W Schütz

Universität Ulm, Ulm, Baden-Wuerttemberg, Germany

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Publications (32)76.27 Total impact

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    ABSTRACT: Hepatic hypoperfusion is regarded as an important factor in the pathophysiology of perioperative liver injury. Although epidural anesthesia (EDA) is a widely used technique, no data are available about the effects on hepatic blood flow of thoracic EDA with blockade restricted to thoracic segments in humans. In 20 patients under general anesthesia, we assessed hepatic blood flow index in the right and middle hepatic vein by use of multiplane transesophageal echocardiography before and after induction of EDA. The epidural catheter was inserted at TH7-9, and mepivacaine 1% with a median (range) dose of 10 (8-16) mL was injected. Norepinephrine (NE) was continuously administered to patients who demonstrated a decrease in mean arterial blood pressure below 60 mm Hg after induction of EDA (EDA-NE group). The other patients did not receive any catecholamine during the study period (EDA group). A further 10 patients without EDA served as controls (control group). In five patients, administration of NE was necessary to avoid a decrease in mean arterial blood pressure below 60 mm Hg. Thus, the EDA-NE group consisted of five patients and the EDA group of 15. In the EDA group, EDA was associated with a median decrease in hepatic blood flow index of 24% in both hepatic veins (P < 0.01). In the EDA-NE group, all five patients showed a decrease in the blood flow index of the right (median decrease 39 [11-45] %) and middle hepatic vein (median decrease 32 [7-49] %). Patients in the control group showed a constant blood flow index in both hepatic veins. Reduction in blood flow index in the EDA group and the EDA-NE group was significant in comparison with the control group (P < 0.05). In contrast to hepatic blood flow, cardiac output was not affected by EDA. We conclude that, in humans, thoracic EDA is associated with a decrease in hepatic blood flow. Thoracic EDA combined with continuous infusion of NE seems to result in a further decrease in hepatic blood flow.
    Anesthesia and analgesia 04/2009; 108(4):1331-7. DOI:10.1213/ane.0b013e3181966e6f · 3.42 Impact Factor
  • R. Meierhenrich, W. Schütz, A. Gauss
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    ABSTRACT: In den letzten beiden Dekaden wurde zunehmend erkannt, dass die Ventrikelfunktion nicht nur durch die systolische, sondern entscheidend auch durch die diastolische Funktion bestimmt wird. Eine normale diastolische Funktion ist durch die Fähigkeit gekennzeichnet, bei normalen Füllungsdrücken ausreichende Blutvolumina in die Ventrikel aufzunehmen. Bestimmt wird die diastolische Funktion durch einen aktiven, energieverbrauchenden Prozess, die Relaxation, und durch die passiven Eigenschaften des Ventrikels, die ventrikuläre Compliance. Diagnostisch nimmt die Dopplerechokadiographie durch Analyse des transmitralen sowie des pulmonalvenösen Flussprofils und durch Quantifizierung der Exkursionen des Mitralklappenanulus eine zentrale Stellung ein. In letzter Zeit wird die Bedeutung der diastolischen Ventrikelfunktion auch im perioperativen Bereich zunehmend erkannt. Neuere Studien haben gezeigt, dass es nach kardiopulmonalem Bypass zu einer Abnahme der ventrikulären Compliance kommt. Im Zusammenhang mit einer Sepsis scheinen nicht nur Störungen der aktiven Relaxation, sondern auch Veränderungen der passiven Eigenschaften des linken Ventrikels aufzutreten. Erste Arbeiten beschäftigen sich auch mit Therapieansätzen bei Patienten mit isolierter diastolischer Dysfunktion. Over the last two decades there has been a growing recognition that cardiac function is not solely determined by systolic but also essentially by diastolic function. Left ventricular diastolic dysfunction is characterized by an impairment of ventricular filling caused either by abnormal relaxation, an active energy consuming process or decreased compliance, which is determined by passive tissue properties of the ventricle. Doppler echocardiography, including tissue Doppler imaging, has emerged as the preferred clinical tool for the assessment of left ventricular diastolic function. Recently the importance of left ventricular diastolic function is increasingly being recognized also during the perioperative period. Newer studies have shown that after cardiopulmonary bypass there is a significant decrease in left ventricular compliance. Experimental studies have demonstrated that sepsis is associated with a decrease in both active relaxation and ventricular compliance. Initial studies are also focusing on therapeutic options for patients with isolated diastolic dysfunction.
