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K Redmann

Publications and source records attributed to K Redmann.

At least 19 recordsLinked to original sources
PubMed2006

Intrathoracic implantation of a continuous flow left ventricular assist device--the microdiagonal blood pump.

AIM: All existing ventricular assist devices are associated with a considerable number of serious complications. We report on our first animal tests with a newly developed microdiagonal blood pump (MDP). METHODS: Six female calves underwent MDP implantation. The inflow and outflow conduit were anastomosed to the left atrium and the descending aorta. The MDP was placed in the left phrenicocostal sinus. Pump flow was adjusted to 2-3 L/min. Hemodynamic and echocardiographic data as well as blood samples were measured over the test period of 7 days. Thereafter, all internal organs and the pump were explanted for thorough examination. RESULTS: Mean arterial (90.5+/-12.1102.7+/-8.7 mmHg) and mean pulmonary arterial (17.3+/-2.420.6+/-2.7 mmHg) pressures remained stable during the test period. Cardiac output (5.4+/-0.5 = or >3.5+/-0.5 L/min) decreased postoperatively due to partial unloading of the heart. Left ventricular end-diastolic (4.4+/-0.5= or >3.8+/-0.4 cm) and end-systolic (3.4+/-0.5 =or >2.9+/-0.4 cm) diameters decreased after MDP implantation and did not change during the test period. Mean number of platelets (550+/-57 =or >350+/-86 x 103/microL) and hemoglobin (13.2+/-1.3 = or >11.9+/-0.8 g/dL) decreased perioperatively due to surgical reasons and recovered in the postoperative course. Free hemoglobin was slightly enhanced in the postoperative course. CONCLUSION: Our results demonstrate that the MDP is suitable for intrathoracic implantation and provides a reliable left ventricular unloading.

Animals↗
PubMed2004

The forces generated within the musculature of the left ventricular wall.

OBJECTIVES: To test the hypothesis that two populations of myocardial fibres-fibres aligned parallel to the surfaces of the wall and an additional population of fibres that extend obliquely through the wall-when working in concert produce a dualistic, self stabilising arrangement. METHODS: Assessment of tensile forces in the walls of seven porcine hearts by using needle probes. Ventricular diameter was measured with microsonometry and the intracavitary pressure through a fluid filled catheter. Positive inotropism was induced by dopamine, and negative inotropism by thiopental. The preload was raised by volume load and lowered by withdrawal of blood. Afterload was increased by inflation of a balloon in the aortic root. The anatomical orientation of the fibres was established subsequently in histological sections. RESULTS: The forces in the fibres parallel to the surface decreased 20-35% during systolic shrinkage of the ventricle, during negative inotropism, and during ventricular unloading. They increased 10-30% on positive inotropic stimulation and with augmentation in preload and afterload. The forces in the oblique transmural fibres increased 8-65% during systole, on positive inotropic medication, with an increase in afterload and during ventricular shrinkage, and decreased 36% on negative inotropic medication. There was a delay of up to 147 ms in the drop in activity during relaxation in the oblique transmural fibres. CONCLUSION: Although the two populations of myocardial fibres are densely interwoven, it is possible to distinguish their functions with force probes. The delayed drop in force during relaxation in obliquely oriented fibres indicates that they are hindered in their shortening to an extent that parallels any increase in mural thickness. The transmural fibres, therefore, contribute to stiffening of the ventricular wall and hence to confining ventricular compliance.

Animals↗
PubMed2001

Does a suitable animal model for research on partial left ventriculectomy exist? Animal models for PLV.

Partial left ventriculectomy is a new surgical option quickly introduced into clinical use worldwide for treating end-stage heart failure in patients with dilated cardiomyopathy. Due to the overwhelming success of this new kind of surgical treatment for dilated cardiomyopathy, experimental research on the physiological and pathophysiological basis was initially not performed. Now, demands for an appropriate animal model have arisen more and more since the outcome of patients treated by partial left ventriculectomy has differed considerably. This review summarizes available experimental models for heart failure in large animals, and discusses their suitability for research on partial left ventriculectomy.

Animals↗
PubMed2001

Treatment strategy and perioperative risk in patients with idiopathic thrombocytopenic purpura undergoing cardiac surgery.

