Using computational fluid dynamics to evaluate a novel venous cannula (Smart canula) for use in cardiopulmonary bypass operating procedures.

Peripheral access cardiopulmonary bypass (CPB) is initiated with percutaneous cannulae (CTRL) and venous drainage is often impeded due to smaller vessel and cannula size. A new cannula (Smartcanula, SC) was developed which can change shape in situ and, therefore, may improve venous drainage. Its performance was evaluated using a 2-D computational fluid dynamics (CFD) model. The Navier-Stokes equations could be simplified due to the fact that we use a steady state and a 2-dimensional system while the equation of continuity (p constant) was also simplified. We compared the results of the SC to the CTRL using CFDRC (Version 6.6, CFDRC research corporation, Huntsville, USA) at two preloads (300 and 700 Pa). The SC's mass flow rate outperformed the CTRL by 12.1% and 12.2% at a pressures of 300 and 700 Pa, respectively. At 700 Pa, a pressure gradient of 50% was measured for the CTRL and 11% for the SC. The mean velocity at the 700 Pa for the CTRL was 1.0 m.s(-1) at exit while the SC showed an exit velocity of 1.3 m.s(-1). Shear rates inside the cannulae were similar between the two cannulae. In conclusion, the prototype shows greater mass flow rates compared to the classic cannula; thus, it is more efficient. This is also advocated by a better pressure gradient and higher average velocities. By reducing cannula-tip surface area or increasing hole surface area, greater flow rates are achieved.

Ex vivo evaluation of a new extracorporeal lung assist device: NovaLung membrane oxygenator.

When lung function is compromised,alternative devices need to be deployed in order to maintain blood oxygenation. A new device, NovaLung, has been designed for acute lung failure. We went about evaluating its gas exchange capability. Three calves (79.5 +/- 7.8 kg) were connected to the NovaLung System with a priming volume of 240 mL, gas exchange surface area of 1.3 m2 and exhibiting a biologically coated surface. A standard battery of blood samples were taken before implantation and over a six hour period. Hematocrit remained stable ranging from 27 +/- 4% (baseline) to 29 +/- 5% (6 hrs). Platelets were preserved ranging from 882 +/- 27.4 U/L (baseline) to 734 +/- 147 (6 hrs). LDH remained stable at 719 +/- 85 U/L (baseline) vs 686 +/- 190 U/L (6 hrs) and the pressure drop was maintained below 20 mmHg. Minimal hemolysis was observed. Oxygen transfer peaked at two hours acute extracorporeal lung support (ECLS)with a mean value of 130 +/- 50 ml/min. In conclusion, the device is easy to use,provides adequate O2 and CO2 transfer for partial lung support in an acute setting. Shows minimal signs of hemolysis and platelets levels are maintained throughout the six hour ECLS period.

Poly2-methoxyethylacrylate (PMEA) coated oxygenator: an ex vivo study.

UNLABELLED: PMEA is a hydrophilic polymer coating with a unique design that minimizes the adsorption and denaturation of proteins and blood cells. This study compares thrombus resistance, blood path resistance, thrombocyte profile, and blood trauma of the PMEA coated Capiox membrane oxygenator (Terumo, Japan) vs. an uncoated version. METHOD: Six calves (mean bodyweight: 75.3 +/- 4.5kg) were placed on cardiopulmonary bypass for 6 hours and randomly assigned to the coated or uncoated oxygenator, with a low heparinisation protocol (ACT > 180s). RESULTS: Macroscopically, red staining was observed in all uncoated oxygenators, and in none of the coated ones. Inlet pressure was significantly higher in the uncoated group (at 1 h: 279 +/- 25 vs. 175 +/- 11mmHg, p < 0.01 and at 6h: 217 +/- 10 vs. 171(8mmHg, p < 0.01). Thrombocyte count values (corrected for hematocrit and normalized by prebypass values) were significantly higher in the coated group (at 1 h: 76 +/- 6 vs. 53 +/- 13%, p < 0.01 and at 6 h: 70 +/- 6 vs. 44 +/- 26%, p < 0.01). Plasma hemoglobin was below 100mg/L in both groups throughout the experiments. CONCLUSIONS: When compared with uncoated oxygenator, PMEA coated oxygenator exhibited increased thrombus resistance with lower inlet pressure and lower thrombocyte consumption. In both groups, trauma to red cells was minimal, emphasizing the efficient design of this type of oxygenator.

