NU 428 Hemodynamic Monitoring
What is hemodynamics and some principles of monitoring hemodynamics?
Interrelationships of dynamic forces that affect blood circulation
Hemodynamic monitoring allows us to tell when the pt is going into distress before they actually get there. They represent how much circulatory volume is there, can tell us whether it’s too low or too high.
1) You must look at the whole picture. Can’t just look at the monitor. Can’t just look at the pt. Must look at both, but the pt and your assessment skills are MOST important, take priority. Assess pt first, then worry about the lines.
2) Must look at trends. Can’t just look at one number from the machine at one time and diagnose them.
3) For arterial lines, keep them sterile, and be anal about sterile technique in every area! High risk of infections with arterial lines in major vessels. Will cause the infection to be a systemic infection if it gets in.
What is cardiac output? What is systemic vascular resistance? Why do they matter?
Cardiac output: CO
- Volume of blood ejected from heart/min
- 4 to 8 L/min
- Cardiac index (CI)
- CO adjusted for body size
Systemic vascular resistance: SVR
- Peripheral vascular resistance
- Diameter of blood vessels
- SVR tells us whether or not the vessels are open or resistant.
Arterial BP = CO x SVR
What is preload? How does it affect the heart? What is afterload? What is contractility?
Muscle fiber stretch before systole
Determined by left ventricular end diastolic volume (LVEDV) and left ventricular end diastolic pressure (LVEDP).
Too much preload will stretch the fibers too much and make the heart boggy. Increased stretch means increase in volume. Preload occurs during diastole.
- Increased stretch = increased volume
- Stretch is within physiologic limits
Pressure or resistance against flow
Related to lumen size and viscosity
(MAP-RAP)/CO x 80
Like "opening a door against the wind.
Force of ventricular contraction
Affects stroke volume. Shows how the heart is functioning. If contractility is good, stroke volume will be good.
Don’t want it to be too hard, the heart will work harder and need more oxygenation. Cause hypoxia, chest pain.
Why do we use continuous arterial pressure monitoring? What does it monitor? How does it work? What is a diagnostic test that ensures adequate arterial flow in the radial and ulnar arteries of the hands?
Monitor BP through arterial line
Frequent ABG sampling
Normal Mean Arterial Pressure (MAP): 70-105
A 20-gauge, 2-inch catheter cannulates a peripheral artery (e.g., radial, femoral) & sutured—connected to pressurized tubing to monitor (reading of pressure given)
Great way to get ABGs, get a constant more accurate BP, gives MAP
The cannula, enters the radial artery and is connected via pressure (nondistensible) tubing to the transducer.
- The transducer converts the pressure wave into an electronic signal.
- The transducer is wired to the electronic monitoring system, which amplifies, conditions, displays, and records the signal.
- Stopcocks are inserted into the line for specimen withdrawal and for referencing and zero-balancing procedures.
- A flush system, consisting of a pressurized bag of intravenous fluid, tubing, and a flush device, is inserted into the line.
- Continuous slow (approx 3 mL/hr) flushing and provides a mechanism for fast flushing of lines.
- The stopcock nearest the transducer is usually the zero (calibrated) reference for the transducer.
- Open the reference stopcock to room air (off to the patient) and observe the monitor for a reading of zero.
- This allows the monitor to use the atmospheric pressure as a reference for zero.
- Then flush the line. Must do this re-calibration regularly every 4, 8, or 12 hours.
Allen's Test - clamp off both the ulnar and radial arteries, then unclamp the ulnar. Watch for redness, flushing of the hand as blood flow re-perfuses the tissue.
What position does the transducer of the arterial line stay in? How does a nurse determine where the transducer must be placed? When must you zero the line?
*Picture for reference on slide 10
The transducer must stay on the 4th intercostal space. If you move the pt, you must move the transducer back to the right spot. Some nurses mark it with a marker, some tape it, some eyeball it using a pole to measure.
If you have the transducer too high, you’ll have a false low reading.
