- Email: [email protected]
Transoesophageal echocardiography during orthotopic liver transplantation
Rev Esp Anestesiol Reanim. 2017;64(9):522---527
Revista Española de Anestesiología y Reanimación www.elsevier.es/redar
CONTINUING EDUCATION
Transoesophageal echocardiography during orthotopic liver transplantation夽,夽夽 J. Acosta Martínez ∗ , D. López-Herrera Rodríguez, D. González Rubio, J.L. López Romero Facultativo Especialista de Área, Unidad de Gestión Clínica de Anestesiología y Reanimación, Hospital General Virgen del Rocío, Seville, Spain Received 10 November 2016; accepted 10 January 2017 Available online 18 August 2017
KEYWORDS Transoesophageal echocardiography; Liver transplantation; Haemodynamic monitoring
Abstract Despite the importance of haemodynamic management in patients undergoing liver transplantation, there is currently no consensus on the most appropriate type of monitoring to use. In this context, transoesophageal echocardiography can provide useful information to professionals, although their use constraints prevent further spread today. © 2017 Sociedad Espa˜ nola de Anestesiolog´ıa, Reanimaci´ on y Terap´ eutica del Dolor. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.
PALABRAS CLAVE
Ecocardiografía transesofágica durante el trasplante ortotópico hepático
Ecocardiografía transesofágica; Trasplante hepático; Monitorización hemodinámica
Resumen A pesar de la importancia del manejo hemodinámico en los pacientes sometidos a trasplante hepático, en la actualidad no existe consenso acerca del tipo de monitorización más apropiada a emplear. En este contexto, la ecocardiografía transesofágica puede aportar información muy útil a los profesionales implicados, aunque sus limitaciones impiden que se extienda su uso aún más en la actualidad. © 2017 Sociedad Espa˜ nola de Anestesiolog´ıa, Reanimaci´ on y Terap´ eutica del Dolor. Publicado por Elsevier Espa˜ na, S.L.U. Todos los derechos reservados.
夽 Please cite this article as: Acosta Martínez J, López-Herrera Rodríguez D, González Rubio D, López Romero JL. Ecocardiografía transesofágica durante el trasplante ortotópico hepático. Rev Esp Anestesiol Reanim. 2017;64:522---527. 夽夽 This article is part of the Anaesthesiology and Resuscitation Continuing Medical Education Program. An evaluation of the questions on this article can be made through the Internet by accessing the Education Section of the following web page: www.elsevier.es/redar ∗ Corresponding author. E-mail address: [email protected] (J. Acosta Martínez).
2341-1929/© 2017 Sociedad Espa˜ nola de Anestesiolog´ıa, Reanimaci´ on y Terap´ eutica del Dolor. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.
Transoesophageal echocardiography during orthotopic liver transplantation
Introduction Patients with end-stage liver disease that are candidates for orthotopic liver transplantation (OLT) present a series of cardiovascular manifestations typical of liver disease (cirrhosis, the main indication for OLT, is characterized by haemodynamic derangement with high cardiac output [CO], decreased peripheral vascular resistance and cirrhotic cardiomyopathy). These, when added to coexisting cardiovascular disease processes associated with advanced age and acute intraoperative haemodynamic changes, have a significant effect on anaesthetic management during OLT.1,2 Despite the importance of intraoperative haemodynamic management, there is currently no consensus on the type of monitoring to be used in this type of intervention. One of the most widely used monitoring strategies in recent years is transoesophageal echocardiography (TOE). Although this technique provides comprehensive qualitative and quantitative information, it is not without limitations.3
Development Advanced monitoring systems in liver transplantation As will be described below, the different phases of OLT are associated with important haemodynamic alterations, and it is therefore essential to identify the cause of these in order to correct them. Invasive arterial monitoring is essential, but is insufficient to achieve intraoperative targets, so different monitoring modalities have been developed, each with its advantages and drawbacks.4,5 Pulmonary artery catheter The pulmonary arterial catheter (PAC) has been --- and continues to be --- the mainstay of haemodynamic monitor during OLT. Central venous pressure and pulmonary artery occlusion pressure have traditionally been used as preload parameters, although they have been shown to poorly correlate with changes in CO.6 In addition, the latest PAC systems can measure CO by continuous thermodilution, bearing in mind that large volume fluid replacement, vascular short circuits and hepatic reperfusion can distort the measurements obtained. PAC is probably now more widely used for direct measurement of pulmonary arterial pressures, especially in patients with portopulmonary hypertension. Although mild and moderate pulmonary hypertension is not an absolute contraindication for OLT, it has been associated with an increase in perioperative mortality.7 PAC is also used to measure mixed venous oxygen saturation, although it has shown poor correlation with CO during OLT.
