Ch. 13 Part 2 Flashcards
follows a spectrum of very invasive, moderately invasive, minimally invasive, and noninvasive methods
In general, cardiovascular surgical units use more invasive hemodynamic monitoring, whereas nonsurgical critical care areas begin with less-invasive monitoring, adding invasive technologies based on the patient’s physiologic requirements.
Hemodynamic Monitoring Equipment
Intraarterial Blood Pressure Monitoring
Central Venous Pressure Monitoring
Pulmonary Artery Pressure Monitoring
Continuous Monitoring of Mixed Venous and Central Venous Oxygen Saturation
Hemodynamic Monitoring
four component parts:
Heparin
Calibration of Hemodynamic Monitoring Equipment
Zeroing the Transducer
Midaxillary Line (Phlebostatic Axis)
Leveling the Transducer
Head of Bed Backrest Position
Lateral Position
Hemodynamic Monitoring Equipment
- An invasive catheter and high-pressure tubing connect the patient to the transducer.
- The transducer receives the physiologic signal from the catheter and tubing and converts it into electrical energy.
- The flush system maintains patency of the fluid-filled system and catheter.
- The bedside monitor contains the amplifier with recorder, which increases the volume of the electrical signal and displays it on an oscilloscope and on a digital scale in millimeters of mercury (mm Hg).
four component parts:
Use of the anticoagulant heparin added to the normal saline flush setup to maintain catheter patency is controversial.
Although many units do add heparin to flush solutions, other critical care units avoid heparin because of concern about development of heparin-induced antibodies that can trigger an autoimmune condition known as heparin-induced thrombocytopenia (HIT).
Dextrose solutions are not recommended as flush solutions in monitoring catheters.
Heparin
Two baseline measurements are necessary:
1. Calibration of the system to atmospheric pressure, also known as zeroing the transducer
2. Determination of the midaxillary axis for transducer height placement, necessary to accurately level the transducer
Calibration of Hemodynamic Monitoring Equipment
calibrate the equipment to atmospheric pressure, referred to as zeroing the transducer, the three-way stopcock nearest to the transducer is turned simultaneously to open the transducer to air (atmospheric pressure) and to close it to the patient and the flush system.
Using zero to represent current atmospheric pressure provides a convenient baseline for hemodynamic measurement purposes.
Some monitors also require calibration of the upper scale limit while the system remains open to air.
Disposable transducers are very accurate, and after they are calibrated to atmospheric pressure, drift from the zero baseline is minimal.
Zeroing the Transducer
physical reference point on the side of the chest that is used as a baseline for consistent transducer height placement.
a theoretical line is drawn from the fourth sternal intercostal space, where it joins the sternum, to a theoretical line on the side of the chest that is one half of the depth of the lateral chest wall.
The level of the transducer “air reference stopcock” approximates the position of the tip of an invasive hemodynamic monitoring catheter within the chest.
Midaxillary Line (Phlebostatic Axis)
This process aligns the transducer with the level of the left atrium. The purpose is to line up the air fluid interface with the left atrium to correct for changes in hydrostatic pressure in blood vessels above and below the level of the heart.
If the transducer is placed above this atrial level, gravity and lack of fluid pressure give an erroneously low reading.
Every inch the transducer is positioned above the catheter tip, the measurement is 1.87 mm Hg less than the true value.
When there is a change in the patient’s position, the transducer must be leveled again to ensure that accurate hemodynamic pressure measurements are recorded.
Patient Position During Hemodynamic Monitoring.
emphasis on raising the head of the bed above 30 degrees to prevent aspiration, and position changes to prevent sacral skin pressure injury, require a reevaluation of transducer level with each position change.
Leveling the Transducer
Nurse researchers have determined that the central venous pressure (CVP), pulmonary artery pressure (PAP), and pulmonary artery occlusion pressure (PAOP), also known as pulmonary artery wedge pressure, can be reliably measured at head of bed backrest positions from 0 (flat) to 60 degrees if the patient is lying on his or her back (supine).
Most patients do not need the head of the bed to be lowered to 0 degrees to obtain accurate CVP, PAP, or PAOP readings, as long as the midaxillary line is used as the reference point.
Head of Bed Backrest Position
30-degree angle position, the landmark to use for leveling the transducer is one-half of the distance from the surface of the bed to the left sternal border.6 In the 90-degree right-lateral position, the transducer fluid air interface was positioned at the fourth intercostal space at the midsternum. In the 90-degree left-lateral position, the transducer was positioned at the left parasternal border (beside the sternum). It is important to know that measurements can be recorded in nonsupine positions, because critically ill patients must be turned to prevent development of pressure injury and other complications of immobility.
