Effects of 4-dimethylaminophenol, Co2EDTA, or NaNO2 on cerebral blood flow and sinus blood homeostasis of dogs in connection with acute cyanide poisoning.

The effects of the cyanide antidotes DMAP, Co2EDTA, and NaNO2 on cerebral blood flow (CBF) and cerebral blood gases were investigated in connection with acute poisoning of dogs by cyanide. The substances were injected intravenously. Local CBF as measured with thermocouples in the cingulum increased by 100-200% after a non-lethal dose of KCN (1 mg/kg) and by 50% after injection of NaNO2 (15 mg/kg), that oxidized some 20% of the total hemoglobin to ferrihemoglobin. Co2EDTA (10 mg/kg) induced a decrease in local CBF of 30% and in brain temperature of 0.5 degree C. The temperature diminished also after poisoning by KCN, but it rose by 0.15 degree C after the administration of NaNO2. Local CBF and sinus sagittalis blood flow increased by 60-160% for about 15 min, and the brain temperature decreased by 0.4-0.5 degree C when DMAP (3.25 mg/kg) or Co2EDTA (15 mg/kg) was injected 1 min after poisoning by cyanide (4 mg/kg), a dose that always caused respiratory arrest. Immediately after injection of DMAP the brain temperature rose transiently by 0.1-0.2 degree C. Co2EDTA did not exert such an effect. In the sinus sagittalis blood of artificially ventilated animals pCO2 decreased rapidly by 10-20 mmHg after poisoning and approached the initial level after treatment with DMAP or Co2EDTA. The highest value of pO2 was about 80 mmHg and 50 mmHg after injection of DMAP and Co2EDTA, respectively; thereafter pO2 declined to 20 mmHg or 40 mmHg at 20 min. The lactate concentration increased by 60-70% without tendency to return to normal.