Jostra Rota Flow RF-30 Pump System: A New Centrifugal Blood Pump for Cardiopulmonary Bypass

Artificial Organs 24(6):437–441, Blackwell Science, Inc. © 2000 International Society for Artificial Organs

Jostra Rota Flow RF-30 Pump System: A New Centrifugal Blood Pump for Cardiopulmonary Bypass *Yukihiko Orime, *Motomi Shiono, *Shinya Yagi, *Tomonori Yamamoto, *Haruhiko Okumura, *Kin-ichi Nakata, *Shun-ichi Kimura, *Mitsumasa Hata, *Akira Sezai, *Satoshi Kashiwazaki, *Shinsuke Choh, *Nanao Negishi, *Yukiyasu Sezai, †Takahiro Matsui, and †Mitsunori Suzuki *The Second Department of Surgery; †Clinical Engineering Room, Nihon University School of Medicine, Tokyo, Japan

Abstract: The Rota Flow pump is a fully integrated centrifugal pump system in the Jostra heart-lung machine HL-20 with features such as a less friction mono-pivot bearing system, sealless pump housing, and spiral housing. To evaluate its biocompatibility, antithrombogenesity, and hemolysis, we used it as a main pump of cardiopulmonary bypass (CPB) in coronary artery bypass grafting (CABG) cases and compared it with the BioMedicus pump. From February 1999 to May 1999, 30 consecutive patients underwent CABG under conventional CPB. Fifteen cases were supported by the Rota Flow RF-32 (Group R), and the remaining 15 were pumped by the BioMedicus BP-80 (Group B). In both groups, the flow rate was controlled in an equivalent value. Blood sampling was as follows: preoperative, 60 min after, postoperative Days (POD) 0, 1, and 2. We evaluated the plasma free hemoglobin (fHb) as the hemolysis parameter, ␤-thromboglobulin (␤-TG) and

platelet factor IV (PF-4) as the platelet deterioration index, C3, C4, and CH50 as complement activation, coagulation function, fibrinolytic factor and thrombomodulin, nitric oxide (NO), and endothelin as endothelial deterioration. This system was very easily and simply controlled and had excellent response. Perioperative laboratory data were not markedly changed in either group. The Rota Flow demonstrated equivalent value of biocompatibility and hemolysis as compared with the BioMedicus BP-80, which is a standard centrifugal pump. After pumping, no thrombus formation or pivot wear was observed inside the pump. This atraumatic, small centrifugal pump is suitable not only for CPB but also for long-term circulatory support. Key Words: Centrifugal pump—Cardiopulmonary bypass—Biocompatibility—Antithrombogenesity— Hemolysis.

In 1977, the BioMedicus centrifugal pump was introduced as an alternative to the roller pump for cardiopulmonary bypass (CPB) (1,2). Since its introduction, the BioMedicus has become increasingly popular and is the most frequently used device for the main pump in CPB and postcardiotomy support (3–5). In recent years, several types of centrifugal blood pumps have been developed intensively. However, the usage of currently available centrifugal blood

pumps is limited to 2 days because of seal-related problems (6). To overcome the problems of these conventional centrifugal pumps in longer usage such as blood leakage, thrombus formation, and hemolysis, the Rota Flow pump was developed as a completely sealless pump (7). To evaluate its controllability, biocompatibility, antithrombogenesity, and hemolysis, we first used it in Japan as the main pump in CPB in coronary bypass grafting (CABG) cases and compared it with the BioMedicus BP-80, which is the most standard centrifugal pump.

Received December 1999. Presented in part at the 7th Congress of the International Society for Rotary Blood Pumps, held August 26–27, 1999, in Tokyo, Japan. Address correspondence and reprint requests to Dr. Yukihiko Orime, 30–1 Ooyaguchi Kamimachi Itabashi-ku, Tokyo 173–8610, Japan.