Lateral Position
Indications
Catheters
Insertion and Allen Test
Nursing Management
Infection
Perfusion Pressure
Noninvasive Cuff Blood Pressure
Arterial Pressure Waveform Interpretation
Hemodynamic Monitoring Alarms
Invasive Hemodynamic Monitoring
Intraarterial Blood Pressure Monitoring
Arterial blood pressure monitoring is indicated for any major medical or surgical condition that has the potential to alter blood pressure or cardiac output (CO), tissue perfusion, or fluid volume status.
The system is designed for continuous measurement of three blood pressure parameters: systole, diastole, and mean arterial pressure (MAP).
Indications
Seldinger technique is typically used, which involves the following steps:
1. Entry into the artery using a needle
2. Passage of a supple guidewire through the needle into the artery
3. Removal of the needle
4. Passage of the catheter over the guidewire
5. Removal of the guidewire, leaving the catheter in the artery
Catheters
Several major peripheral arteries are suitable for receiving a catheter and for long-term hemodynamic monitoring. The most frequently used site is the radial artery. The femoral artery is a larger vessel that is also frequently cannulated. Other smaller arteries such as the dorsalis pedis, axillary, or brachial arteries are used only when other arterial access is unavailable.2
The major advantage of the radial artery is the supply of collateral circulation to the hand provided by the ulnar artery through the palmar arch in most people.
collateral circulation must be assessed by using Doppler flow or by the modified Allen test according to institutional protocol.
Insertion and Allen Test
Intraarterial blood pressure monitoring is designed for continuous assessment of arterial perfusion to the major organ systems of the body. MAP is the clinical parameter most often used to assess perfusion, because MAP represents perfusion pressure throughout the cardiac cycle.
Nursing Management
associated with the same risk of blood-stream infections as central venous catheters. Therefore infection prevention measures must be just as meticulous for arterial catheters as for central catheters
Infection
A MAP greater than 60 mm Hg is necessary to perfuse the cor-
onary arteries. A higher MAP may be required to perfuse the brain and the kidneys. A MAP between 70 and 90 mm Hg is preferable for a patient with heart disease to decrease left ventricular (LV) workload. After carotid endarterectomy or neurosurgery, a higher MAP of 90 to 110 mm Hg may be more appropriate to increase cerebral perfusion pressure.
If CO decreases, the body compensates by constricting peripheral vessels to maintain the blood pressure.
Nursing assessment of a patient with an arterial line includes comparison of clinical findings with arterial line readings including perfusion pressure and MAP.
Perfusion Pressure
In most nonemergency situations, following the trend of the arterial pressure is more valuable than an isolated measurement
Pulse Pressure
If the arterial line becomes unreliable or dislodged, a cuff pressure can be used as a reserve system. However, research studies indicate that a noninvasive cuff blood pressure does not produce the same values as an intraarterial catheter.
The concern is that the cuff pressure may be unreliable because of peripheral vasoconstriction. It is usual practice to compare a cuff pressure after the arterial line is inserted to identify and document any difference in pressure readings.
Noninvasive Cuff Blood Pressure
As the aortic valve opens, blood is ejected from the left ventricle and is recorded as an increase of pressure in the arterial system.
The highest point recorded is called systole. After peak ejection (systole), the force decreases, and the pressure falls. A notch (dicrotic notch) may be visible on the downstroke of this arterial waveform, representing closure of the aortic valve. The dicrotic notch signifies the start of blood flow into the arterial vasculature. The lowest point recorded is called diastole.
Decreased arterial perfusion.
Pulse deficit.
Pulsus paradoxus.
Pulsus alternans.
Damped waveform.
Underdamped waveform.
Fast-flush square waveform test.
Arterial Pressure Waveform Interpretation
Specific problems with heart rhythm can translate into poor arterial perfusion if CO decreases. Poor perfusion may be seen as a single, nonperfused beat after a premature ventricular contraction (PVC) or as multiple, nonperfused beats
Decreased arterial perfusion.
A pulse deficit occurs when the apical HR and the peripheral pulse are not equal. In the critical care unit, this can be seen on the bedside monitor. Normally, there is one arterial upstroke for each QRS complex, and if there are more QRS complexes than arterial upstrokes, a pulse deficit is present
To determine whether a pulse deficit is significant, it is necessary to evaluate the clinical effect on the patient and whether any change in MAP or pulse pressure has occurred.
