NOTES preload by sanmelody


									               NOTES #4 Hemodynamic Monitoring Lab 2010

    Lab #4: Hemodynamic Monitoring (refer also to Module 4: Heart Failure)
               (Lewis p. 740-742; 829; 1738-1747) * Online tutorial
                          Hemodynamic Monitoring

Information from hemodynamic monitoring (invasive and non-invasive)*

(Measurement of pressure, flow, and oxygenation within cardiovascular system) ;
invasive methods used within ICU setting;
*Indicate important values to know/understand/apply.
   1.    Heart parameters
         a.   Heart rate
         b.   Arterial blood pressure (“A” lines)
         c.   Central venous pressure *(CVP) = CVP-right ventricular pre-load
         d.   Systemic and pulmonary pressures *(PAP), *Pulmonary artery wedge
              pressure (PAWP)
         e.   *Cardiac output/CI (adjusted for body size)
         f.   O2 saturation of arterial blood (SaO2)
         g.   O2 saturation of mixed venous blood (SvO2)
         h.   *Mean arterial blood pressure (MAP) (*What is significance of MAP?
              *p. 744)

                **Mean arterial blood pressure (desirable: 70 – 90 mm
                Hg);*less than 60 danger area (may read slightly different values)>
                inadequate perfusion to vital organs
                    Formula: MAP = CO X SVR
                      *MAP < 60: severely jeopardizes perfusion to vital organs
                      MAP> 105: indicates hypertension or severe
                              vasoconstriction (**Know formula & how to calculate &
                              will see again!) Often calculated automatically on BP
                  **MAP = systolic BP+2(diastolic BP)

          i.    Stroke volume/SVR (Systemic Vascular Resistance) (What is SVR?
                *Factors effect SVR; how would an elevated SVR affect afterload?
     2.   Use indirect measurement of left ventricular pressures by flow directed,
          balloon-tipped catheter (PA catheter/Swan-Ganz catheter)
          a.    *Measurements within vessels walls converted into signals then into
                electrical wave forms graphically amplified/displayed
          b.    For critically ill, unstable patients (ie patients with acute MI,
                cardiomyopathy, right/left ventricular failure, etc.)

Terminology-hemodynamic monitoring (Key Points –Lewis online )

     1.   Cardiac output (CO)= volume of blood pumped by heart in 1 minute.
          Cardiac index (CI) = measurement of CO adjusted for body size.
          a.   CO = stroke volume (SV) X HR; usual is 4-8 L/min. (*adjusted for
               body size by calculation of cardiac index; normal 2.2-4Lmin/m2)

        b.   Urine output: indirect measurement of CO; How does body
             compensate for decreased CO (cardiac dysfunction)? (Text p. 823 &
             Frank Starling mechanism & neuroendocrine response)
        c.   Decreased CO due to poor ventricular filling, hypovolemia, poor
             emptying, decreased myocardial contractility (infarct, ischemia,
             arrhythmias); vasodilatation due to sepsis and drugs and increased
             SVR as hypertension, aortic stenosis is, etc
        d.   Increased CO due to increased O2 demand, effect of sympathetic
             nervous system (fear, anxiety)
   2.   Stroke volume (SV) - volume ejected with each heartbeat . Stroke volume
        index. (SVI) is measurement of SV adjusted for body size; normal SV=60-
        130cc/beat; factors that determine SV = preload, afterload and contractility
        *Keep concept in mind!

   3.   Systemic vascular resistance (SVR)- opposition to blood flow offered by
        the vessels –called systemic vascular resistance (SVR) or pulmonary
        vascular resistance (PVR). Systemic vascular resistance (SVR) is the
        resistance of the systemic vascular bed.
   4.   Pulmonary vascular resistance (PVR)- resistance of pulmonary vascular
        bed; both of these measures can be adjusted for body size.
   5.   Preload, afterload, and contractility determine SV (and thus CO and blood
        a.    Preload- volume within ventricle at end of diastole.
        b.    PAWP= LVEDP= PAOP- *Filling volume of ventricles at end of
              diastole; reflects amount of cardiac muscle stretch at end-diastole
              just before contraction; (pre-before=the load or volume that
              stretches the LV or RV just prior to ejection/contraction); preload
              affected by volume of blood returning to the heart,

        c.      Measured by Pulmonary Artery (PA) catheter for left ventricular pre-
                load, also called Pulmonary artery occlusion
                pressure/pulmonary artery wedge pressure or PAWP;*Preload
                of left ventricle= LVEDP (left ventricular end-diastolic pressure) =
                1)    Pre-load determined by volume blood returning to heart, venous
                      tone, actual amount of blood in venous system

