A SYSTEM FOR AUTOMATIC FEEDBACK-CONTROL OF PLASMA POTASSIUM CONCENTRATION

A system is described for automatic feedback control of plasma potassium concentration in experimental animals. Plasma potassium was monitored continuously and the signal compared with the desired plasma potassium concentration. The resulting error signal controlled the infusion rates of a concentrated potassium chloride solution (50 or 200 mmol litre-1) and a solution of 50% glucose with insulin 200 u litre-1. Plasma potassium was increased or decreased to the desired concentration at various rates, dictated by the controller constants. Increases were achieved significantly faster than reductions. The system may prove useful for elucidating the fate of infused potassium and for determining the optimum rate of insulin infusion in hyperkalaemia. If adapted for clinical use, it may find applications in the management of various abnormalities of potassium homeostasis.