- Email: [email protected]
Initial Clinical Experience With a Miniaturized Transesophageal Echocardiography Probe in a Cardiac Intensive Care Unit
Initial Clinical Experience With a Miniaturized Transesophageal Echocardiography Probe in a Cardiac Intensive Care Unit Nick Fletcher, MBBS, FRCA, FFICM,*† Martin Geisen, MD,* Hanif Meeran, MBBS, FRCA, FFICM,*† Dominic Spray, MBBS, FRCA, FFICM,*† and Maurizio Cecconi, MD, MD(UK), FRCA, FFICM*† Objective: To investigate the safety of a novel, miniaturized, monoplane transesophageal echocardiography probe (mTEE) and its potential as a hemodynamic monitoring tool. Design: This was a retrospective analysis of the clinical evaluation of a disposable mTEE in ventilated patients with severe cardiogenic shock requiring hemodynamic support. mTEE assessment was performed by operators with mixed levels of TEE training. Information on hemodynamic interventions based on mTEE findings was recorded. Setting: A tertiary university cardiac critical care unit. Participants: Male and female critical care patients admitted to the unit with severe hemodynamic instability. Interventions: Insertion of miniaturized disposable TEE probe and hemodynamic and other critical care interventions based on this and conventional monitoring. Measurements and Main Results: In 41 patients (51.2% female, 73.2% after cardiac surgery), hemodynamic support probe insertion was accomplished without major
I
N THE UNSTABLE PATIENT AFTER cardiac surgery or percutaneous intervention, conventional modalities of hemodynamic monitoring have distinct limitations. Their accuracy frequently is affected by underlying disease, mechanical ventilation and mechanical support.1-4 In this situation, echocardiography provides immediate point-of-care hemodynamic assessment and substantial diagnostic information to the experienced operator. Although transthoracic echocardiography (TTE) is used widely for the assessment of the acutely unstable patient in the intensive care unit (ICU), this is limited by poor windows in the ventilated cardiac patient.2–7 In these patients, transesophageal echocardiography (TEE) can provide superior imaging although concerns exist regarding repeated or prolonged exposure to conventional TEE probe insertion.8–18 Miniaturized TEE probes have been shown to be safe and to provide additional information to conventional monitoring, but further information regarding therapeutic impact is needed.19–23 Initial reports of a recently introduced miniaturized, disposable, monoplane TEE probe (mTEE) with an approved insertion time of up to 72 hours (ClariTEE, ImaCor Inc., Garden City, NY) have been promising .24–28 It was the aim of this study to assess the potential therapeutic impact of this novel device in the medical and surgical cardiac ICUs.
From the *Department of Intensive Care Medicine; and †Department of Anaesthesia, St. Georges Healthcare NHS Trust, London, United Kingdom. An equipment loan for this study was granted by ImaCor, Inc, which provided 50% of the mTEE probes used and loan of the Zura console. The remaining mTEE probes were purchased at normal retail price. Address reprint requests to Nick Fletcher, Department of Anaesthesia, St. George’s Healthcare NHS Trust, London, SW17 0QT, United Kingdom. E-mail: [email protected] © 2015 Elsevier Inc. All rights reserved. 1053-0770/2601-0001$36.00/0 http://dx.doi.org/10.1053/j.jvca.2014.09.016 582
complications. A total of 195 mTEE studies were performed, resulting in changes in therapy in 37 (90.2%) patients based on mTEE findings, leading to an improvement in hemodynamic parameters in 33 (80.5%) patients. Right ventricular (RV) failure was diagnosed in 25 patients (67.6%) and mTEE had a direct therapeutic impact on management of RV failure in 17 patients (68 %). Conclusions: Insertion and operation of a novel, miniaturized transoesophageal echocardiography probe can be performed for up to 72 hours without major complications. Repeated assessment using this device provides complementary information to invasive monitoring in the majority of patients and has an impact on hemodynamic management. & 2015 Elsevier Inc. All rights reserved. KEY WORDS: echocardiography, transesophageal, hemodynamic, critical care, intensive care
METHODS
This was a retrospective analysis of a clinical evaluation of a novel disposable TEE probe in a dedicated 17-bed cardiothoracic ICU of a tertiary referral center. Approval for publication was given by the local Joint Research and Development Office and the responsible hospital officer for patient information governance. The ClariTEE probe is a 5.5-mm monoplane disposable TEE probe approved for an insertion time of up to 72 hours, allowing for continuous hemodynamic assessment or repeated TEE studies without the need for probe reinsertion. The device is connected to a proprietary TEE platform that provides digital storage, area and distance measurements, and color-flow imaging. The group of operators consisted of 5 senior, consultantlevel cardiac intensivists certified in TEE and 4 senior trainees who had completed a 3-day introductory course on basic TEE. The senior trainees were experienced and competent in the hemodynamic management of this group of patients. All operators received 2 hours of simulator-based training on the device initially, and the trainees received ongoing educational support. The training included a standardized, algorithmic approach to image acquisition aiming at obtaining 4 views: A transgastric short-axis view, a midesophageal 4-chamber view, and a midesophageal para-aortic/superior vena cava view; in addition, a modified 4-chamber view focusing on the right ventricle was obtained. A summary of TEE views is provided in Figure 1. Probe insertion was initiated at the discretion of the treating clinician. Insertion criteria were: Mechanically ventilated patients with ongoing severe hemodynamic instability and circulatory shock requiring at least 3 vasoactive agent pharmacologic supports, deemed likely to persist for at least 24 hours. Exclusion criteria were previous esophageal surgery, known gastroesophageal disease associated with strictures or ulcerations and nonavailability of a trained operator. All probes were inserted orally.
