Hemodynamic monitoring Flashcards
What are 5 purposes of hemodynamic monitoring?
- Assess hemostasis, trends
- Observe for adverse reactions
- Assess therapeutic interventions
- Manage anesthetic depth
- Evaluate equipment function
What needs to be continually monitored during anesthesia?
Oxygenation, ventilation, circulation, temperature
What monitors must be used under minimal standards?
- Electrocardiogram (HR and rhythm)
- Blood Pressure
- Precordial stethoscope
- Pulse oximetry
- Oxygen analyzer
- End tidal carbon dioxide
What minimal monitoring information must be on graphic display?
- Electrocardiogram
- Blood Pressure
- Heart rate
- Ventilation status
- Oxygen saturation
What are three basic monitoring techniques?
- Inspection
- Auscultation
- Palpation
What are 5 considerations when choosing hemodynamic monitoring techniques?
- Indications/contraindications
- Risk/benefit
- Techniques/alternatives
- Complications
- Cost
Describe the purpose/use of a precordial stethoscope.
- Used for continual assessment of breath sounds and heart tones
- Esophageal use in intubated pts (only 28-30 cms into the esophagus)
- Very sensitive monitor for bronchospasm and changes in pediatric patients
When does a patient have to have ECG monitoring?
Continuously from the beginning of anesthesia until leaving anesthesia location
What is the purpose of ecg monitoring?
- Record electrical activity of the heart
- Detect arrhythmias
- Monitor heart rate
- Detect ischemia
- Detect electrolyte changes
- Monitor pacemaker function
Describe the difference between 3 lead and 5 lead ECGs.
3 Lead:
- Elecrodes RA, LA, LL
- Leads I,II, III
- 3 views of the heart
5 lead:
- Electrodes RA, LA, LL, RL and chest lead
- Leads I, II, III, aVR, aVL, aVF, V lead
- 7 views of heart
What should the gain of an ECG be set at?
Gain should be set at standardization
- 1 mV signal produces 10mm calibration pulse
- a 1 mm ST segment change is accurately assessed
What should the filtering capacity be set to on an ECG?
Filtering capactiy should be set to diagnostic mode.
-Filtering out the low end of the frequency bandwith can distort ST segment
What are the 5 principle indicators of acute ischemia on an ECG?
- ST segment elevation ≥ 1mm
- T wave inversion
- Development of Q waves
- ST segment depression, flat or downslope of ≥1mm
- Peaked T waves
What leads would you see changes in with posterior/inferior wall ischemia (right coronary artery)?
Leads II, III, AVF
What leads would you see changes in with lateral wall ischemia (circumflex branch of left coronary artery)?
Leads I, AVL, V5-6
What leads would you see changes in with anterior wall ischemia (left coronary artery)?
Leads I, AVL, V1-V4.
What leads would you see changes in with anterioseptal ischemia (left descending coronary artery).
Leads V1-V4
What do changes in systolic/diastolic blood pressure correlate with?
Changes in SBP correlate with changes in myocardial O2 requirements. Changes in DBP reflect coronary perfusion pressure
What changes occur to the pulse pressure and SBP as a pulse moves peripherally?
As a pulse moves peripherally wave reflection distorts the pressure waveform-exaggerated SBP and wider pulse pressure.
What are 4 ways to non-invasively measure blood pressure?
- Palpation-palpating the return of arterial pulse while on occuluded cuff is deflated
- underestimates systolic pressure, measures only SBP - Doppler- based on shift in frequency of sound waves that is reflected by RBCs moving through an artery
- measures only SBP reliably - Auscultation-using a sphygmomanometer, cuff, and stehoscope. 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. The first oscillation correlates with SBP, maximum/peak oscillations occur at MAP, oscillations cease at DBP. This is how automated cuffs work.
Describe the sizing and positioning of a BP cuff.
- Bladder width 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
What can cause false high BP measurements with a BP cuff?
- Cuff too small
- Cuff too loose
- Extremity below level of heart
- Arterial stiffness- HTN, PVD
What can cause false low BP measurements with a BP cuff?
- Cuff too large
- Extremity above level of heart
- Poor tissure perfusion
- Too quick deflation
What are some complications associated with non-invasive blood pressure measurement?