MATERIAL AND METHODS Jostra Rota Flow pump This pump is very compact with a priming volume of 32 ml, an outer diameter of 85.5 mm, a height of 437

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48 mm, and a weight of 60 g (Fig. 1). Due to its compact size and low weight, the Rota Flow pump can be removed easily from and reinstalled on the console simply by lifting or placing the console into the guided position. The pump is constructed to exploit the potential of the radial magnetic drive in eliminating a central shaft and seal using a bloodflushed bearing, avoiding stagnant zones, and reducing areas of high shear and turbulence. The drive magnets are embedded in a shrouded impeller with 4 blood channels. The impeller is supported with a single pivot bearing at its bottom, in which the ball bearing is held in the center of the completely open rotor by a 1 mm steel strut. The blood gap between the impeller and housing is conical on either side, exiting into a circular recuperator and a spiral volume chamber. All blood-contacting parts are made of acrylic and polycarbonate resins. Patients Between February and May 1999, 30 consecutive patients underwent elective CABG at the Second Department of Surgery, Nihon University School of Medicine, Tokyo, Japan. Exclusion criteria included emergency operation, age (>80 years old), preoperative low left ventricular ejection fraction less than 30%, and end-organ dysfunction. In all cases, normothermia and cardioplegic (St. Thomas solution) cardiac arrest were performed under conventional CPB using a centrifugal pump. According to the pumps used in the CPB circuit, cases were divided into 2 groups. In 15 patients, the BioMedicus BP-80 (Medtronic Inc., Minneapolis, MN, U.S.A.) was used as the main pump for CPB (Group B). In another 15 cases, the Rota Flow RF32 (Jostra Medizintechnik AG, Hirrlingen, Germany) was introduced (Group R). In both groups, the same membrane oxygenator (HPO-20RHF-C, Senko Medical Instrument Mfg. Co., Ltd., Tokyo,

FIG. 1. Shown is the Rota Flow RF-32. Artif Organs, Vol. 24, No. 6, 2000

Japan), arterial filter (CBM-40, Medtronic Inc., Minneapolis, MN, U.S.A.) and priming solution were used, supporting the same flow rate of 60–70 ml/min/kg. Parameters As a postoperative course, drainage volume and urine output in the intensive care unit (ICU) were evaluated. In addition, postoperative intubation time, ICU stay, and hospital stay time were also compared in both groups. We evaluated the plasma free hemoglobin (fHb) as hemolysis, ␤-thromboglobuline (␤-TG) and platelet factor-4 (PF-4) as platelet deterioration, C3, C4, and CH50 as complement activation, fibrinogen, thrombin antithrombin III complex (TAT), and antithrombin-III (AT-III) as coagulation function, Ddimer, and fibrinogen degradation products (FDP) as fibrinolytic factors, and thrombomodurine, nitric oxide (NO), and endothelin as intimal deterioration. Blood sampling was made at 5 points as follows: preoperative, 60 min after CPB postoperative Days (POD) 0, 1, and 2. After pumping the Rota Flow RF-32 was disassembled, and thrombus formation inside the pump was observed macroscopically. In addition, wear of the male and female pivots was evaluated by scanning electron microscope (SEM) image. Statistical analysis Data are expressed as the mean ± standard deviation (SD). Statistical analysis of variance was followed by the Student t test, and a p value less than 0.05 was considered statistically significant. RESULTS Demographic data for both groups are shown in Table 1. There were no significant differences in age, gender, number of bypass grafts, aortic cross-clamp time (ACCT), CPB time, rectal temperature, bleeding volume, and urine output in operation between groups. De-airing from the Rota Flow pump was easily accomplished, and the pump can be primed quickly. No accidents associated with the pumps were indicated during pumping. The corporate operation of this system with the heart-lung machine, Jostra LH20 (Jostra Medizintechnik AG, Hirrlingen, Germany), was very easily and simply controlled. All patients were weaned from CPB easily and discharged without any complications. There were no early death cases. Postoperative states are shown

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TABLE 1. Patient characteristics

Number Age (years) Gender No. of bypass grafts ACCT (min) CPBT (min) Rectal temperature (°C) Bleeding in operation (ml) Urine in operation (ml)

Group B (BioMedicus BP-80)

Group R (Rota Flow RF-32)

p value

15 61.8 ± 6.1 12 M, 3 F 2.33 ± 0.61 76.9 ± 16.3 132.0 ± 33.4 32.8 ± 0.7 227.4 ± 121.0 1667 ± 723

15 67.5 ± 7.4 13 M, 2 F 2.53 ± 0.63 83.4 ± 23.1 144.0 ± 34.4 32.8 ± 0.9 160.8 ± 67.6 1374 ± 472

NS NS NS NS NS NS NS NS

ACCT: aortic cross clamp time, CPBT: cardiopulmonary bypass time, M: male, F: female, NS: not significant.

