Hemodynamic Monitoring

Hemodynamic Monitoring

Instructor Information

  • Professor: Melissa A. Coleman, MSN-Ed., RN, PCCN

Learning Objectives

  • Describe methods commonly used in critical care to determine cardiac output.
  • Describe hemodynamic monitoring and the nurse’s role in invasive cardiac monitoring.
  • Discuss indications for invasive hemodynamic monitoring.
  • Compare preload, afterload, and contractility in relation to cardiac function.
  • Describe potential complications of invasive hemodynamic monitoring.
  • State the teaching needs for patients and their families when invasive hemodynamic monitoring is indicated.
  • Formulate nursing interventions for patients undergoing hemodynamic monitoring.
  • Calculate a patient’s mean arterial pressure (MAP) and apply findings to the patient's condition.

Hemodynamics: Definition

  • Hemodynamics: Refers to the intravascular pressures and flow during heart muscle contraction. It involves:

    • Movement of blood
    • Assessment of tissue perfusion
    • Measurement of cardiac output (CO)

  • Hemodynamic Stability: Indicates that blood movement meets the body’s metabolic demands, assessed via:

    • Adequate blood pressure (BP)
    • Heart rate (HR)
    • Cardiac output (CO) measurements

Cardiac Output (CO)

  • Definition: The volume of blood the heart pumps per minute.
  • Formula: extCO=extStrokeVolume(SV)imesextHeartRate(HR)ext{CO} = ext{Stroke Volume (SV)} imes ext{Heart Rate (HR)}
  • Components:
    • Preload: Initial stretch of myocardium before contraction
    • Afterload: The resistance the ventricle must overcome to eject blood
    • Contractility: The strength of the heart’s contraction
  • Cardiac Index (CI): Assessment of CO adjusted for patient's size, formula: extCI=extCOextBodySurfaceArea(BSA)ext{CI} = \frac{ ext{CO}}{ ext{Body Surface Area (BSA)}}
    • Normal Range: 2.5 - 4.0 L/min/m²

Preload

  • Estimation Methods:

    • Right Atrial Pressure (RAP)
    • Central Venous Pressure (CVP)
    • Pulmonary Artery Occlusive Pressure (PAOP)/Pulmonary Artery Wedge Pressure (PAWP)

  • Influencing Factors:

    • Blood volume
    • Ventricular function
    • Vascular tone
    • Cardiac rhythm
    • Intrathoracic pressure

Afterload

  • Estimation Methods:

    • Pulmonary Artery Pressure (PAP)
    • Pulmonary Vascular Resistance (PVR)
    • Systemic Vascular Resistance (SVR)
    • Left Ventricular Pressure

  • Influencing Factors:

    • Vasodilation and constriction
    • Fluid volume changes

Mean Arterial Pressure (MAP)

  • Definition: The average arterial pressure during one cardiac cycle.
  • Importance: Better indicator for organ perfusion than BP alone.
  • Goal: MAP > 65 mmHg recommended.
  • Formula:
    extMAP=extsystolicBP+(2imesextdiastolicBP)3ext{MAP} = \frac{ ext{systolic BP} + (2 imes ext{diastolic BP})}{3}

Methods of Hemodynamic Monitoring

  • Non-Invasive/Indirect Methods:

    • Vital signs: Heart rate, Blood pressure
    • Arterial oxygen saturation measurement
    • Transthoracic Echocardiogram (TTE)
    • Ejection Fraction
    • Lactic Acid levels (Type 1 vs Type 2 lactic acidosis)
    • Mottling test - passive leg raise

  • Invasive/Direct Methods:

    • Arterial Line (A-Line) for blood pressure monitoring
    • Central Venous Catheter (CVC) for CVP monitoring
    • Pulmonary Artery Catheter (PAC) for multiple hemodynamic parameters
    • Cardiac Catheterization for direct measurements

Invasive Hemodynamic Measurements

  • Mixed Venous Blood O2 Saturation (SVO2, ScVO2):
    • Normal Range: 60-80%
    • Indicates oxygen utilization by the body. An increase suggests poor utilization, possibly from hypermetabolic states, anemia, or shock.
  • Intracardiac Pressures:
    • Right Atrial Pressure (RAP)
    • Central Venous Pressure (CVP)
    • Right Ventricular Pressure (RVP)
    • Pulmonary Artery Pressure (PAP)
  • Calculated Measurements:
    • Stroke Volume
    • Systemic Vascular Resistance (SVR)
    • Pulmonary Vascular Resistance (PVR)

Specific Intracardiac Pressures

  • Right Atrial Pressure (RAP)/Central Venous Pressure (CVP):

    • Normal Range: 2-6 mmHg
    • Indicator of right heart preload. An increase signals fluid overload, right heart failure, or tricuspid valve failure; a decrease suggests fluid deficit or shock states.

  • Pulmonary Artery Occlusive Pressure (PAOP)/(PAWP):

    • Normal Range: 8-12 mmHg
    • Reflects left atrial pressure. An increase indicates fluid overload or left-sided heart failure; a decrease indicates fluid deficit or shock states.

  • Pulmonary Artery Pressure (PAP):

    • Represented as systolic/diastolic (Normal Range: 15-25/8-15 mmHg).
    • Indicates afterload conditions on the right heart.

Other Measurements

  • Right Ventricular Pressure (RVP):

    • Normal Range: 15-25/2-8
    • Reflects right ventricular afterload.

