Podcast
Questions and Answers
Which of the following best describes the physiological basis of the Frank-Starling Law concerning cardiac function?
Which of the following best describes the physiological basis of the Frank-Starling Law concerning cardiac function?
- A greater end-diastolic volume leads to a more forceful contraction due to optimized overlap of actin and myosin filaments. (correct)
- Decreased preload causes a reduction in myocardial fiber length, leading to a more efficient contraction.
- Elevated afterload promotes increased myocardial stretch, resulting in a compensatory stronger contraction.
- Increased venous return elevates the heart rate, thereby enhancing cardiac output.
A patient presents with hypotension and signs of poor peripheral perfusion. Hemodynamic monitoring reveals a significantly elevated systemic vascular resistance (SVR). Which intervention would be MOST appropriate based on these findings?
A patient presents with hypotension and signs of poor peripheral perfusion. Hemodynamic monitoring reveals a significantly elevated systemic vascular resistance (SVR). Which intervention would be MOST appropriate based on these findings?
- Initiate vasodilator therapy to reduce SVR and improve left ventricular ejection. (correct)
- Administer a beta-blocker to decrease heart rate and myocardial oxygen demand.
- Increase the rate of the current vasopressor infusion to further elevate blood pressure.
- Administer a fluid bolus to increase preload and improve cardiac output.
A patient's pulmonary artery wedge pressure (PAOP) suddenly increases from 10 mm Hg to 22 mm Hg. Assuming cardiac output remains stable, which of the following is the MOST likely explanation for this change?
A patient's pulmonary artery wedge pressure (PAOP) suddenly increases from 10 mm Hg to 22 mm Hg. Assuming cardiac output remains stable, which of the following is the MOST likely explanation for this change?
- The patient has developed an acute increase in right ventricular contractility.
- The patient is experiencing acute mitral valve stenosis or regurgitation, increasing left atrial pressure. (correct)
- The patient has developed severe tricuspid valve stenosis, impeding right atrial emptying.
- The patient's systemic vascular resistance (SVR) has significantly decreased.
Following a severe myocardial infarction, a patient's left ventricular ejection fraction (LVEF) is measured at 30%. Based on this finding, which of the following compensatory mechanisms is the body MOST likely to employ to maintain adequate cardiac output?
Following a severe myocardial infarction, a patient's left ventricular ejection fraction (LVEF) is measured at 30%. Based on this finding, which of the following compensatory mechanisms is the body MOST likely to employ to maintain adequate cardiac output?
A patient with septic shock exhibits a cardiac index of 4.5 L/min/m² despite low systemic vascular resistance (SVR). Which of the following factors is MOST likely contributing to the patient's elevated cardiac index?
A patient with septic shock exhibits a cardiac index of 4.5 L/min/m² despite low systemic vascular resistance (SVR). Which of the following factors is MOST likely contributing to the patient's elevated cardiac index?
A patient is receiving mechanical ventilation with positive end-expiratory pressure (PEEP) of 10 cm H2O. How does PEEP potentially affect cardiac output?
A patient is receiving mechanical ventilation with positive end-expiratory pressure (PEEP) of 10 cm H2O. How does PEEP potentially affect cardiac output?
When calculating a patient's mean arterial pressure (MAP), why is the diastolic blood pressure weighted twice as much as the systolic blood pressure?
When calculating a patient's mean arterial pressure (MAP), why is the diastolic blood pressure weighted twice as much as the systolic blood pressure?
A patient with known heart failure is being assessed for fluid responsiveness using a passive leg raise (PLR). Which of the following hemodynamic changes would BEST indicate that the patient is likely to benefit from intravenous fluid administration?
A patient with known heart failure is being assessed for fluid responsiveness using a passive leg raise (PLR). Which of the following hemodynamic changes would BEST indicate that the patient is likely to benefit from intravenous fluid administration?
A patient's hemodynamic monitoring shows an elevated central venous pressure (CVP) of 18 mm Hg and a normal pulmonary artery wedge pressure (PAOP) of 10 mm Hg. Which of the following conditions is MOST likely responsible for these findings?
A patient's hemodynamic monitoring shows an elevated central venous pressure (CVP) of 18 mm Hg and a normal pulmonary artery wedge pressure (PAOP) of 10 mm Hg. Which of the following conditions is MOST likely responsible for these findings?
Which of the following parameters provides the MOST direct assessment of left ventricular contractility, independent of preload and afterload?
