Hemodynamic Monitoring Concepts

Hemodynamic Monitoring Concepts

• Cardiac Output (CO)

  • Formula: CO = HR × SV
  • Definition: Volume of blood pumped by the heart per minute
  • Normal range: 4 – 8 L/min

• Ejection Fraction (EF)

  • Definition: Percentage of blood ejected from the ventricle with each beat

• Preload

  • Definition: Stretch of the cardiac muscle at the end of diastole, highest when ventricular volume is greatest
  • Factors Affecting Preload:
    • Amount of blood returning to the ventricle (venous return)
    • Ventricular compliance/extensibility
  • Measurement: Central venous pressure (CVP)
    • Normal range: 2 – 6 mmHg
    • Used to estimate fluid volume

• Starling's Law

  • Increased stretch leads to stronger contraction

Effects of Preload

• Increased preload:

  • Increased stroke volume
  • Increased cardiac output
  • Increased myocardial oxygen demand

• Decreased preload:

  • Dehydration
  • Blood loss
  • Sepsis

Afterload

• Definition: Pressure/resistance ventricle must overcome to eject blood
• Factors Affecting Afterload:
  • Systemic and pulmonary arterial pressures
  • Systemic vascular resistance (SVR)
  • Resistance from aortic and pulmonic valves
  • Blood viscosity

Summary of Hemodynamics

• Preload: Volume
• Afterload: Resistance

Purpose of Hemodynamics

• Measure pressure, volume, and oxygenation of blood in the cardiovascular system

Types of Invasive Lines

• Arterial Line
  • Used for continuous blood pressure monitoring and blood draws
• Central Venous Catheter (CVC)
  • Measures right atrial pressure (CVP)
  • Normal CVP: 2 – 6 mmHg
• Pulmonary Artery Catheter (Swan-Ganz)
  • Measures left atrial pressure (PAWP)
  • Normal PAWP: 6 – 12 mmHg

Monitoring and Calibration

• Transducer: Converts physiological events into electrical signals
• Zeroing: Necessary to ensure accurate readings, done every 8 hours or with position changes
• Phlebostatic Axis: Level of the right atrium—at the 4th intercostal space at the midaxillary line

Arterial Line Monitoring

• Mean Arterial Pressure (MAP)
  • Formula: MAP = (SBP + (DBP x 2)) / 3
  • Normal range: 70 – 105 mmHg
  • Minimum MAP of 60 mmHg needed for organ perfusion

Complications and Interventions

• Complications: Limb impairment, infection, thrombosis/arterial occlusion
• Interventions: Monitoring perfusion, applying pressure if line dislodged
• Central Venous Pressure (CVP): Monitor fluid status, guide therapy
• Nursing Interventions: Maintaining dressing changes, confirming initial placement with chest X-ray, monitoring CVP trends
• Pulmonary Artery Catheter: Reflects left atrium and left ventricular preload, placement confirmed with chest X-ray
  • Low PAWP: Indicates conditions like MI, heart failure
  • High PAWP: Indicates conditions like sepsis, hyperthyroidism

This quiz explores key concepts of hemodynamic monitoring, including cardiac output, ejection fraction, and preload. Understand how these parameters affect heart function and overall cardiovascular health. Test your knowledge on the effects of preload and related physiological laws.