Heat generation and hemolysis at the shaft seal in centrifugal blood pumps

The heat and hemolysis around a shaft seal were investigated. Materials were original pumps (Nikkiso HMS-15:N-original, and 3M Delphin:D-original), vane-removed pumps (Nvane(-), Dvane(-)), and a small chamber with a shaft coiled by nichrome wire (mock pump). The original pumps were driven at 500 mmHg and 5 L/min, and vane-removed pumps were driven at the same rotation number. An electrical powers of 0, 0.5, 2, and 10 W was supplied to the mock pumps. In vitro hemolytic testing showed that hemolytic indices were 0.027 g/100 L in N-original, 0.013 in Nvane(-), 0.061 in D-original, and 0.012 in Dvane(-). Measurement of heat with a thermally insulated water chamber showed total heat within the pump of 8.62 and 10.85 W, and heat at the shaft seal of 0.87 and 0.62 W in the Nikkiso and Delphin pumps, respectively. Hemolysis and heat generation of mock pumps remained low. The results indicate that the heat generated around the shaft seal was minimal. Hemolysis at the shaft-seal was considerable but not major. Local heat did not affect hemolysis. It was concluded that the shaft-seal affected hemolysis, not by local heat but friction itself.     

Clinical evaluation of the centrifugal pump in open heart surgery: a comparative study of different pumps

Pulmonary embolism after cardiac surgery is attributed to embolization from thrombus within the deep venous system. We report two cases of pulmonary embolism after coronary artery bypass surgery in which transesophageal echocardiography detected in situ right atrial thrombus. The right atrium should be screened for thrombus in patients who have pulmonary embolism after cardiac surgery.     

The role of the centrifugal pump in hemolysis during neonatal extracorporeal support

A study was conducted to evaluate coronal microleakage of Super EBA and Ketac-Endo when used as sealers with single-cone gutta-percha (GP) root canal obturation. The root canals of 24 extracted human teeth were instrumented with flared preparations to a minimum #40 master apical file size. Ten teeth were obturated with a single GP cone and Super EBA as the sealer and ten teeth were obturated with a single GP cone and Ketac-Endo as the sealer. Four teeth were used as controls. Salivary bacterial microleakage studies were conducted to determine whether these sealers could prevent coronal microleakage through the root canal in the absence of a coronal tooth restoration. There was no bacterial penetration through the apical foramen for either sealer tested during the 60-day test period.     

Structure of cast components for centrifugal ore pumps. Part 1

With a view to reducing the development time and costs for new flow components of ore pumps, the operation of a Gr pump is simulated by means of FlowVision software. On the basis of the resulting three-dimensional model of the Gr 8 pump and hydrodynamic calculations for the basic pump design, zones of increased flow velocity may be identified. These zones are in good agreement with the zones of increased wear. That confirms the applicability of the model and permits the determination of means of improving the pump geometry (structure).     

Alterations in erythrocyte morphology induced by blood pumps

A scanning electron microscopy was used after in vitro and in vivo tests to investigate any alterations caused by the peristaltic roller pump in erythrocyte morphology. The electron micrographs of samples were examined as follows: 1) by image analyser; 2) by applying Bessis's classification for the qualitative study of crenated red blood cells (RBCs). The in vitro test was repeated four times using blood from healthy donors. Each basal blood sample was divided into 250 ml portions, each of which was recirculated for 12 minutes at different flow rates. In order to verify any persistent erythrocyte damage caused by the peristaltic pump, 15 minutes after recirculation at 450 ml/min, another sample was prepared using the blood remaining from the last test. A statistically significant direct correlation was found between blood flow (Qb) increase and the percentage of morphologically altered RBCs, when either using an image analyser (r = 0.97; p < 0.05) or Bessis's classification (r = 0.95; p < 0.05). However, neither method showed any statistically significant difference between the percentage of deformed RBCs, determined in the basal sample, or in the percentage found at the end of the 450 ml/min test after standing 15 minutes at room temperature. The in vivo test was carried out on 6 patients over 2 dialysis sessions, which differed only for the Qb: 250 versus 400 ml/min. The two dialysis sessions gave comparable results when using both study methods regarding the presence of deformed RBCs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Haemodynamic changes in patients undergoing high-risk PTCA under protection of transfemoral heart- lung machine support with centrifugal pumps

