To limit the morbidity of cardiopulmonary bypass (CPB), a new concept of integrating pumping, oxy... more To limit the morbidity of cardiopulmonary bypass (CPB), a new concept of integrating pumping, oxygenation, and air removal into a single unit has been developed (CardioVention Inc., Santa Clara, CA). The air filtration capacity of this system was tested. Three calves (73.2 +/- 2 kg) were connected to the integrated system by jugular and carotid cannulation. The integrated unit was challenged with injections of boluses of air of 5, 10, and 20 ml, three times each, and for a blood flow of 3 L/min and 5 L/min, respectively. The bubble count and size were recorded downstream of the unit with a Doppler ultrasound. At 3 L/min, bubbles were detected after injections of 20 ml only (n = 7 for the nine boluses). At 5 L/min, 1 bubble was detected with the nine injections of 5 ml, 14 bubbles were detected with nine injections of 10 ml, and 25 bubbles were detected with nine injections of 20 ml. No bubble exceeded 40 microm in diameter as determined by the Doppler ultrasound. The air filtering capacity of the CardioVention system is excellent both in terms of bubble count and of size after injection of large boluses of air. Its integrated concept offers a simplification of the circuit with fewer devices and connections, which further reduces the risk of accidental air introduction.
Trillium coating (Medtronic Inc., Minneapolis, MN) offers, in addition to the presence of heparin... more Trillium coating (Medtronic Inc., Minneapolis, MN) offers, in addition to the presence of heparin, endothelium-like properties of its negatively charged surface. Its thromboresistant properties on coated connectors are tested here and compared with uncoated standard connectors, as well as with the Carmeda BioActive surface (CBAS) heparin surface coating. A partial cardiopulmonary bypass bovine model (body weight 68 +/- 5 kg) was selected, and the surfaces were exposed to the blood stream (pump flow 3.5 L/min) for up to 350 minutes without systemic heparinization. Thereafter, another set of samples was exposed to stagnant blood for 20 minutes. Besides hemodynamic, hematologic, and biochemical analyses, the macroscopic appearance of 45 blood exposed surface samples were graded semiquantitatively on a scale of 0 to 10: no macroscopic deposits = grade 0, one spot (1 mm diameter) = grade 1, two spots = grade 2, five or more spots = grade 5, 10% of the surface covered with clots = grade 6, 100% covered = grade 10. When exposed to blood flow, Trillium and CBAS coatings showed a statistically significant (p = 0.03) better thromboresistance (score: 0 +/- 0 for both) than uncoated connectors (score: 0.8 +/- 1.5) in this nonheparinized model. The same holds true when the connectors were exposed to stagnant blood (score: 0 +/- 0 for both coatings vs 4.3 +/- 2.8 for controls; p = 0.03). Therefore, Trillium coating exhibits significant antithrombotic properties that outperform standards for connectors used in clinical perfusion.
Most membrane oxygenators are built with microporous fibers known for plasma leakage in long-term... more 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.
To limit the morbidity of cardiopulmonary bypass (CPB), a new concept of integrating pumping, oxy... more To limit the morbidity of cardiopulmonary bypass (CPB), a new concept of integrating pumping, oxygenation, and air removal into a single unit has been developed (CardioVention Inc., Santa Clara, CA). The air filtration capacity of this system was tested. Three calves (73.2 +/- 2 kg) were connected to the integrated system by jugular and carotid cannulation. The integrated unit was challenged with injections of boluses of air of 5, 10, and 20 ml, three times each, and for a blood flow of 3 L/min and 5 L/min, respectively. The bubble count and size were recorded downstream of the unit with a Doppler ultrasound. At 3 L/min, bubbles were detected after injections of 20 ml only (n = 7 for the nine boluses). At 5 L/min, 1 bubble was detected with the nine injections of 5 ml, 14 bubbles were detected with nine injections of 10 ml, and 25 bubbles were detected with nine injections of 20 ml. No bubble exceeded 40 microm in diameter as determined by the Doppler ultrasound. The air filtering capacity of the CardioVention system is excellent both in terms of bubble count and of size after injection of large boluses of air. Its integrated concept offers a simplification of the circuit with fewer devices and connections, which further reduces the risk of accidental air introduction.
New peripheral venous cannulae have recently been proposed for minimally invasive open cardiac su... more 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.