Which of the following parameters provides the MOST direct assessment of left ventricular contractility, independent of preload and afterload?
Flashcards
Hemodynamics
Hemodynamics
The pressures generated by blood flow, reflecting heart function, fluid balance and vessel condition.
Cardiac Output (CO)
Cardiac Output (CO)
Volume of blood ejected by the heart in one minute.
Stroke Volume (SV)
Stroke Volume (SV)
The amount of blood ejected by the ventricle with each heartbeat.
Preload
Preload
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Frank-Starling Law
Frank-Starling Law
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LVEDP (PAOP/PCWP/POP)
LVEDP (PAOP/PCWP/POP)
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Afterload
Afterload
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Calculating MAP
Calculating MAP
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Systemic Vascular Resistance (SVR)
Systemic Vascular Resistance (SVR)
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Pulmonary Vascular Resistance (PVR)
Pulmonary Vascular Resistance (PVR)
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Study Notes
- Hemodynamics involves the pressures generated by blood flow
- It provides information about heart function, fluid balance, and vessel health
- It ensures optimal tissue perfusion and oxygen delivery
- Hemodynamic monitoring is indicated in cases of shock, heart dysfunction, fluid imbalance, and to guide therapies during cardiovascular instability
- Hemodynamic monitoring technologies can be invasive or non-invasive
Pulmonary Artery Monitoring
- Pulmonary artery monitoring involves using a pulmonary artery catheter
Cardiac Output (CO)
- CO refers to the volume of blood the heart ejects in one minute
- CO is calculated by multiplying heart rate (HR) by stroke volume (SV), where CO = HR x SV
- Stroke volume is the amount of blood ejected by the ventricle with each heartbeat
- Determinants of stroke volume include preload, afterload, contractility, and the patient’s heart rate and rhythm
Preload, Afterload, Contractility, & Heart Rate
- Preload is influenced by ventricular compliance and venous return
- Afterload is influenced by systemic vascular resistance (SVR), aortic impedance, and blood viscosity
- Contractility is a factor
- Heart rate is affected by sympathetic stimulation and pharmacologic agents
Preload
- Preload is the stretch of myocardial muscle prior to contraction, created by volume in the ventricle
- Preload is equivalent to End Diastolic Volume
- Preload is determined by total circulating volume, distribution of volume, ventricular compliance, and atrial systole
- According to the Frank-Starling Law, greater stretch results in greater contraction
- Volume in the ventricle at end-diastole is preload
- LVEDP (PAOP, PCWP, POP, "wedge") reflects preload, with a normal range of 5-12 mm Hg
- RVEDP (CVP, RAP) also reflects preload, with a normal range of 2-5 mm Hg
- Fluid responsiveness can be assessed through echo, stroke volume variation and passive leg raise
Afterload
- Afterload is defined as the amount of resistance the left ventricle must overcome to eject its contents into the aorta
- Afterload equals End Systolic Wall Stress (or resistance)
- The diameter of the vessel affects blood flow, with constrictor and dilator influences affecting vascular tone
- Mean Arterial Pressure (MAP) can be calculated with the formula: SBP + 2(DBP) / 3
Ventricular Afterload
- Left ventricular afterload is influenced by systemic vascular resistance
- SVR is calculated using the formula: MAP – CVP x 80 / CO
- Normal SVR range is 800-1400 dynes/sec/cm5
- Right ventricular afterload is influenced by pulmonary vascular resistance
- PVR is calculated using the formula: MPAP – CAOP x 80 / CO
- The normal PVR range is 100-250 dynes/sec/cm5
Contractility
- Contractility, also known as Inotropy
- It Reflected by LVSWI (amount of "work" performed by LV with each heartbeat): normal range is 50-62 g-m/m²
- RVSWI normal range is 7.9-9.7 g-m/m²
- Ejection Fraction normal range is 50-70%
Cardiac Index
- Cardiac Index is calculated as CO/BSA
- The normal range is 2.2-4.0 L/min/m2
- Cardiac output is indexed to reflect BSA
Cardiac Output Guide
- Right-side preload is CVP, afterload is PVR and contractility is RVSWI
- Left-side preload is PAOP, afterload is SVR, and contractility is LVSWI
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Description
This lesson covers hemodynamics, including pressures generated by blood flow and its significance for heart function, fluid balance, and vessel health. It discusses pulmonary artery monitoring, cardiac output (CO) calculation, as well as the determinants of stroke volume, including preload, afterload, contractility and heart rate.
