|
|
||||||||
Eur J Cardiothorac Surg 2006;29:525-529
© 2006 Elsevier Science NL
a Department of Cardiovascular Surgery, Centre Hospitalier Universitaire Vaudois (CHUV), Rue du Bugnon 46, 1011 Lausanne, Switzerland
b Department of Anesthesiology, CHUV, Lausanne, Switzerland
Received 8 June 2005; received in revised form 6 November 2005; accepted 21 December 2005.
* Corresponding author. Tel.: +41 21 3142153; fax: +41 21 3142158. (Email: David.Jegger{at}chuv.hospvd.ch).
| Abstract |
|---|
|
|
|---|
P
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 ± 17.6 years and 64.6 ± 13.1 years, respectively. Weight was 70.3 ± 11.6 kg and 72.8 ± 14.4 kg, respectively. BSA was 1.80 ± 0.2 m2 and 1.82 ± 0.2 m2, respectively. CPB times were 114 ± 53 min and 108 ± 44 min, respectively. Cross-clamp time was 59 ± 15 min and 76 ± 29 min, respectively (p
= NS). Free-Hb was 568 ± 142 U/l versus 549 ± 271U/l post-CPB for the SC and CC, respectively (p
= NS). LDH was 335 ± 73 mg/l versus 354 ± 116 mg/l for the SC and CC, respectively (p
= NS). V
m was 89 ± 10cm/s (SC) versus 63 ± 3 cm/s (CC), V
max was 139 ± 23 cm/s (SC) versus 93 ± 11 cm/s (CC) (both p
< 0.01).
P
CPB was 30 ± 10 mmHg (SC) versus 43 ± 13 mmHg (CC) (p
< 0.05). A BlandAltman test showed good agreement between the two devices used concerning flow rate calculations between CPB and TTE (bias 300 ml ± 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.
Key Words: Cardiopulmonary bypass Cardiotomy suction Haemolysis Blood
| 1. Introduction |
|---|
|
|
|---|
Recently, its usefulness has been reviewed and demonstrated in off-pump coronary artery bypass (OPCAB) [1] and during on-pump cardiopulmonary bypass (CPB) procedures [2].
Novel applications for TTE or TOE was already introduced several years ago such as evaluating the correct positioning of femoral CPB cannulae, ventricular assist device (VAD) and the intra aortic balloon pump catheter (IABP) [3,4]. With the inception of minimally invasive procedures such as Port-access, TOE was also utilised with success [5,6].
Recently, diverse applications such as placement of umbilical venous catheter, haemodialysis and jugular vein cannulation have been reported with TOE [79]. Specific to cardiac applications, TOE has been used to disobstruct venous drainage cannula and to optimise placement of venous cannulae in the inferior vena cava (IVC) [1012].
Since the inception of CPB, little progress has been made in the design of venous cannula except for minimally invasive applications [13] and three-stage venous cannula [14]. However, a self-expanding cannula, Smartcanula® (SC), was developed and tested using computational fluid dynamics (CFD) [15], in vitro [16] and in in vivo animal settings [17]. During all of the above tests, it was found to be superior compared to classic venous cannula used for CPB applications.
Therefore, the aim of this study was twofold: (1) to establish the feasibility of using echocardiography (E) to evaluate the performance of venous cannula; and (2) to compare the SC with a control one to establish which is superior.
| 2. Materials and methods |
|---|
|
|
|---|
|
2.2 Echocardiography technique
After rewarming but before weaning, a sterile sheath (Raucodrape®, Lohmann & Rauscher International GmbH & Co, Rengsdorf, Germany) was passed to the surgeon into which the epicardial TTE probe (model 15-6L, Philips, Böblingen, Germany) was inserted together with transonic gel. The probe was placed on the venous cannula at the outlet of the right atrium. Echocardiographic longitudinal and cross-sectional images are shown of the SC in situ (Fig. 1
). A Hewlett-Packard TTE machine (Sonos 5500, Philips, Böblingen, Germany) was used to perform the imaging with a frame rate of 50 Hz. Once visualisation of flow inside the cannula was possible, continual doppler imaging was performed to obtain the maximum velocity (V
max in cm/s) and mean velocity (V
m in cm/s)(Fig. 2
). The diameter of the cannula was calculated by using the pointer on the TTE machine thereby making the calculation of flow rate (Q
E and Q
CPB, subscript E denotes echocardiography and subscript CPB denotes cardiopulmonary bypass, respectively) possible from the following formula: VTI (velocity time integral using V
m
x 60) x CSA (cannula surface area). Simultaneously, the pressure drop (
P
CPB
=
P
in
P
out) between the right atrium and the inlet of the CPB venous reservoir was calculated by placing a DLP pressure transducer at the inlet to the venous reservoir (DLP 60000, Grand Rapids, MI, USA). The P
in was the central venous pressure value (CVP) while the P
out was the value indicated on the DLP pressure transducer.
|
|
|
2.5 Surgical technique
A midline sternotomy was performed. The pericardium opened anteriorly to the phrenic nerve to expose the right atrium and both venae cavae. Simultaneously, the arterial site was prepared to expose the aorta. The patient was anticoagulated with 3 mg/kg heparin (Liquemin, Hoffmann-La Roche, Basel, Switzerland) before cannulation of the aorta. Subsequent superior vena cava (SVC) and inferior vena cava (IVC) cannulation occurs or direct cannulation of the right atrium depending on the surgical procedure. CPB was initiated with passive venous drainage. The cardiac procedure was performed under direct vision. After rewarming and careful deairing manoeuvres by way of a vent placed in the ascending aorta, the aorta was unclamped. The weaning process was started once the patient was ventilated and cardiac rhythm reinitiated.
