| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Service de Chirurgie Thoracique et Cardiovasculaire, AP-HP, Hôpital Henri Mondor, Créteil, France
Received 23 May 2007; received in revised form 31 August 2007; accepted 26 November 2007.
* Corresponding author. Address: 51 Avenue du Maréchal de Lattre de Tassigny, 94 000 Créteil Cédex, France. Tel.: +33 1 49 81 21 72; fax: + 33 149 81 21 52. (Email: matthias.kirsch{at}hmn.aphp.fr).
 |
Abstract |
|---|
 Top Abstract 1. Introduction2. Patients and methods3. Results4. DiscussionReferences |
|---|
Key Words: Cardiopulmonary bypass • Assisted venous drainage • Heart assist devices • Heart transplantation
|
1. Introduction |
|---|
|
TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionReferences |
|---|
In patients deemed at high risk of injury, cardiopulmonary bypass is usually initiated peripherally, using femoral vein and artery cannulation [2]. This technique is usually effective for partial circulatory support, but full rate cardiopulmonary bypass is usually not possible due to inadequate venous drainage. Moreover, low venous pressure secondary to blood shedding and air aspiration from injury to the walls of the right atrium or the great veins can impede adequate drainage.
Venous drainage can be increased by the use of kinetic or vacuum assistance [3]. However, although these methods augment venous return, they also expose to additional blood trauma and increase the risk and amount of air aspiration during mediastinal dissection with potential subsequent arterial line emboli [4]. In the present retrospective study, we have compared cardiopulmonary bypass parameters, blood transfusion requirements and early postoperative outcome in patients assisted with the Thoratec® paracorporeal VAD and undergoing orthotopic heart transplantation using either gravity siphon or kinetic assisted venous drainage.
|
2. Patients and methods |
|---|
|
TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionReferences |
|---|
The series comprised 28 men and five women, aged 40.4 ± 12.2 years (range, from 17 to 59 years). Primary causes for heart failure are listed in Table 1 . Patients were assisted for a mean duration of 3.02 ± 2.96 months (range, from 0.0 to 11.8 months). Five patients (15.2%) were assisted using a left ventricular device only, while 28 patients required biventricular support (84.8%).
|
Aprotinin was used in 20 (61%) patients, depending on the risk of anaphylaxis estimated by the anaesthesiologist [5]. When administered, an intravenous loading dose of 2 x 106 KIU was followed by continuous infusion of 5 x 105 KIU/ h. An additional 2 x 106 KIU were added to the bypass pump prime.
2.3 CPB cannulation technique
In 26 patients (n
= 78.8%), arterial cannulation was performed through the right or left femoral artery. In these patients, venous drainage was achieved through cannulation of a femoral vein with subsequent cannulation of the superior vena cava as soon as it was dissected free (n
= 23), or through direct bi-caval cannulation (n
= 3). In one patient a high pressure developed in the arterial line and required conversion to aortic cannulation during the course of CPB.
In the remaining seven patients (21.2%), arterial cannulation was performed directly in the distal ascending aorta or the proximal aortic arch. This approach was adopted in patients considered to be at low risk of mediastinal re-entry accident, which was left to the appreciation of the operating surgeon on the basis of the type (biventricular vs left ventricular support) and duration of support. In these patients, venous drainage was obtained through bicaval cannulation (n = 5) or separate cannulation of a femoral vein and the superior vena cava (n = 2).
Femoral vein cannulation was performed using Fem-FlexTM (Research Medical Inc., Midvale, Utah) and DLP® (Medtronic, Inc. Minneapolis, MN) femoral venous cannulae sized from 28 to 32 French (mean size 29.0 ± 1.4 French).
2.4 Perfusion strategy
In 20 patients (60.6%), femorofemoral bypass was established prior to resternotomy in order to achieve decompression of the right cavities of the heart and reduce their risk of injury, and was completed as soon as the superior vena cava could be cannulated. In the remaining patients (n = 13, 39.4%), CPB was established as late as possible during mediastinal dissection in order to reduce the duration of bypass.