Journal of Cardiothoracic and Vascular Anesthesia, Vol 29, No 3 (June), 2015: pp 582–587
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Fig 1. Description of views obtained by mTEE examination. LV ¼ left ventricle, RV ¼ right ventricle, LVEDA ¼ left ventricular end-diastolic area, FAC ¼ fractional area change, SVC ¼ superior vena cava.
All clinical information and data from conventional monitoring such as invasive pressures were assessed by the operators and appropriate hemodynamic interventions were made before imaging with mTEE. Blinding of operators was not attempted. LiDCO is the authors’ first line monitoring technique, but their clinical protocol is to escalate to pulmonary artery (PA) catheter monitoring in all patients on more than 1 vasoactive agent support. Management of these very complex patients does not follow a protocol in normal clinical practice. When additional interventions were made on the basis of information obtained by the mTEE examination, this was then classified as an mTEE effect on therapy. The criteria for a successful mTEE-based intervention were several-fold: A 10% improvement in conventionally measured hemodynamic parameters or other data such as serum lactate or a qualitative visual improvement in ventricular contractility when serial images subsequently were compared. The criteria for successful reduction in therapy were similarly obtained and were defined as when this intervention was not subsequently reversed. Right ventricular failure as imaged on mTEE was defined as a visually significant qualitative reduction in free-wall/long-axis contractility when compared with a normally functioning chamber. Superior vena cava (SVC) collapsibility was measured using maximum and minimum callipered dimensions over a respiratory cycle; collapsibility greater than 30% was taken as an indication for fluid challenge. Impact on sedation was defined as hemodynamic TEE confirmation of improvement in ventricular function such that a sedation hold could be
undertaken. Impact on management of ventilation was modification of positive end-expiratory pressure because of mTEE assessment of severely impaired right ventricular (RV) function. When the trainees were uncertain about image interpretation or an intervention, then this was discussed with one of the senior clinicians. Study information including hemodynamic interventions based on mTEE findings was recorded digitally on the proprietary ultrasound platform contemporaneously and transferred to an electronic spreadsheet. Only interventions based on mTEE assessment were included in the analysis. All images acquired by traineelevel physicians were reviewed by an accredited expert in critical care echocardiography (N.F.) before inclusion into the study. An adequate image on expert review is defined as one in which the area of interest (eg, SVC, left ventricle walls and cavity) can be identified clearly enough to make a functional assessment. Descriptive statistics were performed using GraphPad Prism v.6.00 software (GraphPad Software Inc., La Jolla, CA). The intervention rate in surgical patients as compared to medical patients was compared using unpaired Student’s t-test and Fisher exact test. RESULTS
A total of 41 participants were included (51.2% female) of whom 30 (73.2%) were cardiac surgical patients. All patients were intubated and ventilated at the time of probe insertion. A total of 37 patients (90.2%) received hemodynamic support by
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Table 1. Patient Characteristics No. (%)
Total Participants Female Postcardiac surgery Combined interventions Valvular surgery only CABG only Aortic surgery Nonsurgical patients MI/cardiogenic shock OOHCA Ongoing sepsis/ARDS Hemodynamic support Vasopressors Inotropes IABP ICU mortality Hospital mortality
41 21 (51) 30 (73) 13 6 8 3 11 (27) 8 1 2 41 (100) 41 (100) 37 (90) 3 (7) 15 (37) 16 (39)
Abbreviations: ARDS, acute respiratory distress syndrome; CABG, coronary artery bypass graft; IABP, intra-aortic balloon counterpulsation; ICU, intensive care unit; MI, myocardial infarction; OOHCA, outof-hospital cardiac arrest.
inotropes. Three patients received support by intra-aortic balloon counterpulsation (IABP). Hemodynamic monitoring was based on an indwelling pulmonary artery catheter in 24 (58.5%) patients (Vigilance II Monitor, Edwards Lifesciences, Irvine, CA), the remaining patients received monitoring based on pulse-pressure analysis using the lithium-dilution technique (LiDCOplus, LiDCO Ltd., London, UK). Reasons for noninsertion of a PA catheter included rapid death, failure of insertion, unstable ventricular arrhythmias, or presence of a temporary transvenous pacing wire. ICU mortality was 36.5%,
in-hospital mortality was 39%. A detailed summary of patient characteristics is given in Table 1. Probe insertion was accomplished in all 41 participants at first attempt and was graded as easy. In these patients, 195 mTEE studies were performed (4.8 ⫾ 3.3 studies/patient). The mean indwelling time of the mTEE probe was 27 (26.68 ⫾ 21.46) hours. At least 1 full mTEE examination including the 4 standard views was obtained in 37 (90.2%) patients. Images were acquired by trainee physicians in 29 (70.7%) patients and were found to be of adequate quality on expert review. One hundred eighteen successful changes in therapy targeting cardiovascular dynamics were recorded in 37 out of 41 (90.2%) patients based on mTEE findings. These interventions were made throughout the probe monitoring period (Fig 2). The impact on change of therapy was larger in the surgical group of patients (97% v 73%, p ¼ 0.05). These included changes in inotrope/vasopressor management (n ¼ 52, 44.1%), changes in fluid administration based on SVC collapsibility (n ¼ 48, 40.7%), initiation or optimization of IABP support (n ¼ 6, 5.1%) and adjustment of mechanical ventilation or level of sedation (n ¼ 4, 3.4%). These interventions resulted in improvement of hemodynamic parameters in 33 (80.5%) patients. RV assessment was performed in 37 (90.2%) patients. In these, RV failure was diagnosed in 25 patients (67.6%) and mTEE had a therapeutic impact in its management in 17 patients (68 %). A summary of changes in therapy based on mTEE findings is provided in Table 2. In 4 patients, mTEEguided treatment did not result in a change in the patient’s clinical condition. Complications were recorded in 4 patients. One patient developed a lip ulcer at the location of the indwelling probe. In another patient, the probe was removed following limited aspiration of blood through the nasogastric tube. One probe
Patient number
Timing of hemodynamic intervention 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
Hours since probe insertion Fig 2. Patients in whom mTEE probe remained 4 25 hours. The timing of each intervention is displayed for every patient along a linear timeline. When interventions happened at the same time interval for any one patient, the data points are displayed next to each other. Final data point indicates probe removal not intervention. Median time for intervention was 18.5 hours (IQR 20), IQR ¼ interquartile range.
