M&M: CV Monitoring Flashcards
During systole LV
ejects blood into vasculature, resulting in BP
As pulse moves through the arterial tree what happens to the wave?
Wave reflection distorts the pressure waveform
Systolic BP is the
peak pressure generation during systolic contraction
Diastolic BP is the
Trough pressure generation during diastolic relaxation
what is pulse pressure?
the difference between the systolic pressure and the diastolic pressure.
What is the MAP
Average arterial pressure during a pulse cycle.
Any anesthetic delivery is an absolute indication for
Arterial BP measurement.
Frequncy of BP measurement should be
every 3-5 minutes.
Contraindications to BP measurement with cuff
Vascular abnormalities or IV lines (shunts and stuff)
Why is arterial blood pressure used as a measure of organ blood flow?
Because intruments that monitor specific organ perfusion and oxygenation are complex, expensive and often unreliable.
Cuff bladder should extend at least
halfway around the extremity
Cuff width should be
20-50% greater than the diameter of the extremity
Palpation method to measure SBP
occluding flow at a palpable peripheral pulse with a BP cuff. The pressure is release 2-3 mmHg per heartbeat, until the pulse is again palpable
What is the doppler effect?
shift in sound wave frequency when a source moves relative to an observer.
When should the doppler probe be placed?
Positioned directly above an artery so that the beam passes through the vessel wall.
What is the only thing that can be reliably detected by the doppler technique
Only systolic pressure.
Maximal oscillation with Oscilllometry occurs at
MAP after which oscillations decrease
Automated BP monitors derive
SBP, MAP and DBP which is the pressure at which oscillation amplitudes change.
Arterial tonometry
pressure transducers are applied to the skin overlying an artery. Beat to beat BP is sensed by the pressure required to partially flatten the artery.
Invasive arterial BP monitoring indications
Induced hypotension
Anticipitated wide BP swings
End-organ disease necessitating precise beat to beat BP
Contraindication of Invasive arterial BP monitoring
inadequate collateral blood flow or suspicion of vascular insufficiency (Raynaud phenomenon)
Radial artery inadequate collateral flow occurs in______ % of patients
5%
Why does some people of inadequate collateral flow ?
incomplete palmar arches
How can you access ulnar collateral circulation?
Allen’s test, doppler probe, Plethysmography or pulse ox.
Brachial artery and distortion: Advantage
Large and easily ID , LESS waveform distortion because it’s proximity to the aorta.
Brachial artery disadvantage:
Kinking of the catheter during the flexion of the elbow.
Femoral artery disadvantage:
Prone to pseudoaneurysm and atheroma formation.
INCREASE RISK OF INFECTION>
The most distorted waveforms arteries
Dorsalis pedis and posterior tibial arteries.
Axillary artery more at risk for
Brachial plexus damage
Flushing the left axillary arteyr can easily result in
Transmission of air or thrombi to the cerebral circulation.
2 things that Provide optimal exposure of the radial artery
Supinate
Wrist extension
How is the radial artery course determined by
lightly palpating over the maximal impulse of the radial pulse with the fingertips
Explain the procedure of inserting an aline
Skin is prepped
0.5ml of lidocaine is infiltrated directly above the radial artery
20-22 ga cath over a needle is passed through the skin at 45 degree angle directed toward the point of palpation
Blood flashback, guidewire may be advanced through the catheter into the artery
the needle is lowered to 30 degree and advanced 1-2 mm to ensure the catheter tip is in the vessel.
Needle is withdrawn while firm pressure is applied over the artery proximal to the catheter tip to minimize blood loss as the tubing is being connected.
Complications of arterial blood pressure monitoring:
Hematoma
Vasospasm
Bleeding
arterial thrombosis
Factors associated with increases rate of complications:
Prolonged cannulation, hyperlipidemia, repeated insertion attempts, female gender, extracorporeal circulation, use of vasopressors.
Complications of A line can be minimized by
heparinized saline continuous at a rate of 2-3 ml/hr
What is the gold standard of BP monitoring
Beat to beat monitoring via arterial cannulation
The transduced waveform depends on the
Dynamic characteristics of the catheter-tubing transducer system.
Can lead to OVERDAMPING
Tubing, stopcocks and air
Overdamping lead to
underestimated systolic pressure.
