What is the role of invasive hemodynamic monitoring in critical care?

SECTION 9  Hemodynamic Management

48 What Is the Role of Invasive Hemodynamic Monitoring in Critical Care? Daniel De Backer

INTRODUCTION Hemodynamic monitoring provides important information about the approach to the patient in acute circulatory failure. The strength of monitoring lies not in the direct impact on outcome,1 but rather in directing clinical management. Indeed, accurate hemodynamic data provide important information on (1) the patient’s condition, (2) therapeutic choices, and (3) the effects of these choices. Current trends favor the use of minimally invasive2 (e.g., calibrated pulse wave analysis and esophageal Doppler) or noninvasive approaches (e.g., bioreactance and bioimpedance techniques, noninvasive pulse contour methods, echocardiography) but invasive hemodynamic monitoring techniques (e.g., pulmonary artery catheter and transpulmonary thermodilution) are still widely used.3 The information provided by noninvasive techniques is often limited to cardiac output and stroke volume variations, while more invasive techniques provide more information, such as intravascular pressures and cardiac volumes. The reliability of the various techniques in severely ill patients is variable and often inversely proportional to invasiveness. Accordingly, the choice of the hemodynamic technique should not be guided solely on the basis of its invasiveness, but should also take into account accuracy of the approach and, most importantly, the potential value of the added information. The choice of the hemodynamic monitoring device should thus be individualized. Perhaps the most important change in the hemodynamic evaluation of the critically ill patients is the ever-increasing reliance on echocardiography.4 Echocardiography is now recommended in the initial hours for the classification of shock5,6 and observational studies suggest that its use, alone or in combination with other tools, is associated with a better outcome.7 However, echocardiography is discontinuous, even if it can be easily repeated. In addition, hemodynamic evaluation using echocardiography requires skills that go well beyond the basic level.8 Accordingly, echocardiography is often used in combination with other tools providing online, hemodynamic measurements. 332

The main indications for hemodynamic monitoring are the identification of the type of shock6 and therapeutic guidance. Another important indication is cardiopulmonary evaluation of the patient with respiratory failure. In this chapter, we discuss the use of invasive techniques for hemodynamic monitoring.

INVASIVE OR NONINVASIVE ARTERIAL PRESSURE MONITORING? Arterial pressure is a key determinant of organ perfusion and is routinely measured in critically ill patients, either noninvasively or invasively. Noninvasive measurements can reliably be used in less severely ill patients but are unfortunately less reliable in patients with shock, when accuracy of measurements is most important.9 For example, an overestimate of 5–10 mm Hg will have minimal impact on patient management if real mean arterial pressure (MAP) is 80 mm Hg, but could have important consequences if MAP is 55 mm Hg. Hence invasive arterial pressure monitoring is recommended in patients with circulatory failure.5

CENTRAL VENOUS PRESSURE AND CENTRAL VENOUS OXYGEN SATURATION Central venous access is often used in the care of critically ill patients, especially when in shock, and the measurements of central venous pressure (CVP) and oxygen saturation can provide important information on the hemodynamic state. Although CVP measurements reflect cardiac function and volume status, they are also influenced by intrathoracic pressure. A high CVP may reflect impaired cardiac function (biventricular or right heart), hypervolemia, or tamponade. A low CVP usually suggests hypovolemia but can be misleading in patients with isolated left heart dysfunction. Importantly, the measured CVP is also affected by intrathoracic pressures and may overestimate the true CVP (transmural CVP) in patients being mechanically ventilated. This interaction may

