Efficacy of single or repeated hemoperfusion in a canine model of paraquat poisoning.

Although hemoperfusion has been used to treat paraquat poisoning, its efficacy has been widely debated. This study examines the kinetic and pathologic correlates of paraquat toxicity and hemoperfusion and the efficacy of hemoperfusion in four groups of four dogs. This species was chosen because the kinetics and toxicity of paraquat are similar to those in the human. All dogs given a lethal dose of paraquat dichloride producing 100% mortality as a 2-hr infusion (7.48 mg of paraquat ion per kg) developed the typical clinical, laboratory and pathologic features of paraquat toxicity and died within 5 to 7 days. All dogs given paraquat and hemoperfused for 8 hr daily, beginning at 12 hr, died within 3 to 6 days. Two of four dogs which were hemoperfused once, beginning at 2 hr, survived. One dog in the repeated hemoperfusion only group died from blood loss. Negligible amounts of paraquat (0.4-2.0% of the total dose) were adsorbed during repeated hemoperfusion because of extensive excretion of paraquat in urine and sequestration in peripheral tissues from which redistribution was slow. The efficacy in the single early hemoperfusion group can be attributed to removal of 25% of the dose by the procedure in the two survivors. We conclude that single hemoperfusion may have some clinical application in patients who present within a few hours of the ingestion and have not ingested a dose of paraquat that is multiples of the lethal dose producing 100% mortality. It is doubtful if there is any role for repeated hemoperfusion.