Ch. 8 Hemodynamic Monitoring

Resp Variation to Assess Preload Responsiveness

- RAP variation - systolic pressure variation - arterial pressure variation - SV variation

cardiac cycle

- Systole: heart contracts and pumps out blood - Diastole: heart relaxes and chambers fill with blood

causes of innacurate arterial line readings

- air bubbles in the catheter system - failure to zero the transducer air-fluid interface - blood in the system - blood clot at the catheter tip

pulmonary artery cath

- assess left heart function with PAOP pressures - identify and treat cause of hemodynamic instability - assess pulmonary artery pressures - assess mixed venous o2 sat (SvO2) - directly measure CO

overdamped system causes and interventions

- blood clots/air bubbles: flush the system or aspirate, d/c from the pt to adequately flush to remove clots or bubbles if needed - compliant tubing: change to noncombliant - loose connections - kinks: straighten the tubing

- low SvO2 (<60%)

- decreased O2 delivery: hypoxia, hemorrhage, anemia, hypovolemia, cardiogenic shock, dysrhythmias, MI, CHF, cardiac tamponade - increased O2 consumption: fever, pain, anxiety, hormonal imbalance, late septic shock, seizures

causes of SV reduction

- decreased preload: hemorrhage, hypovomemia, vasodilation, fluid shifts - increased afterload: vasoconstriction, increased blood viscosity - decreased contractility: MI or ischemia, HF, cardimyopathy, cardiogenic shock, cardiac tamponade

managing a hemodynamic monitoring system

- document insertion date - change dressings - maintain patency of the flush system: flush after each use, clear any blood from the tubing, maintain a pressure of 300 mmHg, ensure adequate amount of flush solution in the Iv bag - ensure tightened connections - no kinks - minimize excess tubing and stopcocks - limit d/c or opening of the system - ensure the alarm limits are set

underdamped system

- excessive tubing length: remove extraneous tubing, stopcocks, or extensions - small-bore tubing: replace with a larger bore set - unknown causes: add a damping device into the system

causes of high CO

- heart rate elevation s/t: increased activity, anemia, metabolic demands, adrenal disorders, fever, anxiety - SV increase as a result of: increased preload (fluid resus, alteration in ventricular compliance), decreased afterlaod (vasodilation, anemia, increased contract, hypermetabolic state, med therapy)

causes of low CO

- heart rate too fast/slow, leading to inadequate ventricular filling - stroke volume reduction

- high SvO2 (>75%)

- increased O2 deliver: increase in FiO2, hyperoxygenation - decreased O2 consumption: hypothermia, anesthesia, neuromuscular blockade

atrial stiffening

- increased arterial systolic and pulse pressure - increased aortic wall thickness - increased LV wall tension which leads to LV hypertrophy

basic hemodynamic monitoring system

- invasive cath - high pressure noncompliant tubing - transducer with a stopcock - pressurized flush system - bedside monitoring system

alterations in mixed venous O2 sat

- low SvO2 (<60%) - high SvO2 (>75%) - high SvO2 (>80%)

centrial venous cath

- measure right heart filling pressures - estimate fluid status - guide volume resuscitation - assess central venous o2 sat (ScvO2) - access to place transvenous pacemaker

indications for arterial line

- treat hemodynamic instability - assess efficacy of vasoactive meds - obtain frequent blood samples for ABG or lab tests - can be used in conjuction with a stroke volume measurement device

potential comps of invasive hemodynamic monitoring devices

- vascular comp: thrombosis, hematoma - infection - bleeding - pneumothorax or hemothorax - cardiac dysrhythmias - pericardial tamponade

cardiac contraction

Begins with pressure in Lt ventricle rising rapidly Lt ventricle pressure exceeds that in AO AO valve opens, blood is ejected, BP rises Increased HR delivers increased blood volume Pt's cardiac status plays important role in blood movement through vasc system

advantages of CCO

Continuous cardiac output removes the potential for operator error associated with intermittent TdCO measurement. ■ Other advantages of CCO are that no extra fluid is administered to the patient, data are available for trending throughout the shift, and there is no need to change the computation constant in the CO module.