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limit the ability of CVP to evaluate preload responsiveness and even cardiac function. Nevertheless, CVP reflects the backpressure of the venous system and hence the driving force for tissue edema. CVP provides important information on the hemodynamic state of the patient: even though its interpretation is not always easy, it remains an important variable to measure.10 Measurement of central venous oxygen saturation (ScvO2) provides information on the adequacy of oxygen transport, and hence cardiac output. A low ScvO2 suggests a low or inadequate cardiac output, anemia, hypoxemia, agitation, or a combination of all factors. In patients with septic shock, hemodynamic optimization, based on these variables, has been suggested. While an initial trial of early goal directed therapy (EGDT), based on CVP and ScvO2, was associated with a marked reduction in mortality,11 these findings were not confirmed in three largescale international trials.12–14 Several factors may explain these conflicting results.15 At study entry, ScvO2 was close to 50% in both groups in the original EGDT trial, while the value was approaching goal (70%) on randomization into the three recent trials. If the main variable being corrected is already within target values, one would expect the intervention to have minimal impact. In the ARISE (Australasian Resuscitation in Sepsis Evaluation) trial, 78% of the patients had reached the ScvO2 goal at randomization; additional interventions only increased ScvO2 to 82%.13 Furthermore, the inclusion rate was much lower in the three recent trials (1 and 0.5 patients per center per month vs. 8 patients per center per month in the original single-center EGDT trial). Thus, there may have been some selection bias toward less severely ill patients in the more recent studies; indeed, this finding might explain the low mortality observed in the recent trials. Indeed, 50% of the included patients did not require administration of vasopressors during their entire stay12 and 18% were even not admitted to the intensive care unit (ICU).16 Finally, the “standard of care” has evolved dramatically since the original EGDT study; thus, use of the most impactful interventions were probably not restricted to the intervention groups. In aggregate, the conclusions from these trials are that protocolized EGDT does not offer survival benefit in all patients with septic shock, but that hemodynamic optimization based on ScvO2 may still be justified in the most severe patients presenting with an altered ScvO2.15

THE PULMONARY ARTERY CATHETER The invasive pulmonary artery (PA) catheter has the advantage of providing quasi-continuous information on cardiovascular status. The PA catheter measures three types of variables: intravascular pressures, cardiac output, and mixedvenous blood gases. Measurements of PA pressure are particularly indicated in cases of right ventricular (RV) dysfunction, where evaluation of RV afterload is crucial for diagnosis and for therapy.17

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Echocardiography can also provide an estimate of PA pressure. None of the noninvasive techniques can determine PA pressure at bedside. The measurement of PA pressure is less important in disorders that have minimal impact on RV function. The PA occlusion pressure is useful in the identification of left ventricular (LV) dysfunction and can aid in fluid management. It provides information on lung hydrostatic pressure, and thus on the risk of developing pulmonary edema. PA occlusion pressure is not a measurement of true capillary pressure, which is always higher; thus, an elevated PA occlusion pressure is always informative. Measurement of cardiac output is important for diagnosing the type of shock and evaluating the effect of therapies.5 Thermodilution cardiac output is measured intermittently by injection of cold bolus or automatically in a semicontinuous fashion. Importantly, most monitors average several sequential cardiac output measurements; rapid changes may be difficult to detect. Thermodilution cardiac output may be unreliable in the presence of severe tricuspid regurgitation or intracardiac shunt. At high cardiac output values, the precision of semicontinuous cardiac output measurements is lower than that of classical thermodilution,18 Finally, each hemodynamic evaluation should be accompanied by measurement of mixed venous oxygen saturation (SvO2), which enables the interpretation of the cardiac output by considering oxygen transport in relation to oxygen consumption. Although related, SvO2 may differ from ScvO2; whereas SvO2 represents the venous blood collected from all parts of the body, ScvO2 represents only the blood drained from the upper part of the body. Observational trials have demonstrated that use of a PA catheter allows for more accurate determination of the hemodynamic state than clinical evaluation and is associated with significant changes in therapy that may improve outcome.19 A series of randomized studies, however, failed to demonstrate outcome benefit from the use of PA catheters in ICU patients. Perioperative hemodynamic optimization using the PA catheter was associated with decreased complication rates25 and improved survival.26 The full value of a PA catheter may only be realized if the data are obtained and interpreted properly.27,28 The importance of these concerns is highlighted by the lack of decision algorithm use in most trials involving a PA catheter in critically ill patients. Similarly, the addition of echocardiographic data does not necessarily improve data interpretation by practitioners,29 suggesting that the fault lies with data evaluation and not with technique.30 Furthermore, the patients included in trials evaluating PA catheters were highly selected. In the Fluids and Catheters Treatment Trial (FACTT), a large number of patients were disqualified from participation because they had a PA catheter at the time of randomization, suggesting that the sickest patients were not included.31 A report on excluded patients with cardiogenic shock found that those with a PA catheter prior to randomization had significantly higher mortality rates than patients included in the trial.32 Thus, the results of the study may be biased.33 Nonetheless, publication of negative trials (and the wide

