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Biomedical subjects

A Meissner

Publications and source records attributed to A Meissner.

At least 73 records · Page 4Linked to original sources
PubMed1997

[Thoracic epidural anesthesia--more than an anesthesia technique].

Thoracic epidural anaesthesia (TEA) faces growing interest as an adjuvant anaesthetic and postoperative analgesic regimen. The procedure allows a specific blockade of nociceptive reflex arches and may exert beneficial effects on stress-induced alterations of organ function. Myocardial blood flow to areas at risk is improved, and paradoxical reactions of atherosclerotic coronary arteries after sympathetic stimulation are suppressed. After cardiac surgery, TEA improved postoperative recovery and resulted in better haemodynamic stability and allowed earlier extubation. During vascular surgery, the graft occlusion rate was significantly decreased. The improved pulmonary function after TEA is due to superior pain relief which allows the patients to breathe and cough sufficiently. After upper abdominal surgery, TEA leads to improved recovery of gastrointestinal function which reduces the risk of bacterial translocation. Although lumbar epidural anaesthesia is preferred by many anaesthesiologists as there is no risk of traumatizing the spinal cord, many positive effects are forgone. With insufficient rostral spread of a lumbar epidural block above the fifth thoracic level, cardiac complications can occur due to reflex activation of sympathetic outflow in unblocked thoracic regions. When the contraindications are carefully observed, TEA can be safely performed in most patients.

Anesthesia, Epidural↗
PubMed1997

Effects of sympathetic nerve blockade on vasoconstrictive properties of nitric oxide synthase inhibition in sheep.

OBJECTIVE: Inhibition of nitric oxide synthase causes intense vasoconstriction. This effect is thought to be dependent on sympathetic nerve activity. Thus, we investigated the vasoconstrictive effects of the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) in sheep, in which a reversible sympathetic block was established by thoracic epidural anesthesia. METHODS: Sheep (n = 11) were surgically prepared for chronic study. After at least 5 days of recovery, L-NAME was continuously administered and hemodynamics were monitored. This was done in sheep with and without sympathetic blockade in randomized order. RESULTS: The vasoconstrictive effects of L-NAME were similar in sheep with and without sympathetic blockade. CONCLUSION: The obtained results suggest that the vasoconstrictive properties of nitric oxide synthase inhibitors are independent of sympathetic tone.

Anesthesia, Epidural↗
PubMed1997

Repolarization dispersion and sudden cardiac death in patients with impaired left ventricular function.

AIMS: Prolongation of repolarization dispersion measured from the 12-lead surface ECG has been associated with sudden cardiac death and ventricular tachyarrhythmia in a variety of heart disorders. This study tested the hypothesis that increased repolarization dispersion is of prognostic value in identifying chronic heart failure patients at high risk of sudden cardiac death and ventricular tachyarrhythmia. RESULTS: In 163 patients, ischaemic (n = 126) and idiopathic dilated (n = 37) cardiomyopathy with a left ventricular ejection fraction < or = 40% were diagnosed by left ventricular angiography. During follow-up (26 +/- 15 months) 24 patients died suddenly, 10 experienced ventricular tachyarrhythmia, 19 died from pump failure, six died from acute myocardial infarction, and 97 survived. Bazett's formula rate-corrected JT-interval dispersion (JTc-d) was found to be 109 +/- 23 ms in sudden cardiac death/ventricular tachyarrhythmia patients, 57 +/- 20 ms in survivors, and 55 +/- 20 ms in patients who died from pump failure or acute myocardial infarction. Both univariate and multivariate analyses showed JTc-d to be the most important independent predictor of sudden cardiac death/ventricular tachyarrhythmia. A cut-off value of 85 ms for JTc-d had a 74% positive and a 98% negative predictive accuracy in identifying patients at risk for sudden cardiac death/ventricular tachyarrhythmia. CONCLUSION: Analysis of repolarization dispersion from the 12-lead surface ECG seems to be a useful screening method for identifying chronic heart failure patients at high risk for sudden cardiac death/ventricular tachyarrhythmia.

