Blood hyperviscosity in cryoglobulinaemia: temperature sensitivity and correlation with reduced skin blood flow.

Cryoglobulins cause an increase in plasma viscosity and this has been attributed to increased protein-protein interaction. The purpose of the present study was to analyse the interaction between red cells and these proteins by measuring the viscosity of whold blood from 21 patients with cryoglobulinaemia not only at high (73 sec-1) and low (0.18 sec-1) shear rates, but also at different temperatures. At 35 degrees blood hyperviscosity was found in 62% of the patients at the high shear rate, and in 76% of patients at the low shear rate. Cooling of the blood to 25 degrees caused an increase in the blood viscosity which was particularly marked at the low shear rate. The plasma viscosity was significantly increased at both temperatures. The hand blood flow was measured at 32 degrees, 27 degrees and 20 degrees in 12 patients to assess the degree of impairment of the peripheral circulation. The flows were significantly reduced at each temperature and there was an increase in the sensitivity of the flow through this region to local cooling. These findings indicate that in the presence of a cryoglobulin there is an increased viscous resistance, particularly at low flow rates. The temperature and shear rate characteristics of the blood viscosity suggest that cryoglobulins markedly potentiate red cell aggregation. This explains, at lest in part, the high incidence of skin and vascular complications in patients with cryoglobulinaemia and the characteristic localization of these features to exposed peripheral tissues.