Invasive Monitoing Lecture-1.pptx

Invasive Monitoring & Vascular Access Techniques Christopher Simons, DNAP, CRNA [email protected] Making patient safet Outline of Today’s Presentation Making patient safet 2 Main Topics INVASIVE ARTERIAL BLOOD PRESSURE MONITORING CARDIAC OUTPUT MONITORING Making patient safet 1. Invas...

Invasive Monitoring & Vascular Access Techniques Christopher Simons, DNAP, CRNA [email protected] Making patient safet Outline of Today’s Presentation Making patient safet 2 Main Topics INVASIVE ARTERIAL BLOOD PRESSURE MONITORING CARDIAC OUTPUT MONITORING Making patient safet 1. Invasive Arterial Blood Pressure Monitoring Making patient safet Main Objectives 1. 2. 3. 4. 5. 6. List indications and contraindications for invasive arterial blood pressure monitoring Compare and contrast radial, brachial, and femoral sites for invasive arterial blood pressure monitoring List 3 methods for percutaneous insertion of an arterial cannula Describe technical aspects of arterial pressure monitoring in the operating room List methods for troubleshooting the direct pressure monitoring system Recognize normal and abnormal arterial pressure waveforms Making patient safet Do arterial lines save lives? Making patient safet   Direct measurement of arterial BP is considered by many to be the GOLD STANDARD for recording BP Offers many advantages DESPITE its increased Risk Cost Need for technical expertise for placement and management Making patient safet 1. List of indications for invasive arterial blood pressure monitoring Anticipated Blood Pressure Instability (cardiac surgery, trauma surgery, major vascular surgery, transplant, etc.) Major end-organ disease Need for repeated blood sampling Noninvasive BP failure Supplementary diagnostic information from the arterial waveform Intra-op emergency Making patient safet 1. List of absolute contraindications for invasive arterial blood pressure monitoring Absent pulse at the anatomical location (i.e. hx of radial arterial harvesting for CABG) Avoid cannulation in patients with documented compromised collateral blood flow (Failed Allen’s Test***) Preexisting vascular insufficiency (Raynaud’s Syndrome, Thromboangiitis obliterans) Full thickness burns over the proposed site of cannulation ***Studies have found no objective evidence that noninvasive determination of collateral flow before the catheter is inserted, such as the Allen test, was of any value in predicting morbidity. Making patient safet 1. List of relative contraindications for invasive arterial blood pressure monitoring Local infection at cannulation site Coagulopathy Moderate or severe atherosclerosis Second or third-degree burns at the cannulation site Artificial vascular graft in the area Cannulation site within the proposed surgical field Making patient safet Complications Hematoma, Vasospasm, Air embolism Ischemia to distal limbs/digits (poor collateral flow) Damage to adjacent nerves/veins (Peripheral neuropathy) Hemorrhage Infection (local and systemic) Misinterpretation of data (misplaced transducer) Misuse of equipment (intraarterial injection of drugs) Making patient safet Complications Making patient safet  Think risk vs. benefit  Less than 1% chance for major complications with arterial cannulation Making patient safet 2. Compare and contrast radial, brachial, and femoral sites  Radial Artery Most common site for invasive blood pressure monitoring because of its consistent anatomical accessibility, ease of cannulation, and relatively low rate of complications Ulnar artery provides sufficient collateral flow Radial arterial pressure reflects aortic pressure well in young, healthy, individuals Colateral flow from the palmar arch Making patient safet Making patient safet 2. Compare and contrast radial, brachial, and femoral sites  Brachial Artery While lacking collateral branches to protect the hand, has a long track record of safe use. A slightly longer catheter is preferred due to their relatively deeper and more mobile anatomic locations. Increased risk of cerebral embolization when more central vessels are utilized. Making patient safet 2. Compare and contrast radial, brachial, and femoral sites  Femoral Artery The femoral artery is the largest vessel in common use for blood pressure monitoring, but its safety profile seems comparable to other sites Catheterization is best achieved with a guidewire technique Point of entry must be distal to the inguinal ligament to minimize the risk of arterial injury, hidden hematoma formation, or even uncontrolled hemorrhage into the pelvis or retroperitoneum Making patient safet 2. Compare and contrast radial, brachial, and femoral sites Overall, no evidence has suggested that one cannulation site —radial, ulnar, brachial, axillary, femoral, or dorsalis pedis—was safer than another, except perhaps from an infectious disease viewpoint. As the location of the catheter becomes more peripheral, measured