A 15-year-old teenager presents for a sports physical. His blood pressure is 110/70 mm Hg, temperature is 36.5°C (97.7°F), and heart rate is 100/min. On cardiac auscultation, an early diastolic heart sound is heard over the cardiac apex while the patient is in the left lateral decubitus position. A transthoracic echocardiogram is performed which shows an ejection fraction of 60% without any other abnormalities. Which of the following is the end-systolic volume in this patient if his cardiac output is 6 L/min?
Q22
A 41-year-old woman presents to her primary care provider reporting abdominal pain. She reports a three-hour history of right upper quadrant sharp pain that started an hour after her last meal. She denies nausea, vomiting, or changes in her bowel habits. She notes a history of multiple similar episodes of pain over the past two years. Her past medical history is notable for type II diabetes mellitus, major depressive disorder, and obesity. She takes glyburide and sertraline. Her temperature is 98.6°F (37°C), blood pressure is 140/85 mmHg, pulse is 98/min, and respirations are 18/min. On examination, she is tender to palpation in her right upper quadrant. She has no rebound or guarding. Murphy’s sign is negative. No jaundice is noted. The hormone responsible for this patient’s pain has which of the following functions?
Q23
An 83-year-old male presents with dyspnea, orthopnea, and a chest radiograph demonstrating pulmonary edema. A diagnosis of congestive heart failure is considered. The following clinical measurements are obtained: 100 bpm heart rate, 0.2 mL O2/mL systemic blood arterial oxygen content, 0.1 mL O2/mL pulmonary arterial oxygen content, and 400 mL O2/min oxygen consumption. Using the above information, which of the following values represents this patient's cardiac stroke volume?
Q24
A 72-year-old man arrives at the emergency department 30 minutes after developing rapid onset right-sided weakness and decreased sensation on the right side of his body. The patient’s wife also reports that he has had difficulty forming sentences. His wife adds that these symptoms were at their maximum within a few minutes of the incident and began to resolve almost instantaneously. The patient says he had a related episode of painless visual loss in his left eye that resolved after about 10–20 minutes about 3 months ago. His past medical history includes diabetes mellitus type 2 and essential hypertension. The patient reports a 50 pack-year smoking history. His blood pressure is 140/60 mm Hg, and his temperature is 36.5°C (97.7°F). Neurological examination is significant for a subtle weakness of the right hand. A noncontrast CT scan of the head is unremarkable, and a carotid Doppler ultrasound shows 10% stenosis of the right internal carotid artery and 50% stenosis of the left internal carotid artery. Which of the following is the expected change in resistance to blood flow through the stenotic artery most likely responsible for this patient’s current symptoms?
Q25
A 57-year-old man is admitted to the burn unit after he was brought to the emergency room following an accidental fire in his house. His past medical history is unknown due to his current clinical condition. Currently, his blood pressure is 75/40 mmHg, pulse rate is 140/min, and respiratory rate is 17/min. The patient is subsequently intubated and started on aggressive fluid resuscitation. A Swan-Ganz catheter is inserted to clarify his volume status. Which of the following hemodynamic parameters would you expect to see in this patient?
Q26
A 69-year-old woman is admitted to the hospital with substernal, crushing chest pain. She is emergently moved to the cardiac catheterization lab where she undergoes cardiac angiography. Angiography reveals that the diameter of her left anterior descending artery (LAD) is 50% of normal. If her blood pressure, LAD length, and blood viscosity have not changed, which of the following represents the most likely change in LAD flow from baseline?
