Critical Care Nursing Program August to November, 2015 Full-time Lesson A13 Pumping and Perfusion III Basic Hemodynamic Monitoring August 2015 RN Professional Development Centre Page 1
Lesson Thirteen Pumping and Perfusion III Basic Hemodynamic Monitoring Introduction In order to pump blood and perfuse tissues, the body requires adequate volume. Pumping and Perfusion II builds on the concept of preload, or volume as it relates to cardiac output. This first unit, basic hemodynamic monitoring, will introduce hemodynamic monitoring concepts. Hemodynamic monitoring is one of the more advanced technologies for monitoring the critically ill client. Hemodynamic monitoring can be as simple as taking a blood pressure or a central venous pressure (CVP) reading or as complex as obtaining and interpreting mixed venous oxygen saturation (SvO 2 ). We will build on these concepts when advanced hemodynamic monitoring (Pulmonary artery (PA) catheters) is introduced in your inflammation course. This unit will discuss the principles, interpretation and complications of hemodynamic monitoring. Learning Outcomes In this unit the learner will be able to: 1. Describe the components and functions of hemodynamic monitoring systems used for arterial and central lines. 2. Describe various insertion sites for arterial lines and central venous catheters in relation to the advantages, disadvantages, and complications. 3. Analyze the normal waveforms and numerical values associated with arterial lines and central venous pressures. 4. Identify appropriate nursing interventions to correct abnormal hemodynamic monitoring parameters. Resources Urden, L. D., Stacy, K. M., & Lough, M. E. (2014). Critical care nursing: diagnosis and management (7th ed.). St. Louis: Mosby, Elsevier, pp. 237-252. August 2015 RN Professional Development Centre Page 2
Common Principles for Hemodynamic Monitoring 1. Single readings are not as significant as the trend of the pressure (e.g., is it increasing, decreasing, or staying stable). 2. Values must be interpreted in relation to the client s history, clinical course, interventions, physical assessment and other parameters (e.g., mean arterial pressure). 3. To obtain accurate values, the transducer or water manometer must be levelled to the phlebostatic axis. Arterial Line Monitoring Intra-arterial blood pressure monitoring is a frequently used intervention for the critically ill patient. The benefits of this type of monitoring system include the ability to visually assess the arterial waveform and increased accuracy of blood pressure measurement. This section will discuss (a) the etiologies which result in the need for an arterial line, (b) the monitoring system used, and (c) arterial waveform analysis. It will conclude with the identification of potential problems arising from the use of arterial lines and the related nursing care. To review the etiologies for an arterial line, the equipment needed to set up a monitoring system and insertion techniques, please read: Please read the following: Urden et al., p. 237-242 (Stop reading at Arterial Pressure Waveform Interpretation ) August 2015 RN Professional Development Centre Page 3
Arterial Line Insertion Site Advantages/Disadvantages INSERTION ADVANTAGE DISADVANTAGE Radial artery Very accessible. Highly visible. Collateral circulation present. Requires immobilization of wrist. Brachial artery Very accessible. Highly visible. Larger artery. No collateral circulation. Requires immobilization of elbow. Close proximity to brachial nerve. Axillary artery Femoral artery Dorsalis pedis artery Larger artery. Allows free movement of hand. Larger artery. Very accessibleparticularly during emergency situations. Very accessible. Highly visible. Collateral circulation present. Poor visibility of site. No collateral circulation. Hematoma development can cause brachial plexus compression. Poor visibility of site. No collateral circulation. High risk of infection related to close proximity to perineum. Difficult to control bleeding. Small size artery. Avoid using in patients with peripheral vascular diseases or diabetes. Higher systolic pressures and lower diastolic pressures than radial artery. Nursing Management of Arterial Lines Please read the following: Urden et al., p. 242-247 (Stop at Central Venous Pressure Monitoring ) The following information is provided in order to facilitate your understanding of the concepts discussed in the previous reading. Arterial Pressure (produced by the ejection of blood from the left ventricle into the arterial system) = Cardiac Output (the volume of blood ejected by the left ventricle) x Systemic Vascular Resistance (the resistance to the flow of that volume through the systemic vasculature). August 2015 RN Professional Development Centre Page 4
Arterial systolic pressure represents the maximal pressure generated by the left ventricle to expel the volume of blood. Arterial diastolic pressure reflects the velocity of the flow of the ejected blood, as well as the elasticity of the arterial system, particularly the arterioles. Pulse pressure, the difference between systolic and diastolic pressures, is primarily determined by the volume of blood ejected from the heart with each beat (stroke volume) and the elasticity of the arterial system. Mean arterial pressure (MAP) represents the average pressure in the arterial system throughout systole and diastole. It can be mathematically calculated. MAP = (diastole x 2) + (systole x 1) 3 Slight differences exist between arterial line pressure readings and cuff pressures. Arterial systems measure pressure (the magnitude of force exerted by circulating blood over a specific