MMCTS
(October 9, 2006). doi:10.1510/mmcts.2005.001610
Copyright © 2006 European Association for Cardio-thoracic Surgery
Procedure
Peripheral cannulation for cardiopulmonary bypass
Ludwig K. von Segesser1,*
Department of Cardio-vascular Surgery, Centre Hospitalier Universitaire Vaudois, CHUV, CCV, BH 10-275, Rue du Bugnon 46, CH-1011 Lausanne, Switzerland
* Corresponding author: * E-mail: Ludwig.von-segesser{at}chuv.ch
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Summary
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Peripheral cannulation is the historical route for connecting the pump-oxygenator to the vasculature of the patient in order to establish partial or complete cardiopulmonary bypass. Although most open heart procedures are nowadays realized with central cannulation, there is renewed interest in remote cannulation through the femoral, iliac, axillary, subclavian and jugular vessels. Remote cannulation is not only of interest in hemodynamically unstable patients who can be put on cardiopulmonary bypass in local anesthesia, and stabilized prior to intubation, but also for complex procedures like replacement of the thoracoabdominal aorta, acute type A aortic dissections, complex redo open heart surgery, extracorporeal membrane oxygenation, and more recently, small access open heart surgery, robotic surgery, and others. In the following shall be described femoral arterial cannulation with standard cannulas, femoral arterial cannulation with percutaneous cannulas, femoral venous cannulation using standard cannulas, femoral venous cannulation using percutaneous cannulas, as well as optimized venous cannulation relying on more advanced cannula designs.
Key Words: Cardiopulmonary bypass • Cannulas • Cannulation • Percutaneous cannulation • Smart cannulation
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Introduction
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Peripheral cannulation is the historical route for connecting the pump-oxygenator to the vasculature of the patient in order to establish partial or complete cardiopulmonary bypass. Although most open heart procedures are nowadays realized with central cannulation (from the right atrium or both caval veins to the aorta), there is renewed interest in remote cannulation through the femoral, iliac, axillary, subclavian and jugular vessels. Remote cannulation is not only useful in hemodynamically unstable patients who can be put on cardiopulmonary bypass in local anesthesia, and stabilized prior to intubation, but also for complex procedures like replacement of the thoracoabdominal aorta [1], acute type A aortic dissections [2], complex redo open heart surgery [3], extracorporeal membrane oxygenation [4], and more recently, small access open heart surgery [5], robotic surgery [6], and others. In the following shall be described peripheral arterial and venous cannulation using traditional cannulas, percutaneous cannulas, as well as more advanced cannula designs.
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Femoral arterial cannulation with standard cannulas
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Arterial cannulation through the common femoral artery with open technique is nowadays used not only in a planned fashion for complex surgical procedures, but it is also the backup procedure for access to the arterial system if everything else has failed. Hence, the principles for open cannulation of the femoral artery with standard cannulas belong to the basic armentarium of all cardio-thoracic surgeons.
Access to the common femoral artery is guided by the following anatomical landmarks, which can be identified with relative ease by palpation: the anterior superior iliac spine and the pubic tuberculum. A straight line between these two points is the reference for finding the inguinal ligament which is undercrossed by the femoral vessels in cranio-caudal fashion. In patients with stable hemodynamics, the pulse of the femoral artery can usually be found medial to the center of the reference line mentioned before. We prefer a skin incision in cranio-caudal fashion (modifications of this incision are slightly oblique or curved), lateral to the femoral artery pulse in order to preserve the inguinal lymph nodes. Although the femoral artery can also be accessed by a truely oblique incision, the cranio-caudal incision has the advantage to be easily extended in both directions, proximally and distally, which is important in case of cannulation and decannulation problems, as well as for complex vascular repairs and distal mal-perfusion. Care is taken not to open the fascia covering the quadriceps and the sartorius muscles, which protects the femoral nerve. If the fascia is accidentally opened, we recommend systematic repair in order to maintain the normal anatomy for future explorations.