Patients suffering from idiopathic thrombocytopenic purpura undergoing cardiac surgery with extracorporeal circulation may be at increased risk for postoperative bleeding complications. Therefore, different treatment strategies, such as conservative treatment, splenectomy, transfusion of platelet concentrates and therapy with immunoglobulins have been proposed. We report on our experiences with preoperative immunoglobulin treatment in selected patients with special regard on the optimal dosage.

Aged↗
PubMed2000

Preoperative immunoglobulin treatment in patients with Werlhof's disease undergoing cardiac operation.

BACKGROUND: Patients with Werlhof's disease and undergoing a cardiac surgical procedure with cardiopulmonary bypass are at increased risk for bleeding complications. We report the usefulness of preoperative immunoglobulin treatment in selected patients. METHODS: Between May 1995 and July 1998, 10 patients with Werlhof's disease underwent a cardiac surgical procedure with cardiopulmonary bypass in our department. Five patients with mean platelet counts of less than 80x10(9)/L received immunoglobulin therapy preoperatively (group 1). The other 5 patients with mean platelet counts higher than 80x10(9)/L were not so treated (group 2). RESULTS: In group 1, mean platelet count increased from 54x10(9)/L 5 days before operation to 112x10(9)/L after immunoglobulin treatment (p = 0.018) and did not fall to less than 60x10(9)/L postoperatively. Patients in group 1 received 16 units of packed red blood cells and 5 units of platelet concentrate. Patients in group 2 required 24 units of packed red blood cells, 5 units of platelet concentrate, and 23 units of fresh frozen plasma. Only 1 patient (group 2) had a surgical bleeding complication that required reexploration. Mean drainage loss was 1,100 mL in group 1 and 1,210 mL in group 2. CONCLUSIONS: Our data demonstrate that immunoglobulin treatment of patients with Werlhof's disease and mean platelet counts of less than 80x10(9)/L significantly augments platelet counts preoperatively. It may be useful in selected patients.

Adult↗
PubMed2000

Late ventricular structure after partial left ventriculectomy.

Nine months after partial ventriculectomy, a 53-year-old man died of progressive heart failure. His heart was examined to determine the alignment of the muscle fibers around the ventricular scar, which was 11 cm long, 1.3 cm thick and 4 cm wide. The scar reached 2 to 12 mm beyond the surgical suture line. The fibers in the middle and subendocardial layers were malaligned, resulting in convergence, compression and regional necrosis.

Cardiomyopathy, Alcoholic↗
PubMed1997

A silicone rubber mould of the heart.

The macroscopical structure of the ventricular myocardium has been an unsolved problem since the XVIth century, when Anatomy started as an authentic science. Since then the spatial organization of the myocardial fibres has represented, as Pettigrew says, "an arrangement so unusual and perplexing, that it has long been considered as forming a kind of Gordian knot in Anatomy. Of the complexity of the arrangement I need not speak further than to say that Vesalius, Albinus, Haller and De Blainville, all confessed their-inability to unravel it". What is shown in the present paper is the result of an anatomical work, developed over 43 years, by means of which it has been shown that the ventricular myocardial mass consists of a band, curled in a helical way, which extends from the pulmonary artery to the aorta. This is illustrated by a silicone rubber model cast from an actual unrolled myocardial band.

Animals↗
PubMed1997

The heart muscle's putative "secondary structure'. Functional implications of a band-like anisotropy.

Opinions are divided as to whether the rope-like secondary structure, which Torrent-Guasp dissected out of the myocardial body by the blunt unwinding technique (BUT) reveals some kind of functional compartmentation of the heart muscle. The myocardial fibres are aligned parallel to the fibre disruption (cleavage) plane, along which the band has been prepared but they are not necessarily aligned parallel to the long axis of the band. Inconsistencies in the myocardial rope model arise from the obligatory zones of transmural inflection, which are obvious in the base and the apex of both ventricles. They are, however, merely discernible in the midzone of the left ventricular cone. The investigator experienced in BUT knows that the cleavage plane is not unique. We doubt the assumption that the rope structure is the predominant stress transmission pathway, because the fibre strand peel-off technique (SPOT) delivers irregular fibre disruption planes which are definitely different from those which Torrent-Guasp prepares. The rope-like fibre arrangement could be just a redundant structure, a remnant of past developmental steps without, however, any functional implication to the human heart. On the other hand, peeling-off fibre strands from the ventricular wall produces deeply perforating, i.e., oblique transmurally grooved surfaces. Putative functions of force transmission in an oblique transmural direction are (1) ventricular dilation as a function of the variable inclination angle with respect to the epicardial surface, (2) monitoring of ventricular wall stress and ventricular size and (3) segmental stiffening which could serve other dependent segments as a punctum fixum.

