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IntroductionHemodynamic monitoring is the active assessment of cardiopulmonary status by the use of biosensors that assess physiologic outputs.The simplest form of monitoring is the individual health care professional, inspecting the patient for consciousness, agitation or distress,breathing regular or labored, the presence or absence of central and peripheral cyanosis; touching of the skin of a patient to note if it iscool and moist, and if capillary refill is rapid or not; palpation of the central and peripheral pulses to note rate and firmness.Although well established and important as bedside diagnostic tools, these simple “human-instrument” measures can be greatly expandedby the use of pulse oximetry to estimate arterial oxygen saturation (Spo2), and the sphygmomanometer and auscultation to note systolicand diastolic blood pressure and identify pulsus paradoxus. These classic measures of hemodynamics, often referred to as routine vitalsigns, are central to the assessment of cardiorespiratory sufficiency and much of diagnostic bedside medicine is rooted in these importanttechniques.However, with some exceptions, these simple and inexpensive measures do not have the discriminatory value in identifying patients asbeing stable or unstable when compensatory processes mask instability or when changes in physiologic state occur rapidly. Furthermore,they predict poorly who are at an early stage of an instability process, such as hypovolemia or heart failure, but compensating. Within thecontext of circulatory shock, tachycardia may or may not develop early and even if it is present, it is nonspecific. However, these simplemeasures can be markedly helped in their sensitivity to detect effective hypovolemia by making these same measures before and duringan orthostatic challenge.For example, measuring blood pressure and pulse rate changes between lying supine, sitting, and standing markedly increase thediagnostic capability of the measures to identify functional hypovolemia. If heart rate increases and/or blood pressure decreases withsitting or standing, it is reasonable to presume that some degree of compatible hypovolemia exists. However, the other important conceptin making these observations is that the measures themselves do not change, but their measured values change in response to a definedphysiologic challenge: this is an example of functional hemodynamic monitoring. Functional hemodynamic monitoring is the use of adefined physiologic stressor to access the physiologic reserve of the system.Both invasive and non invasive hemodynamic monitoring is used extensively in critical care practice. Invasive monitoring is used to obtaincontinuous pressure measurements in the central and systemic circulation. These parameters are used to estimate physiological variablesuch as cardiac output and volume status.Learning outcomes for this sectionUpon successful completion of this section, you should be able to:discuss the theoretical principles of haemodynamicssafely action haemodynamic monitoring procedures and protocolsinterpret hemodynamic monitoring outputrelate hemodynamic monitoring parameters to physiology of critically ill patientsrealise the contribution hemodynamic monitoring makes as part of continuous patient assessment.14/9/2020 Study plan: Week 4 – Haemodynamic monitoringhttps://flo.flinders.edu.au/mod/book/tool/print/index.php?id=2585802 4/15ReviewThe material discussed in this section requires an appreciation of the factors which are related to cardiac output.Revise the following and list the normal values for each:cardiac outputcardiac indexstroke volumestroke volume indexpreloadafterloadsystemic vascular resistancepulmonary vascular resistancecontractility.Cardiac Cycle animationBlood Pressure Animation4/9/2020 Study plan: Week 4 – Haemodynamic monitoringhttps://flo.flinders.edu.au/mod/book/tool/print/index.php?id=2585802 5/15Suggested readingsCore text readingAitken, A, Marshall, A, & Chaboyer, W.,2015, ACCCN’s critical care nursing, 3nd edn, Elsevier, Australia, Chapter 9, pp. 248-260.Other readings are highlighted through-out this module4/9/2020 Study plan: Week 4 – Haemodynamic monitoringhttps://flo.flinders.edu.au/mod/book/tool/print/index.php?id=2585802 6/15Concepts of haemodynamicsHeart Lung.org – great resource – Click HerePressure and flowPressure is the force applied per unit area. In haemodynamics we always think of pressure in terms of a pressure difference. Thepressure difference along the axis, or pressure gradient, is the pressure that causes the flow of blood. The pressure differencebetween the inside and outside of a vessel or the heart, which is often called transmural pressure, and causes the wall distension.It is important to remember that even though pressure is measured with various endpoints that are manipulated and responded toclinically; we can lose the focus of blood flow or perfusion which is the only hemodynamic concept that is associated with improved patientsurvival.Blood flow is represented by cardiac output (Q).Cardiac Output (Q) = Stroke Volume x Heart RateThe stroke volumes for each ventricle are generally equal, both being approximately 70-85 