Advanced Hemodynamics - Orlando Health

More documents

Recommendations

Info

Advanced Hemodynamic Monitoring measure the pressure required to fill the ventricles as a measure of left ventricular end-diastolic volume (LVEDV) or fiber length. Left ventricular preload can also be clinically assessed via the pulmonary artery (PA) catheter by obtaining the pulmonary artery wedge pressure (PAWP), also known as the pulmonary artery occlusion pressure (PAOP), more commonly referred to as the “wedge” pressure. Normal PAWP/PAOP can range from 6-12 mm Hg. Right ventricular preload is assessed by obtaining the central venous pressure (CVP). A normal CVP can be from 0-8 mm Hg. Generally speaking, lower values may indicate hypovolemia or extreme venodilation, and vice versa for higher values. Frank-Starling’s Law The Frank-Starling Law describes the relationship between myocardial muscle length and the force of Starling’s Curve contraction. The amount of stretch is directly affected by the amount of fluid volume in the ventricle, thus preload is most directly related to fluid volume. Starling’s Curve describes the relationship of preload to cardiac output. As preload (fluid volume) increases, cardiac output will also increase until the cardiac output levels off. If additional fluid is added after this point, cardiac output begins to fall. This reaction of the heart muscle to stretch can be likened to a slingshot. The farther the slingshot is stretched, the farther it propels a stone. If the slingshot is only slightly stretched, the stone will travel a very short distance. If the slingshot is repeatedly overstretched, however, it weakens and eventually loses its ability to launch the stone at all. The slingshot functions best when it is stretched just the Preload right amount, neither too little nor too much. The same is true of the heart. With too little preload the cardiac output cannot propel enough blood forward. With too much preload the heart will become overwhelmed, leading to failure. Afterload Afterload refers to the resistance, impedance, or pressure that the ventricle must overcome to eject its own volume. Afterload can also be viewed as the resistance of flow, or how clamped the blood vessels are, affecting how hard the heart (right or left) has to pump to push the blood out. In the clinical setting the most sensitive indicator of left ventricular afterload is the systemic vascular resistance (SVR), and for right ventricular afterload it is pulmonary vascular resistance (PVR). The normal value for the SVR is 800-1200 dynes/sec/cm. This value can also be corrected for body surface area and is termed the systemic vascular resistance index (SVRI), for which the normal values are 1680-2580 dynes/sec/cm5/m2. The normal values for the PVR is generally less than 250 dynes/sec/cm5, and the PVRI approximately 255-285 dynes/sec/cm5/m2. Generally speaking, higher values indicate vasoconstriction and lower values indicate vasodilation. Contractility Contractility is the force and velocity with which the ventricular ejection occurs independent of the effects of preload and afterload. In other words, think of contractility as the cardiac “squeeze”. Contractility is primarily influenced by the effects of the sympathetic nervous system. Factors such as the release of catecholamines from fear, stress, anxiety, pain, or hypovolemia can increase Copyright 2010 Orlando Health, Education & Development 5 Cardiac Output
Advanced Hemodynamic Monitoring contractility causing the heart to “squeeze” harder. The ventricular stroke work index (VSWI) is a useful measurement for myocardial contractility. Normal values for the left VSWI (LVSWI) are 35- 85 gm/m2/beat. Compliance Myocardial compliance refers to the ventricle’s ability to stretch to receive a given volume of blood. Normally the ventricle is very compliant so large changes in volume will produce small changes in pressure. If compliance is low, small changes in volume will result in large changes in pressure within the ventricle (refer back to the illustration of Starling’s curve). If the ventricle cannot stretch, it will be unable to increase cardiac output with increased preload as described by the curve. Arterial Blood Oxygen Content Hemoglobin carries 97% of oxygen and 2% is dissolved in plasma. Together, oxygen bound to hemoglobin and oxygen dissolved in plasma, is called arterial oxygen content or CaO 2 = (Hgb x 1.34 x SaO 2 ) + (0.003 x PaO 2 ). Hemoglobin can carry 1.34 ml of oxygen per gram of hemoglobin. Oxygen does not dissolve very well in plasma as evidenced by a solubility coefficient of 0.0031. Therefore, hemoglobin has the largest influence on CaO 2 . Saturation of hemoglobin indicates how much oxygen is being carried on the hemoglobin. Normal oxygen saturation of a healthy individual ranges from 97% to 99%. A value of 95% is still clinically acceptable with a normal hemoglobin. These readings have to be considered in relation to the oxyhemoglobin dissociation curve. The oxyhemoglobin dissociation curve indicates the relationship between oxygen saturation of hemoglobin and the partial oxygen pressure, and how it releases oxygen to the tissues or how it retains oxygen on the hemoglobin. Copyright 2010 Orlando Health, Education & Development 6
Page 1 and 2: Advanced Hemodynamics Self-Learning
Page 3 and 4: Purpose Advanced Hemodynamic Monito
Page 5: Advanced Hemodynamic Monitoring the
Page 9 and 10: Advanced Hemodynamic Monitoring Oxy
Page 11 and 12: Advanced Hemodynamic Monitoring Con
Page 13 and 14: Line Setup & Zeroing of a Transduce
Page 15 and 16: PAC Insertion Advanced Hemodynamic
Page 17 and 18: Advanced Hemodynamic Monitoring Sec
Page 19 and 20: Advanced Hemodynamic Monitoring for
Page 21 and 22: Advanced Hemodynamic Monitoring
Page 23 and 24: Advanced Hemodynamic Monitoring Com
Page 25 and 26: Advanced Hemodynamic Monitoring Alt
Page 27 and 28: Advanced Hemodynamic Monitoring The
Page 29 and 30: Advanced Hemodynamic Monitoring tem
Page 31 and 32: Advanced Hemodynamic Monitoring Pul
Page 33 and 34: Advanced Hemodynamic Monitoring SV
Page 35 and 36: Advanced Hemodynamic Monitoring The
Page 37 and 38: Advanced Hemodynamic Monitoring Aft
Page 39 and 40: Advanced Hemodynamic Monitoring Hem
Page 41 and 42: Post Test Advanced Hemodynamic Moni
Page 43 and 44: Advanced Hemodynamic Monitoring C.
Page 45 and 46: Advanced Hemodynamic Monitoring Ref
Page 47 and 48: Advanced Hemodynamic Monitoring Lit
Page 49: Advanced Hemodynamic Monitoring Hea

Advanced Hemodynamics - Orlando Health

Create successful ePaper yourself

Delete template?

Save as template?