Blood Volume in the Hypothermic Dog

Abstract

In nembutalized dogs chilled to 20[degree]C by immersion in an iced bath, circulating plasma (PV) and erythrocyte (RV) volumes were measured with T 1824- and p32-tagged cells, respectively; and hematocrit ratios (Hct) by spinning at 3000 rpm for 30 min. Mixing of both dye and tagged cells was found complete at 45 min. (normal body temp.) and 45-60 min. (20[degree]). Plasma protein concns. were computed from either specific gravity as measured against CuSO4 or refractometrically. Differences from normal noted at 20[degree] follow: RV, -2.6% [plus or minus] 2.1; PV, -12.8% [plus or minus] 1.5; plasma protein concn., -1.7% [plus or minus] 1.1; Hct, [plus or minus] 15.2% [plus or minus] 1.7. Previous studies on tissue water (muscle, liver, heart) in dogs chilled to the same temp. showed no measurable increases at expense of plasma. An apparent increase in RV of 18-33% obatins at 20[degree] when calculated from PV and Hct. It thus appears that neither specific gravity nor Hct are reliable indices of blood volume change in hypothermia. The data suggest rather that erythrocytes and some 87% of the plasma are confined to a smaller than normal vascular bed, with some 13% of the plasma sequestered in vessels from which erythrocytes are excluded.