● Two methods are commonly used to evaluate CO via the PA catheter:

thermodilution cardiac output (TdCO) and CCO.

complications of artieral lines

thrmobosis, embolism, blood loss, infection

square wave test

Observe waveform sharply rise and "square off", release flush and the waveform returns to baseline—count the number of oscillations and observe distance between them.

goal of hemodynamic monitoring is...

to maintain adequate tissue perfusion - assess the patient and provide therapies to optimize O2 delivery and tissue perfusion

- high SvO2 (>80%)

techinal error: PA cath in wedged position, fibrin clot, computer needs to be recalibrated

Allen Test

test that determines the patency of the radial and ulnar arteries by compressing one artery site and observing return of skin color as evidence of patency of the other artery

methods for determing accurate right atrial pressure

mean of the a wave

SvO2

measured in the PA ● An SvO2 between 60% and 75% indicates an adequate balance between supply and demand.

ScvO2

measured in the central venous system, usually the superior vena cava.

Esophageal Doppler monitoring (EDM)

uses a thin silicone probe placed in the distal esophagus, allowing the clinician to evaluate descending aortic blood flow, which provides real-time assessment of left ventricular performance ■ The probe is lubricated and inserted either orally or nasally with the bevel facing upward until the depth of the catheter is approximately 35 to 40 cm. ■ The EDM monitor provides a variety of clinical parameters, including CO and SV derived from a proprietary algorithm. ■ Normal FTc is 330 to 360 milliseconds (ms). Normal PV varies by age: 90 to 120 cm/sec for a 20-year-old person, 70 to 100 cm/sec for a 50-year-old person, and 50 to 80 cm/sec for a 70-year-old person.

preventing infection

■ A centril line bundle: emphasizes strict hand washing, strict sterile technique with maximal barrier precautions during placement, chlorhexidine skin antisepsis, optimal catheter site selection, and daily review of line necessity ■ Additionally, staff education and training, interdisciplinary collaboration, maintaining the site properly, minimizing the number of times the system is opened, using sutureless securement devices, cleansing patients with chlorhexidine baths, changing the tubing system no more frequently than every 72 to 96 hours, aseptic treatment of tubing infusion ports, and aseptic treatment of medications and fluids given to the patient are recommended

Right Atrial PRessure Variation

■ Although the RAP is less predictive of responsiveness to fluid resuscitation, assessing the degree of change with respiration has the potential to be a useful indicator of responsivenes ■ A change >1 mmHg with inspiration is indicative of a positive responder, whereas a change of RAP of less than 1 mm Hg is likely to be a nonresponder.

Stroke volume variation

■ Assessment of SV variability requires an arterial line, a specialized transducer, and the use of a pulse contour device such as the FloTrac (discussed in the next section). ● only predictive in the patient who is mechanically ventilated in a controlled mode with tidal volumes of more than 8 mL/kg with constant respiratory rates

Arterial pulse pressure variation

■ Changes in arterial pressure with inspiration and expiration can be used to gauge fluid responsiveness or preload responsiveness ■ Arterial pulse pressure is defined as the difference between arterial systolic and diastolic pressure measurements. ● The arterial pulse pressure is affected by three variables: SV, resistance, and compliance. ■ A pulse pressure variation (PPV) of more than 10% to 12% is predictive of a patient's ability to respond to fluid resuscitation.

Systolic pressure variation

■ Patients receiving positive pressure ventilation have a decrease in SV with inspiration that ultimately leads to a decrease in systolic blood pressure. ■ The normal systolic pressure variation is 8 to 10 mm Hg. ● A change of greater than 10 mm Hg is indicative of a patient who is preload responsive, and for whom fluid resuscitation is needed ■ The limitation to this strategy is that it requires the patient to be mechanically ventilated in a strict volume control mode

invasive catheter

■ The catheter can be placed into an artery, a vein, or the heart. ■ An arterial catheter consists of a relatively small-gauge, short, pliable catheter that is placed over a guidewire or in a catheter-over-needle system. ● Central venous pressure or ScvO2 monitoring is obtained through a central venous catheter (CVC), most commonly placed in the subclavian or internal jugular vein

bedside monitoring system

■ Visual display of waveforms and numeric information generated by the transducer and have the ability to store and record data

pressurized flush system

■ maintains patency of the pressure tubing and catheter ● 0.9 NS ■ The flush solution is placed in a pressure bag that is inflated to 300 mm Hg to ensure a constant flow of fluid through the pressure tubing. ■ The rate of fluid administration varies from 2 to 5 mL/hr per lumen.

jugular venous pressure

■ provides an estimate of intravascular volume, and it is an indirect measure of CVP - Jugular venous distension occurs when the CVP is elevated, which can occur with fluid overload, right ventricular dysfunction, superior vena cava obstruction, and right heart failure.

