Hemodynamic Concepts

Question 1

Hemodynamic Equation

Answer 1

• Cardiac Output = Heart Rate x Stroke Volume
• CO = HR x SV
• SV: Made up of Preload, Contractility, and Afterload

Question 2

Stroke Volume

Answer 2

• SV determined by preload, afterload, and contractility
• Normal SV = 50 to 100 mL per beat
• Preload
  
  • CVP (right ventricular)
  • PAOP (left ventricular)
• Contractility
• Afterload
  
  • PVR (right ventricular)
  • SVR (left ventricular)
• As stroke volume increases, CO increases
• SV is how many mL per beat the left ventricle ejects

Question 3

Cardiac Output

Answer 3

• Normal CO is 4 L to 8 L per minute
• If CO is critically low, blood pressure will decrease

Question 4

Cardiac Index

Answer 4

• Cardiac index (CI)
• Takes into account the body surface area (BSA)
• More meaningful value than CO
• Normal CI = 2.5 to 4.0 L/min/m²

Question 5

Heart Rate (HR)

Answer 5

• As HR increases, CO increases
• Extreme bradycardia results in low CO and hypotension
• Increase in HR first sign of compensation for a low CO (occurs before BP drops)
• Extreme tachycardia also decrease CO
  
  • Loss of diastolic filling time occurs
  • Ventricles do not have time to fill, ventricular preload drops, and ventricles cannout put out what is not delivered

Question 6

Preload

Answer 6

• Volume/pressure in the ventricle at the end of diastole after the AV valves close, just prior to ejection
• Right atrial (RA) pressure or central venous pressure (CVP) reflects the right ventricular preload
• PAOP reflects the left ventricular preload
• As preload increases, SV and CO increase up to a point
• Too high of preload may lead to heart failure
• Preload will seldom be elevated if the heart is without disease and there are no metabolic abnormalities

Question 7

Afterload

Answer 7

• Pressure (resistance) against which the ventricle must pump to open the valve (pulmonic or aortic)
• Clinically measured by the pulmonary vascular resistance (PVR) for the right ventricle or systemic vascular resistance (SVR) for the left ventricle
• As afterload increases, SV and Co decrease

Question 8

Contractility

Answer 8

• The contractile force of the myofibrils independent of preload and afterload
• As contractility increases, SV and Co increase

Question 9

Normal Hemodynamic and Oxygen Parameters

Answer 9

Question 10

Hemodynamic Profiles for Select Abnormal Conditions

Answer 10

Question 11

Hemodynamic Effects of Various Cardiovascular Agents

Answer 11

Question 12

Therapies for Alterations in Hemodynamics

Answer 12

Question 13

Hemodynamic Oxygenation Parameters

Answer 13

Question 14

SvO₂ Changes

Answer 14

Question 15

Acute Mitral Valve Insufficiency

Answer 15

Question 16

Intravenous Fluids

Answer 16