ml. Stroke volume is the difference betweenend diastolic volume and end systolic volume.Interesting, Q has no pressure measurement in the above formula yet pressure is what we measure regularly as volume is far moredifficult to measure. However,Stroke volume = Pulse pressure x 2(Pulse pressure is the difference between systolic and diastolic pressure)Hence we have difference in pressure as explained above and it is used to calculate stroke volume which is related to flow (Q) once weadd a driving force of heart rate. Invisible to this assumption is that heart contractility and elastance determine the filling, stroke volumeand driving force contraction of the heart and must not be forgotten.The vascular beds are a dynamic and connected part of the circulatory system against which the heart must pump to transport the blood.Q is influenced by the resistance of the vascular bed against which the heart is pumping. For the right heart this is the pulmonary vascularbed, creating Pulmonary Vascular Resistance (PVR), while for the systemic circulation this is the systemic vascular bed, creating SystemicVascular Resistance in dynes-sec-cm (SVR).Put simply, increasing resistance decreases Q; conversely, decreasing resistance increases Q.By simplifying Darcy’s (and Ohm’s)Law, we get the equation thatFlow = Pressure/ResistanceWhen applied to the circulatory system, we get:Q = Mean Arterial Pressure/Systemic Vascular ResistanceMuch of the focus clinically on haemodynamics is the Mean Arterial Pressure (MAP) but as you can see it is related to Q or blood flow onlywhen Systemic Vascular Resistance (SVR) is added to the equation. Hence a patient may have MAP that is matching a prescribedendpoint of 75 mmHg, but if the SVR is high the Q will be reduced to below the cell’s metabolic need for oxygen and nutrients and thepatient will struggle to survive.So it is worthwhile to assess SVR in conjunction with MAP.SVR can be measured through various haemodynamic devices and can be assessed clinically as peripheral coolness and capillary return.However as you can see in the equation below, the SVR can be calculated with simple monitoring.Q = (HR × SV) = MAP / SVRCalculate the HR and the SV; then you can calculate the Q or cardiac output. As you are measuring the MAP with monitoring and it iseasily accessed, you can divide the MAP by Q to get an approximation of the SVR in dynes-sec-cm by multiplying MAP in mmHg by 80.SVR = 80 x MAP/QOhm’s Law and Hemodynamics (Fluid …554/9/2020 Study plan: Week 4 – Haemodynamic monitoringhttps://flo.flinders.edu.au/mod/book/tool/print/index.php?id=2585802 7/15Cardiac Output and RespirationQ is affected by the phase of respiration with intra-thoracic pressure changes influencing diastolic heart filling and therefore Q. Breathing inreduces intra-thoracic pressure, filling the heart and increasing Q, while breathing out increases intra-thoracic pressure, reduces heartfiling and Q. This respiratory response is called stroke volume variation and can be used as an indicator of cardiovascular status and fluidneeds.These respiratory changes are important, particularly during mechanical ventilation, and Q (as well as arterial and central venouspressure) should therefore be measured at a defined phase of the respiratory cycle, usually end-expiration.ActivityCalculate the Cardiac output (HR & SV), SVR and MAP for your allocated patients this week. Consider:
The clinical assessment of the patient compared with their haemodynamic values.
Medications that the patient is receiving that modulate SVR, HR, or cardiac output (contractility and/or strokevolume).
The relationship between the MAP and the SVR and how cardiac output is affected.Viscosity and Poiseuille’s Law (Fluid M…How Does Respiratory Pump Affect Ve…Hemodynamic Principles4/9/2020 Study plan: Week 4 – Haemodynamic monitoringhttps://flo.flinders.edu.au/mod/book/tool/print/index.php?id=2585802 8/15Arterial Pressure MonitoringFluid filled monitoring devices are used extensively to evaluate pressures in various cardiovascular compartments. These work on theassumption that any change in pressure at any point in an unobstructed fluid filled system results in a similar change in pressure at allother points in the system. In most invasive monitoring systems this involves a fluid filled intravascular catheter attached to a pressuretransducer which converts the pressure of the fluid into an electrical signal. This depends upon the fluid filled system to be unobstructedby air bubbles or kinks and low compliance semi rigid tubing used.A flush system consisting of a bag of normal saline to which heparin may or may not be added is used to maintain patency of the fluidfilled monitoring device.eReadingRead the relevant section in your text book and answer the following questions.Activity
Describe briefly how a waveform is displayed on the monitor. [You will need to understand the relationshipbetween monitor, transducer and patient parameters to answer this question correctly.]
Describe the square wave form test and the effect of dampening on the pressure measurement system.What can cause a dampened response?
Why is it important that non-distensible tubing be used on pressure monitoring lines?