Anisotropy↗
PubMed1997

The heart's fibre alignment assessed by comparing two digitizing systems. Methodological investigation into the inclination angle towards wall thickness.

Myocardial contractile pathways which are not aligned strictly parallel to the heart's epicardial surface, give rise to forces which also act in the ventricular dilating direction. We developed a method which allows us to assess any fibre orientation in the three-dimensional myocardial weave. Decollagenized hearts were prepared by peeling-off fibre strands, following their main fibre orientation down to near the endocardium. In the subepicardium the strands followed a course more or less parallel to the epicardium, whereas from the mid-wall on they tended to dive progressively deeper into the wall. The preparation displays more or less rugged surfaces rather than smooth layers. The grooves and crests on the exposed surfaces were sequentially digitized by two methods: (1) Using a magnet tablet (3 Draw Digitizer System, Polhemus, Cochester VTO 5446, USA) on a dilated pig heart we manually followed the crests using a stylus, handling each groove and crest as an individual contractile pathway. (2) A constricted cow heart was digitized using a contact-free optical system (opto TOP, Dr. Breuckmann, Meersburg, Germany), which is based on the principle of imaging triangulation. Using specially developed software the inclination angles of selected crests and grooves with respect to the epicardial surface were calculated. The two digitizing methods yield comparable results. We found a depth- and side-specific weave component inclined to the epi-endocardial direction. This oblique netting component was more pronounced in the inner 1/3 of the wall than in the subepicardium. The inclination angle probably increases with increasing wall thickness during the ejection period. Manual digitizing is an easy and fast method which delivers consistent results comparable with those obtained by the cumbersome high resolution optical method. The rationales for the assessment of transmural fibre inclination are (1) the putative existence of dilating forces inherent in the myocardial weave and (2) the possible overproportional increase in the oblique transmural weave component during myocardial hypertrophy, which would entail a reduction in efficiency of ventricular performance in terms of haemodynamic work.

Animals↗
PubMed1997

Computation of the alignment of myocardial contractile pathways using a magnetic tablet and an optical method.

The computation of the inclination angle of myocardial contractile pathways, based on the data from (1) optically and (2) manually digitized hearts is described. The measured raw data comprised: (1) A list epi of points on an "epicardial' surface S. (2) For each selected contractile pathway f, a list of points along the contractile pathway. For any point p on a contractile pathway f, the angle of inclination alpha p = alpha p (p,f,S) is defined to be the angle (in degrees) between the tangent tp = tp(f) to the contractile pathway f at the point p and the tangent plane Tvp to the surface S at the surface point up = v(p,S) which is nearest to p. Thus alpha p is a generalization of the imbrication angle of Streeter. The angle of inclination was computed using two separate numerical methods: (1) A discrete method, applying finite differences to the raw data, to compute the tangents tp and the tangent planes Tvp, after which the results were smoothed. (2) A smoothing method in which the data was first smoothed to obtain an approximation Scpi to the epicardial surface and spline approximations to the contractual pathways f. We describe the results for two typical hearts: a manually digitized dilated pig heart and an optically digitized constricted cow heart. For each heart we first present the depths and angles of inclination of typical contractual pathways and then summarize the results in the form of histograms. The results are discussed in detail in the accompanying paper of Lunkenheimer. Redmann et al. [5], where the digitization methods are also described.

Animals↗
PubMed1997

The assessment of intramural stress alignment on the beating heart in situ using micro-ergometry: functional implications.

The main local stress transmission pathways in the left ventricular base, midportion and apex in up to seven layers have been assessed in normal dog and porcine hearts, in hypertrophied dog hearts, and in three pig hearts having undergone a temporary left ventricular outflow stricture. The rotational sensitivity of needle force probes was used to determine the focal surface-parallel direction of the myocardial tension vector. In all places investigated the orientation of the force transmission pathways differs slightly from the morphologically determined fibre alignment. Vector rotation upon an axis normal to the epicardial surface is definitely tempered as compared to fibre rotation. Alterations in the force transmission pathways assessed in hypertrophied dog hearts by micro-ergometry qualitatively confirm structural remodelling in so far as an irregularity in the transmural rotation of the main stress vector was found. The measured disparities between the alignment of the myocardial fibre weave and the direction of stress transmission both in the normal and the diseased heart is widely individual, and hence, scattering of the data is marked. However, it must also be called into consideration that the measured orientation of force vectors is that at the moment of highest developed force, only. Further investigations will elucidate if discrepancies between that force vector and morphology are less pronounced when the vector is averaged over the entire heart cycle.