2.6 Measurements
Age, weight, body surface area (BSA), CPB and cross-clamp times were recorded. V
max (cm/s), V
m (cm/s),
P
CPB (mmHg), diameter, CSA of analysed section (mm) and Q
E (l/min) were also recorded. Free Hb and LDH values were also compared between the two groups.
2.7 Data analysis
| 3. Results |
|---|
|
|
|---|
In order to exclude any detrimental effects of the wire-interlaced design on the intimal vessel wall, Free Hb and LDH values were both comparable between the two groups (Table 2
). The SC expressed 30% greater V
m values and 33% greater V
max values compared to the CTRL (p
< 0.001, Table 2). When
PCPB was analysed, lower values of 30 ± 10 mmHg versus 43 ± 13 mmHg were observed for the SC and CTRL, respectively (p
< 0.05, Table 2). Q
CPB was comparable between the two groups. However, Q
E was significantly different when compared between the two groups.
|
|
| 4. Discussion |
|---|
|
|
|---|
During a numerical analysis using CFD, Mueller et al. [15] established lower pressure gradients across the SC which we can advocate and validate in our study performed in a clinical setting with a 30% lower
P
CPB observed (Table 2). Moreover, significantly greater mean and maximum velocities were attained for the SC for an equivalent flow rate when compared to the CTRL (Table 2). Due to the fact that higher velocities are measured within the SC, greater resistance to blood flow is encountered outside the patient or in the venous line. However, the
P
CPB is lower; thus, resistance to blood flow inside the patient (CVP) is lower which supports the superiority of the SC by showing its ability to reduce the CVP when compared to the CTRL cannula. Jegger et al. [16,17], also showed superiority of the SC in an in vitro setting demonstrating 1419% greater flow rates depending on the preload used. This phenomenon was complemented by performing in vivo animal testing with the SC exhibiting a 20% greater flow rate capacity during passive and active venous drainage techniques [20]. Similar findings were encountered by Mueller et al. [21] in a parallel bovine experiment. Undertaking clinical comparisons is difficult as once theoretical flow is attained, it is also maintained. Nevertheless, comparable flow rates of 4.8 ± 0.2 l/min and 4.4 ± 0.5 l/min for the CTRL and SC, respectively, were obtained. In our study, no additional haemolysis was associated with the use of the SC compared to the CTRL as LDH and Free Hb values were comparable (Table 2). In addition, after each CPB procedure with the smartcannula, the cannula was examined macroscopically with no deposits being found. Also, the cannulae were rinsed and visually inspected again in the absence of any thrombotic material in or around the cannulae.
TTE has previously been reported by Grooters et al. [22] in a clinical setting analysing the velocities at the outlet of several commercially available arterial CPB cannula. The intention was to evaluate whether cannula design influenced velocities and thus reduced the tendency of atherosclerotic emboli being a major cause of morbidity and mortality in the cardiac surgical community. Also, TTE has already been utilised to improve outcome when used to guide aortic cannula during on-pump CABG procedures. The use of this technique significantly reduced perioperative stroke and death [2]. Recently, the use of intraoperative epiaortic ultrasonography (EAUS) has been reported to delineate aortic atheroma. A correlation was established between atheromatous finding in the ascending aorta detected by EAUS and the presence of peripheral vascular disease. Additionally, surgical technique was altered in 24% of the population due to atheromatous finding. The changes in surgical technique included conversion from on-pump to OPCAB, change in cannulation, aortic cross-clamping or saphenous vein graft proximal anastomosis site. More importantly, no cerebral vascular accidents were observed in the patients with a pathologic aorta who were converted to off-pump CABG surgery [23].
This novel analysis has not been performed with venous cannula. However, TTE was used to determine the position of the cannula relative to the IVC or right hepatic vein (RHV). It was observed that malposition of the venous cannula into the RHV was observed in 10% of the study population. When analysing the data, it was also observed that the incidence was greater with single stage compared to two-stage cannula. It is speculated that position of the cannula deep inside the IVC is more deleterious than the positioning of it in the RHV [11].
Upon the onset of CPB or during vital manipulations during the surgical procedure, Q CPB can often take several seconds or minutes to stabilise, which are represented by a constant level of blood in the venous reservoir. However, when Q E is utilised, it is performed instantaneously or in real time and the waiting period for stabilisation of blood in the venous reservoir is substantially reduced. This is advantageous as not only instantaneous flow is measured but also change in flow patterns, such as chattering (Fig. 3C), can be identified and corrected. This improves patient safety as venous drainage is optimised, maintained and assured during the CPB procedure.
The TTE technique can be considered a valid one due to the fact that the BlandAltman analysis depicts small bias values when comparing the two methods. Also, the standard deviation is less than 10% of the theoretical flow rates often observed during CPB.
In conclusion, this study emphasises the benefit of using TTE in evaluating venous cannula performance and at the same time could be used to visualise correct placement of it in the right atrium. More so, the SC outperforms the CTRL one using this novel technique. This unique Smartcanula design, due to its self-expanding principle, provides superior flow characteristics compared to classic two stage venous cannula used for adult CPB surgery. Additionally, no haemolysis was observed in this clinical setting.
| Acknowledgments |
|---|
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
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] |
||||
![]() |
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] |
||||
![]() |
L. K. von Segesser Peripheral cannulation for cardiopulmonary bypass MMCTS, October 9, 2006; 2006(1009): 1610. [Abstract] [Full Text] [PDF] |
||||
![]() |
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] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |