A Novel Device for Reducing Hemolysis Provoked byCardiotomy Suction During Open Heart Cardiopulmonary

Bypass Surgery: A Randomized Prospective Study

David Jegger, Judith Horisberger, Mirko Jachertz, Isabelle Seigneul, Piergiorgio Tozzi,Dominique Delay, and Ludwig K. von Segesser

Department of Cardiovascular Surgery, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland

Abstract: Since the inception of cardiopulmonary bypass(CPB), little progress has been made concerning the designof cardiotomy suction (CS). Because this is a major sourceof hemolysis, we decided to test a novel device (Smart-suction [SS]) specifically aimed at minimizing hemolysisduring CPB in a clinical setting. Block randomization wascarried out on a treated group (SS, n = 28) and a controlgroup (CTRL, n = 26). Biochemical parameters were takenpre-, peri-, and post CPB and were compared between thetwo groups using the Student’s t-test with statistical signifi-cance when P < 0.05. No significant differences in patientdemographics were observed between the two groups.Lactate dehydrogenase (LDH) and plasma free hemoglo-bin (PFH) pre-CPB were comparable for the CTRL and SSgroups, respectively. LDH peri-CPB was 275 � 100 U/Lversus 207 � 83 U/L for the CTRL and SS groups, respec-tively (P < 0.05). PFH was 486 � 204 mg/L versus 351 �176 mg/L for the CTRL and SS groups, respectively (P <0.05). LDH post CPB was 354 � 116 U/L versus

275 � 89 U/L for the CTRL and SS groups, respectively(P < 0.05). PFH was 549 � 271 mg/L versus 460 �254 mg/L for the CTRL and SS groups, respectively (P < 0.05). Preoperative hematocrit (Hct) of 43 � 5% (CTRL)versus 37 � 5% (SS), and hemoglobin (Hb) of141 � 16 g/L (CTRL) versus 122 � 17 g/L (SS) were sig-nificantly lower in the SS group. However, when normal-ized (N), the SS was capable of conserving Hct, Hb, anderythrocyte count perioperatively. Erythrocytes (N) were59 � 5% (CTRL) versus 67 � 9% (SS); Hct (N) was59 � 6% (CTRL) versus 68 � 9% (SS), and Hb (N) was61 � 6% (CTRL) versus 70 � 10% (SS) (all P < 0.05). Thisnovel SS device evokes significantly lowered blood PFHand LDH values peri- and post CPB compared with theCTRL blood using a CS system. The SS may be a valuablealternative compared to traditional CS techniques. KeyWords: Cardiopulmonary bypass—Cardiotomy suction—Hemolysis—Blood.

Since the inception of cardiopulmonary bypass(CPB), little progress has been made concerning thedesign and function of cardiotomy suction (CS). TheCS has already been reported in 1960 to be a majorsource of gaseous and particulate emboli (1). Inherentto all suctioning procedures is the mixing of air withblood, forming bubbles, often in a foamlike matrix.These bubbles are large and also consist of nitrogen,and are hence more stable and are associated with

other blood products or aggregate material (2). Thelarger stability is due to the differences in solubility ofnitrogen in blood compared to oxygen and carbondioxide. Due to this, a larger risk to the patient ispromoted when filtration techniques are inadequate.

Apart from emboli, hemolysis is another phenom-enon associated with CPB and thus CS. Hemolysis isalready reported with the use of different pumpsused in CPB applications (3), open venous reservoirsystems (4), oxygenators (5), and CS (2). The CS hasalso been attributed to be a major source of brainlipid emboli during CPB (6). Likewise, the braininjury marker, S100b, may also play a pivotal role inthe deleterious effects of CS (7). The hemolysis onCPB is also attributed to blood contact with the peri-cardium, excessive negative pressure, and coaspira-tion of blood with air (2).

doi:10.1111/j.1525-1594.2007.00336.x

Received May 2006; revised June 2006.Address correspondence and reprint requests to Dr. David

Jegger, Department of Cardiovascular Surgery, Centre HospitalierUniversitaire Vaudois, Rue du Bugnon 46, 1011 Lausanne,Switzerland. E-mail: David.Jegger@chuv.ch

Artificial Organs31(1):23–30, Blackwell Publishing, Inc.© 2007, Copyright the AuthorsJournal compilation © 2007, International Center for Artificial Organs and Transplantation

23

Today, the tendency to completely remove the CSduring CPB has been shown to reduce systemicinflammatory response clinically and experimentally(8–10). Additionally, the CS has been replaced withalternatives such as cell salvage (CeS) improving bio-compatibility (11). However, the biggest drawbackwith the cell saver is that the plasma proteins, coagu-lation factors, and platelets are discarded (12).

