Final answer:
An adult with major trauma is time-critical if they exhibit severe bleeding, low blood pressure, and multiple injuries, which are indicative of hypovolemic shock. In critical situations without known blood type, type O negative blood is transfused because it is universally compatible and lacks the most common antigens that cause reactions.
Step-by-step explanation:
In the setting of major trauma, an adult is considered time-critical if they meet criteria such as severe bleeding, low blood pressure, and multiple injuries. These conditions may lead to hypovolemic shock, which is a life-threatening state where the circulatory system cannot maintain sufficient blood flow to supply oxygen and other nutrients to the tissues.
Following a motor vehicle accident where a patient presents with multiple traumatic injuries and severe bleeding, there may be insufficient time to determine the patient's blood type. In such a case, universal donor blood, type O negative, is typically transfused. This type of blood is safe for most recipients because it lacks the A, B, and Rh antigens, which are the most common causes of blood transfusion reactions.
Hypovolemic shock is characterized by symptoms such as a rapid heart rate, a thready pulse, cool and clammy skin, rapid and shallow breathing, and thirst. Immediate treatment with intravenous fluids, blood transfusions, and potentially vasopressor medications is critical to managing the condition and preventing the worsening of the patient's state.