Q27
A 55-year-old woman is brought to the emergency department because of worsening upper abdominal pain for 8 hours. She reports that the pain radiates to the back and is associated with nausea. She has hypertension and hyperlipidemia, for which she takes enalapril, furosemide, and simvastatin. Her temperature is 37.5°C (99.5 °F), blood pressure is 84/58 mm Hg, and pulse is 115/min. The lungs are clear to auscultation. Examination shows abdominal distention with epigastric tenderness and guarding. Bowel sounds are decreased. Extremities are warm. Laboratory studies show:
Hematocrit 48%
Leukocyte count 13,800/mm3
Platelet count 175,000/mm3
Serum:
Calcium 8.0 mg/dL
Urea nitrogen 32 mg/dL
Amylase 250 U/L
An ECG shows sinus tachycardia. Which of the following is the most likely underlying cause of this patient's vital sign abnormalities?
Q28
A 28-year-old woman is brought to the emergency department 1 hour after being involved in a motor vehicle collision. She was riding a bike when she lost control and hit a car on the opposite side of the road. On arrival, she is unconscious. She has a history of intravenous heroin use. Her pulse is 56/min, respirations are 8/min and irregular, and blood pressure is 196/102 mm Hg. Examination shows a 2-cm laceration over the left cheek and a 3-cm laceration over the left chest. There are multiple abrasions over her face and chest. She opens her eyes and flexes her extremities to painful stimuli. The pupils are dilated and react sluggishly to light. There are decreased breath sounds over the left lung. The trachea is central. There is no jugular venous distention. Cardiac examination shows no abnormalities. The abdomen is soft and nontender. The left knee and right ankle are swollen; range of motion is limited. Two large-bore peripheral intravenous catheters are inserted. She is intubated and mechanical ventilation is initiated. A focused assessment with sonography in trauma is negative. An occlusive dressing is applied over the left chest wound. She is scheduled for a noncontrast CT scan of the brain. Which of the following is the underlying cause of this patient's hypertension?
Q29
A 45-year-old man comes to his primary care provider for a routine visit. The patient mentions that while he was cooking 5 days ago, he accidentally cut himself with a meat cleaver and lost the skin at the tip of his finger. After applying pressure and ice, the bleeding stopped and he did not seek treatment. The patient is otherwise healthy and does not take any daily medications. The patient’s temperature is 98.2°F (36.8°C), blood pressure is 114/72 mmHg, pulse is 60/min, and respirations are 12/min. On exam, the patient demonstrates a 0.5 x 0.3 cm wound on the tip of his left third finger. No bone is involved, and the wound is red, soft, and painless. There are no signs of infection. Which of the following can be expected on histopathological examination of the wounded area?
Q30
A peripheral artery is found to have 50% stenosis (50% reduction in cross-sectional area). Therefore, compared to a normal artery with no stenosis, by what factor has the flow of blood been decreased?
Hemodynamics US Medical PG Practice Questions and MCQs
Question 21: A 15-year-old teenager presents for a sports physical. His blood pressure is 110/70 mm Hg, temperature is 36.5°C (97.7°F), and heart rate is 100/min. On cardiac auscultation, an early diastolic heart sound is heard over the cardiac apex while the patient is in the left lateral decubitus position. A transthoracic echocardiogram is performed which shows an ejection fraction of 60% without any other abnormalities. Which of the following is the end-systolic volume in this patient if his cardiac output is 6 L/min?
A. 50 mL
B. 40 mL (Correct Answer)
C. 60 mL
D. 120 mL
E. 100 mL
Explanation: **Correct: 40 mL**
- Cardiac output (CO) = Heart Rate (HR) × Stroke Volume (SV). Given CO = 6000 mL/min and HR = 100 beats/min, SV = CO / HR = 6000 mL / 100 = **60 mL**.
- Ejection fraction (EF) = SV / End-diastolic volume (EDV). Given EF = 60% = 0.60 and SV = 60 mL, EDV = SV / EF = 60 mL / 0.60 = **100 mL**.
- SV = EDV - End-systolic volume (ESV). We need to find ESV, so ESV = EDV - SV = 100 mL - 60 mL = **40 mL**.
*Incorrect: 50 mL*
- This value would imply different stroke volume or end-diastolic volume calculations, which do not align with the given cardiac output, heart rate, and ejection fraction.