A novel remote-controlled automatic suctionsystem, Smartsuction (SS), has already been tested inan experimental setting and has been shown to beless hemolytic versus standard continuous aspirationand when compared with the cell saver (13,14). Itconsists of an optic sensor placed at its tip that aspi-rates only when the sensor detects blood, thus mini-mizing blood–air mixing.

We decided to test the SS with the following aims:(i) to establish the source of hemolysis during CPB;(ii) to establish the effects of CS on blood elements;and (iii) to evaluate the beneficial effects of the SS onblood elements and hemolysis during CPB in a clini-cal setting.

MATERIALS AND METHODS

ConsentPatients undergoing elective cardiac surgery were

studied after informed consent and approval fromthe local ethics committee. Exclusion criteriaincluded anemia and cerebrovascular and carotiddiseases.

Patient demographics are presented in Table 1.Block randomization was carried out divided intoa treated group (SS, n = 30) and a control group(CTRL, n = 26).

Anesthesia techniqueAll patients received midazolam or flunitrazepam

for premedication. Anesthesia was induced in all

patients with propofol or etomidate, opioids includ-ing fentanyl or remifentanil, and the muscle relaxantspancuronium or vecuronium. All necessary monitor-ing lines were then inserted, and anesthesia wasmaintained with propofol infusion, continuous infu-sion, or repeated doses of opioids, and pancuroniumor vecuronium administration as required.

Perfusion techniqueA heart lung machine (Stockert Medizintechnik

AG, Munich, Germany), a hollow fiber membraneoxygenator (D903 Dideco, Mirandola, Italy orQuadrox, Jostra Medizintechnik AG, Hirrlingen,Germany), a conventional tubing circuit (Dideco,Mirandola or Jostra Medizintechnik AG), and an air-oxygen blender (Sechrist Industries, Inc., Anaheim,CA, USA) were used in all the procedures.The extra-corporeal circuit is primed with 1000-mL Ringerlactate, 500-mL Haes, 100-mg heparin (Liquemin,Hoffmann-La Roche, Basel, Switzerland), an antibi-otic and 1 000 000 IU aprotinin (Trasylol, Bayer,Zürich, Switzerland) following the departmentalprotocol.

Surgical techniqueA midline sternotomy was performed. The pericar-

dium was opened anterior to the phrenic nerve toexpose the right atrium and both venae cavae. Simul-taneously, the arterial site was prepared to expose theaorta. The patient was anticoagulated with 3-mg/kgheparin (Liquemin,Hoffmann-La Roche) before can-nulation of the aorta. Subsequent superior vena cavaand inferior vena cava cannulations or direct cannu-lation of the right atrium occurred depending on thesurgical procedure. CPB was initiated with passivevenous drainage.The intracardiac procedure was per-formed under direct vision. After rewarming andcareful deairing maneuvers by way of a vent placed in

TABLE 1. Patient demographics and operative data of the study population

Group CTRL (n = 26) Group SS (n = 30)

Age (years) 64.3 � 14.4 63.6 � 15.1Gender (male/female ratio) 17/9 29/11*Body surface area (m2) 1.84 � 0.21 1.83 � 0.19Ejection fraction (%) 57.6 � 9.6 54.0 � 12.4CPB time (min) 95.7 � 34.6 110.0 � 40.0Cross-clamp time (min) 72.1 � 21.9 65.3 � 36.5Weight (kg) 74.5 � 14.6 73.3 � 13.4CABG (n and percentage) 17 (65%) 8 (20%)*Valve (n and percentage) 1 (4%) 18 (45%)*Combined (n and percentage) 4 (15%) 5 (13%)Others (n and percentage) 4 (15%) 9 (23%)

Results are expressed as means � SDs.CABG, coronary artery bypass graft.*Statistical significance expressed when P < 0.05.

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the ascending aorta, the aorta was unclamped. Theweaning process was started once the patient wasventilated and cardiac rhythm was reinitiated.

