Hemodynamics Flashcards
Changes in what lead(s) would indicate inferior wall ischemia (right coronary artery)?
II, III, aVF
Changes in what lead(s) would indicate lateral wall ischemia (circumflex branch of left coronary artery)?
I, aVL, V5-V6
Changes in what lead(s) would indicate anterior wall ischemia (left coronary artery)?
V3-V4
Changes in what lead(s) would indicate septal wall ischemia (left descending coronary artery)?
V1-V2
ST-segment changes to leads II, III, and aVF could indicate ischemia to what area of the heart?
Inferior wall (right coronary artery)
ST-segment changes to leads I, aVL, V5-V6 could indicate ischemia to what area of the heart?
Lateral wall (circumflex branch of left coronary artery)
ST-segment changes to leads V3-V4 could indicate ischemia to what area of the heart?
Anterior wall (left coronary artery)
ST-segment changes to leads V1-V2 could indicate ischemia to what area of the heart?
Septal wall (left descending coronary artery)
What two leads are the standard of monitoring for HR/arrhythmia detection and for ischemia?
Lead II for HR and arrhythmia detection. Lead V5 for ischemia.
What are the principle indicators for ischemia detection on ECG?
ST-segment elevation >/= 1mm
ST-segment depression >/= 1mm
T wave flattening or inversion
Peaked T waves
Development of Q waves
Arrhythmias
What should you do if you suspect ischemia and why?
Get a TEE so that you can look at wall motion abnormalities. Then work on your supply/demand (decrease HR, increase BP).
Changes in SBP correlate with changes in…
…myocardial O2 requirements.
Changes in DBP reflect…
…coronary perfusion pressure.
What should a well-fitted NIBP cuff bladder’s width extend to (in relation to patient’s arm)?
Bladder width should be approximately 40% of the circumference of the extremity
What should a well-fitted NIBP cuff bladder’s length extend to (in relation to patient’s arm)?
Bladder length should be sufficient to encircle at least 80% of the extremity
Potential reasons for falsely high NIBP measurements
Cuff too small
Cuff too loose
Extremity below level of heart
Arterial stiffness (HTN, PVD)
Potential reasons for falsely low NIBP measurements
Cuff too large
Extremity above level of heart
Poor tissue perfusion
Too quick deflation
What patient populations are more vulnerable to NIBP measurement complications?
Peripheral neuropathies
Arterial/Venous insufficiencies
Severe coagulopathies
Recent use of thrombolytic therapy
What are complications of noninvasive blood pressure (NIBP) measurement?
Compartment syndrome
Limb edema
Pain
Peripheral neuropathy
Petechiae and ecchymoses
Venous stasis and thrombophlebitis
List the indications for arterial line cannulation.
- Continous, real-time blood pressure monitoring
- Planned pharmacologic or mechanical cardiovascular manipulation (elective deliberate hypotension)
- Supplementary diagnostic information from the arterial waveform
- Wide swings in intra-op BP or risk of rapid changes in BP
- Rapid fluid shifts
- Titration of vasoactive drugs
- End-organ disease
- Repeated blood sampling
- Failure of indirect BP measurement
How is the morphology of the arterial wave form affected with different arterial catheter sites?
As the pressure wave travels from the central aorta to the periphery:
- arterial upstroke becomes steeper
- systolic peak increases
- dicrotic notch appears later
- diastolic wave becomes more prominent
- end-diastolic pressure decreases
How do pressures compare between the central aorta and peripheral arterial waveforms?
Peripheral arterial waveforms have:
- higher systolic pressure
- lower diastolic pressure
- wider pulse pressure
Potential causes of overdamped arterial pressure waveforms
- Arterial spasm
- Air bubbles
- Blood clots
- Loose connections
- Kinks
- Narrow tubing
Potential causes of underdamped arterial pressure waveforms
- Catheter whip or artifact
- Stiff non-compliant tubing
- Hypothermia
- Tachycardia or dysrhythmia
Actions for damped arterial pressure waveforms
- Pressure bag inflated to 300 mmHg
- Reposition extremity or patient
- Verify appropriate scale
- Flush or aspirate line
- Check or replace module and/or cable
Arterial line complications
- Distal ischemia, pseudoaneurysm, arteriovenous fistula
- Arterial aneurysm
- Arterial embolization, thrombosis
- Vasospasm
- Peripheral neuropathy
- Nerve damage
- Hemorrhage/Hematoma
- Infection
- Air embolus
- Skin necrosis
- Loss of digits
- Retained guidewire
- Misinterpretation of data
- Misuse of equipment
What arterial blood pressure waveform abnormalities result from aortic stenosis?
