Biomedical subjects

T L Opfer-Gehrking

Publications and source records attributed to T L Opfer-Gehrking.

30 records · Page 2Linked to original sources

PubMed1996

Role of physical countermaneuvers in the management of orthostatic hypotension: efficacy and biofeedback augmentation.

OBJECTIVE: To evaluate the efficacy of various physical countermaneuvers in reducing orthostatic hypotension and its associated symptoms and to assess the efficacy of biofeedback training in enhancing the effectiveness of physical countermaneuvers. MATERIAL AND METHODS: In nine study subjects with neurogenic orthostatic hypotension, four training sessions on physical countermaneuvers were performed after tilt-up, three with visual feedback on the effect of physical countermaneuvers on blood pressure and other cardiovascular variables. Blood pressure change and orthostatic symptoms during tilt-up were determined, as were the changes in total peripheral resistance, stroke index, and heart rate. RESULTS: The five female and four male patients had a mean age of 53 years and a mean duration of symptoms of 4.2 years. On an orthostatic symptom scale of 0 to 10, these patients had a mean symptom score of 7.3. The increment in systolic blood pressure was better for some maneuvers (such as leg crossing and a combination) than others (such as neck flexion and abdominal contraction). Three patterns of responses to biofeedback were found. Simple maneuvers such as squatting did not improve with training; visual feedback was needed for maneuvers such as thigh contraction, and performance declined without biofeedback; the third pattern, seen in maneuvers such as leg crossing, showed continued improvement with training, even without biofeedback. A survey at 3 to 4 months after training revealed continued use of physical maneuvers (3.8 +/- 3.1 per day), increased standing time with each episode of presyncopal symptoms (8.3 +/- 5.8 minutes), and continued global symptomatic improvement. Total peripheral resistance, but not heart rate or stroke index, showed significant regression with blood pressure improvement. CONCLUSION: Physical countermaneuvers are efficacious in reducing orthostatic hypotension, can be augmented by use of biofeedback, and may significantly improve the functional outcome. The major mechanism of improvement is an increase in total peripheral resistance, presumably by reducing the vascular capacitance.

Adult↗

PubMed1995

Prospective evaluation of clinical characteristics of orthostatic hypotension.

OBJECTIVE: To undertake a prospective study of the clinical characteristics of orthostatic intolerant patients referred to the Mayo Autonomic Reflex Laboratory with suspected orthostatic hypotension (OH). DESIGN: Autonomic function tests were performed to quantify the severity of sudomotor, adrenergic, and cardiovagal failure and generate a composite autonomic symptom score (CASS). CASS was related to a symptom score, which was derived from the frequency of orthostatic intolerance and syncope and the standing time until occurrence of symptoms. RESULTS: Three groups were defined by their response to a tilt study: group I, 90 patients with symptomatic OH, mean age, 63.6 years; group II, 60 patients who had symptoms without OH, mean age, 48.9 years; and group III, 5 patients with asymptomatic OH, mean age, 68.0 years. Group I had a significantly higher CASS (P < 0.001) than did those without OH. Further analysis was done on the 90 patients in group I. The most common symptoms were lightheadedness, weakness, impaired cognition, visual blurring, tremulousness, and vertigo. The most common aggravating factors were prolonged standing, exercise, warming, and eating. Most patients (75%) could stand for less than 5 minutes before symptoms occurred. Symptoms regressed significantly with CASS but not with the tilt grade. CONCLUSION: Patients with generalized autonomic failure have a recognizable pattern of symptoms and aggravating factors that relate, albeit imperfectly, to the severity of autonomic failure.

Autonomic Nervous System↗

PubMed1995

Postural tachycardia syndrome (POTS).

In orthostatic intolerance, the patient develops symptoms while standing that are relieved when the patient assumes a supine position. Different degrees of orthostatic intolerance exist, but not a system of grading severity. We have developed a system that grades the severity of orthostatic intolerance by the three-pronged criteria of the rapidity of development and the severity of orthostatic symptoms, the ability of the subject to withstand orthostatic stresses, and the degree of interference with daily living. In this article, this system is presented, and one disorder, postural tachycardia syndrome (POTS), is examined in some detail.

Humans↗

PubMed1994

Comparison of the postural tachycardia syndrome (POTS) with orthostatic hypotension due to autonomic failure.