Pulse wave analysis Several different monitoring systems base the measurement of haemodynamic parameters on arterial pulse
523
waveforms, using either transpulmonary thermodilution ® ® (PiCCO or Edwards-EV1000 , for example) or other tech® ® niques (FloTrac/Vigileo , MostCare , among others). The findings of studies performed to validate these monitors have been contradictory, and they have been shown to correlate poorly with CO measured by PAC (to date, the gold standard) in patients with low peripheral vascular resistance. An additional advantage of these monitors is that they measure dynamic fluid responsiveness parameters (variations in systolic volume and pulse pressure). These can only be obtained in patients presenting sinus rhythm and certain ventilatory conditions (absence of inspiratory efforts and VT > 8 ml/kg). Despite these limitations, the use of these minimally invasive monitors, which require a conventional central line and a central or peripheral arterial catheter, depending on the type of monitor), in becoming more widespread in the context of OLT.
Overview of TOE in OLT TOE provides a comprehensive assessment of the patient’s haemodynamic status, and can identify alterations related to volaemia, biventricular contractile activity, mechanical complications or situations specific to OLT, such as pulmonary embolism, hypertrophic obstructive cardiomyopathy, the presence of patent foramen ovale (PFO) or pulmonary hypertension. Potential TOE-related complications and the long learning curve associated with the technique have meant that it is rarely used in clinical practice. Surveys performed in US hospitals have shown that routine use of TOE during OLT ranges from 11%8 to 38%,9 although up to 80% of centres claim to use it occasionally for rescue situations or special circumstances.9 While 20 TOE views are essential for a comprehensive intraoperative evaluation, the latest guidelines published by the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists (ASE and SCA, respectively) recommend that anaesthesiologists should be familiar with at least 11 views.10 Evaluation of circulating volume and fluid responsiveness Correct determination of circulating volume is the cornerstone of haemodynamic management in patients undergoing OLT. The use of filling pressure (central venous pressure, pulmonary artery occlusion pressure) parameters to guide fluid replacement therapy has declined in recent years, mainly because of the poor correlation between pressure and left ventricle (LV) volume (due to, for example, differences in LV distensibility). Ultrasound or the use of dynamic parameters to determine volume dependence give an adequate estimate of preload. Measuring LV end-diastolic area or diameter is a simple method of estimating preload. These parameters can be obtained from mid-oesophageal 4-chamber or transgastric short axis views.2 The most widely used dynamic fluid responsiveness parameter, meanwhile, is the caval index, which measures the difference between expiratory inferior vena cava
524 (IVC) diameter and inspiratory IVC diameter (>12% indicates response). This index, however, is less reliable in patients under mechanical ventilation, for whom some investigators have suggested using the diameter of the superior vena cava. In these cases, the cut-off point for responders is around 30%. Another dynamic parameter that can be calculated is the variation in peak aortic flow velocity; a value greater than 15% indicates a favourable response to fluid replacement. A recent prospective, multicentre study11 in 540 patients compared the foregoing parameters in patients under mechanical ventilation (superior and inferior vena cava diameter), as well as the variation in arterial pulse pressure and in IVC diameter. They defined fluid responsiveness as a 10% increase in the aortic velocity time integral ratio in the left ventricular outflow tract. They found that superior vena cava variability had the best specificity (84%) and ICV had the best sensitivity (79%) to fluid responsiveness.
J. Acosta Martínez et al. Table 1 Contraindications echocardiography.
Use of TOE according to the stage of surgery OLT is characterized by 3 stages, each with distinct haemodynamic events: the dissection or preanhepatic phase, the anhepatic phase, and the postreperfusion phase. The haemodynamic pattern can vary considerably at each stage of the procedure, and TOE provides useful information to guide the management strategy. Dissection (preanhepatic) phase This phase begins with the cutaneous incision and ends when the portal vein is clamped. The main cause of haemodynamic instability in this phase is sudden changes in blood volume,
transoesophageal
Absolute
Relative
Oesophageal disease: stenosis, trauma, tumour, scleroderma, Mallory---Weiss syndrome, diverticulum Puncture Oesophagectomy
Atlantooaxial subluxation
Recent upper GI surgery Active GI bleeding
Contraindications for TOE in OLT One of the reasons why use of TOE is not more widespread in patients that are candidates for OLT is the fear of bleeding due to laceration of oesophageal varices, which occurs in up to 80% of patients undergoing TOE.12 Despite this, the presence of oesophageal varices is considered a relative contraindication, although it is wiser to avoid using riskier (for example, transgastric) views. Several studies have evaluated the safety of TOE during OLT, and have found little evidence of an increased risk of bleeding from oesophageal varices, although most are small, retrospective studies.13,14 In conclusion, if TOE is unavoidable due to the haemodynamic status of the patient (and transthoracic echocardiography or noninvasive monitoring have been ruled out), the presence of oesophageal varices is not an absolute contraindication. A recent review1 makes specific recommendations relating to the technique to be used in patients with oesophageal varices undergoing a TOE study: preoperative endoscopic surveillance, oropharyngeal examination, limiting probe manipulation, and use of the most experienced operator for the examination, and the use of rigid laryngoscope in the case of difficult insertion. Absolute and relative contraindications for TOE are summarized in Table 1.
for
Severe cervical arthritis Oesophagitis, peptic ulcer Symptomatic hiatal hernia History of GI surgery Recent upper GI bleeding Thoracoabdominal aneurysm Barrett’s Oesophagus Dysphagia Coagulopathy, thrombocytopenia History of thoracic radiotherapy
GI: gastrointestinal.