The SS deviceThe SS system (Cardio Smart, Muri, Switzerland)

is composed of a “sensitive” suction cannula, a reser-voir with an automatically controlled constant nega-tive pressure, a servo-controlled roller pump and acomputer. The suction cannula is coupled to an opticfiber that transmits an on/off signal to the computerwhich determines whether its end is in contact or notwith blood. The pressure into the reservoir is main-tained at an adjustable constant negative level. Whenthe tip of the suction cannula is in contact with blood(Fig. 1a), the sensor will automatically open a clamplocated at the entrance of the reservoir. Blood willthus immediately be aspirated. When contact is lost(Fig. 1b), the clamp closes immediately. Emptying ofthe reservoir starts when a defined high level hasbeen detected by another sensor (Fig. 1b). A secondclamp placed at the exit port of the reservoir auto-matically opens, and the roller pump simultaneouslyruns on and pumps the collected blood into the CPBcircuit. In the same way, a low-level sensor automati-cally closes the exit clamp and stops the roller pump(Fig. 1a). The reservoir is thus kept isolated, and thenegative pressure can easily be adjusted. The CTRLdevice is represented in Fig. 2. It is a typical inte-grated venous cardiotomy reservoir system utilizedduring all CPB procedures using an open reservoirsystem. The venous inlet to the reservoir (1), theblood inlet from the CS into the filtration compart-ment (2), the hardshell reservoir that holds thepatient’s blood volume (3), the filtration devicelocated inside the venous cardiotomy reservoir (4),and the outlet of the blood that is pumped from thereservoir into the oxygenator (5). Classic rollerpumps were used to aspirate the blood from the sur-gical field into the CTRL reservoir system (Fig. 2).Here, filtration occurred and the blood returned tothe patient after passing through the oxygenator.

The CeS device consisted of a high-speed centri-fuge that recuperated shed blood and concentratesthe red blood cells while eliminating the plasma andclotting factors. The cells were washed with salinesolution and transferred to a reinfusion bag forreturn to the patient.

MeasurementsAge, weight, body surface area, CPB, and cross-

clamp times were recorded. Biochemical parameterssuch as platelets, plasma free hemoglobin (PFH),lactate dehydrogenase (LDH), erythrocyte count,

hemoglobin (Hb), and hematocrit (Hct) were takenpre- (before injection of heparin), peri- (afterrewarming but before weaning), and post CPB (afterheparin neutralization with protamine).

Data analysis with respect to the aims cited in theIntroduction.

(1) We assumed that the distribution is Gaussianand performed a nonlinear regression analysisbetween LDH, PFH, and the patient demographicsusing GraphPad Prism version 4.00 for Windows

FIG. 1. (a,b) SS system. Basically, the system includes a suctioncannula (A), a reservoir (R), and a computer (C). The computercontrols four parameters: the opening of the admission clamp tothe reservoir (1), the opening of the evacuation clamp of thereservoir (2), the roller pump between the reservoir and thepatient (3), and the vacuum pressure within the reservoir (4). Onesensor is located at the tip of the cannula (S1), and two sensorsare placed within the reservoir to detect the lowest (S2) and thehighest (S3) levels of blood allowed, respectively. The sensors ofthe reservoir trigger the evacuation clamp of the reservoir as wellas the roller pump. The two scenarios are depicted: the tip of thecannula is in contact with blood; the contact of the cannula withblood is lost.

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(GraphPad Software, San Diego, CA, USA).Forward stepwise regression analysis was performedfor LDH and PFH (dependent variable) with allaforementioned patient demographic parameters asindependent variables. All analysis was done inSPSS (SPSS 12.0, SPSS Inc., Chicago, IL, USA). (2)The same analysis was performed as in (1), exceptbetween CS and the blood elements previouslycited. No forward stepwise regression analysis wasperformed. (3) Mean and SD were derived for eachparameter analyzed. Student’s t-test and analysis ofvariance for repeated measures were used for deter-mination of statistical significance between groups

(CTRL and SS) at pre-, peri-, and post-CPB timepoints concerning LDH and PFH, for blood ele-ments and when analyzing the patient demographics(P < 0.05).