A new expandable cannula to increase venous return during peripheral access cardiopulmonary bypass surgery.

Peripheral cannulation for cardiopulmonary bypass (CPB) is of prime interest in minimally invasive open heart surgery. As CPB is initiated with percutaneous cannulae, venous drainage is impeded due to smaller vessel and cannula size. A new cannula was developed which can change shape in situ and therefore may improve venous drainage. An in vitro circuit was set-up with a penrose latex tubing placed between the preload reservoir and the cannula, encasing the cannula's inlet and simulating the vena cava. The preload (P) was stabilised at 2 and at 5 mmHg respectively. The maximum flow rate was determined for 4 conditions: passive venous drainage (PVD) and assisted venous drainage (AVD) using a centrifugal pump at the 2 preload settings. We compared the results of the prototype cannula to classical femoral venous cannulae: basket 28Fr, a thoracic 28Fr and a percutaneous 27Fr. Under PVD conditions and a CVP of 2 mmHg, the prototype cannula's flow rate outperformed the next best cannula by 14% (p=0.0002) and 13% under AVD conditions (p=0.0001). Under PVD conditions and a CVP of 5 mmHg, the prototype cannula outperformed the percutaneous cannula by 19% (p=0.0001) and 14% under AVD conditions (p=0.0002). The new cannula outperforms the classical percutaneous venous cannulae during all of the four conditions tested in vitro.

Venous drainage with a single peripheral bicaval cannula for less invasive atrial septal defect repair.

New peripheral venous cannulae have recently been proposed for minimally invasive open cardiac surgery. We present a femoral venous cannula designed to simultaneously drain both superior and inferior vena cavae. Used in adult patients for atrial septal defect repair, the cannula allowed passive blood drainage of 70.6% +/- 11.7% of theoretical cardiac output. Drainage was augmented to 93.4% +/- 8.6% of theoretical cardiac output by means of a centrifugal pump.

Are standard human coagulation tests suitable in pigs and calves during extracorporeal circulation?

The thrombogenicity of membrane oxygenators as well as clotting parameters profiles, using standard human clotting tests, was analyzed in calves and pigs during 6 h perfusion. Three calves and 3 pigs were connected to extracorporeal circulation with standard heparinization. Blood samples were taken for coagulation variables throughout perfusion, and oxygenators were examined for clot deposits at the end of the experiment. Two out of 3 oxygenators of the calf group presented clot deposits while none in the pig group did. Baseline coagulation variables of pigs showed values similar to those of humans while neither extrinsic nor intrinsic pathways could be activated in calves with standard human coagulation tests. The calf model, in conclusion, was confirmed to be a difficult model for the testing of extracorporeal circulation device resistance to thrombus formation, which is, however, not reflected by standard human coagulation tests. The pig model is a better model in which both coagulation pathways could be activated with standard human coagulation tests.

A cardiopulmonary bypass score system to assess quality of perfusion performance.

