Circulatory Anatomy, Physiology, and Perfusion Practice Questions

25 multiple-choice questions on Circulatory anatomy, physiology, and perfusion for paramedic and EMT students, from Chapter 31 (Bleeding). Read each question, pick your answer, then tap Show answer to check it and read the explanation.

25 practice questions

1. A cold, bleeding trauma patient begins shivering hard in the ambulance. This is harmful mainly because shivering:

   1. A. Directly worsens bleeding from the wound
   2. B. Lowers the blood pressure by vasodilation
   3. C. Raises oxygen demand when supply is low
   4. D. Is a sign that the shock has now resolved
   Show answer

   Answer: C. Raises oxygen demand when supply is low

   Shivering can raise metabolic rate several-fold, so muscles consume more oxygen at a time when delivery is already reduced, deepening the oxygen debt. Cover the patient, warm the cab, and use warmed fluids. Shivering is a heat-producing response, not vasodilation, it does not itself make a wound bleed, and it says nothing about shock resolving.

2. A patient with a high spinal cord injury is hypotensive from loss of vascular tone. In the perfusion triangle of pump, fluid, and container, which part has failed?

   1. A. The pump (the heart)
   2. B. The fluid (the blood volume)
   3. C. All three parts equally
   4. D. The container (vessels)
   Show answer

   Answer: D. The container (vessels)

   Loss of sympathetic tone dilates the vessels, so the same blood volume fills a larger container and pressure falls, which is the basis of neurogenic shock. The heart and blood volume are intact at first. Hemorrhage is a fluid problem and cardiogenic shock is a pump problem; recognizing which part failed guides treatment.

3. An 80-kg man has a circulating blood volume of about:

   1. A. 3.2 L
   2. B. 5.6 L
   3. C. 8.0 L
   4. D. 11.2 L
   Show answer

   Answer: B. 5.6 L

   Adult blood volume is about 70 mL/kg, so 80 kg × 70 mL = 5,600 mL. 8 L would assume 100 mL/kg, which overestimates adult volume and makes a given loss seem less serious than it is.

4. A 20-kg child has a circulating blood volume of about:

   1. A. 1.6 L
   2. B. 0.8 L
   3. C. 3.0 L
   4. D. 4.0 L
   Show answer

   Answer: A. 1.6 L

   Children have about 80 mL/kg of blood, so 20 kg × 80 mL = 1,600 mL. A loss of only 400 mL is therefore about 25% of this child's volume, which is why seemingly small bleeds matter in children.

5. A 70-year-old with known coronary artery disease is bleeding heavily from a leg wound. He develops chest pressure, and the monitor shows new ST depression. The most likely cause is:

   1. A. A clot blocking a coronary artery suddenly
   2. B. Low oxygen supply to a fast-working heart
   3. C. Coronary spasm triggered by the pain
   4. D. Potassium lost along with the blood
   Show answer

   Answer: B. Low oxygen supply to a fast-working heart

   Hemorrhage lowers oxygen delivery (fewer red cells, low diastolic pressure) while tachycardia raises myocardial demand, so narrowed coronary arteries cannot meet the need, producing supply-demand (type 2) ischemia. The treatment is to stop the bleeding and restore volume, not antiplatelet or clot-directed therapy. Pain does not typically cause coronary spasm, and whole blood loss removes potassium in proportion rather than creating hypokalemia, so neither explains new ST depression here.

6. A man with a bleeding leg wound feels faint and his radial pulse fades when rescuers sit him upright in a stair chair. The main cause is:

   1. A. A sudden rise in afterload from pain
   2. B. A drop in heart rate from vagal tone
   3. C. Less venous return and lower preload
   4. D. Better filling of the heart when upright
   Show answer

   Answer: C. Less venous return and lower preload

   When a volume-depleted patient sits up, blood pools in the legs, venous return falls, and the ventricles fill less, so stroke volume and blood pressure drop. Move him supine. Afterload is resistance to ejection and is not the problem here, a vagal drop in heart rate is not what is described, and upright posture worsens rather than improves filling.

