111.6 ± 0.0 mm Hg (3/16 in) and 74.0 ± 0.1 mm Hg (1/4 in) at 35°C. When using 12 Fr arterial cannula at 1500 mL/min, preoxygenator pressures reached 324.4 ± 0.3 mm Hg (3/16 in) and 302.5 ± 0.4 mm Hg (1/4 in); arterial line pressure drops were 154.0 ± 0.1 mm Hg (3/16 in) and 92.0 ± 0.2 mm Hg (1/4 in) at 35°C. Pressure drops across arterial line tubing were main CPB circuit pressure drops. High flow rate, hypothermia, small diameter arterial tubing. and arterial cannula created more hemodynamic energy at the preoxygenator site, but energy loss across CPB circuit also increased. Although small diameter (<1/4 in ID) arterial tubing may decrease total CPB priming volume, it also led to significantly higher circuit pressure, higher pressure drop, and more hemodynamic energy loss across CPB circuit. Larger diameter arterial cannula had less pressure drop and allowed more hemodynamic energy delivery to the patient.     

The Type of Aortic Cannula and Membrane Oxygenator Affect the Pulsatile Waveform Morphology Produced by a Neonate-Infant Cardiopulmonary Bypass System In Vivo

Although the debate still continues over the effectiveness of pulsatile versus nonpulsatile perfusion, it has been clearly proven that there are several significant physiological benefits of pulsatile perfusion during cardiopulmonary bypass (CPB) compared to nonpulsatile perfusion. However, the components of the extracorporeal circuit have not been fully investigated regarding the quality of the pulsatility. In addition, most of these results have been gathered from adult patients, not from neonates and infants. We have designed and tested a neonate-infant pulsatile CPB system using 2 different types of 10 Fr aortic cannulas and membrane oxygenators in 3 kg piglets to evaluate the effects of these components on the pulsatile waveform produced by the system. In terms of the methods, Group 1 (Capiox 308 hollow-fiber membrane oxygenator and DLP aortic cannula with a very short 10 Fr tip [n =2]) was subjected to a 2 h period of normothermic pulsatile CPB with a pump flow rate of 150 ml/kg/min. Data were obtained at 5, 30, 60, 90, and 120 min of CPB. In Group 2 (Capiox 308 hollow-fiber membrane oxygenator and Elecath aortic cannula with a very long 10 Fr tip [n =7]) and Group 3 (Cobe VPCML Plus flat sheet membrane oxygenator and DLP aortic cannula with a very short 10 Fr tip [n =7]), the subjects' nasopharyngeal temperatures were reduced to 18°C followed by 1 h of deep hypothermic circulatory arrest (DHCA) and then 40 min rewarming. Data were obtained during normothermic CPB in the pre- and post-DHCA periods. The criteria of pulsatility evaluations were based upon pulse pressure (between 30 and 40 mm Hg), aortic dp/dt (greater than 1000 mm Hg/s), and ejection time (less than 250 ms). The results showed that Group 1 produced flow which was significantly more pulsatile than that of the other 2 groups. Although the same oxygenator was used for Group 2, the quality of the pulsatile flow decreased when using a different aortic cannula. Group 3 did not meet any of the criteria for physiologic pulsatility. In conclusion these data suggest that in addition to a pulsatile pump, the aortic cannula and the membrane oxygenator must be chosen carefully to achieve physiologic pulsatile flow during CPB.     

Experimental use of an ultra-low prime neonatal cardiopulmonary bypass circuit utilizing vacuum-assisted venous drainage.

In adult cardiopulmonary bypass surgery, vacuum assisted venous drainage has become a popular technique to augment venous return to the bypass circuit. The application of this technique in neonatal cardiopulmonary bypass surgery could be beneficial to the further miniaturization of neonatal circuitry by coupling radical respositioning of the oxygenator and pump console with decreasing line length. This report communicates the use of an investigational, vacuum assisted venous drainage neonatal circuit that is positioned at patient level utilizing a modified pump console with elevated double head twin roller pumps. The circuit, including the oxygenator, arterial line, venous line, raceway tubing, and a functional level in the venous reservoir has a priming volume of 107 ml. Initial bench and animal tests have demonstrated that this technique may be clinically feasible in CPB applications. With vacuum assisted venous drainage, the goal of asanguinous neonatal cardiac surgery could become a reality. Safety issues must be adequately addressed to ensure that this technique does not impose unacceptable risks.     