Deletions, mutations and the functional inactivation of tumor suppressor gene p16 are involved in the genesis of different neoplasias. Little is known about the role of p16 gene alterations in the genesis of gastric carcinomas. This study aimed to detect genetic alterations of the p16 gene in gastric carcinomas. We analyzed p16 gene mutations and the frequency of loss of heterozygosity (LOH) at the p16 locus in 43 gastric carcinomas. PCR-SSCP analysis of exons 1 and 2 revealed only one gene mutation in a carcinoma of the diffuse type. Besides carcinomas of the diffuse, intestinal and the mixed type, we also investigated a small-cell primary gastric carcinoma, which was the only one to show a deletion in the p16 gene. LOH analysis was performed using two polymorphic markers located near the p16 gene (D9S171, D9S162) and a sequence-tagged-site marker (c5.1). Allelic loss was noted in two carcinomas of the diffuse type and in one carcinoma of the intestinal type. Allelic instabilities were found in one tumor of the intestinal type and diffuse type each. Although only five of 43 (11.6%) gastric carcinomas had p16 alterations, tumors of the diffuse type tend to show a higher number of genetic alterations near the p16 locus.     

Estimating mechanical blood trauma in a centrifugal blood pump: laser Doppler anemometer measurements of the mean velocity field

There are different opinions on the duration of post-operative shoulder immobilisation following arthroscopic repair of labrum tears. Between 1993 and 1994 at our department arthroscopic repairs of the glenoid labrum as described by Habermeyer (15, 16) have been performed in 38 patients. In 20 of these patients postoperative treatment included immobilisation of the operated shoulder in a Gilchrist-bandage for 3 weeks, while in the remaining 18 patients this postoperative immobilisation period was decreased to only 1 or 2 weeks. Physiotherapy started the day after the operation, using a device for passive-motion exercises. The mean follow-up time of our examinations was 15.4 month. The mean score by Rowe rose significantly from 20.0 preoperatively to 82.6 at the follow-up examination. Results were excellent or good in 89.4% of all cases, new shoulder dislocations did not occur in any case. Patients having their shoulders immobilised for 3 weeks reached significantly higher Rowe-scores at our follow-up than those patients, whose shoulders were immobilised for only 1 or 2 weeks. Therefore, postoperative management following arthroscopic repair of labrum tears should include immobilisation of the operate shoulder for 3 weeks and an early start of passive-motion exercises.     

Noninvasive pump flow estimation of a centrifugal blood pump

A flow rate estimating method was investigated for a centrifugal blood pump developed in our institute. The estimated flow rate was determined by the power consumption, the rotating speed of the motor, and the hematocrit value. The power consumption and the rotating speed of the motor were measured with a wattmeter. The examinations were performed in a closed mock loop filled with goat blood with hematocrit values of 21.5%, 28%, 34%, and 42%. Measured values of blood viscosity were 2.47, 3.09, 3.71, and 5.07 mPa.s at a share rate of 37.5/s, respectively. A linear correlation between the power consumption and the pump flow rate was observed in all hematocrit values. But variations in hematocrit caused a difference in the flow rate up to 1.1 L/min at the same power consumption and rotating speed. Effects of blood viscosity on the flow estimation were corrected by the hematocrit value. The value of the coefficient of determination, R2, between the estimated flow rate and the measured flow rate was 0.988. These results may indicate that the flow estimating method calculated by the power consumption of the motor, the rotating speed, and the hematocrit value is useful in the clinical situation.     