    Der Anaesthesist 11/2008; 57(11):1053-1068. DOI:10.1007/s00101-008-1457-0 · 0.74 Impact Factor
  • R Meierhenrich, W Schütz, A Gauss
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    ABSTRACT: Over the last two decades there has been a growing recognition that cardiac function is not solely determined by systolic but also essentially by diastolic function. Left ventricular diastolic dysfunction is characterized by an impairment of ventricular filling caused either by abnormal relaxation, an active energy consuming process or decreased compliance, which is determined by passive tissue properties of the ventricle. Doppler echocardiography, including tissue Doppler imaging, has emerged as the preferred clinical tool for the assessment of left ventricular diastolic function. Recently the importance of left ventricular diastolic function is increasingly being recognized also during the perioperative period. Newer studies have shown that after cardiopulmonary bypass there is a significant decrease in left ventricular compliance. Experimental studies have demonstrated that sepsis is associated with a decrease in both active relaxation and ventricular compliance. Initial studies are also focusing on therapeutic options for patients with isolated diastolic dysfunction.
    Der Anaesthesist 11/2008; 57(11):1053-68. · 0.74 Impact Factor
  • European Journal of Anaesthesiology 01/2008; 25 (Suppl 44):3-4. DOI:10.1097/00003643-200805001-00357 · 3.01 Impact Factor
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    ABSTRACT: The purpose of this study was to analyze left ventricular diastolic function in patients undergoing aortic aneurysm repair and to investigate the effects of laparotomy and aortic cross-clamping on diastolic function. Prospective clinical study. University hospital. Forty-five consecutive patients undergoing open aortic aneurysm repair. Left ventricular diastolic function and hemodynamic variables were evaluated using transesophageal Doppler echocardiography and a pulmonary artery catheter at baseline, after laparotomy, and at 1 and 10 minutes after cross-clamping. Diastolic function was determined by Doppler derivatives of mitral inflow (E/A ratio, deceleration time of early inflow) and pulmonary venous flow (S/D ratio). Twenty of 39 patients revealed signs of diastolic dysfunction at baseline. Of these 20 patients, 14 displayed delayed relaxation and 6 displayed a pseudonormal filling pattern. Patients with pseudonormal filling exhibited a lower stroke volume (p = 0.02) and cardiac index (p < 0.01) in comparison to patients with normal diastolic function. Laparotomy was associated with an improvement of diastolic function in 9 of 20 patients with preexisting diastolic dysfunction. Only 3 patients suffered impairment of diastolic function after cross-clamping. The hemodynamic response to cross-clamping did not differ between patients with normal and abnormal diastolic function. About 50% of patients undergoing aortic aneurysm repair exhibit signs of diastolic dysfunction. The majority of these patients showed delayed relaxation. Patients with pseudonormal filling displayed a significantly lower cardiac index. Laparotomy resulted in an improvement in diastolic function in about half of patients with preexisting diastolic dysfunction. The effects of cross-clamping on diastolic function are minimal.