Impact of tubing length on hemodynamics in a simulated neonatal extracorporeal life support circuit

During extracorporeal life support (ECLS), a large portion of the hemodynamic energy is lost to various components of the circuit. Minimization of this loss in the circuit leads to better vital organ perfusion and decreases the risk of systemic inflammation. In this study, we evaluated the hemodynamic properties of differing lengths of tubing in a simulated neonatal ECLS circuit. The neonatal ECLS circuit used in this study included a Capiox Baby RX05 oxygenator (Terumo Corporation, Tokyo, Japan), a Rotaflow centrifugal pump (MAQUET Cardiopulmonary AG, Hirrlingen, Germany), and a heater and cooler unit. An 8 Fr Biomedicus arterial and a 10 Fr Biomedicus venous cannula were connected to the pseudopatient. One‐fourth inch tubing was used for both the arterial and the venous line. A Hoffman clamp was located upstream from the pseudopatient to maintain a certain patient pressure. Three pressure transducers were placed at different sites: postoxygenator, prearterial cannula, and postarterial cannula. The system was primed with Lactated Ringer's solution; human blood was then added to maintain a hematocrit of 40%. The volume of the pseudopatient was 500 mL. We hemodynamically evaluated three circuits with different lengths of tubing: 6, 4, and 2 feet (182.88, 121.92, and 60.96 cm, respectively) for both arterial and venous lines; the priming volumes including all of the components of the circuits were 195, 155, and 115 mL, respectively. In each circuit, we measured the pressure drops of the arterial tubing and the arterial cannula, as well as the flow rates at different rpm (1750–3000, 250 intervals) under three patient pressures (40, 60, and 80 mm Hg). All the experiments were conducted at 37°C. The pressure drop across the arterial cannula is much larger than that of arterial tubing in all set‐ups, especially under high flow rates. Upon cutting the tubing from 6 to 2 feet, the pressure drop of the arterial tubing decreased by half, while the pressure drop of the arterial cannula increased due to the slightly higher flow rates. These results suggest that compared to the arterial tubing, the arterial cannula has a larger impact on the hemodynamics of the circuit. There is a little influence of tubing length on the circuit flow rate.     

Development of a completely closed circuit using an air filter in a drainage circuit for minimally invasive cardiac surgery

The completely closed circuit system is the future direction of cardiopulmonary bypass because of its compactness and superior biocompatibility. The most serious obstacle for clinical application is the sucking of air bubbles into the drainage circuit. The purpose of this study was to remove the air bubbles from the drainage circuit. Infusing 50 ml/min of air bubbles into the drainage circuit of the usual closed circuit, and infusing 50, 100, and 150 ml/min of air into the drainage circuit of a newly developed closed circuit (drainage circuit using an air filter), the number and size of air bubbles were observed at the outlet of the arterial filter. In the usual closed circuit, many air bubbles of over 40 microm were detected within 5 s at a blood flow of 4 L/min because the centrifugal pump decreased the size of the bubbles, which then passed through the oxygenator and arterial filter. Air bubbles of over 40 micro were not detected in the newly developed closed circuit within 5 min at a blood flow of 4 L/min. The removal of air mixed into the completely closed circuit was possible with a drainage circuit using an air filter that was developed. The clinical use of the completely closed circuit for minimally invasive cardiac surgery (MICS) became possible based on this development.     

Studies of emergency cardiopulmonary bypass (ECPB) for cardiopulmonary-cerebral resuscitation; (1) Introduction of a portable-percutaneous ECPB system]

The authors have developed an ECPB system, which can be applied quickly, safely and easily under an emergency condition requiring cardiac massage and artificial ventilation. Fundamentally, the ECPB system consists of 3 parts; a portable ECPB apparatus, a pair of percutaneous cannulae and a short circuit connecting an oxygenator with the cannulae. The ECPB apparatus is assembled with commercially available components (i.e., a centrifugal pump, a battery pack, a temperature controller, a compact membrane oxygenator with a heat exchanger, etc) and they are placed on a mobile cart. The circuit is primed with 300 ml of lactated Ringer solution. The priming can be done within 15 minutes via a reservoir. It is also possible to keep the primed circuit to be ready for emergency use at least for a week. The cannulae are placed intravascularly through the femoral artery and vein by using the Seldinger's percutaneous method. In an emergency situation, the arterial and venous cannulations are carried out separately on the both inguinal regions to save time. The tip of the venous cannula is adjusted to be placed near the right atrium under fluoroscopy. Initiation of ECPB via the femoro-femoral V-A cannulae assures instant and stable supply of oxygenated blood to all of the vital organs. At the present time, nothing is more important than a quick supply of oxygenated blood to the brain to ameliorate the post-ischemic brain damage.     