with a high risk of bleeding (favoured by coagulopathy, portal hypertension and surgical complexity) and other volume losses (ascitic fluid, venous congestion, etc.). IVC clamping at the end of this phase causes an abrupt decrease in venous return and, subsequently, CO. It is increasingly common at present to use the so-called piggyback technique, which consists of partial clamping of the IVC (suprahepatic veins), which maintains venous flow. By measuring preload (diameter and end-diastolic area), TOE allows surgeons to optimize fluid management. It can also identify right ventricular failure, and can assist in the placement of transcutaneous veno-venous bypass lines if needed (risk of air embolism or accidental decannulation).15,16 According to a recent retrospective study of 100 patients (Shillcutt et al.17 ), the most common TOE finding at this stage of OLT is PFO with left-right shunt (16%), followed by hyperdynamic LV function (11%) and the presence of intracardiac thrombus (8%). None of these findings were associated with major cardiovascular complications (atrial fibrillation, non-fatal myocardial infarction, congestive heart failure, pulmonary embolism, stroke) or increased mortality. Anhepatic phase This starts at vascular clamping and continues until reperfusion of the graft, and therefore includes vascular anastomosis. It is mainly characterized by haemodynamic changes caused by venous clamping (especially when using conventional techniques), which reduces venous return and increases splanchnic and IVC pressure.
Transoesophageal echocardiography during orthotopic liver transplantation Echocardiographic views (mid-oesophageal 4-chamber or transgastric short axis) provide useful information on preload and biventricular function. TOE can distinguish between 2 very frequent entities during OLT --- hypovolaemia and loss of systemic vascular resistance --- by comparing the LV end-diastolic and end-systolic area (or diameter) ratio; a decrease in both would indicate hypovolaemia, whereas a decrease in end-systolic area would point to a loss of resistance. Echocardiographic abnormalities are found in up to 56% of cases.17 The most frequent findings are right ventricular dysfunction (15%), hypovolaemia (12%), PFO (11%) and biventricular dysfunction (10%). None of these are associated with a higher rate of major cardiovascular events or mortality.
Reperfusion phase This phase is mainly characterized by a sudden increase in venous return to the right ventricle (RV), which can lead to volume overload and trigger pulmonary oedema in patients with diagnosed or silent heart failure. The bestknown event in this phase is the so-called reperfusion syndrome, in which blood pressure drops by at least 30% for 1 min or more in the first 5 min following reperfusion. Abrupt decrease in blood pressure may be accompanied by bradyarrhythmias, loss of vascular resistance, and increased pulmonary artery and wedge pressure. This is due to the sudden release of cold, acidotic, and hyperkalemic preservation fluid along with vasoactive mediators into the circulation.1,2 Echocardiographic findings in this phase range from volume overload secondary to rapid increase in flow following unclamping (increased left ventricular end-diastolic area), to possible biventricular dysfunction. Continuous monitoring of the transition from the anhepatic to the reperfusion phase allows identification of intracardiac air, thrombosis, ventriculoauricular regurgitation, or circulatory obstruction. High pulmonary pressure or PFO (usually transient) can also be diagnosed during this phase of OLT. As in previous stages, the mid-oesophageal 4 chamber and the transgastric short axis views are the most useful. Echocardiographic findings are more common in this phase (77%),17 with the most frequent being the presence of microemboli (40%, snowflake pattern), followed by right ventricular dysfunction (22%) and intracardiac thrombi (18%). The presence of biventricular dysfunction in this phase (13% of cases) has been associated with an increase in mortality and the incidence of major cardiovascular events at 1 month and 1 year.
Entities rarely associated with OLT As mentioned previously, haemodynamic instability arising during OLT can be very striking, and the choice of the appropriate corrective action will depend on establishing an adequate differential diagnosis. In addition, certain pathological entities that present in OLT patients and can be
525
detected using TOE predispose patients to intraoperative hypoxaemia. Patent foramen ovale and hepatopulmonary syndrome Despite being very prevalent, PFO is a silent entity that only produces symptoms when pressure in the right atrium exceed that in the left, which can trigger hypoxaemia and paradoxical embolisms. There are several events that may reverse normal (left atrial > right atrium) intracardiac pressure during OLT: mechanical ventilation, systemic hypotension, reperfusion syndrome, increased intra-abdominal pressure, acute pulmonary hypertension, etc. In spite of its potential clinical relevance, PFO is not an absolute contraindication for OLT.18 TOE can distinguish PFO from another entity that can also cause hypoxaemia in this type of patient: hepatopulmonary syndrome. The appearance of air bubbles after more than 3 cardiac cycles when administering agitated saline is indicative of intra-pulmonary shunt, and supports the diagnosis of hepatopulmonary syndrome. Pulmonary embolism The balance between pro- and antihemostatic states in patients with end-stage liver disease is unstable, causing both bleeding and thrombosis. In addition, both the surgical stimulus and vascular clamping predispose to pulmonary embolism, and this is why anaesthesiologists must be trained to diagnose this entity. Although not the gold standard, TOE can identify signs that support the diagnosis of pulmonary embolism, since direct diagnosis is very rare.19 Findings consist of signs of RV dilation, RV hypokinesia, regional alterations in RV motility, elevated pulmonary pressures, atrial and/or interventricular septal defect, and RV dysfunction (lower TAPSE). Obstruction of the left ventricular outflow tract Hypertrophic cardiomyopathy in the cirrhotic patients predisposes to the appearance of this entity, especially in the presence of hypovolaemia and tachycardia. This phenomenon occurs more frequently during dissection and anhepatic, and can therefore be identified on a midoesophageal long axis view by associating the degree of obstruction with that of mitral regurgitation.20 The pathophysiological event linking LV outflow tract obstruction with mitral regurgitation is systolic anterior motion of the mitral valve. This movement is caused by the Venturi effect, which arises due to the pressure gradient at the level of the LV outflow tract. Portopulmonary hypertension Portal and pulmonary hypertension may present up to 8.5% of OLT patients. It is characterized by mean pulmonary arterial pressure > 25 mmHg at rest, wedge pressure < 15 mmHg, pulmonary vascular resistance > 240 dyn/s/cm−5 and portal hypertension. These patients have a high risk of RV dysfunction, which is why in many hospitals it is considered a contraindicated for OLT. Echocardiographic findings include RV hypertrophy, RV dilation and dysfunction, and paradoxical septal motion.21
