APEX: Monitoring II: HEMO Flashcards
A blood pressure cuff that is too large requires
less pressure to occlude the artery
An improperly sized NIBP cuff leads to
inaccurate results
The Ideal bladder length equals
80 % of the EXTREMITY CIRCUMFERENCE
The Ideal bladder Width equals
40% of the EXTREMITY circumference
A cuff that is too small
Overestimates SBP
A cuff that is too large
Underestimates SBP
Although rare, nerve injury due to NIBP measurements tends to affect the
ulnar or median nerve.
The auscultation method relies on the
Korotfoff sounds
There are how many sounds with BP cuff
five
Where is the SBP measured with BP measurement
First sound
Where is the DBP measured with BP measurement
Last sound
Uses the Oscillatory Method of BP
Automated NIBP machines
How does the oscillatory method of SBP work
Inflatable cuff occlude arterial blood flow and as the cuff pressure is released, the monitor measure the pressure fluctuations that occur in response to arterial pulsations
With oscillatory method, SBP is measured when
Oscillations first appears (The appearance of flow after occlusion by the cuff)
With oscillatory method, MAP is measured when
When the amplitude of the oscillation is greatest
With oscillatory method, DBP is measured when
at the minimum pressure where oscillation can still be registered.
With oscillatory method, which measurement is most susceptible to error
DBP
The oscillatory method requires
Pulsative flow,
Because The oscillatory method requires so a NIBP wont function in those patients
pt on CBP or with a LVAD. Those patients require an A-line
Cuff Location : as the pulse move from the aortic root towards the periphery the systolic pressure_____and the diastolic pressure _______and the pulse pressure _____
Increases ; decreases; widents.
What remains constant through the arterial tree
MAP
At the aortic root, the SBP is the _____And DBP is the ________and PP is the
Lowest, highest, narrowest
At the dorsalis pedis, the SBP is the _____And DBP is the ________and PP is the
highest, lowest, widest
Blood in the circulation behaves like a column of fluid and follows the rules of
Hydrostatic pressure.
If the BP cuff location is above the heart , the BP reading will be
falsely decrease (there is less hydrostatic pressure)
If the BP cuff location is below the heart , the BP reading will be
Falsely increase (there is more hydrostatic pressure)
For every 10cm change, the BP changes by
7.4 mmHg
For every inch change, the BP changes by
2 mmHg
For examples the BP cuff is 10 inches below the level of the heart, what is the true BP at the level of the heart?
10 inch x 2 mmHg = 20 mmHg
The BP on the monitor falsely increases, therefore the BP at the heart is 20mmHg less than what you see on the monitor.
Never measure BP in the Calf when patient is in these 2 positions? why?
Revere Tredelenburg or SITTING. Because cerebral ischemia may occur with a normal BP on the monitor.
Complications of BP on the limb
Neuropathy (radial, ulnar and median)
Limb ischemia
Compartment syndrome
Complications of BP other
Pain
Bruising
Petechiae
Interference with IV medications
Where to not put BP cuff
over a PICC line
Bone fracture
Limb with an AV fistula.
Avoid BP in arm with Severe axillary node dissection why?
May impair lymphatic drainage and cause limb edema, .
Arterial BP waverform: Dicrotic notch indicates______followed by
AV closure; Diastolic runoff
A-line where is systolic BP read
Peak of the waveform
A-line where is DBP read
Trough of the waveform
A-line where is PP read
Peak - trough
A-line where is contractility
Upstroke
A-line where is SV read
Area under the curve
A-line what does the dicrotic notch indicates
Closure of aortic valve
Is the height of the dicrotic notch a reliable estimate of SVR
NO
Optimally damped system:
Baseline is re-established after 1 oscillation
Under- damped system: baseline, SBP, DBP and MAP
Baseline is re-established after several oscillations (SBP is overestimated, DBP is underestmiated, and MAP is accurate.
Over- damped system: baseline, SBP, DBP and MAP
Baseline is re-established after no oscillations (SBP is underestimated, DBP is overestimated, and MAP is accurate.
Causes of OVERDAMPED SYSTEM
AIr bubble
Clot in the pressure tubling
Low flush bag pressure.
Invasive blood pressure monitors measure BP at the
Level of the transducer
As long as the transducer is at the ___________ changes in body or extremity position will not affect the accuracy of the arterial BP measurement.
Level of the right atrium
When inserting a central line in the Right IJ vein, how far should the catheter be advanced to achieve correct placement?
15 cm
The tip of the CVC should reside where?
the junction of the vena cava and the Right atrium. It SHOULD NOT ENTER THE Right atrium
The distance from SKIN to the junction of the VC and RA is
15 cm.