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              2)    Pre-load directly related to force of myocardial contraction
              3)    Inc. preload: greater the stroke volume (SV= greater CO
              4)    Consider- what disease process/medication(s), etc. inc. preload?
                    How would that be managed? (Lewis p. 824-828, consider types
                    heart failure)
              5)    Causes dec. preload from dec. stroke volume (SV) and dec.
                    cardiac output (CO); what disease process/medication(s) would
                    decrease preload? How would that be managed?
         d.   Afterload refers to forces opposing ventricular ejection;includes
              systemic arterial pressure, resistance offered by aortic valve, and
              mass and density of blood to be moved.
              1)    *Left ventricular afterload -measured by assessment of SVR
              2)    (systemic vascular resistance); Pulmonary vascular resistance
                    PVR measures resistance against which right ventricle works
              3)    **Greater the afterload, less the cardiac output
              4)    Arterial BP: indirect measurement of afterload for LV
              5)    *What decreases afterload-arterial vasodilation as in sepsis,
                    hyperthermia, use of nitrates; what increases afterload:
                    vasoconstriction. hypovolemia, hypothermia, aortic stenosis,
                    hypertension; medications as catecholamines/inotropic drugs like
                    norepinephrine/epinephrine and intropin), pulmonary
                    hypertension (right sided failure)
         e.   Contractility describes strength of contraction. Agents that inc. or
              improve contractility =positive inotrope as sympathetic stimulation
              ie drugs (dig, dopamine, dobutamine, epinephrine, calcium).
              Contractility diminished by negative inotropes, as certain drugs
              (e.g., lidocaine, calcium channel blockers, β-adrenergic blockers) and
              conditions (e.g., acidosis) as acute MI, cardiomyopathy; hypoxemia;
              electrolyte imbalance (K, Ca, Mg); drugs as lidocaine, calcium channel
              blockers, beta blockers); **Starling’s Law= greater the stretch of
              muscle fibers = greater the force of contraction and volume of blood
    6.   CVP- measured in right atrium or in vena cava close to heart = right
         ventricular preload or right ventricular end-diastolic pressure under normal

Principles of Invasive Pressure Monitoring

    1.   To accurately measure pressure, equipment must be referenced and “zero”
         balanced to environment and dynamic response characteristics optimized.
    2.   “Referencing”- positioning transducer so that zero reference point is at level
         of atria of heart or *phlebostatic axis.

   3.   Zeroing confirms that when pressure within system = zero, monitor reads
        zero; “zeroing” recommended during initial setup, immediately after
        insertion of arterial line, when transducer has been disconnected from
        pressure cable or pressure cable has been disconnected from monitor, and
        when accuracy of measurements is questioned.
   4.   Optimizing dynamic response characteristics involves checking that
        equipment reproduces, without distortion, a signal that changes rapidly.
        Dynamic response test (square wave test)- performed every 8 to 12 hr
        and when system opened to air or accuracy of measurements are

Types/uses of Invasive Pressure Monitoring

   1.   Continuous arterial pressure monitoring- (“Art line”) use for patients
        experiencing acute hypertension and hypotension, respiratory failure, shock,
        neurologic injury, coronary interventional procedures, continuous infusion of
        vasoactive drugs, and frequent ABG sampling. Highly accurate.

        Arterial line (note set-up and connection to pressurized bag)
        UTube video –shows insertion arterial line and Allen test (6 minutes)
        a.    High- and low-pressure alarms set based on patient’s current status.
              Measurements obtained at end expiration to limit effect of
              respiratory cycle on arterial pressure.
        b.    Arterial lines- risk of hemorrhage, infection, thrombus formation,
              neurovascular impairment, and loss of limb.
        c.    To help maintain line patency and limit thrombus formation, use
              continuous flush irrigation system at 3 to 6 ml of heparinized saline
              per hour. (or without heparin)
        d.    Neurovascular status distal to arterial insertion site-assessed hourly.
              Neurovascular impairment -result in loss of a limb-an emergency.
        e.     *Allen test prior to insertion to determine adequacy of ulnar artery
              circulation –read page 1740)