Underdamping lead to
overshoot and a falsely high
What can improve system compliance
low compliance tubing
Minimizing tubing and stopcocks
Remove air bubbles.
How does transducers work?
Convert mechanical energy of the arterial pressure to an electrical singal and their accuracy depends on the correct calibration and zeroing procedures.
Motion and electrocautery on waveform
misleading arterial waveform
Rate of upstroke of the aline indicates
Contractility
Rate of downstroke of the aline indicates
Peripheral vascular resistance
Exaggerated variations in size for aline during the respiratory cycle suggest
Hypovolemia
How is MAP calculated with aline by doing what?
Intergrating the area under the pressure curve.
ECG leads are positioned throughout the body to
provide different perspectives of the electrical potentials.
What determines the sensitivity of the ECG
Lead selection
Lead II results in the
Largest P wave voltages of any surface lead.
Lead V liest at the
5th ICS at the anterior axillary line.
A true V5 required
At least 5 lead wires
What can cause artifacts?
Electrocautery
Faulty electrodes
Can be printed to compare with intraoperative settings
Preinduction rhythm strip
To interpret ST segment changes properly, ECG must be
Standardized so that 1-mV signal results in a deflection of 10mm on a standard strip monitor.
CVC - CVP monitoring good for
fluid administration to treat hypovolemia and shock infusion of caustic drugs TPN Aspiration of air emboli Insertion of Transcutaneous pacing leads
Contraindications to CVC
Tumors, clots or Tricuspid vegetations that can be dislodged during cannulation
Ipsilateral carotid endarterectomy
CVC catheter tip should be placed where?
Tip should lie at the junction of the SVC and the RA
Most Central lines placed using what technique?
Seldinger techniques.
This is crucial during CVC
IJ vein be cannulated because carotid artery cannulation can lead to hematoma, stroke and AIRWAY COMPROMISE
The risk of vein dilator or catheter placment in the carotid artery can be reduced by ?
transducing the vessel’s pressure waveform or comparing the blood PaO2 with an arterial sample.
What else can confirm the placment other than transducing the vessel pressure?
TEE
Risks of central venous cannulation are
infection
air thrombus
arrhythmias
Pneumothorax
WIth central venous cannulation, arrhythmias indicates that
Catheter tip is in the RA or RV.
Cannulation of this vein is highly assoiated with significant risk of pneumothorax?
Subclavian
Central vein cannulation risk associated with left sided catheterization ?
risk of vascular erosion
Pleural effusion
chylothorax.
CVP approximates ____pressure
RAP
Noncompliant ventricles have
larger pressure swings with smaller volume changes.
Compliant ventricle accomodate
High volume with minimal changes in pressure.
Better indicator of the patient’s volume responsiveness with
Changes associated with volume loading when compulse with other hemodynamic measures (BP, HR, UO)
a wave on the CVP waveform associated with
Atrial contraction
a waves are absent during
Afib
a waves are EXAGGERATED with
Junctional rhythm
Cannon a waves seen with
JUnctional rhythms
c waves caused by
Tricuspid valve elevation during early ventricular contraction
V waves reflect
venous retunr against a closed tricuspid valve.
x descent is the
downward displacement of the tricuspid vlave during systole
y descent is the
tricuspid valve opening during diastole.
Central venous catheter cannulation landmarks
IJ
clavicle
Medial and Lateral head sternocleidomastoid
Mastoid process.
Best position for CVC
Trendelenburg.
What does the PAC provide measurements of
CO and PaOP
Determination of the PA occlusion or wedge pressure permits estimation of what 2 parameters?
LVEDP and ventricular volume.
The PAC can only help measure the LVEDP and ventricular volume in the absence of what?
Mitral stenosis
What is the formula of CO?
CO = HR x SV
What is the formula for BP?
BP = CO x SVR (VIR omh’s law)
Numerous studies for PAC indicated that
Patients with managed PA did worse than patient w/o PA
Relative Contraindications to a PAC why?
Left BBB because of the risk of complete HB
Relative contraindications to a PAC with arrythmias
WPW; ebstein malformation *because of possible tachydysrhythmias , need a catheter with pacing ability
Possible complications of PAC
PULMONARY ARTERY RUPTURE.
