Sympathetic skin response in hemodialysis patients: correlation with nerve conduction studies and adequacy of dialysis.

A sympathetic skin response (SSR) test was performed in diabetic and nondiabetic patients undergoing regular hemodialysis and the results correlated with nerve conduction studies (NCS): sensory conduction velocity (SCV) and motor 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 patients had no SSR. Eight nondiabetic uremic patients (40%) had a mildly impaired response. Nondiabetic patients with a normal response were younger (31.1+/-16.4 years) than the patients with abnormal SSR, whether mildly impaired 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 reduced (p<0.01) in uremic patients with respect to normal subjects. Severity and frequencies of sensory NCS abnormalities in nondiabetic patients were: normal 20%, mildly impaired 75%, and severely impaired 5%. Severity and frequencies 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 between 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 was 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 of hemodialysis or Kt/V and SSR. No differences were found in SSR, NCS, or Kt/V values between cuprophane membrane and polyacrylonitrile membrane dialyzed patients (Student's t test). The relationship between NCS and SSR in uremic patients was confirmed. Old age and diabetes mellitus, but not the dialysis membrane used, were confirmed as synergistic factors of neuropathic impairment. It appeared that SSR is more sensitive than NCS in detecting polyneuropathy in uremic patients on hemodialysis.