Why should the tip of the CVC be placed in the RA?
It will increase the risk of dysrhythmias, thrombus formation and cardiac perforation
The tip of the PAC should reside where?
in the pulmonary catheter, distal to the pulmonic valve.
Tip of PAC in relation to the VC junction
2535cm
Insertion site to VC and RA junction: Right IJ insertion site.
15cm
Insertion site to VC and RA junction: Left IJ insertion site.
20 cm
Insertion site to VC and RA junction:Femoral insertion site.
40cm
Insertion site to VC and RA junction: Subclavian insertion site.
10cm
Vena Cava and R atrial Junction –> catheter tip: RA
0-10cm
Vena Cava and R atrial Junction –> catheter tip: RV
10-15cm
Vena Cava and R atrial Junction –> catheter tip: PA
15-30cm
Vena Cava and R atrial Junction –> catheter tip: PAOP position
25-35 cm
While obtaining venous access possible complications are
Arterial puncture Pneumothorax AIr embolism Neuropathy Catheter knot
During catheter residence complications are
Bacterial colonization of catehter, heart or PA Myocardial or valvular injury Sepsis Thrombus formation Thrombophlebitis Misinterpretation of data
What are the risk of obtaining access via left IJ?
Puncturing the thoracic duct. This can cause CHYLOTHORAX (lymph in the chest)
What is the most common complication while obtaining access?
Dysrhythmias
What is thest best way to treat PACs and PVCs during PAC insertion?
Withdraw the catheter and start over
The incidence of catheter related infection increases after how many days?
3
Who shouldn’t you float a PAC in ? why?
Patient with LBBB. Because advancing the catheter into the RV can cause a RBBB and this can put the patient in a complete HB.
What is the classic presentation of PULMONARY ARTERY RUPTURE?
Hemoptysis
Major complication of PAC
Pulmonary artery rupture.
Pulmonary artery rupture chances increases if
Balloon is inflated with more than 1.5 ml
The risk of pulmonary artery rupture is increased by patient factors such as
Anticoagulation
Hypothermia
Advanced age.
The risk of pulmonary artery rupture is increased by Providers factors such as
Inserting catheter too far prolonged balloon inflation chronic irritation of vessel wall unrecognized wedging filling the balloon with liquid instead of air
CVP passive filling is the ___Wave
V wave
The CVP waveform is a reflection of the pressure inside the
RA
CVP waveform has ____Peaks and ______troughs
3; 2
Tricuspid valve elevation into RA is the ____wave
C
Downward movement of contracting RV is _____descent
x descent
RA empties through open tricuspid
y descent
A wave Mechanical event vs electrical events
Right atrial contraction (mechanical)
Just after the P wave (Atrial depolarization)
C wave Mechanical event vs electrical events
Right ventricular contraction (bulding of Tricuspid in RA)’->mechanical
Just after the QRS complex (ventricular depolarization)
X Descent Mechanical event vs electrical events
RA relaxation (mechanical) ST se
X Descent Mechanical event vs electrical events
RA relaxation (mechanical) ST segment (Electrical event)
V wave Mechanical event vs electrical events
Passive filling of RA (mechanical)
Just after T wave begins (ventricular repolarization)
Y descent Mechanical event vs electrical events
RA empties through open tricuspid valve (mechanical)
After T wave ends
CVP and PEEP
Increase PEEP
PEEP and PVR
Increases PVR which creates additional resistance against RV ejection, which can increase RVEDP and CVP.
A transducer above the zero point and CVP
Underestimated CVP
Pericardial tamponade produces a
Compressive force around the hearts. This reduces RA compliance and increases (Not decreases) CVP
VSD typically ________RVEDV and CVP
Increases
Where should CVP be zeroed?
AT the phlebostatic axis
Where is the Phlebostatic axis?
4th intercostal space MID anteroposterior level
A transducer placed below the zero point
overestimated CVP
When should CVP be measured?
End Expiration
During this phase of the ventilatory cycle , end expiration , what happens to pressure?
Extravascular pressure equals atmospheric pressure, and this allows us to measure CVP relative to Atmospheric pressure.
CVP measurement is not affected by _____Pressure if the reading is recorded at end-expiration
Intrathoracic pressure
The normal CVP in the adults
1 - 10 mmHg
CVP is a funciton of
Intravascular volume
venous tone
RV compliance.
Right atrial pressure reflects
LV End Diastolic pressure
In a perfect world, Right ventircular output equals
LV output
Low CVP usually means
low intravascular volume
High CVP indicates
Hypervolemia
Reduce ventricular compliance
Increase Intrathoracic pressure.