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Hemodynamic Management

availability of alternatives) was followed by a decrease in the use of PA catheters.34 Recent data appear to suggest that PA catheter use is increasing again,35,36 particularly in patients with cardiogenic shock and RV dysfunction. In summary, use of PA catheters is indicated in some situations, in particular in patients with RV dysfunction.37 Unfortunately, the decline in PA catheter use presents an educational challenge as fewer intensivists are learing how to place , manipulate and interpret the data from a PA catheter.

TRANSPULMONARY THERMODILUTION AND PULSE WAVE ANALYSIS A commonly used alternative to the PA catheter is transpulmonary thermodilution (TPTD) coupled with pulse wave analysis. These minimally invasive techniques still require placement of arterial and central venous lines. TPTD is used not only for the calibration of pulse-wave-derived continuous cardiac output measurement but also for volumetric measurements. Stroke volume can be estimated from an arterial pressure waveform. Calibration with TPTD is used to capture differences in arterial compliance and vascular tone from one patient to another, and from one time to another in a given patient.38,39 The accuracy of pulse wave analysis is highly dependent on the delay between the two calibrations. Any change in vascular tone can significantly alter the precision of these devices40 and should prompt recalibration. Newer devices that use autocalibration permit reliable measurements to be made even in patients with septic shock18 but lack the additional cardiac function and volumetric measurements. TPTD requires the use of a modified arterial catheter equipped with a thermistor. This catheter is inserted in the femoral artery. The thermodilution curve is determined using a proprietary algorithm. Cardiac output is derived from the area under the curve. TPTD is slightly less sensitive to valvular regurgitation than right-sided thermodilution. The main advantage of TPTD is that it also allows the measurement of extravascular lung water (EVLW) and of cardiac chamber volume (global end-diastolic volume index [GEDVI]), an index of preload. Volumetric indices perform better than pressures in patients with raised intrathoracic or intra-abdominal pressures or with decreased LV compliance. EVLWI reflects the degree of pulmonary edema, whatever its cause, and is associated with prognosis.41 Both indices are useful in establishing diagnosis and to aid in fluid management. Given the additional value of volumetric measurements, TPTD should be considered an integral part of hemodynamic assessment. Cardiac function index (CFI) is a derived parameter calculated as cardiac index divided by GEDVI. In patients with cardiogenic shock, CFI reflects LV ejection fraction,42,43 provided that RV function is maintained.43 CFI can be substituted for a PA catheter to identify myocardial depression in septic patients.42

Complications related to hemodynamic monitoring with TPTD are relatively minor and are related to arterial and central venous catheterization (local bleeding and infections).44

