Characteristic parameters derived from whole-blood viscometry: Their potential utility in diagnosis and therapy

Recently, Whittington and Harkness (1) showed how whole-blood viscosities, as measured in a concentric-cylinder apparatus, could, in principle, be inferred from capillary-tube measurements made at rates of shear up to 1,000 times those in the rotary machine. Two invariant parameters, “A” and “β” were postulated. “A” is the relative whole-blood viscosity at unit rate of shear and 1% haematocrit; and “β” is the shear-sensitivity exponent. The ability of these parameters to discriminate between normal, hyperproteinaemic and sickle-cell bloods will now be demonstrated. It will be suggested that A and β may also be more useful indicators of haemorheo1ogica1 reaction to surgery and drug-therapy than the data arising from whole-blood viscometry as usually presented. Hitherto, this art has generally implied the measurement of viscosity at selected constant shear-rates, often with a “correction” to an arbitrary haematocrit value. The new approach is to presume that A and β are constant characteristics of the blood-sample, quite independent of the haematocrit at withdrawal, and of the stresses imposed upon the blood during measurement.