Exam 3 Flashcards
Factors that increase CVP
Hypervolemia (volume overload/perfusionist overfilling) Forced Exhalation Tension pneumo Heart failure Pleural effusion Decreased cardiac output cardiac tampenade Mechanical ventilation and the application of PEEP
Factors the decrease CVP
Hypovolemia (perfusionist underfilling)
Hypovolemia
Deep inhalation
shock
Six Factors Affecting Venous Return
- Musculovenous pump
- Decreased venous capacitance
- Respiratory pump
- Vena Cava Compression
- Gravity
- Pumping Action of the Heart
Musculovenous pump
Contraction of limb muscles during normal locomotion (walking, running, swimming) promotes venous return by the muscle pump mechanism (n/a on CPB)
Decreased venous capacitance
Sympathetic activation of veins decrease venous compliance, increase venous tone, increase CVP and venous return which increases blood flow through the circulatory system
Respiratory pump
during inspiration, the intrathoracic pressure is negative and abdominal pressure is positive
Vena Cava Compression
an increase in the resistance of the vena cava, when the thoracic vena cava becomes compressed decreases venous return
Gravity
the effects of gravity on venous return seem paradoxical, when a preson stands up hydrostatic forces cause the RAP to decrease and the venous pressure in the limbs to increase. This increases the pressure gradient for venous return from the dependent limbs to the right atrium; however, venous return decreases
Why do the effects of gravity cause venous return to DECREASE?
CO and arterial pressure decrease when standing (because RA pressure falls)
Flow decreases; arterial P falls more than RAP. Pressure gradient driving flow through the entire circulatory system is decreased.
(Orthostatic hypotension)
Pumping action of the heart
Atrial pressure changes alter CVP during cardiac cycle. CVP is altered because there is no valve between the heart’s atria nad veins. Atrial pressure changes venous pressure and therefore alters venous return
No valve; can assume pressures are equal
Subclavian vein & internal jugular vein insertion catheter length
20 cm
Femoral venous access catheter length
60cm
CVP Insertion Sites
Subclavian internal jugular external jugular femoral antecubital
Seldinger Technique
Catheter over guidewire
Do peds use swan ganz catheters?
No, they don’t make them small enough
Central Line Complications
Cardiac Tampenade Wire or catheter embolism Vascular injuries (non PA) -Hemothorax -Hydrothorax -Carotid artery injury -subclavian a. aneurysm Pulmonary artery rupture Pneumothorax Air Embolism Fluid extravasation
A Wave
Increased Atrial Pressure during right atrial contraction. Correlates with P wave on EKG
C Wave
Slight elevation of the tricuspid valve into the right atrium during early ventricular contraction. Correlates with QRS
Due to isovolumic RV contraction; closes tricuspid valve and causes it to bow back into RA
“tricuspid valve close and ventricular contraction”
X Wave
Downward movement of ventricle during systolic contraction. Before T wave on EKG.
Midsystolic Event
“Systolic collapse in atrial pressure”
V Wave
Pressure produced when blood filling the right atrium comes up against a closed tricuspid valve. Occurs as the T wave is ending on an EKG
Last atrial pressure increase caused by filling of the atrium with blood from the vena cava; late systole with tricuspid still closed
“venous filling of the atrium”
Y Wave
Tricuspid valve opening the diastole with blood flowing into the RV. Occurs before P wave on EKG
“Diastolic collapse in atrial pressure”
Decrease in atrial pressure as tricuspid open and blood flows from atrial to ventricle
What determines change in CVP?
CVP = V/ Compliance
What part of CVP waveform coincides with point of maximal filling of the right ventricle?
Peak of “a” wave
What part of CVP waveform should be used for measurement of RVEDP?
