Dehydration would:
(a) Cause an increase in the hematocrit
(b) Cause a decrease in the hematocrit
(c) Have no effect on the hematocrit
(d) Cause an increase in plasma volume

Verified step by step guidance

1. Step 1: Understand what hematocrit is. Hematocrit is the percentage of red blood cells (RBCs) in the total blood volume. It is calculated as: \(\text{Hematocrit} = \frac{\text{Volume of RBCs}}{\text{Total blood volume}} \times 100\%\).
2. Step 2: Consider what happens during dehydration. Dehydration causes a loss of water from the body, which reduces the plasma (fluid) volume in the blood but does not immediately change the number of red blood cells.
3. Step 3: Analyze the effect of reduced plasma volume on hematocrit. Since plasma volume decreases but RBC volume remains relatively constant, the ratio of RBC volume to total blood volume increases.
4. Step 4: Conclude the effect on hematocrit. Because the denominator (total blood volume) decreases due to less plasma, the hematocrit value increases.
5. Step 5: Eliminate other options based on this reasoning: (b) decrease in hematocrit and (d) increase in plasma volume are inconsistent with dehydration effects, and (c) no effect is unlikely because plasma volume changes.

Key Concepts

Hematocrit Definition

Hematocrit is the percentage of red blood cells (RBCs) in the total blood volume. It reflects the proportion of blood composed of cells versus plasma, and is commonly used to assess blood concentration and oxygen-carrying capacity.

Effects of Dehydration on Blood Volume

Dehydration reduces the body's total fluid volume, primarily decreasing plasma volume. This leads to a relative increase in the concentration of red blood cells, as the plasma component shrinks while RBC count remains constant.

Relationship Between Plasma Volume and Hematocrit

Since hematocrit is the ratio of RBC volume to total blood volume, a decrease in plasma volume (due to dehydration) raises hematocrit values. Conversely, an increase in plasma volume dilutes RBCs, lowering hematocrit.