Hemodynamicsupdated 4/25/2012

Hemodynamics is the study of the forces that influence the circulation of blood.

Meaning literally "blood movement" is the study of blood flow or the circulation.

How bad is your day?Is everything working the way it is supposed to?

Goal:

The goal of hemodynamic monitoring is to maintain adequate tissue perfusion. Classical hemodynamic monitoring is based on the invasive measurement of systemic, pulmonary arterial and venous pressures, and of cardiac output.

- Monitors do not always “tell the truth.”

-Therapeutic decision-making based on numbers alone is never appropriate and can be dangerous, even deadly.

Trace a drop of blood through the heart

Ventricular Preload

Ventricular preload refers to the degree that the myocardial fiber is stretched prior to contraction (end-diastole).

Within limits, the more the myocardial fiber is stretched during diastole (preload), the more strongly it will contract during systole, and therefore the greater the myocardial contractility will be.

Ventricular Afterload

Ventricular afterload is defined as the force against which the ventricles must work to pump blood.

Determined by:1) The volume and viscosity of the blood ejected2) The peripheral vascular resistance3) The total cross-sectional area of the vascular space into which blood is

ejected.

Arterial systolic blood pressure best reflects the ventricular afterload.

Blood Volume

Although total blood volume varies with age, body size and sex, the normal adult volume is 5 Liters.

75% is in the systemic circulation15% in the heart10% in the pulmonary circulation

Overall, about 60% of the total blood volume is in the veins and about 10% in the arteries.

The capillary bed normally contains about 75ml of blood but has the capacity to hold 200ml.

Hypovolemia due to bleeding out, shock (shunt), dehydrationHypervolemia due to fluid overload (IV therapy, renal disease, CHF)

Stoke Volume

Stroke Volume is the volume of blood ejected by the ventricles (particularly the left ventricle) during each contraction or systole.

The preload, afterload, and myocardial contractility are the major determinates of stroke volume. {normal SV is 60-130 ml/beat}

Note: The heart does not eject all the blood it contains during systole.

ESV = a small volume that remains in the heart called the end-systolic volume, remains behind in the ventricles

EDV = during the resting phase, or diastole, the ventricles fill back up to a volume called the end-diastolic volume

EDV-ESV = Stroke Volume

Normal stoke volume of 70ml, we can compute an ejection fraction (EF)

SV / EDV = EF or 70 / 110 = 0.64 or 64%

Cardiac Output

Stoke Volume is determined by:1) Ventricular preload2) Ventricular afterload3) Myocardial contractility

Cardiac Output directly influences blood pressure

CO is measured via a special PA catheter using the thermodilution method

CO is the volume of blood pumped in 1 minute

SV x HR = CO {normal CO is 4-8 L/min}

If SV is 70ml and HR is 72 bpm, the CO is 5,040 ml/min

If HR is 100 bpm and CO is 8L (8000ml):800ml ÷ 100bpm = 80ml SV

BSA is needed to calculateboth the Stroke Volume Index (SVI)and the Cardiac Index (CI)

BSA can be calculated by the following formula, or by the Dubois Body Surface Chart as shown:

BSA = 1+ weight in Kg + (height in cm – 160) ÷ 100

Stoke Volume Index and Cardiac Index

Stroke Volume Index (SVI)

Assuming the heart rate remains the same, as the stroke volume index increases or decreases, the cardiac index also increases or decreases.

The stroke volume index reflects:contractility of the heartoverall blood volume statusamount of venous return

SV / BSA = SVIExample: 60 ml/beat ÷ 2 m2 = SVI of 30 ml/beat/m2

Cardiac Index (CI)

If CO is being determined, the CI should also be calculated for additional information on heart function. Calculated as CO / BSA = CI

Example: 5 L/min ÷ 2 m2 = 2.5 L/min/m2

Normal, resting Cardiac Index is 2.5–4 L/min/m2 of BSA

Play YouTube VideoHemodynamic Video Lecture:

Graphic Display (duration = 4 minutes) :http://www.youtube.com/watch?v=G9C-4i3RNs8&feature=related

Pulmonary Vascular Resistance (PVR)

The PVR measurement reflects the afterload of the right ventricle.

(PA – PCWP) / CO x 80 = PVR(normal PVR = 80-240 dynes/sec/cm-5, or 1-3 mmHg/L/min)

Increased PVR – Chemical: Decrease alveolar oxygenation (alveolar hypoxia) Decreased pH (acidemia) Increased PCO2 (hypercapnia)

Increased PVR – Pharmacologic Agents: Epinephrine (Adrenalin®) Norepinephrine (Levophed®, Levarterenol®) Dobutamine (Dobutrex®) Dopamine (Intropin®) Phynelephrine (Neo-Synephrine®)

PVR cont.