Pulsus parvus (narrow pulse pressure)
Pulsus tardus (delayed upstroke)
What arterial blood pressure waveform abnormalities result from aortic regurgitation?
Bisferiens pulse (double peak)
Wide pulse pressure
What arterial blood pressure waveform abnormalities result from hypertrophic cardiomyopathy?
Spike and dome (mid-systolic obstruction)
What arterial blood pressure waveform abnormalities result from systolic left ventricular failure?
Pulsus alternans (alternating pulse pressure amplitude)
What arterial blood pressure waveform abnormalities result from cardiac tamponade?
Pulsus paradoxus (exaggerated decrease in systolic blood pressure during spontaneuous inspiration)
What does pulse pressure variation measure?
Fluid responsiveness
How does positive pressure ventilation increase left ventricular preload and reduce left ventricular afterload?
Increases in lung volume compress lung tissue and displace blood contained within the pulmonary venous reservoir into the left heart chambers, thereby increasing left ventricular preload.
The increase in intrathoracic pressure reduces left ventricular afterload.
What effects do the increase in LV preload and decrease in afterload (from positive pressure ventilation) produce?
- Increase in cardiac output
- Increase in LV stroke volume
- Increase in systemic arterial pressure
In general, what are the ideal conditions for measuring pulse pressure variation accurately?
- Mechanical ventilation with tidal volumes 8-10 mL/kg
- Positive end-expiratory pressure 5 mmHg or greater
- Regular cardiac rhythm
- Normal intra-abdominal pressure
- Closed chest
For pulse oximetry, why do we use two different wavelengths of light when referencing it to ambient light?
At 660 nm, light absorption is greater by deoxyhemoglobin than by oxyhemoglobin. At 940 nm, light absoption is greater by oxyhemoglobin than by deoxyhemoglobin.
What are four major sources of artifacts in pulse oximeter readings?
- Ambient light (covering sensor with opaque shield can minimize)
- Low perfusion (weak pulse, low AC-to-DC signal ratio)
- Venous blood pulsations (caused by patient motion)
- Additional light absorbers in the blood (dyshemoglobins, intravenous dyes)
What are uses for pulse oximetry?
Detection of hypoxemia
Detection of perfusion
What are potential causes of inaccuracies in pulse oximetry readings?
- Malposition of probe
- Dark nail polish
- Different hemoglobin
- Dyes
- Electrical interference
- Shivering
What conditions would cause a right shift of the oxyhemoglobin dissociation curve?
- Acidosis
- Hypercarbia
- Hyperthermia
- Increased DPG (diphosphoglycerate concentration)
What conditions would cause a left shift of the oxyhemoglobin dissociation curve?
- Alkalosis
- Hypocarbia
- Hypothermia
- Decreased DPG (diphosphoglycerate concentration)
- Carboxyhemoglobin
- Fetal hemoglobin
What happens with oxygen and hemoglobin with a left shift on the oxyhemoglobin dissociation curve?
There is increased oxygen affinity of hemoglobin, allowing less oxygen to be available to the tissues.
What happens with oxygen and hemoglobin with a right shift on the oxyhemoglobin dissociation curve?
There is decreased oxygen affinity of hemoglobin, allowing more oxygen to be available to the tissues
What is considered the gold standard for SaO2 measurements and is relied on when pulse oximetry readings are inaccurate or unobtainable?
Co-oximetry
In a patient with carbon monoxide poisoning, the SpO2 is falsely _________.
Elevated
At what wavelength does MetHb absorb light, and what is the result?
Methemoglobin absorbs a significant amount of light at both 660 and 940 nm. As a result, in its presence, the ratio of light absorption R approaches unity. An R value of 1 represents the presence of equal concentrations of O2Hb and deO2Hb and corresponds to an SpO2 of 85%.
In a patient with methemoglobinenia, what is the SpO2?
In a patient with methemoglobinenia, the SpO2 is 80% to 85% irrespective of the SaO2.
What are the indications for central venous cannulation?
- Central venous pressure monitoring
- Pulmonary artery catheterization and monitoring
- Transvenous cardiac pacing
- Temporary hemodialysis
- Drug administration (concentrated vasoactive drugs, hyperalimentation, chemotherapy, agents irritating to peripheral veins, prolonged antibiotic therapy)
- Rapid infusion of fluids via large cannulas (trauma, major surgery)
- Aspiration of air emboli
- Inadequate peripheral intravenous access
- Sampling site for repeated blood testing
What are the insertion sites for CVCs?
- Right internal jugular vein
- Left internal jugular vein
- Subclavian veins
- External jugular veins (not common)
- Femoral veins
What is the preferred site for CVC and why?