Animals↗
PubMed1997

Inhomogeneities in wall stress measured by microergometry in the heart muscle in situ.

Microergometry is a method which we have developed as a tool to measure local mesh-tension within the myocardial weave at any measuring site of both ventricles and the septum on the beating heart in situ. In a mapping procedure on pig and dog hearts, both in control conditions and in the hypertrophied state after aortic banding, local mesh-tension was measured in several areas and in up to eight depths proceeding from the epicardium to the endocardium: Probe-to-fibre coupling is definitely more stable in the canine myocardium than in the porcine heart muscle, probably due to a more effective connective tissue fettering of the canine myocardial weave. The observed longitudinal gradient, with the highest tension in the base, of control dog hearts was levelled out in the hypertrophied hearts. Furthermore, in control dog hearts mesh-tension in the subepi- and subendocardial layers was higher than in the midlayers. This pronounced midlayerhypotension was smoothed in the hypertrophied hearts. Further studies will be dedicated to the question of whether the impact of ventricular size and shape on intersegmental stress transmission is determined by the Frank-Starling mechanism alone or whether protracted remodelling processes on the level of the local fibre weave cause slow coupling alterations.

Animals↗
PubMed1996

A prospective risk analysis of contemporary thoracic surgery.

OBJECTIVE: The results of surgical therapy can only be accurately judged if the patients' characteristics and their impact on the outcome are known. The purpose of this study was to identify the risk factors of contemporary thoracic surgery, which could serve as a basis for a risk-matched comparison of different surgical techniques. METHODS: The data of 15 patients' undergoing thoracic surgery were prospectively documented. The outcome of the various operative procedures applied was statistically correlated with the access procedure, sex, age, body mass, dignity of underlying disease and six concomitant diseases. RESULTS: Four patients died within 30 days of surgery (mortality: 2.6%). Morbidity comprising all complications (class I) and morbidity comprising only complications of consequence for postoperative therapy (class II) rose with the number of concomitant diseases (50%/0% with no concomitant disease, 89%/33% with more than three concomitant diseases). Univariate testing identified malignant disease (P = 0.002), male sex (P = 0.003), body mass index of less than 20 and more than 27 kg/m of the expected level according to the Quetelet rule (P = 0.013) and a combination of concomitant respiratory and cardiocirculatory disease (P = 0.022) as being associated with class I morbidity. Male sex was significantly coincident with class II morbidity (P = 0.020). Logistic regression analysis demonstrated that these characteristics also had independent influence on class I morbidity (P = 0.022, P = 0.001, P = 0.023, P = 0.028). CONCLUSION: It is concluded that these characteristics are important predictors of morbidity of thoracic surgery. If a non-randomized comparison of the outcome of thoracic operations or different access strategies like thoracotomy or thoracoscopy is intended, at least these patient features should be documented and used as a basis for matching pairs.

Adolescent↗
PubMed1995

[Hemo- and cardiodynamic effect of nifedipine in halothane or isoflurane anesthesia. An animal experiment study].