Two functionally different Na/K pumps in cardiac ventricular myocytes

The whole-cell patch-clamp technique was used to voltage clamp acutely isolated myocytes at -60 mV and study effects of ionic environment on Na/K pump activity. In quiescent guinea pig myocytes, normal intracellular Na+ is approximately 6 mM, which gives a total pump current of 0.25 +/- 0.09 pA/pF, and an inward background sodium current of 0.75 +/- 0.26 pA/pF. The average capacitance of a cell is 189 +/- 61 pF. Our main conclusion is the total Na/K pump current comprises currents from two different types of pumps, whose functional responses to the extracellular environment are different. Pump current was reversibly blocked with two affinities by extracellular dihydro-ouabain (DHO). We determined dissociation constants of 72 microM for low affinity (type-1) pumps and 0.75 microM for high affinity (type-h) pumps. These dissociation constants did not detectably change with two intracellular Na+ concentrations, one saturating and one near half-saturating, and with two extracellular K+ concentrations of 4.6 and 1.0 mM. Ion effects on type-h pumps were therefore measured using 5 microM DHO and on total pump current using 1 mM DHO. Extracellular K+ half-maximally activated the type-h pumps at 0.4 mM and the type-1 at 3.7 mM. Extracellular H+ blocked the type-1 pumps with half-maximal blockade at a pH of 7.71 whereas the type-h pumps were insensitive to extracellular pH. Both types of pumps responded similarly to changes in intracellular-Na+, with 9.6 mM causing half-maximal activation. Neither changes in intracellular pH between 6.0 and 7.2, nor concentrations of intracellular K+ of 140 mM or below, had any effect on either type of pump. The lack of any effect of intracellular K+ suggests the dissociation constants are in the molar range so this step in the pump cycle is not rate limiting under normal physiological conditions. Changes in intracellular-Na+ did not affect the half-maximal activation by extracellular K+, and vice versa. We found DHO-blockade of Na/K pump current in canine ventricular myocytes also occurred with two affinities, which are very similar to those from guinea pig myocytes or rat ventricular myocytes. In contrast, isolated canine Purkinje myocytes have predominantly the type-h pumps, insofar as DHO-blockade and extracellular K+ activation are much closer to our type-h results than type-1. These observations suggest for mammalian ventricular myocytes: (a) the presence of two types of Na/K pumps may be a general property. (b) Normal physiological variations in extracellular pH and K+ are important determinants of Na/K pump current. (c) Normal physiological variations in the intracellular environment affect Na/K pump current primarily via the Na+ concentration. Lastly, Na/K pump current appears to be specifically tailored for a tissue by expression of a mix of functionally different types of pumps.     

Orbital sinus blood sampling in rats as performed by different animal technicians: the influence of technique and expertise

We have investigated the effects of chronic hypoxia on the acute adrenergic stress response of adult rainbow trout (Oncorhynchus mykiss). The goal of this study was to determine whether a prior 5-d exposure of fish to lowered environmental oxygen levels (60 or 80 Torr) would influence the nature of catecholamine secretion from chromaffin tissue in situ. Using a saline-perfused posterior cardinal vein preparation, it was demonstrated that the basal (unstimulated) secretion of noradrenaline and adrenaline was increased at 60-Torr hypoxia. In response to cholinergic (carbachol-elicited) stimulation, noradrenaline and adrenaline secretion were significantly affected by prior exposure to hypoxia. The construction of dose response curves revealed that noradrenaline secretion was enhanced at the lowest doses of carbachol (1 - 5 x 10(-7) mol kg(-1)) and that this was reflected by an approximate 10-fold reduction in the ED50 (the dose of carbachol eliciting half-maximal noradrenaline secretion). The effect of chronic hypoxia on in situ carbachol-evoked adrenaline secretion was similar but less pronounced. The results of this study suggest that during chronic moderate hypoxia, increased basal catecholamine secretion and enhanced responsiveness of chromaffin cells to cholinergic stimulation, as well aiding the ongoing stress, may assist the physiological adaptations to subsequent bouts of more severe acute stress.     

Control of centrifugal blood pump based on the motor current

In this study, centrifugal pump performance was examined in a mock circulatory loop to derive an automatic pump rotational speed (rpm) control method. The pivot bearing supported sealless centrifugal pump was placed in the left ventricular apex to aorta bypass mode. The pneumatic pulsatile ventricle was used to simulate the natural ventricle. To simulate the suction effect in the ventricle, a collapsible rubber tube was placed in the inflow port of the centrifugal pump in series with the apex of the simulated ventricle. Experimentally, the centrifugal pump speed (rpm) was gradually increased to simulate the suction effect. The pump flow through the centrifugal pump measured by an electromagnetic flowmeter, the aortic pressure, and the motor current were continuously digitized at 100 Hz and stored in a personal computer. The analysis of the cross-spectral density between the pump flow and motor current waveforms revealed that 2 waveforms were highly correlated at the frequency range between 0 and 4 Hz, with the coherence and phase angles being close to 1.0 and 0 degree, respectively. The fast Fourier transform analysis of the motor current indicated that the second harmonic component of the motor current power density increased with the occurrence of the suction effect in the circuit. The ratio of the fundamental to the second harmonic component decreased less than 1.3 as the suction effect developed in the circuit. It is possible to detect and prevent the suction effect of the centrifugal blood pump in the natural ventricle through analysis of the motor current waveform.     