526 Table 2 view.
J. Acosta Martínez et al. Transoesophageal echocardiography findings, by
TOE view ME4C
Angle 0---20◦
ME LAX
120---150◦
TG SAX
0---20◦
Relevant findings Biventricular function and size Volaemia Intracardiac air Septal defects Intracardiac air LVOT obstruction ASM Segmental motility Volaemia Can be difficult to obtain due to gastric retraction
ASM: anterior systolic movement; LVOT: left ventricular outflow tract; ME4C: mid-oesophageal 4-chamber; ME LAX: midoesophageal long axis; TG SAX: transgastric short axis; TOE: transoesophageal echocardiography.
Conclusions The importance of echocardiography monitoring, particularly TOE, to obtain a direct, comprehensive picture of intraoperative haemodynamic status is gaining recognition, and its use has increased in recent years. TOE can identify even the rarest entities that cause haemodynamic instability, and is now used more frequently as a monitoring technique in the context of OLT. Despite this, the advantages TOE must be carefully weighed up against its potential complications, particularly bleeding from esophagogastric varices which, though common in cirrhotic patients, is not an absolute contraindication for the use of TOE. Although mastery of TOE requires extensive training, the technique has been simplified with the establishment of a series of basic views that provide the most useful information at each stage of OLT. These are summarized in Table 2.
Conflict of interest The authors declare they have no conflicts of interest.
References 1. Robertson AC, Eagle SS. Transesophageal echocardiography duting orthotopic liver transplantation: maximizing information without the distraction. J Cardiothorac Vasc Anesth. 2014;28:141---54. 2. De Pietri L, Mocchegiani F, Leuzzi C, Montalti R, Vivarelli M, Agnoletti V. Tranoesophageal echocardiography during liver transplantation. World J Hepatol. 2015;7:2432---48. 3. Krenn CG, de Wolf AM. Current approach to intraoperative monitoring in liver trasplantation. Curr Opin Organ Transplant. 2008;13:285---90.
4. Rudnick MR, de Marchi L, Plotkin JS. Hemodynamic monitoring during liver transplantation. World J Hepatol. 2015;7: 1302---11. 5. Mellado Miras P, Villegas Duque D, Rusiecka M. Monitorización hemodinámica en trasplante hepático. In: Hospital Universitario Virgen del Rocío. 1000 trasplantes hepáticos. Sevilla: Servicio Andaluz de Salud; 2014. p. 137---43. 6. Costa MG, Chiarandini P, Della Rocca G. Hemodynamics during liver transplantation. Transplant Proc. 2007;39: 1871---3. 7. Krowka MJ, Mandell MS, Ramsay MA, Kawut SM, Fallon MB, Manzarbeitia C, et al. Hepatopulmonary syndrome and portopulmonary hypertension: a report of a multicenter liver transplant database. Liver Transpl. 2004;10: 174---82. 8. Schumann R. Intraoperative resource utilization in anesthesia for liver transplantation in the United States: a survey. Anesth Analg. 2003;97:21---8. 9. Soong M, Sherwani SS, Ault ML, Baudo AM, Herborn JC, de Wolf AM. United States practice patterns in the use of transesophageal echocardiography during adult liver transplantation. J Cardiothorac Vasc Anesth. 2014;28: 635---9. 10. Reeves ST, Finley AC, Skubas NJ, Swaminathan M, Whitley WS, Glas KE, et al. Basic perioperative transesophageal echocardiography examination: a consensus statement of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists. J Am Soc Echocardiogr. 2013;26: 443---56. 11. Vignon P, Repessé X, Bégot E, Léger J, Jacob C, Bouferrache K, et al. Comparision of echocardiographic indices used to predict fluid responsiveness in ventilated patients. Am J Respir Crit Care Med. 2016 (in press). 12. Burger-Klepp U, Karatosic R, Thum M, Schwarzer R, Fuhrmann V, Hetz H, et al. Transesophageal echocardiography during orthotopic liver transplantation in patients with esophagogastric varices. Transplantation. 2012;94:192---6. 13. Spier BJ, Larue SJ, Teelin TC, Leff JA, Swize LR, Borkan SH, et al. Review of complications in a series of patients with known gastro-esophageal varices undergoing transesophageal echocardiography. J Am Soc Echocardiogr. 2009;22: 393---400. 14. Markin NW, Sharma A, Grant W, Shillcutt SK. The safety of transesophageal echocardiography in patients undergoing liver transplantation. J Cardiothorac Vasc Anesth. 