2.5 Cardiopulmonary bypass circuit
In all patients the cardiopulmonary bypass circuit consisted of the following basic elements: (1) a soft shell venous reservoir bag (Affinity®, Medtronic) with a blood collection reservoir (EL Cardiotomy Reservoir, Medtronic); (2) a centrifugal arterial blood pump (Bio-Pump® Plus, Medtronic); (3) a hollow fibre membrane oxygenator (Affinity NT, Medtronic); and (4) a 40 µm arterial line filter (Jostra Quart, Maquet Cardiopulmonary AG, Germany). Perfusion flow rate was measured on line using the Medtronic Bio-Probe® flow transducer. Perfusion adequacy was monitored by continuous measurement of haemoglobin oxygen saturation in the venous blood (SvO2) using the BioTrend® oxygen saturation monitor (Medtronic).
2.6 Management of venous drainage
During the study period, two methods of venous drainage were used. With the first method (n
= 16, from 1996 to 2004), venous drainage relied solely on the gravity siphon (gravity siphon drainage, GSD).
With the second method (n = 17, from 2000 to 2004), venous return was augmented using a centrifugal pump (kinetic assisted venous drainage, KAVD). Briefly, a centrifugal Biomedicus pumphead (Bio-Pump® BPX-80, Medtronic) driven by a Biomedicus 550 pump was incorporated into the venous line between the venous cannulae and the soft shell reservoir. A pressure monitoring line was connected to the venous line approximately 10 cm before the inlet of the venous pump. Bypass commenced with gravity drainage. Once stable, KAVD was initiated and progressively increased. During bypass, the negative pressure did not exceed –80 mmHg.
Although KAVD was introduced at a later time point, there remained an overlap of both techniques during the second half of the study period (Fig. 1 ).
|
Perfusion adequacy was estimated using mean SvO2 calculated over the whole duration of CPB, and a de-saturation index, defined as the ratio of the number of SvO2 recordings 
70 mmHg by the total number of recordings.
Transfusion (red blood cells (RBC), fresh frozen plasma (FFP) and platelets) and crystalloid requirements were recorded for the perioperative period and the first 24 h in ICU. Hospital death was defined as death of any cause occurring during the hospitalisation in which the transplantation was performed. Those deaths occurring after discharge from the hospital but within 30 days of the procedure were also considered as hospital deaths.
2.8 Statistical analysis
Statistical analysis was performed using SPSS Base 12.0.1 for Windows statistical software (SPSS Inc, Chicago, IL). Continuous variables were expressed as the mean ± 1 standard deviation and compared using Student's t-test. Categorical variables were expressed as percentages and compared using the Chi-square or Fisher's exact tests, as appropriate. A p value of less than 0.05 was considered significant.
|
3. Results |
|---|
|
TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionReferences |
|---|
|
Perfusion parameters such as CPB duration, mean arterial perfusion pressure, lowest perfusion temperature and lowest haemoglobin values were similar between both patients groups (Table 3 ). Arterial re-infusion flow rates were similar between both patient groups whether the whole duration of CPB or only the first period of CPB (results not shown) was considered (Table 3).
|
3.4 Blood product use
Aprotinin therapy was given in a similar proportion in both patient groups (KAVD, 11 (68.8%), GSD 6 (53.3%); p
= 0.48). Perioperative requirements in FFP and platelet transfusions were significantly higher in the KAVD group (Table 4
). In contrast, perioperative RBC transfusion and crystalloid infusion was similar in both patient groups.
|
3.5 Outcomes
No significant differences were detected in duration of mechanical ventilation (GSD, 2.7 ± 3.7; KAVD, 4.5 ± 7.5; p
= 0.42), ICU stay (GSD, 10.5 ± 6.3 days; KAVD, 16 ± 29.2 days; p
= 0.47) and hospital mortality (GSD, 3 (18.8%); KAVD, 1 (5.9%); p
= 0.34) between both patient groups.
|
4. Discussion |
|---|
|
TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionReferences |
|---|
Heart transplantation in patients implanted with Thoratec® VAD can be extremely challenging owing to the development of dense, device-related, mediastinal adhesions which expose patients to the injury of vital structures or the inflow and outflow cannulae.