During cardiopulmonary bypass, the perfusionist maintains physiological parameters laid down in protocols; this is his or her performance capability. In order to assess his or her performance we need to be able to analyse these physiological parameters objectively. We defined six parameters, pH, BE, PaCO2, PaO2, ACT and oesophageal temperature and gave them ideal values of 7.40+/-0.05, 0.0+/-2.5 mmol/l, 39.0+/-3.0 mmHg, 150+/-50 mmHg, 540+/-60 s and 37.2+/-0.2 degrees C, respectively. We established ranges and a score system: +/- one standard deviation of the mean for a score of zero; between +/- one and two standard deviations for a score of one; and greater than +/- two standard deviations for a score of two. We captured and analysed the most outlying value, with respect to known normal values, for each parameter recorded on the pump sheet. This was performed for 100 consecutive patients. Mean +/- standard deviation (medians) values for pH, BE, PaCO2, PaO2, ACT and oesophageal temperature were 7.41+/-0.07 (7.41), -1.85+/-2.37 mmol/l (-1.85 mmol/l), 34.6+/-5.42 mmHg (34.0 mmHg), 320+/-96.2 mmHg (317 mmHg), 558+/-164 s (503 s) and 37.3+/-0.5 degrees C (37.4 degrees C), respectively. We then analysed what percentage of our 100 patients fell within each score range for each of the six parameters. This is an efficient means in analysing whether the perfusionist abides by the protocols, what quality is supplied to the patient, does he or she react when he or she is faced with parameters that are out of range and finally advocating in-line blood gas monitoring. This is another step towards our goal of total quality management.

Atrial, ventricular, or both cannulation sites to optimize left ventricular assistance?

The efficiency of left ventricular assist devices (LVADs) depends on the capacity of the inflow cannula to drain blood into the pump. Left atrial (LA) and left ventricular (LV) sites were compared in an animal model mimicking different hemodynamic conditions. Three calves (56.3+/-5.0 kg) were equipped with a Thoratec LVAD. A regular cardiopulmonary bypass (CPB) circuit was used as a right ventricular assist device (RVAD) (jugular vein/pulmonary artery), and preload conditions were adjusted by storage (or perfusion) of blood into (or from) the venous reservoir. LA and LV drainage, tested separately or simultaneously, was measured by its effect on the LVAD's performance. The LVAD was used alone on a beating heart or together with the RVAD (biVAD) on a beating and on a fibrillating heart. Increasing the central venous pressure (CVP) highlighted the differences between the LA and LV cannulation sites when the LVAD was tested either alone or together with the RVAD (biVAD) on a beating heart. Drainage through the LA or the LV was similar when CVP was set at 8 mm Hg, and increasing CVP to 14 mm Hg allowed for better drainage through the LV cannula. In contrast, after induction of fibrillation to mimic extreme heart failure, the drainage was better through the LA cannula. Using both LA and LV cannulae simultaneously did not improve the LVAD output in any of the conditions tested. LV cannulation provides better blood drainage when used on a normal beating heart and, therefore, allows for increased LVAD performance. However, in severe heart failure, blood drainage through the LV cannula decreases and the LA cannulation site is superior.

Hemolysis and hematology profile during perfusion: inter-species comparison.

INTRODUCTION: Cardiopulmonary bypass components need to be tested on an animal model before their clinical application. Because their weight is similar to that of man, the calf and pig are often used. This study compares the impact of prolonged perfusion on hemolysis and hematology profile in both species. METHODS: Three calves (mean bodyweight: 77.2+/-4.4 kg) and three pigs (80+/-5.3 kg) were connected to an extracorporeal circulation circuit by jugular venous and carotid arterial cannulation, with a mean flow rate of 3.5L/min for 6h. After 7 days, the animals were sacrificed. A standard battery of blood samples was taken before, throughout, and 24h, 48h and 7 days after bypass. ANOVA was used for repeated measurements. RESULTS: Absolute values of red cell count were higher in the calf (p<0.001), while normalized values were higher in the pig (p<0.001). Absolute values of white cell count were higher in the pig, while normalized values diverged toward the end of the perfusion with an increase in the calf and a decrease in the pig (p<0.001). Free plasma Hb and LDH exhibited similar profiles in both groups. CONCLUSIONS: In the setting of prolonged perfusion, species type--bovine or porcine--has an impact on hematology profile, but not on hemolytic parameters. These findings should be taken into account when cardiopulmonary bypass components are tested.

Performance of a new implantable cardiac assist centrifugal pump.