2015;29: 588---93. 15. Burtenshaw AJ, Isaac JL. The role of trans-oesophageal echocardiography for perioperative cardiovascular monitoring during orthotopic liver transplantation. Liver Transpl. 2006;12:1577---83. 16. Torbicki A, Perrier A, Konstantinides S, Agnelli G, Galiè N, Pruszczyk P, et al. Guidelines on the diagnosis and management of acute pulmonary embolism: the Task Force for the diagnosis and management of acute pulmonary embolism of the European Society of Cardiology (ESC). Eur Heart J. 2008;29: 2276---315. 17. Shillcutt SK, Ringenberg KJ, Chacon MM, Brakke TR, Montzingo CR, Lyden ER, et al. Liver trasplantation: intraoperative transesophageal echocardiography findings and relationship to major postoperative adverse cardiac events. J Cardiothorac Vasc Anesth. 2016;30:107---14. 18. Alba AC, Verocai Flaman F, Granton J, Delgado DH. Patent foramen ovale does not have a negative impact on early outcomes in patients undergoing liver transplantation. Clin Transplant. 2011;25:151---5.
Transoesophageal echocardiography during orthotopic liver transplantation 19. Rosenberger P, Shernan SK, Body SC, Eltzschig HK. Utility of intraoperative transesophageal echocardiography for diagnosis of pulmonary embolism. Anesth Analg. 2004;99:12---6. 20. Roy D, Ralley FE. Anesthetic management of a patient with dynamic left ventricular outflow tract obstruction with systolic
527
anterior movement of the mitral valve undergoing redoorthotopic liver transplantation. J Cardiothorac Vasc Anesth. 2012;26:274---6. 21. Safdar Z, Bartolome S, Sussman N. Portopulmonary hypertension: an update. Liver Transpl. 2012;18:881---91.
Revista Española de Anestesiología y Reanimación www.elsevier.es/redar
CONTINUING EDUCATION
Transoesophageal echocardiography during orthotopic liver transplantation夽,夽夽 J. Acosta Martínez ∗ , D. López-Herrera Rodríguez, D. González Rubio, J.L. López Romero Facultativo Especialista de Área, Unidad de Gestión Clínica de Anestesiología y Reanimación, Hospital General Virgen del Rocío, Seville, Spain Received 10 November 2016; accepted 10 January 2017 Available online 18 August 2017
KEYWORDS Transoesophageal echocardiography; Liver transplantation; Haemodynamic monitoring
Abstract Despite the importance of haemodynamic management in patients undergoing liver transplantation, there is currently no consensus on the most appropriate type of monitoring to use. In this context, transoesophageal echocardiography can provide useful information to professionals, although their use constraints prevent further spread today. © 2017 Sociedad Espa˜ nola de Anestesiolog´ıa, Reanimaci´ on y Terap´ eutica del Dolor. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.
PALABRAS CLAVE
Ecocardiografía transesofágica durante el trasplante ortotópico hepático
Ecocardiografía transesofágica; Trasplante hepático; Monitorización hemodinámica
Resumen A pesar de la importancia del manejo hemodinámico en los pacientes sometidos a trasplante hepático, en la actualidad no existe consenso acerca del tipo de monitorización más apropiada a emplear. En este contexto, la ecocardiografía transesofágica puede aportar información muy útil a los profesionales implicados, aunque sus limitaciones impiden que se extienda su uso aún más en la actualidad. © 2017 Sociedad Espa˜ nola de Anestesiolog´ıa, Reanimaci´ on y Terap´ eutica del Dolor. Publicado por Elsevier Espa˜ na, S.L.U. Todos los derechos reservados.
夽 Please cite this article as: Acosta Martínez J, López-Herrera Rodríguez D, González Rubio D, López Romero JL. Ecocardiografía transesofágica durante el trasplante ortotópico hepático. Rev Esp Anestesiol Reanim. 2017;64:522---527. 夽夽 This article is part of the Anaesthesiology and Resuscitation Continuing Medical Education Program. An evaluation of the questions on this article can be made through the Internet by accessing the Education Section of the following web page: www.elsevier.es/redar ∗ Corresponding author. E-mail address: [email protected] (J. Acosta Martínez).
2341-1929/© 2017 Sociedad Espa˜ nola de Anestesiolog´ıa, Reanimaci´ on y Terap´ eutica del Dolor. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.
