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Interact CardioVasc Thorac Surg 2009;9:37-41. doi:10.1510/icvts.2008.192559
© 2009 European Association of Cardio-Thoracic Surgery
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Institutional report - Cardiopulmonary bypass

Comparison of minimally invasive closed circuit versus standard extracorporeal circulation for aortic valve replacement: a randomized study{star}

Alessandro Castiglioni, Alessandro Verzini*, Nicola Colangelo, Simona Nascimbene, Giovanni Laino and Ottavio Alfieri

Department of Cardiac Surgery, San Raffaele Hospital, Via Olgettina 60, 20132, Milan, Italy

Received 1 September 2008; received in revised form 7 February 2009; accepted 3 March 2009

{star} Presented at the 22nd Annual Meeting of the European Association for Cardio-thoracic Surgery, Lisbon, Portugal, September 14–17, 2008.

*Corresponding author. Tel.: +39 02 26437102; fax: +39 02 26437125.

E-mail address: Verzini.Alessandro{at}hsr.it (A. Verzini).


   Abstract
Top
 Abstract
1. Introduction
 2. Material and methods
 3. Results
 4. Comment
 Conference discussion
 References
 
To evaluate the clinical results of aortic valve replacement performed with a miniaturized closed circuit extracorporeal circulation (MECC) system and to compare it to standard cardiopulmonary bypass (CPB). One hundred and twenty consecutive patients undergoing isolated aortic valve replacement were randomly assigned to either a miniaturized closed circuit CPB with the maquet-cardiopulmonary MECC System© (study group, n=60) or to a standard CPB (control group, n=60). Demographic characteristic and operative data were similar in the two groups. No hospital death occurred in either group and no difference in intensive care unit (ICU) stay and in-hospital stay was observed. Patients in the study group showed lower chest tube drainage (212±62 ml vs. 420±219 ml, P<0.05) and lower need for blood products (6.1% vs. 40.4%, P<0.05) than patients in the control group. Platelet count at ICU arrival was significantly higher in the study group (139±40x10 9/l vs. 164±75x10 9/l, P=0.05). Peak postoperative troponin I release was significantly lower in the MECC group (3.81±2.7 ng/dl vs. 6.6±6.8 ng/dl, P<0.05). In this randomized study the MECC system has demonstrated best postoperative clinical results in terms of need for transfusion, platelets consumption and myocardial damage as compared to standard CPB.

Key Words: Aortic valve replacement; Minimally invasive; Extracorporeal circulation


   1. Introduction
Top
 Abstract
 1. Introduction
2. Material and methods
 3. Results
 4. Comment
 Conference discussion
 References
 
During the past decade, significant attention has been devoted to minimizing some of the metabolic alterations that negatively impact the large population of patients undergoing cardiac surgical procedures under temporary cardiopulmonary bypass (CPB).

The search for a less metabolically aggressive and more biologically respectful form of CPB has led to the development of the concept of minimal extra-corporeal circulation (MECC) and to the creation of a system capable of ensuring adequate organs preservation, utilizing a closed, extremely minimized perfusion circuit.

This novel technique has been successfully utilized in coronary artery bypass procedures [1–4], where it has shown its ability to maintain stable and appropriate tissue perfusion, while reducing the systemic inflammatory response, induced by extensive contact of blood components with foreign surfaces and air [2, 3].

The present study has been designed to evaluate the applicability and safety of the MECC system vs. conventional cardiopulmonary perfusion techniques in aortic valve replacement procedures.


   2. Material and methods
Top
 Abstract
 1. Introduction
 2. Material and methods
3. Results
 4. Comment
 Conference discussion
 References
 
One hundred and twenty consecutive patients referred to our institution for aortic valve disease were randomized either to standard CPB (Group A, control group n=60) or modified MECC system (Group B, study group n=60), between January 2005 and December 2007. The patients' written consent to be included in the study was obtained. A blind randomization was used. In order to improve the reporting of the present randomized clinical trial, the CONSORT guidelines have been followed.

Exclusion criteria included emergency operation, redo procedure, combined procedure (double valve surgery, concomitant CABG surgery, or vascular surgery), interatrial or interventricular septal defect. Patients' preoperative characteristics in both groups are summarized in Table 1.