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Table 2. Impact of mTEE on Clinical Management Postcardiac
Total patients Probe insertion time (hours) No. of studies per participant Recorded clips per participant Full mTEE exam Impact on treatment Changes in inotropes Added fluids Removed fluids Changes in sedation Changes in ventilation Changes in pacemaker Tamponade confirmed PE diagnosed Avoided resternotomy Focused RV assessment RV failure RV targeted therapy initiated
Surgery
Nonsurgical
30 28.3 ⫾ 20.3 5.1 ⫾ 3.5 21.1 ⫾ 12.2 29 (97) 29 (97) 25 (83) 22 (73) 10 (33) 2 2 2 1 1 2 28 (93) 20 (66) 12 (40)
11 22.5 ⫾ 24.7 3.9 ⫾ 2.8 21.6 ⫾ 16 9 (82) 8 (73) 8 (73) 6 (55) 2 (18) 0 0 0 1 1 0 9 (82) 5 (45) 5 (45)
p Value
0.46 0.33 0.92 0.17 0.05 0.66 0.28 0.46
0.29 0.29 1.0
NOTE. Data are number of patients (%). Continuous data are expressed as mean ⫾ SD (standard deviation). Categoric data are expressed as number and percentages. Abbreviations: mTEE, miniaturized transesophageal echocardiography; PE, pulmonary embolism; RV, right ventricle.
was removed because of disruption of the electrical connector. There was 1 inadvertent probe removal. No major adverse incidents to study participants occurred as a result of probe insertion. DISCUSSION
In this report, the authors have described their initial experience using a novel, miniaturized mTEE probe allowing for intermittent hemodynamic assessment using prolonged probe placement for up to 72 hours. The data suggest that this device provided additional information to existing monitors. This information proved valuable in directing clinical decisions in 90% of very ill unstable patients in the cardiac ICU throughout the monitoring period. Interventions based on mTEE assessment led to an improvement of hemodynamic parameters in the majority of patients and crucial information regarding the presence of pericardial effusion or RV dysfunction was obtained. There are a limited number of previously published studies investigating the use of this miniaturized probe. An initial clinical report by Bick et al25 evaluated the device in 13 patients treated in an ICU after out-of hospital cardiac arrest. The same group confirmed the safety and feasibility of the device in a group of 21 cardiac surgery patients. Most notably, monitoring by mTEE was important in the diagnosis of RV failure in onethird of the patients and a high rate of discordance between conventional monitoring devices and episodic mTEE monitoring was observed.26 A recent multicenter study conducted by Vieillard-Baron et al, which included 94 critically ill patients with circulatory failure, demonstrated the safety of probe insertion and the ability to guide hemodynamic management, with a direct therapeutic impact in 68% of all patients.27 The
study population in this publication was mixed general ICU patients predominantly with septic shock; this may explain the higher therapeutic impact in this study (90%) in which the subjects had primary cardiogenic shock. In both of these previous studies, mTEE probes were operated by experienced specialists in TEE, so no conclusions regarding the impact of training on proficiency in image acquisition could be made. This topic has been addressed by another recent study by Cioccari et al28 in which a team of intensivists with no previous experience in TEE tested the feasibility of hemodynamic monitoring using mTEE after receiving 6 hours of introductory training in 55 critically ill patients. The overall learning curve for competence in advanced critical care conventional TEE may be shorter than previously recognized.29 The results of the present study regarding success in achieving adequate image acquisition, safety and impact on hemodynamic management were in keeping with the findings of other recent investigations. In 90.2% of all patients, at least 1 full mTEE study was performed with adequate image quality with no serious complications. Probe insertion time was shorter and therapeutic impact higher in this study population when compared with the previous studies. This most likely reflected the high percentage of hemodynamically compromised patients early after high-risk cardiovascular interventions (cardiac surgery or emergency coronary interventions). Further, early ICU mortality in the present study population was high and may have contributed to the shorter duration of probe insertion. The high mortality observed here was likely because of the high mortality associated with severe cardiogenic shock in this self-selected population. It is important to note the high incidence of RV failure in this study population. Recent demographic trends suggest an increasing prevalence of pre-existing RV dysfunction and pulmonary artery hypertension in patients undergoing cardiothoracic surgery.30–32 The authors were able to use this device successfully to manipulate fluids, vasoactive drugs, and positive end-expiratory pressure in response to RV dysfunction. Resternotomy for pericardial hematoma collection leading to tamponade is a well-known and potentially devastating complication of cardiac surgery. The authors’ experience suggested that the 2D mode in mTEE may be deployed safely to monitor the development and the size of any fluid collection in these patients while ventilated. Other clinically useful applications that were identified during the conduct of the study were: Weaning of vasoactive drugs and mechanical support; ventricular recovery and function following acute myocardial infarction; and confirming the correct positioning of a balloon pump. Although this study was not designed to detect the ability to improve outcomes by earlier detection and improved management of these complications, the authors believed that there was sufficient promise to justify larger outcome studies powered to investigate this hypothesis. This study was not designed to directly compare mTEE with conventional monitoring modalities as echocardiography provides complementary information, which cannot be derived from these techniques. Data from conventional monitoring devices were freely available to the treating clinicians in their decision-making. When changes in management were deemed necessary because of changing clinical conditions, they were