The anatomical situs of the right-sided groin ready for arterial cannulation is shown in Schematic 1 with its most important landmark: the ligamentum inguinale, which runs between the anterior superior iliac spine and the pubic tuberculum. The distal landmark of the prepared femoral artery is the departure of the deep femoral artery (Schematic 2). The latter should not be occluded by the cannula or vascular clamps during the pump run, because this vessel allows for significant collateral perfusion of the distal part of the concerned extremity through collaterals fed from the pelvis and from the contra-lateral side. Care has to be taken to respect the common origin of the superficial circumflex iliac vessels and the superficial epigastric vessels which can become major bleeders if hit (Schematic 3). We usually use one vessel loop which helps for single-handed digital control of the uncannulated, cannulated and decannulated vessel (Schematic 4). The vessel loop, or an additional proximal string around the vessel, is later combined with a snare.
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Schematic 1 Right groin prepared for femoral cannulation with its most important landmarks: the inguinal ligament, which runs between the anterior superior iliac spine and the pubic tuberculum.
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Schematic 2 The distal landmark of the prepared femoral artery is the departure of the deep femoral artery. The latter should be maintained patent during the pump run, because this allows for significant collateral perfusion of the distal part of the concerned extremity through collaterals fed from the pelvis and from the contralateral side.
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Schematic 3 Care has to be taken to respect the common origin of the superficial circumflex iliac vessels and the superficial epigastric artery which can become major bleeders if hit.
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Schematic 4 We usually use a one-vessel loop which helps for single-handed digital control of the uncannulated, cannulated and decannulated vessel. The vessel loop or an additional proximal string around the vessel is later combined with a snare.
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Examples of traditional cannulas for peripheral cannulation are shown in Photo 1. Typically, an arterial cannula slightly smaller than the arterial diameter is selected (typical size for adult males is 24 F and 22 F for adult females). A transverse incision of the clamped femoral artery is preferred for healthy vessels (can be closed by direct suturing), whereas a longitudinal arteriotomy is selected for diseased vessels (requires usually patch repair and/or a local endarteriectomy). Once the femoral artery is cannulated, the proximal side is controlled with a snare (using the vessel loop around the femoral artery) which is attached to the cannula in order to hold the latter in place, whereas the distal side remains controlled with an angulated clamp. As mentioned before, care is taken to maintain patency of the deep femoral artery.
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Photo 1 Examples of traditional cannulas for peripheral cannulation: (top) original Bardic cannula (MMCTSLink 114): straight design with a shoulder. A connector with a sidearm and a Luer lock two way stopcock have been added. (Center) modern straight cannula (MMCTSLink 115): straight design without shoulder. (Bottom) wire supported cannula with light house tip and end hole (MMCTSLink 116 – this design is guide wire compatible) or others (MMCTSLink 117 or MMCTSLink 118).
Usually, an arterial cannula slightly smaller than the arterial diameter is selected (typical size for adult males is 24 F and 22 F for adult females).
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Femoral artery repair depends on the primary arteriotomy selected. The decannulated femoral artery after transverse incision can usually be repaired by direct suture (Schematic 5). Two angle stitches kept under tension are helpful for restriction-free repair. In contrast, longitudinal incisions usually require a patch, and if more serious vessel trauma has occurred, endarteriectomy, and/or interposition of a vascular graft may be preferable.
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Schematic 5 The decannulated femoral artery after transverse incision can usually be repaired by direct suture. Two angle stitches kept under tension are helpful for restriction-free repair. A running suture in between may be adequate for larger vessels whereas interrupted sutures are preferable for smaller vessels.