The AB-180 is a new implantable centrifugal pump with a low volume dome (10 ml) and a local heparin delivery system which avoids systemic heparinization. This study focuses on its hemodynamic performance. We analyzed 3 anesthetized calves (71.0 +/- 2.5 kg), equipped with arterial pressure (AP), and Swan-Ganz and left atrial pressure (LAP) catheters. The AB-180 pump was installed through a left thoracotomy, with a transmitral left ventricular (LV) inflow cannula inserted via the left appendage and an outflow tract sutured to the descending aorta. LAP, AP, and blood flow across the pump were recorded for various pump speed and in different preload conditions (right atrial pressure = 4, 7, and 10 mm Hg, respectively). The pump significantly unloaded the left heart cavities and was able to increase the mean AP. For an RAP of 10 mm Hg, running the pump at 4,500 rpm decreased the LAP from 11.0 +/- 0.8 mm Hg to 3.0 +/- 0.8 mm Hg (p < 0.001) and augmented the mean AP from 48.2 +/- 6.4 mm Hg to 80.8 +/- 12.1 mm Hg (p < 0.001). A maximal pump flow of 5.6 +/- 0.2 L/min was obtained under these conditions. In addition to the advantage of its particular design, the AB-180 can be considered as an efficient left ventricular assist device (LVAD). It significantly unloads the left heart cavities and ensures efficient systemic AP and blood flow.

Assembly of the Heparin Removal Device for patients with suspected adverse reaction to protamine sulphate.

Protamine sulphate is routinely used after cardiopulmonary bypass (CPB) to restore the patient's baseline coagulatory state. However, adverse reactions are encountered, and alternative means to neutralize heparin are, therefore, necessary. The Heparin Removal Device (HRD) constitutes an extracorporeal circuit that allows ex vivo deheparinization by mean of a polycationic ligand that binds heparin molecules. This paper presents the setup of the HRD circuit. It is illustrated by the report of a 68-year-old man with a known severe crustacean allergy. The patient (78 kg, 170 cm) was admitted for elective coronary artery bypass graft surgery. It was decided that the HRD would be used as a precaution in order to avoid the risks of using protamine sulphate. The CPB time and aortic crossclamp time were 70 and 40 min, respectively. At the end of CPB, the device was inserted and processing started. Activated coagulation time values were monitored over a 130 min period and diminished from 480 to 300 s after 45 min, 220 s after 90 min, and settled at 150 s. Haemostasis was acceptable and processing stopped. The operation was terminated and the patient transferred to the intensive care unit. Clinical evolution was excellent, with minimal postoperative bleeding. The HRD presents an alternative to protamine sulphate when this drug is contraindicated for a certain patient population who might have a suspected, known or emergency adverse reaction.

Hemoglobin substitute and cardiopulmonary bypass.

The effects of diaspirin crosslinked hemoglobin (DCLHb, Baxter Health Care Corp., Round Lake, IL) on oxygen exchange in the setting of cardiopulmonary bypass (CPB) are unknown. Six calves (71.2 +/- 1.3 kg) were connected to CPB by jugular venous and carotid arterial cannulation for 5 hours. Each 1 hour period included 45 min of partial CPB (mean flow rate of 50 ml/kg per min) followed by 15 min without CPB, at the end of which 500 ml of blood were substituted for with either 500 ml of hydroxyethyl starch (Haes; n = 3) or 500 ml of DCLHb (n = 3). A total of 2 liters of blood was, thus, exchanged (28 ml/kg of blood substitute). Values are expressed as mean +/- 1 SD. Analysis of variance for repeated measurements was used. The cardiac output (CO) values at 1 h, 3 h, and 5 h were in the Haes group: 5.7 +/- 2, 6.7 +/- 2.5, and 7.7 +/- 2.5L/min, and in the DCLHb group: 5.7 +/- 0.6, 4 +/- 1, and 4.7 +/- 1.2 L/min, respectively. The arteriovenous oxygen content difference (Ca-Cvo2) values at 1 h, 3 h, and 5 h were in the Haes group: 4.6 +/- 1, 3.3 +/- 1.5, and 3.5 +/- 1.5 ml/dl, and in the DCLHb group: 4.9 +/- 0.6, 7.4 +/- 0.7, and 6.6 +/- 0.6 ml/dl, respectively. The oxygen consumption (Vo2) values at 1 h, 3 h, and 5 h were in the Haes group: 244 +/- 29, 198 +/- 58, and 249 +/- 42 ml/min, and in the DCLHb group: 273 +/- 28, 296 +/- 75, and 306 +/- 65 ml/min, respectively. CO and Ca-Cvo2 showed a significant difference (p < 0.01), whereas Vo2 did not (p = 0.52). In the DCLHb group of this CPB animal model, the cardiac output is lower and the arteriovenous oxygen content difference higher than in the Haes group, allowing for preserved oxygen consumption.