Peripheral access cardiopulmonary bypass (CPB) is initiated with percutaneous cannulae (CTRL) and... more 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.
The Journal of Extra Corporeal Technology, Sep 1, 2000
This study compares the gas transfer capacity, the blood trauma, and the blood path resistance of... more 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.
It has been suggested that the shape of the normalized time-varying elastance curve, E n (t n ), ... more It has been suggested that the shape of the normalized time-varying elastance curve, E n (t n ), is conserved in different cardiac pathologies. We hypothesize, however, that the E n (t n ) differs quantitatively after myocardial infarction (MI).
Objective: Transthoracic echocardiography (TTE) has been used clinically to disobstruct venous dr... more Objective: Transthoracic echocardiography (TTE) has been used clinically to disobstruct venous drainage cannula and to optimise placement of venous cannulae in the vena cava but it has never been used to evaluate performance capabilities. Also, little progress has been made in venous cannula design in order to optimise venous return to the heart lung machine. We designed a self-expandable Smartcanula 1 (SC) and analysed its performance capability using echocardiography. Methods: An epicardial echocardiography probe was placed over the SC or control cannula (CTRL) and a Doppler image was obtained. Mean (V m ) and maximum (V max ) velocities, flow and diameter were obtained. Also, pressure drop (DP CPB ) was obtained between the central venous pressure and inlet to venous reservoir. LDH and Free Hb were also compared in 30 patients. Comparison was made between the two groups using the student's t-test with statistical significance established when p < 0.05. Results: Age for the SC and CC groups were 61.6 AE 17.6 years and 64.6 AE 13.1 years, respectively. Weight was 70.3 AE 11.6 kg and 72.8 AE 14.4 kg, respectively. BSA was 1.80 AE 0.2 m 2 and 1.82 AE 0.2 m 2 , respectively. CPB times were 114 AE 53 min and 108 AE 44 min, respectively. Cross-clamp time was 59 AE 15 min and 76 AE 29 min, respectively ( p = NS). Free-Hb was 568 AE 142 U/l versus 549 AE 271U/l post-CPB for the SC and CC, respectively ( p = NS). LDH was 335 AE 73 mg/l versus 354 AE 116 mg/l for the SC and CC, respectively ( p = NS). V m was 89 AE 10cm/s (SC) versus 63 AE 3 cm/s (CC), V max was 139 AE 23 cm/s (SC) versus 93 AE 11 cm/s (CC) (both p < 0.01). DP CPB was 30 AE 10 mmHg (SC) versus 43 AE 13 mmHg (CC) ( p < 0.05). A Bland-Altman test showed good agreement between the two devices used concerning flow rate calculations between CPB and TTE (bias 300 ml AE 700 ml standard deviation). Conclusions: This novel Smartcanula design, due to its self-expanding principle, provides superior flow characteristics compared to classic two stage venous cannula used for adult CPB surgery. No detrimental effects were observed concerning blood damage. Echocardiography was effective in analysing venous cannula performance and velocity patterns. #
To date, there is no quality assurance program that correlates patient outcome to perfusion servi... more To date, there is no quality assurance program that correlates patient outcome to perfusion service provided during cardiopulmonary bypass (CPB). A score was devised, incorporating objective parameters that would reflect the likelihood to influence patient outcome. The purpose was to create a new method for evaluating the quality of care the perfusionist provides during CPB procedures and to deduce whether it predicts patient morbidity and mortality. We analysed 295 consecutive elective patients. We chose 10 parameters: fluid balance, blood transfused, Hct, ACT, PaO2, PaCO2, pH, BE, potassium and CPB time. Distribution analysis was performed using the Shapiro-Wilcoxon test. This made up the PerfSCORE and we tried to find a correlation to mortality rate, patient stay in the ICU and length of mechanical ventilation. Univariate analysis (UA) using linear regression was established for each parameter. Statistical significance was established when p < 0.05. Multivariate analysis (MA) ...
