Arterial Baroreflex Function in Patients with Parkinson’s Disease: a Pharmacological Approach

Abstract

Parkinson’s disease (PD) is a neurodegenerative disorder that is known for its motor dysfunction. Moreover, PD also causes non‐motor impairments, and approximately 40% of the patients experience coexistent abnormalities, like orthostatic hypotension (OH). The OH induces incapacitating symptoms that can contribute to an increased risk of falls, which have a great impact on patients’ quality of life. The arterial baroreflex system plays a pivotal role in counteracting transient falls in blood pressure during the execution of activities of daily living. Although a plethora of studies have indicated that an impaired baroreflex function is a clinical feature in patients with PD, none of the human studies have used the modified oxford method, which is considered the gold standard approach for assessing arterial baroreflex sensitivity (BRS). Additionally, since the OH and arterial BRS have an age‐dependent effect, studies with younger patients with PD is lacking. In this sense, the aim of the present study was to test the arterial baroreflex function in patients with PD with and without OH and aged‐matched control during rapid changes in blood pressure induced by sequential boluses of vasoactive drugs (Modified‐Oxford Technique). Beat‐to‐beat HR (electrocardiography) and BP (finger photoplethysmography) were obtained during 10‐min of supine rest preceding a modified‐Oxford [bolus injection of 65–100μg sodium nitroprusside (NTP) followed by 65–100μg phenylephrine hydrochloride (PHE) 1 min afterwards] in five patients with PD (50±6yr; Hohen and Yhar: <3a.u.; diagnose time: 8.8±3.7yr) and seven age‐matched controls (48±7yr). Arterial BRS was analyzed using the slopes of the linear portions of the R‐R interval‐systolic BP relationship. Patients with PD had lower BP at rest compared to controls (82±7 vs. 94±5mmHg, P=0.01) and a trend for higher HR (72±13 vs. 59±8bpm, P=0.06). The average of falling (ΔSBP: −37±0.65 vs. −31±0.43, P=0.26) and rising systolic BP (ΔSBP: −27±0.76 vs. −20±0.58, P=0.38) was similar between patients with PD and controls. Our preliminary results showed that arterial BRS was lower in patients with PD compared to controls for falling pressure (NTP trial: 4.52±0.34 vs. 9.81±0.23ms/mmHg, P=0.01) and for rising pressure (PHE trial: 5.08±0.27 vs. 13.60±0.55ms/mmHg, P=0.03). Of note, only one of the patients presented OH, and the baroreflex function was characterized by a marked blunted arterial BRS for failing pressure (NTP trial: 1.83ms/mmHg) and an averaged BRS for rising in pressure. Our preliminary results indicated that the ups and downs of baroreflex function are impaired in patients with PD, and the downs appear to be further impaired in patients with OH. These findings provide a better understanding of the neural control of blood pressure in patients with PD, and future studies should focus on OH.Support or Funding InformationCNPq, FAPDF and CAPES.