Mod 11 Hemodynamics Flashcards
What factors can affect/determine hemodynamic stability?
- Cardiac contractility
- Blood Volume
- Vascular smooth muscle tone
What is hemodynamics and why it important to monitor?
The study of the forces (pressures) within the vascular system that influence the circulation of blood
- can help guide drug interventions
- Valuable for assessment of cardiovascular function and adequacy of intravascular fluid volume
What are 3 laws about liquids and pressures in a container?
- Liquids are essentially not compressible
- Pressure varies with vertical position (container)
- The pressure is the same @ all points @ the same level within that liquid (pascal law)
How does Pascals Principle apply to Hemodynamic monitoring?
Changes in pressure are transmitted from catheter to the transducer via the fluid filled IV line
- Recall: Changes in pressure in a enclosed space is transmitted undiminished to every portion of the vessel
What are 2 considerations that should be done/kept in mind when managing Pressure Transducing Systems?
- Level
- Zeroing
What is leveling mean in the context of pressure transducing systems?
The process of placing the transducer at the same level as the phlebostatic axis
- AKA the mid-axillary line and 4th rib which approximates the right atrium
What does a Transducer do in a Pressure Transducing System?
Transducers changes the mechanical signal to an electronic signal
(Pressure -> # on monitor)
- It is a strain gage basically
What happens to the transducer as pressure is applied to the diaphragm?
- The strain gauge wire is lengthened, changing resistance
- This changes the electrical current flowing through the wire
- This electrical current is interpreted by a computer as a proportional change in pressure
- The computer will display a numeric pressure value or waveform
What is the pressure bag inflated to on a Pressure Induced System?
300mmHg
What is the placement of a Transducer on a Pressure Transducing System?
***Insert image from slide 10
Upside down w/cable feeding to bottom by convention (doesn’t affect function)
What does “zeroing” entail for a Pressure Transducing System?
- Steps?
- when is it done?
- Turn the stopcock (closest to transducer) off to the patient and open to atm pressure
- Wait for equilibration and zero the monitor (few secs)
- Is done at set up and at the start of each shift (or troubleshooting)
When are Pressure Transducing Systems “zeroed”?
- Setup
- Start of shift
- Troubleshooting
What is the most frequently measured hemodynamic parameter?
Arterial pressure
Methods of arterial pressure assessment?
- Direct (invasive) via indwelling arterial catheter
- Blood pressure cuff (non-invasive)
- Doppler method aka ultrasound (non-invasive)
Indications for continuous arterial monitoring? (4)
- Hypotension/Hypertension
- Frequent need for ABG/blood work
- Pt requiring inotropic support
- Pt receiving vasoactive drugs
What are 3 complications of indwelling catheters that need monitoring?
- What are the general associated causes/risks?
- Infection (sterility)
- Hemorrhage (bleed or hematoma = decreased clotting)
- Ischemia (embolus/thrombus could occur)
What does a arterial pressure waveform indicate when the diacrotic notch is not visible?
Pressure tracing is dampened and may be inaccurate (numbers are lower than the pts actual)
What pressures would reflect a dampened pressure tracing?
Diacrotic notch not visible w/a systolic P < 50-60 mmHg
Why could arterial pressure waveforms form a higher point than the actual pressure in the volume displacement phase?
An increase of circulating catecholamines can make the inotropic phase steeper
Where does CVP need to be “zeroed”?
Level of right arium aka phlebostatic axis
What is CVP?
- normal?
- reflects what value?
CVP is the pressure of the blood in the right atrium or vena cava during diastole
- Normal < 6mmHg
- Reflects preload of RV
What are the indications for CVP? (2)
- Assess circulating blood volume
- Assess RV function
What can the CVP line be used for aside from monitoring? (5)
- Rapid infusion of fluid/blood/drugs
- Blood samples
- Parenteral nutrition
- Poor peripheral access
- Temp cardiac pacemakers, hemodialysis catheters
What are 3 factors that are generally used to assess CVP?
- Blood volume
- Cardiac filling
- Venous Return
What are common routes of access for CVP lines?
- Jugular vein (low risk of pneumothorax)
- Subclavian vein (higher risk of pneumothorax)
CxRs needed for placement of both
What factors can skew values in hemodynamic monitoring?
- Kinking, breakage, accidental removal
- Site compcliations aka bleeding risk
- pressure waveform dampening (pt needs to be supine)
What are rare site of access for CVP lines?
Femoral vein
- easy to place w/low risk of complications
- less reliable bc catheter tip is far from Rt atrium
CVP Risks and complications
- pain
- infection
- bleeding
- air embolism
- thrombus
- pneumothorax (site dependent)
CVP placement? (2)
Venacava or right atrium
How do Respiratory variations affect CVP waveforms?
- when should they be recorded?
CVP should be recorded @end expiration
- Breathing makes readings inaccurate
How does spontaneous breathing affect CVP?
Inspiration causes a decrease in CVP
How does PPV affect CVP?
PPV causes an increase in CVP
What if there are no respiratory varitions (pt not breath holding)?
Check for kink/air in tubing, stopcock error, small clot or kink in the catheter
What are Pulmonary Artery Catheters (PAC) used for?
- CO (thermodilution)
- Route for mixed venous sampling (SvO2) or C(a-v)O2
- Admin of drugs
- Pacing
What values do Pulmonary Artery Catheters (PAC) use?
- CVP
- PAP
- PAWP
- PVR and SVR
What is PAP?
volume ejected by RV and resistance of flow through pulmonary vasculature
How is PVR measured?
Mean PAP and PCWP
How is SVR measured?
Systemic arterial pressure and PA end diastolic pressure
What is C(a-v)O2 used for?
Can assess (L->R) shunt by measuring CVP and PA distal
What are complications associated with Pulmonary Artery Catheters (PAC)
- Same as CVP line problems
- Catheter irritations can cause dysrhythmias
- Perforation of the heart and pulmonary artery
- Pulmonary rupture by overfilling balloon
What dysrhythmias can be caused by PAC?
bundle branch blocks. SVT, or ventricular dysthymia if pt is acidotic or hypoxemic
Where does the proximal and distal openings of the PAC catheters rest?
- Proxima lumen opening rests in the RA (CVP measurement)
- Distal lumen opening rests in the PA
What do the Proximal ports of PAC catheters do?
- blood samples
- inject drugs
- thermal bolus
What do the Distal ports of PAC catheters do?
- Measure PAP
- Measure PCWP
- Mixed venous samples
What are:
- Normal Right atrium pressures
- Normal Right ventricle Pressures
- Normal Pulmonary Artery Pressures
- Normal PAWP?
What does PCWP assess/reflect?
Represents left atrial pressure. used to assess:
- LV filling
- Mitral valve fuction
Tricuspid valve vs Mitral valve locations?
Tricuspid = Right
Mitral = Left
For PCWP to reflect left atrial pressures, what conditions need to be met?
Blood flow must be uninterrupted between the catheter tip and the left heart - this condition only exists in west Zone III
Need to add slides 31-34***