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Biomedical subjects

H Schobel

Publications and source records attributed to H Schobel.

At least 19 recordsLinked to original sources
PubMed2004

[Realistic early and late results after otosclerosis surgery and presentation of a technique involving almost no complications].

Although the modern technique of otosclerosis surgery introduced by John Shea on 1st May 1956 has already been used throughout the world for almost fifty years it has not been possible to bring in line the differing opinions of surgeons concerning the optimum operation technique, the problems of the fenestration of the footplate, material and form of stapes replacement prosthetics and kind and place of their anchoring on the incus. Moreover, there is considerable disagreement among surgeons on a realistic evaluation of the findings of early and late results. During the last few decades otosclerosis surgery has become the hallmark of modern ear surgery and has been practiced in very highly specialized departments as well as in outpatient departments. The author, who has been very active in otosclerosis surgery since 1959-since 1979 with a modified personal technique-, wishes to prove that it is both meaningful and essential to modify the operation technique further, which is based on his own experiences and on more than 100 international publications. In this paper he presents his modified method, which has been tested on 1800 ears since 1979, as well as the results, achieved in this way.

Auditory Threshold↗
PubMed2002

Influence of antihypertensive medication on aldosterone and renin concentration in the differential diagnosis of essential hypertension and primary aldosteronism.

OBJECTIVE: Antihypertensive drugs influence the neurohumoral cardiovascular system and the concentration of hormones involved in blood pressure regulation. Little is known, however, about the extent to which various antihypertensive drugs influence cardiovascular hormone concentrations and thus disturb the differential diagnosis of hypertension in clinical practice. In this study we compare the impact of different antihypertensive medicaments on the renin-angiotensin-aldosterone system in patients with essential hypertension who are screened for primary aldosteronism. DESIGN AND SUBJECTS: We analysed serum aldosterone (SAC) and plasma renin concentration (PRC) in 37 normotensive controls, 144 hypertensive patients with essential hypertension, and 19 patients with primary aldosteronism. Patients were on different treatment regimens such as single drug or combination therapy with beta-blockers, angiotensin-converting enzyme (ACE) inhibitors or angiotensin II subtype 1 (AT1) receptor antagonists, calcium channel blockers, spironolactone and no treatment. RESULTS: In patients with essential hypertension, beta-blocker therapy (n = 47) led to a highly significant suppression of renin, whereas serum levels of aldosterone were not significantly altered. ACE inhibitors and AT1 receptor antagonists (n = 55) decreased aldosterone levels only to a minor extent. Calcium channel blockers (n = 23) had no significant influence on SAC or PRC. In patients with primary aldosteronism treated with spironolactone (n = 8), renin escaped suppression and reached very high levels. CONCLUSION: Beta-blockers and aldosterone antagonists have the strongest impact on the renin-angiotensin system. The decrease in renin concentration by beta-blockers leads to an increase in the ratio of aldosterone to renin, and thus to false-positive results in patients with essential hypertension. Calcium channel blockers, and probably also ACE inhibitors and AT1 receptor antagonists alone or in combination, may be continued during screening for primary aldosteronism by determination of renin and aldosterone concentration.

Adrenergic beta-Antagonists↗
PubMed2002

Ratio of serum aldosterone to plasma renin concentration in essential hypertension and primary aldosteronism.

The ratio of serum aldosterone to plasma renin activity (PRA) has been proposed as sensitive screening method in the diagnosis of primary aldosteronism under random conditions. However, the method for determination of renin activity is hampered by the necessity of ice cooling during storage and transport. The present study was therefore conducted to examine the ratio of serum aldosterone to plasma renin concentration (ARR) and its usefulness in diagnosis of primary aldosteronism under ambulatory conditions and given antihypertensive medication. 146 patients with arterial hypertension who consecutively attended the outpatient clinic were studied prospectively. Patients with secondary hypertension besides primary aldosteronism were not included in the series. 37 normotensive patients served as control. Also, 17 patients with known primary aldosteronism were retrospectively examined. Among the hypertensive group 2 patients with Conn's syndrome were newly detected (1.4%). ARR was 7.92 +/- 6.04 [pg/ml]/[pg/ml] in normotensive controls (range from 2.03 to 26.98), 14.61 +/- 18.50 [pg/ml]/[pg/ml] in patients with essential hypertension (n = 144, range from 0.41 to 115.45) and 155.92 +/- 127.84 [pg/ml]/[pg/ml] in patients with primary aldosteronism (n = 19, range from 6.75 to 515). 17 of the 19 patients with Conn's syndrome had an ARR of more than 50. Under ongoing drug treatment this represents a sensitivity of 89% and a specificity of 96%. Sensitivity decreased to 84% and specificity increased to 100% when a second criteria (aldosterone > or = 200 pg/ml) was included. In summary, ARR using renin concentration is a useful screening parameter for primary aldosteronism.