Bacteremia
Endocarditis
Pulmonary infarction
How many lumen in a popular PAC? size?
5 lumen; 7.5 Fr catheter
Length of the PAC
110cm
Proximal port of the PAC is how far from the tip
30 cm from the tip
Ventricular port of the PAC is how far from the tip
20 cm for infusions.
Distal port of the PAC is for what?
Aspiration of mixed venous blood samples and measurements of PAP
Insertion of PA catheter requires
central venous access
When inserting a PAC instead of a central venous catheter was is inserted?
A dilator and a sheath are threaded over the guidewire.
During the PAC advancements the ECG should be monitored for
Arrhythmias
Transient ectopy during PAC insertion from irritation of the
RV by the catheter
At what point should the PAC enter the RA?
15cm
During insertion, when is the balloon inflated
after 15-20 cm when the catheter is estimated to be in the RA.
Why is the balloon inflated during insertion of a PAC?
to allow the RV’s cardiac output to direct the catheter forward
What should be done with withdrawal ?
balloon should be deflated
During PAC insertion , you noticed a sudden increase in the systolic pressure, what is the meaning?
Indicates the catheter is in the RV>
What indicates entry to the PA with the PAC insertion?
Sudden increase in diastolic pressure.
Entry to PA normally occur at ______Cm
35-45 cm
After attaining PA position, to obtain PAOP
minimal advancement should be done
The PA tracing should reappear after
the balloon is deflated.
If you notice wedging before maximal inflation of the balloon, what does it mean and what should be done?
an overwedged position, and the catheter should be slightly withdrawn with the balloon down.
Minimize this with PAC and why?
minimize frequency of wedge readings because of the risk of PA rupture.
What can confirm the PAC position?
Chest Radiograph *Xray
Allow continuous measurement of mixed venous blood oxygen saturation?
Optional fiberoptic bundles
Wedge pressure and PAOP: how does it measure wedge
When the distal lumen is properly wedged the PAC is isolated from right-sided pressure by the ballon, therefore, its distal opening is exposed only to PULMONARY CAPILLARY PRESSURE
PAOP or pulmonary capillary wedge pressure (PCWP) equals
Left atrial pressure
PAOP is only accurate at measuring PCWP or PAOP in the absence of
High airway pressure
Pulmonary vascular disease.
When is the Relationship between PAOP and LVEDP unreliable?
Conditions with left atrial or ventricular compliance,
Mitral valve function
Pulmonary vein resistance
Conditions in which PAOP > LVEDP (PEML)
Pulmonary venous obstruction
Elevated alveolar pressure.
Mitral stenosis
Left atrial myxoma
Conditions in which PAOP < LVEDP (DA)
–Decreased LV compliance (stiff ventricle or LVEDP >25mmHg)
–Aortic insufficiency
CO : thermodilution techniques
A known quantity of fluid that is below body temp is injected into RA
Changes in temp of blood in contact with PAC thermistor
The degree of changes is inversely proportional to CO
Thermodilution: CO is measured in
Area under the curve
The degree of change is _______proportional to CO
Inversely
Factors that determine accurate measurements
Injection, temp, volume, computer, electrocautery
rapid and smooth injection
precise injectant temperature and volume
correct computer calibration factors for the type of PAC
avoidance of measurements during electrocautery
Factors accurate PA measurements: physiologic
absence of tricuspid regurgitation and cardiac shunts.
Transpulmonary thermodilution:
Uses thermodilution w/o PAC requires central line and a thermistor equipped. USUALLY FEMORAL not radial arterial catheter.
Transpulmonary thermodilution determine
CO and global end-diastolic volume and extravascular lung water.
Cardiac output: dye dilution:
Is injected through a central venous catheter.
Use only for patients with peripheral access
Lithium Chloride (LiDCO)
Lithium should not be administered to patients in the
1st trimester of pregnancy
CO : pulse contour devices
Arterial pressure trace is used to estimate CO and parameters such as pulse pressure (PPV) and stroke volume variation (SVV)with mechanical ventilation
SVV can only be measured with
mechanical ventilation.
SVV may suggest whether or not
Hypotension is likely to respond to fluid therapy
Pulse contour devices rely on algorithms that measure
The area of the systolic portion of the arterial pressure trace from end diastole to the end of ventricular ejection.