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included in the analysis only if mTEE examination triggered the decision-making. These included decisions of both escalation and de-escalation of therapy. Whereas the authors recorded interventions triggered by mTEE, they were unable to capture when mTEE prevented a harmful intervention such as on-ICU emergency re-sternotomy. Equally, the authors did not seek to compare this novel technique with TTE, which is regarded as the first-line method in the assessment of the acutely deteriorating ICU patient. Particularly in postcardiac surgical patients, the subcostal drains and dressings, mechanical ventilation and poststernotomy, pulmonary, and chest wall sequelae make TTE technically demanding. The authors consider that a high level of TTE expertise is required to accurately assess RV function and pericardial blood collections. This level of ICU TTE expertise generally is not available on a 24-hour basis in the UK. Comparison of TTE imaging with mTEE needs to be addressed and should be incorporated into subsequent studies. It is possible that there was bias in patient selection. The selected population had a high risk of death from circulatory failure so all possible extra information was desirable. It was not clear whether the findings regarding the therapeutic impact of mTEE hold true in a population that is less severely ill. The short duration of the indwelling time in some of the patients may have reflected early death following probe insertion in this study population. Whereas mTEE could perform distance and area measurement (and, hence, fractional area change of the left ventricle could be calculated intermittently), there was no spectral Doppler quantification and the information obtained was mostly qualitative. Assessment of changes in function was made by direct on-screen visual comparison with the previously stored 2D image loops. This lacks precision but is a
commonly used method of assessment in echocardiography practice. The disposable probe is more expensive compared with other available monitor disposables, but the authors did not set out to assess cost-effectiveness in this study. This highrisk group of patients consumed vast amounts of resources in the course of their ICU stay, but in view of the lack of evidence of the influence of mTEE on outcome, cost was not evaluated. TEE, as opposed to TTE, frequently offers superior image quality in ventilated patients and a sustained image plane. Those clinicians who provide intensive care for cardiac surgical and acute cardiology patients often are very familiar with the use of TEE. The last few years have seen an increased awareness of the benefits of echocardiography in critically ill patients and there is a developing body of technical expertise among intensivists.33 Increasing deployment of echocardiography as a complementary modality to invasive monitoring rather than a replacement is now firmly on the agenda.34 However, clinicians must bear in mind the life-cycle of other monitoring devices that have not justified their early promised effect on outcome. The monitor can only detect clinical information; it is clearly the intervention that makes the difference. CONCLUSIONS
Insertion and operation of a novel, miniaturized transesophageal echocardiography probe can be performed without major complications for up to 72 hours. Repeated assessment using this device provides complementary information to invasive monitoring in the majority of patients and has an impact on hemodynamic management.
REFERENCES 1. Pölönen P, Ruokonen E, Hippeläinen M, et al: A prospective, randomized study of goal-oriented hemodynamic therapy in cardiac surgical patients. Anesth Analg 90:1052-1059, 2000 2. Pearse R, Dawson D, Fawcett J, Rhodes A, et al: Early goaldirected therapy after major surgery reduces complications and duration of hospital stay. A randomised, controlled trial. Crit Care 9: 687-693, 2005 3. Aya HD, Cecconi M, Hamilton M, et al: Goal-directed therapy in cardiac surgery: a systematic review and meta-analysis. Br J Anaesth 110:510-517, 2013 4. Alhashemi JA, Cecconi M, Hofer CK: Cardiac output monitoring: an integrative perspective. Crit Care 15:214, 2011 5. Vignon P, Mentec H, Terré S, et al: Diagnostic accuracy and therapeutic impact of transthoracic and transesophageal echocardiography in mechanically ventilated patients in the ICU. Chest 106: 1829-1834, 1994 6. Slama M, Novara A, Van de Putte P, et al: Diagnostic and therapeutic implications of transesophageal echocardiography in medical ICU patients with unexplained shock, hypoxemia, or suspected endocarditis. Intensive Care Med 22:916-922, 1996 7. Schmidlin D, Schuepbach R, Bernard E, et al: Indications and impact of postoperative transesophageal echocardiography in cardiac surgical patients. Crit Care Med 29:2143-2148, 2001 8. Vieillard-Baron A, Slama M, Cholley B, et al: Echocardiography in the intensive care unit: from evolution to revolution? Intensive Care Med 34:243-249, 2008 9. American Society of Anaesthesiologists and Society of Cardiovascular Anesthesiologists Task Force on Transesophageal