Interactive cardiovascular and thoracic surgery, 2006
To assess the performance of 45F vs. 36F smartcanula in CPB with gravity drainage alone. Twenty p... more To assess the performance of 45F vs. 36F smartcanula in CPB with gravity drainage alone. Twenty patients were randomly assigned to two groups receiving for venous drainage a smartcanula which is collapsed over a mandrel for trans-atrial insertion into the inferior vena cava and expanded in situ to either 45F or 36F. Valve replacement/repair was realized in 7/10 and/or CABG in 6/10 for 36F (69+/-13 years) vs. 5/10 and 5/10, respectively, for 45F (63+/-11 years: NS). Body weight and surface area (BSA) were 83+/-9 kg (1.9+/-0.2 m2, max 2.2 m2) for 36F vs. 79+/-6 kg: NS (1.9+/-0.1 m2 (NS), max 2.1 m2) for 45F. Insertion and access orifice diameter (area) was 6 mm and 10 mm (78.5 mm2) for the 36F vs. 6 mm and 13 mm (132 mm2) for the 45F (+69%). Calculated target pump flow (2.4 l/min/m2) was 4.7+/-0.4 l/min for 36F vs. 4.5+/-0.3 l/min for 45F. Achieved pump flow accounted for 5.0+/-0.3 l/min for 36F (8% above target) vs. 4.8+/-0.3 l/min for 45F (8% above target): NS. The water balance dur...
Vacuum-assist venous drainage (VAVD) can increase venous blood return during cardiopulmonary bypa... more Vacuum-assist venous drainage (VAVD) can increase venous blood return during cardiopulmonary bypass (CPB) procedures. However, the negative pressure created in the closed cardiotomy reservoir can be transmitted to the oxygenator if a nonocclusive or centrifugal arterial pump is used, resulting in bubble transgression (BT) from the gas to blood compartment of the oxygenator. We analyzed the vacuum pressure required to produce BT using an in vitro circuit including successively a closed reservoir, a pump (centrifugal or roller), and an oxygenator. A constant hydrostatic pressure was maintained onto the oxygenator. Vacuum was applied on the cardiotomy reservoir, progressively increasing negative pressure from 0 to -80 mmHg and monitoring BT with a bubble detector. Six different oxygenators were compared. A partially occlusive roller pump and a centrifugal pump were compared to a control, which was without any pump. A mean negative pressure of -53 +/- 7 mmHg was necessary to produce BT ...
The mechanical cardiac assistance, once limited only to the adult patients, is now progressively ... more The mechanical cardiac assistance, once limited only to the adult patients, is now progressively extended to the paediatric population, including neonates. Currently for children with cardiorespiratory insufficiency requiring for a mechanical assistance there are available several options: Intra-Aortic Balloon Pump, Extra-Corporeal Membrane Oxygenation (ECMO) et le Ventricular Assist Device. From April 1999 in our Department of Cardiovascular Surgery at CHUV 8 children, including 4 neonates, have been treated with ECMO. Indications, contra-indications, advantages, disadvantages, results and complications of the available options of paediatric mechanical cardiac assistance are described.
Reduction of priming volumes of the cardiopulmonary bypass (CPB) circuit in neonatal cardiac surg... more 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.
During cardiopulmonary bypass (CPB), venous drainage may be impeded due to small vessel and cannu... more During cardiopulmonary bypass (CPB), venous drainage may be impeded due to small vessel and cannula size or chattering, thus, blood return to the heart-lung machine is reduced. We designed a self-expandable prototype cannula, which is able to maintain the vein open and overcome this problem and analysed its performance capability. This prototype and several other cannulae were tested using an access vessel diameter of 7 mm. An in vitro circuit was set up with a 10 mm penrose latex tube simulating the patient&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s vein placed between the patient preload reservoir and the cannula, encasing the cannula&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s inlet(s). Maximum flow rate was determined for passive venous drainage (PVD) at preloads (P) of 2 and 4 mmHg. We compared these results to three classic single-stage venous cannulae: basket tip, thoracic drain and percutaneous tip. By comparing the other cannulae to the prototype, under PVD conditions and a central venous pressure (CVP) of 2 mmHg, the prototype cannula&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s flow rate (1.32 +/- 0.04 L/min) outperformed the basket type (the best performing comparator) (1.02 +/- 0.08 L/min) by 23% (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.005). When the preload was increased to 4 mmHg under PVD conditions, the same trend was noted with the prototype cannula (1.65 +/- 0.05 L/min), outperforming the basket cannula&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s value (1.26 +/- 0.05 L/min) by 24% (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). This new cannula design provides superior flow characteristics, under all test conditions, compared to the classic single-stage venous cannulae used for paediatric CPB surgery.