area) whereas cuff pressures measure flow (the amount of circulating blood over a specific time). Some clinicians suggest that cuff pressures be taken once per shift to correlate with arterial pressure readings, while others propose that this practice is unnecessary since the two methods are measuring different phenomenon. For example, in a shock state the blood vessels vasoconstrict, and, as a compensatory response, tachycardia and increased cardiac output occur. In this instance, the cuff pressure may be higher than the arterial pressure because of the increased blood flow resulting from the compensatory mechanisms. The arterial pressure would more accurately reflect the physiological changes in the patient s blood vessels during the shock state. The most valuable point to remember is that any type of monitoring system, whether simple or complex is prone to mechanical failure. Therefore, any time blood pressures are suspicious (i.e., too high, too low, no correlation between methods or inappropriate to the patient s condition) evaluate the patient. If the patient is stable, check your equipment. As well, it is important to note that trends of blood pressure readings are most valuable compared to isolated readings. Blood pressure readings differ depending on the measurement site used (e.g., arms versus legs). As blood travels away from the heart, diastolic and mean arterial pressures decrease slightly, while systolic pressure increases. For example, systolic pressure in the legs can be 20-30 mmhg higher than in the forearms. August 2015 RN Professional Development Centre Page 5
The arterial waveform (Refer to Figure 14-2 in Urden et al., p. 243) is a graphic representation of the ejection of blood from the left ventricle. This waveform is divided into the two components of arterial blood pressure: systole and diastole. The normal arterial waveform is characterized by: (a) an initial sharp rise (anacrotic limb), (b) a rounded top (systole), (c) a dicrotic notch on the downstroke (dicrotic limb) of the arterial waveform, and (d) a tapering off of the downstroke after the dicrotic notch (diastole). The highest point recorded corresponds to the systolic reading and the lowest point corresponds to the diastolic reading. Your reading describes waveform interpretation including normal, decreased arterial perfusion, pulse deficit, pulsus paradoxus, pulsus alterans, dampened and underdampened waveforms. The square wave snap test (Refer to Urden et al. Fig 14-10, p. 248) is performed by: (a) pulling the fast flush valve fully open; (b) holding it for one second; (c) quickly releasing the valve, allowing it to snap shut and (d) observing the change in waveform on the monitor. Note: To prevent vasospasm and/or embolus, forceful or prolonged flushing should be avoided. In an over damped system systolic pressure may be falsely decreased, while diastolic pressure is falsely increased. The nurse should check tubing for presence of blood clots, air bubbles, kinks and loose connections. In an under damped system systolic pressures are falsely high and diastolic pressures may be falsely low. Removing any air bubbles in the tubing, using large bore, shorter tubing or using a damping device (an accudynamic) may correct this problem. In addition to patient safety measures described by Urden et al. in Table 14-2 (p. 245-246), also remember to: Check your patient's coagulation status (INR, PTT and platelet levels) before removal of any patients line. Apply firm pressure to the insertion site for five to ten minutes, when removing the arterial catheter. Inspect the site for bleeding or hematoma formation which can lead to compromised perfusion to the extremity. Change the arterial catheter flush solutions and tubing every 96 hours (or according to hospital policy) to prevent infection. Heparin is generally not used with arterial lines in NS due to the risks of developing heparin induced thrombocytopenia (HIT). August 2015 RN Professional Development Centre Page 6
Check the patient status when a problem is suspected before proceeding to examine the equipment or troubleshooting. This ensures that patient safety is always the priority. Use the minimal amount of blood discard prior to taking samples to avoid anemia. Blood conservation systems are used to minimize blood loss and may be cost effective in patients requiring multiple specimens. LEARNING ACTIVITY 1 1. Match the following problems with their cause. Problem Cause A. Thrombus formation Transducer below the phlebostatic axis. B. Air emboli Prolonged catheter use. C. Haemorrhage Less than 300 mmhg pressure on the IV flush solution. D. Infection Drip chamber not filled when new IV bag applied. E. Abnormally low readings F. Abnormally high readings Stopcock turned off to the patient. Loose connection. G. No waveform Transducer above the phlebostatic axis. 2. Match the following preventive measures with the problem. Problem Measure A. Thrombus formation Raise the transducer to the level of the phlebostatic axis. B. Air emboli Close and cap stopcocks when not in use. C. Haemorrhage Infuse heparin solution through the in-line flush device. D. Infection Ensure that all stopcocks are in correct position and tubing is not kinked. E. Abnormally low readings F. Abnormally high readings Purge all air bubbles from the set up before using. Change IV solution q24h. G. No waveform Ensure that the transducer is level with the phlebostatic axis. August 2015 RN Professional Development Centre Page 7