    Journal of Cardiothoracic and Vascular Anesthesia 04/2005; 19(2):165-72. DOI:10.1053/j.jvca.2005.01.025 · 1.48 Impact Factor
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    ABSTRACT: Conflicting results have been published about the effects of carbon dioxide (CO(2)) pneumoperitoneum on splanchnic and liver perfusion. Several experimental studies described a pressure-related reduction in hepatic blood flow, whereas other investigators reported an increase as long as the intraabdominal pressure (IAP) remained less than 16 mm Hg. Our goal in the present study was to investigate the effects of insufflated CO(2) on hepatic blood flow during laparoscopic surgery in healthy adults. Blood flow in the right and middle hepatic veins was assessed in 24 patients undergoing laparoscopic surgery by use of transesophageal Doppler echocardiography. Hepatic venous blood flow was recorded before and after 5, 10, 20, 30, and 40 min of pneumoperitoneum, as well as 1 and 5 min after deflation. Twelve patients undergoing conventional hernia repair served as the control group. The induction of pneumoperitoneum produced a significant increase in blood flow of the right and middle hepatic veins. Five minutes after insufflation of CO(2) the median right hepatic blood flow index increased from 196 mL/min/m(2) (95% confidence interval (CI), 140-261 mL/min/m(2)) to 392 mL/min/m(2) (CI, 263-551 mL/min/m(2)) (P < 0.05) and persisted during maintenance of pneumoperitoneum. In the middle hepatic vein the blood flow index increased from 105 mL/min/m(2) (CI, 71-136 mL/min/m(2)) to 159 mL/min/m(2) (CI, 103-236 mL/min/m(2)) 20 min after insufflation of CO(2). After deflation blood flow returned to baseline values in both hepatic veins. Conversely, in the control group hepatic blood flow remained unchanged over the entire study period. We conclude that induction of CO(2) pneumoperitoneum with an IAP of 12 mm Hg is associated with an increase in hepatic perfusion in healthy adults.
    Anesthesia & Analgesia 03/2005; 100(2):340-7. DOI:10.1213/01.ANE.0000143566.60213.0A · 3.42 Impact Factor
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    ABSTRACT: To evaluate the efficacy of intraoperative transesophageal echocardiography (TEE) as an adjunctive measure in guiding the implantation of endoluminal stent-grafts in the thoracic aorta. TEE was used in 21 of 30 patients (27 men; median age 70 years; range 19-77) undergoing implantation of Excluder or Talent stent-grafts for management of 11 type B aortic dissections, 7 thoracic aortic aneurysms, 2 traumatic thoracic aortic ruptures, and an aortic coarctation. We evaluated the ability of TEE to provide evidence of (1) correct placement of the guidewire within the true lumen, (2) reduction in blood flow in the false lumen following stent deployment, and (3) early complications. Definite identification of the true lumen and a reliable evaluation of the position of the stent-graft guidewire during advancement were possible in all patients. Reduction of blood flow within the false lumen following deployment of the stent-graft was visualized in >70% of patients with aortic dissection. In the patient with aortic coarctation, TEE recognized the acute onset of aortic dissection following stent dilation, which resulted in immediate management with an additional stent. The intraoperative use of TEE in the implantation of stent-grafts in the thoracic aorta is not significantly invasive and is easily employed. It permits excellent evaluation of the correct placement of the stent guidewire and, in patients with aortic dissection, intraoperatively visualizes effective blood flow reduction in the false lumen following stent-graft deployment. Its ability to recognize early complications may indicate the need for additional maneuvers during the surgical procedure.
    Journal of Endovascular Therapy 06/2002; 9 Suppl 2:II14-9. DOI:10.1583/1545-1550-9.sp3.14 · 3.59 Impact Factor
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    Critical Care 03/2002; 6:1-2. DOI:10.1186/cc1656 · 5.04 Impact Factor
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    ABSTRACT: The role of multi-plane transoesophageal echocardiography (TOE) in the visualization of the three main hepatic veins and acquisition of Doppler sonography curves has not been established. We have studied this diagnostic option of TOE in 34 patients during general anaesthesia. The findings were compared with the results of conventional transabdominal sonography (TAS). Using TOE, each of the three main hepatic veins could be visualized in all patients. In contrast, TAS allowed adequate two-dimensional visualization of the right, middle, and left hepatic vein in only 97%, 85%, and 61% of the patients, respectively. Adequate Doppler tracings of the right and middle hepatic vein could be obtained in 100% and 97% of the patients by TOE and in 91% and 50% of the patients by TAS. Doppler tracings of the left hepatic vein could only be acquired in 18% of the patients by TOE, but in 47% of the patients by TAS. As blood flow may be calculated from the diameter of the vessel, velocity time integral of the Doppler curve and heart rate, TOE may provide an interesting non-invasive tool to monitor blood flow in the right and middle hepatic vein.
