Hemodynamics — MCQs

A 65-year-old man comes to the physician for a routine examination. He feels well. His pulse is 80/min and blood pressure is 140/85 mm Hg. Cardiac examination shows a holosystolic murmur in the 4th intercostal space along the left sternal border that gets louder during inspiration. The increase of this patient's murmur is best explained by which of the following hemodynamic changes?

Q32

A 34-year-old male is brought to the emergency department by fire and rescue following a motor vehicle accident in which the patient was an unrestrained driver. The paramedics report that the patient was struck from behind by a drunk driver. He was mentating well at the scene but complained of pain in his abdomen. The patient has no known past medical history. In the trauma bay, his temperature is 98.9°F (37.2°C), blood pressure is 86/51 mmHg, pulse is 138/min, and respirations are 18/min. The patient is somnolent but arousable to voice and pain. His lungs are clear to auscultation bilaterally. He is diffusely tender to palpation on abdominal exam with bruising over the left upper abdomen. His distal pulses are thready, and capillary refill is delayed bilaterally. Two large-bore peripheral intravenous lines are placed to bolus him with intravenous 0.9% saline. Chest radiograph shows multiple left lower rib fractures. Which of the following parameters is most likely to be seen in this patient?

Hemodynamics US Medical PG Practice Questions and MCQs

Question 31: A 65-year-old man comes to the physician for a routine examination. He feels well. His pulse is 80/min and blood pressure is 140/85 mm Hg. Cardiac examination shows a holosystolic murmur in the 4th intercostal space along the left sternal border that gets louder during inspiration. The increase of this patient's murmur is best explained by which of the following hemodynamic changes?

A. Increased systemic venous compliance
B. Decreased pulmonary vessel capacity
C. Decreased left ventricular preload
D. Increased peripheral vascular resistance
E. Increased right ventricular stroke volume (Correct Answer)

Explanation: ***Increased right ventricular stroke volume*** - The murmur's location at the **left sternal border** in the 4th intercostal space, combined with its **holosystolic** nature and **inspiratory increase**, points to **tricuspid regurgitation**. - During **inspiration**, intrathoracic pressure decreases, leading to **increased venous return** to the right side of the heart, thereby increasing the **right ventricular stroke volume** and the intensity of a right-sided murmur. *Increased systemic venous compliance* - An increase in systemic venous compliance would cause a **decrease in venous return** to the right heart due to venous pooling, which would **decrease** the intensity of right-sided murmurs. - This condition would lead to a reduction in preload, not an increase needed to augment the murmur. *Decreased pulmonary vessel capacity* - A decrease in pulmonary vessel capacity would primarily affect **pulmonary hypertension** and right ventricular afterload, rather than directly increasing right ventricular stroke volume or the intensity of a tricuspid regurgitation murmur during inspiration. - It would hinder blood flow from the right ventricle to the pulmonary artery, not enhance it. *Decreased left ventricular preload* - While deep inspiration can mildly decrease left ventricular preload due to pooling of blood in the pulmonary circulation, this effect is relevant for **left-sided murmurs** and would cause their intensity to **decrease**. - This change would not explain the observed increase in a right-sided murmur. *Increased peripheral vascular resistance* - Increased peripheral vascular resistance would primarily affect the **left side of the heart** as the left ventricle would have to pump against a higher afterload. - This would typically **increase** the intensity of **left-sided murmurs** like aortic stenosis or mitral regurgitation but would not directly explain the inspiratory increase of a right-sided murmur.

Question 32: A 34-year-old male is brought to the emergency department by fire and rescue following a motor vehicle accident in which the patient was an unrestrained driver. The paramedics report that the patient was struck from behind by a drunk driver. He was mentating well at the scene but complained of pain in his abdomen. The patient has no known past medical history. In the trauma bay, his temperature is 98.9°F (37.2°C), blood pressure is 86/51 mmHg, pulse is 138/min, and respirations are 18/min. The patient is somnolent but arousable to voice and pain. His lungs are clear to auscultation bilaterally. He is diffusely tender to palpation on abdominal exam with bruising over the left upper abdomen. His distal pulses are thready, and capillary refill is delayed bilaterally. Two large-bore peripheral intravenous lines are placed to bolus him with intravenous 0.9% saline. Chest radiograph shows multiple left lower rib fractures. Which of the following parameters is most likely to be seen in this patient?

A. Increased cardiac output
B. Increased mixed venous oxygen saturation
C. Decreased pulmonary capillary wedge pressure (Correct Answer)
D. Decreased systemic vascular resistance
E. Increased right atrial pressure

Explanation: ***Decreased pulmonary capillary wedge pressure*** - The patient presents with classic signs of **hemorrhagic shock** (hypotension, tachycardia, somnolence, abdominal bruising, thready pulses) due to trauma, likely involving the spleen or kidney given the left upper abdominal bruising and rib fractures. - **Decreased pulmonary capillary wedge pressure (PCWP)** is expected in hypovolemic shock because it reflects left atrial and left ventricular end-diastolic pressure, which will be low due to reduced venous return and intravascular volume. *Increased cardiac output* - In **hemorrhagic shock**, the body attempts to compensate by increasing heart rate, but overall **cardiac output is typically decreased** due to profound reduction in preload (venous return) from blood loss. - While heart rate is elevated, the stroke volume is severely diminished, leading to a net decrease in cardiac output despite compensatory efforts. *Increased mixed venous oxygen saturation* - **Mixed venous oxygen saturation (SvO2)** is generally **decreased in hemorrhagic shock** due to increased oxygen extraction by tissues. - Inadequate oxygen delivery to the tissues forces them to extract more oxygen from the blood, leading to a lower SvO2. *Decreased systemic vascular resistance* - In **hemorrhagic shock**, the body activates compensatory mechanisms, including generalized **vasoconstriction**, to maintain blood pressure and prioritize blood flow to vital organs. - This leads to an **increased systemic vascular resistance (SVR)**, not decreased, as reflected by the thready distal pulses and delayed capillary refill. *Increased right atrial pressure* - **Right atrial pressure (RAP)**, representing CVP, is typically **decreased in hemorrhagic shock** due to reduced circulating blood volume. - A lower RAP indicates decreased venous return to the heart, a hallmark of hypovolemia.

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