EFFECTS OF POTASSIUM AND LACTIC-ACID AN VENTILATION IN ANESTHETIZED CATS

Intravenous infusions of lactic acid alone, KCl alone and both togethe r were administered to anaesthetized, spontaneously breathing cats. Ve ntilation (VI), end-tidal P-O2 (PET(O2)), end-tidal PCO2 (PET(CO2)), a rterial blood pressure and heart rate were recorded continuously. [K+] a and pHa were monitored using intravascular ion selective catheter el ectrodes. The increase in VI during infusion of KCI and lactic acid to gether was greater than that observed during infusion of lactic acid a lone. The increment in VI produced by the addition of an infusion of K Cl to the lactic acid infusion was greater than the increment produced by the addition of KCl to a control infusion of normal saline. The re duction in Pa-CO2 which occurred when KCl was added to the lactic acid infusion was similar to that when KCl was infused with NaCl. Thus the inhibition of respiration secondary to reduced Pao(CO2) was similar i n both circumstances. These results suggest that the combined respirat ory stimulant effect of elevation of [K+]a and acute lactic acidosis i s more than additive.