    BJA British Journal of Anaesthesia 12/2001; 87(5):711-7. DOI:10.1093/bja/87.5.711 · 4.35 Impact Factor
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    ABSTRACT: Objectives: Total hepatic venous blood flow is determined by the common hepatic arterial blood flow and the venous outflow from stomach, spleen, pancreas, small intestine, and bowel, collected by the portal vein, and thus represents overall splanchnic perfusion. We investigated whether transesophageal echography (TEE) can provide a method for bedside assessment of hepatic venous blood flow useful as a noninvasive method for measuring splanchnic perfusion in clinical practice. Design and setting Experimental study in 15 anesthetized and ventilated pigs in an animal research laboratory. Interventions: TEE-derived calculations of hepatic venous blood flow were compared with liver blood flow measurements using perivascular ultrasound flow probes surgically positioned on portal vein and common hepatic artery. Parameters were determined at baseline and after modulating splanchnic perfusion by either PEEP maneuver (15 cmH2O) or intravenous epinephrine (0.1 g kg-1 min-1). Measurements and results: Diameter (d) and velocity time integral (VTI) of all three hepatic veins were determined by TEE, heart rate (HR) was derived from electrocardiography and flow subsequently calculated as Q=&#63(d/2)20.57VTIHR. Regression analysis of matched TEE and flow probe values showed a significant linear relationship (r2=0.698). Bias analysis revealed a systematic underestimation of liver blood flow by TEE, possibly due to use of 0.57 as correction factor for mean velocity, while changes in liver blood flow were reliably detected. Conclusion: TEE offers a noninvasive approach for monitoring hepatic perfusion and may be used in patients.
    Intensive Care Medicine 02/2001; 27(3):580-585. DOI:10.1007/s001340100859 · 5.54 Impact Factor
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    ABSTRACT: The value of exercise electrocardiography in the prediction of perioperative cardiac risk has yet to be defined. This study was performed to determine the predictive value of exercise electrocardiography as compared with clinical parameters and resting electrocardiography. A total of 204 patients at intermediate risk for cardiac complications prospectively underwent exercise electrocardiography before noncardiac surgery. Of these, 185 were included in the final evaluation. All patients underwent follow-up evaluation postoperatively by Holter monitoring for 2 days, daily 12-lead electrocardiogram, and creatine kinase, creatine kinase MB, and troponin-T measurements for 5 days. Cardiac events were defined as cardiac death, myocardial infarction, minor myocardial cell injury, unstable angina pectoris, congestive heart failure, and ventricular tachyarrhythmia. Potential risk factors for an adverse event were identified by univariate and multivariate logistic regression analysis. Perioperative cardiac events were observed in 16 patients. There were 6 cases of myocardial infarction and 10 cases of myocardial cell injury. The multivariate correlates of adverse cardiac events were definite coronary artery disease (odds ratio, 8.8; 95% confidence interval [CI], 1.1--73.1; P = 0.04), major surgery (odds ratio, 4.7; 95% CI, 1.3--16.3; P = 0.02), reduced left ventricular performance (odds ratio, 2.0; 95% CI, 1.1--3.8; P = 0.03), and ST-segment depression of 0.1 mV or more in the exercise electrocardiogram (odds ratio, 5.2; 95% CI, 1.5--18.5; P = 0.01). A combination of clinical variables and exercise electrocardiography improved preoperative risk stratification. This prospective study shows that a ST-segment depression of 0.1 mV or more in the exercise electrocardiogram is an independent predictor of perioperative cardiac complications.