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  		Table 1 Baseline patient characteristics

 
In group A, extracorporeal circulation was instituted by draining blood by gravity into an open venous reservoir, hard shell reservoir, and by reinfusing it into the patient at a mean flow rate of 2.4 l/min/m2 using a roller peristaltic pump (Caps, Stöckert Instruments, Munich, Germany). The circuit was completely coated with phosphorylcholine and primed with Ringer's lactate solution 1500 ml, mannitol 18% 100 ml, and porcine heparin 5000 IU. Intermittent cold blood cardioplegia (4 °C) was infused using a heat exchanger (D720 Helios C, Dideco, Mirandola, Italy) and two roller pumps.

Shed mediastinal blood suction and left heart venting were actively performed with two separated roller pumps. Additionally, blood was aspirated from the operative field with a vacuum suction device, processed in a cell saver (Compact-A, Dideco, Mirandola, Italy), and then reinfused into the patient after chest closure.

In group B, a totally coated closed circuit with a centrifugal pump was used (Rotaflow centrifugal pump and Quadrox D membrane oxygenator, Maquet-Cardiopulmonary, Rastatt, Germany). In this group a dedicated circuit was created to obtain complete air–blood separation. The circuit was primed with Ringer's lactate solution 500 ml. A double vent was used: the first one was placed through the right superior pulmonary vein and the second one through the pulmonary artery. No venous open reservoir was used. The left vent was used only when the heart was completely closed while the right vent was used during the cross-clamp time. The left and right heart blood was withdrawn by the left vent and the right vent and collected into a vacuum bag. Then it was directly reinfused into the patient via the venous cannula. All lines and cannulae were treated with bioline coating (Fig. 1).


Figure 1
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  		Fig. 1. Closed heparin-coated circuit.

 
2.1. Surgical procedure

The operation was performed using median sternotomy. Mild-to-moderate hypothermia (mean internal temperature 34 °C) was used. During aortic cross-clamping, myocardial protection was achieved by anterograde/retrograde blood cardioplegia according to Buckberg's protocol in both groups [5]. In group B, a single tailored two-stage right atrial cannula was used for venous drainage; to prevent air entry, the purse-string suture around the cannula was reinforced with a double 4-0 polypropylene to keep it completely airtight. A running suture of 2-0 polypropylene was used for valve implantation.

2.2. Anesthesia management

Induction of anesthesia was performed with fentanyl-propofol and orotracheal intubation facilitated with pancuronium (0.1 mg/kg) in both groups. Anesthesia was then maintained with propofol (2–3 mg/kg/h), isoflurane (end-tidal concentration <1 MAC) in the control group and propofol and fentanyl in the study group.

High systemic vascular resistances were treated with sodium nitroprusside, insufficient venous return was managed using fluid infusion, small doses of vasoconstrictors, Trendelenburg position and by checking if the venous cannula position was appropriate. Prior to institution of CPB, patients received intravenous porcine heparin (300 IU/kg of body weight) and additional doses were administered during CPB (5000 IU) if necessary, to maintain the activated clotting time >480 s (ACT II, Medtronic, Minneapolis, MN, USA). At the end of surgery patients were maintained sedated, mechanically ventilated and transferred to the intensive care unit (ICU). Extubation and discharge from ICU were performed according to clinical criteria. Intra- and postoperative criteria for allogenic transfusions were standardized: hematocrit value <25%.

2.3. Statistical analysis

Variables are reported as mean±S.D. Baseline characteristics and outcome were compared using {chi}2 analysis for continuous categorical data and unpaired t-test for continuous variables. Differences were considered significant only with a P<0.05.


   3. Results
Top
 Abstract
 1. Introduction
 2. Material and methods
 3. Results
4. Comment
 Conference discussion
 References
 
Demographic data did not differ significantly between the two groups particularly for age, body surface area, diabetes, peripheral vascular disease, preoperative hematocrit level and left ventricular function (Table 1).

Also there was no difference between the two groups regarding intraoperative data (Table 2).


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  		Table 2 Intraoperative data

 
The surgical procedure was well tolerated by patients, in patients undergoing surgery with the MECC system neither intraoperative perfusion accidents nor the need to switch to conventional CPB were reported.