To limit the morbidity of cardiopulmonary bypass (CPB), a new concept of integrating pumping, oxy... more To limit the morbidity of cardiopulmonary bypass (CPB), a new concept of integrating pumping, oxygenation, and air removal into a single unit has been developed (CardioVention Inc., Santa Clara, CA). The air filtration capacity of this system was tested. Three calves (73.2 +/- 2 kg) were connected to the integrated system by jugular and carotid cannulation. The integrated unit was challenged with injections of boluses of air of 5, 10, and 20 ml, three times each, and for a blood flow of 3 L/min and 5 L/min, respectively. The bubble count and size were recorded downstream of the unit with a Doppler ultrasound. At 3 L/min, bubbles were detected after injections of 20 ml only (n = 7 for the nine boluses). At 5 L/min, 1 bubble was detected with the nine injections of 5 ml, 14 bubbles were detected with nine injections of 10 ml, and 25 bubbles were detected with nine injections of 20 ml. No bubble exceeded 40 microm in diameter as determined by the Doppler ultrasound. The air filtering capacity of the CardioVention system is excellent both in terms of bubble count and of size after injection of large boluses of air. Its integrated concept offers a simplification of the circuit with fewer devices and connections, which further reduces the risk of accidental air introduction.
Trillium coating (Medtronic Inc., Minneapolis, MN) offers, in addition to the presence of heparin... more Trillium coating (Medtronic Inc., Minneapolis, MN) offers, in addition to the presence of heparin, endothelium-like properties of its negatively charged surface. Its thromboresistant properties on coated connectors are tested here and compared with uncoated standard connectors, as well as with the Carmeda BioActive surface (CBAS) heparin surface coating. A partial cardiopulmonary bypass bovine model (body weight 68 +/- 5 kg) was selected, and the surfaces were exposed to the blood stream (pump flow 3.5 L/min) for up to 350 minutes without systemic heparinization. Thereafter, another set of samples was exposed to stagnant blood for 20 minutes. Besides hemodynamic, hematologic, and biochemical analyses, the macroscopic appearance of 45 blood exposed surface samples were graded semiquantitatively on a scale of 0 to 10: no macroscopic deposits = grade 0, one spot (1 mm diameter) = grade 1, two spots = grade 2, five or more spots = grade 5, 10% of the surface covered with clots = grade 6, 100% covered = grade 10. When exposed to blood flow, Trillium and CBAS coatings showed a statistically significant (p = 0.03) better thromboresistance (score: 0 +/- 0 for both) than uncoated connectors (score: 0.8 +/- 1.5) in this nonheparinized model. The same holds true when the connectors were exposed to stagnant blood (score: 0 +/- 0 for both coatings vs 4.3 +/- 2.8 for controls; p = 0.03). Therefore, Trillium coating exhibits significant antithrombotic properties that outperform standards for connectors used in clinical perfusion.
Most membrane oxygenators are built with microporous fibers known for plasma leakage in long-term... more 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.
To limit the morbidity of cardiopulmonary bypass (CPB), a new concept of integrating pumping, oxy... more To limit the morbidity of cardiopulmonary bypass (CPB), a new concept of integrating pumping, oxygenation, and air removal into a single unit has been developed (CardioVention Inc., Santa Clara, CA). The air filtration capacity of this system was tested. Three calves (73.2 +/- 2 kg) were connected to the integrated system by jugular and carotid cannulation. The integrated unit was challenged with injections of boluses of air of 5, 10, and 20 ml, three times each, and for a blood flow of 3 L/min and 5 L/min, respectively. The bubble count and size were recorded downstream of the unit with a Doppler ultrasound. At 3 L/min, bubbles were detected after injections of 20 ml only (n = 7 for the nine boluses). At 5 L/min, 1 bubble was detected with the nine injections of 5 ml, 14 bubbles were detected with nine injections of 10 ml, and 25 bubbles were detected with nine injections of 20 ml. No bubble exceeded 40 microm in diameter as determined by the Doppler ultrasound. The air filtering capacity of the CardioVention system is excellent both in terms of bubble count and of size after injection of large boluses of air. Its integrated concept offers a simplification of the circuit with fewer devices and connections, which further reduces the risk of accidental air introduction.
New peripheral venous cannulae have recently been proposed for minimally invasive open cardiac su... more 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.