systolic pressure tends to increase and diastolic pressure tends to decrease as a result of resonance effects in the arterial tree. Mean pressure decreases only slightly. Making patient safet 3. List 3 methods for percutaneous insertion of an arterial cannula. Guidewire Seldinger technique Direct insertion or “catheter over needle” Transfixion (modified Seldinger) Making patient safet Guidewire Seldinger technique Most common and recommended technique Performed by accessing the artery with a needle, feeding a guidewire through the lumen of the needle, and finally placing the catheter in the lumen of the artery by feeding it over the guidewire and removing the guidewire leaving only the catheter itself in place. Making patient safet Direct insertion Basic and can be performed via accessing the artery with a needle that includes an integrated catheter that is easily advanced into the lumen of the vessel following arterial access Once the artery has been accessed and the catheter placed in the lumen, the needle is completely removed leaving only the catheter in place Making patient safet Transfixion Also known as “modified Seldinger” technique It is usually used with “cannula over needle” kits combined with a guidewire The modified Seldinger technique uses an integrated needlecatheter-wire system Making patient safet Transfixion 1. 2. 3. 4. 5. The artery is accessed, and pulsatile blood flow is confirmed The needle is advanced until blood flow is obtained A guidewire is then threaded through the cannula The needle is withdrawn, leaving the cannula in situ The arterial catheter is then inserted using a conventional Seldinger technique Making patient safet Ultrasound Guidance The first new “technique” in arterial cannulation in decades Not as standard as it is with central lines, due to the lower rate of insertionrelated complications with arterial lines The use of ultrasound guidance does not obviate the need for a sound knowledge of anatomy or protect inexperienced practitioners from the risk of complications. However, ultrasound guidance has been demonstrated to increase the success rate, decrease the number of “passes” and decrease procedure time for practitioners who are already proficient with the palpation method Making patient safet 4. Describe technical aspects of arterial pressure monitoring in the operating room Most invasive blood pressure monitoring systems are underdamped, second-order dynamic systems that demonstrate simple harmonic motion dependent on elasticity, mass, and friction These three properties determine the system operating characteristics or dynamic response Dynamic response is characterized by natural frequency and damping coefficient Making patient safet 4. Describe technical aspects of arterial pressure monitoring in the operating room Natural Frequency Making patient safet Natural Frequency The displayed pressure waveform is a periodic complex wave produced via Fourier analysis of a summation of multiple propagated and reflected pressure waves, or harmonics Meaning…it is a mathematical re-creation of the original complex pressure wave created and propagated by stroke volume ejection Making patient safet Natural Frequency A Harmonic is a multiple of the fundamental frequency. For example, if the fundamental frequency is 25 Hz, the harmonics will be 50 Hz, 75 Hz, 100 Hz, etc. 6-10 harmonics are needed to most accurately create the arterial pressure waveform Example: Pulse Rate 120 BPM = 2 cycles/sec or 2 Hz 6-10 waveforms x 2Hz = 12-20Hz Arterial Transducer Systems have a natural frequency > 12Hz If your pulse rate is 160 your arterial wave form is less accurate? Same with a low HR?? Making patient safet Summary The faster the heart rate and the steeper the systolic pressure upstroke, the greater the demands on the monitoring system The highest possible natural frequency of the system yields the optimal result. Best achieved by: Using short lengths of stiff pressure tubing Limiting additions or connections to the system such as stopcocks Making patient safet 4. Describe technical aspects of arterial pressure monitoring in the operating room Damping coefficient Making patient safet Damping coefficient Damping is an influence within an oscillatory system that has the effect of reducing, restricting, or preventing oscillations. When pressure monitoring equipment for invasive pressure monitoring is exposed to pressure waves, it too can oscillate, and can be detected along with the blood pressure waves. This is Resonance Making patient safet Damping coefficient An underdamped system may combine elements of the measurement system itself with the measured sine waves and display systolic pressure overshoot An overdamped waveform exhibits a slurred upstroke, absent dicrotic notch, and loss of fine detail Making patient safet Damping coefficient Making patient safet Summary Dampening Coefficient Too Low = Underdamped = Overestimation of BP Too High = Overdamped = Underestimation of BP While adding an air bubble to the monitoring system will increase damping, it simultaneously lowers natural frequency and may increase the intrinsic system resonance and worsen systolic pressure overshoot Making patient safet 5. List methods for troubleshooting the direct pressure monitoring system Damping Making patient safet 5. List methods for troubleshooting the direct pressure monitoring system Overdamped Fine detail lost and trace looks flat On square wave test – no oscillations Underdamped Lots of artefacts present On square wave test – multiple oscillations Making patient safet 5. List methods for troubleshooting the direct pressure monitoring system Causes of overdamping (underestimating BP) can include: Loose connections (usually the most common-not enough pressure ) Air bubbles Kinks Blood clots Arterial spasm Narrow tubing Making patient safet 5. List methods for troubleshooting the direct pressure monitoring system Causes of underdamping (falsely elevated BP) can include: Catheter artifact Hypothermia (vasoconstriction causes systolic pressure in the radial artery to exceed that in the femoral artery) Tachycardia or arrhythmias Making patient safet 5. List methods for troubleshooting the direct pressure monitoring system Zeroing & Leveling Making patient safet 5. List methods for troubleshooting the direct pressure monitoring system “Zero-ing” – important to ensure transducer zeroed. This ensures that the transducer references atmospheric pressure as zero. Anywhere in the room Transducer height (levelling) – needs to be at level of right atrium (phlebostatic axis). For every 10 cm below the phlebostatic axis the transducer will add 7.4 mmHg of pressure and vice versa. 1 cm =.74 mmHg (how much you lose) Or 1 cm / 1.34 = x mmHG Making patient safet 5. List methods for troubleshooting the direct pressure monitoring system In specific circumstances, clinicians may choose to place the transducer at a level different from the standard For example, during a sitting neurosurgical procedure, it may be more informative to place it at the level of the patient’s ear to approximate the level of the Circle of Willis. Making patient safet 6. Recognize normal and abnormal arterial pressure waveforms Normal Waveforms Making patient safet 6. Recognize normal and abnormal arterial pressure waveforms The systolic phase, characterized by a rapid increase in pressure to a peak, followed by a rapid decline The dicrotic notch*** The diastolic phase, which represents the run-off of blood into the peripheral circulation ***widely believed to be the effect of the aortic valve closing, actually the offspring of several reflected waves, only vaguely related to the behavior of the aortic valve. Making patient safet 6. Recognize normal and abnormal arterial pressure waveforms The peak correlates with the systolic blood pressure The trough is the diastolic pressure The mean arterial pressure (MAP) is calculated from the area under the pressure curve Making patient safet 6. Recognize normal and abnormal arterial pressure waveforms Abnormal Waveforms Making patient safet 6. Recognize normal and abnormal arterial pressure waveforms 1. 2. 3. 4. 5. Aortic Stenosis Aortic Regurgitation Hypertrophic cardiomyopathy Systolic left ventricular failure Cardiac tamponade Making patient safet 6. Recognize normal and abnormal arterial pressure waveforms 1. Aortic Stenosis Pulsus parvus (narrow pulse pressure) Pulsus tardus (delayed upstroke) you’re building up pressure Making patient safet 6. Recognize normal and abnormal arterial pressure waveforms 2. Aortic Regurgitation Bisferiens pulse (double peak) Wide pulse pressure Making patient safet 6. Recognize normal and abnormal arterial pressure waveforms 3. Hypertrophic cardiomyopathy Spike and dome (midsystolic obstruction) Making patient safet 6. Recognize normal and abnormal arterial pressure waveforms 4. Systolic left ventricular failure Pulsus alternans (alternating pulse pressure amplitude) Possible hypoventilation? Making patient safet 6. Recognize normal and abnormal arterial pressure waveforms 5. Cardiac tamponade Pulsus paradoxus (exaggerated decrease in systolic blood pressure during spontaneous inspiration) Intrathoracic pressure stays conistnet with Making patient safet Making patient safet 2. Cardiac Output Monitoring Making patient safet Main Objectives 1. 2. 3. 4. 5. 6. List indications, contraindications, and complications of central venous cannulation List advantages and disadvantages of the most used sites (internal jugular, subclavian, and femoral vein) for central venous cannulation in the perioperative period Compare and contrast landmark and ultrasound-guided techniques for internal jugular vein cannulation Interpret normal and abnormal central venous pressure waveforms List indications, contraindications and complications of pulmonary artery catheterization Describe techniques for assessment of cardiac function in the perioperative period Making patient safet  Do central lines save lives?  