In patients with leukemia and very high white blood cell counts, the whole blood viscosity may rarely increase sufficient to cause the hyperviscosity syndrome.



(1) increased minimum apparent whole blood viscosity

(2) presence of appropriate symptoms

(3) improvement following therapy to reduce the white blood cell count

(4) exclusion of other conditions


Minimum apparent whole blood viscosity:

(1) Direct measurement of viscosity is usually not readily available.

(2) This can be estimated from the type of leukemia, the white blood cell count and the hematocrit (see previous section).

(3) There is no absolute correlation between viscosity and symptom onset or severity.

(4) According to Baer et al, hyperviscosity in CLL tends to occur with a WBC count > 500,000 per µL. This correlates with an "observed" leukocrit of about 14. With a normal hematocrit, this would be associated with an apparent viscosity of 4.8 centipoise.

(5) According to Figure 6, Lichtman 1982 (page 282) an apparent viscosity > 4.5 centipoise is needed for hyperviscosity.


Symptoms of hyperviscosity:

(1) ocular: retinal hemorrhage, diplopia, nystagmus, visual blurring, papilledema, retinal vein distention

(2) neurologic: headache, slurred speech, seizure, vertigo, ataxic gait

(3) ear: hearing loss, tinnitus

(4) congestive heart failure

(5) increased bleeding


Differential diagnosis:

(1) leukostasis

(2) chemotherapy effect

(3) infection

(4) thromboembolic phenomenon


To read more or access our algorithms and calculators, please log in or register.