Increased PVR – Hyperinflation of Lungs: Mechanical ventilation CPAP, PEEP, ↑Vt

Increased PVR – Pathology: Vessel blockage or obstruction Caused by a thrombus or an embolus (blood clot, fat cell, air bubble, or tumor mass)

Vessel wall disease Sclerosis, Endarteritis, Polyarteritis, Scleroderma

Vessel destruction or obliteration Emphysema or Pulmonary interstitial fibrosis

Vessel compression Pneumothorax, Hemothorax, or Tumor mass

PVR cont.

Decreased PVR – Pharmacologic Agent: Oxygen Isoproterenol (Isuprel®) Aminophylline Calcium-blocking agent

Decreased PVR – Humoral Substances: Acetylcholine Bradykinin Prostaglandin E Prostacyclin (prostaglandin I2)

Systemic Vascular Resistance (SVR)(aka Peripheral Vascular Resistance)

The SVR measurement reflects the afterload of the left ventricle.

Circulatory Resistance is derived by dividing the mean blood pressure by the cardiac output: BP ÷ CO = Resistance(normal SVR = 900-1,400 dynes/sec/cm-5, or 15-20mm Hg/L/min)

Generally, if vascular resistance increases, BP increases.Blood pressure can be used to reflect pulmonary or systemic resistance.

Increased SVR – Vasoconstricting Agents: Epinephrine (Adrenalin®) Norepinephrine (Levophed®, Levarterenol®) Dopamine (Intropin®) Phynelephrine (Neo-Synephrine®)

Increased SVR – Abnormal Conditions: Hypovolemia Septic shock (late stages) ↓PCO2

SVR cont.

Decreased SVR – Vasodilating Agents: Nitroglycerin Nitroprusside (Nipride®) Morphine Amrinone (Inocor®) Hydralazine (Apresoline®) Methyldopa (Aldomet®) Diazoxide (Hyperstat®)

Decreased SVR – Abnormal Conditions: Septic shock (early stages) ↑PCO2

Nitric Oxide Therapy (NO)

Because it relaxes capillary smooth muscle, inhalation of NO improves blood flow to ventilated alveoli.

This reduces intrapulmonary shunting, improves arterial oxygenation, and lowers pulmonary vascular resistance and pulmonary artery pressures.

Knowledge of the effect of NO therapy on patient outcomes awaits further study.

{AARC Clinical Practice Guidelines}

NO in the Cath-Lab

Although NO is used often in the Cath-Lab; research on its effect is limited.

"Cardiac catheterization in congenital heart disease patients is frequently more time consuming because of small vessel size, the multiple measurements that must be made, the instability of the patients (particularly neonates and infants), the frequency of multiple sites of arterial-venous admixture, and performance of other required interventions (e.g., Rashkind procedure). For example, evaluation of pulmonary artery hypertension may require administration of oxygen, nitric oxide, or other agents and repeated measurement of pulmonary blood flow pressures and cardiac output."

http://www.aapc.com/memberarea/forums/archive/index.php?t-1214.html

Monitoring Devices

Non-Invasive:SpO2

BP cuffTEE (Transesophageal Echocardiography)

Invasive:ABGRadial Arterial Line CatheterCVPSvO2

Swan-Ganz

SpO2 Monitoring

SpO2 Quiz

Blood Pressure Monitoring

Blood Pressure

Systemic arterial BP is the force exerted against the walls of the arteries when blood is pumped through them.

In other words:Blood pressure (BP) is a function of the Cardiac Output (CO) times the Systemic Vascular Resistance (SVR)

CO x SVR = BP

Normal CO = 4-8 L/min

Normal SVR = 15-20 mmHg/L/min

Normal BP with proper size cuff and use of a sphygmomanometer = 120/80 mmHg{Systolic normal range = 100-140mmHg; Diastolic normal range = 60-90mmHg}

Infants and children <10 years of age Systolic 60-100 mmHg

Diastolic 20-70 mmHg

Mean BP

Calculate the Mean BP

Systolic – Diastolic = Pulse Pressure (PP)PP x 1/3 = _____ + diastolic = Mean{Mean arterial pressure = 70-105mmHg}

If BP is 130/90, then: If BP is 90/40, then:130 – 90 = 40 (PP) 90 – 40 = 5040 x .33 = 13.2 50 x .33 = 16.513.2 + 90 = 103 16.5 + 40 = 57

Why calculate the Mean Blood Pressure?Most physician’s drug orders are given to nursing based on it.“if mean is less than (#), then give x_dose”

All else being constant, the mean arterial pressure is directly related to the volume of blood in the vascular system, and inversely related to its capacity

Volume ÷ Capacity = MAP (Mean Arterial Pressure)

Transesophageal Echocardiography (TEE)

An echocardiogram (echo) uses high-frequency sound waves to produce a graphic outline of the heart’s movement.