Echocardiography: Practice guidelines for perioperative transesophageal echocardiography. An updated report by the American Society of Anesthesiologists and the Society of Cardiovascular Anesthesiologists Task Force on Transesophageal Echocardiography. Anesthesiology 112:1084-1096, 2010 10. Mebazaa A, Pitsis AA, Rudiger A, et al: Clinical review: Practical recommendations on the management of perioperative heart failure in cardiac surgery. Crit Care 14:201, 2010 11. Sutton DC, Kluger R: Intraoperative transoesophageal echocardiography: impact on adult cardiac surgery. Anaesth Intensive Care 26: 287-293, 1998 12. Couture P, Denault AY, McKenty S, et al: Impact of routine use of intraoperative transesophageal echocardiography during cardiac surgery. Can J Anaesth 47:20-26, 2000 13. Forrest P, Lovelock N, Hu J, et al: The impact of intraoperative transoesophageal echocardiography on an unselected cardiac surgical population: A review of 2,343 cases. Anaesth Intensive Care 30:734-741, 2002 14. Hogue CW, Lappas GD, Creswell LL, et al: Swallowing dysfunction after cardiac operations. J Thorac Cardiovasc Surg 110:517-522, 1995 15. Rousou JA, Tighe DA, Garb JL, et al: Risk of dysphagia after transesophageal echocardiography during cardiac operations. Ann Thorac Surg 269:486-490, 2000 16. Kallmeyer IJ, Collard CD, Fox JA, et al: The safety of intraoperative transesophageal echocardiography: a case series of 7200 cardiac surgical patients. Anesth Analg 92:1126-1130, 2001 17. Lennon MJ, Gibbs NM, Weightman WM, et al: Transesophageal echocardiography-related gastrointestinal complications in cardiac surgical patients. J Cardiothorac Vasc Anesth 19:141-145, 2005
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18. Piercy M, McNicol L, Dinh DT, et al: Major complications related to the use of transesophageal echocardiography in cardiac surgery. J Cardiothorac Vasc Anesth 23:62-65, 2009 19. Spencer KT, Krauss D, Thurn J, et al: Transnasal transesophageal echocardiography. J Am Soc Echocardiogr 10:728-737, 2007 20. Spencer KT, Goldman M, Cholley B, et al: Multicenter experience using a new prototype transnasal transesophageal echocardiography probe. Echocardiography 16:811-817, 1999 21. Greim CA, Brederlau J, Kraus I, et al: Transnasal transesophageal echocardiography: a modified application mode for cardiac examination in ventilated patients. Anesth Analg 88:306-311, 1999 22. Zimmermann P, Greim C, Trautner H, et al: Echocardiographic monitoring during induction of general anesthesia with a miniaturized esophageal probe. Anesth Analg 96:21-27, 2003 23. Benjamin E, Griffin K, Leibowitz A, et al: Goal-directed transesophageal echocardiography performed by intensivists to assess left ventricular function: comparison with pulmonary artery catheterization. J Cardiothorac Vasc Anesth 12:10-15, 1998 24. Vignon P, Amiel J-B, Francois B, et al: Evaluation of a miniaturized TEE probe in ventilated ICU patients. Preliminary results. Intensive Care Med 37(suppl):S242, 2012 25. Bick JS, McPherson JA, Schaff J, et al: Initial experience with a disposable transesophageal echocardiography monitoring system during therapeutic hypothermia following out of hospital cardiac arrest. Internet J Emerg Intensive Care Med 12:2, 2012
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26. Maltais S, Costello WT, Billings FT, et al: Episodic Monoplane Echocardiography Impacts Postoperative Management of the Cardiac Surgery Patient. J Cardiothorac Vasc Anesth 27:665-669, 2013 27. Vieillard-Baron A, Slama M, Mayo P, et al: A pilot study on safety and clinical utility of a single-use 72-hour indwelling transesophageal echocardiography probe. Intensive Care Med 39:629-635, 2013 28. Cioccari L, Baur H-R, Berger D, et al: Hemodynamic assessment of critically ill patients using a miniaturized transesophageal echocardiography probe. Crit Care 17:R121, 2013 29. Charron C, Vignon P, Prat G, et al: Number of supervised studies required to reach competence in advanced critical care transesophageal echocardiography. Intensive Care Med 39:1019-1024, 2013 30. Haddad F, Couture P, Tousignant C, Denault AY: The right ventricle in cardiac surgery, a perioperative perspective: II. Pathophysiology, clinical importance, and management. Anesth Analg 108:422-433, 2009 31. Strumpher J, Jacobsohn E: Pulmonary hypertension and right ventricular dysfunction: physiology and perioperative management. J Cardiothorac Vasc Anesth 25:687-704, 2011 32. Denault A, Deschamps A, Tardif JC, et al: Pulmonary hypertension in cardiac surgery. Curr Cardiol Rev 6:1-14, 2010 33. Fletcher SN, Grounds RM: Critical care echocardiography: cleared for take up. Br J Anaesth 109:490-492, 2012 34. Geisen M, Spray D, Fletcher SN: Echocardiography based haemodynamic management in the cardiac surgical ICU Review. J Cardiothorac Vasc Anaesth 28:733-744, 2014
I
N THE UNSTABLE PATIENT AFTER cardiac surgery or percutaneous intervention, conventional modalities of hemodynamic monitoring have distinct limitations. Their accuracy frequently is affected by underlying disease, mechanical ventilation and mechanical support.1-4 In this situation, echocardiography provides immediate point-of-care hemodynamic assessment and substantial diagnostic information to the experienced operator. Although transthoracic echocardiography (TTE) is used widely for the assessment of the acutely unstable patient in the intensive care unit (ICU), this is limited by poor windows in the ventilated cardiac patient.2–7 In these patients, transesophageal echocardiography (TEE) can provide superior imaging although concerns exist regarding repeated or prolonged exposure to conventional TEE probe insertion.8–18 Miniaturized TEE probes have been shown to be safe and to provide additional information to conventional monitoring, but further information regarding therapeutic impact is needed.19–23 Initial reports of a recently introduced miniaturized, disposable, monoplane TEE probe (mTEE) with an approved insertion time of up to 72 hours (ClariTEE, ImaCor Inc., Garden City, NY) have been promising .24–28 It was the aim of this study to assess the potential therapeutic impact of this novel device in the medical and surgical cardiac ICUs.