- An ESV of 50 mL would result in an EF of (100 - 50) / 100 = 50%, which is lower than the given 60%.
*Incorrect: 60 mL*
- This value is equal to the calculated stroke volume (SV), not the end-systolic volume (ESV).
- If ESV were 60 mL and EDV were 100 mL, the SV would be 40 mL, which would not yield the given cardiac output.
*Incorrect: 120 mL*
- This value is higher than the calculated end-diastolic volume (EDV) of 100 mL, and ESV must be less than EDV.
- This would lead to a negative stroke volume, which is physiologically impossible.
*Incorrect: 100 mL*
- This value represents the calculated end-diastolic volume (EDV), not the end-systolic volume (ESV).
- If ESV were 100 mL and EDV were 100 mL, the stroke volume would be 0, and the ejection fraction would be 0%.
Question 22: A 41-year-old woman presents to her primary care provider reporting abdominal pain. She reports a three-hour history of right upper quadrant sharp pain that started an hour after her last meal. She denies nausea, vomiting, or changes in her bowel habits. She notes a history of multiple similar episodes of pain over the past two years. Her past medical history is notable for type II diabetes mellitus, major depressive disorder, and obesity. She takes glyburide and sertraline. Her temperature is 98.6°F (37°C), blood pressure is 140/85 mmHg, pulse is 98/min, and respirations are 18/min. On examination, she is tender to palpation in her right upper quadrant. She has no rebound or guarding. Murphy’s sign is negative. No jaundice is noted. The hormone responsible for this patient’s pain has which of the following functions?
A. Promote gallbladder relaxation
B. Increase pancreatic bicarbonate secretion
C. Promote relaxation of the sphincter of Oddi (Correct Answer)
D. Increase growth hormone secretion before meals
E. Promote migrating motor complexes
Explanation: ***Promote relaxation of the sphincter of Oddi***
- This patient's symptoms (postprandial RUQ pain, obesity, absence of rebound/guarding, negative Murphy's sign) are highly suggestive of **biliary colic** due to **cholelithiasis** (gallstones).
- The hormone primarily responsible for this patient's condition is **cholecystokinin (CCK)**, which is released from the duodenal mucosa in response to fatty meals.
- CCK has **two coordinated actions**: it causes **gallbladder contraction** to expel bile AND **relaxation of the sphincter of Oddi** to allow bile flow into the duodenum.
- Both functions are essential for normal bile delivery, making this the correct answer regarding CCK's physiologic functions.
*Increase pancreatic bicarbonate secretion*
- **Secretin**, not CCK, is the hormone primarily responsible for stimulating the pancreas to release **bicarbonate-rich fluid** to neutralize gastric acid entering the duodenum.
- While CCK does stimulate pancreatic enzyme secretion (amylase, lipase, proteases), it is not the primary regulator of bicarbonate secretion.
*Promote gallbladder relaxation*
- This is incorrect; CCK **promotes gallbladder contraction** to expel bile, not relaxation.
- Gallbladder relaxation is the default interdigestive state and does not cause the acute, postprandial pain seen in biliary colic.
- In biliary colic, CCK-induced gallbladder contraction against an obstructed cystic duct (by a gallstone) causes the characteristic pain.
*Increase growth hormone secretion before meals*
- Growth hormone secretion is primarily regulated by **growth hormone-releasing hormone (GHRH)** and **somatostatin**, not by gastrointestinal hormones.
- Growth hormone release is related to sleep-wake cycles and metabolic state, not nutrient intake or meal timing.
- This function is unrelated to the pathophysiology of biliary colic.
*Promote migrating motor complexes*
- **Motilin** is the hormone responsible for promoting **migrating motor complexes (MMCs)** during the interdigestive phase (between meals) to clear the gut of undigested material.
- MMCs occur in the fasting state, whereas this patient's symptoms are clearly **postprandial** (after meals), making this mechanism irrelevant to her presentation.