Postural tachycardia syndrome (POTS) is characterized by orthostatic dizziness, tremulousness, tachycardia and variable blood pressure changes. Since some POTS patients have a marked reduction in pulse pressure on standing, a major mechanism of their symptoms might be venous pooling. We therefore studied the cardiovascular response to head-up tilt, Valsalva maneuver and deep breathing in: control subjects (n = 11; F = 8; M = 3; 39.2 +/- 14.4 years); patients with orthostatic hypotension secondary to autonomic failure (n = 11; F = 9; M = 2; 61.7 +/- 13.0 years), and patients with POTS (n = 15); F = 13; M = 2; 32.3 +/- 10.6 years). Blood pressure was measured with a Finapres, and cardiac output, stroke volume, end-diastolic volume and thoracic impedance (TFI) were measured by thoracic electrical bioimpedance. During tilt (in contrast to patients with orthostatic hypotensiom), patients with POTS had excessive tachycardia (P < 0.001), a normal to excessive total peripheral resistance increase, and an exaggerated decrease in stroke volume (P < 0.001) and end-diastolic volume (P < 0.001). These findings suggest that sympathetic arteriolar function remains relatively intact but that sympathetic venomotor function is selectively impaired. These findings may have significant implications for the treatment of patients with POTS.

Adult↗

PubMed1993

Comparison of directly stimulated with axon-reflex-mediated sudomotor responses in human subjects and in patients with diabetes.

The muscarinic receptors of human eccrine sweat gland may be directly stimulated by iontophoresis of acetylcholine (direct response; DIR) and indirectly via nicotinic receptors and an axon "reflex" (AXR). Using a specially designed multicompartmental sweat cell and dual sudorometers, we were able to simultaneously record the evoked DIR and AXR responses. On a second day, we repeated the experiment under identical ambient and stimulus conditions but instead obtained silastic imprints of DIR and AXR for morphometry. Studies were done on 24 controls (mean +/- SD = 47.6 +/- 15.1 years) and 23 diabetic subjects (mean +/- SD = 49.6 +/- 16.3 years). In control subjects, sudorometric DIR recordings were consistently larger than AXR. There was no difference in sweat droplet density by sex, but the size of droplets was larger in males. In diabetic patients 3 of 23 had absent AXR but preserved DIR, suggesting that failure of AXR preceded DIR in patients with neuropathy. Patients with mild neuropathy had an overrepresentation of large diameter droplets in the silastic imprints of both DIR and AXR, while patients with severe neuropathy had a markedly reduced density and small diameter droplets.

Acetylcholine↗

PubMed1993

Impaired respiratory sinus arrhythmia with paradoxically normal Valsalva ratio indicates combined cardiovagal and peripheral adrenergic failure.

Combined reductions of the heart rate responses to deep breathing (HRDB) and the Valsalva ratio (VR) are used as a standard test of cardiovagal function. We observed that some patients had marked reduction of HRDB with a paradoxically normal VR. The mechanism of this paradox was evaluated. We found that these patients had evidence of peripheral adrenergic and postganglionic sudomotor impairment, including an excessive fall in blood pressure on upright tilt. Since VR depends on heart rate responses to blood pressure excursions, we evaluated the phases of the Valsalva manoeuvre and the ensuing heart rate responses in these patients and compared the responses to patients with generalized autonomic failure (Group II) and controls (Group III). Group I patients when compared with controls, had a larger phase II fall in blood pressure and normal phase IV resulting in a significantly enhanced baroreflex stimulus. These patients had a normal heart rate increment but 75% failed to develop reflex bradycardia. We conclude that the paradoxical VR is due to the exaggerated blood pressure swing due in turn to adrenergic failure. When both HRDB and VR are reduced as in Group II, there may be the additional impairment of cardiac adrenergic failure.

Adult↗

PubMed1992

Differential effects of amitriptyline on sudomotor, cardiovagal, and adrenergic function in human subjects.

Tricyclic antidepressants, especially amitriptyline (AMI), are widely used by patients who require tests of autonomic function. AMI effects autonomic function, but its quantitative and differential effects are not known. We prospectively evaluated the effect of AMI on sudomotor (M3 receptor), cardiovagal (M2) and adrenergic functions in 6 subjects, aged 20-40 years before, during, and 48 hours after AMI 75 mg/d. M3 receptor function was evaluated using QSART (quantitative sudomotor axon reflex test) recordings from four sites, M2 receptor function from cardiovagal studies [HR response to deep breathing (HRDB) and the Valsalva ratio (VR)], and adrenergic function from an analysis of beat-to-beat BP responses to tilt and the Valsalva maneuver. Plasma AMI was determined from blood samples obtained within 2 hours of autonomic testing. QSART volume was reduced by 47% by AMI (P = 0.01), and recovered to 81% of baseline following a 48-hour washout. HRDB was unaffected by AMI (P > 0.05). VR was increased by 10% (NS) with AMI and by 14% (P < 0.05) with washout. The percent change in hemodynamic parameters by AMI were: orthostatic reduction in SBP, 62% (NS); orthostatic HR increment, 66%, (P = 0.03); and phase IIe SBP decrement, 665%, (P = 0.02). We conclude that AMI in the moderate doses used, resulted in greater inhibition of M3 than M2 receptors. The BP, HR, and beat-to-beat BP alterations likely reflect adrenergic inhibition resulting in a reduction in effective plasma volume. A washout of 48 hours is adequate for muscarinic but not adrenoreceptors.