Central Venous Pressure (CVP) To gain an understanding of advanced hemodynamic monitoring and the interpretation of related parameters, it is beneficial to start with a less complex parameter such as measurement and interpretation of the central venous pressure (CVP), before moving on to advanced hemodynamic monitoring using Pulmonary Artery (PA) catheters or other non-invasive methods of measuring cardiac output. Since CVP and right atrial pressure (RAP) are synonymous in that they both indicate the pressure in the right atrium, the term RAP will be used throughout this unit. Pressure in the right atrium can indicate an alteration in preload (fluid or volume status). As discussed in pumping and perfusion I, preload or volume of blood in the heart is a determinant of cardiac output. It is affected by venous return, changes in blood volume and atrial kick. Please read the following and review indications, insertion sites, complications, and nursing management of central venous pressure monitoring: Please read the following: Urden et al., p. 247-252 (Stop at Pulmonary Artery Pressure Monitoring) Normal Right Arterial Pressure (RAP) Value Normal RAP values vary from text to text. For instance, Urden et al. presents the normal RAP value as 2-5 mmhg. Other texts that you may have read indicate the RAP value as 0-8 mmhg. For purposes of this program, the normal right atrial pressure range used will be 2-6 mmhg. It is important to note this is an appropriate RAP in a normal healthy person NOT a sick patient. When patients experience various diseases, they may require a RAP outside of this range. Please refer to your laminated Critical Care Nursing Program Guide it provides you with a list of normal hemodynamic parameters. Patient Safety/Evidence Informed Practice Central Line-Associated Bloodstream Infections (CLABSIs) are a serious complication related to central venous catheters and a have a safety intervention bundle of evidencebased practice guidelines promoted by Safer Healthcare Now! Please refer to the following: http://www.saferhealthcarenow.ca/en/interventions/cli/pages/default.aspx These safety initiatives outlined by Safer Healthcare allow for standardization of care and reduce patient risk of line infections and include the following interventions: August 2015 RN Professional Development Centre Page 8
On insertion: Hand hygiene Maximum barrier precautions Chlorhexidine skin antisepsis Optimal catheter type and site selection Daily: Review of central and arterial lines for necessity to promote prompt removal of unnecessary lines Aseptic lumen access Optimal catheter site and tubing care A great deal of information has been presented thus far. At this point, an instructional activity is provided to help you assess your understanding of the content presented. LEARNING ACTIVITY 2 Please answer the following questions: 1. Hypovolemia and loss of atrial kick would be two examples of preload and therefore, CVP. 2. Renal disease and vasoconstriction would be two examples of preload and therefore, CVP. 3. A realistic treatment for someone with a CVP of 15 would be. 4. Mr. Jones returns from surgery with a central venous catheter in place. His blood pressure is 75/30 and the surgeons tell you that he has lost 5 litres of blood. List priority interventions and why. Perfusion Parameter Measured with Central Venous Catheters A venous blood gas can be drawn from a central venous catheter. A mixed venous saturation obtained from the central line is called a S c VO 2. A true SVO 2, or saturation of venous oxygen, is drawn from the pulmonary artery (PA) when the PA catheter is used. We will discuss these concepts more with advanced hemodynamic monitoring in the inflammation lesson. The S c VO 2, drawn from the central line, can be utilized to interpret the balance between oxygen supply and demand. Recall from ventilation and oxygenation that oxygen supply or delivery of oxygen (DO 2 ) can be expressed by the formula =(Hg, SaO 2 and PaO 2 ) x (CO). S c VO 2, perfusion parameter, when interpreted with arterial supply and patient condition, assists clinicians to determine treatment to optimize oxygenation status. August 2015 RN Professional Development Centre Page 9
Normal SVO 2 = 60%-80%. 1. High SVO 2 (greater than 80%) possible indications are Anaesthesia Receiving more oxygen than necessary Hypothermia Sepsis (decreased utilization by the tissues) 2. Low SVO 2 (less than 60%) possible indications are Bleeding (anemia, hemorrhage) Conclusion Shock state Hypoxemia from decreased supply Increased metabolic demand The knowledge and skills presented in this unit have prepared you to care for a patient who needs hemodynamic monitoring. This content will be reinforced during your lab and clinical experiences. August 2015 RN Professional Development Centre Page 10
Learning Activity Answer Key Arterial Lines 1. F D A B G C E 2. F C A G B D E Learning Activity 2 1. Decreased, Decreased 2. Increased, Increased 3. Diuresis 4. Fluid resuscitation (blood, pentaspan, colloids, crystolloids) to maintain adequate perfusion to the vital organs. August 2015 RN Professional Development Centre Page 11
BIBLIOGRAPHY Ahrens, T. (2010). Stroke volume optimization versus central venous pressure in fluid management. Critical Care Nurse, 30(2), 71-73. Breitenbach, J.E. (2007). Putting an end to perfusion confusion. Nursing made Incrediibly Easy!, May/June 2007, p. 50-62. Scales, K., & Collie, E. (2007). A practical guide to using pulmonary artery catheters. Nursing Standard, 21(43), 42-48. Urden, L. D., Stacy, K. M., & Lough, M. E. (2014). Critical care nursing: diagnosis and management (7th ed.). St. Louis: Mosby, Elsevier. Woodrow, P (2009). Arterial catheters: promoting safe clinical practice. Nursing Standard, 24 (4), 35-40. August 2015 RN Professional Development Centre Page 12