Pulse contour devices must compensate for
dynamic vascular compliance.
CO: Esophageal doppler relies on the
Doppler principle to measure the velocity of blood flow in the descending thoracic aorta.
With Esophageal doppler, Blood in the aorta is in relative motion
compared with the doppler probe in the esophagus.
How does the esophageal doppler work
When blood flows toward the transducer, its reflected frequency is higher than that which was transmitted by the probe. When blood cells move away the frequency is lower than that which was initially sent by the probe.
What is used to determine the velocity of blood flow in the aorta when an esophageal doppler?
Doppler equation
With esophageal doppler the monitor approximates the area in the
Descending aorta using normograms . The SV in the DESCENDING AORTA is calculated.
Knowing the HR with esophageal doppler, allows
calculation of that portion of the CO flowing through the descending thoracic aorta, which is approximately 70% of CO. Correcting for this 30% allow the monitor to estimate that patient’s total CO.
CO : Thoracic bioimpedance method
6 chest electrodes inject microcurrents and sense bioimpedance. Changes in thoracic volume cause chnages in thoracic resistance (bioimpedance) to low amplitue, high frequency currents.
Cardiac output : FICK Principle
Amount of oxygen consume by an individual (VO2) equals the difference between arterial and venous (a-v) oxygen content (C) (CaO2 and CvO2) multiplied by the CO.
Fick’s principle FORMULA: Long
CO = Oxygen consumption / a-v O2 content difference (Ca-Cv)
Fick’s formula
CO = VO2 / Ca-Cv
Oxygen consumption can be calculated from the difference between the
Oxygen content in inspired and expired gas.
Cardiac output : Echocardiography uses
ultrasound to generate images of heart structures.
TTE invasiveneness and disadvantage?
Noninvasive; yet difficult to acquire windows to view the heart.
Ideal option to visualize the heart is (TTE vsTEE)
TEE
Basic hemodynamic information provided by the TEE
Source of hemodynamic instability Whether the heart is adequately volume loaded Contraction good or bad (MI, HF) Not externally compressed OBVIOUS structural defects
What information is provided by advanced TEE?
Form the basis therapeutic and surgical recommendations.
Echocardiography uses the _____effect to do what?
Doppler effect, to evaluate the direction and velocity of blood flow and tissue movement. Using the doppler , it is possible to ascertain the maximal velocity as blood accelerates through a pathologic heart structure such as stenotic aortic valve.
Echocardiography uses those 2 things
Doppler Effect
Bernoulli equation.
Bernouli equation is
Pressure change = 4V^2 (V is the area of maximal velocity)
What does bernoulli equation allow us to do?
Determine the pressure gradient between areas of different velocity .
How does color-flow doppler work?
Creates a visual picture of the heart’s blood flow by assigning a color code to the velocities in the heart.
With color-flow doppler, blood flow directed away from the echocardiographic transducer is colored
blue
With color-flow doppler, blood flow directed towards the echocardiographic transducer is colored
RED
Flow pattern changes are used to identify areas of
pathology
Cardiac output can be measure with TTE or TEE based on what principle?
Assuming that the Left ventricular outflow tract is a cylinder, diameter can be measured and then the area through which the blood flow is calculating using the equation AREA= 0.785 x Diameter ^2 . A doppler BEAM is aligned in parallel to the LVOT, AND the velocities passing through it are used by the computer to integrate the velocity /time curve to determine the distance that the blood traveled.
CO measurement with TTE or TEE is using the formula
Area = 0.785 x Diameter ^2
Normal Tissue velocity is
8-10cm /s
Reduced myocardial velocities associated with
impaired diastolic funciton
High LVED pressures
Valve replacement surgery necessitates what kind of monitoring? why?
Arterial blood pressure monitoring; because of anticipated BP swings and the need for precise beat-to-beat BP regulation to guide the administration of vasoactive medications.
Pt has a hx of vascular insufficiency such as RAYNAUD phenomenon, is radial artery a contraindications?
No
This valve stuck can lead to increased airway pressures
Stuck expiratory valve.
Beta blocker and bronchospam
May exacerbate bronchospasm
Mainstem intubation would likely have presented as
Increased airway pressure RIGHT AFTER INTUBATION.
