Objective assessment of heparin requirements for hemodialysis in humans.

The abilities of four heparin regimens to inhibit activation of blood coagulation, fibrinolysis, and the platelet release reaction in humans during renal dialysis have been assessed by visible examination of the extracorporeal circulation and by use of radioimmunoassays to FPA, beta 15-42 antigen, beta gamma G, and PF4. A subcutaneous injection of 5000 IU of heparin administered 1 hour before dialysis in two patients was either unable to sustain dialysis because of excess fibrin formation or allowed elevated plasma FPA and beta gamma G concentrations during dialysis. Injection of 10,000 IU heparin s.c. in five patients could sustain dialysis in only three patients for 5 hours, and allowed progressively increasing concentrations of FPA, beta gamma G, and PF4, as well as fibrin formation, in the extracorporeal circulation. A lower dose of heparin administered intravenously (2500 IU bolus plus 1000 IU/hr) to six patients was also unable to prevent elevations in FPA and beta gamma G 4 hours and 5 hours after the initiation of dialysis. Intravenous administration of heparin at a dose of 5000 IU bolus plus 1500 IU/hr completely suppressed generation of FPA during 5-hour dialysis and was free of visible fibrin formation in the extracorporeal circulation in 13 patients. The concentration of the fibrinolytic system marker beta 15-42 antigen did not change significantly in any of the regimens, and the concentration of PF4 altered in response to infused heparin as well as to inadequate heparinization. We conclude that complete inhibition of activation of coagulation and suppression of the platelet release reaction occurs when high plasma heparin levels (greater than or equal to 0.5 IU/ml) are maintained during dialysis: lower heparin levels may be compatible with dialysis in some patients, but they allow generation of fibrin and the platelet release reaction, which pose a potential risk to the dialysis procedure and to the patient.