Question 23: An 83-year-old male presents with dyspnea, orthopnea, and a chest radiograph demonstrating pulmonary edema. A diagnosis of congestive heart failure is considered. The following clinical measurements are obtained: 100 bpm heart rate, 0.2 mL O2/mL systemic blood arterial oxygen content, 0.1 mL O2/mL pulmonary arterial oxygen content, and 400 mL O2/min oxygen consumption. Using the above information, which of the following values represents this patient's cardiac stroke volume?
A. 30 mL/beat
B. 70 mL/beat
C. 40 mL/beat (Correct Answer)
D. 60 mL/beat
E. 50 mL/beat
Explanation: ***40 mL/beat***
- First, calculate cardiac output (CO) using the **Fick principle**: CO = Oxygen Consumption / (Arterial O2 content - Venous O2 content). Here, CO = 400 mL O2/min / (0.2 mL O2/mL - 0.1 mL O2/mL) = 400 mL O2/min / 0.1 mL O2/mL = **4000 mL/min**.
- Next, calculate stroke volume (SV) using the formula: SV = CO / Heart Rate. Given a heart rate of 100 bpm, SV = 4000 mL/min / 100 beats/min = **40 mL/beat**.
*30 mL/beat*
- This answer would result if there was an error in calculating either the **cardiac output** or if the **arteriovenous oxygen difference** was overestimated.
- A stroke volume of 30 mL/beat with a heart rate of 100 bpm would yield a cardiac output of 3 L/min, which is sub-physiologic for an oxygen consumption of 400 mL/min given the provided oxygen content values.
*70 mL/beat*
- This stroke volume is higher than calculated and would imply either a significantly **lower heart rate** or a much **higher cardiac output** than derived from the Fick principle with the given values.
- A stroke volume of 70 mL/beat at a heart rate of 100 bpm would mean a cardiac output of 7 L/min, which is inconsistent with the provided oxygen consumption and arteriovenous oxygen difference.
*60 mL/beat*
- This value is higher than the correct calculation, suggesting an error in the initial calculation of **cardiac output** or the **avO2 difference**.
- To get 60 mL/beat, the cardiac output would need to be 6000 mL/min, which would mean an avO2 difference of 0.067 mL O2/mL, not 0.1 mL O2/mL.
*50 mL/beat*
- This stroke volume would result from an incorrect calculation of the **cardiac output**, potentially from a slight miscalculation of the **arteriovenous oxygen difference**.
- A stroke volume of 50 mL/beat at 100 bpm would mean a cardiac output of 5 L/min, requiring an avO2 difference of 0.08 mL O2/mL, which is not consistent with the given values.
Question 24: A 72-year-old man arrives at the emergency department 30 minutes after developing rapid onset right-sided weakness and decreased sensation on the right side of his body. The patient’s wife also reports that he has had difficulty forming sentences. His wife adds that these symptoms were at their maximum within a few minutes of the incident and began to resolve almost instantaneously. The patient says he had a related episode of painless visual loss in his left eye that resolved after about 10–20 minutes about 3 months ago. His past medical history includes diabetes mellitus type 2 and essential hypertension. The patient reports a 50 pack-year smoking history. His blood pressure is 140/60 mm Hg, and his temperature is 36.5°C (97.7°F). Neurological examination is significant for a subtle weakness of the right hand. A noncontrast CT scan of the head is unremarkable, and a carotid Doppler ultrasound shows 10% stenosis of the right internal carotid artery and 50% stenosis of the left internal carotid artery. Which of the following is the expected change in resistance to blood flow through the stenotic artery most likely responsible for this patient’s current symptoms?
A. It will double
B. No change
C. It will be 8 times greater
D. It will be 4 times greater
E. It will be 16 times greater (Correct Answer)
Explanation: ***It will be 16 times greater***
- According to **Poiseuille's law**, resistance to blood flow is inversely proportional to the fourth power of the radius (R ∝ 1/r⁴).