- Edema of extremity
- Petechiae/bruising
- Ulnar neuropathy
- Interference of IV flow
- Altered timing of IV drug administration
- Pain
- Compartment syndrome
Describe invasive blood pressure measurement.
- Involves percutaneous insertion of a catheter into an artery which is then transduced to convert the generated pressure into an electrical signal to provide a waveform.
- Generates real-time beat to beat BP
- Allows access for arterial blood samples
- Measurement of CO/CI/SVR
- Small catheter
- Sites of insertion include radial, ulnar, brachial, femoral, dorsalis pedis, axillary
- Transducer system-continuous flush device. 1-3 ml/hr of NS prevents thrombus formation, allows rapid flushing
- System dynamics and accuracy improved by minimizing tube length, limit stop cocks, no air bubbles, the mass of fluid is small, using non compliant stiff tubing, and calibration at level of heart
What are the indications for invasive blood pressure measurement?
- Elective deliberate hypotension
- Wide swings in intra-op BP
- Risk of rapid changes in BP
- Rapid fluid shifts
- Titration of vasoactive drugs
- End organ disease
- Repeated blood pressure sampling
- Failure of indirect BP measurement
Describe leveling an A-line.
- Mid axillary line in supine patients (right atrium)
- Level of the ear (circle of willis) in sitting pts
What does the rate of upstroke indicate on an arterial waveform?
Contractility
What does the rate of downstroke indicate on an arterial waveform?
SVR
What is the effect of hypovolemia on the arterial waveform?
Exaggerated variations in size with respirations.
How to you determine the MAP from an arterial waveform?
Area under the curve.
What does the dicrotic notch indicate on the arterial waveform?
Closure of the aortic valve
How does the BP waveform change as it travels through the arterial tree to the periphery.
Distal pulse amplification
- SBP increases
- DBP wave decreases
- MAP not altered
- Dicrotic notch becomes less and appears later
What are some complications associated with invasive blood pressure measurement?
- Nerve Damage
- Hemorrhage/Hematoma
- Infection
- Thrombosis
- Air embolus
- Skin necrosis
- Loss of digits
- Vasospasm
- Arterial aneursym
- Retained guidewire
What are the indications for central venous catheters?
- Measuring right heart filling pressure
- Assess fluid status/blood volume
- Rapid administration of fluids
- Administration of vasoactive drugs
- Removal of air emboli
- Insertion of transvenous pacing leads
- Vascular access
- Sample central venous blood
- Pulmonary artery catheters
What are the possible insertion sites for central venous catheters?
- Right internal jugular
- Left internal jugular
- Subclavian veins
- External jugular veins
- Femoral veins
What is the most common size for a central venous catheter?
7 french, 20cm
Where is the ideal placement for the tip of the central venous catheter?
Within the SVC just above the junction of venae cavae and the RA, parallel to vessel walls, positioned below the inferior border of the clavical and above the level of the 3rd rib, the T4/T5 interspace, the carina, or takeoff right main bronchus
What are contraindications for central venous catheters?
- Right atrial tumor
- Infection at site
What are some risks associated with central venous catheters?
- Air or thrombo-embolism
- Dysrhythmia
- Hematoma
- Carotid puncture
- Pneumo/hemothorax
- Vascular damage
- Cardiac tamponade
- Cardiac tamponade
- Infection
- Guidewire embolism
What are normal CVP values in a spontaneous breathing patient? During mechanical ventilation?
1-7 mmHg in spontaneous breathing, rises 3-5 mmHg during mechanical ventilation
What is CVP an indication of?
Right atrial pressure/Right ventricle preload
What part of the CVP waveform should the measurement be taken?
The peak of the “a” wave. This coincides with the point of maximal filling of the right ventricle. This is used for measurement of right ventricle end diastolic pressure. Should be measured at end-expiration
What are the peaks of the CVP waveform? Descents?
Peaks: a, c, v
Descents: x, y
Describe the a wave of the CVP waveform
- Due to contraction of the right atrium which results in increases pressure in the atrium
- Follows the P-wave on the EKG
- End diastole
- Corresponds with “atrial kick” which causes filling of the right ventricle
Describe the c wave of the CVP waveform.