Bypass flow, mean arterial pressure, and cerebral perfusion during cardiopulmonary bypass in dogs

OBJECTIVE: To determine if normal cardiopulmonary bypass (CPB) pump flows maintain cerebral perfusion in the context of reduced mean arterial pressure at 33 degrees C. DESIGN: A prospective investigation. SETTING: Animal CPB research laboratory. PARTICIPANTS: Seven dogs that underwent CPB. INTERVENTIONS: Seven dogs underwent CPB at 33 degrees C using alpha-stat management and a halothane, fentanyl-midazolam anesthetic. Cerebral blood flow was measured using the sagittal sinus outflow technique. After control measurements at 70 mm Hg, cerebral physiologic values were determined under four conditions in random order: (1) mean arterial pressure of 60 mm Hg achieved by a reduction in pump flow, (2) mean arterial pressure of 60 mmHg determined by partial opening of a femoral arterial-to-venous reservoir shunt, (3) mean arterial pressure of 45 mm Hg by reduced pump flow, and (4) mean arterial pressure of 45 mm Hg by shunt. A 9F femoral arterial-to-venous reservoir shunt was controlled by a screw clamp. MEASUREMENTS AND MAIN RESULTS: Except for the controlled variables of mean arterial pressure and bypass flow, physiologic determinants of cerebral blood flow (temperature, PaCO2 and hematocrit) did not differ under any of the CPB conditions. Pump flow per se was not a determinant of cerebral perfusion. Cerebral blood flow and cerebral oxygen delivery did not differ with changes in pump flow if mean arterial pressure did not differ. Cerebral blood flow depended on mean arterial pressure under all pump flow conditions, however. CONCLUSIONS: Over the range of flows typical in adult CPB at 33 degrees C, pump flow does not have an effect on cerebral perfusion independent of its effect on mean arterial pressure. A targeted pump flow per se is not sufficient to maintain cerebral perfusion if mean arterial blood pressure is reduced.     

In Vitro Evaluation of an Alternative Neonatal Extracorporeal Life Support Circuit on Hemodynamic Performance and Bubble Trap

The objective of this study was to evaluate an alternative neonatal extracorporeal life support (ECLS) circuit with a RotaFlow centrifugal pump and Better‐Bladder (BB) for hemodynamic performance and gaseous microemboli (GME) capture in a simulated neonatal ECLS system. The circuit consisted of a Maquet RotaFlow centrifugal pump, a Quadrox‐iD Pediatric diffusion membrane oxygenator, 8 Fr arterial cannula, and 10 Fr venous cannula. A “Y” connector was inserted into the venous line to allow for comparison between BB and no BB. The circuit and pseudopatient were primed with lactated Ringer's solution and packed human red blood cells (hematocrit 35%). All hemodynamic trials were conducted at flow rates ranging from 100 to 600 mL/min at 36°C. Real‐time pressure and flow data were recorded using a data acquisition system. For GME testing, 0.5 cc of air was injected via syringe into the venous line. GME were detected and characterized with or without the BB using the Emboli Detection and Classification Quantifier (EDAC) System. Trials were conducted at flow rates ranging from 200 to 500 mL/min. The hemodynamic energy data showed that up to 75.2% of the total hemodynamic energy was lost from the circuit. The greatest pressure drops occurred across the arterial cannula and increased with increasing flow rate from 10.1 mm Hg at 100 mL/min to 114.3 mm Hg at 600 mL/min. The EDAC results showed that the BB trapped a significant amount of the GME in the circuit. When the bladder was removed, GME passed through the pump head and the oxygenator to the arterial line. This study showed that a RotaFlow centrifugal pump combined with a BB can help to significantly decrease the number of GME in a neonatal ECLS circuit. Even with this optimized alternative circuit, a large percentage of the total hemodynamic energy was lost. The arterial cannula was the main source of resistance in the circuit.     

Cardiopulmonary bypass

The purpose of cardiopulmonary bypass is to maintain perfusion and oxygenation of the vital organs in the absence of heart and lung function, usually to facilitate surgery on the heart, but occasionally in other situations. Although the intricacies of the modern extracorporeal circuit and the conduct of cardiopulmonary bypass are the domain of the clinical perfusion scientist (‘perfusionist’), safe surgery mandates a good understanding of some fundamentals by the anaesthetist and the surgeon. This review is aimed at the anaesthetist. First, we will systematically examine the main components of the extracorporeal circuit, travelling in the direction that blood travels, from the venous cannula to the arterial cannula. Then we will describe the process of preparing for bypass, ‘going on’, conducting a bypass run, and weaning and separation from bypass. It is crucial to have clear communication between the surgeon, perfusionist and anaesthetist. This can be difficult for the novice because a quite specific language has evolved in cardiac operating theatres to signal key events in the cardiopulmonary bypass sequence. As we go through this article, we will highlight commonly used terminology and expressions used.     