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Femoral arterial cannulation with percutaneous cannulas
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Percutaneous cannulas can be used for open, semi-open, as well as percutaneous cannulation. A selection of arterial percutaneous cannulas is shown in Photo 2. The main characteristics of percutaneous cannulas include reduced cannula wall thickness, kink resistant design, guide-wire compatibility, and the combination with an intruder kit. Open cannulation with percutaneous cannulas is similar to open cannulation with standard cannulas. The main difference between open cannulation with standard cannulas and open cannulation with percutaneous cannulas is the relative ease for the latter to be used with a mandrel having a conical tip and a guidewire. The guidewire based approach has the advantage that the guide wire can be identified by transesophageal echocardiography in the aorta and its true lumen prior to cannula insertion and, therefore, the risk of false lumen perfusion can be reduced.
For percutaneous arterial cannulation we rely on the same landmarks as previously exposed for the skin incision: the anterior superior iliac spine and the pubic tuberculum. A straight line between these two points is the reference for the position of the inguinal ligament, which is undercrossed by the femoral vessels in cranio-caudal fashion (Schematic 6). In patients with stable hemodynamics, the pulse of the femoral artery can usually be found medial to the center of this reference line. Positioning the femoral artery between two parallel fingers, and direct arterial puncture with a hollow needle between the finger tips, is well established for arterial blood gas sampling, and applied in similar fashion for percutaneous cannulation. The only difference is the angle between the vascular axis and the needle, the latter being equivalent to the future axis of the percutaneous cannula. Checking for arterial pressure and adequate blood color (oxygen saturation: see also chapter on cannulation with self expanding cannula) is mandatory prior to insertion of a guide wire, small skin incision (just equivalent to the diameter of the percutaneous cannula), access dilation, and finally insertion of a mandrel supported, guide wire compatible, percutaneous arterial cannula (Photo 2).
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Schematic 6 (same as 1) Right groin prepared for femoral cannulation with its most important landmark: the ligamentum inguinale, which runs between the anterior superior iliac spine and the pubic tuberculum.
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After decannulation (withdrawal of percutaneous cannula), there are various options for vascular access site closure, including digital compression (in such a fashion, that distal perfusion is maintained), compression devices, closure devices, and finally open repair.
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Femoral venous cannulation with standard cannulas
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Femoral venous cannulation is helpful under many circumstances, and belongs to the basic armentarium for venous access which includes not only extracorporeal circulation, but also for rapid transfusion in patients with hypovolemic shock including severe trauma. The right groin prepared for femoral cannulation is shown in Schematic 6 with its most important landmark: the ligamentum inguinale, which runs between the anterior superior iliac spine and the pubic tuberculum. The distal landmark of the prepared femoral vein is the departure of the great saphenous vein and its branches (Schematic 7). This structure is usually not prepared, but reminds us, if identified, that the approach to the common femoral vein has been selected too caudal. It is helpful to identify the departure of the deep femoral vein (Schematic 8) in order to avoid this structure during the following steps. The deep femoral vein should be maintained patent during the pump run, because this allows for some venous drainage through collaterals. If a vessel loop is used, it has to be placed cranially to the deep femoral vein (Schematic 9).
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Schematic 7 The distal landmark of the prepared femoral vein is the departure of the great saphenous vein and its branches. This structure is usually not prepared, but reminds us, if identified, that the approach to the common femoral vein has been selected too caudal.
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Schematic 8 It is helpful to identify the departure of the deep femoral vein in order to avoid this structure during the following steps. The deep femoral vein should be maintained patent during the pump run, because this allows for some venous drainage through collaterals.
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Schematic 9 If a vessel loop is used, it has to be placed cranially to the deep femoral vein. A vessel loop helps for single-handed digital control of the uncannulated, cannulated, and decannulated vessel. The vessel loop or an additional proximal string around the vessel can later be combined with a snare.
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A vessel loop helps for single-handed digital control of the uncannulated, cannulated, and decannulated vessel. The vessel loop, or an additional proximal string around the vessel, can later be combined with a snare. Examples of venous cannulas (Photo 3) for open peripheral cannulation include a simple chest tube, a light house tip venous cannula including a distal orifice which makes it guide-wire compatible, and also more modern designs. Usually, a venous cannula slightly smaller than the venous diameter is selected (typical size for adult males is 28 F and 24 F for adult females). Various cannula tip designs are shown in Photos 4 and 5 (see also optimized peripheral venous cannulation with self-expanding cannulas).