in Table 2. After surgery, unusual bleeding in the ICU was not observed, demonstrating no significant differences between groups. There were also no significant differences in urine output in the ICU, postoperative intubation time in the ICU, or the hospital stay. The changes of fHb are shown in Fig. 2. In both groups, it increased during and after CPB and normalized on POD-1. The fHb of Group R tended to be lower than that of Group B in CPB and POD-0; however, there were no significant differences between groups. Platelet deterioration was observed during and after CPB and recovered after the operation. In PF-4, there were no significant differences between groups (Fig. 3). The changes of C4 are shown in Fig. 4, which decreased after surgery and recovered at POD-2. C4 of Group R was significantly lower than that of Group B during CPB and at POD-3. There were also no significant differences between groups in coagulation factors (TAT and AT-III) and fibrinolytic function (D-dimer and FDP). Endothelin of both groups increased after surgery and decreased on POD-3, indicating no significant differences between groups (Fig. 5). In addition, no significant differences were found in endothelial parameters (thrombomodurine and NO). After pumping, no thrombus formation inside the pump was observed macro- and microscopically. No

evidence of significant wear of the male pivot is seen in the SEM image in Fig. 6. DISCUSSION In recent years, several types of centrifugal blood pumps were developed that can be used clinically as a main pump in cardiopulmonary bypass (CPB) and/ or circulatory support system. There are many clinically available centrifugal pumps. Therefore, appropriate device selection is the most important issue in obtaining better clinical results (8). Our clinicians need a small, less hemolytic, durable, biocompatible, and antithrombogenetic centrifugal pump. The Rota Flow pump was initially introduced as a new centrifugal pump in 1995 by Mendler and colleagues at the German Heart Center. This pump was able to reduce heat generation of the bearing and seal as well as dead water zones, and poor hydraulic efficiency with ensuring blood damage (7). It was reported that the Rota Flow was superior to several commercially available centrifugal pumps in hydraulic efficiency. However, since this first experimental study, no report has been published concerning clinical data of the pump. We clinically applied it for the main pump in CPB, and it was the first clinical usage in Japan (9). The Rota Flow RF-32, which is the most current design model, has many features (7). The pump rotor is suspended and driven by a radial permanent magnetic field that stabilizes the impeller in 4 of the

TABLE 2. Postoperative course

Drainage volume in ICU (ml) Urine output in ICU (ml) Intubation time (h) ICU stay (h) Hospital stay (day)

Group B (BioMedicus BP-80)

Group R (Rota Flow RF-32)

p value

698 ± 343 8,338 ± 2,834 7.9 ± 7.4 77.1 ± 25.7 15.2 ± 4.3

792 ± 666 7,795 ± 2,169 15.4 ± 21.7 77.5 ± 23.9 14.1 ± 2.5

NS NS NS NS NS

ICU: intensive care unit, NS: not significant. Artif Organs, Vol. 24, No. 6, 2000

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FIG. 2. The graph shows the changes in free Hb of both groups. FIG. 4. The graph shows the changes in C4 of both groups.

6 spatial degrees of freedom and allows it to be topspun on a single blood-flushed pivot bearing with minimal load and friction. A shrouded impeller with an open center and 4 logarithmically curved channels is run inside a cone-and-plate type housing with a spiral volute chamber. This pump is demonstrated to have the smallest internal volume, surface, and passage time as well as the highest hydraulic efficiency of all commercially available pumps. This pump can provide 10 L/min of pump flow rate against 400 mm Hg of total head pressure at 42,000 rpm, indicating high pump performance (7). The pump speed is adjusted to an operating point where a given pump would deliver 4 L/min against 200 mm Hg of total pressure head. This speed is kept constant, and throttle curves and hydraulic efficiencies were established. Since the introduction of the BioMedicus pump, the Rota Flow RF-32 is the most frequently used device for CPB and postcardiotomy support (3–5).

FIG. 3. The graph shows the changes in PF-4 of both groups. Artif Organs, Vol. 24, No. 6, 2000

In clinical applications around the world, the reliability, durability, and low-grade hemolysis of the BioMedicus pump has been confirmed and recognized as the standard centrifugal pump, which is the reason we selected the BioMedicus BP-80 as a standard against which to compare the Rota Flow RF-32. The postoperative course of each group was quite normal and uneventful: patients were extubated less than 15 h after surgery, stayed in the ICU for approximately 3 days, and were discharged from the hospital approximately 2 weeks after the CABG (Table 2). The fHb of Group R was lower than that of Group B; however, there were no significant differences (Fig. 2). The reason that the Rota Flow pump indicated a similar hemolysis grade of the BioMedicus was that we used the cardiotomy sucker system dur-

FIG. 5. The graph shows the changes in endothelin of both groups.