Adult↗

PubMed1992

In vivo studies on receptor pharmacology of the human eccrine sweat gland.

The receptor pharmacology of the human sweat gland was studied in vivo. The axon-reflex response was mediated by nicotinic receptors which were activated by nicotine and acetylcholine, but not pilocarpine, and inhibited by hexamethonium. The direct response was mainly muscarinic, responding to pilocarpine and acetylcholine. A component of the direct response was nicotinic, since it was activated by nicotine and blocked by hexamethonium in a dose-dependent manner. The axon-reflex response to nicotine and acetylcholine was partially blocked by pilocarpine, especially when application of pilocarpine preceded the procedure. The inhibition of the nicotinic response may be secondary to M1 antagonism since pilocarpine is an M2 agonist and M1 antagonist and pirenzepine, a specific M1 antagonist, caused similar effects as pilocarpine.

Acetylcholine↗

PubMed1991

Use of the photoplethysmographic technique to analyze the Valsalva maneuver in normal man.

We analyzed the Valsalva maneuver (VM) using a photoplethysmographic technique in 24 normal subjects. We studied the effects of test duration (range 5 to 20 seconds) and magnitude of expiratory pressure (EP, range 20 to 50 mmHg) on maximal (% delta) and time integrated (int) changes in heart rate (HR), and mean (MAP) and pulse (PP) pressures during phases II and IV. At all EPs, there was correlation (P less than 0.01) between % delta MAP in both late phase II and phase IV and duration of the VM. The Valsalva ratio (VR) correlated with test duration only at high EPs. All responses, except the fall in MAP in early phase II and bradycardia in phase IV, correlated with EPs. The VR correlate not only with HR responses in phases II and IV but also with MAP and PP overshoot in phase IV. Correlations between maximal AP and HR changes in either phase II and IV were poor. Our study indicates that the photoplethysmographic technique allows a more rational interpretation of the VM in the clinical setting. The VR cannot be adequately interpreted without comcomitant monitoring of arterial pressure during the VM.

Adult↗

PubMed1990

The effect of aging on cardiac autonomic and postganglionic sudomotor function.

Little quantitative information is available on the effects of age on peripheral autonomic function. We studied the effect of age on the heart rate (HR) responses to deep breathing and the Valsalva maneuver in 122 and 155 subjects, respectively, aged 10 to 83 years. The quantitative sudomotor axon reflex test (QSART) was determined in 114 subjects in the same age group. The HR responses were not different between the sexes, but a consistently significant regression with age was demonstrated in response to deep breathing and the Valsalva ratio. The QSART responses were significantly larger in male subjects and were generally lower in older subjects of both sexes but a significant negative regression with age was found only in female subjects. Cardiac vagal function is impaired with age, but postganglionic sympathetic function is little affected by age, suggesting selectivity of effects of aging on autonomic function.

Adolescent↗

PubMed1989

Sweating patterns in atopic dermatitis patients.

Postganglionic sweat output in ten patients with atopic dermatitis was determined by a quantitative sudomotor axon reflex test in which the output results from axon reflex stimulation by acetylcholine iontophoresis. All measurements were obtained from normal skin on the volar aspect of the left wrist and dorsal aspect of the left foot of the atopic patients. Latency, sweat volume, and dynamic sweat pattern were variables included in the study. An abnormal value or configuration was found in nine of the ten patients studied. Seven of the ten patients had abnormal sweat output values. Atopic patients have abnormal sweating patterns, which may be inherently responsible for or related to their disorder.

Acetylcholine↗

PubMed1989

The venoarteriolar reflex in diabetic and other neuropathies.

Limb dependency activates the venoarteriolar reflex (VAR), resulting in reflex vasoconstriction (RV). Since others have reported the VAR to fail in diabetic neuropathy, we examined the reliability of this test in detecting sympathetic failure in diabetic and other neuropathies. We studied 40 controls, 49 diabetic subjects, and 29 patients with other neuropathies. The mean RV was greater in controls than in diabetics or other neuropathies, but there were marked overlaps among groups. We conclude that the VAR, while impaired in the neuropathies, is of little value as a clinical test and is a poorer test of autonomic function than the quantitative sudomotor axon reflex test or heart rate responses to deep breathing or the Valsalva maneuver.

Adult↗