The initial step in hemostasis is the vascular spasm, which is the immediate constriction of damaged blood vessels. This vasoconstriction reduces blood flow to the injured area, limiting blood loss and providing time for subsequent processes like platelet plug formation and coagulation to occur. Without this rapid vessel narrowing, hemostasis would be less effective, leading to increased bleeding. This mechanism is crucial during surgery or trauma to quickly control hemorrhage before more complex hemostatic stages initiate.

Reference: Robbins Basic Pathology, Kumar, Abbas, Aster, 10th Edition.