Intradialytic hypotension in relation to pre-existent autonomic dysfunction in hemodialysis patients

After having monitored haemodynamics during haemodialysis, we examined autonomic nervous function in rest prior to a next dialysis session in 28 patients on chronic intermittent haemodialysis. The aim was to compare intradialytically hypotensive with stable patients to assess whether blood pressure regulating mechanisms were related to basal autonomic function, assessed as heart rate variability (HRV) tested by means of the deep breathing test, the lying-to-standing test, and the Valsalva maneuver. Impedance cardiography was used to determine stroke volume and cardiac output during dialysis. In addition, blood pressure was registered automatically and systemic vascular resistance calculated. Blood volume variation was monitored by an on-line optical device. Intradialytic hypotension was observed in 10 patients (36%). Systemic vascular resistance in hypotensive patients decreased considerably (-14.0+/-5.9%), while it increased in stable patients (+9.9+/-4.6%, p = 0.004). Heart rate rose significantly in hypotensive patients (11.5+/-3.8%) in comparison to stable patients (-0.2+/-2.8%, p = 0.02). However, no significant differences in autonomic function were observed between hypotensive and stable patients. Although both groups showed impaired autonomic function, no significant correlation between changes in haemodynamics during dialysis and autonomic function at rest could be ascertained. In conclusions, hypotension during haemodialysis is not related to a patient's autonomic function at rest. This suggests that structural neuronal differences are not responsible for the severe decrease in systemic vascular resistance in intradialytic hypotension.