Plasma includes water, ions, proteins, nutrients, hormones, Plasma= 55% wastes, etc The hematocrit is a Leukocytes and buffy coat platelets rapid assessment of blood composition It is the percent of the Erythrocytes =45% (hematocrit= 45%) blood volume that is composed of RBCs (red blood cellsPlasma includes water, ions, proteins, nutrients, hormones, wastes, etc. The hematocrit is a rapid assessment of blood composition. It is the percent of the blood volume that is composed of RBCs (red blood cells)