Peripheral access cardiopulmonary bypass (CPB) is initiated with percutaneous cannulae (CTRL) and... more 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&amp;amp;#39;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.
The Journal of Extra Corporeal Technology, Sep 1, 2000
This study compares the gas transfer capacity, the blood trauma, and the blood path resistance of... more 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 &lt; .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.
It has been suggested that the shape of the normalized time-varying elastance curve, E n (t n ), ... more It has been suggested that the shape of the normalized time-varying elastance curve, E n (t n ), is conserved in different cardiac pathologies. We hypothesize, however, that the E n (t n ) differs quantitatively after myocardial infarction (MI).
Objective: Transthoracic echocardiography (TTE) has been used clinically to disobstruct venous dr... more Objective: Transthoracic echocardiography (TTE) has been used clinically to disobstruct venous drainage cannula and to optimise placement of venous cannulae in the vena cava but it has never been used to evaluate performance capabilities. Also, little progress has been made in venous cannula design in order to optimise venous return to the heart lung machine. We designed a self-expandable Smartcanula 1 (SC) and analysed its performance capability using echocardiography. Methods: An epicardial echocardiography probe was placed over the SC or control cannula (CTRL) and a Doppler image was obtained. Mean (V m ) and maximum (V max ) velocities, flow and diameter were obtained. Also, pressure drop (DP CPB ) was obtained between the central venous pressure and inlet to venous reservoir. LDH and Free Hb were also compared in 30 patients. Comparison was made between the two groups using the student's t-test with statistical significance established when p < 0.05. Results: Age for the SC and CC groups were 61.6 AE 17.6 years and 64.6 AE 13.1 years, respectively. Weight was 70.3 AE 11.6 kg and 72.8 AE 14.4 kg, respectively. BSA was 1.80 AE 0.2 m 2 and 1.82 AE 0.2 m 2 , respectively. CPB times were 114 AE 53 min and 108 AE 44 min, respectively. Cross-clamp time was 59 AE 15 min and 76 AE 29 min, respectively ( p = NS). Free-Hb was 568 AE 142 U/l versus 549 AE 271U/l post-CPB for the SC and CC, respectively ( p = NS). LDH was 335 AE 73 mg/l versus 354 AE 116 mg/l for the SC and CC, respectively ( p = NS). V m was 89 AE 10cm/s (SC) versus 63 AE 3 cm/s (CC), V max was 139 AE 23 cm/s (SC) versus 93 AE 11 cm/s (CC) (both p < 0.01). DP CPB was 30 AE 10 mmHg (SC) versus 43 AE 13 mmHg (CC) ( p < 0.05). A Bland-Altman test showed good agreement between the two devices used concerning flow rate calculations between CPB and TTE (bias 300 ml AE 700 ml standard deviation). Conclusions: This novel Smartcanula design, due to its self-expanding principle, provides superior flow characteristics compared to classic two stage venous cannula used for adult CPB surgery. No detrimental effects were observed concerning blood damage. Echocardiography was effective in analysing venous cannula performance and velocity patterns. #
To date, there is no quality assurance program that correlates patient outcome to perfusion servi... more To date, there is no quality assurance program that correlates patient outcome to perfusion service provided during cardiopulmonary bypass (CPB). A score was devised, incorporating objective parameters that would reflect the likelihood to influence patient outcome. The purpose was to create a new method for evaluating the quality of care the perfusionist provides during CPB procedures and to deduce whether it predicts patient morbidity and mortality. We analysed 295 consecutive elective patients. We chose 10 parameters: fluid balance, blood transfused, Hct, ACT, PaO2, PaCO2, pH, BE, potassium and CPB time. Distribution analysis was performed using the Shapiro-Wilcoxon test. This made up the PerfSCORE and we tried to find a correlation to mortality rate, patient stay in the ICU and length of mechanical ventilation. Univariate analysis (UA) using linear regression was established for each parameter. Statistical significance was established when p < 0.05. Multivariate analysis (MA) ...