Describe the meaning of the systolic, diastolic and mean arterial pressures? If these are abnormal, (high orlow) what does it mean for the patient? How is the mean calculated?
Draw an intra-arterial waveform. What does the dicrotic notch signify?
Where and how are arterial catheters inserted?
What is the Allen test and when is this performed?
What are the complications of intra-arterial catheter monitoring? What nursing observations are necessary todetect these?
Why are transducers calibrated and zeroed?
What is the purpose of levelling the transducer? Locate the phlebostatic axis.
Discuss the infection control risk with venous access devices. Research the protocols in place in yourdepartment to minimise the risk of infection.CVP and Arterial Line Waveform Interp…
Arterial Pressure Monitoring, Chapter 4 in Hemodynamic Monitoring Made Incredibly Visual! 2nd Edition. Lippincott Williams & Wilkins. Web. – Click Here
1. Quick guide to cardipulmonary care booklet – Click Here4/9/2020 Study plan: Week 4 – Haemodynamic monitoringhttps://flo.flinders.edu.au/mod/book/tool/print/index.php?id=2585802 9/15Central venous pressure monitoringThe central venous pressure gives a direct measurement of right atrial pressure and indirectly reflects the preload of the right ventricle orright ventricular end diastolic pressure. The measurement of end diastolic pressure gives an estimation of end diastolic volume. Volumeestimations are used to titrate fluid therapy and increase cardiac output by optimising preload. This is based on the Frank Starling Law ofthe heart which states that the greater the end diastolic fiber stretch the greater the force of contraction. Overfilling can result in adecrease in stroke volume and cardiac output.Central venous access is frequently necessary for both measurement of central venous pressure and access for fluids and infusions.eReadings
Magder, S 2015, ‘Understanding central venous pressure: not a preload index?’, Current Opinion in Critical Care, vol. 21, no.5 pp 369-375. Click Here2 De Backer, D. & Vincent, J.-L. 2018. Should we measure the central venous pressure to guide fluid management? Tenanswers to 10 questions. Critical Care, 22, 43. Click HereVideosActivity
Explain how central venous pressure can represent blood flow?
What are the possible sites of insertion of a central venous catheter?
What factors may influence the decision of insertion site?
Familiarise yourself with the markings on the catheter which indicate insertion length. What is the usualinsertion length for in each site of insertion?
Describe the seldinger technique of insertion of central venous catheters.
Why is it important to place the patient in a slightly head down position during insertion or disconnection of acentral venous line?
What is the normal CVP and what factors may affect it?
Describe the effect of the respiratory cycle on the central venous pressure and how this affects themeasurement which is recorded. How does this differ if the patient is mechanically ventilated?
Source the procedure in your unit for extraction of a CV blood sample for a Central Venous OxygenSaturation (ScvO2) measurement.
List five possible complications when using a central venous catheter?
Central venous catheters are available in different brands, with different numbers of access ports, designedfor different sites and different length of insertion times. They also have different coatings for infection controlreasons. Make a list of the various central venous catheters available in your unit and their particularcharacteristics. Explain in what situation their use would be applicable and why?Central Line Procedure4/9/2020 Study plan: Week 4 – Haemodynamic monitoringhttps://flo.flinders.edu.au/mod/book/tool/print/index.php?id=2585802 10/15Pulmonary artery pressure monitoringThis section is for critical care specialistsThe pulmonary artery catheter has been used extensively since the 1970s to evaluate filling pressures of the left ventricle by way ofmeasuring the pulmonary artery occlusion pressure. This gives an estimation of the left ventricular preload. The pulmonary artery catheteris also used to calculate cardiac output by way of thermodilution, and blood gas analysis of samples taken from the catheter tip give anaccurate measurement of mixed venous oxygenation. It’s popularity has reduced in the last few years with other less invasive technologiesbeing used.eReadingVideoActivity
List the ports and the function of each commonly found on a pulmonary artery catheter.
Familiarise yourself with the insertion measurements on the pulmonary artery catheter. What is the likelyinsertion length of pulmonary artery in the most common insertion sites?
Describe the insertion technique for the pulmonary artery catheter. Familiarise yourself with the waveformcharacteristics at each stage of the insertion process.
Make a list of the possible complications of pulmonary artery catheter both during the insertion process andwhile insitu. Include the routine assessments performed to detect these and the precautions which are takento prevent these occurring.
How is a pulmonary capillary occlusion pressure (PCOP) or ‘wedge’ pressure obtained?
What does the PCWP (PCOP) indicate and what could be considered normal, optimal and fluid overloadedvalues? Explain why you see these as such and in what clinical circumstances.