Transoesophageal echocardiography during orthotopic liver transplantation
Introduction Patients with end-stage liver disease that are candidates for orthotopic liver transplantation (OLT) present a series of cardiovascular manifestations typical of liver disease (cirrhosis, the main indication for OLT, is characterized by haemodynamic derangement with high cardiac output [CO], decreased peripheral vascular resistance and cirrhotic cardiomyopathy). These, when added to coexisting cardiovascular disease processes associated with advanced age and acute intraoperative haemodynamic changes, have a significant effect on anaesthetic management during OLT.1,2 Despite the importance of intraoperative haemodynamic management, there is currently no consensus on the type of monitoring to be used in this type of intervention. One of the most widely used monitoring strategies in recent years is transoesophageal echocardiography (TOE). Although this technique provides comprehensive qualitative and quantitative information, it is not without limitations.3
Development Advanced monitoring systems in liver transplantation As will be described below, the different phases of OLT are associated with important haemodynamic alterations, and it is therefore essential to identify the cause of these in order to correct them. Invasive arterial monitoring is essential, but is insufficient to achieve intraoperative targets, so different monitoring modalities have been developed, each with its advantages and drawbacks.4,5 Pulmonary artery catheter The pulmonary arterial catheter (PAC) has been --- and continues to be --- the mainstay of haemodynamic monitor during OLT. Central venous pressure and pulmonary artery occlusion pressure have traditionally been used as preload parameters, although they have been shown to poorly correlate with changes in CO.6 In addition, the latest PAC systems can measure CO by continuous thermodilution, bearing in mind that large volume fluid replacement, vascular short circuits and hepatic reperfusion can distort the measurements obtained. PAC is probably now more widely used for direct measurement of pulmonary arterial pressures, especially in patients with portopulmonary hypertension. Although mild and moderate pulmonary hypertension is not an absolute contraindication for OLT, it has been associated with an increase in perioperative mortality.7 PAC is also used to measure mixed venous oxygen saturation, although it has shown poor correlation with CO during OLT.
Pulse wave analysis Several different monitoring systems base the measurement of haemodynamic parameters on arterial pulse
523
waveforms, using either transpulmonary thermodilution ® ® (PiCCO or Edwards-EV1000 , for example) or other tech® ® niques (FloTrac/Vigileo , MostCare , among others). The findings of studies performed to validate these monitors have been contradictory, and they have been shown to correlate poorly with CO measured by PAC (to date, the gold standard) in patients with low peripheral vascular resistance. An additional advantage of these monitors is that they measure dynamic fluid responsiveness parameters (variations in systolic volume and pulse pressure). These can only be obtained in patients presenting sinus rhythm and certain ventilatory conditions (absence of inspiratory efforts and VT > 8 ml/kg). Despite these limitations, the use of these minimally invasive monitors, which require a conventional central line and a central or peripheral arterial catheter, depending on the type of monitor), in becoming more widespread in the context of OLT.
Overview of TOE in OLT TOE provides a comprehensive assessment of the patient’s haemodynamic status, and can identify alterations related to volaemia, biventricular contractile activity, mechanical complications or situations specific to OLT, such as pulmonary embolism, hypertrophic obstructive cardiomyopathy, the presence of patent foramen ovale (PFO) or pulmonary hypertension. Potential TOE-related complications and the long learning curve associated with the technique have meant that it is rarely used in clinical practice. Surveys performed in US hospitals have shown that routine use of TOE during OLT ranges from 11%8 to 38%,9 although up to 80% of centres claim to use it occasionally for rescue situations or special circumstances.9 While 20 TOE views are essential for a comprehensive intraoperative evaluation, the latest guidelines published by the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists (ASE and SCA, respectively) recommend that anaesthesiologists should be familiar with at least 11 views.10 Evaluation of circulating volume and fluid responsiveness Correct determination of circulating volume is the cornerstone of haemodynamic management in patients undergoing OLT. The use of filling pressure (central venous pressure, pulmonary artery occlusion pressure) parameters to guide fluid replacement therapy has declined in recent years, mainly because of the poor correlation between pressure and left ventricle (LV) volume (due to, for example, differences in LV distensibility). Ultrasound or the use of dynamic parameters to determine volume dependence give an adequate estimate of preload. Measuring LV end-diastolic area or diameter is a simple method of estimating preload. These parameters can be obtained from mid-oesophageal 4-chamber or transgastric short axis views.2 The most widely used dynamic fluid responsiveness parameter, meanwhile, is the caval index, which measures the difference between expiratory inferior vena cava
524 (IVC) diameter and inspiratory IVC diameter (>12% indicates response). This index, however, is less reliable in patients under mechanical ventilation, for whom some investigators have suggested using the diameter of the superior vena cava. In these cases, the cut-off point for responders is around 30%. Another dynamic parameter that can be calculated is the variation in peak aortic flow velocity; a value greater than 15% indicates a favourable response to fluid replacement. A recent prospective, multicentre study11 in 540 patients compared the foregoing parameters in patients under mechanical ventilation (superior and inferior vena cava diameter), as well as the variation in arterial pulse pressure and in IVC diameter. They defined fluid responsiveness as a 10% increase in the aortic velocity time integral ratio in the left ventricular outflow tract. They found that superior vena cava variability had the best specificity (84%) and ICV had the best sensitivity (79%) to fluid responsiveness.
