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RTT 214 - Ch. 16
Ch. 16 - Assessment of Hemodynamic Pressures
| Question | Answer |
|---|---|
| why is invasive hemodynamic monitoring needed? | clinical assessment alone may not accurately predict hemodynamics |
| what must be considered before a catheter is placed in a pt? | risk-benefit ratio of invasive monitoring |
| what is hemodynamic monitoring performed to do? | evaluate: intravascular fluid vol, cardiac/vascular function; identify sudden changes in hemodynamics |
| why is invasive monitoring needed? | obtain an accurate evaluation of hemodynamics |
| what type of pt may a physician place an arterial catheter? | significant hemodynamic instability or freq arterial blood draws |
| what conditions are likely candidates for arterial pressure monitoring? | severe hypotension (shock) or HTN; respiratory failure |
| what pts may benefit from arterial pressure monitoring? | pts in need of meds that affect BP (vasodilators/inotropic agents) |
| how many arterial catheter sizes are in common use and what is selection determined by? | two; planned insertion site |
| where is the smaller catheter ideal for use? where is it not adequate? | radial/small arteries; femoral/large arteries |
| how do arterial catheter walls compare with central venous catheters? | thin and stiff |
| where is the arterial catheter usually placed? | radial, ulnar, brachial, axillary, femoral |
| where is the arterial line most often placed and why? | radial; readily accessable/adequate collateral circulation |
| the radial site is easy to _______ and what does it provide? | monitor; stable site for blood withdrawal |
| what does the femoral artery provide? | pressure measurements less affected by peripheral vasoconstriction; leakage of blood occurs |
| the _________ technique is used for most arterial catheter insertions. | "Seldinger" |
| what should the arterial pressure waveform include? | clear upstroke on left, w/ dicrotic notch (aortic valve closure) on downstoke to right |
| what happens if the dicrotic notch is not present? | pressure tracing dampened, inaccurate; numbers are lower that actual pressure |
| the dicrotic notch disappears in some pts when the systolic pressure drops below __-__ mmHg. | 50-60 |
| the left side of the pressure wave may become straight and even pointed on the top when there is an increase in...? when else does this happen? | circulating catecholamines that causes an increased inotropic response; stiff aorta |
| increases in HR and vascular resistance _______ diastolic pressure. | increase |
| what can cause the diastolic pressure to drop? | vasodilation that decreases vascular resistance |
| because approx ___% of coronary artery perfusion occurs during the diastolic phase, coronary arterial perfusion may be compromised if the diastolic pressure falls below ___ mmHg. | 70%; 50 |
| what must be considered when respiratory variation in the arterial pressure waveform is seen? | cardiac tamponade or other causes of paradoxical pulse |
| when are increases in arterial pressure during inspiration seen? | after heart surgery; pts w/ LV failure with MV and PEEP |
| what can cause variations in the height and shapes of the waveforms? | dysrhythmias and pulsus alternans |
| what is the normal arterial pressure in the adult? | 120/80 mmHg |
| what values are considered hypertensive? | >160/90 mmHg |
| what values are considered hypotensive? | <90/60 mmHg |
| arterial pressure is only a general sign of _________ status. | circulatory |
| what is pressure the product of? | flow and resistance |
| what is low blood pressure a late sign of? | deficits in blood volume or cardiac function |
| what is earlier evidence of decreased blood volume or CO? | cold, clammy extremities (caused by catecholamine-mediated peripheral vasoconstriction) |
| what are the causes of hypotension? | low blood vol (bleeding), cardiac failure/shock (heart attack), vasodilation (sepsis) |
| during administration of what drugs should diastolic pressure be watched carefully? | vasodilators such as sodium nitroprusside |
| what values of diastolic pressure may result in compromised coronary perfusion? | diastolic pressures <50 mmHg; mean pressure <60 mmHg |
| what are the causes of hypertension? | improvement in circulatory vol/function, sympathetic stimulation, vasoconstriction, vasopressors |
| administration of ________ _____ may or may not increase BP. | inotropic agents |
| what inotropic agent can cause vasodilation? | isoproterenol (isuprel) |
| besides systolic/diastolic pressures, what else does arterial pressure monitoring allow assessment of? | pulse and mean arterial pressures |
| what is pulse pressure? and what is the normal? | difference b/t systolic and diastolic pressure; 30-40 mmHg |
| what is pulse pressure reflection of? | SV by the LV and arterial system compliance |
| what is a decreasing pulse pressure a sign of? | low SV |
| what is an increasing SV in a pt receiving fluid therapy consistent with? | improved preload |
| what is mean arterial pressure? | avg of pressures pushing blood through the systemic circulation (most important of arterial pressures) |
