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Ann Thorac Surg 2002;74:S1330-S1333
© 2002 The Society of Thoracic Surgeons
a Department of Cardiovascular Surgery, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
* Address reprint requests to Dr von Segesser, Department of Cardiovascular Surgery, Centre Hospitalier Universitaire Vaudois (CHUV), CH-1011 Lausanne, Switzerland.
e-mail: xavier.mueller{at}chuv.hospvd.ch
Presented at the Eighth Annual Cardiothoracic Techniques and Technologies Meeting 2002, Miami Beach, FL, Jan 23–26, 2002.
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Abstract |
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METHODS: In 6 calves (78 ± 4.3 kg), the jugular vein and the carotid artery were cannulated through a cervicotomy. The Smart cannula was tested against three percutaneous cannulas with a diameter of 27, 25, and 21F, respectively. Stenotic percutaneous access to the vein was simulated by 1-cm wide tape encircling the vein that could be adjusted to a diameter of 27, 25, and 21F, respectively. The maximal flow rate, reached with stable reservoir level and a negative pressure of 44 mm Hg, was determined three times for each access size with the Smart cannula (one size fits all) and the corresponding percutaneous cannula successively.
RESULTS: For an access size of 27F, the flow of the Smart cannula was 5.7 ± 0.4 L/min and that of the percutaneous cannula was 4.3 ± 0.2 L/min (p < 0.0001); for 25F, flow rates were 5.6 ± 0.5 and 3.9 ± 0.2 L/min, respectively (p < 0.0001); and for 21F, the flow rates were 4.3 ± 0.4 and 2.7 ± 0.3 L/min, respectively (p < 0.0001). The percentage increase of flow for the 27, 25, and 21F sizes were 34% ± 9%, 42% ± 16%, and 53% ± 18%, respectively (one-way analysis of variance, p = 0.014).
CONCLUSIONS: For the present set-up, the Smart cannula outperforms commercially available percutaneous cannulas. The smaller the size of the insertion site, we observed a higher gain of flow with the Smart cannula.
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Introduction |
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| Dr von Segesser discloses that he has a pending financial relationship with Cardiosmart Ltd.
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The amount of venous drainage during cardiopulmonary bypass (CPB) is determined by the patient’s blood volume, the force of gravity, and the resistance of the venous circuit. Venous circuit resistance comes from the venous cannulas, the venous line, and the connectors. The venous cannulas are typically the narrowest component of the CPB venous system and they are thus an important determinant for venous drainage. Although poor drainage is a concern, excessive drainage may also be a problem. Excessive drainage occurs when the negative pressure of gravity is too high, leading to a drainage superior to the blood return to the central vein. Excessive drainage may lead to a collapse of the vein wall around the end of the venous cannula, a phenomenon called "chattering" or "fluttering," with intermittent reduction of venous drainage.
These problems may be exacerbated when venous cannulation is accomplished peripherally through the femoral or iliac veins. The small access site leads to the use of longer and thinner cannula with limited drainage capacity. Therefore, techniques such as assisted drainage with a centrifugal pump or the application of a vacuum force have been introduced to compensate this limitation [1]. However, these methods carry the risk of generating excess negative pressure and hence venous collapse.
To overcome these problems, a new concept of expandable venous cannula has been designed: the Smart cannula (Cardiosmart Ltd., Fribourg, Switzerland). This cannula can be inserted through a limited access, with the capacity to expand within the recipient vein, allowing an optimal drainage. We tested the drainage capacity of this expandable cannula in a large animal model and compared the results with that of a commercially available percutaneous cannula.
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Material and methods |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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Animal preparation
This study was conducted on 6 calves with a mean body weight of 78 ± 4.3 kg. All the animals were premedicated with xylazine (0.15 mg/kg, given intramuscularly). General anesthesia was started with thiopentone sodium (10 mg/kg, given intravenously) and maintained thereafter with volatile anesthetic (N2O and halothane) mixed with oxygen-enriched air. The animals were equipped with a left jugular central venous catheter and a left carotid arterial catheter for hemodynamic monitoring.
Cannula
The Smart cannula is basically a spring with a mesh configuration. Its proximal part is covered with plastic to avoid any blood leak at the introduction site and to allow connection to the venous line. For the tested application, the length was 35 cm. For the insertion, a semirigid obturator (4 mm in diameter) is placed in the lumen of the cannula. The cannula is then stretched over the obturator (Fig 1).