No in-hospital mortality occurred in the two groups and there were no statistically significant differences concerning major postoperative complications between the two groups (Table 3).


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  		Table 3 Postoperative results

 
Chest tube drainage (212±62 vs. 420±219, P<0.05) and blood transfusion requirements (6.1% vs. 40.4%, P<0.02) were significantly reduced in MECC patients compared to patients undergoing standard CPB (Table 4). The time course of hematocrit was significantly higher at all time points during surgery and hospital stay in the study group (P<0.02) (Fig. 2); similarly, the platelet count at ICU admission was significantly higher in the study group (164±75x109/l vs. 139±40x109/l, P=0.05) (Table 5).


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  		Table 4 Results

 

Figure 2
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  		Fig. 2. Time course of mean hematocrit level during and after CPB.

 

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  		Table 5 Laboratory data

 
The peak measurement of serum cardiac troponin T was 3.8±2.7 ng/dl in group B and 6.6±6.25 ng/dl in group A (P<0.03) (Fig. 3).


Figure 3
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  		Fig. 3. Myocardial injury: mean troponin level (ng/ml). CPB, cardiopulmonary bypass; MECC, minimal extracorporeal circulation.

 

   4. Comment
Top
 Abstract
 1. Introduction
 2. Material and methods
 3. Results
 4. Comment
Conference discussion
 References
 
Cardiac surgery with the use of CPB incites systemic abnormalities of the inflammatory and coagulation cascades. Factors that have been assumed to lead to this abnormal systemic inflammatory response include contact of the blood with the large non-endothelial surfaces of the extracorporeal circuit, the release of tissue factor due to the surgical trauma, the activated coagulation factors in mediastinal shed blood, the shear forces generated by cardiotomy suction, and the mechanical alteration of corpuscular blood elements due to mechanical propelling devices [6, 7].

The use of heparin-coated circuits improved biocompatibility by reducing complement activation, platelet consumption, and inflammatory response, associated with CPB [8]. Fromes and colleagues have shown a reduction of inflammatory response after coronary bypass grafting with total MECC. Particularly, authors observed that levels of IL-6 and TNF {alpha}, potent proinflammatory cytokines with negative inotropic properties, were significantly lower in the MECC group than the corresponding levels in the control group [9]. Therefore, the MECC system seems to trigger a lower activation of monocytes, thus leading to a lesser release of proinflammatory cytokines such as IL-6 and TNF {alpha}.

Along with several authors, we have observed that patients undergoing cardiac surgery with the MECC system show decreased postoperative bleeding, reduced blood transfusion requirements, better platelets preservation, and reduced release of myocardial necrosis biomarkers. Besides, the MECC group also showed significantly lower peak postoperative cardiac troponin I release with respect to the control group. It is conceivable that the lower peak measurement of serum cardiac troponin T is due to the lesser release of cytokines from leukocytes, i.e. the major actors in the inflammatory reaction [9, 10].

Renunciation of a cardiotomy sucker connected to a venous reservoir avoids the direct reinfusion of air-activated blood that may also be contaminated with tissue debris and lipids. The amount of circulating thrombin and the severity of coagulopathy associated with CPB are decreased, thanks to the fact that blood from the operative field is not added to the perfusion circuit; this is obtained by using a closed circuit. In the control group, activated shed blood has been sucked up from the surgical field into the CPB circuit, whereas in the MECC group it has been washed in a cell saver, before re-infusion. The feasibility of this perfusion technique in open heart surgery raises doubts. However, positioning a vent through the pulmonary artery trunk allows to avoid blood–air contact; after aortic cross-clamp release the blood–air contact can be reduced by the use of the vent placed through the right superior pulmonary vein.

Increased postoperative blood loss may cause activation of fibrinolysis and platelet dysfunction in shed blood. Recently, Liebold and colleagues have reported that a closed bypass circuit in CABG patients is associated with a decreased incidence of cerebral microembolization as compared to the traditional open CPB system. In the paper, authors speculated that the observed decreased incidence of cerebral microembolization was mainly due to the closed CPB design, without cardiotomy suction and venous reservoir. Likewise, the use of membrane oxygenator with a tight hollow fiber membrane was reported as beneficial [11, 12].