Adult↗
PubMed1999

Hyper-responsiveness to angiotensin II is related to cardiac structural adaptation in hypertensive subjects.

BACKGROUND: Angiotensin II has been found to be a growth stimulating factor for myocardial cells. In humans, angiotensin II infusion causes vasoconstriction in systemic and renal vasculature and leads to aldosterone secretion. Our hypothesis was that hyper-responsiveness to angiotensin II is related to left ventricular mass in human essential hypertension. METHODS AND RESULTS: In 30 normotensive individuals and 30 subjects with mild essential hypertension (white men, mean age 26+/-3 years), the responsiveness to angiotensin II was assessed by measuring changes in mean arterial pressure, renal blood flow, glomerular filtration rate and aldosterone secretion in response to i.v. angiotensin II infusion (0.5 and 3.0 ng/kg per min). The provoked changes to angiotensin II infusion were similar in the normotensive and hypertensive group with the exception of an exaggerated increase in mean arterial pressure in hypertensives (14+/-5 versus 10+/-5 mm Hg, P<0.001 at 3.0 ng/kg per min angiotensin II). The increase in mean arterial pressure was correlated with left ventricular mass in hypertensive subjects (angiotensin II 0.5 ng/kg per min: r = 0.49, P<0.005; angiotensin II 3.0 ng/kg per min: r = 0.35, P<0.05); no such correlation was found in the normotensive group. After taking into account baseline mean arterial pressure and body mass index, the increase in mean arterial pressure to angiotensin II 0.5 ng/kg per min was still correlated with left ventricular mass (partial r = 0.50, P<0.01). Similarly, the change of glomerular filtration rate but not of renal blood flow in response to angiotensin II 0.5 ng/kg per min was correlated with left ventricular mass, (r = 0.42, P<0.02) in the hypertensive group but not in the normotensive one. This relationship remained significant even after taking baseline glomerular filtration rate, mean arterial pressure and body mass index into account (partial r = 0.43, P<0.05). CONCLUSION: Hyper-responsiveness to angiotensin II is related to an increased left ventricular mass in hypertensive subjects independent of blood pressure.

Adult↗
PubMed1998

Impact of dietary sodium intake on left ventricular diastolic filling in early essential hypertension.

AIMS: Dietary sodium intake modulates left ventricular hypertrophy in established essential hypertension independent of blood pressure level. We conducted this study to elucidate the relationship between sodium intake and left ventricular structural or functional changes in early essential hypertension. METHODS: Forty-four young male patients (age 25.9 +/- 2.6 years) with mild essential hypertension that had never been treated and 45 normotensive male control subjects of similar age were examined. Dietary sodium intake was measured from 24 h urinary sodium excretion, blood pressure from 24 h ambulatory monitoring (SpaceLabs 90207), left ventricular structure from 2-D guided M-mode echocardiography, and diastolic filling of the left ventricle (as the main compound of diastolic function in a young population) by pulse-wave Doppler sonography. RESULTS: In hypertensive patients, daily sodium excretion correlated with the ratio of late (A) to early (E) maximum velocity (A/E; r = + 0.27, P = 0.07), velocity time integrals (A/E; r = + 0.54, P < 0.001) as well as atrial contribution, as a percent of left ventricular filling (VH ATCO; r = + 0.52, P < 0.001) independent of heart rate, whereas the opposite correlations were observed in normotensive (all P < 0.001). Stepwise multiple regression analysis confirmed these results. Sodium excretion emerged as the strongest independent determinant of impaired diastolic filling in hypertensive patients (velocity time integrals A/E: R(2) = 0.49, beta = 0.57, P = 0.0001; VH ATCO: R(2) = 0.48, beta = + 0.56, P < 0.0001; Vmax A/E: ns). In normotensive subjects, sodium excretion was a similar strong, but inverse determinant of diastolic filling (velocity time integrals A/E: R(2) = 0.40, beta = -0.43, P = 0.0028). Heart rate was a strong determinant of diastolic filling in hypertensive patients (beta = +0.55, P = 0.0002) and in normotensive subjects (beta = + 0.34, P = 0.011). Left ventricular mass and end-diastolic volume index were not related to diastolic filling in either group. CONCLUSION: In early essential hypertension, sodium excretion is correlated with impaired left ventricular diastolic filling independent of left ventricular mass. The renin-angiotensin-aldosterone-aldosterone system might be a mediator of the observed correlation.