The obturator as well as the tip of the cannula are perforated to allow the passage of a guidewire (0.034 inches in diameter) if the Seldinger technique is required. Once in place, the obturator is removed, allowing the expansion of the spring within the recipient vein (Fig 2).
The mesh configuration of the cannula, once deployed, is illustrated on Figure 3.
The maximal diameter of the tested cannula in its expanded configuration is 14 mm. The cannula is removed from its recipient vein by simply pulling on its proximal part. With the traction, the cannula will adopt a collapsed configuration because its mesh structure confers a spring effect.
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Experimental protocol
A sternotomy was performed and the incision was extended on the right side of the neck to free the right jugular vein on its whole length. Before cannulation, heparin (Liquemin, 100 IU/kg body weight, F. Hoffmann-La Roche & Co., Basle, Switzerland), was given systemically. The activated clotting time (Hemochron; International Technidyne Corp., Edison, NJ) was kept above 400 seconds throughout the perfusion. A 24F arterial cannula (Sarns 3 mol/L; Health Care, Ann Arbor, MI) was inserted into the carotid artery. The venous cannula being tested was inserted through a transverse cut down in the distal jugular vein and positioned with its tip lying at the junction of the superior vena cava and the right atrium as determined by palpation. A standard CPB circuit with 3/8-inch to 1/2-inch polyvinyl chloride tubing was connected to the cannulas after being primed with 1500 mL of crystalloid only (NaCl 104 mmol/L, KCl 5.4 mmol/L, CaCl2 1.6 mmol/L, MgCl2 1 mmol/L, Na lactate 27 mmol/L, Na bicarbonate 50 mmol/L). The venous level of the reservoir was positioned at a vertical distance of 60 cm below the right atrium. During all the testing periods, the mean arterial pressure was kept between 70 and 80 mm Hg, and the central venous pressure was maintained at level such that the vertical distance with the level of the reservoir was 60 cm, which represents a negative drainage pressure of 44 mm Hg. The maximum flow rate achievable was recorded under steady-state conditions when the level in the venous reservoir has stabilized for 2 consecutive minutes.
In each animal, the Smart cannula was tested against three percutaneous cannulas with a diameter of 27, 25, and 21F, respectively. For the Smart cannula, the stenotic percutaneous access to the vein was simulated by a 1-cm wide tape encircling the vein that could be adjusted to a diameter of 27, 25, and 21F, respectively. The maximal flow rate was determined three times for each access size with the Smart cannula and the corresponding percutaneous cannula successively.
Statistics
Mean and standard deviation of the maximal blood flows were derived for each cannula analyzed, and they were compared using a t test. The percentage difference of flow between the two types of cannula for each size was calculated, and results were compared with one-way analysis of variance test. Values were considered to be significantly different if p < 0.05.
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Results |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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For an access size of 27F, the flow with the Smart cannula was 5.7 ± 0.4 L/min and that of the percutaneous cannula was 4.3 ± 0.2 L/min (p < 0.0001); for 25F, 5.6 ± 0.5 and 3.9 ± 0.2 L/min, respectively (p < 0.0001); and for 21F, 4.3 ± 0.4 and 2.7 ± 0.3 L/min, respectively (p < 0.0001).
Figure 4 shows the percentage gain of flow with the Smart cannula when compared with the percutaneous cannula for each size tested. One-way analysis of variance test is significant with a p value of 0.014.
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Comment |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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Beside its indication for minimal access cardiac surgery, venous cannulation through the femoral or iliac veins may be required for emergency closed CPB, for support of severely ill patients before induction of anesthesia, for prevention or management of bleeding complications during sternotomy for reoperations, for aortic and thoracic surgery, and for CPB support during high risk interventional cardiology procedures. Nevertheless nowadays, enthusiasm for minimally invasive cardiac surgery has promoted this indication as the most important one for peripheral access. Through a limited right thoracotomy, mitral valves and atrial septal defect [2] may be routinely repaired. Despite the progress in instrumentation and exposure technique, venous drainage may still be a problem with minimal access surgery. Especially when the right cavities are opened, the need for bicaval cannulation leads to congestion of the minithoracic opening. Peripheral cannulation of the inferior vena cava through a femoral access eliminates one cannula from the surgical field. However, when a femoral access is used, the corresponding cannula has a narrower diameter and thereby a limited drainage capacity.
