Adrianus A. J. Smit

Pathophysiological basis of orthostatic hypotension in autonomic failure

In patients with autonomic failure orthostatic hypotension results from an impaired capacity to increase vascular resistance during standing. This fundamental defect leads to increased downward pooling of venous blood and a consequent reduction in stroke volume and cardiac output that exaggerates the orthostatic fall in blood pressure. The location of excessive venous blood pooling has not been established so far, but present data suggest that the abdominal compartment and perhaps leg skin vasculature are the most likely candidates. To improve the orthostatic tolerance in patients with autonomic failure, protective measures that reduce excessive orthostatic blood pooling have been developed and evaluated. These measures include physical counter‐manoeuvres and abdominal compression.

Use of lower abdominal compression to combat orthostatic hypotension in patients with autonomic dysfunction.

Abstract.The aim of this study was to investigate in patients with neurogenic orthostatic hypotension the mechanism and usefulness of abdominal compression to increase standing blood pressure. In three protocols, 23 patients underwent abdominal compression. Protocol 1 evaluated in a 40–60° head-up-tilt position, the effect of abdominal compression on caval vein and femoral diameter, arterial blood pressure and hemodynamics. Protocol 2 documented the relationship between the level of compression and the arterial pressure response. Protocol 3 investigated the ability to maintain standing blood pressure by an elastic binder. During head-up-tilt, compression (40 mm Hg) resulted in a reduction in diameter of the caval vein (mean –2.6mm, range –1.4 to 0.6), without a change in femoral vein diameter. Stroke volume increased by 14 % (range –1 to 23) and blood pressure (systolic/diastolic) by 30/14 mmHg (range 7/2 to 69/36), both p < 0.05; 40 mmHg compression was associated with a higher pressure response than 20 mmHg (mean 18/8 mmHg, range 6/2 to 43/20 vs. mean 9/4 mmHg, range –1/0 to 18/8, p < 0.05). Elastic abdominal binding increased standing blood pressure with 15/6mmHg (range –3/3 to 36/14, p < 0.05). We conclude that in patients with neurogenic orthostatic hypotension, abdominal compression increases standing blood pressure to a varying degree by increasing stroke volume.

Unusual Recovery From Acute Panautonomic Neuropathy After Immunoglobulin Therapy

A 33-year-old woman with acute idiopathic postganglionic panautonomic neuropathy experienced prompt recovery of all dysautonomic symptoms after receiving high-dose intravenous immunoglobulin therapy. Her recovery was complete within 6 months after onset of disease. This unusually rapid and complete recovery in comparison with that of historical control subjects suggests that patients with acute, severe, and widespread autonomic failure might benefit from intravenous immunoglobulin therapy.

Pathophysiological Mechanisms Underlying Vasovagal Syncope in Young Subjects

The occurrence of vasovagal fainting is common in young subjects, but the origin of the precipitating hemodynamic mechanisms involved remain a subject of considerable speculation. Vasovagal fainting is not a sudden onset phenomenon, early failure of vascular resistance responses occurs in faint‐prone young subjects. The variability of hemodynamic responses during the actual faint is large, but the main mechanism operative during, is withdrawal of sympathetic outflow to blood vessels in skeletal muscle with impairment of ability to maintain vasomotor tone.

Twenty four hour continuous non-invasive finger blood pressure monitoring: a novel approach to the evaluation of treatment in patients with autonomic failure.

Occasional sphygmomanometric readings are not an effective way of evaluating the effect of treatment in patients with hypoadrenergic orthostatic hypotension. A novel non-invasive portable device (Portapres) was used to monitor 24 hour continuous finger blood pressure before and during chronic volume expansion in a 66 year old woman with severe orthostatic hypotension. In both conditions pressures while she was standing were lowest in the morning. Her tolerance to standing and walking increased during the day and, as a consequence of a higher upright mean blood pressure, was improved after treatment. Mean blood pressure during sleep was increased after treatment. Continuous 24 hour non-invasive finger blood pressure monitoring is a promising technique for the evaluation of the effect of treatment in patients with autonomic failure. It provides information about situations in daily life that cannot be obtained by laboratory tests or conventional sphygmomanometric measurements.

Orthostatic Hypotension Due to Suppression of Vasomotor Outflow After Amphetamine Intoxication

Ten hours after ingestion of amphetamines, a previously healthy 17-year-old female adolescent experienced dizziness on standing. Examination revealed pronounced drowsiness and severe orthostatic hypotension. Assessment of arterial baroreflex function suggested that suppressed sympathetic vasomotor drive was the cause of the orthostatic hypotension. Within 3 days, the baroreflex failure resolved spontaneously. To our knowledge, suppressed vasomotor outflow after ingestion of amphetamines has been previously observed only in animal studies.

Patients' choice of portable folding chairs to reduce symptoms of orthostatic hypotension.

Patients with neurogenic orthostatic hypotension may use portable folding chairs to prevent or reduce symptoms of low blood pressure. However, a concomitant movement disorder may limit the use of these chairs in daily living. In this prospective study, 13 patients with orthostatic hypotension, balance disturbance associated with motor disability, or both examined three commercially available portable folding chairs. A questionnaire was used to document the characteristics in chair design that were relevant for satisfactory use to these patients. Armrests, seat width, and an adjustable sitting height were found to be important features of a portable folding chair. One chair was selected by 11 of 13 patients to fit most needs.

Diabetic autonomic neuropathy: Conventional cardiovascular laboratory testing and new developments

Cardiovascular reflex tests remain the investigational cornerstone for the assessment of patients in the clinical autonomic laboratory. Three cardiovagal tests have been found suitable for testing: the instantaneous heart rate responses induced by deep breathing, Valsalvas manoeuvre and standing up. Suitable laboratory indices of adrenergic function include continuous monitoring of blood pressure responses induced by Valsalvas manoeuvre and standing up, which is now possible through tracking of beat-to-beat blood pressure changes at the finger. Spectral analysis of heart rate and blood pressure and pulse wave analysis for stroke volume changes are promising approaches to evaluate abnormalities in arterial baroreflex regulatory mechanisms in diabetic patients