Is dialysis hypotension caused by an abnormality of venous tone?

The role of peripheral vascular tone in the development of hypotension induced by dialysis was investigated in eight patients undergoing haemodialysis with acetate or bicarbonate buffered fluid. Each patient had two sessions of dialysis with acetate fluid and two with bicarbonate fluid in the order acetate, bicarbonate, bicarbonate, acetate or bicarbonate, acetate, acetate, bicarbonate. Mean arterial blood pressure fell at a mean rate of 3.9 mm Hg/hour during dialysis with acetate fluid and 1.4 mm Hg/hour during dialysis with bicarbonate fluid. The rate of fall was significantly greater during dialysis with acetate fluid compared with bicarbonate fluid. Heart rate increased by a mean rate of 2.6 beats/min/hour during dialysis with both acetate and bicarbonate fluid. Vascular resistance in the forearm increased at a rate of 3.6 units/hour during dialysis with acetate fluid and 4.5 units/hour during dialysis with bicarbonate fluid, but the venous bed of the forearm dilated. The index of venous tone rose at a mean rate of 0.23 ml/dl [corrected] over 40 mm Hg/hour during dialysis with acetate fluid and 0.20 ml/dl over 40 mm Hg/hour during dialysis with bicarbonate fluid. Inappropriate peripheral venodilatation may be important in the development of hypotension induced by dialysis.