Peak of “a” wave
Should be measure at end-expiration; machines just “average” the measurement
Systolic Events of CVP waveform (ventricular events)
cxv
Diastolic events of CVP waveform (ventricular events)
ay
Tachycardia and CVP
Short PR interval can cause “a” and “c” waves to fuse
Reduces time spent in diastole causing short “y” descent
“V” and “A” may appear to merge
Bradycardia and CVP
Each wave becomes more distinct
“H” wave may become evident- plateau wave in mid or late diastole
“H” wave has little clinical significance
A Fib and CVP
“A” wave disappears (no atrial contraction)
“C” wave more prominent (atrial volume is higher at the beginning of systole because the atrium did not empty)
PVCs and CVP
Large a wave
a wave at expected time (not premature)
Tricuspid Regurgitation and CVP
RA gains volume during systole so “c” and “v” wave is much higher
RA sees RV pressure curve becomes “ventricularized”
Tricuspid Stenosis and CVP
Problem with atrial emptying and a barrier to ventricular filling on the right side of the heart
Mean CVP elevated
“a” wave usually prominent as it tries to overcome the barrier to emptying
“Y” descent muted as a result of decreased outflow from atrium to ventricle
Pericardial Constriction and CVP
Limited venous return to heart, elevated CVP, end diastolic pressure, equalization in all cardiac chambers
Prominent “a” and “v” waves; steep “x” and “y” descnets
Characteristic M or W pattern, dip and plateau (square root sign)
Cardiac Tampenade and CVP
Changes in atrial and ventricular volumes are coupled so total cardiac volume doesnt change
CVP monophasic with single, prominent “x” descent and a muted “y” descent
Similar to pericardial constriction but not exactly the same
CVP and Respiration
Increases during Expiration
Decreases during inspiration
What is CVP when on bypass?
0
If not zero, you’re not emptying; get better venous return!!
As you restrict your venous line, what is the relationship between arterial flow and venous return?
Arterial Flow > Venous Return
This will fill your heart. CVP rises (preloads RV); Pa Volume rises (preload LV) arterial P rises
Therefore, perfusionists control preload!!
Who invented the Swan Ganz catheter and in what year?
Dr. Jeremy Swan & Dr. William Ganz
Cedars-Sinai Medical Center
Invented in 1970
Fabricated by Edwards Laboratories
Indications for PAP Monitoring
- Management of cardiopulmonary pressures and flows
- Assess CV Function
- Perioperative monitoring in surgical pts
- Shock
- Assess pulmonary status
- Assess fluid requirements
- Assess obstetric pts
- Therapeutic & diagnostic indications
Indications for Swan-Ganz PA Catheter
Assessment of respiratory distress
Assessment of Shock
Assessment of Therapy
Assessment of fluid requirement in critically ill patients
Assessment postoperative in heart surgery pts
Assessment of valvular disease
Assess cardiac tamponade/constriction
What is the #1 use for a swan?
assess fluid requirement in critically ill patients
What types of things are we looking at when assessing therapy?
Afterload reduction
Vasopressors
Beta Blockers
Intra-aortic balloon counter-pulsation
What do we look at when we assess fluid requirement in critically ill patients?
Hemorrhage
Sepsis
ARF aka Acute kidney injury
Burns
What can a Swan-Ganz Catheter do and measure?
Preload Afterload SVR PVR Cardiac Output (thermal dilution) Cardiac Index Venous Sat (Oximetric Swan) Pacemaker (paceport swan)
Preload
Reflected by end-diastolic pressures of ventricles, as generate by volume of blood into ventricles just before next contraction
What measures RV preload?
CVP measures right filling pressures
What measures LV preload?
PAWP measures left ventricular filling pressures
Afterload
pressure the ventricles must pump against to eject blood; resistance to ventricular systole
What are the determinants of CO?
Preload Afterload Contractility Heart Rate Heart Rhythm
Where is the thermistor located?
About 3cm behind the tip
Two ways to measure CO (thermal dilution)
10ccs of cold saline under 10C or room temp injected through RA. Drop in blood temp recorded as cooler fluid passes the tip of the thermistor
Incorporation of heating coil on catheter 30cm from tip, residing in atrium area, eliminates the cold fluid bolus
Cardiac Index
Measurement considered more accurate than CO, individualized to heigh and weight of pt
What type of swan used for venous saturation?