Angiography↗
PubMed1997

The effects of thoracic epidural anesthesia on functional recovery from myocardial stunning in propofol-anesthetized dogs.

The purpose of this investigation was to examine the effects of thoracic epidural anesthesia (TEA) on myocardial stunning during propofol anesthesia. Six dogs were chronically instrumented for measurement of left atrial, aortic, and left ventricular pressure, maximal rate of increase of left ventricular pressure, and myocardial wall-thickening fraction (WTF). Myocardial blood flow was determined with colored microspheres. Experiments were performed on separate days with 1) 10 min of left anterior descending artery (LAD) ischemia during propofol anesthesia without TEA, and 2) 10 min of LAD ischemia during propofol anesthesia with TEA. WTF was measured as baseline (BL) prior to propofol anesthesia and at predetermined time points until complete recovery from stunning. Propofol anesthesia caused a significant decrease of WTF in the LAD-perfused myocardium (LAD-WTF) compared to BL in awake animals. LAD ischemia led to a further significant decrease of LAD-WTF. There were no significant differences in LAD-WTF between the two experimental conditions at any of the time points measured. TEA did not change subendocardial blood flow in nonischemic myocardium. During ischemia neither the subendocardial/subepicardial nor the occluded/normal zone blood flow ratio were affected by TEA. After myocardial ischemia during propofol anesthesia TEA does not affect functional recovery of stunned myocardium in dogs.

Anesthesia, Epidural↗
PubMed1997

Multiple coronary artery-left ventricular fistulae: haemodynamic quantification by intracoronary Doppler ultrasound.

Multiple coronary artery-left ventricular fistulae involving all three major coronary arteries are extremely rare. Clinical findings are heterogeneous but include a history of typical or atypical angina pectoris in most cases. Coronary arteriography in a 65 year old woman who presented with chest pain at rest revealed multiple fine fistulae arising from the left anterior descending, left circumflex, and right coronary arteries. Left-to-left shunt was estimated by measurements of coronary artery flow velocity with intravascular Doppler ultrasound.

Aged↗
PubMed1997

[The experiences of the Munich methadone outpatient clinics].

In 1994, two methadone outpatient treatment departments, providing a combined therapy of substitution and psychosocial care, were set up in Munich. Indication for treatment is established according to the guidelines for new treatment and diagnostic methods (NUB guidelines), focussing mainly on NUB 2.3, on account of the high psychiatric comorbidity. After 1 1/2 years a total of 102 addicts had received treatment. More than half of these patients were then hospitalized for detoxification. Substitution therapy enabled many of these patients to improve their work and home situations. A corresponding reduction in the use of drugs was also observed, especially in the case of opiates. The programme has therefore been successful similar to the results of the substitution study of Hamburg.

Adult↗
PubMed1996

Effects of dantrolene sodium on intracellular Ca2(+)-handling in normal and Ca2(+)-overloaded cardiac muscle.