RESULTS

No significant differences in patient demographicswere observed between the two groups except formale/female ratio, less coronary artery bypass graft(CABG) patients, and more valve patients in the SSgroup. There were also more CABG proceduresreported in the CTRL group versus more valve pro-cedures in the SS group (Table 1).

Source of hemolysisInitially, the hemolysis was found to be significantly

dependent upon CS with correlation coefficientsestablished for LDH (r = 0.59, P < 0.01) and PFH(r = 0.67, P < 0.01) (Fig. 3). Another determinant ofhemolysis was the CPB time exhibiting correlationcoefficients established for LDH (r = 0.44, P < 0.05)and PFH (r = 0.42, P < 0.05) (Fig. 3). In a subgroupanalysis of the CTRL group at baseline, it was evidentthat CABG patients exhibited lower amounts of PFHcompared with patients undergoing valve replace-ment, emphasizing that valve procedures exhibitlarger amounts of hemolysis as it is an open heartprocedure, and that more CS is utilized. PFH was509 � 253 mg/L (CABG) versus 767 � 415 mg/L(valves) (P = NS).

When the SS was added to the valve group, lowerPFH values (-40%) were observed 767 � 415 mg/L(CTRL) versus 463 � 270 mg/L (SS), but without sta-tistical significance. The same observation wasevident with respect to the CABG (-27%) and com-bined groups (-19%) (Table 2). This emphasized thefact that the SS was most beneficial in the valvegroup. Also, LDH showed a similar behavior com-pared to Free Hb when the SS was added (Table 2).However, statistical significance was observed forCABG and combined groups (P = 0.04).

After performing multiple regression analysis, CS(P < 0.01, r = 0.65) and cross-clamp time (P < 0.001,r = 0.79) were found to be independent predictors ofPFH. Also, CS (P < 0.01, r = 0.69) and CPB duration(P < 0.01, r = 0.59) were found to be independentpredictors of LDH.

Effects of CS on blood elementsNo correlations could be established between CS

and blood elements. However, when normalized, sig-nificant correlations could be established between CS

FIG. 2. A diagrammatic representation of the CTRL suctionsystem, which is a typical integrated venous cardiotomy reservoirsystem utilized during all CPB procedures using an open reser-voir system. The venous inlet to the reservoir (1), the blood inletfrom the CS into the filtration compartment (2), the hardshellreservoir that holds the patient’s blood volume (3), the filtrationdevice located inside the venous cardiotomy reservoir (4), andthe oulet of the blood that is pumped from the reservoir into theoxygenator (5).

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and proteins post CPB (P < 0.05, r = 0.74), normal-ized proteins post CPB (P < 0.05, r = 0.77), and nor-malized Hb values post CPB (P < 0.05, r = 0.76).

Effects of SS on blood elementsLDH pre-CPB was 178 � 49 U/L versus 167 �

55 U/L for the CTRL and SS groups, respectively(P = NS). PFH was 48 � 8 mg/L versus 39 � 14 mg/Lfor the CTRL and SS groups, respectively (P = NS).LDH peri-CPB was 275 � 100 U/L versus 207 �83 U/L for the CTRL and SS groups, respectively,being significantly lower (P < 0.05). PFHwas 486 � 204 mg/L versus 351 � 176 mg/L for theCTRL and SS groups, respectively (P < 0.05). LDHpost CPB was 354 � 116 U/L versus 275 � 89 U/Lfor the CTRL and SS groups, respectively, againshowing statistical significance (P < 0.01). PFHwas 549 � 271 mg/L versus 460 � 254 mg/L for theCTRL and SS groups, respectively (P < 0.05) (Fig. 4).

Platelets, Hct, Hb, and erythrocytes were com-parable between CTRL and SS groups (Table 3).However, it was observed that the baseline values forHct and Hb were significantly lower in the SS group,thus favoring the CTRL group (Table 3). Therefore,it was decided to normalize the parameters by pre-

bypass values. Erythrocytes, Hct, and Hb were betterpreserved perioperatively with the SS compared withthe CTRL group. Normalized mean erythrocytesdropped by 33% (SS) versus 41% (CTRL) (P = 0.01);Hct dropped by 32% (SS) versus 41% (CTRL) (P =0.01), and Hb dropped by 30% (SS) versus 39%(CTRL) (P = 0.02) (Table 3). Normalized meanplatelets were also conserved in the SS (66%) versusCTRL (60%), but without statistical significance.

