![]() ![]() Hyperviscosity with IgG myeloma circulating as a monomer with a molecular weight of ∼180 kDa often requires a level in excess of 10 000 mg/dL. The median IgM level producing hyperviscosity in Waldenström macroglobulinemia (WM), reported from the University of California San Francisco (UCSF), is in the range of 5000 mg/dL. IgM, with its molecular weight of 950 kDa, has a high axial length-to-width ratio and, therefore, has high intrinsic viscosity and raises the plasma viscosity at levels far below those of plasma proteins such as IgG and IgA. This is true of both fibrinogen 13 in plasma and immunoglobulins in serum. Large linear proteins spin end over end and raise viscosity disproportionately. Spherical proteins rotate through the plasma and contribute very little. The 3-dimensional structure of the protein is important. In serum and plasma, proteins determine the viscosity level. Serum and plasma viscosity management, however, should always be based on a direct measurement of serum viscosity even if intervention is required before the results subsequently become available, as was done in the patient presented. Because measurement of viscosity by this technique requires the construction of a standard curve, the test is usually reserved for central laboratories where the volume of samples justifies the production of a control curve. 11 The increased power required in sera with increased viscosity is calibrated by standards of known viscosity and can be completed in 15 minutes. This requires between 0.65 and 1.5 mL of serum and operates on the principle of the power required to oscillate a probe at constant rate. Mayo Medical Laboratories uses the Sonoclot Coagulation Analyzer, which can do coagulation testing, thromboelastography, 10 as well as viscosity measurement. 9 Today, in commercial laboratories, mechanical direct measurement is preferred because the Oswald tube requires 5 mL of serum and requires experienced technicians for it to be reproducible. The ratio between the 2 flow times determines the relative viscosity of the fluid. It involves the use of a stopwatch to measure the flow in seconds, first of water and then remeasuring serum or plasma. 8 This requires significant technical expertise to be reproducible. Its use dates back to the turn of the 20th century and involves measuring the flow of serum or plasma through a capillary tube connected via a U-tube to 2 reservoirs. Historically, this was done using the Ostwald viscosimeter. The measurement of viscosity is done in a viscosimeter. Salvage chemotherapy was initiated but failed, and the patient died 17 days later of refractory multiple myeloma. Although epistaxis resolved immediately, the patient’s mentation did not clear and he remained somnolent. The viscosity was then measured as 1.8 cP. A second plasma exchange was performed the following day 3535 mL of plasma were removed and were replaced with 3302 mL of albumin over 70 minutes. After the first plasma exchange, the viscosity was reduced to 3.6 cP. The serum viscosity came back at 13.6 centipoise (cP). A serum viscosity was drawn and sent to the laboratory while plasma exchange was initiated 3479 mL of plasma was removed and replaced with 3304 mL of normal serum albumin over 68 minutes. Total protein was 12.3 g/dL, M spike was 6.6 g/dL, and quantitative immunoglobulin was 7220 mg/dL. His hemoglobin was 7.9 g/dL, and platelet count was 34 × 10 9/L. The epistaxis was both nostrils and could not be stopped with pressure or cautery. At 66 years of age, he presented with epistaxis, gait instability, and somnolence. Over a period of 8 years, he was treated with multiple chemotherapeutic regimens with response and subsequent relapse. A 58-year-old man was diagnosed with immunoglobulin A (IgA) κ multiple myeloma. ![]()
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