A. Phlebostatic axis is an external landmark used to identify the level of the atria in the supine patient.
- The phlebostatic axis is defined as the intersection of two imaginary lines: one drawn vertically through the fourth intercostal space at the sternum,
- one drawn horizontally through the midchest, halfway between the outermost anterior and outermost posterior points of the chest.
B, As the backrest of the supine patient is elevated, the phlebostatic axis remains at the same anatomic location, becoming progressively elevated from the floor.
- The zero reference point must be repositioned with changes in backrest elevation, to keep it at the phlebostatic level.
- Initial setup of arterial line
- After insertion of arterial line
- Cable disconnections
- Accuracy is questioned
What is the square wave test? When do you perform it?
Square wave test - Optimizes dynamic response (equipment reproduces, without distortion, a signal that changes rapidly)
Perform dynamic response test (square wave test) every 8 to 12 hours, when system opened to air, when accuracy questioned. Just flushing the line basically.
Also, regularly check the blood flow to the distal site in anyone w/ an A-line.
What are the principles of arterial pressure monitoring?
Set high/low alarms based on patient condition
Get your readings during expiration! Inspiration causes increased pressure, increased blood flow.
Simultaneously recorded electrocardiogram (ECG) tracing.
Systemic arterial pressure tracing:
- Systolic pressure is the peak pressure.
- Dicrotic notch indicates aortic valve closure.
- Diastolic pressure is the lowest value before contraction.
- Mean pressure is the average pressure over time calculated by the monitoring equipment.
*Picture on slide 14 for reference
What are some complications of arterial lines?
- is most likely to occur when the catheter dislodges or the line loosens/disconnects.
- To avoid use Luer-Lok connections, always check the arterial waveform, activate alarms.
- If you have a pt with an A-line, keep the line above the covers where it can be seen, you can tell if they’re bleeding.
- Continuous flush irrigation system delivers 3 - 6 mL/h of saline (possibly heparinized)
- Maintains line patency & limits thrombus formation
- Keep the line patent to prevent thrombus formation. Flush the line every 8 or so hours.
4) Neurovascular impairment
- Assess neurovascular status distal to arterial insertion site hourly.
- Compromised arterial flow: cool, pale, with capillary refill >3 seconds.
- If you don’t have blood flow to the distal site, it can cause a lot of problems. Do your checks! Symptoms of neurologic impairment (e.g., paresthesia, pain, paralysis) may be noted.
- Might lead to loss of limb
What does a pulmonary artery (PA) catheter measure?
PA line AKA Swan Ganz line helps to detect left sided heart function.
Reflects left ventricular pressures which reflects the amount of VOLUME in the body.
Placement: Jugular, femoral, subclavian. If the wave patterns are not looking right for the pulmonary catheter, you can get an x-ray to confirm placement.
Measures pressure, flow & O2. Mainly measures VOLUME.
Central venous pressure (CVP):
- RV preload or RV end-diastolic pressure under normal conditions, measured in RA (w/PA cath prox. lumen) or in vena cava (w/central line) close to heart
- Elevated CVP indicates RV failure or volume overload. Would probably see JVD. Low CVP indicates hypovolemia (dehydration, OD on diuretics).
Cardiac output (CO)/cardiac index (CI):
- Volume of blood pumped by heart in 1 minute (SVxHR)
- CI: CO adjusted for body size (more precise)
- Frank-Starling law (explains preload): the more a myocardial fiber is stretched during filling, the more it shortens during systole and the greater the force of the contraction.
- As preload increases, force generated in the subsequent contraction (contractility) increases, thus SV and CO increase (increases O2 requirements)
- Positive inotropes improve/increase contractility: Epinephrine, norepinephrine (Levophed), isoproterenol (Isuprel), dopamine (Intropin), dobutamine (Dobutrex), digitalis-like drugs, calcium, and milrinone. Increase output for the pt
- Negative inotropes: alcohol, calcium channel blockers, β-adrenergic blockers and clinical conditions (e.g., acidosis). Decrease contractility
Stroke volume (SV)/SV index (SVI):
- Volume ejected with each heartbeat (determined by preload, afterload & contractility)
- SVI: SV adjusted for body size
Pulmonary artery diastolic (PAD, Normal: 5-15), pulmonary artery systolic (PAS, Normal: 15-30), and pulmonary artery wedge (PAWP, Normal: 4-12) pressures:
- Indicators of cardiac function and fluid volume status.