| what is mean arterial pressure an indicator of? | tissue perfusion |
| what is the normal MAP? | 80-100 mmHg |
| what is the MAP calculation? | systolic pressure + (diastolic pressure x 2)/3 |
| when is circulation to the vital organs compromised? | MAP <60 mmHg |
| what is elevated MAP associated with? | increased risk of stroke and heart failure (need vasodilators or negative inotropics) |
| what is MAP use to calculate? | SVR, LVSW, cardiac work |
| what is a major compication of direct arterial monitoring? | ischemia resulting from embolism, thrombus, or arterial spasm |
| what is this complication evidenced by? | pallor distal to the insertion site; pain and paresthesias |
| what can ischemia result in? | tissue necrosis (if catheter is not repositioned or removed) |
| what is thrombosis prevented by? | irrigation w/ diluted heparanized solution |
| __________ is possible if the line becomes disconnected or a stop cock is left open. | hemorrhage |
| what else can occur at the insertion side especially if the catheter was placed through a needle? | bleeding and hematoma |
| as with all invasive lines, the presence of an arterial catheter increases the risk of _________. | infection |
| _______ in pts with invasive lines must trigger questions about the necessity of the lines and their role as a cause of the infection process. | fever |
| _______ _______ ________ is the pressure of the blood in the RIGHT atrium or vena cava, where the blood is returned to the heart from the venous system. | central venous pressure |
| what does CVP also represent? | RVEDP and preload (filling vol) for RV |
| when is CVP monitoring indicated? | assess circulating blood vol (filling pressures), degree of venous return, assess RV function |
| what pts need a CVP catheter? | pts w/ major surgery or trauma, severe dehydration; pulmonary edema; pts with damage to RV from MI |
| what are the most common central venous catheters? | 7-french, 3-lumen catheters w/ one distal port and two pots 3-4 cm from the distal end of catheter |
| what does the multiple-lumen catheter allow? | infusion of blood samples and medications |
| what catheters are less commonly associated with infection? | those impregnated with antibiotics |
| what are the common sites for introduction of central venous catheters? | subclavian, internal jugular, femoral veins |
| what is an advantage of the subclavian vein approach? | results in stable catheter after placement |
| what is a disadvantage of the subclavian vein approach? | more difficult to find |
| what approach is easier because there is nearly a straight shot for the guidewire to reach the superior vena cava and less risk for pneumothorax and hematomas are easier to see and control? | internal jugular vein approach |
| what are the disadvantages of the internal jugular vein approach? | catheter less stable, subject to kinking, breakage, and accidental removal |
| what central venous catheters are the easiest to place and have the least risk for complications, but they provide less reliable hemodynamic info b/c the catheter tip is far from RA, pressure waveforms often dampened? | femoral central venous catheters |
| what should be performed after subclavian or internal jugular central venous line insertion? | CXR (ensure placement/rule out pneumothorax) |
| where is the subclavian vein entered? | edge of the distal third of the clavicle |
| where is the internal jugular vein entered? | head of the clavicle or a site behind the brachial artery |
| where is the femoral vein entered? | just medial to the femoral artery in the groin |
| what is the only difference b/t these techniques? | the head of the pt's bed is lowered for subclavian/internal jugular vein insertions |
| what does doing this cause? | increases size of vein, making it easier; decreases risk of air embolism |
| what do CVP waveforms reflect? what is it equivalent too? | pressure changes in the R atrium; PAWP (approximates L atrial pressure) |
| what do CVP and PAWP waveforms both include? | three waves - a, c, v |
| what does the a wave result from and occur during? | atrial contraction; ventricular diastole |
| when the atrium contracts against a closed valve, as occurs during atrioventricular dissociation or w/ some junctional or ventricular pacemaker rhythms, what occurs? | large a waves called cannon waves |
| what does the downslope of the a wave (x descent) result from? | decrease in atrial pressure |
| when does the c wave occur? | AV valve closure; represents movement of AV valve back toward atrium during V contraction |
| what does the v wave result from? | atrial filling while the AV valve is closed during ventricular systole |
| when does the downslope of the v wave occur? | when tricuspid and mitral valves open and the ventricle begins to fill with blood |
| what is it referred to as when the AV valve does not close all the way and some of the blood is ejected backward into the atrium during systole? | tricuspid regurgitation (exaggerated v waves and elevated CVP measurement) |
| what are the most likely causes of no respiratory artifact seen on the trace and the pt is not holding their breath? | kink/air in tube, stopcoack turned in wrong direction, small clot/kink in catheter |