- In vascular medicine, **50% stenosis** refers to a 50% reduction in the vessel **diameter**, which also means the radius is reduced by 50% (halved).
- When the radius is halved, resistance increases by a factor of (1/0.5)⁴ = 2⁴ = **16 times**.
- The **left internal carotid artery** with 50% stenosis is responsible for the patient's symptoms (right-sided weakness and aphasia indicate left hemisphere pathology).
*It will be 8 times greater*
- This would occur if the radius were reduced to approximately 63% of its original size (1/0.63⁴ ≈ 8).
- This does not correspond to a 50% stenosis.
*It will double*
- A doubling of resistance would occur if the radius were reduced by approximately 16% (to 84% of original).
- This represents much less severe stenosis than described in this case.
*It will be 4 times greater*
- A four-fold increase would result from reducing the radius by approximately 29% (to 71% of original).
- This would correspond to approximately 30% stenosis by diameter, not 50%.
*No change*
- Any degree of **stenosis** reduces the vessel radius and significantly increases resistance according to Poiseuille's law.
- A 50% stenosis causing a 16-fold increase in resistance can critically reduce blood flow, especially during periods of increased demand or reduced perfusion pressure, leading to **TIA** symptoms as seen in this patient.
Question 25: A 57-year-old man is admitted to the burn unit after he was brought to the emergency room following an accidental fire in his house. His past medical history is unknown due to his current clinical condition. Currently, his blood pressure is 75/40 mmHg, pulse rate is 140/min, and respiratory rate is 17/min. The patient is subsequently intubated and started on aggressive fluid resuscitation. A Swan-Ganz catheter is inserted to clarify his volume status. Which of the following hemodynamic parameters would you expect to see in this patient?
Explanation: ***Cardiac output: ↓, systemic vascular resistance: ↑, pulmonary artery wedge pressure: ↓***
- The patient's **hypotension (75/40 mmHg)** and **tachycardia (140/min)**, combined with severe burns, indicate **hypovolemic shock** due to massive fluid loss from damaged capillaries.
- In response to decreased cardiac output and hypovolemia, the body compensates by increasing **systemic vascular resistance (SVR)** to maintain perfusion to vital organs, and **pulmonary artery wedge pressure (PAWP)** will be low due to reduced intravascular volume.
*Cardiac output: ↓, systemic vascular resistance: ↔, pulmonary artery wedge pressure: ↔*
- This option incorrectly suggests that systemic vascular resistance and pulmonary artery wedge pressure would be normal, which is inconsistent with **hypovolemic shock**.
- In shock, the body's compensatory mechanisms would lead to significant changes in SVR and PAWP, not maintain them at baseline.
*Cardiac output: ↑, systemic vascular resistance: ↑, pulmonary artery wedge pressure: ↔*
- Increased cardiac output is usually seen in **distributive shock** (e.g., septic shock) where vasodilation leads to reduced SVR, not increased SVR as suggested here.
- An elevated SVR coupled with an increased cardiac output would typically result in a higher blood pressure unless there is a compensatory drop in other parameters.
*Cardiac output: ↑, systemic vascular resistance: ↓, pulmonary artery wedge pressure: ↔*
- This pattern (high cardiac output, low SVR) is characteristic of **distributive shock**, such as **septic shock** or anaphylactic shock, rather than the hypovolemic shock expected in a burn patient.
- Severe burns primarily cause massive fluid shifts, leading to hypovolemia and a reduced cardiac output, not an elevated one.
*Cardiac output: ↔, systemic vascular resistance: ↔, pulmonary artery wedge pressure: ↔*
- This scenario represents **normal hemodynamic parameters**, which would not be expected in a patient experiencing severe shock from extensive burns.
- The patient's clinical presentation (hypotension, tachycardia) clearly indicates a state of hemodynamic instability.
