Clinical autonomic research : official journal of the Clinical Autonomic Research Society
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Treatment with head-up tilt sleeping and low-dose fludrocortisone effectively minimizes orthostatic symptoms and increases orthostatic blood pressure in patients with neurogenic orthostatic hypotension. The aim of the present study was to examine whether the improvement in orthostatic blood pressure during combined treatment with low-dose fludrocortisone and nocturnal head-up tilt in patients with neurogenic orthostatic hypotension can be attributed to expansion of plasma volume or to increased total peripheral resistance. The effects of a 3-week treatment with fludrocortisone and nocturnal head-up tilting on the postural changes in arterial pressure, heart rate, and cardiac output (pulse contour) were evaluated in eight consecutive patients with orthostatic hypotension. ⋯ The responses of plasma renin activity and aldosterone to orthostatic stress prior to treatment were subnormal and became even lower after treatment. The improvement in upright blood pressure in orthostatic hypotension during treatment with fludrocortisone and nocturnal head-up sleeping is the result of a reduction in the orthostatic decrease in cardiac output. Preliminary data suggest that the expanded body fluid volume is allocated to the perivascular space rather than to the intravascular space.
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Recent investigations suggest a role for neurally mediated hypotension (NMH) in the symptomatology of chronic fatigue syndrome (CFS) in adults. Our previous observations in children with NMH and syncope (S) unrelated to CFS indicate that the modulation of sympathetic and parasympathetic tone measured by indices of heart rate variability (HRV) is abnormal in children who faint during head-up tilt (HUT). In order to determine the effects of autonomic tone on HUT in children with CFS we performed measurements of HRV during HUT in 16 patients aged 11-19 with CFS. ⋯ All indices of HRV are markedly depressed in CFS patients, even when compared with already low HRV in S+ or Control+ patients. Sympathovagal balance does not shift toward enhanced sympathetic modulation of heart rate with HUT and there is blunting in the overall HRV response with syncope during HUT. Taken together these data may indicate autonomic impairment in patients with CFS.
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Randomized Controlled Trial Clinical Trial
Heart rate variability effects of an agonist or antagonists of the beta-adrenoceptor assessed with scatterplot and sequence analysis.
There is evidence that the processes regulating heart rate variations reflect non-linear complexity and show 'chaotic' determinism. Data analyses using non-linear methods may therefore reveal patterns not apparent with conventional statistical approaches. We have consequently investigated two non-linear methods, the Poincaré plot (scatterplot) and cardiac sequence (quadrant) analysis, and compared these with standard time-domain summary statistics, during a normal volunteer investigation of an agonist and antagonists of the cardiac beta-adrenoceptor. ⋯ The duration of beat-to-beat difference shortened after celiprolol; this contrasted with increased duration of beat-to-beat difference after propranolol and atenolol. These results demonstrated a shift towards sympathetic dominance after the beta-adrenoceptor partial agonist celiprolol contrasting in parasympathetic dominance after the beta-adrenoceptor antagonists propranolol and atenolol. These non-linear methods appear to be valuable tools to investigate HRV in health and in cardiovascular disease and to study the implications of alterations in autonomic control during therapeutic intervention.
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Venoms and poisons of jellyfish and other marine animals can induce damage to the human nervous and circulatory systems. Clues to the pathogenesis and clinical manifestations of these lesions can be obtained from data of human envenomations and animal experimentation. Because many investigators are unaware that marine animal venoms have autonomic actions, this paper aims to elucidate the broad antagonistic or toxic effects these compounds have on the autonomic nervous system. ⋯ Actions on nerves, as well as skeletal, smooth or cardiac muscle occur. Recent studies indicate that the hepatic P-450 enzyme family may be injured by these compounds. The multiplicity of these venom activities means that a thorough understanding of the sting pathogenesis will be essential in devising effective therapies.
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The objective of the present investigation was to describe and localize autonomic dysfunction in acute and chronic stages of complex regional pain syndrome (CRPS). Patients were investigated twice: the first investigation was performed as soon as diagnosis was established during the acute stage of CRPS and the second investigation was performed about 2 years later. Twenty-one patients completed the follow-up investigation. ⋯ In conclusion, the present investigation proved that vasomotor and sudomotor control are substantially altered in CRPS. In the acute stage vasomotor control is decreased in the affected limb whereas sudomotor function is enhanced. This may be the result of disturbances of thermoregulation, but different secondary peripheral mechanisms, concerning vasomotor and sudomotor function, contribute to clinical presentation of CRPS and affect autonomic function at all stages of CRPS.