Sympathetic skin response in hemodialysis patients: Correlation with nerveconduction studies and adequacy of dialysis

A sympathetic skin response (SSR) test was performed in diabetic and nondia betic patients undergoing regular hemodialysis and the results correlated w ith nerve conduction studies (NCS): sensory conduction velocity (SCV) and m otor conduction velocity (MCV). Comparisons were made between diabetic and nondiabetic patients and between cuprophane and polyacrylonitrile membrane dialyzed patients. Six nondiabetic uremic patients (30%) and all diabetic p atients had no SSR. Eight nondiabetic uremic patients (40%) had a mildly im paired response. Nondiabetic patients with a normal response were younger ( 31.1 +/- 16.4 years) than the patients with abnormal SSR, whether mildly im paired response (58.3 +/- 20.3 years; p < 0.05, Anova) or absent response ( 65.3 +/- 13.8 years; p < 0.01, Anova). SCV, MCV, and SSR values were reduce d (p < 0.01) in uremic patients with respect to normal subjects. Severity a nd frequencies of sensory NCS abnormalities in nondiabetic patients were: n ormal 20%, mildly impaired 75%, and severely impaired 5%. Severity and freq uencies of motor conduction abnormalities were: normal 80%, mildly impaired 20%, severely impaired 0%. The SSR abnormality incidence in patients with a normal NCS was similar to that in patients with either mildly or severely impaired NCS (chi-square test). There was a positive linear correlation be tween the SSR amplitude and SCV (r = 0.52, p < 0.01) and MCV (r = 0.49, p < 0.01). The SSR latency was also significantly related to SCV (r = 0.66, p < 0.01) and MCV (r = 0.61, p < 0.01). A significant negative correlation wa s found between age and SSR parameters, amplitude (r = -0.56, p < 0.01) and latency (r = -0.66, p < 0.01). No correlation was found between duration o f hemodialysis or Kt/V and SSR. No differences were found in SSR, NCS, or K t/V values between cuprophane membrane and polyacrylonitrile membrane dialy zed patients (Student's t test). The relationship between NCS and SSR in ur emic patients was confirmed. Old age and diabetes mellitus, but not the dia lysisis membrane used, were confirmed as synergistic factors of neuropathic impairment. It appeared that SSR is more sensitive than NCS in detecting p olyneuropathy in uremic patients on hemodialysis.