HEMODYNAMIC MONITORING: The Fundamentals

Goal: Provide the participant with the basic knowledge required to care for a patient with an arterial line, central venous pressure/right atrial pressure line, and/or a pulmonary artery catheter.

Objectives: Define hemodynamic monitoring. State indications for hemodynamic monitoring. Identify the correct reference point for leveling & zeroing the hemodynamic monitoring system. Identify components of normal arterial, right atrial, pulmonary artery, & pulmonary artery wedge waveforms. Identify factors that can affect the accuracy of the waveforms. Describe common complications associated with hemodynamic monitoring. Discuss the nursing care for patients with hemodynamic monitoring.

Hemodynamic Monitoring: The use of a device or instrument to provide physiological measurements in order to more closely and accurately monitor a patient’s condition. Usually involves the use of an invasive catheter inserted into a body cavity or organ system.

Hemodynamic Monitoring - Examples: Intra-arterial pressure Central venous pressure Intra-cardiac pressures: Right atrial pressure Pulmonary artery pressure Pulmonary artery wedge pressure

Indications: Intra-arterial: Intra-cardiac: Continuous blood pressure monitoring Blood sampling Frequent arterial or venous sampling Ability to quickly assess the effects of medical interventions Medications or fluid Intra-cardiac: Continuous monitoring of both right & left heart fluid status Cardiac output Mixed venous blood sampling Ability to quickly assess the effects of medical management Medications or fluid

Common Components: Monitoring device: Transducer cable Transducer Amplifier Oscilloscope Transducer cable Transducer Transducer holder Flush system: Pressure bag Fluid: Heparin vs. NS Pressure tubing Catheter Carpenter’s level

Common System Components:

Accurate & Reliable Waveforms/Values: Technical factors: Patient positioning: Supine Head of bed: 0-45° Leveling: Eliminates effects of hydrostatic forces on the observed hemodynamic pressures Ensure air-fluid interface of the transducer is leveled before zeroing and/or obtaining pressure readings Phlebostatic axis: Level of left atrium 4th ICS & MAL (technically ½ AP diameter) Mark the chest with washable felt pen

Phlebostatic Axis:

Leveling:

Accurate & Reliable Waveforms/Values: Technical factors: Zeroing: Negates the force exerted by the atmosphere (760 mmHg at sea level) Pressure transducers can be affected by changes in temperature “Drift” will occur from the zero baseline over time

Accurate & Reliable Waveforms/Values: Technical factors: Pressure tubing & transducer system System free of air Length of tubing; correct tubing System connectors tight; stopcocks Luer-locked Adequate fluid in flush system Flush solution pressurized to 300 mmHg Dynamic response testing Square wave, fast flush or snap test

Dynamic Response Test: Figure A – Expected square wave test Figure B – Overdamped Figure C – Underdamped

Accurate & Reliable Waveforms/Values: Overdamped: Sluggish, artificially rounded & blunted appearance SBP erroneously low; DBP erroneously high Causes: large air bubbles in system, too compliant of tubing, loose/open connections Overdamped? Shock states, vasodilation, aortic stenosis, thrombus on catheter tip, catheter kinked or against vessel wall

Overdamped Waveform:

Accurate & Reliable Waveforms/Values: Underdamped or ringing: Overresponsive, exaggerated, artificially spiked waveform SBP erroneously high; DBP erroneously low Causes: small air bubbles, too long of tubing, defective transducer Underdamped? Vasoconstriction, hypertension, atherosclerosis, aortic regurgitation, hyperdynamic states (fever)

Underdamped Waveform:

Intra-arterial Pressure Monitoring

Blood Pressure Monitoring: Non-invasive blood pressure: Dependent on blood flow Invasive, intra-arterial monitoring: Dependent on pressure changes Typically more accurate than NIBP Allows for convenient arterial blood sampling

Arterial Line Insertion Sites: Radial: Most common site Good collateral circulation Accessibility & ease of maintenance Modified Allen’s test Brachial Femoral Dorsalis Pedis

Arterial Waveform: Peak systolic pressure: Generated by left ventricular contraction Peak systole correlates with QRS on ECG rhythm strip Normal: 100-140 mmHg

Arterial Waveform:

Arterial Waveform: Dicrotic notch: Diastole: Closure of the aortic valve Marks the end of ventricular systole & the beginning of diastole Diastole: Lowest pressure in arterial system Measured just before systolic upstroke Normal: 60-80 mmHg