Pulse deficit.
a decrease of more than 10 mm Hg in the arterial waveform that occurs during inhalation (inspiration). It is caused by a fall in CO as a result of increased negative intrathoracic pressure during inhalation.
In certain clinical conditions, the pulsus paradoxus is obvious and can be clearly seen on an arterial waveform. It can be used as a clinical diagnostic test for a patient with cardiac tamponade, pericardial effusion, or constrictive pericarditis.
Pulsus paradoxus may also be observed in hypovolemic surgical patients who are mechanically ventilated with large tidal volumes
Pulsus paradoxus.
every other arterial pulsation is weak. This sometimes occurs in individuals with advanced LV heart failure.
Pulsus alternans.
If the arterial monitor shows a low blood pressure, it is important to determine whether the problem is related to the patient or to the monitoring equipment,
In this case the arterial waveform is more rounded, without a dicrotic notch, compared with a normal waveform, and the digital readout correlated with the patient’s cuff pressure, adding confirmation that the patient was hypotensive.
A damped (flattened) arterial waveform: in this case the patient’s cuff pressure was significantly higher than the digital readout, representing a problem with equipment.
Damped waveform occurs when communication from the artery to the transducer is interrupted and produces falsely lower values on the monitor and oscilloscope.
Troubleshooting techniques are used to find the origin of the problem and to remove the cause of damping
Damped waveform.
Another cause of arterial waveform distortion is underdamping, also called overshoot or fling. Underdamping is recognized by a narrow upward systolic peak that produces a falsely high systolic reading compared with the patient’s cuff blood pressure,
over-shoot is caused by an increase in dynamic response or increased oscillations within the system
Underdamped waveform.
dynamic response of the monitoring system can be verified for accuracy at the bedside by the fast-flush square waveform test, also called the dynamic frequency response test
nurse performs this test to ensure that the patient pressures and waveform shown on the bedside monitor are accurate
makes use of the manual flush system on the transducer.
If air bubbles, clots, or kinks are in the system, the waveform becomes damped, or flattened, and this is reflected in the square waveform result.
should be incorporated into nursing care procedures at the bedside when the hemodynamic system is first set up, at least once per shift, after opening the system for any reason, and when there is concern about the accuracy of the waveform.
must be able to assess whether a low MAP or narrowed perfusion pressure represents decreased arterial perfusion or equipment malfunction.
Fast-flush square waveform test.
All critically ill patients must have the hemodynamic monitoring alarms on and adjusted to sound an audible alarm if the patient should experience a change in blood pressure, HR, respiratory rate, or other significant monitored variable.
Alarm limits must be customized to the patient’s physiologic baseline to reduce false-positive alarms.
Hemodynamic Monitoring Alarms
Invasive hemodynamic monitoring refers to monitoring situations where catheters are placed into central veins or pass through the right heart chambers predominantly describing central venous catheters, pulmonary artery catheters, thermodilution CO, and continuous mixed-venous oxygen saturation monitoring. Some of the newer monitoring methods that combine arterial and central venous monitoring systems also are considered invasive
Invasive Hemodynamic Monitoring
Indications
Central Venous Catheters
Insertion
Central Venous Catheter Complications
Nursing Management
Specialized Central Venous Catheters
Central Venous Pressure Monitoring
whenever a patient has a significant alteration in fluid volume used as a guide for fluid volume replacement in hypovolemia. In addition to clinical signs and symptoms, CVP is also monitored in hypervolemia to assess the effect of diuresis after diuretic administration
Indications
Antimicrobial-impregnated or heparin-coated catheters have a lower rate of bloodstream infections.
Central Venous Catheters
large veins of the upper thorax, the subclavian (SC) and internal jugular (IJ), are most commonly used for percutaneous CVC line insertion. The femoral vein in the groin is used when the thoracic veins are not accessible.
Internal jugular vein.
Subclavian vein.
Femoral vein.
Insertion
most frequently used easiest to canalize.
blood flow is significantly higher in the IJ vein
Another advantage of the IJ vein is that the risk of creating an iatrogenic pneumothorax is small.
Disadvantages to the IJ vein are patient discomfort from the indwelling catheter when moving the head or neck and contamination of the IJ vein site from oral or tracheal secretions, especially if the patient is intubated or has a tracheostomy.
infections are higher in the IJ than the SC position for indwelling catheters left in place for more than 4 days.