How can you tell if the PCWP value is accurate?
Why is the mixed venous sample taken from the PA port?
How should pulmonary catheter balloon rupture be prevented and treated? Describe your nursing actions oftreatment using an ABC process
What is microshock and how do we prevent it?Pulmonary Arterial Catheterization12 Measuring Wedge Pressure
Pulmonary Artery Pressure Monitoring, Chapter 6 in Hemodynamic Monitoring Made Incredibly Visual! 2nd Edition. Lippincott Williams & Wilkins. Web. – Click Her4/9/2020 Study plan: Week 4 – Haemodynamic monitoringhttps://flo.flinders.edu.au/mod/book/tool/print/index.php?id=2585802 11/15Cardiac output measurementInvasive hemodynamic monitoring is used to monitor cardiac output in critically ill patients. This parameter allows the practitioner tocalculate other derived indices of cardiovascular function. The pulmonary artery catheter has long been considered the gold standardmethod of measuring cardiac output in critically ill patients. More recently other techniques have been employed for cardiac outputestimation. The pulmonary artery catheter provides a measurement of cardiac output by means of thermodilution. Here a bolus of a knownvolume of crystalloid solution into the right atrial or CVP port. A calculation of stroke volume is made based on the resulting temperaturechanges at the tip of the pulmonary artery catheter. Like measurements of PCWP and CVP the measurement of cardiac output is affectedby breathing and must be taken at the same part of the respiratory cycle, normally at end expiration.Calculations of other indices of cardiovascular function are made using these values along with the PCWP and CVP measurement. Thesevalues are converted to indices by the hemodynamic calculator available on most modern monitors. Here, the height and weight of thepatient are used to index the value to body surface area. These include systemic vascular resistance index which gives an estimation ofleft ventricular afterload, and pulmonary vascular resistance which gives an estimation of right ventricular afterload. Contractility ismeasured by calculation of the stroke work indices of the right and left ventricle.In recent years the use of the pulmonary artery catheter has decreased in some critical care units in favour of less invasive methods ofmonitoring cardiac output. These include the techniques of transpulmonary thermodilution and pulse contour analysis as used by PiCCOtechnology and trans-oesophageal Doppler measurement. A recent systematic review by the Cochrane Collaboration (Harvey et al 2006)concluded that the use of pulmonary artery catheters do not improve survival or hospital length of stay, but do contribute to the cost oftreatment. The study did also comment that the use of alternative methods of cardiac output analysis requires careful scrutiny before theyare widely adopted into general practice.eReadingActivityRead the relevant section in your text book and answer the following questions.
Why do we need to perform at least three measurements before calculating our results and what are youobserving about them?
Define cardiac index.
Why is 5% dextrose the fluid of choice in cardiac output measurement?
Cardiac output can be measured in many different ways: the most commonly used method is bythermodilution. Describe other ways of obtaining cardiac output measurement (describe three, one mustinclude PICCO or NICCO).Swan-Ganz Thermodilution Pulmonary …
Cardiac Output Monitoring, Chapter 7 in Hemodynamic Monitoring Made Incredibly Visual! 2nd Edition. Lippincott Williams & Wilkins. Web. – Click Here4/9/2020 Study plan: Week 4 – Haemodynamic monitoringhttps://flo.flinders.edu.au/mod/book/tool/print/index.php?id=2585802 12/15Pulse contour analysis—continuous cardiac outputPulse Contour Analysis uses the concept of Frank Starling to calculate stroke volume and cardiac output of the left heart by analysing theaortic pulse contour. This method involves the calculation of the area under the systolic portion of the arterial pressure waveform, which,divided by aortic impedance, allows the estimation of the left ventricular stroke volume. Various different monitoring devices use arterialpulse contour analysis for continuous cardiac output monitoring, for example, the PiCCO© or the PulseCO©. So called dynamicparameters, such as the systolic pressure variation (SPV), the pulse pressure variation (PPV), and the stroke volume variation (SVV), allbased on respiratory—induced changes in the interactions of heart and lungs have been evaluated by different groups to improve theassessment of fluid responsiveness, and by that to optimise fluid therapy in mechanically ventilated patients the method of arterial pulsecontour analysis seems to be indeed a useful carrier to transfer clinically relevant, direct information on systemic blood flow in anautomated and continuous mode, and most importantly without any time delay at the patient’s bed side.Activity
How can haemodynamic monitoring be used to predict the response of a patient to intravenous fluid?