New method of evaluating sublethal damage to erythrocytes by blood pumps

We recently proposed a new concept, the total destruction time of erythrocytes, to indicate sublethal damage to erythrocytes by blood pumps. In this article, results of additional experiments concerning this new concept are reported. Five paired in vitro hemolysis tests with bovine blood were conducted using a cone-type centrifugal pump (Group A) and an impeller-type pump (Group B). A total pressure head of 100 mm Hg was applied. The factors evaluated were the normalized index of hemolysis and the total destruction time, or the pumping duration, required to raise the level of the plasma-free hemoglobin to 50% of the total hemoglobin. The morphologic change of the erythrocytes also was analyzed. The percentage of crenated cells was calculated from blood smear specimens 1 min after starting the pumps and 2 h before the total destruction time of Group A in each experiment. Although there was no statistical difference in the normalized index of hemolysis between the two groups, the total destruction time of Group A erythrocytes was significantly shorter than that of Group B (18.9 +/- 4.5 h and 33.7 +/- 9.9 h in Group A and Group B, respectively; p < 0.02). The rate of crenated erythrocytes was higher in Group A than in Group B at a point 2 h before the total destruction time of Group A. The total destruction time values seem to define a good method for establishing sublethal traumatic damage to erythrocytes in blood pumps.     

Three-dimensional numerical prediction of stress loading of blood particles in a centrifugal pump

The successful use of centrifugal pumps as temporary cardiac assist devices strongly depends on their degree of blood trauma. The mechanical stress loading experienced by cellular components on their passage through the pump is a major cause of blood trauma. Prediction of the mechanical stresses will assist optimization of pump design to minimize hemolysis and platelet activation. As a theoretical approach to this task., the determination of the complete three-dimensional (3D) flow field including all regions of high shear stress is therefore required. A computational fluid dynamics (CFD) software package, TASCflow, was used to model flow within a commercially available pump, the Aries Medical Isoflow Pump. This pump was selected in order to demonstrate the ability of the CFD software to handle complex impeller geometries. A turbulence model was included, and the Newtonian as well as the Reynolds stress tensor calculated for each nodal point. A novel aspect was the assignment of scalar stress values to streaklines representing particle paths through the pump. Scalar stress values were obtained by formulating a theory that enables the comparison of a three-dimensional state of stress with a uniaxial stress as applied in all mechanical blood damage tests. Stress loading-time functions for fluid particles passing inlet, impeller, and outlet domains of the pump were obtained. These showed that particles undergo a complex, irregularly fluctuating stress loading. Future blood damage theories would have to consider an unsteady stress loading regime that realistically reflects the flow conditions occurring within the pump.(ABSTRACT TRUNCATED AT 250 WORDS)     

Preclinical evaluation of the Kyocera Gyro centrifugal blood pump for cardiopulmonary bypass

The Kyocera Gyro pump has been developed as a completely seal-less centrifugal pump to overcome the problems of the conventional centrifugal pumps. The Gyro pump is a double pivot bearing-supported centrifugal pump with several specific design features, including its eccentric inlet port. We investigated the feasibility of the Gyro pump for cardiopulmonary bypass (CPB) in a bovine model, comparing it with the BioMedicus pump (BP-80). Ten healthy calves (5: Gyro pump, 5: BP-80) underwent 6 h of mildly hypothermic CPB at approximately 33 degrees C. Both pumps provided more than 50 ml/kg/min without any incidents. The haemodynamics of both groups remained stable within the normal range. All haematology and biochemistry data demonstrated no significant differences between the two groups. However, values of plasma-free haemoglobin and lactate dehydrogenase were less throughout the experiments of the Gyro pump than those of the BP-80. To obtain flow equivalent to that of the BP-80, the Gyro pump needed less rotational speeds than the BP-80 (2749.7 +/- 233.3 versus 3170.6 +/- 300.8 rpm. p < 0.05). Less rotational speed in addition to the difference in operating principle may contribute to less blood damage during the CPB OF the Gyro pump. After pumping for CPB, no leakage or thrombus formation was observed in either pump. The present study indicated that the Kyocera Gyro pump can be applied as a centrifugal pump for CPB with the same performance as the BP-80 and with relatively less haemolysis than the BP-80.     

