Summary
Heparin enhances the inhibition rate of thrombin by both antithrombin III (AT III)
and heparin cofactor II (HC II). We studied the activity of these two plasma proteins
in patients with chronic renal failure (CRF) undergoing regular hemodialysis as their
heparin requirements varied widely. In 77 normal blood donors, normal ranges (mean
± 2 SD) were 82-122% for AT III and 65-145% for HC II. When compared with these controls
82 dialyzed CRF patients had a subnormal AT III activity and a significantly (p <0.001)
lower HC II activity. To evaluate the effect of hemodialysis we compared AT III, HC
II and total proteins in plasma before and after dialysis in. 24 patients (12 with
normal and 12 with low basal HC II activity). AT III and HC II activities significantly
(p <0.001) increased in absolute value. When related to total plasma proteins, in
order to suppress the influence of hemoconcentration induced by dialysis, AT III decreased
significantly (p <0.01) whereas HC II increased slightly but significantly (p <0.01)
in the 12 patients with low initial HC II activity. The decrease of AT III induced
by heparin administrated during dialysis is likely to account for this relative decrease
of AT III activity. A modification of the distribution of both HC II and heparin between
the vascular wall and the circulating blood is evoked to explain the relative increase
in HC II activity and the need for higher heparin dosage in patients with low HC II
levels.
Keywords
Antithrombin III - Heparin cofactor II - Chronic renal failure - Hemodialysis - Heparin
