Revisiting autonomic dysfunction in end-stage renal disease patients.
BACKGROUND
Autonomic dysfunction is frequent in end-stage renal disease (ESRD) patients, but both the relative involvement of the parasympathetic and sympathetic branches and the role of antihypertensive drugs in this setting are still controversial. The present study addressed these issues employing a battery of standard noninvasive cardiovascular autonomic tests.


METHODS
Sympathetic (S) function was evaluated by responses of both systolic blood pressure (BP) to passive tilting and diastolic BP to handgrip; parasympathetic (P) function, through the respiratory sinus arrhythmia test and the heart rate response to the 4-s unloaded exercise test. Additional tests influenced by both branches of the autonomic system (P + S) were accomplished by the assessment of heart rate response to the Valsalva maneuver, handgrip, and tilting.


RESULTS
Studied subjects belonged to one of the three groups: ESRD patients not requiring BP medications (n = 11; 8 men, 3 women); ESRD patients receiving antihypertensive therapy (n = 36; 21 men, 15 women); and apparently healthy controls (n = 15; 10 men, 5 women). When the variables grouped according to the branch of the autonomic nervous system predominantly probed were analyzed, only the frequency of impaired sympathetic autonomic responses was higher in ESRD patients not receiving BP drugs compared to controls (55 vs. 23%, P = 0.040). In contrast, when ESRD patients receiving BP drugs were compared to controls, the differences became significant in S, P, and P + S tests (46 vs. 23%, P = 0.045; 22 vs. 3%, P = 0.020; and 34 vs. 13%, P = 0.010, respectively). With the criterion of more than one positive finding in any of the variables examined for diagnosing autonomic dysfunction, the prevalence of autonomic dysfunction was 20% in controls, 64% in ESRD patients not receiving BP drugs (P = 0.005 vs. controls), and 67% in ESRD patients receiving BP drugs (P = 0.043 vs. controls).


CONCLUSIONS
ESRD continues to be associated with a high prevalence of autonomic dysfunction. ESRD patients receiving BP drugs were found to have detectable impairment in the entire autonomic system in contrast to those not receiving BP drugs in whom inadequate responses were restricted to the sympathetic branch.
Lugon
Jocemir R
JR
Department of Clinical Medicine, Universidade Federal Fluminense, Niteroi-RJ, Brazil. jocerl@hospital.huap.uff.br
Warrak
Elias A
EA
Lugon
Adriano S
AS
Salvador
Bruno A
BA
Nobrega
Antonio C L
AC