| what should happen to the waveform if the patient is asked to take a deep breath? | fall below baseline as intrathoracic pressure falls w/ inspiration |
| when does CVP decrease and increase? | d: spontaneous inspiration, i: MV |
| how can a mean venous pressure without resp artifact be obtained if spontaneously breathing? on MV? | suspend breathing; disconnect ventilator |
| what are hte two ways CVP can be obtained? | transducer system (mmHg) or a water manometer (cmH2O) |
| which method is more accurate assessment of mean CVP or right atrial pressure and also allows observation of the CVP waveform? | transducer |
| what are the advantages of the water manometer? | inexpensive, does not require electric equipment, easy to use |
| when is CVP ideally read and why? | end of expiration, spontaneous inspiration causes pressure to fall and MV causes it to rise |
| what does the criteria for interpretation of CVP by water manometer include? | 1. X-ray 2. IV fluid 3. ability to easily aspirate blood sample 4. rapidly falling H2O column 5. small oscillations at top of H2O column 6. larger oscillations w/ respiration |
| what does the comparison of water manometer methods w/ transduccer methods demonstrate? | water manometer method usually overestimates transducer-determined mean RA pressure (CVP) |
| what CVP regulated by? | balance b/t ability of heart to pump blood out of RA and V and amount of blood returned to the heart by venous system (venous return) |
| when the pumping ability of the right heart is increased, CVP ________; when pumping ability decreases, CVP _________. | decreases; increases |
| what are 6 causes of increased CVP? | fluid overload, R/L heart failure, pulmonary HTN, tricuspid valve stenosis, pulm embolism, increased venous return |
| what are 4 causes of decreased CVP? | vasodilation, reduced circulating blood vol, leaks in pressure system/air bubbles, spontaneous inspiratino |
| what does the CVP reflect when a pt is hypovolemic but has pulmonary HTN with decreased RV function? | elevated pressure from the loss of ventricular function, does not fall to level that are expected |
| when is this most commonly seen? | cor pulmonale who become dehydrated and hypovolemic |
| when can CWP be used to estimate LV filling pressures and performance? | pts w/ an EF >0.50, no cardiopulmonary disease |
| what is CVP a reasonable option for the management of? | intraoperative fluid levels, postop fluid levels, vol replacement in young pts w/ no hx of heart disease or HTN |
| who may benefit from monitoring of both the left and right heart pressures? | pulmonary HTN disease |
| what problems can placement of the catheter cause? | bleeding, pneumothorax |
| when is bleeding more likely? | when pt is taking heparin or low platelet count; subclavian artery penetrated |
| when can pneumothorax occur? | catheter punctures the pleural lining |
| what is the most common complication associated with use of the catheter over time? what is a less common complication? | infection; thrombus around the catheter |
| what can accidental opening of the central venous line stopcock allow and result in? | air to enter vein, air embolus |
| what does the PAC allow the assessment of? | filling pressures of the left side of the heart |
| what does the PAC allow the assessment of? | LV filling pressures (via PADP/PCWP); PVR (via PA mean systolic pressures/PCWPs), SVR (via systemic arterial mean pressure/PAEDP); CO; arteriovenous O2 difference, mixed venous O2 levels |
| what is the only place w/ swan-ganz catheter to get the most accurate assessment of oxygenation? | arteriovenous O2 difference; mixed venous O2 levels |
| PAC is more a risk than CVP because why? | need for catheter to pass through the R side of the heart and into PA (may cause dysrhythmias or other complications) |
| what are common factors to consider when placing a PAC? | experience of physician, availability of proper equipment/personnel, diagnosis, cardiac/pulm hx |
| what are the common situations in which PAC monitoring is considered? | severe cardiogenic pulm edema; ARDS (hemodynamically unstable); major thoracic surgery; cardiogenic/septic shock pts |
| what are PACs also called? | swan-ganz catheters |
| what is the balloon at the tip of the catheter used for? | float the catheter into position (into the R side of heart and into PA) and obtain wedge pressure measurements |
| what is another name for the catheter? | balloon-tipped, flow-directed catheter |
| what are the catheters available for children? what is most commonly used for adults? | 4- and 5-french catheters w/ 2 or 3 lumens; 7-french w/ 3-lumens (air channel for balloon) |
| the distal lumen terminates at the tip of the catheter, what is it used for? | measuring PA pressures, aspirating mized venous blood samples, injecting meds |
| what might the balloon help prevent? | PVCs |
| what is the proximal port used for? | aspirating blood samples, measuring CVP, injecting drugs, injecting thermal bolus used for thermodilution CO measurements |
| some catheters have 2 lumens ending in the RA, what are these used for? | 1. routine infusion of drugs/continuous pressure monitoring 2. infusion of thermodilution materials/periodic injections |