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Photo 3 Examples of venous cannulas for open peripheral cannulation: (top) Chest tube (24 F); (center) (32 F) – MMCTSLink 123; (bottom) smart canula® expands from 18 F to 36 F – MMCTSLink 122.
Typically, a venous cannula slightly smaller than the venous diameter is selected (typical size for adult males is 28 F and 24 F for adult females).
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Photo 4 Tips of the venous cannulas for open peripheral cannulation: (top) chest tube presents tip orifices and several side holes (24 F); (center) Medtronic presents light house tip (32 F: guide wire compatible) – MMCTSLink 123; (bottom) Collapsed smart canula® (expands from 18 F to 36 F: mandrel and guide wire required) – MMCTSLink 124.
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Photo 5 Examples of venous cannulas for open peripheral cannulation: (top) chest tube: surface of all orifices is in the same order of magnitude as the inner diameter of the chest tube (24 F); (center) Medtronic: surface of all orifices is in the same order of magnitude as the inner diameter of the cannula (32 F) – MMCTSLink 123; (bottom) expanded smart canula®: surface of all orifices is at least one order of magnitude larger than the inner cannula diameter (expands from 18 F to 36 F: after removal of guide wire and mandrel).
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A transverse incision is preferred for cannulation of healthy veins (can be closed later by direct suturing), whereas a longitudinal phlebotomy is selected for diseased vessels (requires usually patch repair). Once the femoral vein is cannulated, its cranial side is controlled with a snare (the vessel loop around the femoral vein can be used) and secured together with the cannula, whereas the caudal side of the vein remains controlled with an angulated clamp. Care is taken to maintain the patency of the deep femoral vein in order to allow for drainage through collaterals. The decannulated femoral vein after transverse incision is shown in Schematic 10. This can usually be repaired by direct suture. Two angle stitches kept under tension are helpful for repair without restriction.
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Schematic 10 The decannulated femoral vein after transverse incision can usually be repaired by direct suture. Two angle stitches kept under tension are helpful for restriction-free repair. A running suture in between may be adequate for larger vessels whereas interrupted sutures are preferable for smaller vessels.
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Femoral venous cannulation with percutaneous cannulas
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Like on the arterial side, percutaneous venous cannulas can be used for open, semi-open, as well as percutaneous cannulation. A selection of venous percutaneous cannulas is shown in Photos 6 and 7. The main characteristics of percutaneous cannulas include reduced cannula wall thickness, kink resistant design, guide-wire compatibility, and the combination with an introducer kit. Open cannulation with percutaneous cannulas is similar to open cannulation with standard cannulas. The main difference between open cannulation with standard cannulas and open cannulation with percutaneous cannulas is the relative ease for the latter to be used with a mandrel having a conical tip and a guide wire. The guide-wire based approach has the advantage that the guide wire can be identified by transesophageal echocardiography within the superior vena cava and the right atrium. Accordingly, accidental cannulation/perforation of the right atrial appendage, right ventricle, etc., can be avoided.
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Photo 6 Two types of percutaneous venous cannulas are available: (top) the thin walled type (with or without wire winding) with its conic mandrel, which is inserted over a guide wire (e.g. Medtronic – MMCTSLink 120, Edwards Research Medical – MMCTSLink 113, Stockert – MMCTSLink 125, Heartport – MMCTSLink 111, Sarns-Terumo, etc.).
(Center and bottom) The smart canula® collapsed prior to insertion (stretched over a mandrel prior to insertion of a guide wire: center) which can be expanded after removal of the guide wire by withdrawal of the mandrel (bottom) – MMCTSLink 122.
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Photo 7 View of the tips of the percutaneous venous cannulas shown in Photo 6 various manufacturers in alphabetic order: (top) Medtronic after removal of the mandrel: all orifices are close to the tip – MMCTSLink 120; (center) smart canula® collapsed prior to insertion (stretched over a mandrel) – MMCTSLink 126; (bottom) smart canula® expanded after removal of the guide wire and the mandrel: orifices allowing for blood drainage are distributed evenly over the entire intravascular portion of the cannula – MMCTSLink 127.