Early transplantation would obviously alleviate these difficulties. However, actual donor organ shortage renders early transplantation less probable. Furthermore, survival after cardiac transplantation is influenced by the time interval from ventricular assist device insertion to transplantation [6,7]. Thus, survival has been shown to be significantly reduced when transplantation is performed within 2–4 weeks of VAD implantation, probably as a consequence of insufficient end-organ function restoration and patient rehabilitation [7].
Several strategies have been developed in order to reduce mediastinal adhesion formation. Thus, efforts should be made at the time of device implantation to limit dissection and tissue injury as much as possible. Furthermore, postoperative bleeding should also be prevented by careful surgical haemostasis and administration of antifibrinolytic agents. Some groups advocate placement of expanded polytetrafluoroethylene membranes over the right ventricle or the device at the end of the implantation procedure [8,9]. This strategy has been shown to reduce adhesions between tissues and device surfaces without increasing the risk of infection [9].
However, none of these procedures completely obviates the risk of injury at the time of re-operation, and femorofemoral bypass prior to re-sternotomy is a cautious option in some of these patients. Unfortunately, venous drainage is often insufficient in this setting, owing to the longer and smaller venous cannula, a frequently low central venous pressure related to blood spoliation, and the frequent aspiration of air through holes in the walls of the right atrium, right ventricle or the great veins. Thus, bypass flow is often critically reduced until the superior vena cava is dissected free and another venous cannula can be inserted in order to separately drain blood from the upper part of the body and allow complete exclusion of the heart. Improved venous drainage might be obtained in this setting with newer generation venous cannulae such as the self-expandable Smart canulaTM (Cardiosmart Ltd., Fribourg, Switzerland) [10]. Alternatively, we have tried additional percutaneous cannulation of the right internal jugular vein using a 14 Fr arterial cannula in two patients. However, time constraints, full dose anticoagulation and antiaggregation and frequent history of previous jugular catheterisations in these critically ill patients render this approach unpractical.
Kinetic or vacuum assisted venous drainage has been proved useful in the setting of minimally invasive surgery [11,12] and conventional re-operations after cardiac surgery [13] by allowing higher arterial re-infusion flows [13] and reduced blood product use [14]. In the present study, we found no significant difference in arterial re-infusion rates between GSD and KAVD. Moreover, patients with KAVD appeared to have less adequate tissue oxygenation as suggested by a lower mean SvO2 and a higher desaturation index. We believe that in our specific setting of extremely difficult mediastinal dissection in patients under mechanical circulatory support, the benefit of KAVD on venous return was probably offset by an increase of the risk and amount of air aspiration. Indeed, the venous centrifugal pump and the venous reservoir bag required constant clearing of air, and CPB was frequently hampered by air-locks as has been reported in an in-vitro setting [15]. We recently improved on this limitation by adding an arterial filter on the venous line, immediately above the venous centrifugal pump.
Patients under MCS undergoing heart transplantation are at increased risk of preoperative bleeding due to mediastinal re-entry injuries but also to device related chronic activation of fibrinolytic and inflammatory pathways and anti-thrombotic treatment [16]. We have observed a nearly two-fold increase in FFP and platelet transfusion in patients undergoing KAVD. One contributing factor might be increased blood trauma due to venous line vacuum or more intense blood activation by the contact with air, although experimental [17] and clinical [14] data using vacuum assisted venous drainage do not support this hypothesis.
The findings of the present study are limited by its retrospective nature, the small number of patients in each group and the long time-span over which these patients were included. Furthermore, transplantation in patients under MCS is an extremely complex procedure and we cannot exclude the possibility that severe unmeasured bias against KAVD were present and accounted for the differences observed between both groups. However, our results suggest that the perceived benefits on venous return associated with KAVD do not necessarily translate into higher arterial re-infusion flow rates and should be carefully weighed against possible hazards such as increased air aspiration and increased blood product requirements.
|
References |
|---|
|
TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionReferences |
|---|
This article has been cited by other articles:
|
|
 |
|
  L. K. von Segesser, G. Siniscalchi, K. Kang, O. Maunz, J. Horisberger, E. Ferrari, D. Delay, and P. Tozzi Temporary caval stenting improves venous drainage during cardiopulmonary bypass Interactive CardioVascular and Thoracic Surgery, December 1, 2008; 7(6): 1096 - 1100. [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 |
