Routine use of self-expanding venous cannulas for cardiopulmonary bypass: benefits and pitfalls in 100 consecutive cases

Objective: Assess the performance of self-expanding venous cannulas for routine use in open-heart surgery. Methods: Prospective study in 100 unselected consecutive patients undergoing open-heart surgery with either remote or central smart venous cannulation. Results: The study focuses on the 76 consecutive adult patients (mean age 59.2±17.3 years; 60 males, 16 females) undergoing surgical procedures with total cardiopulmonary bypass for either valve procedures (42/76 patients=55.3%), ascending aorta and arch repair (20/76 patients=26.3%), coronary artery revascularization (13/76 patients=17.1%) or other procedures (11/76 patients=14.5%) with 14/76 patients (18.4%) undergoing redo surgery and 6/76 patients (7.9%) undergoing small access surgery. The mean pump flow achieved by gravity drainage alone accounted for 5.0±0.6l/min (=114% of target) in the entire study population (n=76) as compared to the calculated, theoretical pump flow of 4.4±0.5l/min (p<0.0001). For the femoral cannulation sub-group (n=35) pump flow achieved by gravity drainage alone accounted for 4.9±0.6l/min (=114% of target) as compared to the calculated theoretical pump flow of 4.3±0.4l/min (p<0.0001). The corresponding numbers for trans-subclavian cannulation (n=7) are 5.2±0.5l/min (111%) for the pump flow achieved by gravity drainage as compared to the theoretical target flow of 4.7±0.4l/min. For the central cannulation sub-group (n=34) mean flow achieved by gravity drainage with a self-expanding venous cannula accounted for 5.1±0.7l/min (=116% of target) as compared to the calculated theoretical flow of 4.4±0.6l/min (p<0.0001). Conclusion: Full or more than target flow was achieved in 97% of the patients studied undergoing CPB with self-expanding venous cannulas and gravity drainage. Remote venous cannulation with self-expanding cannulas provides similar flows as central cannulation. Augmentation of venous return is no longer necessar

Superior flow for bridge to life with self-expanding venous cannulas

Background: Recently, a compact cardiopulmonary support (CPS) system designed for quick set-up for example, during emergency cannulation, has been introduced. Traditional rectilinear percutaneous cannulas are standard for remote vascular access with the original design. The present study was designed to assess the potential of performance increase by the introduction of next-generation, self-expanding venous cannulas, which can take advantage of the luminal width of the venous vasculature despite a relatively small access orifice. Methods: Veno-arterial bypass was established in three bovine experiments (69 ± 10 kg). The Lifebridge® (Lifebridge GmbH, Munich, Germany) system was connected to the right atrium in a trans-jugular fashion with various venous cannulas; and the oxygenated blood was returned through the carotid artery with a 17 F percutaneous cannula. Two different venous cannulas were studied, and the correlation between the centrifugal pump speed (1500-3900 RPM), flow and the required negative pressure on the venous side was established: (A) Biomedicus 19 F (Medtronic, Tolochenaz, Switzerland); (B) Smart canula 18 F/36 F (Smartcanula LLC, Lausanne, Switzerland). Results: At 1500 RPM, the blood flow was 0.44 ± 0.26 l min−1 for the 19 F rectilinear cannula versus 0.73 ± 0.34 l min−1 for the 18/36 F self-expanding cannula. At 2500 RPM the blood flow was 1.63 ± 0.62 l min−1 for the 19 F rectilinear cannula versus 2.13 ± 0.34 l min−1 for the 18/36 F self-expanding cannula. At 3500 RPM, the blood flow was 2.78 ± 0.47 l min−1 for the 19 F rectilinear cannula versus 3.64 ± 0.39 l min−1 for the 18/36 F self-expanding cannula (p ≪ 0.01 for 18/36 F vs 19 F). At 1500 RPM, the venous line pressure was 18 ± 8 mmHg for the 19 F rectilinear cannula versus 19 ± 5 mmHg for the 18/36 F self-expanding cannula. At 2500 RPM the venous line pressure accounted for −22 ± 32 mmHg for the 19 F rectilinear cannula versus 2 ± 5 mmHg for the 18/36 F self-expanding cannula. At 3500 RPM, the venous line pressure was −112 ± 42 mmHg for the rectilinear cannula versus 28 ± 7 mmHg for the 18/36 F self-expanding cannula (p ≪ 0.01 for 18 F/36 F vs 19 F). Conclusions: The negative pressure required to achieve adequate venous drainage with the self-expanding venous cannula accounts for approximately 31% of the pressure necessary with the 19 F rectilinear cannula. In addition, a pump flow of more than 4 l min−1 can be achieved with the self-expanding design and a well-accepted negative inlet pressure for minimal blood trauma of less than 50 mmH