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For percutaneous arterial cannulation we rely on the same landmarks as previously exposed for the skin incision: the anterior superior iliac spine and the pubic tuberculum. A straight line between these two points is the reference for the position of the inguinal ligament, which is undercrossed by the femoral vessels in cranio-caudal fashion (Schematic 6). The common femoral vein is situated medially to the common femoral artery, which can be readily palpated in patients with stable hemodynamics (see also arterial cannulation). Hiding the femoral artery with one finger, and direct venous puncture medially with a hollow needle is well established for venous blood gas sampling, and applied in similar fashion for percutaneous venous cannulation. The main difference in femoral puncture for cannulation is the axis of the needle with reference to the axis of the femoral vein. The closer the two, the easier it will be to insert the percutaneous cannula. Checking for venous pressure and adequate blood color (low oxygen saturation: see also chapter on cannulation with self expanding cannula) is mandatory prior to insertion of a guide wire, skin incision, access dilation, and finally insertion of a mandrel supported, guide-wire compatible, percutaneous venous cannula.
After decannulation (withdrawal of percutaneous cannula), there are various options for vascular access site closure. In most cases digital compression (in such a fashion, that perfusion is maintained) with or without compression devices is usually sufficient and open repair is not routine.
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Optimized venous cannulation with self-expanding cannulas
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Less invasive open heart surgery
Small access open heart surgery [5,6] has triggered the development of new technologies for efficient remote arterial and venous cannulation in order to avoid partial obturation of the small access to the surgical field. As a matter of fact, the incision required for accessing the heart can be kept smaller, if less instruments are competing for space. Various approaches have been developed for this purpose in the past. This includes guide-wire compatible cannulas which can be inserted through a small cut-down or in percutaneous fashion in a remote area (see also femoral venous cannulation with percutaneous cannulas). However, the main limitation of remote venous cannulation with traditional guide-wire compatible cannulas is inadequate flow. This is due to the fact, that the access vessel, i.e. the femoral vein, has by definition a much smaller diameter as compared to the two venae cava at the level of the right atrium (Schematic 11). Hence, a centrifugal pump or vacuum assistance are necessary for augmentation of venous return [7,8]. Unfortunately, these adjuncts do usually not allow for full flow [4] and a significant amount of blood stays within the heart. This is due to the traditional design of long, rectilinear percutaneous cannula with the access vessel diameter as main limiting factor with regard to cannula size. Even extreme negative pressure will not increase venous drainage. As a matter of fact, excessive augmentation of venous drainage with vacuum or centrifugal pump assistance, increases the risk of collapsing the venous compartment [3], with consecutive complete shut down of venous drainage.
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Schematic 11 Schematic view of the inferior vena cava (typically >20 mm in diameter), its afferent iliac as well as femoral vessels (typically approximatively 8 mm in diameter).
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Possibilities for improved venous drainage
Self-expanding smart cannulas based on the ‘collapsed insertion and expansion in situ principle’ (Schematic 12) have been shown to solve this problem. The superior performance of smart cannulation is based on its ability to take advantage of the human anatomy, which by nature increases the diameter of the mains veins in vicinity to the heart (Schematic 11). In adults, the femoral veins typically measure 8–9 mm in diameter, whereas the common iliac veins have diameters of 10 mm and more, and the inferior vena cava may reach diameters in excess of 20 mm. Hence, a venous cannula that can be inserted from the groin into the venous system with a relatively small diameter, which reaches larger (iliac and caval) diameters within the body (Schematic 13), allows for a significant reduction of the narrowed intra-cannular blood path. In accordance to Bernoulli's law, a shorter restriction results in less pressure drop, which in turn provides superior flow as demonstrated by computational fluid dynamics (CFD: [9]), in bench tests [10], and in vivo evaluation [11]. For the clinical setting, it has been shown that full venous drainage can be achieved by gravity drainage alone with trans-femoral smart cannulation of the right atrium under echocardiographic guidance [3,12].