From the *Department of Intensive Care Medicine; and †Department of Anaesthesia, St. Georges Healthcare NHS Trust, London, United Kingdom. An equipment loan for this study was granted by ImaCor, Inc, which provided 50% of the mTEE probes used and loan of the Zura console. The remaining mTEE probes were purchased at normal retail price. Address reprint requests to Nick Fletcher, Department of Anaesthesia, St. George’s Healthcare NHS Trust, London, SW17 0QT, United Kingdom. E-mail: [email protected] © 2015 Elsevier Inc. All rights reserved. 1053-0770/2601-0001$36.00/0 http://dx.doi.org/10.1053/j.jvca.2014.09.016 582
complications. A total of 195 mTEE studies were performed, resulting in changes in therapy in 37 (90.2%) patients based on mTEE findings, leading to an improvement in hemodynamic parameters in 33 (80.5%) patients. Right ventricular (RV) failure was diagnosed in 25 patients (67.6%) and mTEE had a direct therapeutic impact on management of RV failure in 17 patients (68 %). Conclusions: Insertion and operation of a novel, miniaturized transoesophageal echocardiography probe can be performed for up to 72 hours without major complications. Repeated assessment using this device provides complementary information to invasive monitoring in the majority of patients and has an impact on hemodynamic management. & 2015 Elsevier Inc. All rights reserved. KEY WORDS: echocardiography, transesophageal, hemodynamic, critical care, intensive care
METHODS
This was a retrospective analysis of a clinical evaluation of a novel disposable TEE probe in a dedicated 17-bed cardiothoracic ICU of a tertiary referral center. Approval for publication was given by the local Joint Research and Development Office and the responsible hospital officer for patient information governance. The ClariTEE probe is a 5.5-mm monoplane disposable TEE probe approved for an insertion time of up to 72 hours, allowing for continuous hemodynamic assessment or repeated TEE studies without the need for probe reinsertion. The device is connected to a proprietary TEE platform that provides digital storage, area and distance measurements, and color-flow imaging. The group of operators consisted of 5 senior, consultantlevel cardiac intensivists certified in TEE and 4 senior trainees who had completed a 3-day introductory course on basic TEE. The senior trainees were experienced and competent in the hemodynamic management of this group of patients. All operators received 2 hours of simulator-based training on the device initially, and the trainees received ongoing educational support. The training included a standardized, algorithmic approach to image acquisition aiming at obtaining 4 views: A transgastric short-axis view, a midesophageal 4-chamber view, and a midesophageal para-aortic/superior vena cava view; in addition, a modified 4-chamber view focusing on the right ventricle was obtained. A summary of TEE views is provided in Figure 1. Probe insertion was initiated at the discretion of the treating clinician. Insertion criteria were: Mechanically ventilated patients with ongoing severe hemodynamic instability and circulatory shock requiring at least 3 vasoactive agent pharmacologic supports, deemed likely to persist for at least 24 hours. Exclusion criteria were previous esophageal surgery, known gastroesophageal disease associated with strictures or ulcerations and nonavailability of a trained operator. All probes were inserted orally.
Journal of Cardiothoracic and Vascular Anesthesia, Vol 29, No 3 (June), 2015: pp 582–587
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mTEE IN A CARDIAC ICU
Fig 1. Description of views obtained by mTEE examination. LV ¼ left ventricle, RV ¼ right ventricle, LVEDA ¼ left ventricular end-diastolic area, FAC ¼ fractional area change, SVC ¼ superior vena cava.