HEMODYNAMIC OPTIMIZATION WITH THE PULMONARY ARTERY CATHETER OR TRANSPULMONARY THERMODILUTION Several trials have evaluated the impact of hemodynamic optimization on outcome.26,45–48 Perioperative optimization using a PA catheter resulted in decreased perioperative complications25 and improved survival rate.26 TPTD has also been used for this purpose, with a resultant decrease in perioperative complications.45,49 In other conditions, it has been more difficult to determine if the use of TPTD affects outcome. In patients with cardiogenic shock after cardiac arrest, hemodynamic monitoring with TPTD was associated with higher fluid intake in the first 24 hours and resulted in a lower incidence of acute kidney injury compared with CVP and arterial pressure monitoring.48 In patients with Takotsubo cardiomyopathy related to subarachnoid hemorrhage, a CFI below 4.2/min was predictive of an impaired ejection fraction and an impaired 3-month neurologic outcome.46 Patients with poor neurologic outcome also had high EVLWI values. In a randomized trial, these authors further reported that targeted hemodynamic resuscitation using TPTD indices was associated with better long-term neurologic outcome.47 It is difficult to determine if hemodynamic management with the PA catheter is preferable to management using transpulmonary thermodilution. In a small randomized trial that directly compared the two techniques, pressure-guided resuscitation was superior to volumetric variables, resulting in shorter duration of mechanical ventilation in shock patients with impaired cardiac function, but not in patients with preserved cardiac function. Survival rates in both groups were unaffected.50 Given the absence of major differences in outcome between the different monitoring techniques, the choice of the hemodynamic device should be based on severity of illness and the value of the measured variables to a patient’s specific condition. We suggest a decision algorithm (Fig. 48.1) based on published review articles.2,3,37 The starting point is evaluation of the hemodynamic state with echocardiography for identification of the type of shock and of RV function. In the absence of significant comorbidities and if the patient rapidly improves after initial resuscitation, basic hemodynamic monitoring with arterial and central venous lines, along with measurements of lactate, ScvO2, and PCO2 (partial pressure of carbon dioxide) gradients, may be sufficient. Noninvasive cardiac output measurement may have value by provi­ding continuous evaluation of flow. In complex cases with associated comorbidities, in patients with acute respiratory distress syndrome (ARDS) or cardiac dysfunction

CHAPTER 48

335

Circulatory failure

Initial assessment

Echocardiography

Hypovolemia Distributive

Rapid improvement

ARDS or cardiac dysfunction without RV impairment

ARDS or cardiac dysfunction with RV impairment

TPTD OR PAC

PAC or TPTD + Echo

Complex cases

Arterial + central line ± non inv. Significant hemodynamic changes detected by monitoring

TPTD

Repeat Echocardigraphy

Fig. 48.1  ​Suggested Decision Algorithm for the Selection of Hemodynamic Monitoring Techniques. The algorithm is inspired from published review articles.2,3,37 In addition to the measurements of arterial pressure and CVP (central venous pressure), lactate, ScvO2 (central venous oxygen saturation), and PCO2 (partial pressure of carbon dioxide) gradients are suggested at each hemodynamic assessment. ARDS, acute respiratory distress syndrome; Echo, echocardiography; PAC, pulmonary artery catheter; RV, right ventricular; TPTD, transpulmonary thermodilution.

without RV impairment, or in cases where the patient deteriorates after initial resuscitation, a TPTD system associated with pulse contour analysis provides cardiac volumes and extravascular lung water. In cases of RV dysfunction, the PA catheter is preferred. If the team is inexperienced with the use of the PA catheter, coupling TPTD with echocardiography may be an alternative.

AUTHORS’ RECOMMENDATIONS • Hemodynamic evaluation is often required in critically ill patients. The PA catheter and TPTD can be used for this purpose. • Beyond perioperative optimization, no large-scale trial has demonstrated improved outcome with either the PA catheter or TPTD. • Basic hemodynamic monitoring may be sufficient in simple cases, but invasive hemodynamic monitoring is often needed in complex cases.