Oximetric Swan
Venous Saturation Measurement
Catheter with fiber-optic based probe extended and lodged into ventricle wall provide instant readings of SvO2 or oxygen saturation of ventricle tissues. Finite life as sensor becomes coated with protein and it can irritate ventricle via the contact area
What type of swan used for pacemaker?
Paceport Swan
PAOP
Pulmonary artery occlusion pressure (PAWP)
PADP
pulmonary artery diastolic pressure
What does PCWP tell us?
Indirect measure of LAP (become of large compliance of pulmonary circulation)
Cause of acute pulmonary edema (PCWP >20mmHg)
Diagnosis severity of LV failure and mitral stenosis
Diagnosis of ARDS
What is PCWP the gold standard for determining?
Cause of acute pulmonary edema
What PCWP indicates acute pulmonary edema?
> 20mmHg
What is ejection fraction related to?
LVEDP
Potential Problems Getting Accurate Hemodynamic Data
Body position relative to transducer Conncetion of transducer to wrong catheter port Cardiac dysfunction Catheter Whip Ventilatory Effects
Catheter Whip
Hyperdynamic Heart
Excessive catheter length
What are some problems with cardiac dysfunction that create problems getting accurate data?
Mitral Regurgitation (PCWP elevated due to elevated v wave) LV dysfunction- (PCWP elevated due to amplified a wave) Tachycardia (not enough time for PCWP and LVEDP to equilibrate)
Complications of Pulmonary Artery Catheterization
Cardiac arrhythmias Bundle Branch Block Balloon Rupture Catheter Knotting Infection Thrombus formation Pneumothorax Pulmonary Ischemia or infarction Damage to or rupture of PA segment Cardiac perforation & tamponade
Why Wide range of results in benefits of swan?
- Knowledge of basic principles varies
- Hemodynamic end-points of tx varies
- Distance of catheter tip from LV varies
- Delay in decision to use a PA catheter
- Patients very ill, one piece of puzzle only
Surgical Cutdown Insertion Technique
Direct needle-puncture of vessel or tiny incision
Percutaneous Insertion Technique
More common
Introducer to access the vessel
Guide wire; wire removed; catheter introduced through insertion sheath
What affects stroke volume?
Preload
Afterload
Contractility
What variables affect cardiac output?
Metabolic rate and oxygen demand
Gender
Age
Body Size
What is the most potent determinant of CO?
Metabolic rate and oxygen demand
Critially ill/injured patients usually need a CO that is _____% higher than normal.
50%
Co normally is ______% less in a female than a male with equivalent BSA.
10 %
Neonatal Demand Range
150-200 cc/kg
Normal BSA Range
1.8 l/m/m^2 to 2/4 l/m/m^2
Normal CPB Flow- Kg
50-75 cc/kg/min
____% to _____% of people have PFO’s
20-30%
Anatomic Shunt
Volume and circulatory flow changes that create differences in saturation, pressure, and flow in the chambers
L to R Shunting
Overloads R ventricle, PBF>SBF. Seen in ASD, VSD, PFO, and acyanotic congenital abnormalities.
R to L Shunting
PBF < SBF, TOF and cyanotic congenital defects (skips the heart)
Invasive Ways of Measuring CO
Fick oxygen consumption method
Indicator- dilution method
Thermodilution method
Fick Principle: Minute volume may be calculated if…
- Tracer substance amt entering or leaving an organ are unknown
- Tracer concentration entering and leaving an organ are known (ex. the lungs)
Fick Principle Equation
CO= Oxygen Consumption (cc/min)/ A-VO2 Content difference (cc/dL blood)
Fick Method Simultaneously Measures….
Arterial oxygen content
Mixed venous oxygen content
Oxygen uptake by lungs
How to measure oxygen uptake by lungs?
