Home › HPCSA Board Exam › Physiology › Blood Vessels and Circulation › Regulatory mechanisms are effective enough that …
Regulatory mechanisms are effective enough that a bleeding patient may remain asymptomatic until roughly what fraction of blood volume is lost?
AAbout 2 to 5 percent
BAbout 30 to 40 percent
CAbout 10 to 20 percent
DAbout 45 to 55 percent
Answer & Solution
Correct answer: C. About 10 to 20 percent
1. Falling blood volume lowers both pressure and flow, and that state is called hypovolemia.
2. Compensating mechanisms defend blood pressure so well that early losses produce no symptoms.
3. A patient may stay asymptomatic until 10 to 20 percent of blood volume has gone.
4. This is exactly why an apparently comfortable trauma patient still needs intravenous fluid replacement.
5. Losses approaching half of blood volume would be far past the silent window and well into shock.
_Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 20 "The Cardiovascular System: Blood Vessels and Circulation", section 20.2 Blood Flow, Blood Pressure, and Resistance_
Related questions
A vessel carrying blood at high pressure close to the heart will have walls that are:The endothelium is described as physiologically critical to regulating capillary exchange Vasoconstriction in arteries occurs when smooth muscle contracts in which layer?In arteries, vasoconstriction makes the lumen narrower and has what effect on blood flow?Endothelins constricting vessel smooth muscle have what effect on blood pressure?The endothelium releases local chemicals called endothelins that can do what to smooth musWhich components of arterial blood pressure are named alongside systolic and diastolic?Which reading is given as a normal adult blood pressure?