    Anesthesiology 02/2001; 94(1):38-46. DOI:10.1097/00000542-200101000-00011 · 6.17 Impact Factor
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    ABSTRACT: Noninvasive cardiokymography has been further developed to be able to record wall motion abnormalities during exercise. The study was designed to evaluate the diagnostic accuracy of stress cardiokymography and electrocardiography in the diagnosis of coronary artery disease. 223 patients were included in a prospective investigation using a newly developed computerized cardiokymography device. Sensitivity, specificity, and positive predictive value were 61, 69 and 90% for exercise cardiokymography, and 57, 74 and 91% for exercise electrocardiography, respectively. There was no statistically significant difference between cardiokymography and electrocardiography. The combination of electrocardiography and cardiokymography did not produce a significant improvement in diagnostic accuracy in comparison to exercise electrocardiography alone.
    Cardiology 02/2001; 96(2):100-5. DOI:10.1159/000049091 · 2.04 Impact Factor
  • A Gauss, T Anhäupl, W Schütz
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    ABSTRACT: Myocardial function is determined by preload, afterload, contractility and heart rate. Pathologic changes of these variables may result in decrease of blood pressure, acute heart failure or cardiogenic shock. Hyperdynamic septic shock is associated with systemic hypotension despite increased cardiac output. Mediators of sepsis induce both myocardial depression and pulmonary arterial hypertension. Moreover, sepsis is characterized by microcirculatory disturbances and dysbalance in regional oxygen delivery and consumption. Severe systemic hypotension is a symptom often requiring catecholamine therapy to restore systemic circulation and to avoid organ damage. As the use of catecholamines is not a causal therapy administration should be limited to an initial measure until correction of the underlying abnormalities can be achieved. Different etiologies of shock as well as diseases requiring specific interventions as pulmonary embolectomy, systemic lysis or coronary angioplasty have to be considered. First line intervention consists of optimizing preload by fluid resuscitation as appropriate and use of dopamine (4-12 micrograms/kg.min) as primary catecholamine to increase contractility and blood pressure. In acute left heart failure inotropic support with dobutamine (4-12 micrograms/kg.min) or epinephrine (0.05-1 microgram/kg.min) may be necessary, frequently combined with a vasodilator (sodium nitroprusside 0.2-5 micrograms/kg.min or nitroglycerine 0.5-2.5 micrograms/kg.min) or phosphodiesterase-III-inhibitor (milrinone 0.3-0.8 microgram/kg.min). In right heart failure norepinephrine is preferred to increase coronary perfusion pressure. Hyperdynamic septic shock with decreased vascular resistance is treated with norepinephrine to restore mean arterial pressure and to improve right ventricular dysfunction induced by pulmonary hypertension.
    ains · Anästhesiologie · Intensivmedizin 04/2000; 35(3):131-6. DOI:10.1055/s-2000-10851 · 0.34 Impact Factor
  • W Schütz, T Anhäupl, A Gauss
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    ABSTRACT: All involuntary innervated structures of the body are controlled by the sympathetic and parasympathetic nervous system. Adrenaline, noradrenaline and dopamine are endogenous catecholamines binding to adrenergic and dopaminergic receptors, respectively, to mediate their clinical effects. Adrenoceptors are classified as alpha 1, alpha 2, beta 1 and beta 2 subtypes which were even further subcharacterized the recent years. Adrenoceptors are membrane proteins interacting with the agonist and, thus, inducing G-protein mediated intracellular effects. Adrenaline induces an extensive increase of heart rate and stroke volume mediated by beta-adrenoceptors and significantly enhances peripheral vascular resistance by alpha-adrenoceptor stimulation, when administered beyond 0.1 microgram/kg.min. In contrast, the clinical effects of noradrenaline are predominantly characterized by alpha-adrenoceptor stimulation resulting in a less pronounced increase of heart rate. Dopamine, less potent on adrenoceptors, shows additional effects on renal as well as on splanchnic circulation mediated by dopaminergic receptors. Dobutamine, primarily acting on beta-adrenoceptors, results in positive inotropic effects without an increase in vascular resistance. Dopexamine, a synthetic catecholamine, induces vasodilation via beta 2-adrenoceptor stimulation and potentially increases splanchnic blood flow by additional effects on dopaminergic receptors. Isoproterenol, the classical beta-adrenoceptor agonist, mediates positive inotropic effects and causes a major increase in heart rate and a significant decrease of systemic vascular resistance. Independent on adrenoceptors, phosphodiesterase-III-inhibitors exert positive inotropic and vasodilating activity by an increase in intracellular cAMP concentration induced by inhibition of cAMP hydrolysis.