J. Acosta Martínez et al. Table 1 Contraindications echocardiography.
Use of TOE according to the stage of surgery OLT is characterized by 3 stages, each with distinct haemodynamic events: the dissection or preanhepatic phase, the anhepatic phase, and the postreperfusion phase. The haemodynamic pattern can vary considerably at each stage of the procedure, and TOE provides useful information to guide the management strategy. Dissection (preanhepatic) phase This phase begins with the cutaneous incision and ends when the portal vein is clamped. The main cause of haemodynamic instability in this phase is sudden changes in blood volume,
transoesophageal
Absolute
Relative
Oesophageal disease: stenosis, trauma, tumour, scleroderma, Mallory---Weiss syndrome, diverticulum Puncture Oesophagectomy
Atlantooaxial subluxation
Recent upper GI surgery Active GI bleeding
Contraindications for TOE in OLT One of the reasons why use of TOE is not more widespread in patients that are candidates for OLT is the fear of bleeding due to laceration of oesophageal varices, which occurs in up to 80% of patients undergoing TOE.12 Despite this, the presence of oesophageal varices is considered a relative contraindication, although it is wiser to avoid using riskier (for example, transgastric) views. Several studies have evaluated the safety of TOE during OLT, and have found little evidence of an increased risk of bleeding from oesophageal varices, although most are small, retrospective studies.13,14 In conclusion, if TOE is unavoidable due to the haemodynamic status of the patient (and transthoracic echocardiography or noninvasive monitoring have been ruled out), the presence of oesophageal varices is not an absolute contraindication. A recent review1 makes specific recommendations relating to the technique to be used in patients with oesophageal varices undergoing a TOE study: preoperative endoscopic surveillance, oropharyngeal examination, limiting probe manipulation, and use of the most experienced operator for the examination, and the use of rigid laryngoscope in the case of difficult insertion. Absolute and relative contraindications for TOE are summarized in Table 1.
for
Severe cervical arthritis Oesophagitis, peptic ulcer Symptomatic hiatal hernia History of GI surgery Recent upper GI bleeding Thoracoabdominal aneurysm Barrett’s Oesophagus Dysphagia Coagulopathy, thrombocytopenia History of thoracic radiotherapy
GI: gastrointestinal.
with a high risk of bleeding (favoured by coagulopathy, portal hypertension and surgical complexity) and other volume losses (ascitic fluid, venous congestion, etc.). IVC clamping at the end of this phase causes an abrupt decrease in venous return and, subsequently, CO. It is increasingly common at present to use the so-called piggyback technique, which consists of partial clamping of the IVC (suprahepatic veins), which maintains venous flow. By measuring preload (diameter and end-diastolic area), TOE allows surgeons to optimize fluid management. It can also identify right ventricular failure, and can assist in the placement of transcutaneous veno-venous bypass lines if needed (risk of air embolism or accidental decannulation).15,16 According to a recent retrospective study of 100 patients (Shillcutt et al.17 ), the most common TOE finding at this stage of OLT is PFO with left-right shunt (16%), followed by hyperdynamic LV function (11%) and the presence of intracardiac thrombus (8%). None of these findings were associated with major cardiovascular complications (atrial fibrillation, non-fatal myocardial infarction, congestive heart failure, pulmonary embolism, stroke) or increased mortality. Anhepatic phase This starts at vascular clamping and continues until reperfusion of the graft, and therefore includes vascular anastomosis. It is mainly characterized by haemodynamic changes caused by venous clamping (especially when using conventional techniques), which reduces venous return and increases splanchnic and IVC pressure.
Transoesophageal echocardiography during orthotopic liver transplantation Echocardiographic views (mid-oesophageal 4-chamber or transgastric short axis) provide useful information on preload and biventricular function. TOE can distinguish between 2 very frequent entities during OLT --- hypovolaemia and loss of systemic vascular resistance --- by comparing the LV end-diastolic and end-systolic area (or diameter) ratio; a decrease in both would indicate hypovolaemia, whereas a decrease in end-systolic area would point to a loss of resistance. Echocardiographic abnormalities are found in up to 56% of cases.17 The most frequent findings are right ventricular dysfunction (15%), hypovolaemia (12%), PFO (11%) and biventricular dysfunction (10%). None of these are associated with a higher rate of major cardiovascular events or mortality.