We investigated the effects of dantrolene sodium on intracellular Ca2+ homeostasis in normal and Ca2+ overloaded rat cardiac muscle. In isometrically contracting rat papillary muscles loaded with the Ca2+ indicator aequorin, dantrolene (50 microM) produced a mild negative inotropic effect (28 +/- 1.8 to 21 +/- 1.1 mN/mm2; mean +/- S.E.; n = 6; P < 0.01), which was paralleled by a decrease in peak systolic [Ca2+]i (0.81 +/- 0.04 to 0.67 +/- 0.04 microM; P < 0.01). In isolated cardiac sarcoplasmic reticulum, dantrolene (50 microM) increased the initial Ca2+ uptake rate by 23% as compared to control preparations (at pCa 6.2: 46.9 +/- 1.6 to 61.1 +/- 2.2 nmol/mg per min; n = 4; P < 0.001). Intracellular Ca2+ overload was provoked in isoproterenol-pretreated (100 microM) preparations with [Ca2+]o = 5.0 mM at a stimulation rate of 1.0 Hz (n = 12). Diastolic Ca2+ oscillations and aftercontractions increased mean diastolic [Ca2+]i (0.33 +/- 0.1 to 0.56 +/- 0.1 microM) and tension (9.5 +/- 1.8 to 15.3 +/- 2.1 mN/mm2), respectively. Addition of dantrolene (50 microM) reduced the amplitude of Ca2+ oscillations and aftercontractions; mean diastolic [Ca2+]i decreased to 0.44 +/- 0.1 microM and diastolic tension to 13.5 +/- 2.2 mN/mm2. We conclude, therefore, that dantrolene sodium modifies Ca2+ handling by the myocardial sarcoplasmic reticulum, an effect that might be useful in cardiac disorders with impaired [Ca2+]i homeostasis.

Animals↗
PubMed1996

[Hypoxic pulmonary vasoconstriction].

Hypoxic pulmonary vasoconstriction (HPV) was first described by von Euler and Liljestrand in 1946 and is still the only known vascular feedback control mechanism in the lung. This technique results in a redistribution of blood flow away from poorly ventilated areas into better ventilated regions, thus reducing shunt. HPV functions as a local mechanism that acts in response to alveolar hypoxia but in the smallest areas of the lung, making it an important mechanism in all situations where ventilation perfusion mismatch occurs. to be effective, HPV needs normal pulmonary areas into which blood flow can be diverted. This explains why the efficacy of the treatment depends on the area that is vasoconstricted. The effect on PaO2 is maximal when the amount of the hypoxic lung ist 30-70%. If the area in vasoconstriction is small, the influence on PaO2 is negligible. On the other hand, when most of the lung is hypoxic, there is no significant normoxic region to which the hypoxic region can divert flow. In that case it does not matter, in terms of PaO2, whether the hypoxic region has active hypoxic pulmonary vasoconstriction or not. In this situation HPV becomes a rather detrimental mechanism, because it causes an increase in pulmonary arterial pressure. At some stage a turning point, where the gain in PaO2 is lost due to an increase in right ventricular after-load, inducing a decrease in CO. The reaction is diminished by exogenous manipulations, drugs (inhalation anesthetics, direct vasodilators), endotoxin, very low PaO2 values, vasodilating mediators and changes in the acid-base balance. Acidosis and alkalosis inhibit HPV. Factors like spontaneous or mechanical ventilation, PEEP, open or closed chest, and the type of hypoxia (atelectasis or nitrogen) have no influence on HPV. The small arteries, those less than 500 microns in diameter, were identified as the location of the hypoxic constriction. Pulmonary vascular smooth muscle cells in pure culture undergo reversible and repeated hypoxic constriction. Examination of a histological lung section emphasizes that the small arteries are closely surrounded by alveoli gas on the outside and by mixed venous blood on the inside. Thus, the response is believed to be accounted for by each smooth muscle cell in the pulmonary arterial wall responding proportionally to the local oxygen tension in its vicinity and depending on alveolar as well as mixed venous oxygen pressure. The biochemical intracellular mechanism remains unknown.

Critical Care↗
PubMed1996

Hepatic branch vagotomy enhances feeding in response to centrally elicited glucose deprivation in rats.

Intracerebroventricular (I.C.V.) administration of 2-deoxy-D-glucose (2-DG) produces glucose deprivation-induced ('glucoprivic') feeding and sympathoadrenal activation. To find out whether peripheral mechanisms modulate centrally elicited glucoprivic feeding the effect of hepatic branch vagotomy (HBV) compared with sham vagotomy (SV) on the feeding response to I.C.V.-injected 2-DG (1.2 or 2.4 mg per rat) was tested in rats fed a fat-enriched diet (18% fat). 2-DG was injected into the lateral ventricle 1 h after after dark onset, at light onset or 6 h after light onset of the 12 h light-12 h dark cycle. Apart from one (1.2 mg 2-DG injected 1 h after dark onset) out of six experiments, HBV enhanced glucoprivic feeding. This finding is consistent with the assumption that centrally elicited glucoprivic feeding is antagonized by peripheral stimuli signalled to the brain through the hepatic vagus branch.