7. According to the Frank-Starling mechanism, as blood loss reduces ventricular filling:

   1. A. Stroke volume falls
   2. B. Stroke volume rises
   3. C. Contractility doubles
   4. D. Afterload falls
   Show answer

   Answer: A. Stroke volume falls

   Within limits, more stretch produces a stronger contraction, so less filling produces a smaller stroke volume. The heart compensates with a faster rate, not with a larger stroke.

8. Afterload is determined mainly by:

   1. A. Venous return to the heart
   2. B. Circulating blood volume
   3. C. The resting heart rate per minute
   4. D. Systemic vascular resistance
   Show answer

   Answer: D. Systemic vascular resistance

   Afterload is the resistance the left ventricle pumps against, set mostly by arteriolar tone. Venous return and blood volume determine preload, the tempting but wrong choice.

9. Early in hemorrhage, a patient's cardiac output has fallen, yet his blood pressure is still normal. This is possible because:

   1. A. Blood pressure does not depend on output
   2. B. The lost blood was mainly from the veins
   3. C. His stroke volume has risen to replace it
   4. D. Vascular resistance has risen
   Show answer

   Answer: D. Vascular resistance has risen

   Blood pressure is roughly cardiac output x systemic vascular resistance, so sympathetic vasoconstriction can hold the pressure normal while output falls. This is why a normal blood pressure does not rule out shock. Stroke volume falls, not rises, with blood loss, and the source of the lost blood does not change the relationship.

10. At rest, most of the circulating blood volume is held in the:

    1. A. Arteries and arterioles
    2. B. Capillary beds
    3. C. Veins and venules
    4. D. Chambers of the heart
    Show answer

    Answer: C. Veins and venules

    The venous system is the capacitance side and holds roughly two thirds of the blood. Venoconstriction in hemorrhage shifts this reserve toward the heart; arterioles control resistance, not storage.

11. A bleeding patient whose blood pressure is held up by intense vasoconstriction becomes suddenly hypotensive after a large IV dose of morphine. The most likely reason is that the drug:

    1. A. Blunted his compensatory vasoconstriction
    2. B. Caused new bleeding at the wound site
    3. C. Increased his heart rate and stroke volume
    4. D. Raised the resistance in his arterioles
    Show answer

    Answer: A. Blunted his compensatory vasoconstriction

    A compensated patient depends on sympathetic tone and arteriolar constriction to keep his pressure up. Opioids and sedatives blunt that tone and release histamine (morphine), so pressure can fall sharply. In bleeding patients, give smaller, titrated doses (fentanyl is often preferred) and watch the blood pressure. The drug does not raise resistance or heart rate, and it does not cause new bleeding.

12. A man lost about 1 L of blood from a leg wound that is now controlled. Two hours later his hemoglobin is lower than on arrival. The most likely reason is that:

    1. A. His bone marrow has stopped making red cells
    2. B. Interstitial fluid has shifted into his vessels
    3. C. His kidneys are losing red cells in the urine
    4. D. His spleen has trapped a large share of red cells
    Show answer

    Answer: B. Interstitial fluid has shifted into his vessels

    As capillary hydrostatic pressure falls, fluid moves from the interstitium into the vessels (transcapillary refill), restoring volume but diluting the remaining red cells. The marrow response to bleeding takes days, and it increases rather than stops red cell production.

13. Two patients have the same degree of hemorrhagic shock. One is in shock for 20 minutes and the other for 2 hours before the bleeding is controlled. The second patient has a worse outlook mainly because:

    1. A. His blood pressure will be lower now
    2. B. He will need fewer units of blood later
    3. C. His bleeding source must be larger
    4. D. His oxygen debt built up for longer
    Show answer

    Answer: D. His oxygen debt built up for longer

    During shock, tissues receive less oxygen than they need, and the deficit (oxygen debt) accumulates with time as lactate and cell injury build up. The longer it lasts, the more likely organ damage becomes even after bleeding is stopped, which is why rapid hemorrhage control and transport matter. The duration, not a larger source or a lower current pressure, is what differs here.