- Assume 3.5 ml/kg/min (avg adult)
- Analyze o2 content different of inspired minus expired air collected over 3 minute period
- use breath-by-breath metabolic monitor
Fick Technique Advantages
Low CO
Better than thermodilution for regurgitant tricuspid or pulmonary valves
Fick Technique Disadvantages
Steady hemodynamic & metabolic state- 3 min Requires multiple people Time consuming Requires meticulous technique Not easily repeatable/ not continuout Results not readily available for immediate clinical intervention Not valid in presence of shunts Not accurate for high cardiac outputs
What does indicator dye measure?
Flow! (Not velocity)
Indicated Dye Characteristics
Mixes well with blood Easy to determine concentration Stable Not retained by the body Not toxic
Indicator Dye Examples
Radio-iodated serum albumin
Indocyanine dye (cardiogreen)
O2
Temperature (iced or room temp saline or 5% dextrose)
Dye Dilution Principle
PA Injection of dye
Continuous sample drawn in systemic artery
Plot concentrations graphically
Does an open system have recirculation?
No recirculation
Does a closed system have recirculation?
Yes, has recirculation
What is QP/QS normally?
1
What is QP relate to in QP/QS
Right heart
What is QS relate to in QP/QS
Left heart
If QP/QS is greater than one, which side output is greater?
RV output greater than LV output
If QP/QS is less than one, which side output is greater?
LV output greater than RV output
Dye dilution Advantages
Most accurate with high-cardiac output
Overall accuracy plus/minus 5%
Dye Dilution Disadvantages
Not valid with shunts, regurg, shock Dye unstable/photosensitive Risk of allergic rxn to dye Calibration using sample of pts blood Careful metered blood withdrawal Not repeatable or have continuout measurement Patient must be stable metabolic state for 40 sec Time consuming Not accurate with low output
Thermodilution Modified Equation
CO = (60)(1.08)(C)(V) (T-Ti)/ int Tb*dt
Thermodilution Technique
Patient supine (less than 20 degrees) Injectate volume (10, 5, or 3 ml) Injectate temp (room or iced) Set stopcocks, computers 4 second injection or less Repeat 3x, 90 seconds apart should have 3 values within 10% of each other
What type of cardiac output does thermodilution work with
High cardiac output
Patient generated errors with thermodilution method?
Low CO
Arrythmias
Flow abnormalities (regurg)
Technique generated errors with thermodilution method?
Wrong injectate, temp, volume Injection too slow THrombus or plasma protein on catheter Thermister defect INcorrect computation factor entered
Thermodilution Method Advantages?
No blood withdrawal
Easy and quickly performed
Continuous info can be available (venous pulmonary artery catheter)
Results readily available
What method has continuous information available?
Thermodilution via venous pulmonary artery catheter
Thermodilution method disadvantages
Not accurate in presence of tricuspid regurg and shunts
Least accurate if CO is low
Non-Invasive Ways of Measuring CO
Doppler Ultrasonography & Echo
Thoracic electrical bioimpedence
Electromagnetic Flow Probes
What is are the normal frequencies in dianostic ultrasound?
2 and 18 MHz
Two approaches to ultrasonic BF
Transit time
Doppler Principle
Doppler Ultrasonography is used to assess…
Insufficient valves
LV function
EF
Systole: Thoracic blood volume _________ and impedence _________
increases; decreases
Diastole: Thoracic blood volume _______ and impedence _________
decreases; increases
TEB Routinely Displayed Parameters
HR BP MAP Thoracic fluid content CO/ CI Acceleration index Velocity index Systolic Time ratio SVR/SVI LV ejection time
Acceleration Index
how fast the ventricular volume change occurs
Velocity index
maximum speed of blood flow
TEB Advantages
Continuous Real-time data Noninvasive Rapid computer processing no extensive training required cost effective not affected by mitral or pulmonic regurg
TEB Disadvantages
Accuracy affected by LBBB, L to R intra cardiac shunts, aortic regurg, sepsis
Uncontrolled muscle movement and patients inability to cooperate creates artifact
Principle of magnetic induction
move electrical conductor through magnetic field get induced voltage proportional to velocity of motion
What does electromagnetic flow probe measure?
Mean velocity of flow
Calculates flow