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Schematic 12 Schematic view of the ‘collapsed insertion and expansion in situ principle’: a collapsed smart canula® (left) and an expanded smart canula® (right). In this example, partial expansion occurred over a short distance simulating a small access vessel – MMCTSLink 124.
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Schematic 13 A smart canula® expanded in situ, i.e. the inferior vena cava. It becomes clear that the majority of the intravenous blood path towards the pump-oxygenator is unrestricted.
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Practically, self-expanding cannulas are used in similar fashion as percutaneous cannulas, i.e. in open, semi-open or percutaneous fashion. The principal landmark is the inguinal ligament, which extends between the anterior superior iliac spine and the pubic tuberculum (Schematic 14). The common femoral vein is punctured with a hollow needle in the middle between the inguinal ligament and the deep femoral vein (Schematic 15). Once proper backflow (low pressure, desaturated venous blood: Schematic 16) is obtained, a J-type guide wire is introduced through the hollow needle (Schematic 17) into the common femoral vein, the iliac vein and the caval axis.
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Schematic 14 (same as 1 and 6) Right groin prepared for femoral cannulation with its most important landmark: the inguinal ligament, which runs between the anterior superior iliac spine and the pubic tuberculum.
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Schematic 15 The optimal puncture site is in between the inguinal ligament and the deep femoral vein (too caudal a puncture may later lead to interference with the deep femoral vein, too proximal may induce difficulties for control of bleeding after decannulation).
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Schematic 16 Relatively low blood pressure (droplets only) and low oxygen saturation (dark) are typical for a venous puncture.
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Schematic 17 A J-type guide wire is fed through the hollow needle. The guide wire should pass without resistance until it can be detected in the superior vena cava (TEE).
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Two self-expanding smart canula® are shown in Photo 8. One is stretched over a mandrel (collapsed state: top) and one has expanded after removal of the guide wire and the mandrel: bottom). A guide wire with a large J (7.5 mm radius) is shown in between (Photo 8). The relatively large J helps for advancing the guide wire within the vena cava. For safe operation, it is important that the guide wire can be advanced without resistance and that its final position is checked with suitable means, prior to insertion of the smart canula®. Hence, for trans-femoral right atrial smart cannulation (Schematic 18), the guide wire tip should be positioned within the superior vena cava. In similar fashion, the right position of the smart canula® tip can be identified with TEE. Schematic 19 shows the final configuration of the expanded smart canula® after removal of both, first the guide wire and second, the mandrel. Again, the effective expansion of the smart canula® can be visualized by TEE (Photo 9).
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Photo 8 Two self-expanding smart canulae® in collapsed (stretched by a guide-wire compatible mandrel: (top) and expanded shape (after removal of the guide wire and the mandrel; (bottom) respectively. In between, a J-type guide wire with a relatively large J in order to reduce the risk for cannulation of the renal veins or other branches.
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Schematic 18 Schematic view of a collapsed smart canula®, which is fed over a guide wire into the common femoral vein. Note that the guide wire tip has been previously located in the superior vena cava.
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Schematic 19 Schematic view of the expanded smart canula® after removal of the guide wire and the mandrel (note: the guide wire has to be removed prior to the mandrel in order to prevent cannula tip dislocation).
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Photo 9 Transesophageal echocardiography showing the expanded smart canula® within the superior vena cava (trans-femoral approach) after withdrawal of the mandrel.