Central lines are not benign Making patient safet 1. List of indications for central venous cannulation CVP monitoring Pulmonary artery catheterization and monitoring Transvenous pacing Temporary Hemodialysis Aspiration of air emboli Inadequate peripheral IV access Sampling site for repeated blood testing Making patient safet 1. List of indications for central venous cannulation cont. Drug administration Concentrated vasoactive drugs Chemotherapy Agents irritating to peripheral veins Prolonged antibiotic or TPN administration Rapid infusion of fluid Trauma Major surgery Making patient safet  If you need to resuscitate, which would you rather have? Making patient safet  If you need to resuscitate, which would you rather have? Making patient safet 1. List of contraindications for central venous cannulation Coagulopathy (relative contraindication) Infection at the insertion site History of surgical manipulation or trauma at insertion site Trauma to nearby structures Cervical collar for IJ catheter Pelvic binder for femoral catheter Making patient safet 1. List of complications for central venous cannulation  Mechanical Vascular Injury Arterial** Venous Cardiac tamponade^^ Respiratory compromise Pneumothorax / hematoma formation Nerve Injury Arrhythmias Making patient safet 1. List of complications for central venous cannulation  Thromboembolic Venous thrombosis Pulmonary embolism Arterial thrombosis / embolism Catheter or guidewire embolism Making patient safet 1. List of complications for central venous cannulation  Infections** Insertion site infection Catheter infection Blood stream infection Endocarditis Making patient safet 1. List of complications for central venous cannulation  Misinterpretation of data That’s you!  Misuse of equipment Making patient safet 2. List advantages and disadvantages of the most used sites for central venous cannulation  Selecting the best site for cannulation requires: The Why Monitoring vs fluid administration The Patient’s Condition The Skill and experience of the clinician Making patient safet 2. List advantages and disadvantages of the most used sites for central venous cannulation  Right Internal Jugular Vein (IJ) Consistent, predictable anatomic site Short, straight course to the vena cava Highly accessible during surgery Recommended if transvenous pacing is required High success rate (90-99%) Making patient safet 2. List advantages and disadvantages of the most used sites for central venous cannulation  Left Internal Jugular Vein (IJ) Increased risk of pneumothorax (pleura higher of left side) Typically smaller than Right IJ Tends to overlap Carotid more than Right IJ Most practioners have less experience placing on left side Making patient safet 2. List advantages and disadvantages of the most used sites for central venous cannulation  Subclavian Vein (SLC) Good for longer term use (lowest infection rate) Easier cannulation side in case of C-collar Increased patient comfort Increased risk of pneumothorax and arterial puncture Technically challenging Making patient safet 2. List advantages and disadvantages of the most used sites for central venous cannulation  Femoral Vein Good option if others inaccessible (surgical site / trauma) Obviates pneumothorax risk Increased risk of infection Increased risk of vascular / nerve injury & thromboembolic injury Unable to ambulate – prolongs recovery Making patient safet  The length of the catheter inserted to position the tip properly in the superior vena cava will vary according to puncture site Making patient safet 2. List advantages and disadvantages of the most used sites for central venous cannulation  Distance to the junction of Vena Cava and R. Atrium*** Subclavian = 10 cm Right internal jugular = 15 cm Left internal jugular = 20 cm Femoral vein = R. & L. median basilic = 40 cm 40 cm Making patient safet 2. List advantages and disadvantages of the most used sites for central venous cannulation  Distance from the R. IJ to distant cardiac structures Junction of vena cava and R. Atrium = R. Atrium = 15 – 20 cm R. Ventricle = 25 – 35 cm Pulmonary Artery = R. artery wedge position = 15 cm 35 – 45 cm 40 – 50 cm Making patient safet 3. Landmark vs. Ultrasound-guided technique for internal jugular vein cannulation  A central vein may be cannulated using either a landmark technique or ultrasound guidance  Ultrasound technology is now widely available and is strongly recommended for central line placement Making patient safet 3. Landmark vs. Ultrasound-guided technique for internal jugular vein cannulation  Advantages of Ultrasound-guided technique Increased first-attempt success rate Reduced number of puncture attempts Lower mechanical complication rate (arterial puncture, etc.) May result in a lower infection rate Making