Illnesses can often lead to fever and dehydration. how might these symptoms affect a person’s cardiovascular system? a. fever and dehydration increase body temp. and fluids, which decrease a person's heart rate and respiration. b. fever and dehydration increases body temp. and fluids decreases the amount of fluids, which increases a person's heart rate and respiration. c fever and dehydration increase body temp and decreases in the amount of fluids, which decrease the viscosity of the blood. d fever and dehydration increases body temp and fluids, which increase the viscosity of the blood.