Animals↗
PubMed1996

[Long-term results of surgical and conservative treatment of ruptures of the long biceps tendon].

INTRODUCTION: The therapeutic concept for rupture of the long biceps tendon continues to be controversially discussed. Various operative procedures compete with mostly unstructured conservative ones. QUESTION INVESTIGATED: a) Is operative therapy of the long biceps tendon rupture superior to the conservative treatment? b) For which group of patients should the operative or the conservative therapy be recommended? PATIENTS AND METHOD: The value of operative versus conservative therapy was examined based on a collective of 43 ruptures (39 patients), 31 operatively and twelve conservatively treated. The investigation comprised the following: 1) the subjective evaluation of the long-term result by the patient, 2) a thorough clinical examination including the function of the shoulder and the elbow joint and 3) an isokinetic force and endurance test on Cybex II. The results of the follow-up were evaluated by a score. RESULTS: It was found that very good but also poor results can be achieved with both operative and conservative therapy, the good results distinctly predominating in the operated collective. Statistically significant differences could not be detected because of the small number of cases and the relatively large variation range. Good results after conservative therapy require a differentiated rehabilitation program corresponding to the normal course followed after operative treatment. CONCLUSION: Since results tended to be better for the operated collective in our study, we recommend a surgical procedure for active younger patients. It seems to be of decisive importance to perform the operation as early as possible and to achieve optimal tension of the muscle by refixation of the tendon.

Adult↗
PubMed1996

[Biomechanics of the pubic symphysis. Which forces lead to mobility of the symphysis in physiological conditions?].

For estimation of the loads of fixation devices, physiological movements and acting forces at the symphysis pubis are examined. Experimentally, Walheim determined the movements of the pubic symphysis under physiological conditions (one-leg stance, walking): there is no effective mobility in the horizontal direction. During the one-leg stance he observed symphyseal mobility of up to 2.6 mm (Phi 1.2 mm) in the vertical direction and 1.3 mm (Phi 0.6 mm) in the sagittal direction. During walking he found symphyseal mobility of up to 2.2 mm (Phi 0.9 mm) in the vertical direction and 1.3 mm (Phi 0.6 mm) in the sagittal direction. Until now the forces leading to symphyseal mobility have not been estimated either experimentally or mathematically. In our experimental study we examined ten fresh cadaver anterior pelvic rings by means of a multidirectional force-mobility measurement. Maximal physiological movements, as determined by Walheim, were increasingly induced in ten equal steps, and the forces required were measured for every single step. Out of the resulting force-mobility curves for the ten cadaver specimens the mean force required (with standard deviation) was calculated for each of the ten measure points, separately for the vertical (y-) direction and sagittal (z-) direction. The values were graphically transferred, and a regression curve was created. This curve allows the acting force to be estimated for every movement of the pubic symphysis: During the one-leg stance the mean force to induce mean mobility is 169 N in vertical direction and 148 N in sagittal direction; for maximal mobility a force of 398 N in the vertical direction and 148 N in the sagittal direction is necessary. During walking, the force required to induce mean movement of the symphysis pubis is 120 N in the vertical direction and 68 N in the sagittal direction; for maximal mobility 333 N is required in the vertical direction and 136 N in the sagittal direction. For mobilization of patients with a symphyseal rupture (type Tile B 1) with partial weight-bearing, neutralization of the mean acting forces during the one-leg stance (169 N in the vertical direction, 68 N in the sagittal direction) must be achieved by an adequate fixation device. In cases where full weight bearing is desirable, such as in patients with limited compliance, stability can only be reached by neutralization of the maximal acting forces during walking (333 N in the vertical direction, 136 N in the sagittal direction).