- The most significant thing you can find from a hemodynamic line (especially a pulmonary artery catheter) is about circulatory volume. TEST QUESTION.
- PAWP: measurement of p
Why do we use PA pressure monitoring? What is the RA port used for?
Guides management of complicated CV, pulmonary, and volume conditions.
RA port (CVP measuring port):
- Measures central venous pressure
- Injection of fluid for CO measurement
- Blood sampling
What is the second proximal port used for? What about the thermistor lumen port (the distal tip)? Why is the multiple lumen style convenient for administering medications?
Second proximal port
- Infusion of fluids and drugs
- Blood sampling
Thermistor lumen port distal tip (PA) is used for core temperature
Lumens empty into different areas of the heart; therefore, you can put two incompatible medicines in two different ports at the same time.
Why would a nurse inflate the balloon on the PA catheter? Do you leave the balloon inflated/wedged? Why?
Inflate to “float” the balloon. Don’t want to inflate the balloon unless necessary. It could be inflated to allow placement of the catheter in order to get a pulmonary artery wedge pressure. Looks at left ventricular pressure.
PAWP: inflate balloon with enough air (1.5 max) until PA waveform changes to a PAWP waveform
The balloon is inflated while the bedside monitor is observed for changes in the waveform. *Slide 30 for wave changes*
Inflate no more than 8 - 15 seconds
DO NOT LEAVE THE BALLOON WEDGED. It’ll infarct the whole lung. We don’t do a lot of wedge pressures anymore because of the risks associated.
Why do we need to know PAD and PAWP?
PAD and PAWP decrease with volume depletion. Fluid therapy based on PA pressure can restore fluid balance while avoiding over/undercorrection of the problem.
Monitoring PA pressures allows therapeutic manipulation of preload.
How can a nurse measure CO with a PA catheter?
Intermittent bolus thermodilution is the method used to get continuous cardiac output:
- Fixed volume (5 to 10 mL) of room temperature or cold NS or D5w injected rapidly (≤4 seconds) and smoothly into the proximal lumen port of the PA catheter
- Repeat this procedure 3 times, with measurements 1 to 2 minutes apart.
- CO is calculated from the temp. change in the PA when a fixed volume at known temperature of a solution is injected into the proximal port in the RA
- Must have patient’s weight in the machine to get an index number.
SVR, SVRI, SV, and SVI can be calculated when CO is measured.
What are the physical symptoms that accompany elevated and decreased SVR? What is the SVR normal range?
- Vasoconstriction (shock)
- ↑ Vasoactive inotropes (Dopamine, Levophed)
- LV failure
- Extreme vasodilation
- Cardiac tamponade
What are some complications with PA catheters?
Infection and sepsis
- Culture tip
- Sterile insertion and maintenance: Cleanse w/ chlorhexidine preparation & Cover w/sterile occlusive dressing q96h
- Also with Insertion and Removal or if tip migrates back to right ventricle
Air embolus (e.g., disconnection)
- Check balloon integrity before insertion, rupture, or injection of air into any of the lumina, can cause an air embolus
PA catheter cannot be wedged
- May need to be pulled back
- Pulmonary infarction or PA rupture balloon rupture, prolonged inflation, spontaneous wedging
- Never inflate the balloon beyond the balloon’s capacity (1 to 1.5 mL of air)
- Check PA pressure waveforms often for signs of catheter occlusion, dislocation, or spontaneous wedging.
- Will be put on heparin if one forms
What tool is used for noninvasive arterial oxygenation monitoring?
Pulse oximetry: SpO2
- May ↓ frequency of ABG sampling
- Normally 95% to 100%
- Difficult w/ hypothermia, vasopressors, or hypoperfusion.