patient safet 3. Landmark vs. Ultrasound-guided technique for internal jugular vein cannulation  Disadvantages of Ultrasound-guided technique Requires expensive equipment Longer average insertion times Loss of technical abilities when using anatomical landmarks False sense of security Making patient safet 4. Interpret normal and abnormal CVP waveforms Normal Waveform Making patient safet 4. Interpret normal and abnormal CVP waveforms  The CVP waveform consists of five phasic events, three peaks (a, c, v) and two descents (x, y) Making patient safet 4. Interpret normal and abnormal CVP waveforms Making patient safet 4. Interpret normal and abnormal CVP waveforms Making patient safet 4. Interpret normal and abnormal CVP waveforms Making patient safet 4. Interpret normal and abnormal CVP waveforms Making patient safet 4. Interpret normal and abnormal CVP waveforms Making patient safet 4. Interpret normal and abnormal CVP waveforms Abnormal Waveforms Making patient safet 4. Interpret normal and abnormal CVP waveforms Making patient safet 4. Interpret normal and abnormal CVP waveforms 1. Atrial Fibrillation Loss of a wave Because the atrial contraction is responsible for the a wave, loss of atrial contraction results in a missing a wave Making patient safet 4. Interpret normal and abnormal CVP waveforms 2. Atrioventricular dissociation Cannon a wave The atrial contraction occurs at the same time as the ventricular contraction, which results in a fusion of the a and c waves Making patient safet 4. Interpret normal and abnormal CVP waveforms 3. Tricuspid regurgitation Fused c-v waves The backflow of blood out of the right ventricle obliterates the normal x descent. The c wave becomes accentuated and fuses with the v wave Making patient safet 4. Interpret normal and abnormal CVP waveforms 4. Tricuspid stenosis Prominent a waves Tricuspid stenosis produces a large a wave because of increased resistance to flow from the atrium to the ventricle Making patient safet 4. Interpret normal and abnormal CVP waveforms 5. Cardiac Tamponade “Sawtooth” or “M” shape All CVP waveform components are elevated x descent is steep y descent is (usually) absent The diastolic y pressure descent is attenuated or absent, because early diastolic flow from right atrium to right ventricle is impaired by the surrounding compressive pericardial fluid collection Making patient safet 4. Interpret normal and abnormal CVP waveforms Final thoughts on CVP monitoring Making patient safet 4. Interpret normal and abnormal CVP waveforms  To correctly interpret the information provided by CVP monitoring, the clinician must possess a thorough understanding of ALL the variables affecting R. heart pressure  The most important traditional application of CVP monitoring is to provide an estimate of the adequacy of the circulating blood volume Making patient safet 4. Interpret normal and abnormal CVP waveforms  The exact same amount of blood returning to the heart can result in very different CVP values at different cardiac function states  Changes in CVP may be the sole result of changes in inotropic state or compliance of the ventricle, independent of the total circulating volume or venous return to the heart Making patient safet 4. Interpret normal and abnormal CVP waveforms Making patient safet 5. Indications, contraindications and complications of pulmonary artery catheterization Pulmonary Artery Catheters Making patient safet 5. Indications, contraindications and complications of pulmonary artery catheterization  Modern versions of the catheter allow clinicians to monitor central venous pressure (CVP), pulmonary artery pressure (PAP), pulmonary capillary wedge pressure (PCWP), mixed venous oxygen saturation, and patient temperature. Making patient safet 5. Indications for pulmonary artery catheterization Cardiac output measurement Evaluation or diagnosis of pulmonary hypertension Distinguishing septic from cardiogenic shock using mixed venous oxygen saturation (SvO2) Complex hemodynamic instability Severe chronic or potentially reversable heart failure Cardiac / pulmonary transplantation workup Making patient safet 5. List of contraindications for PA catheterization   Absolute Tricuspid or Pulmonary stenosis or prosthesis Right heart mass Endocarditis Transvenous pacing wires in right heart- high likelihood of dislodging the strings Relative Left bundle branch block Bacteremia Making patient safet 5. List of complications for PA catheterization   Catheterization Arrhythmia, v-fib Right bundle branch block (complete if existing LBBB) Mechanical Dislodgment of pacing wires Pulmonary infarction / artery rupture Cardiac valve injury Thromboembolism Making patient safet Insertion  The standard PAC has a 7.0 to 9.0 Fr circumference, is 110 cm in length marked at 10-cm intervals, and contains four internal lumens  The distal port at the catheter tip is used for PAP monitoring, while the second is 30 cm more proximal and is used for CVP monitoring  The third lumen leads to a balloon near the tip which is used to float the catheter through the cardiac chambers  The fourth lumen houses wires for a temperature thermistor, the end of which lies just proximal to the balloon Making patient safet “Floating” the catheter  The PAC is advanced through the introducer sheath until the tip of the PAC is beyond the introducer, typically 20 cm.  