Arterial Waveform:

Arterial Waveform: Catheter location: The more distal the catheter is placed, in relation to the aorta, the higher the systolic pressure & the lower the diastolic pressure

Complications: Infection: Hematoma Hemorrhage Thrombosis/embolization Localized Systemic Hematoma Hemorrhage Thrombosis/embolization Ischemia Nerve damage

Nursing Care: Assess arterial line flush system: Adequate, appropriate fluid Pressurized to 300 mmHg No air bubbles Connections tight Infection control Level & zero q shift & PRN Continuously observe arterial waveform quality; over/underdampened Correlation to NIBP Site care Assess circulation distal to insertion site

Central Venous Pressure & Right Atrial Pressure

Central Venous Pressure & Right Atrial Pressure: Indications: Assessment of intra-vascular volume status: Preload: the volume or pressure generated at end-diastole Assess right ventricular function: Follow trends Secure access; often only IV access available

Central Venous Pressure & Right Atrial Pressure: Measured through a catheter tip placed within the right atrium (RAP) or just outside RA in the vena cava (CVP): Single-lumen, double-lumen, triple-lumen catheters Pulmonary artery catheter Access Sites: Subclavian Internal jugular vein Femoral vein

CVP/RAP Pressures: Normal values: Increased CVP/RAP: 2–6 mmHg Hypervolemia Hyperdynamic states (increased cardiac output) Cardiac tamponade Constrictive pericarditis Pulmonary hypertension Heart failure Pulmonary embolus Positive pressure ventilation

CVP/RAP Pressures: Normal values: Decreased CVP/RAP: 2–6 mmHg Hypovolemia: Dehydration Hemorrhage Decreased mean systolic pressure Vasodilation (specifically, venodilation): Sepsis Vasodilators

CVP/RAP Waveform: Waveform Components: “a” wave: Atrial contraction (atrial kick) Within the PR interval “x” descent: atrial diastole “c” wave: Rise in pressure w/ tricuspid valve closure Near the end of the QRS “v” wave: Passive atrial filling during ventricular systole Following the T wave, within the T-P interval “y” descent: passive atrial emptying

CVP/RAP Waveform:

Abnormal Waveforms: Large “a” waves: Loss of “a” waves: Loss of A-V synchrony (Cannon Waves) Tricuspid valve stenosis Loss of “a” waves: Dysrhythmias resulting in loss of P wave Giant “v” waves: Tricuspid insufficiency Right ventricular failure

Complications: Pneumothorax Infection: Bleeding/hemorrhage Localized, endocarditis, systemic Bleeding/hemorrhage Dysrhythmias: Premature ventricular contractions Ventricular fibrillation Heart block Thrombus/embolus Perforation of cardiac chamber

Nursing Care: Assess CVP/RAP line flush system: Adequate, appropriate fluid Pressurized to 300 mmHg No air bubbles Connections tight Infection control Level & zero q shift & PRN Continuously observe CVP/RAP waveform quality; over/underdampened Correlation to clinical picture Site care Assess for complications

Pulmonary Artery Pressure & Pulmonary Artery Wedge Pressure

Indications: Assess left & right heart function: Preload: Right heart: RAP Left heart: pulmonary artery diastolic & pulmonary artery wedge pressures Cardiac output: thermodilution Afterload: Right heart: Pulmonary vascular resistance (PVR) Left heart: Systemic vascular resistance (SVR) Contractility: Stroke work index (SWI) Assess response to therapeutic interventions Atrial and ventricular pacing Mixed venous blood gas Continuous venous oxygen saturation

Clinical Indications: Complicated MI End-stage heart failure Acute pulmonary edema Pulmonary embolus Acute respiratory distress syndrome Shock Acute renal failure Complex fluid management Cardiac surgery High-risk surgical patients

PA Pressure Monitoring: Pulmonary artery catheter: Standard is a #7-French, multi-lumen, radiopaque catheter Marked in 10-cm increments Multiple ports & openings 1.5-cc balloon at distal end

Pulmonary Artery Catheter:

Anatomy of a PA Catheter: Components: Thermistor Balloon inflation port w/ gate valve Proximal injectate port Typically has three infusion ports: RA infusion port & lumen opening RV infusion port & lumen opening PA distal infusion port & lumen opening Balloon

Insertion & Placement:

Insertion: Access: Method: Right internal jugular Left Subclavian vein Femoral Method: Patient positioning Percutaneous Vessel dilator & introducer sheath