    ains · Anästhesiologie · Intensivmedizin 03/2000; 35(2):67-81. · 0.34 Impact Factor
  • W. Schütz, T. Anhäupl, A. Gauss
    ains · Anästhesiologie · Intensivmedizin 01/2000; 35(2):67-81. DOI:10.1055/s-2000-10848 · 0.34 Impact Factor
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    ABSTRACT: Complete heart block is dreaded perioperatively in patients with chronic bifascicular or left bundle branch block (LBBB) and additional first-degree A-V block. Our aim was to investigate the necessity as well as the efficacy and safety of transcutaneous pacing in the perioperative setting. Thirty-nine consecutive patients with asymptomatic chronic bifascicular block or LBBB and prolongation of the P-R interval scheduled to undergo surgery under anesthesia were prospectively enrolled in the study. Preoperatively, a transcutaneous pacemaker (PACE 500 D, Osypka Co.) was applied; its efficacy was checked with intra-arterial blood pressure measurement; the pain level was recorded. Additionally, 24-h Holter monitoring (CM2, CM5) was applied. Occurrences of a block progression or a bradycardia of <40 beats/min with hemodynamic impairment were the defined end points. Thirty-seven of the 39 patients (95%) could be successfully stimulated with a median current strength of 70 mA; whereby 33 of the 39 patients felt moderate to severe pain. There was no perioperative block progression. Three cases of brady-cardia of <40 beats/min with a critical drop in blood pressure occurred; but these patients were successfully treated with drug therapy without pacemaker stimulation. The perioperative application and testing of the pacemaker was safe and could be performed in nearly all patients successfully. However, we do not consider a routine prophylactic transcutaneous placement in patients with chronic bifascicular or LBBB and additional first-degree A-V block justified. Nevertheless, appropriate drugs and temporary pacemaker equipment should be easily accessible.
    Acta Anaesthesiologica Scandinavica 09/1999; 43(7):731-6. DOI:10.1034/j.1399-6576.1999.430708.x · 2.31 Impact Factor
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    ABSTRACT: There are many closed-loop control systems for muscle relaxants reported, but only a few could cope with the introduction of the latest shorter acting neuromuscular blocking drugs. These new muscle relaxants such as mivacurium require a fast adapting closed-loop system for controlling an adequate infusion. After approval of the local ethics committee and having the patients' informed consent a total number of 75 patients [ASA I and II] were included in the study and assigned either to a training-, prediction-, prediction-/feedback- or a validation phase, as needed. Anaesthesia was induced and maintained with propofol in a TCI-mode with a plasma level of 3 to 5 micrograms/ml and 0.1 mg fentanyl boli as needed in all patients. In the last validation phase, having 20 patients, the prediction error and the error of the whole system was taken and analysed. A closed-loop system using a neural network as a predictor could be established. In the final validation phase consisting of 20 patients the mean square prediction error was found to be 0.1% +/- 0.2% [mean +/- SD]. The mean square error of the whole system was 0.55% +/- 0.59% [mean +/- SD]. A closed-loop system for control of a mivacurium infusion could be established. The system proofed to be reliable for a closed-loop infusion of mivacurium in order to maintain a predefined degree of neuromuscular blockade of 95% during routine surgery. The performance of the described controller is comparable to all recent attempts and could therefore be useful for scientific studies. It should be further validated and established for other muscle relaxants, as well.