Internal jugular vein.
anticipated CVC dwelling time is prolonged (more than 5 days), the SC site is preferred.
has the lowest infection rate and produces the least patient discomfort from the catheter.
disadvantages are that the SC vein is more difficult to access and carries a higher risk of iatrogenic pneumothorax or hemothorax, although the risk varies greatly depending on the experience and skill of the physician inserting the catheter.
Subclavian vein.
considered the easiest cannulation site, because there are no curves in the insertion route.
The large diameter of the femoral vein carries a high blood flow that is advantageous for specialized procedures such as continuous renal replacement therapy or plasmapheresis. Because there is a higher rate of nosocomial infection with femoral catheters, this site is not recommended.
The tip of the catheter is designed to remain in the vena cava and should not migrate into the right atrium. Because many patients are awake and alert when a CVC is inserted, a brief explanation about the procedure can minimize patient anxiety and result in cooperation during the insertion.
The electrocardiogram (ECG) should be monitored during CVC insertion because of the associated risk of dysrhythmias.
A chest radiograph is obtained after upper thoracic CVC placement to verify placement and the absence of an iatrogenic hemothorax or pneumothorax, especially if the SC vein was accessed.
Femoral vein.
Air embolus
Thrombus formation.
Infection.
Central Venous Catheter Complications
Air can enter during insertion through a disconnected or broken catheter by means of an open stopcock, or air can enter along the path of a removed CVC. This is more likely if the patient is in an upright position,
Treatment involves immediately occluding the external site where air is entering, administering 100% oxygen, and placing the patient on the left side with the head downward (left lateral Trendelenburg position). This position displaces the air from the right ventricular outflow tract to the apex of the heart, where the air may be aspirated by catheter intervention or gradually absorbed by the bloodstream as the patient remains in the left lateral Trendelenburg position. Precautions to prevent an air embolism in a central line include using only screw (Luer-Lock) connections and using only closed-top screw caps on all three-way stopcocks.
Air embolus
it may involve development of a fibrin sleeve around the catheter, or the thrombus may be attached directly to the vessel wall
Other factors that promote clot formation include rupture of vascular endothelium, interruption of laminar blood flow, and physical presence of the catheter, all of which activate the coagulation cascade.
Because of concerns over the development of HIT, many hospitals use a saline-only flush to maintain CVC patency.
Thrombus formation.
infection incidence strongly correlates with the length of time the CVC has been inserted, with longer insertion
times associated with higher infection rates.
identified at the catheter insertion site or as a blood-stream infection (septicemia). Systemic manifestations of infection can be present without inflammation at the catheter site.
Most infections are transmitted from the skin, and infection prevention begins before insertion of the CVC.
To decrease the infection risk, most hospitals routinely audit use of CVCs to reduce the CVC duration to the absolute minimum, as fewer insertion days means fewer CLABSIs.
Infection.
The CVC is used to monitor the CVP and waveform. The CVP catheter is used to measure the filling pressures of the right side of the heart.
Normal CVP is 2 to 5 mm Hg (3 to 8 cm H2O).
Central venous pressure volume assessment.
Passive leg raise.
Removal.
Patient position.
Central venous pressure waveform interpretation.
Nursing Management
Use of the CVP value to assess volume status is considered inaccurate.
Use of the CVP value to assess volume status is considered inaccurate.
Central venous pressure volume assessment.
Another method to assess fluid responsiveness is to passively raise and support the patient’s legs to allow the venous blood from the lower extremities to flow rapidly into the vena cava and return to the right heart.
This method has the advantage of not infusing any IV fluid.
However, a change in the CVP value is not considered as reliable as using real-time monitoring of CO using a pulse wave analysis method
Passive leg raise.
Removal of the CVC usually is a nursing responsibility. Complications are uncommon, and the ones to anticipate are bleeding and air embolus
Recommended techniques to avoid air embolus during CVC removal include removing the catheter when the patient is supine in bed (not in a chair) and placing the patient flat or in reverse Trendelenburg position if the patient’s clinical condition permits this maneuver.
If the patient is alert and able to cooperate, he or she is asked to take a deep breath to raise intrathoracic pressure during removal.
After removal, to decrease the risk of air entering by a “track,” an occlusive dressing is applied to the site. If bleeding at the site occurs after removal, firm pressure is applied.
Removal.