Ultrasound detection of micro-emboli in the middle cerebral artery during cardiopulmonary bypass surgery

The occurrence of neurological sequelae following cardiopulmonary bypass (CBP) surgery has stimulated interest in refining the techniques of extracorporeal circulation. Air micro-emboli originating from the oxygenator have been postulated as one source of cerebral damage. Since controversy still exists regarding the merits of bubble versus membrane oxygenators, this has prompted investigators to devise methods to determine the amount of micro-emboli produced during CPB. In this study, 27 patients undergoing CPB surgery for coronary artery disease (21) or valve replacement (6) were examined. The surgical and anaesthetic techniques were standardised in all patients except for the type of oxygenator used. A bubble oxygenator was used in 17 patients (Bentley Bio-10, William Harvey or Dideco) and a membrane oxygenator with a 25 microns filter in the remaining 10 patients (Bentley BOS CM50). Transcranial pulsed Doppler ultrasound was used to obtain blood velocity signals from the middle cerebral artery throughout CPB. A flow disturbance index (FDI) was defined which provided a representative index of the number of micro-emboli passing the ultrasound transducer. The FDI indicated the presence of gaseous micro-emboli during insertion of the aortic cannula in 22 of the 27 patients. In the 17 patients with a bubble oxygenator, the FDI ranged from 4-39. In the 10 patients with a membrane oxygenator, the FDI was always 0. Variation of gas flow rates in 3 patients with bubble oxygenators showed a change in the FDI from 4 +/- 4 at a flow rate of 2 l/min to 17 +/- 9 at 5 l/min.(ABSTRACT TRUNCATED AT 250 WORDS)     

High-risk aortic aneurysm repair with partial cardiopulmonary bypass

Two patients with severe cardiac dysfunction and measured left ventricular ejection fractions of 18% and 20% underwent aneurysm repair with the use of femoral vein--femoral artery partial cardiopulmonary bypass. While the aorta was clamped, blood was withdrawn through the venous cannula, and oxygenated blood was delivered to the legs through the arterial cannula. This procedure allowed clamping and unclamping of the aorta to proceed without hemodynamic fluctuation. Intraoperatively, cardiac output, mean arterial pressure, pulmonary artery diastolic pressure, right atrial pressure, pulmonary capillary wedge pressure, and systemic vascular resistance were measured. Both patients recovered, which indicates that this technique may be safely undertaken in the severely compromised patient with cardiac disease.     

Evaluation of Conventional Nonpulsatile and Novel Pulsatile Extracorporeal Life Support Systems in a Simulated Pediatric Extracorporeal Life Support Model

The objective of this study is to evaluate two extracorporeal life support (ECLS) circuits and determine the effect of pulsatile flow on pressure drop, flow/pressure waveforms, and hemodynamic energy levels in a pediatric pseudopatient. One ECLS circuit consisted of a Medos Deltastream DP3 diagonal pump and Hilite 2400 LT oxygenator with arterial/venous tubing. The second circuit consisted of a Maquet RotaFlow centrifugal pump and Quadrox‐iD Pediatric oxygenator with arterial/venous tubing. A 14Fr Medtronic Bio‐Medicus one‐piece pediatric arterial cannula was used for both circuits. All trials were conducted at flow rates ranging from 500 to 2800 mL/min using pulsatile or nonpulsatile flow. The post‐cannula pressure was maintained at 50 mm Hg. Blood temperature was maintained at 36°C. Real‐time pressure and flow data were recorded using a custom‐based data acquisition system. The results showed that the Deltastream DP3 circuit produced surplus hemodynamic energy (SHE) in pulsatile mode at all flow rates, with greater SHE delivery at lower flow rates. Neither circuit produced SHE in nonpulsatile mode. The Deltastream DP3 pump also demonstrated consistently higher total hemodynamic energy at the pre‐oxygenator site in pulsatile mode and a lesser pressure drop across the oxygenator. The Deltastream DP3 pump generated physiological pulsatility without backflow and provided increased hemodynamic energy. This novel ECLS circuit demonstrates suitable in vitro performance and adaptability to a wide range of pediatric patients.