Blood profile during and after hemoglobin substitute administration.

The in vivo effects of Diaspirin Crosslinked Hemoglobin (DCLHb, Baxter Healthcare Corp.) on hematology and biochemistry are unknown. This study includes 6 calves (71.2+/-1.3 kg). In each animal a total of 2 litres of blood was exchanged for the same amount of hydroxylethyl starch (Haes, Fresenius) (n=3) or DCLHb (n=3), which is equivalent to 28cc/kg of blood substitute, over a period of 5 hours. The animals were allowed to survive 7 days. Blood samples were taken hourly during the perfusion protocol, at postoperative day (POD) 1, 2 and 7. ANOVA test was used for repeated measurements. Blood cell profiles were similar in both groups. Peak methemoglobinemia was 4.2% in the DCLHb group. Osmolarity was significantly higher in the DCLHb group with the greatest difference at POD 1 and 2. Postmortem analysis of the major organs did not show any sign of hemoglobin deposit in the DCLHb group. In the given setup DCLHb can be administered in a large quantity with good hematological tolerance and without any deposits in major organs. A prolonged plasma expander effect was observed.

A siliconized hollow fiber membrane oxygenator.

Most membrane oxygenators are built with microporous fibers known for plasma leakage in long-term use such as extracorporeal life support or extracorporeal membrane oxygenation. The current study was designed to evaluate the Quadrox oxygenator in which the fibers have been coated with silicone (Jostra). Six calves (mean weight, 62 +/- 4 kg) were connected to cardiopulmonary bypass (CPB) by jugular venous and carotid arterial cannulation, with a mean flow rate of 3 L/min for 6 hours. They were randomly assigned to a standard Quadrox oxygenator (standard group, n = 3) or a siliconized Quadrox oxygenator (silicone group, n = 3). After 7 days, the animals were sacrificed. A standard battery of blood samples was taken before bypass, after mixing for 10 minutes, and after 1, 2, 5, and 6 hours of perfusion. Analysis of variance was used for repeated measurements. Total oxygen transfer and carbon dioxide transfer did not differ between groups (p = 0.5 for comparison). Blood trauma, evaluated by plasma hemoglobin (Hb), did not detect any significant hemolysis in either group. Thrombocyte and white blood cell count profiles in both groups were parallel and without significant differences (p = 0.1 and 0.6, respectively). At the end of testing no clot deposition was found in the oxygenator. At postmortem, there were no signs of peripheral emboli. The results of this study suggest that this silicone coating of hollow fibers allows for good gas transfer, while preserving all the mechanical advantages of a conventional hollow fiber oxygenator.

Impact of hollow-fiber membrane surface area on oxygenator performance: Dideco D903 Avant versus a prototype with larger surface area.