low pressure

■ seen in relative hypovolemia as a result of vasodilation from rewarming, medications, or sepsis. In all of these conditions, a decreased RAP reflects blood return to the heart that is insufficient to meet the body's requirements.

transducer with a stopcock

■ translates intravascular pressure changes into waveforms and numeric data ■ A three-way stopcock attached to the transducer is generally used as the reference point for zeroing and leveling the system

high-pressure noncompliant tubing

■ used to minimize artifact and increase the accuracy of the data transmission ■ Noncompliant tubing allows for the efficient and accurate transfer of intravascular pressure changes to the transducer and the monitoring system ● Length no longer than 36-48 inches

high RAP

○ A high RAP measurement indicates conditions that reduce the right ventricle's ability to eject blood, thereby increasing right ventricular pressure and RAP. ■ Such conditions include hypervolemia (seen with aggressive administration of intravenous fluids), severe vasoconstriction, and mechanical ventilation (additional positive pressure increases RAP).

clinical considerations

○ Abnormalities in RAP are generally caused by any condition that alters venous tone, blood volume, or right ventricular contractility.

nursing implications

○ Accuracy in hemodynamic monitoring is essential for ensuring clinically relevant decision making and proper patient management ○ Four major components for validating the accuracy of hemodynamic monitoring systems are: pt positioning, leveling, zeroing, performing the square wave test

Doppler Technology Methods of hemodynamic assessment

○ Echocardiography that uses Doppler technology has been the most commonly used method to measure SV; however, it is expensive, requires technical expertise, and is usually a one-time measurement.

hormonal influences

○ NE increases HR and myocardial contractility and causes vasoconstriction ○ Epinephrine stimulates alpha-adrenergic receptors ○ Atrial natriuretic peptides and brain natriuretic peptides are secreted in response to stretch from the heart chambers ■ ANPS and BNPs cause vasodilation and diuresis, inhibit the sympathetic response and the RAAS to decrease circulating blood volume and decrease stress on the myocardium

nursing imp

○ The critical care nurse is responsible for collecting and recording patient data, ensuring the accuracy of the data, and reporting abnormal findings and trends to the provider.

Pulse contour methods of hemodynamic assessment

○ They can provide SVV and PPV data, and are better predictors of fluid responsiveness in mechanically ventilated patients than a static measurement of RAP or PAOP ○ provides an alternative to the PA catheter for measuring CO, even in patients who are hemodynamically unstable ○ The continuous measurement of SVV and PPV is only possible under full mechanical ventilation ○ SV optimization can be used clinically to determine preload responsiveness and treat patients with low SV or a low FTc.

indications for invasive

○ shock, cardiac tamponade, ruptured ventricular septum, heart failure, and right ventricular infarction. ○ Complex surgical patients

clinical considerations

○ used to estimate the preload of the left heart, just as RAP/CVP is used to measure preload of the right heart

heart

● 4-chambered organ ● Responsible for pumping oxygenation blood and receiving deoxygenated blood ● Two atrioventricular (AV) valves (tricuspid and mitral) open during ventricular diastole, allowing blood to flow from the atria into the ventricles. ● As the ventricles begin to contract in systole, the AV valves close and the semilunar valves (pulmonic and aortic) open, allowing blood to flow into the pulmonary and systemic vasculature

blood

● 7% of our body weight, 5 L of blood The fluid component, or plasma, makes up approximately 60% of the blood volume. The remaining 40% consists of the cellular components: erythrocytes (red blood cells), leukocytes (white blood cells), and platelets

A nurse-driven protocol to determine fluid needs and evaluate the patient for other alterations can be effective

● After giving a fluid challenge of either crystalloids or colloids, assess SV response. ● If SVs improves by at least 10%, continue giving fluid boluses until the SV response is less than 10%. ● If no response is noted after fluid administration, collaborate with the physician to determine if other therapies are needed to correct a high afterload state (vasodilators), low contractility state (inotropic agents), or low afterload state (vasopressors).

compliactions of RAP

● CLABSIs ● Other complications may occur during insertion, including carotid puncture, pneumothorax, hemothorax, perforation of the right atrium or ventricle, and cardiac dysrhythmias. - Obtain a chest radiograph after insertion to confirm placement and detect complications.