All patients underwent successful CPB weaningwith minimal inotropic support and were transferredto the intensive care unit in a stable condition. Nocomplications were reported, no postoperative organdysfunction, nor any other complication related tothis technique. Echocardiographic control at day 7was normal in every patient.

DISCUSSION

This study shows that the source of hemolysis(indicative of LDH and PFH) is primarily from theCS and is dependent on the CPB time and the type ofsurgical intervention. Normalized erythrocytes, Hct,and Hb values are better conserved using the SS. Theeffects of CS are detrimental to all normalized blood

FIG. 3. Correlation of free Hb betweenthe amount of blood aspirated from theSS and the CPB time. Correlation of LDHbetween the amount of blood aspiratedfrom the SS and the CPB time.

0

600

1200

1800

0 2000 4000 6000 8000 10000 0

600

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0 50 100 150 200 250

CS (ml)

Pla

sma

Fre

e H

b (

mg

/l)

Pla

sma

Fre

e H

b (

mg

/l)

y = 0.0172x + 241.66R

2= 0.3545

p=0.007y = 0.8346x + 197.33

R2= 0.1986

p=0.026

y = 3.9864x + 210.85R

2= 0.1826p=0.03

y = 0.1046x +340.56R

2= 0.4589

p=0.001

0

200

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600

LD

H (

U/l)

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H (

U/l)

CPB time (min)

TABLE 2. Subgroup analysis of the valve, CABG, and combined procedures

CABG Valves Combined

CTRL SS CTRL SS CTRL SS

LDH (U/L) 368 � 133 278 � 46 295 � 76 286 � 81 376 � 4 283 � 72PFH (mg/L) 509 � 253 371 � 297 767 � 415 463 � 269 700 � 370 570 � 286

LDH and free Hb are expressed for the CTRL and SS groups.Results are expressed as means � SDs.

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elements tested postoperatively. The SS significantlyreduces the PFH and LDH levels during and postCPB compared with CTRL patients.

CS was only measured with the use of the SS as itis difficult to measure it in a clinical setting usinga roller pump due to the air–blood mixingphenomenon. Direct correlations between thevolume of blood aspirated and hemolytic indicatorswere established (Fig. 3), but it would be probably

more significant if the volume aspirated was mea-sured using a conventional suction system. Neverthe-less, this was undertaken by Wright et al. in anexperimental setting (2). Hemolysis provoked by theaddition of air in the CS system in an in vivo experi-ment showed a 10-fold rise compared to controls.Methods proposed in order to reduce blood traumawere the reduction of blood flow rate, increasing thediameter of the suction cannula, and avoiding airaspiration. The avoidance of air mixing is the princi-pal advantage of the SS system, and we have shownthat this reduces LDH and PFH significantly duringand post CPB (Fig. 4). Another unique feature of theSS system is its ability to quantitatively assess theamount of blood volume treated.

In this study, the extent of hemolysis was observedto be correlated with the length of CPB time andwas dependent upon the type of surgery beingperformed. Similar findings were presented with val-vular and congenital (open heart procedures) surgeryreflecting larger hemolysis levels compared withCABG (closed heart) procedures (12). One canspeculate that the opening of the cardiac chamberscauses air–blood mixing which in turn raises thehemolysis levels. In our study, we advocate thephenomenon of elevated hemolysis levels withopen heart procedures compared to CABG alone(Table 2).The length of CPB is probably attributed tomore CS being required over time and to more shearstress imparted on the blood from the arterial rollerpump over time. This was shown to be the case forplatelet degradation by Edmunds et al. with postop-erative platelet count and percent difference in plate-let count correlating significantly with the length ofthe CPB time (15). In our study, we could reproduce

0

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e H

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CTRLSS

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*

*

*

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Pre CPB Peri CPB Post CPB

LD

H (

U/l)

FIG. 4. PFH (mg/L) during the preoperative, perioperative, andpostoperative periods (*, P < 0.05). LDH (U/L) during the preop-erative, perioperative, and postoperative periods (*P < 0.05).