Interactive cardiovascular and thoracic surgery, 2006
To assess the performance of 45F vs. 36F smartcanula in CPB with gravity drainage alone. Twenty p... more To assess the performance of 45F vs. 36F smartcanula in CPB with gravity drainage alone. Twenty patients were randomly assigned to two groups receiving for venous drainage a smartcanula which is collapsed over a mandrel for trans-atrial insertion into the inferior vena cava and expanded in situ to either 45F or 36F. Valve replacement/repair was realized in 7/10 and/or CABG in 6/10 for 36F (69+/-13 years) vs. 5/10 and 5/10, respectively, for 45F (63+/-11 years: NS). Body weight and surface area (BSA) were 83+/-9 kg (1.9+/-0.2 m2, max 2.2 m2) for 36F vs. 79+/-6 kg: NS (1.9+/-0.1 m2 (NS), max 2.1 m2) for 45F. Insertion and access orifice diameter (area) was 6 mm and 10 mm (78.5 mm2) for the 36F vs. 6 mm and 13 mm (132 mm2) for the 45F (+69%). Calculated target pump flow (2.4 l/min/m2) was 4.7+/-0.4 l/min for 36F vs. 4.5+/-0.3 l/min for 45F. Achieved pump flow accounted for 5.0+/-0.3 l/min for 36F (8% above target) vs. 4.8+/-0.3 l/min for 45F (8% above target): NS. The water balance dur...
Vacuum-assist venous drainage (VAVD) can increase venous blood return during cardiopulmonary bypa... more Vacuum-assist venous drainage (VAVD) can increase venous blood return during cardiopulmonary bypass (CPB) procedures. However, the negative pressure created in the closed cardiotomy reservoir can be transmitted to the oxygenator if a nonocclusive or centrifugal arterial pump is used, resulting in bubble transgression (BT) from the gas to blood compartment of the oxygenator. We analyzed the vacuum pressure required to produce BT using an in vitro circuit including successively a closed reservoir, a pump (centrifugal or roller), and an oxygenator. A constant hydrostatic pressure was maintained onto the oxygenator. Vacuum was applied on the cardiotomy reservoir, progressively increasing negative pressure from 0 to -80 mmHg and monitoring BT with a bubble detector. Six different oxygenators were compared. A partially occlusive roller pump and a centrifugal pump were compared to a control, which was without any pump. A mean negative pressure of -53 +/- 7 mmHg was necessary to produce BT ...
The mechanical cardiac assistance, once limited only to the adult patients, is now progressively ... more The mechanical cardiac assistance, once limited only to the adult patients, is now progressively extended to the paediatric population, including neonates. Currently for children with cardiorespiratory insufficiency requiring for a mechanical assistance there are available several options: Intra-Aortic Balloon Pump, Extra-Corporeal Membrane Oxygenation (ECMO) et le Ventricular Assist Device. From April 1999 in our Department of Cardiovascular Surgery at CHUV 8 children, including 4 neonates, have been treated with ECMO. Indications, contra-indications, advantages, disadvantages, results and complications of the available options of paediatric mechanical cardiac assistance are described.
Reduction of priming volumes of the cardiopulmonary bypass (CPB) circuit in neonatal cardiac surg... more 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.
During cardiopulmonary bypass (CPB), venous drainage may be impeded due to small vessel and cannu... more During cardiopulmonary bypass (CPB), venous drainage may be impeded due to small vessel and cannula size or chattering, thus, blood return to the heart-lung machine is reduced. We designed a self-expandable prototype cannula, which is able to maintain the vein open and overcome this problem and analysed its performance capability. This prototype and several other cannulae were tested using an access vessel diameter of 7 mm. An in vitro circuit was set up with a 10 mm penrose latex tube simulating the patient&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s vein placed between the patient preload reservoir and the cannula, encasing the cannula&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s inlet(s). Maximum flow rate was determined for passive venous drainage (PVD) at preloads (P) of 2 and 4 mmHg. We compared these results to three classic single-stage venous cannulae: basket tip, thoracic drain and percutaneous tip. By comparing the other cannulae to the prototype, under PVD conditions and a central venous pressure (CVP) of 2 mmHg, the prototype cannula&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s flow rate (1.32 +/- 0.04 L/min) outperformed the basket type (the best performing comparator) (1.02 +/- 0.08 L/min) by 23% (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.005). When the preload was increased to 4 mmHg under PVD conditions, the same trend was noted with the prototype cannula (1.65 +/- 0.05 L/min), outperforming the basket cannula&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s value (1.26 +/- 0.05 L/min) by 24% (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). This new cannula design provides superior flow characteristics, under all test conditions, compared to the classic single-stage venous cannulae used for paediatric CPB surgery.
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