The next step was the development of a coaxial bicaval Carpentier cannula (DLP, Grand Rapids, MI) which simultaneously drains both vena cavas through a single femoral access, thereby obviating any cannula in the surgical field. This cannula has two series of holes separated by a nonperforated segment. The distal holes lie in the superior vena cava, while the proximal holes lie in the inferior vena cava. The problem of limited drainage capacity is not solved, however. The use of a centrifugal pump has been shown to be a useful tool to overcome this limitation [2]. However, this adjunct may generate venous collapse in case of excessive drainage. Moreover, the intermediate segment between the two perforated segments lies within the atrium, which may restrict vision to the surgical target.
The Smart cannula may solve both problems linked with peripheral cannulation. Drainage capacity is optimized, as the Smart cannula takes advantage of the full size of the recipient vein. Moreover, because this cannula acts as a spring within the vein, the latter is maintained wide open by the cannula itself, thereby limiting the venous collapse phenomenon.
Since the early days of cardiac surgery, venous cannula design has seen little change. A short angulated metallic tip has been introduced to facilitate exposure in pediatric fields [3], extremity of the cannula has been equipped with an inflatable balloon to avoid snaring of the vena cava in case of total CPB [4], cannulas have been bent, and cannulas have been equipped with two series of holes to drain both vena cavas when introduced through a femoral access [5]. Nevertheless, the basic design of a conduit composed of flexible plastic usually reinforced with wire to prevent kinking had not evolved until now.
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References |
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This article has been cited by other articles:
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  L. K. von Segesser, E. Ferrari, D. Delay, O. Maunz, J. Horisberger, and P. Tozzi Routine use of self-expanding venous cannulas for cardiopulmonary bypass: benefits and pitfalls in 100 consecutive cases Eur. J. Cardiothorac. Surg., September 1, 2008; 34(3): 635 - 640. [Abstract] [Full Text] [PDF]
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M. E.W. Kirsch, Z. Kostantinos, F. Ali, E. Vermes, G. Bajan, and D. Y. Loisance Kinetic assisted venous drainage for orthotopic heart transplantation in patients under mechanical circulatory support: a double-edged sword Eur. J. Cardiothorac. Surg., March 1, 2008; 33(3): 418 - 423. [Abstract] [Full Text] [PDF]
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 S Abdel-Sayed, J Favre, J Horisberger, S Taub, D Hayoz, and L. von Segesser New bench test for venous cannula performance assessment Perfusion, November 1, 2007; 22(6): 411 - 416. [Abstract] [PDF]
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A. F. Corno Systemic venous drainage: can we help Newton? Eur. J. Cardiothorac. Surg., June 1, 2007; 31(6): 1044 - 1051. [Abstract] [Full Text] [PDF]
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 L. K. von Segesser Peripheral cannulation for cardiopulmonary bypass MMCTS, October 9, 2006; 2006(1009): 1610. [Abstract] [Full Text] [PDF]
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 L. K. von Segesser, P. Tozzi, E. Riccardo Ferrari, C. Huber, D. Delay, D. Jegger, and J. Horisberger Small access (30F) clinical central venous smart cannulation: is it adequate? Interactive CardioVascular and Thoracic Surgery, October 1, 2006; 5(5): 540 - 543. [Abstract] [Full Text] [PDF]
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D. Jegger, P.-G. Chassot, M.-A. Bernath, J. Horisberger, P. Gersbach, P. Tozzi, D. Delay, and L. K. von Segesser A novel technique using echocardiography to evaluate venous cannula performance perioperatively in CPB cardiac surgery. Eur. J. Cardiothorac. Surg., April 1, 2006; 29(4): 525 - 529. [Abstract] [Full Text] [PDF]
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A. F. Corno, J. Horisberger, J. David, and L. K. von Segesser Right atrial surgery with unsnared inferior vena cava Eur. J. Cardiothorac. Surg., July 1, 2004; 26(1): 219 - 220. [Abstract] [Full Text] [PDF]
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L. K von Segesser, P. Tozzi, I. Mallbiabrrena, D. Jegger, J. Horisberger, and A. Corno Miniaturization in cardiopulmonary bypass Perfusion, July 1, 2003; 18(4): 219 - 224. [Abstract] [PDF]
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