TABLE 3. Biochemical data of Hct, Hb, erythrocytes, platelets, and normalized values with baseline values expressed as100% for the CTRL and SS groups

Absolute values

Erythrocytes (1012/L) Hct (%) Hb (mg/L) Platelets (109/L)

CTRL SS CTRL SS CTRL SS CTRL SS

Pre 4.6 � 0.5 4.2 � 0.5 43 � 5 37 � 5* 141 � 16 122 � 17* 226 � 51 217 � 73Peri 2.8 � 0.4 2.8 � 0.4 25 � 3 25 � 4 86 � 12 85 � 14 133 � 31 168 � 76Post 2.9 � 0.4 2.8 � 0.4 26 � 3 25 � 3 89 � 11 83 � 11 140 � 35 118 � 62

Normalized values

Erythrocytes (%) Hct (%) Hb (%) Platelets (%)

CTRL SS CTRL SS CTRL SS CTRL SS

Pre 100 � 0 100 � 0 100 � 0 100 � 0 100 � 0 100 � 0 100 � 0 100 � 0Peri 59 � 5 67 � 9* 59 � 6 68 � 9* 61 � 6 70 � 10* 60 � 11 66 � 20Post 62 � 8 67 � 9 61 � 8 68 � 9 64 � 8 69 � 10 63 � 12 52 � 22

*Statistical significance expressed when P < 0.05. Results are expressed as means � SDs.

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these findings, but established significant correlationsbetween CS and proteins post CPB, normalized pro-teins post CPB, and normalized Hb values post CPB.Concerning the subgroup analysis of the differentsurgical procedures, the lack of statistical significancewith respect to PFH with the addition of the SS couldbe attributed to the inhomogeneous distribution ofthe study population, the large SDs, and the sensitiv-ity of the PFH when analyzed in the laboratory.

The damage caused by CS on other blood elementshas been reported by Tevaearai et al. in a bovinemodel with specific emphasis on normalized PFH andplatelet values in which the SS was able to signifi-cantly attenuate the damage (13). In our study, wealso showed better blood element conservation ofnormalized erythrocytes, Hct, and Hb with the use ofthe SS (Table 3). Moreover, platelet counts signifi-cantly decreased by almost threefold when suctionwas performed with air–blood mixing in an in vitrosetting (2). The SS has already been shown to con-serve blood elements such as platelets, proteins,fibrinogen, red cell count, and Hct in an experimentalsetting when compared to the CeS (14). Additionally,the CeS has been reported to show reduced cerebralfat microemboli and biocompatibility during cardiacsurgery (11,16,17). It must be emphasized that CPBin this study was performed with heparin coatedsystems. These have been used with success in aneffort to significantly reduce hemolysis and improvebiocompatibility, and thus patient outcome by avoid-ing CS and minimizing the CPB surface area (10,18).

Several alternatives to the conventional CS prin-ciple have been devised but without any successfulimplementation on the commercial market (19–21).However, this novel SS has already shown its superi-ority over traditional devices used for CS in experi-mental settings (13,14). The SS has also been usedclinically with success together with beating heartCPB systems (22). This is the first attempt to demon-strate its feasibility in the clinical cardiac setting usingclassic CPB circuitry.

LimitationsThe patient demographics show more CABG

patients in the CTRL group and more valve proce-dures or combined in the SS group. This implies thatthe study design should favor the CTRL group due tothe fact that hemolysis has been shown to be lessaccentuated in closed heart procedures. However, theresults express a preference for the SS group prob-ably due to the unique design of the device usingcutting-edge fiber optic technology which employsaspirating when required, thus avoiding the blood–gas mixing, which is the main cause of hemolysis.

Also, the use of two SS devices can be even morebeneficial for the patient and shows greater bloodelement conservation if the SS was utilized as an LVvent. Due to the fact that the study is ongoing, thepatient population will grow together with statisticalrelevance. The amount of red blood cells transfusedintraoperatively was not taken into account whenestablishing Table 3. Also, correlations established inthe study were made using CS from the SS and notfrom a CTRL. However, one can surmise that thevolumes of up to eight liters aspirated in the SS group(Fig. 3) can well reflect the volumes aspirated in acontrol setting.

In conclusion, this novel SS device evokes signifi-cantly lowered blood PFH and LDH values peri- andpost CPB compared with the CTRL blood using aclassic CS system. The SS may be a valuable alterna-tive compared to traditional CS techniques.

Acknowledgment: Special thanks to Dr. XavierMueller for his permission in allowing us to use hisFig. 1.

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