nursing implications

● Document assessment of the extremity regularly for perfusion: color, temperature, sensation, pulse, and capillary refill (normal time to refill is less than 3 seconds). ● Keep the patient's wrist in a neutral position and place it on an armboard (radial artery catheters). ● When the catheter is removed, ensure that adequate pressure is applied to the insertion site until hemostasis is obtained (for a minimum of 5 minutes for radial artery catheters). The time required varies depending on the type, size, and location of the catheter and on the patient's coagulation status. Never administer medications via an arterial line because of potential harmful complications.

noninvasive blood pressure

● Ease of use ● Quick availability ● Minimal patient complications ● Problems: improper cuff size (small- false elevation, big- falsely low) ● Pt who are hemodynamically unstable cannt be assessed adequately by NIPB

age

● Elasticity and compliance decrease causing pressure in the arterial system to increase...resulting in systemic HTN ● Left ventricule stiffens, diastolic filling is impaired and leads to left ventricular hypertrophy

pt positioning

● Hemodynamic data can be accurately measured with the patient supine or lateral and with the head of the bed (HOB) flat or elevated as long as the air-fluid interface used to zero the transducer is level to the *phlebostatic axis.* ● HOB to 30 is important for preventing infection

ARTERIAL PRESSURE

● Indicated for patients at risk for compromised tissue perfusion ○ Other indications: the need for frequent laboratory testing, including arterial blood gas sampling, hypotension or hypertension, and monitoring response to vasoactive medications ● involves cannulating an artery and recording pressures via the fluid-filled monitoring system ○ Preferred site: radial artery ○ Assess collateral circulation of the artery with the Allen or modified Allen test ○ More accurate than noninvasive

continuous CO

● Measurement of CCO is based on the same principles as TdCO. ● The CCO system uses a modified PA catheter and a CO computer specific to the device. ● The specialized catheter has a copper filament near the distal end that delivers pulses of energy at prescribed time intervals and warms the blood in the right ventricle. ○ This temperature change is detected by the thermistor at the tip of the catheter approximately every 3 to 6 seconds. ○ The computer interprets the temperature change and averages the CO measurements over the last 60 seconds.

lactate

● Normal arterial lactate levels range from 0.5 to 1.6 mEq/L - Lactate levels may be measured to determine tissue hypoperfusion in shock, to establish adequacy of resuscitation, and to assist in diagnosis of patients who have metabolic acidosis of unknown cause

pulmonary artery pressures

● Pulmonary artery catheters are used to diagnose and manage a variety of conditions in critically ill patients. ○ Thermodilution PA catheters with ability to obtain PA pressures and CO measurement became the gold standard to which all new hemodynamic monitoring methods are compared ● In the last 30 years, the PA catheter has been redesigned to obtain a variety of hemodynamic parameters, including measurements of continuous cardiac output (CCO), right ventricular end diastolic volume, right ventricular ejection fraction, and SvO2.

function

● Regulation of CV Function ● CV system is regulated by hormonal influences

nursing implications

● Routinely monitor RAP, PAP, and PAOP to identify trends and the clinical significance of the values. ● The catheter position must be maintained in the PA. ○ Assess placement and review chest radiograph results, monitor for normal PA waveforms, and ensure that the balloon is deflated except during PAOP measurements. ● Determine how much air is needed to obtain the PAOP (≤1.5 mL) and record this value.

Stroke Volume Optimization

● SV assessment may be more reliable than static measures of pressure such as RAP, PAOP, and MAP to determine cardiac performance and the need for fluids and vasoactive medications ● The first step in a hemodynamic assessment is to determine whether the patient requires fluid to optimize preload and allow the heart to pump more efficiently. ● The fundamental reason to give intravenous fluids is to increase SV.

Cardiovascular System

● System of closed network of arteries, capillaries, and veins that delivers blood, oxygen, hormones and nutrients to tissues by the pumping of the heart ● Wastes are removed via the liver and kidneys

CO monitoring

● The CO is the amount of blood ejected by the heart each minute and is calculated from the heart rate and SV. ○ Cardiac index (CI) is the CO adjusted for an individual's size or body surface area. ○ Monitoring of CO and CI is done to assess the heart's ability to pump oxygenated blood to the tissues.