RA

RV

PA

PAWP

Insertion:

RA RV PA PAWP

PA Pressures: Pulmonary artery systolic (PAS): Normal PAS: 15–30 mmHg Pulmonary artery diastolic (PAD): Normal PAD: 5–16 mmHg Pulmonary arterial wedge pressure: Normal PAWP: 5–12 mmHg All pressures measured at end-expiration

PA Pressures: Increased PA pressures: Decreased PA pressures: Pulmonary hypertension Pulmonary disease Mitral valve disease Left ventricular failure Pulmonary embolus Decreased PA pressures: Hypovolemia Pulmonary artery vasodilation (meds, SIRS, sepsis)

PA Waveform:

PA Waveform Components: 1. PA systolic peak 2. Dicrotic notch: Closure of PA valve 3. PA diastole 4. Anacrotic notch: Opening of PA valve

Pulmonary Artery Wedge Pressure: Also: PCWP or PAOP Normal PAWP: 5–12 mmHg Indirect measurement of mean left atrial pressure (LAP) which is an indirect measure of left ventricular end-diastolic pressure (LVEDP) or left ventricular preload Normally, PAWP is 1–3 mmHg lower than PAD Physiologically impossible for PAWP to be higher than the PAD

PA

PAWP

PAWP:

PAWP Balloon Inflation:

PAWP Waveform Components: “a” wave: Atrial contraction (atrial kick) “x” descent: Atrial diastole “c” wave: Closure of mitral valve “v” wave: Atrial filling “y” descent: Passive atrial emptying

PAWP Waveform Components:

Obtaining PAWP: Continuous, close observation of the ECG and the PAP waveform during procedure Inflate balloon: Open gate valve after syringe attached Slowly & gently inflate with only enough air to “wedge” the balloon (typically 1.25-1.5 cc) Wedge for no more than 10-15 seconds or 2-3 respirations If strong resistance is met – do not inflate If no resistance is met or blood in lumen - STOP Measure PAWP at end-expiration “a” wave method – most accurate

Obtaining PCWP:

Respiratory Variation: PAP waveform in a spontaneously breathing patient

Respiratory Variation: PAWP waveform in a mechanically ventilated patient

Monitoring Problems: Air bubbles in system Blood in system Thrombus at tip of catheter Spontaneous wedging & overwedging Loss of pressure tracing Pressures that do not match the clinical picture

Overwedging:

Complications: Infection Dysrhythmias Pneumothorax Hematoma & hemorrhage Valve rupture Pulmonary artery rupture Pulmonary infarct Pulmonary embolus

Nursing Care: Goals of therapy Prevention of infection Patient positioning Assuring accuracy of data Continuous waveform monitoring Activity

Cardiac Output: Cardiac output: Amount of blood pumped by the heart per minute CO = SV x HR Four physiologic factors affect CO: Preload Afterload Contractility Heart rate

Cardiac Output: Preload: Afterload: Load (volume) that stretches the ventricles prior to contraction: Right heart – CVP/RA Left heart – PAD or PAWP Afterload: Impedance to the ejection of blood from ventricles: Depends on: volume & mass of blood ejected; and compliance & size of vascular space into which blood is being ejected Right heart – PVR Left heart - SVR

Cardiac Output: Contractility: Heart rate Ability of myocardial tissues to shorten and develop tension; “squeeze”: Cannot directly measure clinically Indirectly: LVSWI or RVSWI Heart rate Stroke volume: average volume of blood ejected per cardiac contraction

Cardiac Output: Thermodilution: Equipment: Computer module/monitor w/ software PA catheter w/ thermistor & injection set-up 5-10 cc fluid bolus (injectate) Room temperature vs. iced injectate Inject smoothly & quickly w/ end-expiration Calibration factors: computation constant Patient positioning

Cardiac Output: Normal values: Cardiac Output: 4–6 L/min Cardiac Index: 2.5–4 L/min

References: Boggs, R. L., & Woolridge-King, M. (Eds.). (1993). AACN procedure manual for critical care (3rd ed.). Philadelphia; Saunders. Clochesy, J. M., Breu, C., Cardin, S., Whittaker, A. A., & Rudy, E. B. (1996). Critical care nursing (2nd ed.). Philadelphia; Saunders. Marino, P. L. (1998). The ICU book (2nd ed.). Baltimore; Williams & Wilkins.