Right IJ is preferred.
- Consistent, predictable anatomic location of the internal jugular vein
- Readily identifiable and palpable surface landmarks
- *Short straight course to the superior vena cava
What is anatomically different about the left IJ compared to the right IJ?
The left IJ is often smaller than the right and demonstrates a greater degree of overlap of the adjacent carotid artery.
What is the anatomic disadvantage that pertains to all left-sided catheterization sites and what does this highlight?
Any catheter inserted from the left side of the patient must traverse the innominate (left brachiocephalic) vein and enter the superior vena cava perpendicularly. As a result, the catheter tip may impinge on the right lateral wall of the superior vena cava, increasing the risk of vascular injury.
This highlights the need for radiographic confirmation of proper catheter tip location.
How do you confirm CVC placement in OR?
Aspirate blood from all ports and obtain xray after surgery.
Ideally, where is the tip of the CVC located?
Just above junction of venae cava and the right atrium, parallel to vessel walls, positioned below the inferior border of the clavicle and above the level of 3rd rib, the T4/T5 interspace, the carina, or takeoff right main bronchus.
Rapid intravascular fluid resuscitation is most efficient with what kind of catheter?
Short, large-bore, peripheral intravenous catheters, because CVCs are longer and have narrower individual lumina, significantly increasing resistance to flow.
What are some contraindications of CVC placement?
- Right atrial tumor
- Contralateral pneumothorax
- Infection at site
What is the most important life-threatening vascular complication of central venous catheterization?
Cardiac tamponade resulting from perforation of the intrapericardial superior vena cava, right atrium, or right ventricle.
If arterial puncture with a small needle occurs during central venous cannulation, what should be done?
The needle should be removed and external pressure applied for several minutes to prevent hematoma formation.
When unintentional carotid artery cannulation with a dilator or large-bore catheter occurs, what should be done?
The dilator or catheter should be left in place and a vascular surgeon consulted promptly regarding removal.
What are the complications for central venous cannulation?
- Vascular injury: arterial, venous, cardiac tamponade
- Respiratory compromise: airway compression from hematoma; pneumothorax
- Nerve injury
- Arrhythmias
- Thromboembolic: venous thromboses, pulmonary embolism, arterial thrombosis and embolism, catheter or guidewire embolism
- Infectious: insertion site infection; catheter infection; bloodstream infection; endocarditis
- Misinterpretation of data
- Misuse of equipment
If unintentional carotid artery cannulation occurs with a dilator or large-bore catheter, what are the severe complications that can result if the catheter is immediately removed?
Hemothorax, arteriovenous fistula, pseudoaneurysm, and cerebral infarction.
Open or endovascular repair followed by careful neurologic monitoring (and hence postponement of any elective surgical procedure) is usually required.
“a” wave on CVP
Caused by atrial contraction, which occurs at end-diastole following the ECG P wave. Atrial contraction increases atrial pressure and provides the atrial kick to fill the right ventricle through the open tricuspid valve.
“c” wave on CVP
The “c” wave is due to isovolumetric right ventricular contraction. Atrial pressure decreases following the a-wave, as the atrium relaxes. A transient increase in atrial pressure is produced by isovolumentric ventricular contraction, which closes the tricuspid valve and displaces it toward the atrium, causing the c-wave. The c-wave always follows the ECG R wave because it is generated during onset of ventricular systole.
“x” descent on CVP
- systolic decrease in atrial pressure due to atrial relaxation
- mid-systolic event
“v” wave on CVP
- ventricular ejection, which drives venous filling of the atrium
- occurs in late systole with the tricuspid valve still closed
- occurs just after the T-wave on ECG
“y” descent on CVP
Diastolic decrease in atrial pressure due to flow across the open tricuspid valve
CVP a-wave phase of cardiac cycle
end-diastole
CVP c-wave phase of cardiac cycle
early systole
CVP v-wave phase of cardiac cycle
late systole
CVP x-descent phase of cardiac cycle
mid-systole
CVP y-descent phase of cardiac cycle
early diastole
CVP waveform abnormalities from atrial fibrillation
- loss of a-wave
- prominent c-wave
CVP waveform abnormalities from atrioventricular dissociation
cannon a-wave
CVP waveform abnormalities from tricuspid regurgitation
- tall systolic c-v wave
- loss of x-descent
CVP waveform abnormalities from tricuspid stenosis
- tall a-wave
- attenutation of y-descent
CVP waveform abnormalities from right ventricular ischemia or pericardial constriction
- tall a and v-waves
- steep x and y-descents
- M or W configuration
CVP waveform abnormalities from cardiac tamponade
- dominant x-descent
- attenuated y-descent
When should CVP be measured?