    Der Anaesthesist 04/1999; 48(3):157-62. · 0.74 Impact Factor
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    ABSTRACT: In den vergangenen Jahren wurden unterschiedliche closed-loop-Systeme mit modell-prädiktivem Charakter zur Regelung von Muskelrelaxanzien beschrieben. Seit der klinischen Einführung von Mivacurium ist eine dank seiner kurzen Halbwertszeit für den Regelungsansatz sehr geeignete Substanz verfügbar, deren Dauerinfusion bisher nur von wenigen Systemen geregelt werden kann. Der Einsatz eines neuronalen Netzwerks als Prädiktor für eine solche Regelung soll in der vorliegenden Arbeit untersucht werden. Methodik. 75 Patienten, die sich einem abdominal chirurgischen Eingriff in Vollnarkose unterziehen mußten, wurden nach den Erfordernissen der Synthese des neuronalen Netzwerks der Trainings-, reinen Prädiktions-, der Prädiktions/Regelungs- und der Validierungsphase zugeteilt. Eine standardisierte Narkose wurde mit Propofol in einem TCI-Modus mit 3–5µg/ml und 0,1mg Fentanylboli aufrechterhalten. Die Regelung des Systems im Hinblick auf Prädiktions- bzw. gesamt Regelungsfehler wurde bei den 20 Patienten mit einem T1-Wert von 5% in der Validierungsphase statistisch untersucht. Ergebnisse. Es konnte eine Regelung mit einem neuronalen Netzwerk als Prädiktor zur Regelung einer Mivacuriuminfusion synthetisiert werden. Das Quadrat des gemittelten Prädiktionsfehlers über alle 20 Patienten der Validierungsphase lag bei 0,1% mit einer Standardabweichung von 0,2%. Die Abweichung der Sollgröße von der Istgröße wurde gemessen. Hier wurde der tatsächliche T1-Wert vom Ziel T1-Wert [ 5% bzw. 95%ige Blockade] berechnet. Der mittlere quadratische Fehler des gesamten Systems betrug hierbei 0,55%, die Standardabweichung 0,59%. Schlußfolgerung. Der Einsatz eines neuronalen Netzwerks erlaubt es, eine Mivacuriuminfusion exakt zu steuern und damit die neuromuskuläre Blockade über den Zeitraum einer Operation auf einem vorgegebenen Relaxationsniveau zu halten. Die Ergebnisse sind mit denen anderer Reglungsansätze vergleichbar, bei einer deutlich verbesserten Prädiktionsfunktion. Der Einsatz dieses Systems ist im Rahmen von wissenschaftlichen Studien, die eine konstante Relaxationstiefe erfordern, denkbar. Eine Ausweitung auf andere Muskelrelaxanzien wäre auch wünschenswert. There are many closed-loop control systems for muscle relaxants reported, but only a few could cope with the introduction of the latest shorter acting neuromuscular blocking drugs. These new muscle relaxants such as mivacurium require a fast adapting closed-loop system for controlling an adequate infusion. Methods. After approval of the local ethics committee and having the patients’ informed consent a total number of 75 patients [ ASAI and II] were included in the study and assigned either to a training-, prediction-, prediction-/feedback- or a validationphase, as needed. Anaesthesia was induced and maintained with propofol in a TCI-mode with a plasma level of 3 to 5µg/ml and 0.1mg fentanyl boli as needed in all patients. In the last validation phase, having 20 patients, the prediction error and the error of the whole system was taken and analysed. Results. A closed-loop system using a neural network as a predictor could be established. In the final validation phase constisting of 20 patients the mean square prediction error was found to be 0.1%±0.2% [ mean±SD]. The mean square error of the whole system was 0.55%±0.59% [ mean±SD]. Conclusions. A closed-loop system for control of a mivacurium infusion could be established. The system proofed to be reliable for a closed-loop infusion of mivacurium in order to maintain a predefined degree of neuromuscular blockade of 95% during routine surgery. The performance of the described controller is comparable to all recent attempts and could therefore be useful for scientific studies. It should be futher validated and esthablished for other muscle relaxants, as well.