Adult↗
PubMed1996

[Differential therapy of cardiogenic shock with dopamine/milrinone in comparison with dopamine/dobutamine].

In cardiogenic shock, combined pharmacotherapy with dopamine/dobutamine was being used as a standard regimen and was compared to dopamine/milrinone in this study. In a total of 20 patients with persistent hemodynamic depression despite mechanical ventilation plus dopamine (10-12 micrograms/kg/min) and nitroglycerin (33 micrograms/min) infusions additional therapy with dobutamine (maximal dose: 9 micrograms/kg/min; n = 10) or milrinone (0.5 microgram/kg/min; n = 10) was started. Dobutamine induced an increase of cardiac index (2.0 +/- 0.1 to 2.9 +/- 0.21/min/m2; p < 0.01; mean +/- SEM) and heart rate (96 +/- 6 to 117 +/- 5 min-1; p < 0.05) while mean arterial pressure (75 +/- 2 to 71 +/- 4 mm Hg) and pulmonary capillary wedge pressure (21 +/- 2 to 19 +/- 2 mm Hg) hardly changed. The rate-pressure product rose from 10790 +/- 684 to 13234 +/- 678 mm Hg/ min (p < 0.05). Milrinone had a comparable effect on cardiac index (2.0 +/- 0.1 to 2.6 +/- 0.1 I/min/m2; p < 0.01) but induced a minor change in heart rate (94 +/- 6 to 104 +/- 8 min-1; p < 0.05) and a more pronounced decrease in mean arterial pressure (77 +/- 2 to 65 +/- 2 mm Hg; p < 0.01) and pulmonary capillary wedge pressure (24 +/- 2 to 17 +/- 1 mm Hg; p < 0.01). The rate-pressure product declined (11033 +/- 711 to 10555 +/- 929 mm Hg/min). In comparison, dopamine/milrinone appeared to be advantageous in terms of pre- and afterload reduction and myocardial oxygen demand. However, the concomitant decline in arterial pressure might impair end-organ perfusion.

Aged↗
PubMed1995

Contractile dysfunction and abnormal Ca2+ modulation during postischemic reperfusion in rat heart.

Isolated adult rat hearts in an isovolumic nonworking Langendorff preparation were loaded with the Ca2+ indicator aequorin to investigate the effects of ischemic reperfusion on free intracellular Ca2+ concentration ([Ca2+]i) homeostasis and left ventricular (LV) contractile function. In three groups (each n = 8) that underwent 10, 20, and 30 min of ischemia, recovery of developed pressure amounted to, respectively, 63% [77 +/- 3 (SE) mmHg], 48% (56 +/- 4 mmHg), and 34% (43 +/- 4 mmHg) of preischemic control (122 +/- 5 mmHg) after 60 min of reperfusion. Diastolic pressure remained elevated at 40 +/- 4, 55 +/- 3, and 65 +/- 6 mmHg, respectively (preischemic control, 12 mmHg). During early reperfusion (0-20 min), the light transient demonstrated a prolonged time to 90% decline from peak light (t90L), which was paralleled by a delayed relaxation on the LV pressure tracing in the 10- and 20-min ischemia groups. After 60 min of reperfusion, the prolongation of t90L persisted in all groups (10-min ischemia, 89 +/- 2 ms; 20 min, 95 +/- 3 ms; 30 min, 96 +/- 2 ms; control, 82 +/- 2 ms; P < 0.05). In contrast, the LV pressure tracing was abbreviated beyond the preischemic control, indicating altered myofibrillar Ca2+ responsiveness. Diastolic [Ca2+]i was elevated after 60 min of reperfusion (10-min ischemia, 0.40 +/- 0.06 microM; 20 min, 0.48 +/- 0.04 microM; 30 min, 0.51 +/- 0.06 microM; control, 0.32 +/- 0.01 microM) and had a significant positive correlation with LV diastolic pressure (r = 0.79; P < 0.001). A positive correlation was also found for the amplitude of the Ca2+ transient and LV developed pressure (r = 0.53; P < 0.05). These findings suggest that postischemic contractile dysfunction is related to altered Ca2+ modulation with impaired [Ca2+]i homeostasis following moderate to severe reperfusion injury in the rat.