At end-expiration
How is pulmonary artery pressure monitoring done and what does it assess?
Right-sided heart catheter used for direct bedside assessment of:
- Intra-cardiac pressures (CVP, PAP, PCWP/PAWP)
- Estimate LV filling pressures
- Assess LV function
- CO
- Mixed venous oxygen saturation
- PVR and SVR
What are the components of pulmonary artery pressure catheters?
- 7 french (introducer is 8.5 french)
- 110 cm length marked at 10 cm intervals
- 4 lumens
- distal port = PAP
- second port (30 cm, more proximal) = CVP
- third lumen = balloon
- fourth wires = temp thermistor
Indications for PA pressure monitoring
- LV dysfunction
- Valvular disease
- Pulmonary HTN
- CAD
- ARDS/Respiratory failure
- Shock/sepsis
- ARF
- Surgical procedure: cardiac, aortic, OB
Relative contraindications of PA cath
- WPW syndrome
- Complete LBBB
PA cath complications
- Arrhythmias (including vfib, RBBB, complete heart block)
- Catheter knotting
- Balloon rupture
- Thromboembolism; air embolism
- Pneumothorax
- PA rupture
- Infection (endocarditis)
- Damage to cardiac structures (valves, etc.)
How do we determine the location of the PA cath?
Waveform changes and appropriate distance (cm) markings
PCWP waveform ‘a’ wave
Respresents contraction of the left atrium. Normally it is a small deflection unless there is resistance in moving blood into the left ventricle as in mitral stenosis.
PCWP waveform ‘c’ wave
Due to rapid rise in the left ventricular pressure in early systole, causing the mitral valve to bulge backward into the left atrium, so that the atrial pressure increases momentarily.
PCWP waveform ‘v’ wave. What does a prominent ‘v’ wave reflect?
Produced when blood enters the left atrium during late systole.
A prominent ‘v’ wave reflects mitral insufficiency causing large amounts of blood to reflux into the left atrium during systole.
Methods for cardiac output monitoring
- Thermodilution
- Continuous thermodilution
- Mixed venous oximetry
- Ultrasound
- Pulse contour
What are the 7 cardiac parameters obserevd from a transesophageal echocardiography?
- Ventricular wall characteristics and motion
- Valve structure and function
- Estimation of end-diastolic and end-systolic pressures and volumes (EF)
- CO
- Blood flow characteristics
- Intracardiac air
- Intracardiac masses
What are the uses for transesophageal echocardiography in the OR?
- Unusual causes of acute hypotension
- Pericardial tamponade
- Pulmonary embolism
- Aortic dissection
- Myocardial ischemia
- Valvular dysfunction
- Valvular function
- Wall motion
What are the complications of a TEE?
- Esophageal Trauma
- Dysrhythmias
- Hoarseness
- Dysphagia
Normal values for HR, arterial O2 saturation, SBP, DBP, and MAP
HR: 60-90 beats/min
SpO2: 95%-100%
SBP: 90-140 mmHg
DBP: 60-90 mmHg
MAP: 70-105 mmHg
Normal value of systolic pressure variation (SPV)
5 mmHg
Normal value of pulse pressure variation (PPV)
10%-13%
Normal value of CVP
2-6 mmHg
Normal value of right ventricular pressure
15-30/2-8 mmHg
Normal value of pulmonary artery pressure (PAP)
15-30/5-15 mmHg
Normal value of mean pulmonary arter pressure
9-20 mmHg
Normal value of pulmonary capillary wedge pressure (PCWP)
6-12 mmHg
Normal value of left atrial pressure
4-12 mmHg
Normal value of cardiac output (Q or CO)
4-8 L/m
Normal value of cardiac index (CI)
2.4-4 L/min/m2
Normal value of ejection fraction (EF)
55%-70%
Normal value of end-diastolic volume
65-240 mL
Normal/calculated values for stroke volume (SV), stroke volume index (SVI)
50-100 mL/beat
33-47 mL/m2/beat
Calculated value of systemic vascular resistance (SVR)
800-1300 dynes • sec/cm5
Calculated value of pulmonary vascular resistance (PVR)
<250 dynes • sec/cm5
Normal respiratory parameters
RR: 12-20 breaths/min
Peak inspiratory pressure (PIP): 15-20 cm H20
Tidal Volume (VT): 6-8 mL/kg ideal body weight
End-tidal CO2: 35-40 mmHg
What is end-diastolic volume (EDV)?
Preload. The volume of blood in the ventricles at the end of atrial systole, just prior to atrial contraction.