The present study shows a significant decrease in postoperative blood loss measured as total chest tube drainage and transfusion requirement with the MECC system in aortic valve replacement. Hemodilution is unavoidable in crystalloid prime CPB because of mixing of the crystalloid prime solution with the patient's blood. The on-pump nadir hematocrit value can widely change according to the patient body mass index (or blood volume), and pre-CPB hematocrit level, as well as circuit prime volume [13, 14].

The explanation for the reduced postoperative blood loss observed in the MECC group is certainly multifactorial.

Platelet dysfunction with the loss of aggregability is largely reported as a cause of bleeding after CPB [15]. On the other hand, the MECC system was associated with platelet preservation. In the present study, we have observed a greater reduction on platelet counts in the traditional CPB group with respect to the MECC group. This confirms a depletion arising from contact activation with extracorporeal surfaces, cardiotomy suction and filters. Surely, an important limitation of the study is that it assesses only the platelet count, without examining the platelet function.

There are several other limitations of this study that should be recognized; first, the sample size was not large enough to demonstrate the system safety. The MECC system offers less safety than standard CPB because of the absence of venous reservoir. A risk of gas embolism exists if there is an air-intake on the venous side. A learning curve for this technique is, therefore, necessary for the surgical and anesthetic team.

Although, we are aware that a sample size of 60 patients is too small to provide final results, the MECC system has demonstrated best postoperative clinical results in terms of need for transfusion, platelets consumption and myocardial damage as compared to the standard CPB. In patients who underwent surgery with the MECC system neither intra-operative perfusion accidents nor the need of switching to conventional CPB were reported. Moreover, no apparent device-related adverse events were emphasized. On these grounds, the MECC technique could be an additional step toward reduction of surgical injury in selected patients with high risk of bleeding, e.g. patients with cirrhosis, liver disease and thrombocytopenia.


   Conference discussion
Top
 Abstract
 1. Introduction
 2. Material and methods
 3. Results
 4. Comment
 Conference discussion
References
 
Dr. A. Liebold (Rostock, Germany): I have two questions. What was the amount of the pericardial suction blood in the MECC group?

And how did you process this blood? Did you use a cell saver or did you discard this blood?

Dr. Verzini: In the MECC group we processed the blood before reinfusing it in the patients using a cell saver system.

Dr. Liebold: And which amount?

Dr. Verzini: I'm sorry?

Dr. Liebold: Which amount of shed blood did you collect in your cell saver?

Dr. Verzini: In the MECC group about half a liter of pericardial shed blood was sucked.

Dr. Liebold: But you didn't collect it precisely, and you have no data on it?

Dr. Verzini: We didn't collect exactly the amount of shed blood because we expected that it was almost the same as in the control group using two vents.

Dr. J. Skorpil (Pilsen, Czech Republic): Why did you exclude the CABG cases and combine cases together in that study because I think it's the target of our aging population?

Dr. Verzini: We already use the MECC system in CABG patients, but in this study we preferred to examine only the patients with alone aortic valve disease. So we decided to exclude patients with coronary artery disease because this could be a bias in the results in terms of amount of bleeding and troponin release.

Dr. Skorpil: So more or less the same origin of the disease?

Dr. Verzini: I'm sorry? I didn't understand.

Dr. Skorpil: It's the same origin of the disease, isn't it?

Dr. Verzini: Certainly both coronary artery disease and aortic valve stenosis share the same origin.


   References
Top
 Abstract
 1. Introduction
 2. Material and methods
 3. Results
 4. Comment
 Conference discussion
 References
 