- Alternate locations: forehead, earlobe, toes
What are the benefits of circulatory assist devices (CADs)? What are the two types of CADs?
Decrease cardiac workload
Support while recovering from injury
Can keep someone alive while they’re recovering from an injury like an MI, massive heart failure, trauma, or waiting for a transplant. Just buying time for either the heart to heal or a transplant.
1) IABP – only at the hospital
2) VAD – can be portable
How does an intraaortic balloon pump work? What are the benefits of using an IABP? What should a nurse know about management of a patient with an IABP?
Temporary circulatory assistance: Usually 2-3 days
- ↓ afterload
- Augments aortic diastolic pressure
- Helps with diastolic filling, pushes blood into the coronary arteries.
Counterpulsation: Timing of balloon inflation is opposite to ventricular contraction.
Has to be deflated during systole, inflated during diastole.
Must be a Registered Nurse and trained/certified in IABP care.
Balloon is filled with helium or CO2, if ruptures, will dissolve in the bloodstream.
The balloon is inserted percutaneously through R or L femoral artery, advanced toward the heart, and positioned in the descending thoracic aorta below the left subclavian artery and above the renal arteries. Therefore, you must check the left radial pulse AND urine output.
Inflation timing is coordinated with EKG.
A. During systole the balloon is deflated, which facilitates ejection of the blood into the periphery.
B. In early diastole, the balloon begins to inflate. “Dilated Balloon=Diastole!”
C. In late diastole, the balloon is totally inflated, augments aortic pressure and increases the coronary perfusion pressure with the end result of increased coronary and cerebral blood flow.
The IAPB assist ratio is 1:1 in the acute phase of treatment, there is one IABP cycle of inflation and deflation for every heartbeat.
What are some nursing considerations for a patient on an IABP?
The patient’s HOB can only be 15-30 degrees, no more. Must be supine or side-lying. It’s so the balloon won’t be pushed up into the heart near the subclavian artery. Will cause perfusion problems to the head.
Always check urine output. If it slips downward, the pt will probably have flank pain which will precede low urine output.
Always check pulses distal to the site. Do neurovascular checks.
They’ll be on a heparin drip to prevent thrombus.
Also be on a PA catheter and A-line. Usually try to keep BP on low side to help prevent bleeding and help the coronary arteries to be as perfused as possible.
Watch for bleeding at the site. Don’t just look at the cath site, palpate one inch around the site to check for hematoma.
Reiterate to the pt and family that they cannot sit up or bend legs.
Going to do BPs q15 min.
What are some complications of IAPB therapy?
Vascular injury - Aortic dissection:
- Acute back, retroperitoneal, testicular or chest pain
- Decreased pulses, high HR, low CO
- Low H&H
- Variations in BP b/t arms
Thrombus and embolus formation - dislodging of plaque
Improper timing of balloon inflation
Peripheral nerve damage - compromised distal circulation, happens particularly when a cutdown is performed for insertion.
Improper timing of inflation will cause increased afterload, decreased CO, myocardial ischemia, increased O2 demand.
Mesenteric / renal ischemia
How is a patient weaned from an IABP?
Decrease ratio of IABP-assisted beats to unassisted beats.
Starts at 1:1, goes to 1:2, then 1:3.
- HR <110
- No arrhythmias
- MAP>70, PAWP<18, C.I.>2.5
- Cap refill <2 sec
- U/O >30 ml/hr
When removed, pressure to site like sheath being removed in a cardiac cath
How does a ventricular assist device (VAD) work? When is it indicated?
Short and longer-term support
Greater mobility than IABP
Augment or replace action of ventricle
Implanted vs. external
A typical VAD shunts blood from the left atrium or ventricle to the device and then to the aorta.
- Failure to wean from bypass
- Postcardiotomy shock
- Bridge to recovery or transplant
- NYHA class IV failed Rx
What are the principles of nursing management for a patient with a VAD?
Similar to IABP
- Observe for bleeding, tamponade, HF, infection, dysrhythmias, renal failure, hemolysis, and thromboembolism.
- Recovery through ventricular improvement