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 −69.1±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 condition

Experimental Evaluation of the Medtronic Maxima Forte Hollow Fiber Membrane Oxygenator

A new hollow fiber membrane oxygenator, the Medtronic Maxima Forté, was tested for gas transfer, blood path resistance and blood handling characteristics in a standardized setting with surviving animals. Three calves (mean body weight: 71±9.6 kg) were placed on cardiopulmonary bypass at a mean flow rate of 50 ml/kg/min for six hours. The circuit included the Maxima Forté oxygenator. The animals were weaned from cardiopulmonary bypass and then from the ventilator. After seven days, the animals were sacrificed electively. Physiologic blood gas values could be maintained throughout perfusion in all animals. Mean pressure drop through the oxygenator varied between 49 mmHg and 66 mmHg. The respective baseline values for red blood cell count, white blood cell count and platelets were 8.90±1.26 106/mm3, 7.46±3.17 103/mm3 · and 680±216 l03/mm3. Red blood cell and platelet counts dropped slightly to 7.26±1.61 106/mm3 and 400±126 l03/mm3 at the end of the bypass, whereas the white blood cell count increased up to 9.13±5.25 103/mm3. All three cell lines returned to near their baseline values after seven days. Blood trauma evaluated as a function of plasma hemoglobin (plasma Hb) and lactate dehydrogenase (LDH) showed stable values during all the perfusion time. Both peaked at 24 hours before returning to their baseline values at seven days. LDH showed a statistically significant variation: 3255 ± 693 IU at 24 hours versus 2029 ± 287 IU at baseline (p = 0.04). The variation of plasma Hb was not statistically significant (93.5 ± 7.7 µmol/1 at 24 hours versus 77.3 ± 52.3 µmol/1 at baseline) indicating a weak effect of the perfusion on blood trauma. The Medtronic Maxima Forté hollow fiber membrane oxygenator offered good gas exchange capabilities, a low pressure drop, and low blood trauma over a prolonged perfusion time of six hours in this evaluation

Limitations Using the Vacuum-Assist Venous Drainage Technique During Cardiopulmonary Bypass Procedures

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 in all the oxygenators in the absence of a pump. The presence of a centrifugal pump between the reservoir and the oxygenator significantly increased the negative pressure required to produce BT compared to the control (−67 ± 7 mmHg, p −80 mmHg needed for BT), thus statistically significant when compared to the centrifugal pump (p < .05). The centrifugal pump offers significant resistance to BT but not as much compared to the roller pump, though BT cannot be prevented if the pump is turned off while the vacuum remains on the reservoir. Therefore, VAVD is a safe technique as long as the perfusionist stops the vacuum when the arterial pump is no longer in use

Comparing oxygen transfer performance between three membrane oxygenators: effect of temperature changes during cardiopulmonary bypass