Adult↗
PubMed1997

Is endothelial function of the radial artery altered in human essential hypertension?

There is controversy over whether endothelial function is impaired in human essential hypertension. All studies to date have used measurements of forearm blood flow by plethysmography to assess endothelium-dependent vasodilation and endothelial function. In contrast to these studies, which have focused on resistance vessels, we have determined what effects the endothelium has on underlying smooth muscle cells in conduit arteries by measuring arterial compliance of the radial arteries (change in diameter of radial artery over pressure for each arterial pulse). In 13 normotensive healthy subjects and 11 young patients with essential hypertension, arterial compliance of the radial artery was assessed directly with a new high-precision ultrasonic device (NIUS 02) after infusion of acetylcholine (endothelium-dependent response) or sodium nitroprusside (endothelium-independent response). Arterial compliance of the radial artery was similar at baseline and with increasing doses of acetylcholine and sodium nitroprusside in normotensive and in hypertensive subjects. The increase in arterial compliance from baseline at each individual concentration of acetylcholine and sodium nitroprusside was the same in both normotensive and hypertensive subjects. However, after a single oral dose of a combination of the angiotensin converting enzyme inhibitor spirapril and the calcium entry blocker isradipine, the increase in arterial compliance in response to the maximum dose of intraarterial acetylcholine was enhanced in normotensives (0.38 +/- 1.23 to 0.76 +/- 1.01 mm2/mm Hg x 10(-3), P < .05), but not in hypertensives (+0.41 +/- 1.26 to 0.36 +/- 1.31 mm2/mm Hg x 10(-3), not significant), and differed significantly between normotensive and hypertensive subjects (P < .05). Thus, pharmacologic stimulation disclosed a blunted response of endothelium-dependent action in the arterial compliance of the conduit arteries in hypertensive subjects. This suggests an impaired endothelial function reserve in persons with essential hypertension.

Acetylcholine↗
PubMed1997

Pharmacokinetics of imipenem-cilastatin in critically ill patients undergoing continuous venovenous hemofiltration.

The pharmacokinetics of imipenem-cilastatin were investigated in 12 critically ill patients with acute renal failure (ARF) managed by continuous veno-venous hemofiltration (CVVH) while receiving a fixed combination of 500 mg of imipenem-cilastatin intravenously three or four times daily. No adverse drug reactions were observed. Plasma and hemofiltrate samples were taken at specified times during one dosing interval, and the concentrations of imipenem and cilastatin were determined by high-performance liquid chromatography. Pharmacokinetic variables were calculated by a first-order, two-compartment pharmacokinetic model for both substances. Total clearances of imipenem and cilastatin (mean +/- standard deviations) were 122.2 +/- 28.6 and 29.2 +/- 13.7 ml/min, respectively, with hemofiltration clearances of 22.9 +/- 2.5 and 16.1 +/- 3.1 ml/min, respectively, and nonrenal, nonhemofiltration clearances of 90.8 +/- 26.3 and 13.2 +/- 13.9 ml/min, respectively. Mean imipenem dosage requirements were approximately 2,000 mg/24 h (2,111.8 +/- 493.4 mg/24 h). They were calculated in order to achieve an average steady-state concentration of 12 mg/liter to ensure that concentrations in plasma exceeded the MICs at which 90% of intermediately resistent bacteria are inhibited (8 mg/liter) during the majority of the dosing interval. By contrast, the recommended dosage for patients with end-stage renal failure (ESRF) and infections caused by intermediately resistant bacteria is 1,000 mg/24 h. This remarkable difference may be due (i) to differences in the nonrenal clearance of imipenem between patients with ARF and ESRF and (ii) to the additional clearance by the hemofilter. Since the total clearance of cilastatin was low, marked accumulation occurred, and this was particularly pronounced in patients with additional liver dysfunction. Thus, in patients with ARF managed by CVVH, rather high imipenem doses are required, and these inevitably result in a marked accumulation of cilastatin. The doses of imipenem recommended for patients with ESRF, however, will lead to underdosing and inadequate antibiotic therapy.