    Der Anaesthesist 02/1999; 48(3):157-162. DOI:10.1007/s001010050682 · 0.74 Impact Factor
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    ABSTRACT: The incidence of perioperative bradyarrhythmias in patients with bifascicular or left bundle branch block (LBBB) and the influence of an additional first-degree atrioventricular (A-V) block has not been evaluated with 24-h Holter electrocardiographic monitoring. Therefore the authors assessed the rate of block progression and bradyarrhythmia in these patients. Patients (n = 106) with asymptomatic bifascicular block or LBBB with or without an additional first-degree A-V block scheduled for surgery under general or regional anesthesia were enrolled prospectively. Three patients were excluded. Of the 103 remaining, 56 had a normal P-R interval and 47 had a prolonged one. Holter monitoring (CM2, CM5) was applied to each patient just before induction of anesthesia and was performed for 24 h. The primary endpoint of the study was the occurrence of block progression. As secondary endpoints, bradycardias < 40 beats/min with hemodynamic compromise (systolic blood pressure < 90 mmHg) or asystoles > 5 s were defined. Block progression to second-degree A-V block and consecutive cardiac arrest occurred in one case of LBBB without a prolonged P-R interval Severe bradyarrhythmias with hypotension developed in another eight patients: asystoles > 5 s occurred in two cases and six patients had bradycardias < 40/min. Pharmacotherapy was successful in these eight patients. There was no significant difference for severe bradyarrhythmias associated with hemodynamic compromise between patients with and without P-R prolongation (P = 1.00). In patients with chronic bifascicular block or LBBB, perioperative progression to complete heart block is rare. However, the rate of bradyarrhythmias with hemodynamic compromise proved to be relevant. Because an additional first-degree A-V block did not increase the incidence of severe bradyarrhythmias and pharmacotherapy by itself was successful in nearly all cases, routine prophylactic insertion of a temporary pacemaker in such patients should be questioned.
    Anesthesiology 04/1998; 88(3):679-87. DOI:10.1097/00000542-199803000-00019 · 6.17 Impact Factor
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    ABSTRACT: To investigate the impact of arterial hypertension on cardiac function during aortic cross-clamping and declamping. Prospective study. University hospital. Twenty treated hypertensive males with slight left ventricular hypertrophy and 10 normotensive controls undergoing elective repair of an abdominal aortic aneurysm. Using transesophageal echocardiography, the mitral inflow profile was evaluated during aortic cross-clamping and declamping. During the clamping period, the ratio of peak atrial to peak early filling velocity (PA/PE) was significantly higher in the hypertensive patients. One minute after aortic cross-clamping, mean arterial pressure (MAP) and pulmonary artery occlusion pressure significantly increased in the hypertensive patients, whereas they did not change in the normotensive group. Cardiac index and heart rate significantly decreased after cross-clamping, and increased after clamp release in both groups. PA/PE significantly dropped in both groups after aortic declamping, and returned to baseline values thereafter. MAP also decreased significantly in both groups after clamp release, but the fall of MAP tended to be more pronounced in the hypertensive patients. In the treated hypertensive patients, more pronounced hemodynamic and echocardiographic responses to aortic cross-clamping probably mirror the altered diastolic left ventricular function in these patients. With respect to intraoperative management, however, the treated hypertensive patients did not react grossly differently from the normotensive controls.
    Journal of Cardiothoracic and Vascular Anesthesia 03/1998; 12(1):33-7. DOI:10.1016/S1053-0770(98)90052-0 · 1.48 Impact Factor