Next the balloon is inflated, which allows for blood flow to “direct” the catheter towards the PA, while the catheter is advanced by the operator  As the catheter is carefully advanced, the transduced waveform is carefully observed, while simultaneously appreciating distance of insertion.  Identify wedge pressure waveform and deflate the balloon. Withdraw the catheter 1-2 cm to reduce risk of ischemia or injury. Making patient safet Normal PA Waveforms Making patient safet Normal PA Pressure Values CVP Central Venous Pressure 0-8 mmHg RVP Right Ventricular Pressure 25/5 mmHg PAP Pulmonary Artery Pressure PAOP Pulmonary Artery Occlusion Pressure 5-15 mmHg LVEDP L. Vent. End Diastolic Pressure Cardiac Output = 4-6 L/min 25/10 mmHg 4-12 mmHg Cardiac Index = 2.5-3.5 L/min/m2 Making patient safet Normal PA Waveforms Making patient safet Normal PA Waveforms  As the balloon-tipped PAC is floated to its proper position in the pulmonary artery, characteristic pressure waveforms are recorded  In the superior vena cava or right atrium, a CVP waveform with characteristic a-, c-, and v waves and low mean pressure should be observed  Entry of the PAC into the pulmonary artery is heralded by a stepup in diastolic pressure and a change in waveform morphology Making patient safet Normal PA Waveforms  The wedge pressure is an indirect measurement of pulmonary venous pressure and left atrial pressure  Should therefore resemble these venous waveforms with characteristic a and v waves and x and y descents  Due to the pulmonary vascular bed interposed between the PAC tip and left atrium, wedge pressure is a delayed and damped representation of left atrial pressure Making patient safet Making patient safet Abnormal PA Waveforms  Pathophysiologic conditions involving the leftsided cardiac chambers or valves produce characteristic changes in the pulmonary artery and wedge pressure waveforms Making patient safet Abnormal PA Waveforms  One of the most easily recognized patterns is the tall v wave of mitral regurgitation  The prominent v wave of mitral regurgitation is generated during ventricular systole d/t to the retrograde ejection of blood into the left atrium Making patient safet tall systolic v wave of mitral regurgitation Making patient safet Abnormal PA Waveforms  In contrast to mitral regurgitation, which distorts the systolic portion of the wedge pressure waveform, mitral stenosis alters its diastolic aspect  The holo-diastolic pressure gradient across the mitral valve results in an increased mean wedge pressure, a slurred early diastolic y descent, and a tall end-diastolic a wave Making patient safet In Mitral Stenosis: Mean pulmonary artery wedge pressure (PAWP) is increased (35 mm Hg), and the diastolic y descent is markedly attenuated Making patient safet Abnormal PA Waveforms  Probably the single most important waveform abnormality or interpretive problem in PAC monitoring is discerning the correct pressure measurement in patients with large intrathoracic pressure swings like those receiving positive pressure ventilation Making patient safet Abnormal PA Waveforms  During positive pressure ventilation, inspiration increases pulmonary artery and wedge pressures  By measuring these pressures at end-expiration, the confounding effect of this inspiratory increase in intrathoracic pressure is minimized Making patient safet Abnormal PA Waveforms The most reliable method for measuring central vascular pressures at end-expiration is examination of the waveforms on a calibrated monitor screen or paper recording Making patient safet PA CATHETER-DERIVED HEMODYNAMIC VARIABLES  The cardiovascular system is often modeled as an electrical circuit  The relationship between cardiac output, blood pressure, and resistance to flow related in a manner similar to Ohm’s law: Making patient safet PA CATHETER-DERIVED HEMODYNAMIC VARIABLES  PVR= (MPAP – PAWP) * 80 CO PVR = pulmonary vascular resistance (dyne s/cm5) MPAP = mean pulmonary artery pressure (mm Hg) PAWP = pulmonary artery wedge pressure (mm Hg) CO = cardiac output (L/min) Making patient safet PA CATHETER-DERIVED HEMODYNAMIC VARIABLES  SVR= (MAP – CVP) * 80 CO SVR = systemic vascular resistance (dyne s/cm5) MAP = mean arterial pressure (mm Hg) CVP = central venous pressure (mm Hg) CO = cardiac output (L/min) Making patient safet 6. Techniques for assessment of cardiac function in the perioperative period  Cardiac output is the total blood flow generated by the heart  Measurement of cardiac