   2.   Pulmonary artery (PA) pressure monitoring- guide acute-phase
        management of patients with complicated cardiac, pulmonary, and
        in intravascular volume problems. Normal PA (pulmonary artery

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    pressure- PAP) pressure: **20-30 mmHg systolic and 8-12 diastolic
    usual is 25/10; mean is 15 mm Hg; increased systolic in pulmonary
    HTN, increased diastolic from ventricular failure; decreased PAP
    with hypovolemia, shock (*Know this)
    a.   PA diastolic (PAD) pressure and PAWP-sensitive indicators of cardiac
         function and fluid volume status-routinely monitored.
    b.   Monitoring PA pressures-allows precise therapeutic manipulation of
         Preload- allows CO to be maintained without placing patient at risk for
         pulmonary edema.
    c.   PA flow-directed catheter (e.g., Swan-Ganz)- measure PA pressures,
         including PAWP

         1)    Distal lumen port (catheter tip) placed within PA, used to monitor
               PA pressures and sample mixed venous blood specimens (e.g., to
               evaluate oxygen saturation).
         2)    Additional lumens-exit ports in right atrium or right atrium and
               right ventricle (if two).
         3)    Right atrium port- used for measurement of CVP, injection of
               fluid for CO determination, and withdrawal of blood specimens.
         4)    If a second proximal port available-used for infusion of fluids and
               drugs or blood sampling.
         5)    Thermistor (temperature sensor) lumen port located near distal
               tip-for monitoring blood or core temperature; used in
               thermodilution method of measuring CO.
    d.   PA measurements-obtained at end of expiration.
    e.   PAWP measurement-obtained by slowly inflating balloon with air
         (balloon capacity) until PA waveform changes to a PAWP waveform;
         balloon- not inflated for more than four respiratory cycles or 8 to
         15 seconds- *inflation of balloon blocks pressure from behind
         (wedging)- allows measurement of pressure generated by left
         ventricle= Pulmonary Artery Wedge Pressure (PAWP)

                1)   Assesses left ventricular function
                2)   Normal PAWP: 6–12 mm Hg (*slightly different values various
                     sources; average value)-**Reflects preload of the LV or
                     LVEDP; equal to PA diastolic if no pulmonary problems
                3)   Inc. PAWP due to left ventricular failure, mitral valve problems,
                     hypervolemia and pericardial tamponade (*Understand this)
                4)   Decreased PAWP due to low stroke volume, hypovolemia, shock

   3.   CVP-measurement of right ventricular preload; can measure with PA
        catheter using one of proximal lumens or with a central venous catheter
        placed in internal jugular or subclavian vein.
        a.   Measure of blood volume and venous return
        b.   *Right heart filling pressures; monitors fluid volume status-catheter
             inserted into internal jugular or subclavian vein; distal end positioned
             in superior vena cava just above right atrium
        c.   Reading approximates right ventricular end diastolic pressure or right
             ventricular function and general fluid status (pre-load)
        d.   Measured in cm of water with manometer (normal: 2 – 8 cm) or mm
             Hg if connected to transducer (normal: 2 – 6 mm HG)
        e. Dec. CVP due to hypovolemia, consider all causes; inc. CVP due to
             hypervolemia, inc. venous return, right sided heart failure, pulmonary
             hypertension, tricuspid stenosis and regurgitation; vasoconstriction,
             cardiac tamponade
   4.   PA catheter-commonly used to measure CO via the intermittent bolus
        thermodilution CO method or the continuous CO method.
   5.   SVR, SVR index, SV, and SV index can be calculated each time that CO is
        measured; increased *SVR- indicates vasoconstriction from shock,
        hypertension, inc. release or administration of epinephrine and other
        vasoactive inotropes, or left ventricular failure; dec. SVR- vasodilation, may
        occur during shock states (e.g., septic, neurogenic) or with drugs that
        reduce afterload; changes in SV *important indicators of pumping status of
        heart than other parameters.
   6.   Venous Oxygen Saturation
        a.   CVP and PA catheters- can include sensors to measure oxygen
             saturation of hemoglobin in venous blood termed mixed venous
             oxygen saturation (ScvO2, SvO2).
        b.   SvO2/ScvO2 reflects dynamic balance between oxygenation of arterial
             blood, tissue perfusion, and tissue oxygen consumption (VO2).
             1)    Normal SvO2/ScvO2 at rest is 60% to 80%; sustained decreases
                   in SvO2/ScvO2 may indicate dec. arterial oxygenation, low CO,
                   low hemoglobin level, or inc. oxygen consumption or extraction

