Fibrin deposits in the Kiil dialyser

Plasma levels and effects of sulfinpyrazone in patients requiring chronic hemodialysis

Sulfinpyrazone (Anturane), which inhibits platelet synthesis of prostaglandins and platelet release of serotonin, was given to patients with chronic renal failure requiring hemodialysis. Patients were mateched in double-blind fashion to receive either placebo or sulfinpyrazone at 200 mg orally three times a day. Peak plasma levels of sulfinpyrazone after the first 200-mg dose ranged from 6.7 to 11.4 micrograms/ml (mean : 8.7 micrograms/ml). The plasma concentration showed a monoexponential disappearance pattern with an apparent half-life of 4 hours. At steady state, sulfinpyrazone peak plasma levels were 10.7 to 30.1 micrograms/ml. Residual plasma levels 12 hours after a final dose while in steady state were 3.7 and 4.3 micrograms/ml. Sulfinpyrazone protected against falls of platelet counts normally encountered during hemodialysis. Sulfinpyrazone blocked the increased platelet aggregability and the platelet uptake and release of serotonin normally seen following dialysis. Sulfinpyrazone prevented the consumption of antithyrombin III which is normally seen with hemodialysis, without having changed the anticoagulant efficacy of heparin. Sulfinpyrazone can be given to patients with chronic renal failure. It prevents platelet consumption during hemodialysis and protects against the decrement of antithyrombin III normally seen during hemodialysis.

Platelet and fibrin(ogen) deposition in the artificial kidney. The influence of haematocrit, fibrin monomer and platelet inhibitors. An in vitro study

The effect of variations in haematocrit (hct) on the retention of 51Cr-labelled platelets and 125I-labelled fibrinogen from normal, heparinized, human blood, circulated in an experimental "mini-Kiil" dialyzing system, was studied. Platelet retention (PR) on dialysis membranes and blood lines was found to increase with increasing hct. When only platelet rich plasma was circulated, a significantly lower PR was noted on the blood lines. Fibrin(ogen) deposition on the same surfaces showed a similar tendency. When 125I-labelled fibrin monomer was added to normal blood, prior to dialysis, fibrin deposition on the membranes and blood lines was of a much higher degree than in the control. However, PR was not significantly influenced by the presence or deposition of the fibrin monomer. Reduced platelet function, caused by incubation with acetylsalicylic acid prior to dialysis, led to less PR on the blood lines, but not on the membranes. The observed difference was, however, not statistically significant (p = 0.06). Pretreatment of platelets with prostaglandin E1, however, was able to reduce PR significantly both on dialysis membranes and blood lines.

Thrombus formation in the artificial kidney. Platelet and fibrin(ogen) content of experimental thrombi detected by radioisotope technique

In vitro studies in a "mini-Kiil" dialyser showed that, in spite of presumably adequate heparinization (2.5 IU/ml plasma), 51Cr-labelled platelets and 125I-labelled fibrin(ogen) deposited on membranes and blood lines, when freshly drawn human blood was dialyzed for 30 min. Platelet retention dominated, with a Cr/I ratio 3 times that of blood. Increasing the heparin concentration led to a reduction both of 51Cr- and 125I-activity, with a slight fall in the Cr/I ratio. Heparin was unable to prevent platelet retention in the dialyser, but the platelet aggregating effect of heparin was shown to be of minor importance compared to its anticoagulant activity and effect on thrombin induced platelet aggregation. Platelet retention by the blood lines exceeded that of the dialyser, in spite of a much smaller surface area. Differences in thrombogenicity between cuprophane and silicone rubber as well as different flow characteristics in the two situations were probably contributory. When heparinized tubing was used, the radioactivity retained was negligible, but membrane radioactivity was unaltered. A considerable reduction in blood radioactivity during dialysis, not accounted for by the deposits above, suggests the additional formation of more loosely attached platelet/fibrin(ogen) masses.

Impaired anticoagulant effect of heparin in the artificial kidney. An experimental study

Dialysis of blood and plasma was performed in vitro, in a 'mini-Kill' dialyser as well as in dialysis bags. A marked shortening of the thrombin-clotting time was observed, indicating fall in heparin anticoagulant effect. The concentration of heparin, however, as measured by polybrene titration, was substantially less reduced. Fibrin formation, as evidenced by the ethanol gelation test, occurred more often in the dialysed than in the control plasma. In conclusion, the discrepancy between concentration and anticoagulant effect of heparin could be partly explained by influx from the dialysate of calcium, magnesium, and acetate ions. The fibrin-polymerizing effect of these ions was confirmed by a shortening of the clotting time with Reptilase, a proteolytic enzyme not influenced by thrombin inhibitors such as heparin. In addition, liberation of platelet factor 4 may be responsible for some reduction in antithrombin activity of heparin. No evidence of heparin being dialysed or adhering to the dialysis membrane was found.