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11. Rivers E, Nguyen B, Havstadt S, et al. Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med. 2001;345:1368-1377. 12. Yealy DM, Kellum JA, Huang DT, et al. A randomized trial of protocol-based care for early septic shock. N Engl J Med. 2014;370:1683-1693. 13. Peake SL, Delaney A, Bailey M, et al. Goal-directed resuscitation for patients with early septic shock. N Engl J Med. 2014;371:1496-1506. 14. Mouncey PR, Osborn TM, Power GS, et al. Trial of early, goaldirected resuscitation for septic shock. N Engl J Med. 2015;372:1301-1311. 15. De Backer D, Vincent JL. Early goal-directed therapy: do we have a definitive answer? Intensive Care Med. 2016;42:1048-1050. 16. Angus DC, Barnato AE, Bell D, et al. A systematic review and meta-analysis of early goal-directed therapy for septic shock: the ARISE, ProCESS and ProMISe Investigators. Intensive Care Med. 2015;41:1549-1560. 17. Ventetuolo CE, Klinger JR. Management of acute right ventricular failure in the intensive care unit. Ann Am Thorac Soc. 2014;11:811-822. 18. De Backer D, Marx G, Tan A, et al. Arterial pressure-based cardiac output monitoring: a multicenter validation of the third-generation software in septic patients. Intensive Care Med. 2011;37:233-240. 19. Mimoz O, Rauss A, Rekik N, Brun-Buisson C, Lemaire F, Brochard L. Pulmonary artery catheterization in critically ill patients: a prospective analysis of outcome changes associated with catheter-prompted changes in therapy. Crit Care Med 1994;22:573-579. 20. Wheeler AP, Bernard GR, Thompson BT, et al. Pulmonaryartery versus central venous catheter to guide treatment of acute lung injury. N Engl J Med. 2006;354:2213-2224. 21. Richard C, Warszawski J, Anguel N, et al. Early use of the pulmonary artery catheter and outcomes in patients with shock and acute respiratory distress syndrome: a randomized controlled trial. JAMA. 2003;290:2713-2720. 22. Sandham JD, Hull RD, Brant RF, et al. A randomized, controlled trial of the use of pulmonary-artery catheters in high-risk surgical patients. N Engl J Med. 2003;348:5-14. 23. Binanay C, Califf RM, Hasselblad V, et al. Evaluation study of congestive heart failure and pulmonary artery catheterization effectiveness: the ESCAPE trial. JAMA. 2005;294: 1625-1633. 24. Rajaram SS, Desai NK, Kalra A, et al. Pulmonary artery catheters for adult patients in intensive care. Cochrane Database Syst Rev. 2013;2:CD003408. 25. Pölönen P, Ruokonen E, Hippeläinen M, Pöyhönen M, Takala J. A prospective, randomized study of goal-oriented hemodynamic therapy in cardiac surgical patients. Anesth Analg. 2000;90: 1052-1059. 26. Wilson J, Woods I, Fawcett J, et al. Reducing the risk of major elective surgery: randomised controlled trial of preoperative optimisation of oxygen delivery. BMJ. 1999;318: 1099-1103. 27. Gnaegi A, Feihl F, Perret C. Intensive care physicians’ insufficient knowledge of right-heart catheterization at the bedside: time to act? Crit Care Med. 1997;25:213-220. 28. Iberti TJ, Fischer EP, Leibowitz AB, Panacek EA, Silverstein JH, Albertson TE. A multicenter study of physicians’ knowledge of the pulmonary artery catheter. Pulmonary Artery Catheter Study Group. JAMA. 1990;264:2928-2932.