Reperfusion phase This phase is mainly characterized by a sudden increase in venous return to the right ventricle (RV), which can lead to volume overload and trigger pulmonary oedema in patients with diagnosed or silent heart failure. The bestknown event in this phase is the so-called reperfusion syndrome, in which blood pressure drops by at least 30% for 1 min or more in the first 5 min following reperfusion. Abrupt decrease in blood pressure may be accompanied by bradyarrhythmias, loss of vascular resistance, and increased pulmonary artery and wedge pressure. This is due to the sudden release of cold, acidotic, and hyperkalemic preservation fluid along with vasoactive mediators into the circulation.1,2 Echocardiographic findings in this phase range from volume overload secondary to rapid increase in flow following unclamping (increased left ventricular end-diastolic area), to possible biventricular dysfunction. Continuous monitoring of the transition from the anhepatic to the reperfusion phase allows identification of intracardiac air, thrombosis, ventriculoauricular regurgitation, or circulatory obstruction. High pulmonary pressure or PFO (usually transient) can also be diagnosed during this phase of OLT. As in previous stages, the mid-oesophageal 4 chamber and the transgastric short axis views are the most useful. Echocardiographic findings are more common in this phase (77%),17 with the most frequent being the presence of microemboli (40%, snowflake pattern), followed by right ventricular dysfunction (22%) and intracardiac thrombi (18%). The presence of biventricular dysfunction in this phase (13% of cases) has been associated with an increase in mortality and the incidence of major cardiovascular events at 1 month and 1 year.
Entities rarely associated with OLT As mentioned previously, haemodynamic instability arising during OLT can be very striking, and the choice of the appropriate corrective action will depend on establishing an adequate differential diagnosis. In addition, certain pathological entities that present in OLT patients and can be
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detected using TOE predispose patients to intraoperative hypoxaemia. Patent foramen ovale and hepatopulmonary syndrome Despite being very prevalent, PFO is a silent entity that only produces symptoms when pressure in the right atrium exceed that in the left, which can trigger hypoxaemia and paradoxical embolisms. There are several events that may reverse normal (left atrial > right atrium) intracardiac pressure during OLT: mechanical ventilation, systemic hypotension, reperfusion syndrome, increased intra-abdominal pressure, acute pulmonary hypertension, etc. In spite of its potential clinical relevance, PFO is not an absolute contraindication for OLT.18 TOE can distinguish PFO from another entity that can also cause hypoxaemia in this type of patient: hepatopulmonary syndrome. The appearance of air bubbles after more than 3 cardiac cycles when administering agitated saline is indicative of intra-pulmonary shunt, and supports the diagnosis of hepatopulmonary syndrome. Pulmonary embolism The balance between pro- and antihemostatic states in patients with end-stage liver disease is unstable, causing both bleeding and thrombosis. In addition, both the surgical stimulus and vascular clamping predispose to pulmonary embolism, and this is why anaesthesiologists must be trained to diagnose this entity. Although not the gold standard, TOE can identify signs that support the diagnosis of pulmonary embolism, since direct diagnosis is very rare.19 Findings consist of signs of RV dilation, RV hypokinesia, regional alterations in RV motility, elevated pulmonary pressures, atrial and/or interventricular septal defect, and RV dysfunction (lower TAPSE). Obstruction of the left ventricular outflow tract Hypertrophic cardiomyopathy in the cirrhotic patients predisposes to the appearance of this entity, especially in the presence of hypovolaemia and tachycardia. This phenomenon occurs more frequently during dissection and anhepatic, and can therefore be identified on a midoesophageal long axis view by associating the degree of obstruction with that of mitral regurgitation.20 The pathophysiological event linking LV outflow tract obstruction with mitral regurgitation is systolic anterior motion of the mitral valve. This movement is caused by the Venturi effect, which arises due to the pressure gradient at the level of the LV outflow tract. Portopulmonary hypertension Portal and pulmonary hypertension may present up to 8.5% of OLT patients. It is characterized by mean pulmonary arterial pressure > 25 mmHg at rest, wedge pressure < 15 mmHg, pulmonary vascular resistance > 240 dyn/s/cm−5 and portal hypertension. These patients have a high risk of RV dysfunction, which is why in many hospitals it is considered a contraindicated for OLT. Echocardiographic findings include RV hypertrophy, RV dilation and dysfunction, and paradoxical septal motion.21
526 Table 2 view.
J. Acosta Martínez et al. Transoesophageal echocardiography findings, by
TOE view ME4C
Angle 0---20◦
ME LAX
120---150◦
TG SAX
0---20◦
Relevant findings Biventricular function and size Volaemia Intracardiac air Septal defects Intracardiac air LVOT obstruction ASM Segmental motility Volaemia Can be difficult to obtain due to gastric retraction
ASM: anterior systolic movement; LVOT: left ventricular outflow tract; ME4C: mid-oesophageal 4-chamber; ME LAX: midoesophageal long axis; TG SAX: transgastric short axis; TOE: transoesophageal echocardiography.
Conclusions The importance of echocardiography monitoring, particularly TOE, to obtain a direct, comprehensive picture of intraoperative haemodynamic status is gaining recognition, and its use has increased in recent years. TOE can identify even the rarest entities that cause haemodynamic instability, and is now used more frequently as a monitoring technique in the context of OLT. Despite this, the advantages TOE must be carefully weighed up against its potential complications, particularly bleeding from esophagogastric varices which, though common in cirrhotic patients, is not an absolute contraindication for the use of TOE. Although mastery of TOE requires extensive training, the technique has been simplified with the establishment of a series of basic views that provide the most useful information at each stage of OLT. These are summarized in Table 2.
Conflict of interest The authors declare they have no conflicts of interest.
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