Comparison of autonomic function using Valsalva ratio and 30:15 postural ratio prior to and after haemodialysis treatment

In published studies of chronic haemodialysis patients, the frequency of autonomic dysfunction varies widely. One reason for the variation may be the time of testing with respect to time of dialysis. The current study tests the hypothesis that autonomic function — as measured by heart rate responses to the Valsalva manoeuvre (Valsalva ratio) and 30:15 electrocardiogram (ECG) R—R interval to upright posture (postural ratio) — is different when patients are above dry weight (predialysis) than when they are at or below dry weight (postdialysis). The study also reviews available literature to analyze other factors that may affect the results of autonomic testing in this population. A total of 25 chronic haemodialysis patients underwent standard Valsalva and 30:15 R—R interval postural autonomic testing prior to and after haemodialysis. In addition, pre- and postdialysis orthostatic responses were measured and compared with a control population. The 30:15 ratio increased after dialysis (p = 0.001). The Valsalva ratio did not change with dialysis. Out of 25 subjects, seven had an abnormal 30:15 ratio prior to dialysis decreasing to two out of 25 patients postdialysis (p < 0.03). Orthostatic responses predialysis did not differ from those in the control group. Review of the literature shows great variability in definition of normal Valsalva and postural (30:15 R—R interval) ratios. Diabetic patients in the current and prior studies were more likely to have abnormal responses. In conclusion, the prevalence of autonomic dysfunction in chronic dialysis patients as determined by Valsalva and 30:15 ECG postural ratios may be influenced by the following factors: when subjects are studied with respect to their dialysis treatment; the number of subjects with diabetes; and the cut-off point used to define abnormal test results. Abnormal Valsalva ratios are less frequent when measured postdialysis.