All clinical information and data from conventional monitoring such as invasive pressures were assessed by the operators and appropriate hemodynamic interventions were made before imaging with mTEE. Blinding of operators was not attempted. LiDCO is the authors’ first line monitoring technique, but their clinical protocol is to escalate to pulmonary artery (PA) catheter monitoring in all patients on more than 1 vasoactive agent support. Management of these very complex patients does not follow a protocol in normal clinical practice. When additional interventions were made on the basis of information obtained by the mTEE examination, this was then classified as an mTEE effect on therapy. The criteria for a successful mTEE-based intervention were several-fold: A 10% improvement in conventionally measured hemodynamic parameters or other data such as serum lactate or a qualitative visual improvement in ventricular contractility when serial images subsequently were compared. The criteria for successful reduction in therapy were similarly obtained and were defined as when this intervention was not subsequently reversed. Right ventricular failure as imaged on mTEE was defined as a visually significant qualitative reduction in free-wall/long-axis contractility when compared with a normally functioning chamber. Superior vena cava (SVC) collapsibility was measured using maximum and minimum callipered dimensions over a respiratory cycle; collapsibility greater than 30% was taken as an indication for fluid challenge. Impact on sedation was defined as hemodynamic TEE confirmation of improvement in ventricular function such that a sedation hold could be
undertaken. Impact on management of ventilation was modification of positive end-expiratory pressure because of mTEE assessment of severely impaired right ventricular (RV) function. When the trainees were uncertain about image interpretation or an intervention, then this was discussed with one of the senior clinicians. Study information including hemodynamic interventions based on mTEE findings was recorded digitally on the proprietary ultrasound platform contemporaneously and transferred to an electronic spreadsheet. Only interventions based on mTEE assessment were included in the analysis. All images acquired by traineelevel physicians were reviewed by an accredited expert in critical care echocardiography (N.F.) before inclusion into the study. An adequate image on expert review is defined as one in which the area of interest (eg, SVC, left ventricle walls and cavity) can be identified clearly enough to make a functional assessment. Descriptive statistics were performed using GraphPad Prism v.6.00 software (GraphPad Software Inc., La Jolla, CA). The intervention rate in surgical patients as compared to medical patients was compared using unpaired Student’s t-test and Fisher exact test. RESULTS
A total of 41 participants were included (51.2% female) of whom 30 (73.2%) were cardiac surgical patients. All patients were intubated and ventilated at the time of probe insertion. A total of 37 patients (90.2%) received hemodynamic support by
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Table 1. Patient Characteristics No. (%)
Total Participants Female Postcardiac surgery Combined interventions Valvular surgery only CABG only Aortic surgery Nonsurgical patients MI/cardiogenic shock OOHCA Ongoing sepsis/ARDS Hemodynamic support Vasopressors Inotropes IABP ICU mortality Hospital mortality
41 21 (51) 30 (73) 13 6 8 3 11 (27) 8 1 2 41 (100) 41 (100) 37 (90) 3 (7) 15 (37) 16 (39)
Abbreviations: ARDS, acute respiratory distress syndrome; CABG, coronary artery bypass graft; IABP, intra-aortic balloon counterpulsation; ICU, intensive care unit; MI, myocardial infarction; OOHCA, outof-hospital cardiac arrest.
inotropes. Three patients received support by intra-aortic balloon counterpulsation (IABP). Hemodynamic monitoring was based on an indwelling pulmonary artery catheter in 24 (58.5%) patients (Vigilance II Monitor, Edwards Lifesciences, Irvine, CA), the remaining patients received monitoring based on pulse-pressure analysis using the lithium-dilution technique (LiDCOplus, LiDCO Ltd., London, UK). Reasons for noninsertion of a PA catheter included rapid death, failure of insertion, unstable ventricular arrhythmias, or presence of a temporary transvenous pacing wire. ICU mortality was 36.5%,
in-hospital mortality was 39%. A detailed summary of patient characteristics is given in Table 1. Probe insertion was accomplished in all 41 participants at first attempt and was graded as easy. In these patients, 195 mTEE studies were performed (4.8 ⫾ 3.3 studies/patient). The mean indwelling time of the mTEE probe was 27 (26.68 ⫾ 21.46) hours. At least 1 full mTEE examination including the 4 standard views was obtained in 37 (90.2%) patients. Images were acquired by trainee physicians in 29 (70.7%) patients and were found to be of adequate quality on expert review. One hundred eighteen successful changes in therapy targeting cardiovascular dynamics were recorded in 37 out of 41 (90.2%) patients based on mTEE findings. These interventions were made throughout the probe monitoring period (Fig 2). The impact on change of therapy was larger in the surgical group of patients (97% v 73%, p ¼ 0.05). These included changes in inotrope/vasopressor management (n ¼ 52, 44.1%), changes in fluid administration based on SVC collapsibility (n ¼ 48, 40.7%), initiation or optimization of IABP support (n ¼ 6, 5.1%) and adjustment of mechanical ventilation or level of sedation (n ¼ 4, 3.4%). These interventions resulted in improvement of hemodynamic parameters in 33 (80.5%) patients. RV assessment was performed in 37 (90.2%) patients. In these, RV failure was diagnosed in 25 patients (67.6%) and mTEE had a therapeutic impact in its management in 17 patients (68 %). A summary of changes in therapy based on mTEE findings is provided in Table 2. In 4 patients, mTEEguided treatment did not result in a change in the patient’s clinical condition. Complications were recorded in 4 patients. One patient developed a lip ulcer at the location of the indwelling probe. In another patient, the probe was removed following limited aspiration of blood through the nasogastric tube. One probe
Patient number
Timing of hemodynamic intervention 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
Hours since probe insertion Fig 2. Patients in whom mTEE probe remained 4 25 hours. The timing of each intervention is displayed for every patient along a linear timeline. When interventions happened at the same time interval for any one patient, the data points are displayed next to each other. Final data point indicates probe removal not intervention. Median time for intervention was 18.5 hours (IQR 20), IQR ¼ interquartile range.
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mTEE IN A CARDIAC ICU
Table 2. Impact of mTEE on Clinical Management Postcardiac
Total patients Probe insertion time (hours) No. of studies per participant Recorded clips per participant Full mTEE exam Impact on treatment Changes in inotropes Added fluids Removed fluids Changes in sedation Changes in ventilation Changes in pacemaker Tamponade confirmed PE diagnosed Avoided resternotomy Focused RV assessment RV failure RV targeted therapy initiated
Surgery
Nonsurgical
30 28.3 ⫾ 20.3 5.1 ⫾ 3.5 21.1 ⫾ 12.2 29 (97) 29 (97) 25 (83) 22 (73) 10 (33) 2 2 2 1 1 2 28 (93) 20 (66) 12 (40)
11 22.5 ⫾ 24.7 3.9 ⫾ 2.8 21.6 ⫾ 16 9 (82) 8 (73) 8 (73) 6 (55) 2 (18) 0 0 0 1 1 0 9 (82) 5 (45) 5 (45)
p Value
0.46 0.33 0.92 0.17 0.05 0.66 0.28 0.46
0.29 0.29 1.0
NOTE. Data are number of patients (%). Continuous data are expressed as mean ⫾ SD (standard deviation). Categoric data are expressed as number and percentages. Abbreviations: mTEE, miniaturized transesophageal echocardiography; PE, pulmonary embolism; RV, right ventricle.