This study compares the gas transfer capacity, the blood trauma, and the blood path resistance of the hollow-fiber membrane oxygenator Dideco D 903 with a surface area of 1.7 m2 (oxygenator 1.7) versus a prototype built on the same principles but with a surface area of 2 m2 (oxygenator 2). Six calves (mean body weight: 68.2 +/- 3.2 kg) were connected to cardiopulmonary bypass (CPB) by jugular venous and carotid arterial cannulation, with a mean flow rate of 4 l/min for 6 h. They were randomly assigned to oxygenator 1.7 (N = 3) or 2 (N = 3). After 7 days, the animals were sacrificed. A standard battery of blood samples was taken before the bypass, throughout the bypass, and 24 h, 48 h, and 7 days after the bypass. The oxygenator 2 group showed significantly better total oxygen and carbon dioxide transfer values throughout the perfusion (p < .001 for both comparison). Hemolytic parameters (lactate dehydrogenase and free plasma hemoglobin) exhibited a slight but significant increase after 5 h of bypass in the oxygenator 1.7 group. The pressure drop through the oxygenator was low in both groups (range, 43-74 mmHg). With this type of hollow-fiber membrane oxygenator, an increased surface of gas exchange from 1.7 m2 to 2 m2 improves gas transfer, with a limited impact on blood trauma and no increase of blood path resistance.

Optimization of the pump driven venous return for minimally invasive open heart surgery.

Blood return into the cardiotomy reservoir is usually reduced when a cardiopulmonary bypass (CPB) is initiated through a peripheral access, even if the tip of the venous cannula is pushed into the right atrium. A centrifugal pump can be placed on the venous line to increase the negative pressure. Surgery involving the right atrium requires selective cannulation of both vena cavae. Because of the small diameter of the vena cava as compared to the right atrium, the benefit of the centrifugal pump may have limitations. We analyze the factors influencing the active venous return when the cannula is maintained into the vena cava. In 4 calves (83.0+/-14.9 Kg) a CPB was initiated through carotid and jugular access, with the tip of the venous cannula placed into the superior vena cava, before ventricular fibrillation was provoked. Venous drainage was progressively increased thanks to the centrifugal pump. Considering the negative pressure induced on the venous line, we analyzed the performance expressed in l/min of blood drained, of four one stage cannulae ("lighthouse" tip 24F, 28F or 32F, and percutaneous 28F). The performance of all cannulae were highly dependent on the central venous pressure (CVP) with better drainage for higher CVP. The size and type of cannula also significantly affected blood drainage. Active drainage was best with the percutaneous 28F cannula. This cannula was specially attractive at low CVP conditions.

Ex vivo testing of the Quart arterial line filter.

Arterial line filters are now routinely used in cardiac surgery in order to decrease the microemboli load to the patient. The Quart filter (Jostra, Hirrlingen, Germany) with a new planar construction design, an easy de-airing system and an integrated bypass, was tested for air filtration capacity and resistance to blood path in a standardized setting with surviving animals. Three calves (mean body weight: 71+/-3.4 kg) were connected to a standard cardiopulmonary bypass (CPB) circuit by jugular venous and carotid arterial cannulation with a mean flow rate of 3.5 l/min. The arterial line filter was challenged with upstream injections of boluses of air of 5, 10 and 15 ml, respectively. A Doppler ultrasound was positioned downstream on the arterial line to measure bubble count and size. The pressure drop through the filter was monitored at flow rates of between 1 and 6 l/min. At the end of the procedure the animals were weaned from the CPB and, thereafter, from the ventilator. After 7 days, the animals were sacrificed electively. This study shows that important quantities of air can be injected into the arterial line upstream of the filter with small volumes of small sized bubbles recorded downstream. With the 5 ml air bolus injection, mean values of 0.3+/-0.6 bubbles of 30 and 40 microm were detected, whereas with the 20 ml bolus, 32.6+/-8.7 bubbles of 10 microm, 3.7+/-1.1 bubbles of 30 microm, 3.3+/-0.6 bubbles of 40 microm and 0.7+/-1.1 bubbles of 50 microm were recorded. The blood path resistance at different blood flow rates was well within the acceptable range with a pressure drop of 20+/-0 and 26.6+/-5.7 mmHg at flow rates of 4 and 5 l/min, respectively. With its planar concept, the Quart filter offers good air filtering capacity both in terms of bubble count and size after injection of large boluses of air, without any increase of resistance to the blood path. Moreover, it offers a venting function and an integrated bypass system.

