How can hemodialysis-associated hypotension and dialysis-induced symptoms be explained and controlled--particularly in diabetic and arteriosclerotic patients?

ABSTRACT

Patients with diabetes and/or severe arteriosclerosis are often unable to tolerate volume removal during hemodialysis (HD) and develop hemodialysis-induced symptoms. These problems can be omitted by well-balanced correction of the acid/base status. We compared 20 high-risk patients which were either treated with standard HD (dialysate bicarbonate 33 mmol/l, treatment A) or treated with standard HD and additional administration of NaHCO3 (120-160 ml 8.4% NaHCO3 solution over the venous line during HD) to correct the metabolic acidosis to upper normal values (treatment B). The following parameters were compared 1. Acid/base status; 2. EEG monitoring and clinical observation of dialysis-induced symptoms; 3. Invasive monitoring of circulation by Swan-Ganz thermodilution; 4. Ventilation, oxygen consumption and lactate production. Optimal correction of acid/base values resulted in symptom-free hemodialysis sessions with stable PaCO2 in the normal range, cardiovascular stability assessed by invasive monitoring, normal ventilation and higher oxygen consumption and decreased lactate production. Optimal correction of acid/base balance further led to the absence of EEG alterations and of dialysis-induced symptoms during treatment B as compared to treatment A. The baroreceptor response in these patients is usually disturbed due to sclerosis of the pressosensible vessels, especially the aortic arch and the pulmonary arteries impairing a compensatory increase of heart rate upon volume removal. However, chemoreceptors are able to increase sympathetic tone with preservation of blood pressure in this situation. In addition a decrease of PaO2 during volume removal can only be answered by an early increase of ventilation response due to stimulation of chemoreceptors provided that PaCO2 is maintained normal. Furthermore, normal cerebral blood flow also depends on a normal PaCO2. Based on these pathophysiological mechanisms the therapeutic strategy of additional bicarbonate administration to correct the acid/base status guarantees a stable normal PaCO2 and facilitates a symptom-free HD in high-risk patients.