2 factors that decrease CVP
Transducer above the phlebostaxis axis
Hypovolemia
Constrictive pericarditis on CVP
increase
VSD on CVP
increase
PEEP on CVP
INCREASE
Pulmonic stenosis or tricuspid stenosis
INCREASE
RV failure and CVP
increase
Conditions that increase the amplitude of the a wave on the CVP waveform?
Tricupid stenosis
Diastolic dysfunction
Loss of a wave of CVP corresponds to
Atrial fibrillation
V-pacing if the underlying rhythm is ASYSTOLE
Large a wave occurs when
Atria contracts and EMPTIES AGAINST A HIGH RESISTANCE such as resistance at the valve or NONcompliant ventricle.
Valve condition associated with large a wave
Tricuspid stenosis
Diastolic dysfunction
Heart condition associated with large a wave
Myocardiac ischemia
AV disssociation
V pacing asynchronous
PVCs
Lung condition with large a wave
Chronic lung disease leading the RV hypertrophy
Large V wave occurs when
Tricuspid regurgitation allows a portion of the RV colume to pass through the closed by incompetent tricuspid valve during RV systole. This increases the volume and presure in the RA and manifests as LARGE V WAVES>
3 conditions associated with LARGE V waves
Tricuspid regurgitation
Acute increase in intravascular volume
RV papillary muscle ischemia
Cannon a waves seen with
atrium contracting against a closed tricuspid valve, as seen during AV dissociation.
FIndings once PA catheter enter PA
Dicrotic notch
Increased DIASTOLIC BLOOD PRESSURE
Normal RAP is
1 - 10 mmHg
Normal RVP Systolic/Diastolic
15-30 / 0-8 mmHg
Normal PAP Systolic/Diastolic
15-30 / 5-15 mmHg
Normal PAOP
5 - 15 mmHg
RVP what happens to SBP and DBP
SBP increase
DBP is equal to CVP
PAP what happens to SBP and DBP
SBP remains same
DBP increases
Dicrotic notch formed during pulmonic valve closure during diastole
In which lung zone should the tip of the PAC be placed?
Three (zone III)
Why zone III for the placement of the PAC?
because it provides the most accurate estimation of LVEDP.
Each lung zone is defined by the what 3 factors
Relative pressure in the alveolus
Arterial pulmonary capillary
Venous pulmonary capillary
Zone III is defined as
P arterial > P venous > P Alveolus
In what region is zone III?
Dependent
Zone III in a sitting position is
At the lung base
Zone III in a supine position
Towards the back
Zone III in a prone position
Towards the chest
Zone III in a lateral position
Towards the dependent
How can you tell the tip of PAC is in Zone III
PaOP > pulmonary artery EDP
Inability to aspirate blood from the distal port when the balloon is in the wedged position.
When does pulmonary artery occlusion pressure overestimated LVEDP?
PEEP
Diastolic dysfunction
Anything that impairs the normal pressure gradient between the PAC tip and the
LV can impact PAOP
PAOP underestimates LVEDV in
Aoritc insufficiency.
When PAOP DOES NOT accurately predict LVEDV? and overestimates it: Pulmonary
COPD
PEEP
Pulmonary HTN
Non west zone III placement for PAC
When PAOP DOES NOT accurately predict LVEDV? and overestimates it: Heart
Impaired LV compliance (ischemia) MV disease (stenosis or regurgitation) L to R cardiac shunt Tachycardia PPV
Which situation underestimates CO obtained by the thermodilution method?
High Injectate volume
CO is_________ to the area under the curve with the thermodilution
Inversely proportional
A high injectate volume _______CO
Underestimates
A low injectate volume _______CO
Overestimates
Injectate that is too warm will_______CO
Overestimates CO
A right to left intracardiac shunt has an
Unpredictable on CO measurement.
What is the most common way to measure CO with the PAC?
Thermodilution method
Explain the thermodilution method?
An injection of dextrose or 0.9% NaCL of known quantity and temperature is bolused through the PROXIMAL port on the PAC. each injection should occur during the same phase of the respiratory cycle and be completed < 4 seconds. Average 3 separate injections to get final CO.
If CO is high, the injectate ______and the AUC is
Travels toward the distal tip of the PAC. AUC is smaller
If CO is low, it takes ______And the AUC is ______
longer for the injectate to travel past the distal tip of the PAC, the AUC is larger
Factors that influence themodilution CO measurement: Underestimate CO
Injectate volume too high
Injectate solution too cold
Factors that influence themodilution CO measurement: Overestimate CO
Injectate volume too low
Injectate solution too hot
Partially wedged PAC
Thrombus on tip of PAC
Factors that influence themodilution CO measurement: Unable to predict
Intracardiac shunt
TR
There is a _______Delay between the time CO is measured and when it appears on the monitor
30 seconds
Factors that increased Mixed venous oxygen saturation?