OBJECTIVE: The present experimental study on 16 acutely instrumented dogs was designed to determine the haemo- and cardiodynamic changes after an intravenous infusion of nifedipine during halothane or isoflurane anaesthesia. METHODS: General anaesthesia was induced with ketamine (10 mg/kg) and fentanyl (0.02 mg/kg) and maintained with fentanyl (0.3 micrograms/kg/min), 3:1 N2O/O2 inhalation mixture, and pancuronium (300 micrograms/kg/h). A left thoracotomy was performed and a needle force probe was placed in the left ventricular wall to measure myocardial force of contraction. A Widney gauge was placed around the left ventricle to measure left ventricular circumference changes. The animals were also monitored with left ventricular tip manometers, pulmonary arterial thermodilution catheters, and femoral arterial and venous catheters. Three hours after instrumentation baseline haemodynamic measurements were performed and repeated 30 min after either halothane 0.8 vol.% (n = 8) or isoflurane 1.5 vol.% (n = 8). Then nifedipine (10 micrograms/kg i.v.) was administered and haemodynamic measurements were repeated. RESULTS: Both volatile anaesthetic agents caused a decrease in MAP, CO, LVP, LVFS, and dP/dtmax. Heart rate, CVP, PAOP, and the diastolic diameter of the heart did not change with halothane and isoflurane. Isoflurane led to a decrease of SVR that was not seen with the administration of halothane. Nifedipine during halothane anaesthesia caused a further decrease in MAP, SVR, LVP, dP/dtmax, and LVFS compared to the already reduced values with halothane alone. However, SV did not decrease any further. If nifedipine was added to isoflurane a further decrease in CO and SV was observed despite a constant SVR. CONCLUSION: Halothane, isoflurane and nifedipine are cardiac depressant drugs. Isoflurane induces vasodilation and appears to be less cardiodepressant than halothane in the clinical situation. However, if nifedipine is added, the vasodilation caused by nifedipine offsets its own negative inotropic effect and in parts the cardiac depression of halothane. Combined with isoflurane the vasodilatory effect of nifedipine is insignificant and the negative inotropic effects of both drugs are additive resulting in a profound decrease in SV and CO.

Anesthesia, General↗
PubMed1994

High-frequency oscillation in an adult porcine model.

OBJECTIVE: Controversy exists as to whether high-frequency oscillatory ventilation can be used on babies and small laboratory animals only, or whether high-frequency oscillatory ventilation can also be efficient in the adult patient and large (> 65 kg body weight) laboratory animals. Moreover, controversy exists as to whether limitations in high-frequency oscillation efficiency are caused by the size and shape of the bronchial system, by the lack of low impedant intersegmental gas flow in lung parenchyma, or by inappropriate high-frequency ventilators and ancillary hardware. Therefore, our objective in this study using the adult pig as a model of the adult patient was to test whether the adult airway system is suited to the use of high-frequency oscillatory ventilation or whether there are geometrical, structural, or functional limitations to efficient ventilation by high-frequency oscillation. DESIGN: Prospective, controlled, randomized comparison over 8 to 16 hrs of ventilatory management. SETTING: Experimental thoracovascular surgery laboratory in a university hospital. SUBJECTS: Fifteen adult, female, house swine (weight 90 to 140 kg). INTERVENTIONS: We evaluated the ventilatory effect of a wide range of oscillation frequencies (10-15 to 35-45 Hz), tidal volumes (0.5 to 2.2 mL/kg), and bias flow volumes (10 to 70 L/min) at a mean airway pressure of 12 +/- 1 cm H2O in anesthetized and relaxed pigs who did not have lung injury. MEASUREMENTS AND MAIN RESULTS: Arterial blood gases are mainly dependent on tidal volume, frequency, and mean airway pressure. A threshold bias flow volume of 35 +/- 5 L/min is required to prevent CO2 rebreathing. In the group of lightweight animals (65 to 99 kg), the most efficient frequency band for CO2 elimination was approximately 25 Hz. The most efficient frequency band for arterial oxygenation was found to vary between individuals more than the most efficient frequency band for CO2 elimination. In the group of heavy animals (100 to 140 kg), no most efficient mean frequency could be assessed, probably because the excitation system was limited. We confirmed that tidal volume on its own had an effect on CO2 elimination ("tidal-volume effect"), although CO2 elimination was mainly determined by the product of tidal volume and oscillation frequency (oscillated minute volume), at least up to a critical frequency. Beyond that frequency, CO2 elimination could not be enhanced. The most efficient mean airway pressure in unimpaired lungs was assessed at 12 +/- 1 cm H2O. CONCLUSIONS: Adult pigs with a body weight in the range of the weight of clinical adult patients can be ventilated by high-frequency oscillation at tidal volumes smaller than, equal to, or slightly more than anatomical deadspace. The most efficient frequency for gas exchange varied between individuals. Tidal volume had an enhancing effect on CO2 elimination. The frequency dependency of PaO2 may have been related to a frequency-dependent structural remodeling of the airway system, which occurred even though the mean airway pressure was kept constant. These results demonstrate that failure of adequate ventilation by high-frequency oscillation is caused by a) CO2 rebreathing, b) the avoidance of an appropriate alveolar recruitment strategy, and c) an underpowered, high-frequency ventilatory system (oscillator) that is unable to deliver appropriate pressure oscillations. These limitations led to insufficient CO2 elimination and/or inadequate arterial oxygenation.

Animals↗