(65-240 mL)
What is stroke volume (SV)?
The amount of bloof pumped from the ventricles during ventricular systole.
(50-100 mL/beat)
What is end-systolic volume (ESV)?
Volume of blood remaining in the ventricles following contraction.
(~50-60 mL)
What is the phlebostatic axis?
4th intercostal space along the mid-axillary line
How are pressure readings affected if the arterial line transducer has not been levelled to the phlebostatic axis?
Pressure readings will either be falsely high or falsely low
In regards to the arterial line, a 20-cm difference in height of the transducer produces what pressure difference?
A 20 cm difference in height produces a 15 mmHg difference in pressure.
- high-low
- low-high
The complication risk for radial art lines is overall low. What things increase the risk for complications?
- Vasospastic arterial disease
- Previous arterial injury
- Thrombocytosis
- Protracted shock
- High-dose vasopressor administration
- Prolonged cannulation
- Infection
What is the most common site for invasive blood pressure monitoring?
Radial artery
Where should the arterial line be calibrated?
At the level of the heart (mid-axillary line/right atrium or meatus of ear/circle of willis if concered about cerebral perfusion in sitting patient)
What part of the ECG does the upstroke of an arterial waveform follow?
The R wave
What part of the cardiac cycle is represented by the dicrotic notch on the arterial waveform?
Closure of the aortic valve during ventricular diastole
How is the systemic arterial pressure waveform of an A-line produced?
It results from the ejection of blood from the left ventricle into the aorta during systole, followed by peripheral runoff during diastole
Describe the technique of the Allen test?
Compress both the radial and ulnar arteries and ask the patient to make a tight fist, exsanguinating the palm. The patient then opens the hand, avoiding hyperextension of the wrist or fingers. As occlusion of the ulnar artery is released, the color of the open palm is observed.
Color should return to palm within several seconds if normal.
Severely reduced ulnar collateral flow is present when the palm remains pale for more than 6 to 10 seconds
Purpose of EKG
- Detect arrhythmias
- Monitor HR
- Detect ischemia (3 lead detects HR but not ischemia…must be able to see leads II and V5)
- Detect electrolyte changes
- Monitor pacemake function
What are methods of non-invasive blood pressure measurement and describe them.
- Palpation
- palpating return of arterial pulse while an occluded cuff is deflated
- underestimates systolic pressure and measures only SBP, but is simple and inexpensive
- Doppler
- base on shift in frequency of sound waves that is reflected by RBC’s moving through an artery
- measures only SBP reliably
- Auscultation
- using a sphygmomanometer, cuff, and stethoscope. korotkoff sounds due to turbulent flow within an artery created by mechanical deformation from BP cuff
- permits estimation of SBP and DBP
- unreliable in HTN patients (usually lower)
- Oscillometry
- senses oscillations/fluctuations in cuff pressure produced by arterial pulsations while deflating a BP cuff
- 1st oscillation correlates with SBP
- Maximal degree of detectable pulsation is determined to be the MAP
- oscillations cease at DBP
- Automated cuffs work by this mechanism–measure changes in oscillatory amplitude electronically, derives MAP, SBP, DBP by using algorithms
- Continuous NIBP finger readings
- subject to significant limitations
Describe a well-fitted NIBP cuff
- Bladder width is approximately 40% of the circumference of the extremity
- Bladder length should be sufficient to encircle at least 80% of the extremity
- Applied snugly, with bladder centered over the artery and residual air removed
Describe precordial and esophageal stethoscope
- Minimally invasive, cost-effective continuous monitor
- Continual assessment of breath sounds and heart tones
- Precordial placed on chest surface
- Esophageal placed 28-30 cm into esophagus
- Very sensitive monitor for bronchospasm, airway obstruction, changes in HR/rhythm
Overdamped arterial waveform
- loose connections
- air bubbles
- kinks
- blood clots
- arterial spasm
- narrow tubing
Underdamped arterial waveform
- catheter whip or artifact
- stiff, non-compliant tubing
- hypothermia
- tachycardia or dysrhythmia
Describe pulse oximeter method of measurement
- non-invasive
- relates transmission of light through a solution to the concentration of the solute in the solution (application of Beer-Lambert Law)
- typically uses 660 and 940 nm wavelength of light
- pulse ox probe is composed of a light emitter and a photodetector
Pulse oximeter uses and sites
- Detection of hypoxemia
- Detection of perfusion
Sites: fingers, toes, nose, ear, tongue, cheek
Pulse ox inaccuracies
- malposition of probe
- dark nail polish
- different hemoglobin
- dyes
- electrical interference
- shivering