Question 26: A 69-year-old woman is admitted to the hospital with substernal, crushing chest pain. She is emergently moved to the cardiac catheterization lab where she undergoes cardiac angiography. Angiography reveals that the diameter of her left anterior descending artery (LAD) is 50% of normal. If her blood pressure, LAD length, and blood viscosity have not changed, which of the following represents the most likely change in LAD flow from baseline?
A. Decreased by 93.75% (Correct Answer)
B. Increased by 6.25%
C. Decreased by 25%
D. Decreased by 87.5%
E. Increased by 25%
Explanation: ***Decreased by 93.75%***
- This option is correct based on Poiseuille's Law, which states that flow is proportional to the **fourth power of the radius (r^4)**. A 50% decrease in diameter means a 50% decrease in radius (0.5r).
- The new flow would be (0.5)^4 = 0.0625 times the original flow. Therefore, the decrease in flow is 1 - 0.0625 = 0.9375, or **93.75%**.
*Increased by 6.25%*
- This answer incorrectly suggests an **increase** in flow, which is contrary to the effect of a narrowed artery.
- While 6.25% represents the new flow as a percentage of baseline (since 0.0625 = 6.25%), the vessel stenosis causes a **decrease**, not an increase in flow.
*Decreased by 25%*
- This calculation might arise from considering a linear relationship (e.g., radius decreases by 50%, so flow decreases by 50% of 50%, which is incorrect).
- It does not account for the **fourth power relationship** between radius and flow according to Poiseuille's Law.
*Decreased by 87.5%*
- This percentage represents a calculation error, likely from misapplying the fourth power relationship or confusing the calculation steps.
- It does not accurately reflect the dramatic reduction in flow caused by a 50% reduction in vessel diameter.
*Increased by 25%*
- This option implies a significant increase in blood flow, which would not happen with a **stenosed artery**.
- It completely contradicts the physiological response to a **narrowed vessel**.
Question 27: A 55-year-old woman is brought to the emergency department because of worsening upper abdominal pain for 8 hours. She reports that the pain radiates to the back and is associated with nausea. She has hypertension and hyperlipidemia, for which she takes enalapril, furosemide, and simvastatin. Her temperature is 37.5°C (99.5 °F), blood pressure is 84/58 mm Hg, and pulse is 115/min. The lungs are clear to auscultation. Examination shows abdominal distention with epigastric tenderness and guarding. Bowel sounds are decreased. Extremities are warm. Laboratory studies show:
Hematocrit 48%
Leukocyte count 13,800/mm3
Platelet count 175,000/mm3
Serum:
Calcium 8.0 mg/dL
Urea nitrogen 32 mg/dL
Amylase 250 U/L
An ECG shows sinus tachycardia. Which of the following is the most likely underlying cause of this patient's vital sign abnormalities?
A. Hemorrhagic fluid loss
B. Capillary leakage (Correct Answer)
C. Decreased cardiac output
D. Decreased albumin concentration
E. Increased excretion of water
Explanation: ***Capillary leakage***
- The patient's presentation with **pancreatitis** (epigastric pain radiating to the back, nausea, elevated amylase, epigastric tenderness, guarding) can lead to widespread **capillary leakage** and **third-space fluid sequestration**.
- This leakage results in **intravascular volume depletion**, manifesting as **hypotension** (84/58 mm Hg) and **tachycardia** (115/min), despite seemingly normal extremities.
*Hemorrhagic fluid loss*
- While bleeding can cause similar vital sign changes, a **hematocrit of 48%** makes significant acute hemorrhage unlikely.
- There are no other clinical signs of bleeding, such as **ecchymosis** or **melena**.
*Decreased cardiac output*
- While ultimately leading to hypotension and tachycardia, **decreased cardiac output** in this context is a *consequence* of **intravascular hypovolemia due to capillary leakage**, not the primary underlying cause.
- The underlying issue is the loss of effective circulating volume, not pump failure.
*Decreased albumin concentration*
- **Hypoalbuminemia** contributes to reduced plasma oncotic pressure and can worsen capillary leakage and edema, but it is typically a more chronic condition and not the immediate primary cause of acute, rapid intravascular volume depletion leading to shock in this setting.
