Invasive Hemodynamic Monitoring Overview

Sep 10, 2024

Hemodynamics: Invasive Monitoring Lecture Notes

Introduction

  • Invasive monitoring is common in the ICU for understanding patient hemodynamics.
  • It provides insights into how hemodynamics respond to treatment and how blood flow is affected.
  • Important to compare monitor data with patient condition.

Central Venous Pressure (CVP)

  • Represents right atrial pressure; indicates venous return or preload, specifically of the right heart.
  • Measured using a central line.
  • Normal Values: 2-10 mmHg.
  • Increased CVP Causes:
    • Fluid overload
    • Cardiac tamponade
    • Right heart dysfunction
  • Decreased CVP Causes:
    • Dehydration
    • Volume loss
    • Venodilation

Arterial Line (A-line)

  • Catheter placed in an artery (radial, femoral, etc.).
  • Provides real-time systolic and diastolic pressures and mean arterial pressure.
  • Waveform Analysis:
    • Verify for underdamping (high systolic, low diastolic) or overdamping (flattened waveform).
    • A-line provides a more accurate blood pressure than a manual cuff.

Flow Track System

  • Proprietary system by Edwards Life Sciences for detailed hemodynamic monitoring using an A-line.
  • Provides stroke volume, cardiac output, and stroke volume variance (SVV).

Stroke Volume & Cardiac Output

  • Uses pulse pressure to determine stroke volume.
  • Calculates cardiac output (heart rate x stroke volume).

Stroke Volume Variance (SVV)

  • Indicates preload status; normal value is <13.
  • High SVV suggests low preload (high and dry).
  • Limitations:
    • Inaccurate with spontaneous breaths, open chest, irregular heart rate.
    • Passive leg raise can be used to test responsiveness.

Pulmonary Artery Catheter (SWAN or PA Cath)

  • Long catheter inserted through the vena cava into the pulmonary artery.
  • Provides right atrial pressure, pulmonary artery pressure, pulmonary capillary wedge pressure, and cardiac output/index.

Pulmonary Artery Pressure

  • Normal values: 20-30/10-20 mmHg.
  • Increased pressure can indicate atrial defects, pulmonary hypertension, left ventricular failure, or valve issues.

Pulmonary Capillary Wedge Pressure

  • Indirect measure of left heart preload, normal range: 8-12 mmHg.
  • Elevated Causes: Fluid overload, valve issues, heart dysfunction.
  • Decreased Causes: Hypovolemia, vasodilation.

Cardiac Output & Index

  • Measured continuously or intermittently.
  • Some setups provide venous oxygen saturation (beyond this lesson).

Systemic and Pulmonary Vascular Resistance (SVR & PVR)

  • SVR: 800-1200; low indicates dilated vessels (low BP), high indicates increased resistance (potential high BP).

Conclusion

  • Discussion on different forms of invasive monitoring is concluded.
  • Next lesson will focus on optimizing treatment to manipulate patient hemodynamics.