Sodium nitroprusside toxicity
Sepsis
SvO2 (mixed venous O2 sat) is a function of what variables:
CO
Arterial oxygen saturation
Amount of Hgb
Oxygen consumption
Thyroid storm on SvO2
oxygen demand and decreases SvO2
Cyanide toxicity on SvO2
Impaired O2 utilization , and sepsi
Sepsis on SvO2
High cardiac output state increase SvO2
Anemia on SvO2
Anemia reduces oxygen delivery , and decreases SvO2
Four variables for calculations of SvO2
Q = Cardiac output (L/min) VO2 = Oxygen consumption (mL O2/min) Hgb = Amount of hemoglobin (g /dL) SaO2 = Loading of Hgb in arterial Blood (%)
SvO2 formula:
SaO2 - VO2/ (Q x 1.34 x Hgb x10)
Normal SvO2
65-75%
Mixed venous oxygen saturation an indirect monitor of CO when
hgb, SaO2 and VO2 are held constant.
Factors that change SvO2
When oxygen consumption increases or oxygen delivery decreases, the oxygen content returning to the heart decreases, as manifested as a decreased SvO2
Mixed Venous O2 sat is decreased by either
Increased O2 consumption OR Decreased O2 delivery
Mixed Venous O2 sat is increased by either
Decreased O2 consumption OR increased O2 delivery
Increased O2 delivery by _____PaO2, Increased _______ and ______
Increased; hgb and CO
Decreased O2 consumption occur with
Hypothermia
Cyanide toxicity
Increased O2 consumption occur with
Thyroid storm Stress Fever Shivering Pain
Decreased O2 delivery by _____PaO2, Increased _______ and ______
Decreased, decreased Hgb, and CO
Sepsis creates a
High CO state
Why is there an increase SvO2 with sepsis
Even though sepsis causes end organ hypoxia, O2 bypasses the tissues and SvO2 remains elevated
Increased SvO2 and tissues
Impaired oxygen uptake by tissues.
Classic example of impaired oxygen uptake by tissues
Cyanide poisoning from sodium nitroprusside
Mixed oxygen venous
Left to RIght shunt. Oxygenated blood travels from the left heart to the right heart and is added to pulmonary venous blood.
What do you need to measure SvO2 and why?
PAC is needed because different organs extract different amounts of O2, a true mixed venous sample must contain blood returning from the SVC, IVC, and the coronary sinus.
Preload responsiveness is expected to be present if a 200-250ml fluid bolus increases the SV in excess of
10 %
Most of the pulse contour monitors use the ______to complete their calculations
Arterial waveform or the SPO2 waverorm to complete their calculations.
Pulse contour analysis provides a measure of
Preload responsiveness as a function of how SV changes during the respiratory cycle (assumes PPV).
What can influence SV
Changes in intra-thoracic pressure duing PPV
Inspiration on LV filling
A positive pressure breath augments LV filling (compression of the pulmonary veins and pleural restriction impedes RV filling)
Increases LV filling on SV
Increases SV
Expiration on LV filling
LV filling decreases (decreases RV preload on previous beats reduces LV preloads, the time delay is called pulmonary transit time.
Decreases LV filling on SV
Reduces stroke volume
A hypovolemic patient will have a ________stroke volume variation throughout the respiratory cycle as a function of intrathoracic pressure’s effect on RV filling and function
GREATER DEGREE of SVV
Dynamic measures of the pulse contours are
SVV, SPV, PPV, PVI
Dynamic measures of the pulse contours tend to predict volume responsiveness when the calculated measurement is greater than
13-15 %
Limitations of pulse contous
NOt used with spontaneous ventilation Open chest dysrhythmias PEEP Small tidal volume
Gold standard for assessing myocardial function
TEE
2nd is ESOPHAGEAL DOPPLER
The tip of the esophageal probe should be positioned
~ 35 cm from the incisors. or at the 3rd sternocostal junction
Do not use the ESOPHAGEAL DOPPLER IF THE PATIENT HAS
Esophageal disease
Definition of SV
Volume of blood pumped by LV per beat/min
Definition of SI
SV indexed to BSA
SVV (stroke volume variation)
Change in strove volume per beat
Peak velocity
Index of contractility
Peak velocity Definition
Index of contractility
Flow time Definition
Time between aortic opening and closure
Stroke distance Definition
How far SV is pumped per beat
T wave corresponds with _____wave
V wave
ST segment corresponds with _______
X descent
QRS complex corresponds with
C wave
V wave is the
passive filling
X descent is
Right atrial relaxation