| what are the most popular sites for PAC used in ICU? | subclavian/internal jugular veins |
| the PAC can be positioned used __________, but is more often...? | fluoroscopy; floated into place using pressure waveforms to indicate position |
| what is the insertion technique for PAC? | 1. balloon inflated at superior vena cava or RA 2. catheter floats through R side, into PA 3. wedges into place, balloon deflated |
| what are seen as catheter passes through the RA, RV, PA, and into wedge position? | distinctive waveforms |
| what is the normal pressure for RA? RV? PA? PCWP? | RA: 2-6 mmHg; RV: 20-30/0-5 mmHg; PA: 20-30/6-15 mmHg (mean pressures: 10-20 mmHg); PCWP: 4-12 mmHg |
| in most adults, catheters inserted through the subclavian or jugular vein are positioned in the PA when approximately ___cm of catheter is inserted into the pt. | 50 |
| what is entry into the PA recognized by? | change in the diastolic portion of the wavefomr |
| PA maintains pressure throughout the cardiac cycle so that the basline pressure usually increases to ___-___ mmHg over RV diastolic pressures. | 8-15 |
| PA _______ pressure is the highest pressure created when the RV ejects blood through the pulmonary valve and into the PA and lungs. | systolic |
| what is normal PA systolic pressure? | 20-30 mmHg |
| when does PA pressure decrease? increase? | d: vol of blood from RV decreases, decreased PVR; i: pulm blood flow increases, PVR increases |
| what can resistance to pulmonary flow (increased PVR) be caused by? | constriction, obstruction, or compression of the pulmonary vasculature or backpressure from the L heart |
| what conditions cause increased PVR? | pulmonary emboli; acute/chronic lung disease; cardiac tamponade; L heart failure |
| what is the normal PA diastolic pressure? what does it reflect? | 8-15 mmHg; pulm venous, LA, LVEDP |
| what is a PADP-PCWP gradient >5 mmHg a characteristic of? | ARDS, sepsis, excessive PEEP, anything that increases PVR |
| what is normal PCWP? what is PCWP also called? and what is it used to monitor? | 4-12 mmHg; pulmonary artery occlusion pressure; LV filling during diastole |
| what will hx of MI cause? | stiff LV and lead to higher pressures |
| in the normal heart, optimal SV is obtained with a PCWP of ___-___ mmHg. in the pt with LV hypertrophy, a PCWP of ___ mmHg or higher may be needed to optimize SV. | 10-12; 18 |
| when does PCWP increase? | LV failure (common cause); mitral valve regurgitation; pulm venous circulation obstructed w/ tumor |
| what is the most common cause of a decreased PCWP? what also decreases PCWP? | hypovolemia; severe dehydration |
| what is zone I? | no blood flow b/c alveolar pressure exceeds both pulmonary venous pressure and MAP |
| what is zone II? | alveolar pressure exceeds venous pressure but is less than MAP |
| what is zone III? | area of lung where both PA and venous pressures exceed alveolar pressure |
| what does the catheter in zone II measure? | PAP w/ balloon deflated but reflects alveolar pressure when it is wedged |
| zone II conditions dominate in ________ pts. | supine |
| to measure L heart pressure accurately, the catheter tip must be in zone ___. | III |
| when can zone III areas convert to zone I or II? | when intravascular vol decreases or alveolar pressure increases |
| alterations in ventilatory patterns cause fluctuations in __________ _______. | intrapleural pressure |
| wedge pressure readings normally are about __ mmHg lower than pulmonary diastolic pressure readings b/c blood flows from high pressure to low pressure. | 2 |
| what is transmural pressure? | the net distending pressure within the ventricle |
| how is the transmural pressure calculated? | subtracting the pressure around the heart from the measure filling pressure of the heart |
| what is wedge pressure used to estimate? | LV filling pressure inside the heart |
| what is used to approximate the pressure pushing on the heart from the outside? | intrapleural or esophageal pressure |
| what are the 2 ways PEEP is subtracted from wedge pressures? | 1. compliant lungs: 1/2 of PEEP from PCWP 2. noncompliant lungs: 1/4 of PEEP from PCWP |
| what complications of PA catherization is possible during cannulation of a central vein? | pneumothorax; hydrothorax; hemothorax; air embolism; damage to the vein, arteries, nerves |
| what can movement of the catheter inside the heart trigger? | bundle-branch block; supraventricular or ventricular dysrhythmia |
| constant movement of the catheter with heartbeat, breathing, and pt movement can result in ________ _________. | catheter migration |
| _________ ___________ and even PA rupture can result from overfilling the balloon while obtaining a wedge pressure, as well as from catheter migration. | pulmonary infarction |
| what should be immediately available at both insertion adn removal? | lidocaine and emergency resuscitation equipment |
| what should be optimized to decrease the risk of dysrhythmia? | blood gases and serum electrolytes |
| what is not normal and is an indication for obtaining a CXR to assess the cause? | catheter resistance |
Created by:
christa_2008
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