Initial circulatory response to active standing in Parkinson's disease without typical orthostatic hypotension

While the circulatory response to orthostatic stress has been already evaluated in Parkinson's disease patients without typical orthostatic hypotension (PD-TOH), there is an initial response to the upright position which is uniquely associated with active standing (AS). We sought to assess this response and to compare it to that seen in young healthy controls (YHC). Method In 10 PD-TOH patients (8 males, 60±7 years, Hoehn and Yahr ≤3) the changes in systolic blood pressure (SBP) and heart rate that occur in the first 30 seconds (sec) of standing were examined. Both parameters were non-invasively and continuously monitored using the volume-clamp method by Peñáz and the Physiocal criteria by Wesseling. The choice of sample points was prompted by the results of previous studies. These sample points were compared to those of 10 YHC (8 males, 32±8 years). Results The main finding of the present investigation was an increased time between the AS onset and SBP overshoot in PD-TOH group (24±4 vs. 19±3 sec; p<0.05). Conclusion This delay might reflect a prolonged latency in the baroreflex-mediated vascular resistance response, but more studies are needed to confirm this preliminary hypothesis.