Final answer:
An adult can experience vital signs changes with as little as 1 L of blood loss, which can lead to circulatory or hypovolemic shock.
Step-by-step explanation:
Significant vital signs changes, including increased heart and respiratory rates and a decreasing blood pressure, would likely occur if an 80-kg adult patient acutely loses as little as 1 L of blood. This is related to the concept of circulatory shock, specifically hypovolemic shock, where a rapid loss of blood volume causes a drop in blood pressure and an increase in heart rate as the body tries to compensate. An adult can be asymptomatic until 10-20% of the blood volume is lost; for an 80-kg adult (assuming a blood volume of approximately 7% of body weight), this is between 0.56 L and 1.12 L of blood before symptoms like these would manifest.