Acute Kidney Injury↗
PubMed1997

Glomerular hyperfiltration during sympathetic nervous system activation in early essential hypertension.

Glomerular hyperfiltration may be important for the development of essential hypertension. Both the renin-angiotensin system and the sympathetic nervous system influence renal hemodynamic regulation. To test the hypothesis that glomerular hyperfiltration can be unmasked by sympathetic nervous system activation, renal hemodynamics and humoral components of the renin-angiotensin system were examined at rest and during mental stress in 45 young normotensive healthy subjects and 37 young people with mild essential hypertension. GFR and renal plasma flow (RPF) were determined with inulin and para-aminohippuric acid clearance at rest and during stress. At rest, RPF, GFR, filtration fraction, plasma renin activity, angiotensin (Ang) II concentrations, and serum aldosterone values were similar in normotensive and hypertensive subjects. After stress, blood pressure increased (P < 0.01), but this was nearly identical in normotensive and hypertensive subjects (7.05 +/- 6.9 versus 7.03 +/- 4.6 mmHg, NS). The decrease in RPF (-27 +/- 54 versus -22 +/- 25 ml/min per 1.73 m2, NS) was also similar in the two groups. In contrast, the increase in GFR (+ 10.5 +/- 7.2 versus 6.08 +/- 5.7 ml/min per 1.73 m2, P < 0.001) and filtration fraction (+2.48 +/- 1.38 versus 1.82 +/- 1.49%, P < 0.05) was more marked in hypertensive than in normotensive subjects. The concomitant increase in Ang II concentrations was greater in hypertensive than in normotensive subjects (+4.6 +/- 1.0 versus -1.0 +/- 0.45 pg/ml, P < 0.001). The increase in GFR during mental stress was correlated with the increment in Ang II concentrations (r = 0.39, P < 0.001). Compared with the placebo control phase, blockade of the renin-angiotensin system with an angiotensin-converting enzyme inhibitor attenuated the increase in GFR during stress in hypertensive (8.04 +/- 5.01 versus 10.1 +/- 5.7 ml/min per 1.73 m2, P < 0.05), but not in normotensive, subjects. Even in early essential hypertension, glomerular hyperfiltration is evident during sympathetic nervous system activation, which is mediated by postglomerular vasoconstriction. This early stress-induced glomerular hyperfiltration may contribute to, or trigger, the development of essential hypertension.

Adult↗
PubMed1996

Specific immune tolerance during pregnancy after renal transplantation.

Pregnancy is associated with specific immunological tolerance to fetal antigens suggesting that immunoregulatory processes during pregnancy can induce specific immunological unresponsiveness. We report a case of a female renal transplant recipient who stopped immunosuppressive therapy during first pregnancy. Despite histologically proven acute renal allograft rejection during the early course of transplantation, no immunological response was observed for 9 years after withdrawal of immunosuppression. Two further pregnancies within that time period did not evoke any renal complications, but were complicated by premature rupture of the amnion and by the development of preeclampsia. To our knowledge, there are no reports of such a long-term specific unresponsiveness to a renal allograft without immunosuppressive therapy. Natural and active immunoregulatory mechanism can be related for the development of specific immune tolerance to renal allograft in this case.

Adult↗
PubMed1994

Renal hemodynamic response to stress is influenced by ACE-inhibitors.

Cardiovascular responses to new antihypertensive agents have been studied extensively under resting and stress conditions. However, the effects of antihypertensive agents on renal hemodynamics have only been investigated at rest. To test whether antihypertensive therapy leads to disparate renal hemodynamic effects during exposure to mental stress as opposed to resting conditions, we performed a double-blind, placebo-controlled crossover study. In 17 normotensive healthy men, glomerular filtration rate (GFR; inulin clearance) and renal plasma flow (RPF; para-aminohippuric acid clearance) were measured at rest and after a standardized mental stress test, with or without one week's treatment with a new, long-acting ACE-inhibitor cilazapril 2.5 mg/day. ACE-inhibition did not change resting blood pressure, RPF, GFR, or derived parameters, such as filtration fraction, renal vascular resistance and renal fraction of cardiac output. Mental stress caused an acute increase in GFR (p < 0.001) and filtration fraction with both treatments (0.001). However, the increase in GFR and filtration with mental stress was greater (p < 0.05) with cilazapril treatment than with placebo. Thus, renal hemodynamic responses to mental stress were influenced by ACE inhibitors. We conclude that the impact of antihypertensive agents on renal hemodynamics during stress cannot a priori be delineated from measurements at rest.