PA catheter

● The PA catheter is designed to estimate left ventricular filling pressure. ○ Several pressures and parameters are measured or calculated by the PA catheter: RAP; PA systolic (PAS), PA diastolic (PAD), and mean PA pressures (PAPm); PAOP; pulmonary and systemic vascular resistance; and CO. SvO2 is measured if a fiberoptic catheter is inserted. ● The PAS is the peak pressure as the right ventricle ejects its SV, and reflects the amount of pressure needed to open the pulmonic valve to pump blood into the pulmonary vasculature. ● The PAD represents the resistance of the pulmonary vascular bed as measured when the pulmonic valve is closed and the tricuspid valve is opened. ● The PAPm is the average pressure exerted on the pulmonary vasculature. The normal PAP (PAS/PAD) is approximately 25/10 mm Hg, and the PAPm is 15 mm Hg

RAP

● The RAP is obtained from a central line inserted into the superior or inferior vena cava. ● During right ventricular diastole, the tricuspid valve is open, thereby allowing a clear passage for blood to flow from the right atrium to the right ventricle. Therefore RAP provides a reliable measurement of right ventricular preload. ● Right atrial pressure, along with other measurements, is used to assess and guide fluid resuscitation and estimate right-sided cardiac function.

CO

● The amount of blood pumped each minute ● CO = HR x SV ○ HR is a major determinant of CO ■ Fast heart rates result in less diastolic time and can result in poor ventricular filling

zeroing the transducer

● The effects of atmospheric pressure on the fluid-filled hemodynamic monitoring system must be negated for accurate measurements. ● To accomplish this task, open the zeroing stopcock of the transducer to air (closed to the patient) and calibrate (zero) the monitoring system to read a pressure of 0 mm Hg.

hemodynamic monitorying

● The goal in evaluating hemodynamic data is to determine if oxygen supply is meeting oxygen demands. The hemodynamic assessment aids in surveillance and early detection of oxygen imbalance, quantifying the severity of disease, and as a guide for assessing and adjusting therapies

Balancing Oxygen Delivery and Oxygen Demand

● The primary goal in caring for the critically ill is to determine whether oxygen delivery is meeting the oxygen and metabolic demands of the patient. ● Two invasive techniques are also available for clinical determination of venous oxygen saturation: SvO2 and ScvO2.

leveling the air-fluid interface (zeroing stopcock) to the phlebostatic axis

● The zeroing stopcock of the transducer system must be positioned at the level of the atria for accurate readings. ● This external anatomic location is termed the phlebostatic axis, and it is located by identifying the fourth intercostal space at the midway point of the anterior-posterior diameter of the chest wall ○ if the transducer is above the phlebostatic axis, a false low reading results

thermodilution CO

● To measure the CO via the TdCO method, the thermistor connector on the PA catheter is attached to a CO module on the cardiac monitor. ○ A set volume (5-10 mL) of room temperature solution of 0.9% normal saline is injected quickly and smoothly via the proximal port. ○ As the fluid bolus passes into the right ventricle and subsequently the PA, the difference in temperature is sensed by the thermistor located at the distal portion of the catheter ● TdCO measurement is least accurate in patients with a low CO state and most accurate in a high CO state

■ assessing dynamic responsiveness (performing the square wave test)

● To verify that the transducer system accurately represents cardiovascular pressures, perform the dynamic response, or square wave, test. This test is done by recording the pressure waveform while activating the fast flush valve/actuator on the pressure tubing system for at least 1 second. The resulting graph should depict a rapid upstroke from the baseline with a plateau before returning to the baseline (i.e., a square wave).

RAP/CVP

● Used to estimate central venous blood volume and right heart function ○ The pressure is obtained from the right atrial port of a pulmonary artery catheter (PAC) and is also called the RAP ○ Assesses preload of the right side of the heart ○ Normal RAP/CVP is 2-6 mmHg

stroke volume

● is the amount of blood ejected by the heart with each beat ○ Affected by preload, afterload, and contractility

afterload

● the amount of resistance the ventricles must overcome to deliver the SV into the receiving vasculature

preload

● the degree of ventricular stretch before the next contraction ● The degree of stretch is directly affected by the amount of blood volume present in the ventricles at end-diastole ○ Based on the Frank-Starling mechanism, when ventricular fibers are at maximal stretch, maximal CO results.

contractility

● the strength of myocardial muscle fiber shortening during the systolic phase of the cardiac cycle ● The preload influences contractility because optimizing the preload ensures maximal stretch of the myocardial fibers according to the Frank-Starling law.

RAP waveform

● three major waveforms: a, c, and v waves ○ The a wave is produced by atrial contraction and follows the P wave on the ECG tracing. ○ The c wave is produced by closure of the tricuspid valve and follows the R wave. ○ Finally, the v wave correlates with right atrial filling and right ventricular systole; it follows the T wave on the ECG.