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been designed and modified to be a ventricle assist device that can be used for the long term. Therefore, additional clinical study of longer CPB and/or circulatory support, such as percutaneous cardiopulmonary support, is necessary to estimate its long-term antithrombogenesity. In this clinical study, no significant wear was revealed in the male pivot (Fig. 6). Because evaluated duration of this study was short-term, future studies will include long-term use and evaluation of wear and durability. CONCLUSIONS FIG. 6. Shown is the SEM image of the bottom male pivots after usage. There is no significant wear after pumping.

ing CPB. The maximum fHb levels of both groups were from 20 to 30 mg/dl on average, the normal acceptable range of the fHb, indicating no clinical problems. In other parameters such as platelet deterioration, complement activation, fibrinogen, coagulation function, and fibrinolytic factors, all data recovered and normalized 2 days after operation, and there were almost no significant differences between groups (Figs. 3 and 4). This means that the Rota Flow RF-32 demonstrated an equivalent and acceptable performance as compared with the BioMedicus BP-80, a standard pump, from a biocompatible point of view. The endothelium plays an important role in the regulation of vascular tone. Two systems are involved in this regulation: NO/endothelin and the prostacyclin/thromboxane systems (10). To estimate vascular tone during CPB with the 2 types of pump, endothelin, NO, and thrombomodurine were measured in this study. According to the results of the endothelin, there was a decrease on POD-3, indicating no significant differences between groups (Fig. 5). In the thrombomodurine and NO, there were also no significant differences, which indicated that the same degree of damage to the endothelium by both pumps was recognized. After pumping, there were no thrombus formations inside either pump. Excellent antithrombogenesity of this pump was confirmed. However, its pumping duration was short (144 min on average) because the operation was a conventional CABG. From the beginning of development, this pump has

The Rota Flow RF-32 demonstrated easy manipulation and good controllability. It indicated equivalent value of biocompatibility and hemolysis as compared with the BioMedicus BP-80. After pumping, no thrombus formation or pivot wear was observed inside the pump. This atraumatic, small centrifugal pump is suitable for CPB as well as circulatory support. REFERENCES 1. Lynch MF, Paterson D, Baker V. Centrifugal blood pumping for open heart surgery. Minn Med 1978;61:536–7. 2. Dixon CM, Magovern GJ. Evaluation of Bio Pump for longterm cardiac support without heparinization. J Extra Corp Tech 1982;14:331–6. 3. Noon GP, Sekela ME, Gluech J, Coleman CL, Feldman L. Comparison of Delphin and BioMedicus pumps. Trans Am Soc Artif Intern Organs 1990;36:M616–9. 4. Noon GP. Bio-Medicus ventricular assistance. Ann Thorac Surg 1991;52:180–1. 5. Golding LAR. Biomedicus centrifugal pump for mechanical cardiac support. In: Sezai Y, ed. Artificial Heart. The Development of Biometion in the 21st Century. Tokyo: Saunders, 1992:248–52. 6. Killen DA, Piehler JF, Borkon AM, Reed WA. BioMedicus ventricular assist device for salvage of cardiac surgical patients. Ann Thorac Surg 1991;52:230–5. 7. Mendler N, Podechtl F, Feil G, Hiltmann P, Sebening F. Sealless centrifugal blood pump with magnetically suspended rotor: Rot-a-Flot. Artif Organs 1995;19:620–4. 8. Orime Y, Shiono M, Hata H, Yagi S, Tsukamoto S, Okumura H, Nakata K, Kimura S, Sezai A, Sezai Y. Clinical experiences of percutaneous cardiopulmonary support: Its effectiveness and limit. Artif Organs 1998;22:498–501. 9. Hata M, Shiono M, Orime Y, Yagi S, Yamamoto T, Okumura H, Kimura S, Kashiwazaki S, Choh S, Negishi N, Sezai Y, Matsui T, Suzuki M. Clinical use of Jostra Rota Flow centrifugal pump: the first case report in Japan. Ann Thorac Cardiovasc Surg 1999;5:230–2. 10. Speekenbrink RGH, Oeveren W, Wildevuur CR, Eijsman L. Pathophysiology of cardiopulmonary bypass. In: Oz MC, Goldstein DJ, eds. Minimally Invasive Cardiac Surgery. Totowa: Humana Press Inc., 1999:9–29.

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