29. Jain M, Canham M, Upadhyay D, Corbridge T. Variability in interventions with pulmonary artery catheter data. Intensive Care Med. 2003;29:2059-2062. 30. De Backer D. Hemodynamic assessment: the technique or the physician at fault? Intensive Care Med. 2003;29:1865-1867. 31. Wiedemann HP, Wheeler AP, Bernard GR, et al. Comparison of two fluid-management strategies in acute lung injury. N Engl J Med. 2006;354:2564-2575. 32. Allen LA, Rogers JG, Warnica JW, et al. High mortality without ESCAPE: the registry of heart failure patients receiving pulmonary artery catheters without randomization. J Card Fail. 2008;14:661-669. 33. De Backer D, Schortgen F. Physicians declining patient enrollment in clinical trials: what are the implications? Intensive Care Med. 2014;40:117-119. 34. Koo KK, Sun JC, Zhou Q, et al. Pulmonary artery catheters: evolving rates and reasons for use. Crit Care Med. 2011;39:1613-1618. 35. Pandey A, Khera R, Kumar N, Golwala H, Girotra S, Fonarow GC. Use of pulmonary artery catheterization in US patients with heart failure, 2001-2012. JAMA Intern Med. 2016;176:129-132. 36. De Backer D, Vincent JL. The pulmonary artery catheter: is it still alive? Curr Opin Crit Care. 2018;24:204-208. 37. De Backer D, Hajjar LA, Pinsky MR. Is there still a place for the Swan–Ganz catheter? We are not sure. Intensive Care Med. 2018;44:960-962. 38. van Lieshout JJ, Wesseling KH. Continuous cardiac output by pulse contour analysis? Br J Anaesth. 2001;86:467-469. 39. Michard F. Pulse contour analysis: fairy tale or new reality? Crit Care Med. 2007;35:1791-1792. 40. Hamzaoui O, Monnet X, Richard C, Osman D, Chemla D, Teboul JL. Effects of changes in vascular tone on the agreement between pulse contour and transpulmonary thermodilution cardiac output measurements within an up to 6-hour calib­ ration-free period. Crit Care Med. 2008;36:434-440. 41. Jozwiak M, Silva S, Persichini R, et al. Extravascular lung water is an independent prognostic factor in patients with acute respiratory distress syndrome. Crit Care Med. 2013;42:472-480. 42. Ritter S, Rudiger A, Maggiorini M. Transpulmonary thermodilution-derived cardiac function index identifies cardiac dysfunction in acute heart failure and septic patients: an observational study. Crit Care. 2009;13(4):R133. 43. Perny J, Kimmoun A, Perez P, Levy B. Evaluation of cardiac function index as measured by transpulmonary thermodilution as an indicator of left ventricular ejection fraction in cardiogenic shock. Biomed Res Int. 2014;2014:598029. 44. Belda FJ, Aguilar G, Teboul JL, et al. Complications related to less-invasive haemodynamic monitoring. Br J Anaesth. 2011;106:482-486. 45. Goepfert MS, Reuter DA, Akyol D, Lamm P, Kilger E, Goetz AE. Goal-directed fluid management reduces vasopressor and catecholamine use in cardiac surgery patients. Intensive Care Med. 2007;33:96-103. 46. Mutoh T, Kazumata K, Terasaka S, Taki Y, Suzuki A, Ishikawa T. Impact of transpulmonary thermodilution-based cardiac contractility and extravascular lung water measurements on clinical outcome of patients with Takotsubo cardiomyopathy after subarachnoid hemorrhage: a retrospective observational study. Crit Care. 2014;18:482. 47. Mutoh T, Kazumata K, Terasaka S, Taki Y, Suzuki A, Ishikawa T. Early intensive versus minimally invasive approach to postoperative hemodynamic management after subarachnoid hemorrhage. Stroke. 2014;45:1280-1284.

CHAPTER 48 48. Adler C, Reuter H, Seck C, Hellmich M, Zobel C. Fluid therapy and acute kidney injury in cardiogenic shock after cardiac arrest. Resuscitation. 2013;84:194-199. 49. Salzwedel C, Puig J, Carstens A, et al. Perioperative goal-directed hemodynamic therapy based on radial arterial pulse pressure variation and continuous cardiac index trending reduces postoperative

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complications after major abdominal surgery: a multi-center, prospective, randomized study. Crit Care. 2013;17:R191. 50. Trof RJ, Beishuizen A, Cornet AD, de Wit RJ, Girbes AR, Groeneveld AB. Volume-limited versus pressure-limited hemodynamic management in septic and nonseptic shock. Crit Care Med. 2012;40:1177-1185.

e1 Abstract: Hemodynamic monitoring provides important information for the approach of the patient in acute circulatory failure. The reliability of the various nonhemodynamic techniques in severely ill patients is variable and often inversely proportional to its invasiveness. Accordingly, the choice of the hemodynamic technique should not be guided solely on the basis of its invasiveness, but should also take into account the accuracy of the technique and, mostly, the potential interest of the additionally measured variables. The choice of the hemodynamic monitoring device should thus be individualized, and there is clearly still a place for invasive techniques. The role of invasive techniques for hemodynamic monitoring

is discussed in this chapter. The pulmonary artery catheter and transpulmonary thermodilution are the most popular techniques used for invasive hemodynamic monitoring in critically ill patients. Admittedly, no large-scale trial has indicated an improved outcome with these techniques, outside the scope of perioperative hemodynamic optimization. Basic hemodynamic monitoring may be sufficient in simple cases, but invasive hemodynamic monitoring is often needed in complex cases. Keywords: cardiac output, hemodynamic monitoring, pulmonary artery catheter, transpulmonary thermodilution, echocardiography, right ventricle