14. According to the Fick principle, a trauma patient with an SpO2 of 99% can still have poor tissue oxygen delivery if:

    1. A. The heart rate rises above 100/min
    2. B. Plasma holds too little dissolved oxygen
    3. C. Too few red cells remain to carry oxygen
    4. D. The alveoli are well ventilated with air
    Show answer

    Answer: C. Too few red cells remain to carry oxygen

    Oxygen delivery requires oxygen loading, enough red cells to carry it, and enough flow to the tissues. SpO2 measures only the percentage of hemoglobin that is saturated, so it can be normal after much of the hemoglobin has been lost. Dissolved oxygen in plasma is a tiny share of delivery even in health, and a faster heart rate helps maintain flow rather than causing poor delivery.

15. A pale patient who has lost a large volume of blood has an SpO2 of 97% but no cyanosis. Cyanosis is absent mainly because:

    1. A. Too little hemoglobin remains to look blue
    2. B. His tissues are well oxygenated at present
    3. C. Pulse oximetry would read low if he were hypoxic
    4. D. Cyanosis only appears in children
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    Answer: A. Too little hemoglobin remains to look blue

    Cyanosis needs roughly 5 g/dL of deoxygenated hemoglobin in the capillaries. After severe blood loss there may not be enough hemoglobin to reach that level, so a patient can be dangerously short of oxygen delivery without turning blue. A normal SpO2 shows saturation, not oxygen content, and cyanosis is not limited to children.

16. A patient's blood pressure is 120/60 mmHg. The mean arterial pressure is about:

    1. A. 60 mmHg
    2. B. 80 mmHg
    3. C. 90 mmHg
    4. D. 100 mmHg
    Show answer

    Answer: B. 80 mmHg

    MAP is diastolic plus one third of the pulse pressure: 60 + (60 ÷ 3) = 80 mmHg. Simply averaging systolic and diastolic gives 90, which overstates MAP because the heart spends more time in diastole.

17. A 30-year-old trained marathon runner with a resting heart rate of 45/min was stabbed in the thigh. His heart rate is now 92/min. You should interpret this as:

    1. A. A normal heart rate needing no concern
    2. B. A large rise that may signal shock
    3. C. Proof that his blood loss is minimal
    4. D. A sign of a primary cardiac problem
    Show answer

    Answer: B. A large rise that may signal shock

    Vital signs should be judged against the patient's baseline. A doubling of heart rate in a conditioned athlete is significant tachycardia for him even though 92/min looks normal on paper, and well-trained young adults compensate strongly before they decompensate. A normal-range number does not prove minimal blood loss, and nothing suggests a primary cardiac cause.

18. During hemorrhage, sympathetic constriction of the veins helps maintain the circulation mainly by:

    1. A. Raising the resistance to ejection from the heart
    2. B. Slowing the heart to allow more filling
    3. C. Shifting stored venous blood toward the heart
    4. D. Pulling fluid out of the vessels into tissue
    Show answer

    Answer: C. Shifting stored venous blood toward the heart

    The veins hold most of the circulating blood at rest. When they constrict, part of that reservoir moves toward the heart, supporting venous return and preload. Arteriolar, not venous, constriction is what raises resistance to ejection. Sympathetic activity speeds the heart, and fluid shifts in hemorrhage move into, not out of, the vessels.

19. A patient in hemorrhagic shock becomes nauseated and vomits, although he has no abdominal injury. The most likely reason is:

    1. A. His stomach has filled with swallowed blood
    2. B. A head injury must be the hidden cause
    3. C. He is having a reaction to the dressing
    4. D. Blood flow to the gut has been shunted away
    Show answer

    Answer: D. Blood flow to the gut has been shunted away

    The sympathetic response diverts blood from the gut to the heart and brain, and the poorly perfused bowel commonly causes nausea and vomiting in shock. Be ready to protect the airway. Swallowed blood or a head injury can cause vomiting, but nothing here suggests either, and dressings do not cause this reaction.