  • Systemic Vascular Resistance (SVR):

    • Normal Range: 800-1200 dynes/sec/cm
    • Reflects left ventricular afterload. Can be calculated using:
      extSVR=extMAP−extCVPextCOimes80ext{SVR} = \frac{ ext{MAP} - ext{CVP}}{ ext{CO}} imes 80

  • Pulmonary Vascular Resistance (PVR):

    • Normal Range: 100-250 dynes/sec/cm
    • Reflects right ventricular afterload. Calculated as:
      extPVR=extmPAP−extPAOPextCOimes80ext{PVR} = \frac{ ext{mPAP} - ext{PAOP}}{ ext{CO}} imes 80

Hemodynamic Monitoring: Criteria

  • Goals:

    • Assess cardiovascular response to tissue oxygen demands.
    • Evaluate preload, afterload, and contractility.
    • Guide fluid and vasoactive drug administration.

  • Indications:

    • Cardiac function deficits or losses.
    • All types of shock.
    • Decreased cardiac output.

Invasive Hemodynamic Monitoring Requirements

  • Involves introduitng a catheter into a vessel or heart chamber, connected to a semi-rigid pressure tubing and transducer.
  • Flush System:
    • Maintained at 300 mmHg delivering 3-5 mL/hr through the catheter to prevent clot formation.
    • Leveling must align with the phlebostatic axis for accurate measurements.

Phlebostatic Axis Definition

  • Description: A reference point located at the midpoint between the anterior and posterior areas of the chest, aligned with the right atrium.
    • Defined by a vertical line from the fourth intercostal space at the sternum and a horizontal line extending from there to the mid-axillary line.

General Nursing Care for Invasive Hemodynamics

  • Primary Goal: Reduction of the risk of Central Line Associated Blood Stream Infection (CLABSI).
  • Procedures:
    • Dressing change should follow sterile protocol (Chlorhexidine cleansing).
    • Use transparent dressings: Change every 7 days or as needed.
    • Frequent assessment of the catheter insertion site for infection signs.
    • Patients can shower if the catheter is properly covered.

A-Line: Nursing Considerations

  • Purpose: Directly and continuously record systolic, diastolic, and MAP; allows repeated arterial blood sampling.
  • What it is: A catheter placed in a major artery, with a transducer converting the pressure into an electrical signal displayed on a monitor.
  • Considerations:
    • Perform the Allen Test to ensure collateral circulation.
    • Monitor for risks associated with line displacement (bleeding).

Complications Associated with A-Line

  • Potential Risks:
    • Infection
    • Hemorrhage
    • Hematoma
    • Thrombosis and distal ischemia
    • Embolism (proximal or distal)
    • Pseudo-aneurysm
    • Complications from medication injection:
    • Cell death, skin necrosis, gangrene, or amputation.

Central Venous Catheter (CVC)

  • Purpose: To continuously monitor Central Venous Pressure (CVP) and mixed venous oxygen saturation (ScVO2).
  • What it is: A pressure monitor threaded through a designated catheter, positioned in the superior vena cava; can also be used for medication administration (e.g., PICC, IJ).

Complications of CVC

  • Risks:
    • Infection
    • Bleeding
    • Pneumothorax
    • Hemothorax
    • Pleural effusion
    • Pericardial tamponade
    • Vascular erosion
    • Cardiac dysrhythmias due to catheter irritation
    • Embolism (air, particulate matter, catheter tips, clot).

Pulmonary Artery Catheter (PAC)

  • Description: A balloon-tipped catheter inserted into a large vein, directed to various heart locations, ultimately resting in the pulmonary artery.
  • Measurements:
    • Direct values for:
    • Right Atrial Pressure (RAP)
    • Mixed Venous Oxygen Saturation (SVO2)
    • Right Ventricular Pressure (RVP)
    • Pulmonary Artery Pressure (PAP)
    • Pulmonary Artery Occlusive Pressure (PAOP)
    • Core body temperature
  • Calculations Available:
    • Cardiac Index (CI)
    • Stroke Volume (SV)
    • Systemic and Pulmonary Vascular Resistance (SVR, PVR)
    • Core body temperature measurements.

Indications & Considerations for PAC

  • Indications:
    • Assess cardiac shock
    • Right-sided heart failure
    • Hemodynamic monitoring during cardiac surgery phases
    • Titration of vasoactive medications
  • Considerations:
    • Patient must be on bed rest to minimize PAC line disruptions.
    • Positioning of the stopcock nearest the transducer must align with the phlebostatic axis.
    • Contraindications:
    • Presence of right heart mass
    • Tricuspid or pulmonary prosthetic masses/endocarditis
    • Left bundle branch block (LBBB).

Complications Associated with PAC

  • Risks:
    • Pulmonary artery rupture
    • Pulmonary artery emboli/infarct
    • Arrhythmias.

Obtaining PAOP/PAWP with PAC

  • Guidelines:
    • Avoid wedging for more than 15 seconds.
    • Do not leave the catheter in a permanent wedge position.
    • Passive deflation of the balloon is crucial; do not pull back on the balloon to deflate.
    • Do not inflate the balloon with more than 1.5 mL of air.
    • The balloon should be deflated after four respiratory cycles during dampening/wedging.
    • Only use the 1.5 mL syringe supplied with the catheter for inflation tasks.