Aequorin↗
PubMed1995

[Pseudo-stenosis caused by vessel wall invagination during interventional treatment of 2 coronary vessels in a patient].

We report on a 59-year-old man who underwent a combined procedure of directional coronary atherectomy (DCA) and PTCA of significant lesions of the right coronary artery (RCA) and the left circumflex artery (LCX). Already after positioning of a standard guide wire in the right coronary artery a new excentric "pseudo-stenosis" was observed in the proximal part of the right coronary artery. Since the patient remained symptom free, a 7F DCA catheter was introduced to the stenotic area in the mid RCA, which led to an extension of the narrowing, involving the total segment proximal to the DCA catheter. Directional coronary atherectomy was performed without complications. Removal of the catheter, after successful DCA, and administration of intracoronary nitroglycerin did not relieve the proximal narrowing, which disappeared spontaneously after the guide wire was pulled out. During PTCA of the left circumflex using a standard guide wire and a 3.0 mm Monorail balloon catheter, a similar tight narrowing of the origin of the LCX was observed, which could also not be influenced by vasodilator drugs, but relieved after wire removal. Until now, this phenomenon has only been described for the right coronary artery. The reason underlying intimal folding is a shifting of the intimal layer against the medial layer of the vessel wall. Our observation firstly describes this phenomenon of "pseudo narrowing" in two different vessels in one patient. We, like other authors before, recommend that interventional therapy of these pseudo-lesions should be avoided.

Angioplasty, Balloon, Coronary↗
PubMed1995

[Long-term outcome after conservative treatment of pelvic ring injuries and conclusions for current management].

Until the early eighties conservative treatment was common even for unstable pelvic fractures. The long-term results of 114 non-operatively treated patients who had suffered a pelvic fracture (68 type A, 20 type B, 26 type C according to the classification of the ASIF) have been examined after an average time of 7.1 years after injury. 60% of cases with a stable injury of the pelvis (type A) did not suffer of any complaint. The remaining patients stated moderate pain. After conservative treatment of type B pelvic injuries 55% complained of pain or showed an impaired functional result. Former vertical-shear fractures (type C) showed worse results than type B pelvic injuries: only 15% did not suffer of any pain and 10% had no functional deficit. Patients with unstable pelvic fracture localized pain mainly in the lumbo- or iliosacral region. Radiological and CT findings suggest arthrosis, partial ancylosis and incomplete reduction of the fracture as possible reasons for unsatisfactory clinical results. As consequence of these results we nowadays proceed extended radiological examinations (a.-p.-, inlet-, outlet-views, CT) and operative reduction and internal stabilization (ORIF) of all unstable pelvic fractures.

Activities of Daily Living↗
PubMed1994

[Late results of acetabulum fractures].

Of 100 patients with acetabulum fractures treated from 1976 to 1985, 53 were followed up after a mean of 7.9 years. The results were predominantly good in patients with simple fractures, but mainly unsatisfactory in those with combination fractures. The poor results were mainly due to pain generally resulting from posttraumatic coxarthrosis (all grades 18/48) or from persistent nerve lesions (posttraumatic or postoperative 7/51) and functionally relevant ectopic ossifications (2/48). The mobility of the affected hip joint was predominantly good compared to the contralateral side. Results were best after rapid elimination of luxations in luxation fractures and early repositioning and elective internal fixation of fractures of the acetabulum to be operated on.

Acetabulum↗