6  RNSG 2432
              2)   If SvO2/ScvO2 falls below 60%, nurse determines which of these
                   factors has changed
              3)   Sustained inc. in SvO2/ScvO2 may indicate a clinical
                   improvement (e.g., increased arterial oxygen saturation, dec.
                   metabolic rate) or problems (e.g., sepsis).

Complications with PA Catheters

    1.   Infection and sepsis-serious problems associated with PA catheters
         a.    Careful surgical asepsis for insertion and maintenance of catheter and
               attached tubing is mandatory
         b.    Flush bag, pressure tubing, transducer, and stopcock-changed every
               96 hours.
    2.   Air embolus-risk associated with PA catheters
    3.   Pulmonary infarction or PA rupture due to (1) balloon rupture, releasing
         air and fragments that could embolize; (2) prolonged balloon inflation
         obstructing blood flow; (3) catheter advancing into a wedge position,
         obstructing blood flow; and (4) thrombus formation and embolization.
         a.    Balloon -must never be inflated beyond balloon’s capacity (usually 1 to
               1.5 ml of air); must not be left inflated for more than four breaths
               (except during insertion) or 8 to 15 seconds.
         b.    Pressure waveforms-monitored continuously for evidence of catheter
               occlusion, dislocation, or spontaneous wedging.
         c.    PA catheter- continuously flushed with slow infusion of heparinized
               saline solution (or no heparin).
    4.   Ventricular dysrhythmias- can occur during PA catheter insertion or
         removal or if tip migrates back from PA to right ventricle and irritates
         ventricular wall
    5.   Nurse may observe that PA catheter cannot be wedged and may need to be
         repositioned by the physician or a qualified nurse.

Nursing Management: Hemodynamic Monitoring

    1.   Need baseline data regarding patient’s general appearance, level of
         consciousness, skin color and temperature, vital signs, peripheral pulses,
         and urine output are obtained.
         a.    Baseline data- correlated with data obtained from biotechnology (e.g.,
               ECG; arterial, CVP, PA, PAWP pressures; SvO2/ScvO2).
         b.    Single hemodynamic values are rarely significant; the nurse monitors
               trends in these values and evaluates the whole clinical picture with the
               goals of recognizing early clues and intervening before problems
    2.   * Patient monitored continuously during passage of PA catheter,
         characteristic changes in ECG waveform determine location of catheter;
         balloon inflated during passage (floats through), then wedges in pulmonary
         capillary, reading taken, then deflated..; *Potential for dysrhythmia as
         catheter is advanced
    3.   General factors effecting hemodynamic findings:
         a.    Heart function
         b.    Intravascular volume (amount of blood in vasculature)
         c.    Intropy (strength of myocardial contractions)
         d.    Vasoactivity (expanding and contracting of blood vessels to
               accommodate variations in blood flow, regulate arterial pressure, etc)

          e.      Chronotropy (timing and rate of heart contraction)

    4.    Values Summary- (Text p. 1739; other sources may vary slightly)

                              Parameter                        Normal value
               Mean Arterial Pressure (MAP)                  70 -105 mm Hg
               Cardiac Index (CI)                            2.2-4 L/min/m2
               Cardiac Output (CO)                           4-8 L/min
               Central Venous Pressure (CVP) (also           2-8 mmHg
               known as Right Atrial Pressure (RA))
                                                             Systolic 20-30
                                                             mmHg (PAS)
                                                             Diastolic 4-12
               Pulmonary Artery Pressure (PA)
                                                             mmHg (PAD)
                                                             Mean 15-25
               Pulmonary Capillary Wedge Pressure
                                                             6-12 mmHg

    5.   Drugs that effect Afterload /Preload *Very good to know! *Heart Failure
Drug Therapy                    Examples                      Nursing Responsibilities
Afterload Reduction             ACE inhibitors                Monitor for hypotension