A Transesophageal echo (TEE) test is a type of echo test in which the ultrasound transducer, positioned on an endoscope, is guided down the patient’s throat into the esophagus (the "food pipe" leading from the mouth into the stomach). An endoscope is a long, thin, flexible instrument that is about ½ inch in diameter.

The TEE test provides a close look at the heart’s valves and chambers, without interference from the ribs or lungs. TEE is often used when the results from standard echo tests are not sufficient, or when your doctor wants a closer look at your heart.

TEE may be combined with Doppler ultrasound and color Doppler to evaluate blood flow across the heart’s valves.

Transesophageal Echocardiography

Arterial Blood Gas (ABG)

Radial Arterial Line Catheter aka: A-line, Art-line, RAL

Insertion recommended for the following situations;

1. The patient needs continuous monitoring of blood pressure[a hypotensive pt is receiving medication such as Levophed, vasopressin, dopamine]

2. Frequent arterial blood samples needed for blood gas analysis

Note: a newborn will have the line placed into the umbilical artery

Radial Arterial Line Catheter

Play YouTube VideoSetting Up a Pressure Transducer :

A-line catheter setup (duration = 5 minutes) :http://www.youtube.com/watch?v=58TQjvHd_sQ&feature=related(all the parts for setup + flushing the line)

A-line & CVP setup (duration = 10 minutes) :http://www.youtube.com/watch?v=uv6t1raryjM&feature=related(demonstrates “burping the bag”)

Video – placing the Art-line (duration = 2 minutes) :http://www.youtube.com/watch?v=Vt7ONGDeP3w&feature=relmfu(placing the catheter & drawing blood)

RAL continued

Central Venous Pressure (CVP)

via a Central Line Catheter

The tip of the central-line catheter resides in the superior vena cava just above the right atrium

This CVP is a measurement of the pressure in the Right Atrium

Two factors that influence the Right Atrial pressure:1) Blood volume returning to it2) Function of the Right Ventricle

CVP line inserted to:1. Monitor the patient’s right-sided (right atrium) heart pressure2. To rapidly administer a large volume of IV fluids3. To administer cardiac medications during a CPR attempt

CVP cont.

↓ CVP usually indicates that the patient is hypovolemic

↑ CVP may suggest:1. Fluid overload check for elevated BP, crackles in bases of lungs2. Tricuspid valve or pulmonic valve insufficiency or stenosis3. Right ventricular failure if a COPD pt with pulmonary HTN has RV failure, the condition is: cor pulmonale4. Cardiac tamponade5. Atrial or Ventricular septal defect with left-to-right intracardiac shunt6. Pulmonary embolism

CVP

SvO2

Mixed venous oxygen saturation (SvO2) is measured from a mixed venous blood sample. Small changes in PvO2 (pressure of mixed venous oxygen) lead to large changes in SvO2, and therefore large changes in CvO2.

As a result, the SvO2 measurement is a sensitive index of cardiac output (CO) and tissue perfusion if VO2 is stable.

Continuous SvO2 monitoring has been suggested as an alternative to intermittent, serial CO measurements. Based on the Fick equation (see separate slide), if total body oxygen consumption, hemoglobin, and SaO2 remain constant, a change in CO should be reflected by a parallel change in SvO2.

Low PvO2, SvO2 and ScvO2 (CVP measurement with fiber-optic technology) values are often seen in patients with heart failure because the slow flow of blood through the tissues results in more oxygen being extracted.

SvO2 Monitoring

CCO/SvO2 catheter

=

SvO2 may be continuously monitoredthrough a fiber-optic reflectance oximetrysystem incorporated in a five-lumenpulmonary artery catheter.

A new pulmonary artery balloon flow-directed catheter combines a fiber optic photometric system for continuous display of mixed venous blood oxygen saturation (SO2) with the capacity for hemodynamic measurements including thermodilution cardiac output estimation.

SvO2 Monitoring

Photometric detection system having multiple path length flow

http://www.patsnap.com/patents/view/US7236248.html

The thermodilution technique has become the de facto clinical standard for measuring cardiac output because of its ease of implementation and the long clinical experience using it in various settings. It is a variant of the indicator dilution method, in which a known amount of a substance is injected into the blood stream and its concentration change measured over time at a downstream site. As its name implies, the thermodilution method uses a thermal indicator, whereas other indicator dilution methods use various substances, such as indocyanine green dye.

http://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/v03/030286r00.HTM

Fick Equation

VO2 max

… (aka: maximal oxygen consumption, maximal oxygen uptake, peak oxygen uptake or aerobic capacity) …

is the maximum capacity of an individual's body to transport and use oxygen during incremental exercise, which reflects the physical fitness of the individual.