What other clinical indicators can you use in your assessment of patient fluid volume status?13 Measuring Cardiac OutputFluid Responsiveness4/9/2020 Study plan: Week 4 – Haemodynamic monitoringhttps://flo.flinders.edu.au/mod/book/tool/print/index.php?id=2585802 13/15Recognising deterioration with haemodynamic monitoringWhen a patient is admitted to hospital with an acute medical illness, their safety is a prime concern for healthcare professionals. However,a number of studies published over the last two decades have demonstrated that significant unintentional harm is caused to patientsthrough nurses’ failure to recognise the signs of clinical deterioration. Changes in the patient’s physical condition result in haemodynamicinstability as the critical bodily functions start to fail and may be detected through observation and recording of the patient’s physiologicalvital signs of respiratory rate, heart rate, blood pressure and temperature, and other haemodynamic parameters which gradually becomemore abnormal with the progression of deterioration. The effective nursing observation of patients is therefore crucial to patient safety andoutcome since this is the first step in identifying signs of clinical concern. Despite significant attention given to the observation of patientsand the publication of national guidance to clinical staff, the issue of unrecognised clinical deterioration of patients continues to be asignificant problem.Early recognition of deteriorationIt is difficult to identify patients early on in the course of circulatory shock because normal sympathetically medicated compensatory reflexmechanisms express themselves so as to sustain a relatively normal organ perfusion pressure and blood flow. For example, the normalresponse of the body to hypovolemia or impaired ventricular pump function is to attempt to maintain an adequate mean arterial pressure(MAP) by increasing sympathetic tone causing vasoconstriction, decreasing unstressed vascular volume, increased contractility, andtachycardia. In a healthy athlete early on in hypovolemic shock, tachycardia may not present, and in the elderly and those withdysautonomia tachycardia may not develop at all. Because these reflex sympathetic feedback mechanisms aim to sustain MAP above aminimal value to maintain cerebral and coronary blood flow, and because vascular capacitance is reduced to sustain cardiac output,hypotension not only occurs late but must be associated with tissue hypoperfusion. Hypotension in the setting of circulatory shock mustalso reflect failure of compensatory mechanisms to sustain normal homeostasis.Thus, hypotension is a medical emergency not only because it must be associated with tissue hypoperfusion but also because itsignals loss of intrinsic mechanisms to sustain effective blood flow.Furthermore, restoring MAP by the use of vasopressors improves tissue oxygenation in septic patients. Thus, the immediate restoration ofMAP while other flow-directed resuscitation efforts are under way is essential in minimizing ongoing tissue hypoperfusion.Using the principles described herein, it is possible for the bedside clinician to answer four interrelated important questions of theirpatients.Are they compensating?Are they volume responsive?Is arterial tone increased, normal or decreased?Is their heart able to sustain flow without high filling pressures (ie high CVP)?Haemodynamic protocol4/9/2020 Study plan: Week 4 – Haemodynamic monitoringhttps://flo.flinders.edu.au/mod/book/tool/print/index.php?id=2585802 14/15Haemodynamic Simulation-H.264 for V…4/9/2020 Study plan: Week 4 – Haemodynamic monitoringhttps://flo.flinders.edu.au/mod/book/tool/print/index.php?id=2585802 15/15Lifespan considerationsLifespan considerationsPaediatric FocusThe key principles of haemodynamic monitoring are similar to that of adults. It is however beneficial to be aware of some major differeThe major key point is that placement of invasive lines is technically more difficult and time consuming than placing them in adults.This will alter the risk:benefit ratio and there may often be a higher threshold for the insertion of invasive lines in paediatric patients comIn paediatrics, the best method of monitoring is frequent observation and clinical assessment.Like adults, end organ perfusion can be assessed by monitoring level of consciousness, capillary refill time, urine output, and lactaInsertion of invasive lines will almost always necessitate a degree of sedation, especially the insertion of central lines as children mSedation must always be administered with caution in children as it may cause them to lose their sympathetic drive which may resuSampling anaemia can be a significant problem due to the low total blood volume of paediatric patients compared with adults.Fluid infusions to maintain line patency are a significant contributor to total fluid intake, necessitating absolute diligence when moniPaediatric BASIC (2014). Basic assessment and Support in Paediatric Intensive Care.Figure: Paediatric arterial line insertion and dressing in an infantOlder Adult FocusThe older adult has more subtle compensatory responses and the signs and symptoms may be easily missed. This is the result of aginIncreased dysrhythmiasincreased atrial size and irritabilityleft ventricular myocardial thickening leading to decreased compliancelower ejection fraction,thickened heart valves that interfere with forward flowdecreased response to sympathetic nervous systemdecreased sensitivity of baroreceptors;generalised stiffening of arterial vessels, including aorta.
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