*** first line drugs                 Captorpril (Capoten)           Monitor for cough and
                                     Enalapril (Vasotec)
                                                                    Monitor BUN and creatinine
                                     Lisinipril (Zestril)
                                                                    Monitor for bradycardia &
                                     Apresoline                     hypotension

                                     Minipress                      Watch with COPD & asthma

                                     Nipride for end stage

                                     Newest (beta blocker)-

                                     Carvedilol (Coreg)
Cardiac Glycosides                   Digitalis                      Apical pulse; Rate & rhythm;
                                                                    Anorexia, nausea & vomiting;
                                                                    Visual changes; Digoxin level;
                                                                    Potassium level 3.5-5meq/L

Other Inotropes                      ATPase inhibitors              IV infusion

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Drug Therapy                    Examples                        Nursing Responsibilities
Used for refractory end stage   Dopamine (Intropin)             Monitoring
heart failure
                                Dobutamine (Dobutrex)           Caution due to increased O2
                                Phosphodiesterase inhibitors=
                                increased cell calcium

                                Amrinone (Inocor)

                                Milrinone (Primacor)
Preload Reduction =             Thiazides                       Daily weights

Circulating volume reduction    Chlorothiazide (Diuril)         I&O

                                Metolazone (Zaroxoylin)         Monitor electrolytes – especially

                                Furosimide (Lasix)

                                Bumetanide (Bumex)

                                K sparing

                                Spirolactone (Aldactone)

                                Triamterene (Diazide)

Noninvasive Arterial Oxygenation Monitoring
   Pulse oximetry is a noninvasive and continuous method of determining
     arterial oxygenation (SpO2), and monitoring SpO2 may reduce the frequency
     of ABG sampling.

       SpO2 is normally 95% to 100%.

       Accurate SpO2 measurements may be difficult to obtain on patients who are
        hypothermic, receiving intravenous vasopressor therapy, or experiencing

       Alternate locations for placement of the pulse oximetry probe may need to be
        considered (e.g., forehead, earlobe).

Nursing Management: Hemodynamic Monitoring

       Baseline data regarding the patient’s general appearance, level of
        consciousness, skin color and temperature, vital signs, peripheral pulses, and
        urine output are obtained.

       Baseline data are correlated with data obtained from biotechnology (e.g.,
        ECG; arterial, CVP, PA, PAWP pressures; SvO2/ScvO2).

      Single hemodynamic values are rarely significant; the nurse monitors trends
       in these values and evaluates the whole clinical picture with the goals of
       recognizing early clues and intervening before problems escalate.

 *ICU setting- Three main types of hypotension (“shock states”) observed in ICU *Keep
these in mind when studying “Shock states!!

   1. “Pump”- Cardiogenic shock

   2. “Volume”- Hypovolemia

   3. Squeeze” - Sepsis

   Pump” problems? “Cardiogenic” shock- cardiac output will be low, because the pump isn’t
   pumping. Blood pressure drops. The body says to itself: “What to do? Got to keep the blood
   pressure up somehow!”, and starts to tighten up the arterial bed. What number tells how tight
   the arterial system is? – SVR. In cardiogenic shock, cardiac output goes down, the SVR
   goes up – the pattern is usually clear- “Ooh, look! The output is only 2.2, and the SVR is
   2400!” What does the wedge pressure do? (Remember, the LV is pumping poorly, and
   can’t empty itself…)

   “Volume” problems? “Hypovolemic” shock? Lost a lot of blood? Running too many
   marathons? Cardiac output will probably be low, since there isn’t enough volume to
   pump with. CVP and wedge pressures? Low, right? – Not enough volume. SVR? Same as
   cardiogenic: the arteries clamp down, trying to maintain pressure.

   Hypovolemic shock: cardiac output low, central pressures low, SVR high.

   Squeeze” problem? Any idea what makes this happen? Sepsis”? All that bacteremic
   endotoxin makes the arteries dilate – blood pressure drops. What to do? Now the body uses
   the mirror reflex of what it did in the cardiogenic setting: instead of clamping down the
   arteries, which it can’t do, because that’s where the problem is – now the heart picks
   up the slack, pumping both faster and harder: heart rate goes up, and cardiac output
   does too. * Septic shock: cardiac output high, central pressures low, SVR low.

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