- The presented vital signs suggest a more immediate and acute fluid shift.
*Increased excretion of water*
- **Increased water excretion**, such as from **diuretic use** (furosemide), could contribute to hypovolemia, but the acute and severe nature of the patient's symptoms along with signs of peritonitis and elevated amylase point more strongly to pancreatitis-induced fluid shifts as the primary cause.
- Furthermore, pancreatitis itself is a significant driver of fluid loss into the retroperitoneum and peritoneal cavity.
Question 28: A 28-year-old woman is brought to the emergency department 1 hour after being involved in a motor vehicle collision. She was riding a bike when she lost control and hit a car on the opposite side of the road. On arrival, she is unconscious. She has a history of intravenous heroin use. Her pulse is 56/min, respirations are 8/min and irregular, and blood pressure is 196/102 mm Hg. Examination shows a 2-cm laceration over the left cheek and a 3-cm laceration over the left chest. There are multiple abrasions over her face and chest. She opens her eyes and flexes her extremities to painful stimuli. The pupils are dilated and react sluggishly to light. There are decreased breath sounds over the left lung. The trachea is central. There is no jugular venous distention. Cardiac examination shows no abnormalities. The abdomen is soft and nontender. The left knee and right ankle are swollen; range of motion is limited. Two large-bore peripheral intravenous catheters are inserted. She is intubated and mechanical ventilation is initiated. A focused assessment with sonography in trauma is negative. An occlusive dressing is applied over the left chest wound. She is scheduled for a noncontrast CT scan of the brain. Which of the following is the underlying cause of this patient's hypertension?
A. Elevated sympathetic response
B. Increased intrathoracic pressure
C. Reduced parasympathetic response
D. Posttraumatic vasospasm
E. Brainstem compression (Correct Answer)
Explanation: ***Brainstem compression***
- The patient's presentation with **hypertension**, **bradycardia**, and **irregular respirations** (Cushing's triad) in the setting of severe head trauma is highly indicative of **increased intracranial pressure (ICP)** leading to brainstem compression.
- Brainstem compression, often due to a mass effect from hemorrhage or edema, impairs the brainstem's ability to regulate vital functions, resulting in this classic triad.
*Elevated sympathetic response*
- While trauma typically triggers an **elevated sympathetic response** leading to tachycardia and hypertension, the presence of **bradycardia** in this patient makes a purely sympathetic surge less likely to be the underlying cause of her hypertension.
- The elevated blood pressure combined with a low heart rate points away from an unopposed sympathetic activation.
*Increased intrathoracic pressure*
- An increase in intrathoracic pressure, as seen in conditions like **tension pneumothorax**, can impair venous return and cardiac output, typically leading to **hypotension**, not hypertension.
- Although the patient has decreased breath sounds on the left, an occlusive dressing was applied, and a FAST exam was negative for significant fluid, making this less likely the cause of hypertension.
*Reduced parasympathetic response*
- A reduced parasympathetic response would generally lead to **tachycardia** rather than bradycardia, as the vagal tone would be diminished.
- The observed bradycardia, therefore, contradicts a primary issue of reduced parasympathetic activity.
*Posttraumatic vasospasm*
- **Posttraumatic vasospasm** can occur after severe brain injury, but it typically does not directly manifest as immediate, severe hypertension accompanied by bradycardia and respiratory irregularities (Cushing's triad).
- Vasospasm usually contributes to cerebral ischemia and can develop hours to days after the initial injury, not typically as the acute cause of these profound vital sign changes.