output provides a global assessment of the circulation Making patient safet 6. Techniques for assessment of cardiac function in the perioperative period  In many critically ill patients, low cardiac output leads to significant morbidity and mortality  Clinical assessment of cardiac output is often inaccurate. Seriously ill patients with decreased cardiac output might have normal systemic arterial blood pressures  Newer techniques for cardiac output measurement are becoming less invasive and thus might provide benefit to many patients without the attendant risks of invasive monitoring Making patient safet Thermodilution Method  Considered the gold standard for measuring cardiac output because of its ease of implementation and the long clinical experience with its use in various settings  A known volume of room temperature fluid is injected as a bolus into the proximal (right atrium) lumen of the PAC, and the resulting change in the pulmonary artery blood temperature is recorded by the thermistor at the catheter tip  Usually, three cardiac output measurements performed in rapid succession are averaged to provide a more reliable result Making patient safet Continuous Thermodilution Method  Newer technologies applied to PAC monitoring allow nearly continuous cardiac output monitoring using warm thermal indicator  The displayed value for cardiac output is updated every 30 to 60 seconds and represents the average value for the cardiac output measured over the previous 3 to 6 minutes  Delayed response during unstable hemodynamic conditions  The CCO computer and catheter require a significant amount of time to warm up and may work poorly in an environment where there is a great deal of thermal noise such as an operating room Making patient safet Esophageal Doppler   Measures Doppler shit of blood flow at the thoracic aorta Advantages Technically simple to use Allows for continuous monitoring of stroke volume  Disadvantages Can be difficult to maintain Doppler window Monitoring only measures a fraction of total cardiac output. “Calibration” constants are accurate for most, but not all, patients Inaccurate with aortic valvular disease Not easily applied in awake patients Making patient safet Bioimpedance CO monitoring  For bioimpedance measurement, disposable electrodes are applied to the skin surface along the sides of the neck and lateral aspect of the costal margin (thoracic bioimpedance) or to the four limbs  A high-frequency, low-amplitude electrical current is applied, and the voltage change is measured  Patient height, weight, and gender are used to calculate the volume of the thoracic cavity  Cardiac output is computed for each cardiac cycle and continuously displayed as an average value over several heart beats Making patient safet Bioimpedance CO monitoring  Advantages Noninvasive Highly accurate in healthy patients  Disadvantages Reliability deteriorates in surgical and critically ill patients Electrodes may become dislodged, rendering the data inaccurate Making patient safet Pulse Contour CO monitoring  Continuous measurement of cardiac output derived from the analysis of the arterial pulse pressure waveform.  Can provide multiple measurements, including cardiac output (CO), stroke volume (SV) and stroke volume variation (SVV)  Patient height, weight, and gender are programmed into the computer to further index cardiac output measurments Making patient safet Pulse Contour CO monitoring  Advantages Continuous, beat-to-beat cardiac output monitoring  Provides multiple measurements to CO, including SV and SVV Disadvantages The use of vasopressors might affect the accuracy of pulse contour methods Requires a well-defined arterial pressure waveform with a discernible dicrotic notch for accurate identification of systole and diastole, a condition that might not exist under severe tachycardia or dysrhythmia, or other very low-output states For a meaningful use of beat-to-beat variation in stroke volume (as well as systolic pressure or PPV), the patient needs to be on controlled mechanical ventilation with a tidal volume of at least 8 mL/kg body weight and to be in a regular cardiac rhythm Making patient safet Pulse Contour CO monitoring  Advantages Continuous, beat-to-beat cardiac output monitoring  Provides multiple measurements to CO, including SV and SVV Disadvantages The use of vasopressors might affect the accuracy of pulse contour methods Requires a well-defined arterial pressure waveform with a discernible dicrotic notch for accurate identification of systole and diastole, a condition that might not exist under severe tachycardia or dysrhythmia, or other very low-output states For a meaningful use of beat-to-beat variation in stroke volume (as well as systolic pressure or PPV), the patient needs to be on controlled mechanical ventilation with a tidal volume of at least 8 mL/kg body weight and to be in a regular cardiac rhythm Making patient safet