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Optimized venous cannulation for intra-vena-caval procedures
Surgery within the inferior vena cava, e.g. at the level of the hepatic veins, can be difficult for both the surgical and the perfusion side. As a matter of fact, venous drainage from an open vena cava with traditional femoral cannulation is quite delicate, because the orifices of traditional designs are at their tip, and therefore very close to the surgical field. A permanent struggle between a flooded field, and airlock results, and can make the surgical procedure difficult. In contrast, smart cannulation using self expanding cannulas with an open wall design (Photo 9: the cannula body keeps the vessel wall apart and the vein provides the seal) allows for drainage of the venous blood from the groin and significantly reduces the risk of airlocks with only minimal restriction of venous drainage. The technology described allows for surgery with open right atrium in the absence of a snare around the inferior vena cava. Typical applications for this approach are resections of intra-vena-caval tumors (e.g. renal tumors with extension into the vena cava), hepato-atrial anastomoses (e.g. for Budd-Chiari syndrome [12]), and much more frequently, cavo-pulmonary connections (Fontan completion for univentricular heart, tricuspid atresia etc. [13]).
Optimized venous cannulation for other indications
Optimized venous cannulation based on modern cannula designs that allow for large intra-vascular cannula diameters, despite a small access orifice, is not only helpful in less invasive open heart surgery, but also in difficult redo procedures (e.g. in patients with extracardiac conduits incorporated in the sternum), heart transplantation in assist device dependant patients, as well as emergency procedures under critical conditions, where remote cannulation allowing for full flow can be realized under local anesthesia.
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Results
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As reported previously [3] the smart canula® performance was assessed prospectively in a small series of patients (mean age 62+7 years; males 2/5, females 3/5) undergoing redo procedures of the aortic valve (2/5), ascending aorta (2/5), or the thoraco-abdominal aorta (1/5). For a mean body weight of 76+17 kg (range from 55 kg to 98 kg) and a body surface area of 1.85+0.25 m2 (range from 1.5 m2 to 2.2 m2) the calculated target pump flow (2.4 l/min/m2) was 4.42+0.61 l/min (range from 3.6 l/min to 5.3 l/min). Mean pump flow achieved during cardio-pulmonary bypass was 4.84+0.87 l/min or almost 10% more than the target pump flow of 4.42 l/min. This result with gravity drainage alone is practically 20% above the flows achievable with traditional percutaneous cannulas and centrifugal pump (Biomedicus®) augmentation [4].
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Discussion
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Devices for venous cannulation have seen significant progress over time. Until today, the original, rigid steel cannulas have evolved towards flexible plastic cannulas with wire support that prevent kinking, very thinwalled wire wound cannulas allowing for percutaneous application, and all sorts of combinations. In contrast to all these rectilinear venous cannula designs which present the same cross sectional area over their entire intra-vascular path, the smart canula® concept of ‘collapsed insertion and expansion in situ’ is the logical next step for venous access. Automatically adjusting cross-sectional area up to a pre-determined diameter or the vessel lumen provides optimal flow (Table 1) and ease of use for both, insertion and removal. Reduced atrial chatter, kink resistance in situ, and improved blood drainage despite smaller access orifice size, are the most striking advantages of this new device. Potential drawbacks are similar to other percutaneous cannulas [15] and include local as well as remote vascular trauma, distal malperfusion [16], and others. However, the recommendations made above, including the preservation of the profound femoral vessels as well as the systematic verification of the guide wire position prior to cannulation, greatly reduce such risks.
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Table 1 Bovine experiments undergoing jugulo-carotid cardio-pulmonary bypass with 3 types of cannulas (percutaneous Biomedicus (27F vs. DLP basket type 28F vs. smart canula with a 14F tip), 4 different pressure differences, and 3 scenarios [17]: 1. Gravity drainage with 3/8'' tubing. 2. Centrifugal pump augmentation (Biomedicus®) with 3/8'' tubing. 3. Gravity drainage with 1/2'' tubing
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Footnotes
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1 LKvS is founder and shareholder of Smartcanula LLC, Lausanne, Switzerland. 
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References
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- Schachner T, Nagiller J, Zimmer A, Laufer G, Bonatti J. Technical problems and complications of axillary artery cannulation. Eur J Cardiothorac Surg 2005;27:634–637.[Abstract/Free Full Text]
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Summary
Introduction