Adult↗
PubMed1993

Obesity as a determinant for response to antihypertensive treatment.

OBJECTIVE: To test the hypothesis that beta blockers lower blood pressure more effectively than calcium entry blockers in obese hypertensive patients and that calcium entry blockers are more effective in lean patients. DESIGN: Double blind, randomised controlled trial of treatment over six weeks. SETTING: Tertiary referral centre. SUBJECTS: 42 white men with uncomplicated mild to moderate essential hypertension (World Health Organisation stage I or II); 36 completed the study. INTERVENTION: Patients were randomised to metoprolol 50-100 mg twice daily or isradipine 2.5-5.0 mg twice daily for six weeks after a two week run in phase. MAIN OUTCOME MEASURE: Blood pressure after six weeks of treatment. RESULTS: When stratified according to treatment and presence of obesity (body mass index < or = 27 kg/m2), the mean (SD) fall in blood pressure in the beta blocker group was 24 (13)/18 (10) mm Hg in obese patients and 18 (19)/12 (13) mm Hg in lean patients. In the calcium entry blocker group, the fall in blood pressure was 21 (15)/17 (6) mm Hg in lean patients and 18 (11)/8 (10) mm Hg in obese patients. After taking age and blood pressure before treatment into account there was a significant interaction between obesity and drug therapy (p = 0.019) with a better diastolic blood pressure response to calcium entry blockers in lean patients and to beta blockers in obese hypertensive patients. CONCLUSION: Obesity affects the efficacy of metoprolol and isradipine in reducing blood pressure.

Blood Pressure↗
PubMed1991

Stapedectomy modified by the application of fibrin tissue adhesive.

Certain failures of the stapes operation are caused by loosening of the crimped metal loop on the long process of the incus, atrophy or necrosis of the lenticular process, erosion of the long process with the prosthesis causing injury to the labyrinth, erosion of the incudostapedial joint with upward rotation of the long process, and dislocation of the prosthesis. To reduce the occurrences of these failures following stapes removal, we close the oval window by gluing a fascia graft into place with fibrin tissue adhesive. A ceramic strut with a cup on its upper end that fits the lenticular process is glued between the fascia graft and the lenticular process. This method does not cause bone necrosis or blood circulation disturbances. The hearing results are the same or better than those reported for other stapes procedures.

Animals↗
PubMed1986

[Dilatation of the glottis in bilateral vocal cord paralysis. Review of various surgical procedures and a report of personal experience using a functional lateral fixation surgical technic].

For the treatment of bilateral vocal cord paralysis, the author's technique consists of preservation of the posterior crico-arytenoid ligament as a hinge as well as turning and tilting of the arytenoid cartilage laterally. It is held in this position with three permanent retention sutures, two of them armed with heavy knots. These knots will reinforce the lateral rotation of the arytenoid cartilage. These sutures run in the submucosa horizontally along the anterior surface of the arytenoid cartilage and are fixed through burr holes on the posterior margin of the thyroid cartilage. This method developed from the original "King Procedure" leaves the laryngeal mucosa maximally undisturbed so that in 80% of the cases preliminary tracheotomy became unnecessary. During a period of 27 years, 110 patients were operated; 27 of them had a previously created tracheostoma. Out of the remaining 83, 16 had tracheotomy directly before surgery. Of the remaining 67 patients, four required postoperative tracheotomy for a few days only, while 63 did not require this additional treatment. The average hospital stay was 11 days. In the majority of cases the operation could be performed under local anaesthesia which helped to establish proper voice function.

Adolescent↗
PubMed1979

[Some reasons for failure in tympanoplasty (author's transl)].

The reasons for failures in tympanoplasty are classified and discussed as anatomical or pathological ones and those, that rise from method and technique. A main cause insists in the pathopolymorphism of the chronic purulent otitis media and the discrepancy of clinical impression and pathological reality. The author wishes to encourage the surgeons to a more radical technique by these examples and to the use of new methods in the field of reconstructive surgery of the middle ear.

Humans↗