Gastric emptying in humans: influence of different regimens of parenteral nutrition

The origins of the -28 A->C and frameshift Cd 11 - T(Fs CD 11-T)alleles were investigated by beta-globin cluster haplotype analysis. These alleles were found in a Mexican mestizo family with beta-thalassemia (beta-thal). The -28 A->C mutation was described previously in Kurdish Jews linked to the most common haplotype in the world(+----++),the same haplotype observed in this Mexican family. Therefore, it is not possible to assess a new origin of the -28 A->C mutation in our population. The Fs Cd 11 -T allele, not reported to date in any other populations, was linked to the -++--+-haplotype (sixth in frequency in the world). This haplotype has not been reported in association with any beta-thal mutant, suggesting a Mexican origin for the Cd 11 -T mutation.     

A quantitative visualization study of flow in a scaled-up model of a centrifugal blood pump

There is increasing evidence that adenosine (ADO) and dopamine (DA) interact directly in the basal ganglia via actions at ADO A2a and DA D2 receptors, respectively. The purpose of this study was to determine 1) the extent to which these receptors modulate endogenous GABA release in discrete regions of the rat basal ganglia and 2) whether GABA release is modulated by a direct and opposing interaction between ADO A2a and DA D2 receptors. Tissue slices of striatum (STR) containing globus pallidus (GP; STR/GP) and micropunches of STR, GP, and substantia nigra pars reticulata (SNr) were studied. Radioligand binding demonstrated that ADO A1, ADO A2a, and DA D2 receptors were present in each of the tissue preparations with the exception of SNr, in which ADO A2a receptors were not detected. Stimulation of ADO A2a receptors with CGS 21680 (1-10 nM) increased electrically stimulated GABA release in STR/GP slices and GP micropunches. Consistent with the lack of A2a receptors in SNr, CGS 21680 had no effect on GABA release from this region. In contrast, stimulation of DA D2 receptors with N-0437 (1-100 nM) inhibited evoked GABA release from STR/GP slices and both GP and SNr micropunches. The D2-mediated inhibition of GABA release in GP was abolished in the presence of CGS 21680 (10 nM). These experiments demonstrate that stimulation of ADO A2a and DA D2 receptors has opposing effects on endogenous GABA release in STR and GP. These opposing actions may explain the antagonistic interactions between ADO and DA that have been observed in behavioral studies and support the hypothesis that the striatopallidal efferent system is an important anatomical substrate for the A2a/D2 receptor interaction.     

Less blood damage in the impeller centrifugal pump: a comparative study with the roller pump in open heart surgery

A centrifugal pump with an impeller (Nikkiso Centrifugal Pump, Model HPM15; Nikkiso Co. Ltd.) was applied to cardiopulmonary bypass (CPB) in 14 patients who underwent elective coronary artery bypass grafting. Serum hemoglobin level, platelet count, and serum beta-thromboglobulin (beta TG) level were measured during CPB. The results were compared with those obtained in a comparative roller pump (RP) group (n = 10). There was no difference in the time on CPB between the NP (109 min) and RP (121 min) groups. The serum beta TG level (ng/ml) was lower in the NP group than in the RP group (obtained 90 min after the initiation of CPB). The plasma-free hemoglobin level also was lower in the NP group than in the RP group (obtained 90 min after the initiation of CPB, 120 min after the initiation of CPB, immediately after the termination of CPB, 3 h after termination of CPB; p < 0.01). There was no significant difference in platelet depletion. The HPM15 pump showed excellent hemodynamic performance with less blood trauma compared with the roller pump in its clinical application to open heart surgery.     

The influence of lymphocytes on blood proteins in vitro

The authors report of some results of a clinical follow-up study of 76 schizophrenic patients in psychosis observed during the puerperal period. Two types of the process were distinguished: a recurrent type and attack-like progressive. Some diffrential diagnostical criteria are given permitting to differ recurrent schizophrenia from somatogenic and infectious psychoses.