Recently, a new oxygenator (Dideco 903 [D903], Dideco, Mirandola, Italy) has been introduced to the perfusion community, and we set about testing its oxygen transfer performance and then comparing it to two other models. This evaluation was based on the comparison between oxygen transfer slope, gas phase arterial oxygen gradients, degree of blood shunting, maximum oxygen transfer, and diffusing capacity calculated for each membrane. Sixty patients were randomized into three groups of oxygenators (Dideco 703 [D703], Dideco; D903; and Quadrox, Jostra Medizintechnik AG, Hirrlingen, Germany) including 40/20 M/F of 68.6 +/- 11.3 years old, with a body weight of 71.5 +/- 12.1 kg, a body surface area (BSA) of 1.84 +/- 0.3 m(2), and a theoretical blood flow rate (index 2.4 times BSA) of 4.4 +/- 0.7 L/min. The maximum oxygen transfer (VO(2)) values were 313 mL O(2)/min (D703), 579 mL O(2)/min (D903), and 400 mL O(2)/min (Quadrox), with the D903 being the most superior (P < 0.05). Oxygen (O(2)) gradients were 320 mm Hg (D703), 235 mm Hg (D903), and 247 mm Hg (Quadrox), meaning D903 and Quadrox are more efficient versus the D703 (P < 0.05). Shunt fraction (Qs/Qt) and diffusing capacity (DmO(2)) were comparable (P = ns). Diffusing capacity values indexed to BSA (DmO(2)/m(2)) were 0.15 mL O(2)/min/mm Hg/m(2) (D703), 0.2 mL O(2)/min/mm Hg/m(2) (D903), and 0.18 mL O(2)/min/mm Hg/m(2) (Quadrox) with D903 outperforming D703 (P < 0.0005). During hypothermia (32.0 +/- 0.3 degrees C), there was a lower absolute and relative VO(2 )for all three oxygenators (P = ns). The O(2) gradients, DmO(2) and DmO(2)/m(2), were significantly lower for all oxygenators (P < 0.01). Also, Qs/Qt significantly rose for all oxygenators (P < 0.01). The oxygen transfer curve is characteristic to each oxygenator type and represents a tool to quantify oxygenator performance. Using this parameter, we demonstrated significant differences among commercially available oxygenators. However, all three oxygenators are considered to meet the oxygen needs of the patients

Superior venous drainage in the "LifeBox": a portable extracorporeal oxygenator with a self-expanding venous cannula.

In an experimental setting, the performance of the LifeBox, a new portable extracorporeal membrane oxygenator (ECMO) system suitable for patient transport, is presented. Standard rectilinear percutaneous cannulae are normally employed for this purpose, but have limited flow and pressure delivery due to their rigid structure. Therefore, we aimed to determine the potential for flow increase by using self-expanding venous cannulae. Veno-arterial bypass was established in three pigs (40.6+/-5.1 kg). The venous line of the cardiopulmonary bypass was established by cannulation of the external jugular vein. The arterial side of the circulation was secured by cannulation of the common carotid artery. Two different venous cannulae (SmartCanula 18/36F 430mm and Biomedicus 19F) were examined for their functional integrity when used in conjunction with the centrifugal pump (500-3000 RPM) of the LifeBox system. At 1500, 2000, 2500, and 3000 RPM, the blood flow increased steadily for each cannula, but remained higher in the self-expanding cannula. That is, the 19F rectilinear cannula achieved a blood flow of 0.93+/-0.14, 1.47+/-0.37, 1.9+/-0.68, and 1.5+/-0.9 l/min, respectively, and the 18/36F self-expanding cannula achieved 1.1+/-0.1, 1.9+/-0.33, 2.8+/-0.39 and 3.66+/-0.52 l/min. However, when tested for venous line pressure, the standard venous cannula achieved -29+/-10.7mmHg while the self-expanding cannula achieved -13.6 +/-4.3mmHg at 1500 RMP. As the RPM increased from 2500 to 3000, the venous line pressure accounted for -141.9+/-20 and -98+/-7.3mmHg for the 19F rectilinear cannula and -30.6+/-6.4 and -45+/-11.6mmHg for the self-expanding cannula. The self-expanding cannula exhibited superior venous drainage ability when compared to the performance of the standard rectilinear cannula with the use of the LifeBox. The flow rate achieved was approximately 40% greater than the standard drainage device, with a maximal pump flow recorded at 4.3l/min