Augmented venous return for minimally invasive open heart surgery with selective caval cannulation.

OBJECTIVE: Minimally invasive open heart surgery involves limited intrathoracic cannulation sites necessitating cardiopulmonary bypass to be initiated via peripheral access using percutaneous cannulae with the tip placed into the right atrial cavity. However, surgery involving the opening of the right heart obliges the surgeon to maintain the end of the cannulae into the vena cavae. The impeded venous return due to the smaller diameter may be alleviated by inserting a centrifugal pump in the venous line. METHODS: Right anterior mini-thoracotomy and exposure of the femoral site were performed before the patient was heparinized. Cannulation of the femoral artery, the inferior vena cava via the femoral vein and the superior vena cava through the mini-thoracotomy was performed and cardiopulmonary bypass was initiated. Venous drainage was augmented with the centrifugal pump. Cardiac arrest was provoked and both vena cavae were snared before performing the intracardiac procedure. RESULTS: Twenty consecutive patients were operated on using this technique (15 males/five females; age: 44.8 +/- 14.3 years; bodyweight: 73.5 +/- 15.1 kg; body surface area: 1.8 +/- 0.2 m2; theoretical blood flow rate: 4.4 +/- 0.5 l/min). The cannula sizes were 21.9 +/- 2.2 Fr for the femoral artery, 26.5 +/- 1.7 Fr for the inferior vena cava and 23.8 +/- 2.5 Fr for the superior vena cava. Venous drainage through the single inferior vena cava cannula was 2.1 +/- 0.6 l/min (48.8 +/- 13.3% of the theoretical flow). Adding the superior vena cava cannula increased the venous flow to 3.1 +/- 0.4 l/min (70.7 +/- 9.6% of the theoretical value, P < 0.005). The use of the centrifugal pump increased the flow to 4.1 +/- 0.6 l/min (93.4 +/- 8.9% of the theoretical flow, P < 0.001) with a mean inlet negative pressure of -69 +/- 10.2 mmHg. The mean bypass time was 64.0 +/- 24.6 min for a mean operative time of 226.3 +/- 61.0 min. Minimum venous saturation was 69.4 +/- 8.5%. CONCLUSIONS: Despite the smaller diameter of the vena cavae compared to the right atrium, and a smaller internal diameter of percutaneous cardiopulmonary bypass cannulae compared to classic ones; the centrifugal pump improves the venous drainage significantly so that minimally invasive open heart procedures can be performed under optimal and safe perfusion conditions.

Impact of a remote pump head on neonatal priming volumes.

Reduction of priming volumes of the cardiopulmonary bypass (CPB) circuit in neonatal cardiac surgery to decrease haemodilution and blood transfusion requirements can be achieved with the use of neonatal low prime oxygenators and smaller diameter tubing. We have further reduced our prime volume with the use of a custom-designed arm allowing for remote positioning of a double-headed roller pump. This arm enables the double pump to be placed alongside the main heart-lung machine close to the operating table, and to position the pump inlet and outlet tubing immediately at the reservoir outlet and oxygenator inlet, respectively, therefore reducing tubing lengths. Priming volumes of four cases using this configuration were compared to four cases using our standard neonatal bypass setup. Results showed a 29% decrease in priming volume and a 58% reduction in blood utilization during CPB. This reduction in priming volume is clinically significant as it lowers the ratio of priming volume to patient blood volume and reduces homologous blood requirements.

Heparin removal after cardiopulmonary bypass in a patient with adverse reaction to protamine.

A 74-year-old man underwent elective coronary surgery under cardiopulmonary bypass. A few minutes after the protamine administration was started, he suddenly developed a severe hypotension necessitating cardiac massage and recannulation for pump assistance. A further test dose of protamine provoked an identical reaction. We installed a Heparin Removal Device, which allows for ex-vivo deheparinization. In 35 minutes ACT decreased from 480 sec to 180 sec and clots appeared in the operating field. This system provides an excellent alternative to protamine in patients with an adverse reaction to protamine.