Abstract:The plasma concentrations of dopamine (DA), adrenaline (AD) and noradrenaline (NA) were measured during 29 routine hemodialysis (HD) treatments on 13 patients to determine whether any changes occurred in the concentrations of these substances during HD. All of the 13 patients studied demonstrated a fall in mean arterial pressure (MAP) when HD was commenced. Decreased concentrations of all three catecholamines were also demonstrated after the first hour of dialysis. Plasma AD rose after two hours, but NA and DA were still significantly lower than pre‐dialysis values at the end of HD. Study of 12 further patients during the first hour of HD confirmed that the NA level had fallen significantly by the fifteenth minute of HD, while the DA and AD levels took somewhat longer to fall. Both NA and DA were present in the dialysate in substantial amounts. Although the fall in MAP which accompanies HD is probably multifactorial, the loss of plasma catecholamines during HD may possibly contribute to the hemodynamic change