- Due to right ventricular contraction
- Due to closure of the tricuspid valve and isovolemic ventricular contration
- Results in the tricuspid valve “bulging” back into the atrium
- Occurs in early
Describe the x descent of the CVP waveform
- Atrial pressure continues to decline during ventricular contraction due to atrial relaxation
- Mid-systolic event
Describe the v wave of the CVP waveform.
- Reflects venous return against a closed tricuspid valve (which encompasses a portion of RV systole
- Occurs late in systole with the tricuspid still closed
- Occurs just after the T-wave on EKG
Describe the y descent of the CVP waveform
- After ventricular relaxation, the tricuspid valve opens due to the venous pressure, and blood flows from the atrium into the ventricle
- the y descent is the fall in atrial pressure following opening of the tricuspid valve
- “diastolic collapse in atrial pressure”
What is pulmonary artery pressure monitoring used to measure?
- Intracardiac pressure (CVP, PAP, PCWP)
- Estimate LV filling pressures
- Asess LV function
- CO
- Mixed venous oxygen saturation
- PVR and SVR
Physically describe the pulmonary artery catheter.
- 7 or 9 french
- 110 cm length marked at 10 cm intervals
- 4 lumens: distal port PAP, second port 30cm more proximal CVP, third lumen balloon, fourth wires for thermister
What are the indications for pulmonary artery catheter monitoring?
- LV dysfunction
- Valvular disease
- Pulmonary HTN
- CAD
- ARDS/respiratory failure
- Shock/sepsis
- ARF
- Surgical procedure: cardiac, aortic, OB
What are some complications associated with pulmonary artery catheters?
- Arrhythmias
- Catheter knotting
- Balloon rupture
- Thromboembolism
- Air embolism
- Pneumothorax
- Pulmonary infarction
- PA rupture
- Infection (endocarditis)
- Damage to cardiac structures (valves, etc)
- Relative contraindications: WPW syndrome, complete LBBB
What is the distance from the R internal jugular vein to the vena cava and RA junction.
15 cm
What is the distance from the R internal jugular vein to the right atrium
15-25 cm
What is the distance from the R internal jugular to the right ventricle?
25-35 cm
What is the distance from the R internal jugular to the pulmonary artery?
35-45 cm
What is the distance from the R internal jugular to the PA wedge measurement?
40-50cm
What does the a wave represent on the PA catheter waveform?
Contraction of the left atrium.
What does the c wave represent on the PA catheter waveform?
A 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.
What does the v wave represent on the PA catheter waveform? What does a prominent v wave represent?
Blood entering the left atrium during late systole. Prominent v waves reflect mitral insufficiency causing large amounts of blood to reflux into the left atrium during systole.
What are some methods of cardiac output monitoring?
- Thermodilution
- Continuous thermodilution
- Mixed venous oximetry
- Ultrasound
- Pulse contour
What is the normal range for cardiac output?
4-6.5 L/min
What is the normal range for stroke volume?
60-90 ml
What is normal SVR?
800-1600 dynes-sec/cm^5
What is normal PVR?
40-180 dynes-sec/cm^5
What is normal arterial oxygen content?
16-20 mL/dL
What is normal mixed venous oxygen content?
13-15 mL/dL
What is normal mixed venous oxygen saturation?
70-80%
What is normal arteriovenous oxygen difference?
3-5 mL/dL
What is normal oxygen consumption?
200-250 mL/min
What factors can cause loss of the a wave on the PA catheter waveform?
- A fib
- Ventricular pacing
What factors can cause giant a waves or “cannon” a waves?
- Junctional rhythms
- Complete HB
- Mitral stenosis
- Diastolic dysfunction
- Myocardial ischemia
- Ventricular hypertrophy
What factors can cause large v waves on the PA catheter waveform?
- Mitral regurgitation
- Acute increase in intravascular volume
What 7 parameters are observed during transesophageal electrocardiography?
- 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
What are some cases where transesophageal electrocardiography is used?
- Unusual causes of acute hypotension
- Pericardial tamponade
- Pulmonary embolism
- Aortic dissection
- Myocardial ischemia
- Valvular dysfunction
What are some complications of transesophageal electrocardiography?
- Esophageal trauma
- Dysrhythmias
- Hoarsness
- Dysphagia
- Most complications are in awake patients