The name is derived from V = volume per time, O2 = oxygen, max = maximum.

Q x (CaO2 – CvO2) = VO2 max

Q is the cardiac output of the heartCaO2 is the arterial oxygen content

CvO2 is the venous oxygen content

Swan-Ganz Catheter

Used to measure hemodynamic and central pressure variables such as pulmonary capillary wedge pressure

Measure several hemodynamic parameters directly

The development of the pulmonary artery catheter by Swan and Ganz in the late 1960s began a new era in assessment of left ventricular and pulmonary performance.

Unlike the CVP that is placed in the right jugular vein, the Swan Ganz is usually placed into the subclavian.

Swan-Ganz Catheter• The Swan-Ganz catheter is a balloon-tipped catheter made of

polyvinyl chloride that is used to measure CVP, PAP and PCWP.• The catheter also allows for the aspiration of blood from the

pulmonary artery for mixed venous blood gas sampling and injection of fluids to determine cardiac output.

• The distal channel (lumen) is used for the measurement of PAP and for obtaining mixed venous blood from the pulmonary artery.

• The proximal channel (lumen) is used for the measurement of CVP or right atrial pressure and for the injection of fluids to determine cardiac output.

• The balloon inflation channel controls the inflation and deflation of a small balloon, located about 1cm from the distal tip of the catheter, and is used to measure PCWP.

• The fourth channel is an extra port for the continuous infusion of fluid, when necessary.

• This catheter is also equipped with a computer connector to measure cardiac output with the use of the thermodilution technique.

ValuesHEMODYNAMIC VALUE ABBREVIATION NORMAL RANGE

Directly Measured from the Swan-Ganz:Central Venous Pressure CVP <8 mmHg [<6 depending on textbook]

Right Atrial Pressure RAP 2–8 mmHg [2-6 depending on textbook]

Right Ventricle RVP 0–5 mmHg [systolic = 20-30mmHg]

Mean Pulmonary Artery Pressure PA 9–20 mmHg [systolic = 20-30mmHg

Pulmonary Capillary Wedge Pressure diastolic = 6-15mmHg]

(aka: Pulmonary Artery Wedge)(aka: Pulmonary Artery Occlusion) PCWP 4–12 mmHgCardiac Output CO 4–8 L/min

Calculated from the direct measurements listed above:Stroke Volume SV 60–130 mlStroke Volume Index SVI 30–50 ml/beat/m2Cardiac Index CI 2.5–4.2 L/min/m2Right Ventricular Stroke Work Index RVSWI 7–12 g m/m2Left Ventricular Stroke Work Index LVSWI 40–60 g m/m2Pulmonary Vascular Resistance PVR 20–120 dynes/sec/cm¯5

or, 1.5–3.0 mmHg/L/minSystemic Vascular Resistance SVR 800–1500 dynes/sec/cm¯5

or, 15–20 mmHg/L/min

Catheter placement (duration 50 sec) :http://www.youtube.com/watch?v=sygNe0McMK4&feature=related

Play YouTube VideoPulmonary Artery Catheterization :

Swan-Ganz Monitoring

The pacer leads are connected directly to the pacemaker. If cardiac pacing is not required, the lumen can be used for infusions and blood sampling.

Play YouTube VideoSwan Ganz Catheter Placement :

Physician’s Lecture (duration = 6 minutes) :http://www.youtube.com/watch?v=OYabV1H6p78(heart model demonstration)

Physician’s Lecture (duration = 9 minutes) :http://www.youtube.com/watch?v=PjRRPhMj0os&feature=related(monitoring pressures)

Put It All Together

A burn victim is being monitored in the ICU.Pertinent data are below:

PvO2 45 torrPCWP 4 mm HgMean PAP 11 mm HgCVP 4 cm H2OUrine Output 5 mL/hr

As the respiratory therapist, you should recommend:

A. An increase in intravascular volume

B. The initiation of diuretic therapy

C. Assist/Control ventilation

D. An increase in FIO2

A burn victim is being monitored in the ICU.Pertinent data are below:

PvO2 45 torrPCWP 4 mm HgMean PAP 11 mm HgCVP 4 cm H2OUrine Output 5 mL/hr

As the respiratory therapist, you should recommend:

A. An increase in intravascular volume

Are you Hemodynamically stable today?Or is everything out of the norm?

Open Book Test

May use:> EGAN’s Fundamentals of Respiratory Care> Clinical Assessment in Respiratory Care> Basic Clinical Lab Competencies – Gary White

> Comprehensive Exam Review – J.R. Sills