  1. Harig F, Feyrer R, Mahmoud F, Blum U, Von der Emde J. Reducing the post-pump syndrome by using heparin-coated membrane oxygenator, steroids, or aprotinin. Thorac Cardiovasc Surg 1999;47:111–118.[Medline]
  2. Gulielmos V, Menschikowski M, Dill H-M, Thiele S, Tugtekin SM, Jaross W, Schueler S. Inteleukin-1, interleukin 6 and myocardial enzyme response after coronary artery bypass grafting – a prospective comparison of the conventional and three minimally invasive surgical techniques. Eur J Cardiothorac Surg 2000;18:594–601.[Abstract/Free Full Text]
  3. Immer F, Pirovino C, Gygax E, Englberger L, Tevaerai H, Carrel T. Minimal versus conventional cardiopulmonary bypass: assessment of intraoperative myocardial damage in coronary bypass surgery. Eur J Cardiothorac Surg 2005;28:701–704.[Abstract/Free Full Text]
  4. Wippermann J, Albes J, Hartrumpf M, Kaluza M, Vollandt R, Bruhin R, Wahlers T. Comparison of minimally invasive closed circuit extracorporeal circulation with conventional cardiopulmonary bypass and with off-pump technique in CABG patients: selected parameters of coagulation and inflammatory system. Eur J Cardiothorac Surg 2005;28:127–132.[Abstract/Free Full Text]
  5. Buckberg GD, Dyson CW, Emerson RC. Techniques for administering clinical cardioplegia. Blood cardioplegia. A text-book of clinical cardioplegia. Mt. Kisco, New York: Futura Publishing Co; 1982.
  6. de Haan J, Boonstra PW, Monnink SHJ, Ebels T, van Oeveren W. Retransfusion of suctioned blood during cardiopulmonary bypass impairs hemostasis. Ann Thorac Surg 1995;59:901–907.[Abstract/Free Full Text]
  7. Hansbro SD, Sharpe DAC, Catchpole R, Welsh KR, Munsch CM, McGoldrick JP, Kay PH. Hemolysis during cardiopulmonary bypass: an in vivo comparison of standard roller pumps, non-occlusive roller pumps and centrifugal pumps. Perfusion 1999;14:3–10.[Abstract/Free Full Text]
  8. Koster A, Fischer T, Praus M, Haberzettl H, Kuebler WM, Hetzer R, Kuppe H. Hemostatic activation and inflammatory response during cardiopulmonary bypass: impact of heparin management. Anesthesiology 2002;97:837–841.[CrossRef][Medline]
  9. Fromes Y, Gaillard D, Ponzio O, Chauffert M, Gerhardt MF, Deleuze P, Bical OM. Reduction of the inflammatory response following coronary bypass grafting with total minimal extracorporeal circulation. Eur J Cardiothorac Surg 2002 Oct;22:527–533.[Abstract/Free Full Text]
  10. Remadi JP, Rakotoarrivelo Z, Marticho P, Trojette F, Benamar A, Poulain H, Tribouilloy C. Aortic valve replacement with the minimal extracorporeal circulation (Jostra MECC System) versus standard cardiopulmonary bypass: a randomized prospective trial. J Thorac Cardiovasc Surg 2004 Sep;128:436–441.[Abstract/Free Full Text]
  11. Liebold A, Khosravi A, Westphal B, Skrabal C, Choi YH, Stamm C, Kaminski A, Alms A, Birken T, Zuralowski D, Steinhoff G. Effect of closed minimized cardiopulmonary bypass on cerebral tissue oxygenation and microembolization. J Thorac Cardiovascular Surg 2006;131:268–276.[Abstract/Free Full Text]
  12. Albes JM, Stöhr I, Kaluza M, Siegemund A, Schmidt D, Vollandt R, Wahlers T. Physiological coagulation can be maintained in extracorporeal circulation by means of shed blood separation and coating. J Thorac Cardiovasc Surg 2003;126:1504–1512.[Abstract/Free Full Text]
  13. Habib RH, Zacharias A, Schwann TA, Riordan CJ, Durham SJ, Shah A. Adverse effects of low hematocrit during cardiopulmonary bypass in the adult: should current practice be changed? J Thorac Cardiovasc Surg 2003;125:1438–1450.[Abstract/Free Full Text]
  14. DeFoe GR, Ross CS, Olmstead EM, Surgenor SD, Fillinger MP, Groom RC, Forest RJ, Pieroni JW, Warren CS, Bogosian ME, Krumholz CF, Clark C, Clough RA, Weldner PW, Lahey SJ, Leavitt BJ, Marrin CA, Charlesworth DC, Marshall P, O'Connor GT. Lowest hematocrit on bypass and adverse outcomes associated with coronary artery bypass grafting. Ann Thorac Surg 2001;71:769–776.[Abstract/Free Full Text]
  15. Weerasinghe A, Taylor KM. The platelet in cardiopulmonary bypass. Ann Thorac Surg 1998;66:2145–2152.[Abstract/Free Full Text]




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