20. A patient with a bleeding leg wound is pale and cool before any change in blood pressure. This is because the body:

    1. A. Shunts blood away from the skin
    2. B. Loses heat through the open wound
    3. C. Has used up its clotting factors
    4. D. Releases histamine into the skin
    Show answer

    Answer: A. Shunts blood away from the skin

    Sympathetic vasoconstriction diverts blood from the skin, gut, and kidneys to the heart and brain. Pale, cool skin is an early sign of compensation, not of heat loss through the wound.

21. A trauma patient is tachycardic and pale. A hemoglobin measured 15 minutes after injury is 14 g/dL. This value should be interpreted as:

    1. A. Unreliable, because it lags behind acute loss
    2. B. Proof that blood loss has been minimal
    3. C. Accurate, as long as it was drawn from an artery
    4. D. Low, since normal is 18 to 20 g/dL
    Show answer

    Answer: A. Unreliable, because it lags behind acute loss

    Whole blood is lost in proportion, so hemoglobin stays near baseline until fluid shifts or IV fluids dilute it. Treat the patient's perfusion signs, not an early normal number. The sampling site does not fix this lag, and 14 g/dL falls within the normal adult range, so it is not low.

22. A wounded patient's skin is pale, cool, and sweaty, and his pupils are slightly dilated. These findings are mainly produced by:

    1. A. Parasympathetic (vagal) stimulation
    2. B. Sympathetic stimulation
    3. C. Direct injury to the skin's vessels
    4. D. A drop in his core body temperature
    Show answer

    Answer: B. Sympathetic stimulation

    Blood loss triggers a sympathetic response and catecholamine release: skin vessels constrict (pale, cool), sweat glands are stimulated (diaphoresis), and the pupils dilate. Vagal stimulation would slow the heart and constrict the pupils, the findings are widespread rather than local, and hypothermia does not cause sweating.

23. Machinery completely severs a worker's arm above the elbow. Bleeding from the stump is less than you expected. The best explanation is that:

    1. A. The blood pressure in the arm has risen
    2. B. Platelets activate faster in a large, open wound
    3. C. The cut artery ends retracted and constricted
    4. D. Nearby veins are compressing the artery
    Show answer

    Answer: C. The cut artery ends retracted and constricted

    Smooth muscle in a fully severed artery pulls the ends back and narrows them, while a partial cut is held open by the intact wall. This reprieve may not last, so a tourniquet should still be applied to a traumatic amputation.

24. After 5 L of crystalloid for hemorrhage, a trauma patient develops swelling of the face, hands, and bowel. The main reason is that the fluid:

    1. A. Contained too much protein for the vessels
    2. B. Raised oncotic pressure inside the vessels
    3. C. Stayed entirely inside the blood vessels
    4. D. Diluted plasma proteins
    Show answer

    Answer: D. Diluted plasma proteins

    Large crystalloid volumes dilute albumin, lowering plasma oncotic pressure, and most of the fluid moves into the tissues within an hour, causing edema of the face, lungs, and bowel. This is one reason current practice limits crystalloid and favors blood. Crystalloids contain no protein, and oncotic pressure falls rather than rises.

25. Reduced urine output in a bleeding patient is caused mainly by:

    1. A. Damage to the bladder from trauma
    2. B. Loss of plasma proteins in the urine
    3. C. Increased glucose filtration in the injured kidney
    4. D. Low renal blood flow and fluid-saving hormones
    Show answer

    Answer: D. Low renal blood flow and fluid-saving hormones

    Renal vasoconstriction, aldosterone, and ADH all reduce urine output to conserve volume. Bladder injury can cause hematuria but is not the reason most bleeding patients make less urine.