Question 29: A 45-year-old man comes to his primary care provider for a routine visit. The patient mentions that while he was cooking 5 days ago, he accidentally cut himself with a meat cleaver and lost the skin at the tip of his finger. After applying pressure and ice, the bleeding stopped and he did not seek treatment. The patient is otherwise healthy and does not take any daily medications. The patient’s temperature is 98.2°F (36.8°C), blood pressure is 114/72 mmHg, pulse is 60/min, and respirations are 12/min. On exam, the patient demonstrates a 0.5 x 0.3 cm wound on the tip of his left third finger. No bone is involved, and the wound is red, soft, and painless. There are no signs of infection. Which of the following can be expected on histopathological examination of the wounded area?
A. Platelet aggregates
B. Epithelial cell migration from the wound borders
C. Neutrophil migration into the wound
D. Deposition of type III collagen (Correct Answer)
E. Deposition of type I collagen
Explanation: ***Deposition of type III collagen***
- Five days post-injury, the **proliferative phase of wound healing** is active, characterized by the formation of an initial **granulation tissue** matrix primarily composed of **Type III collagen**.
- This type of collagen forms thinner, more flexible fibers that provide a temporary scaffold for tissue regeneration before being gradually replaced by stronger Type I collagen.
*Platelet aggregates*
- **Platelet aggregation** occurs immediately after injury as part of **hemostasis**, forming a plug to stop bleeding.
- By five days, this initial phase would have concluded, and the primary focus would be on tissue repair and regeneration.
*Epithelial cell migration from the wound borders*
- **Epithelial cell migration** for re-epithelialization typically occurs within the first 24-48 hours after injury, forming a new epidermal layer over the wound.
- While it continues, the dominant histological feature at day 5 in an open wound of this size would be **granulation tissue formation** in the dermis.
*Neutrophil migration into the wound*
- **Neutrophil migration** is a hallmark of the **inflammatory phase**, peaking within 24-48 hours post-injury to clear debris and microbes.
- By day 5, the inflammatory phase would be subsiding, and macrophages would be more prevalent, signaling the transition to the proliferative phase.
*Deposition of type I collagen*
- **Type I collagen** is the predominant collagen found in mature scar tissue and is deposited during the later **remodeling phase** of wound healing.
- While some Type I collagen may be present, **Type III collagen** is characteristic of the early granulation tissue prominent at day 5.
Question 30: A peripheral artery is found to have 50% stenosis (50% reduction in cross-sectional area). Therefore, compared to a normal artery with no stenosis, by what factor has the flow of blood been decreased?
A. 8
B. 2
C. 32
D. 16
E. 4 (Correct Answer)
Explanation: ***4***
- According to **Poiseuille's Law**, blood flow is proportional to the fourth power of the radius (Flow ∝ r⁴).
- If the cross-sectional area is reduced by 50%, the new area is 0.5 times the original. Since Area = πr², we have: πr_new² = 0.5πr_original², which gives r_new = √0.5 × r_original ≈ 0.707 × r_original.
- The new flow becomes: Flow_new ∝ (0.707r)⁴ = (0.707)⁴ × r⁴ = 0.25 × r⁴.
- Therefore, the flow is reduced to **1/4 of the original**, meaning it has decreased by a factor of **4**.
*8*
- This would only be correct if flow were proportional to r³ (the cube of radius), which does not apply to laminar blood flow.
- Poiseuille's Law establishes a **fourth-power relationship** between radius and flow, not a cubic relationship.
*2*
- A factor of 2 would imply either a linear relationship between flow and radius, or only a minimal stenosis (~16% area reduction).
- This significantly **underestimates** the impact of a 50% area reduction on blood flow through the vessel.
*32*
- This represents an excessive reduction that would only occur if flow were proportional to r⁵ or higher.
- With 50% area stenosis and the r⁴ relationship, the mathematical result is a factor of **4**, not 32.
*16*
- This would be the correct answer if "50% stenosis" referred to a **50% reduction in diameter** (radius) rather than area.
- With 50% diameter reduction: r_new = 0.5r, so Flow_new ∝ (0.5r)⁴ = 0.0625r⁴, giving a decrease by factor of 16.
- However, the question specifies **area reduction**, making this option incorrect.