was removed because of disruption of the electrical connector. There was 1 inadvertent probe removal. No major adverse incidents to study participants occurred as a result of probe insertion. DISCUSSION
In this report, the authors have described their initial experience using a novel, miniaturized mTEE probe allowing for intermittent hemodynamic assessment using prolonged probe placement for up to 72 hours. The data suggest that this device provided additional information to existing monitors. This information proved valuable in directing clinical decisions in 90% of very ill unstable patients in the cardiac ICU throughout the monitoring period. Interventions based on mTEE assessment led to an improvement of hemodynamic parameters in the majority of patients and crucial information regarding the presence of pericardial effusion or RV dysfunction was obtained. There are a limited number of previously published studies investigating the use of this miniaturized probe. An initial clinical report by Bick et al25 evaluated the device in 13 patients treated in an ICU after out-of hospital cardiac arrest. The same group confirmed the safety and feasibility of the device in a group of 21 cardiac surgery patients. Most notably, monitoring by mTEE was important in the diagnosis of RV failure in onethird of the patients and a high rate of discordance between conventional monitoring devices and episodic mTEE monitoring was observed.26 A recent multicenter study conducted by Vieillard-Baron et al, which included 94 critically ill patients with circulatory failure, demonstrated the safety of probe insertion and the ability to guide hemodynamic management, with a direct therapeutic impact in 68% of all patients.27 The
study population in this publication was mixed general ICU patients predominantly with septic shock; this may explain the higher therapeutic impact in this study (90%) in which the subjects had primary cardiogenic shock. In both of these previous studies, mTEE probes were operated by experienced specialists in TEE, so no conclusions regarding the impact of training on proficiency in image acquisition could be made. This topic has been addressed by another recent study by Cioccari et al28 in which a team of intensivists with no previous experience in TEE tested the feasibility of hemodynamic monitoring using mTEE after receiving 6 hours of introductory training in 55 critically ill patients. The overall learning curve for competence in advanced critical care conventional TEE may be shorter than previously recognized.29 The results of the present study regarding success in achieving adequate image acquisition, safety and impact on hemodynamic management were in keeping with the findings of other recent investigations. In 90.2% of all patients, at least 1 full mTEE study was performed with adequate image quality with no serious complications. Probe insertion time was shorter and therapeutic impact higher in this study population when compared with the previous studies. This most likely reflected the high percentage of hemodynamically compromised patients early after high-risk cardiovascular interventions (cardiac surgery or emergency coronary interventions). Further, early ICU mortality in the present study population was high and may have contributed to the shorter duration of probe insertion. The high mortality observed here was likely because of the high mortality associated with severe cardiogenic shock in this self-selected population. It is important to note the high incidence of RV failure in this study population. Recent demographic trends suggest an increasing prevalence of pre-existing RV dysfunction and pulmonary artery hypertension in patients undergoing cardiothoracic surgery.30–32 The authors were able to use this device successfully to manipulate fluids, vasoactive drugs, and positive end-expiratory pressure in response to RV dysfunction. Resternotomy for pericardial hematoma collection leading to tamponade is a well-known and potentially devastating complication of cardiac surgery. The authors’ experience suggested that the 2D mode in mTEE may be deployed safely to monitor the development and the size of any fluid collection in these patients while ventilated. Other clinically useful applications that were identified during the conduct of the study were: Weaning of vasoactive drugs and mechanical support; ventricular recovery and function following acute myocardial infarction; and confirming the correct positioning of a balloon pump. Although this study was not designed to detect the ability to improve outcomes by earlier detection and improved management of these complications, the authors believed that there was sufficient promise to justify larger outcome studies powered to investigate this hypothesis. This study was not designed to directly compare mTEE with conventional monitoring modalities as echocardiography provides complementary information, which cannot be derived from these techniques. Data from conventional monitoring devices were freely available to the treating clinicians in their decision-making. When changes in management were deemed necessary because of changing clinical conditions, they were
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included in the analysis only if mTEE examination triggered the decision-making. These included decisions of both escalation and de-escalation of therapy. Whereas the authors recorded interventions triggered by mTEE, they were unable to capture when mTEE prevented a harmful intervention such as on-ICU emergency re-sternotomy. Equally, the authors did not seek to compare this novel technique with TTE, which is regarded as the first-line method in the assessment of the acutely deteriorating ICU patient. Particularly in postcardiac surgical patients, the subcostal drains and dressings, mechanical ventilation and poststernotomy, pulmonary, and chest wall sequelae make TTE technically demanding. The authors consider that a high level of TTE expertise is required to accurately assess RV function and pericardial blood collections. This level of ICU TTE expertise generally is not available on a 24-hour basis in the UK. Comparison of TTE imaging with mTEE needs to be addressed and should be incorporated into subsequent studies. It is possible that there was bias in patient selection. The selected population had a high risk of death from circulatory failure so all possible extra information was desirable. It was not clear whether the findings regarding the therapeutic impact of mTEE hold true in a population that is less severely ill. The short duration of the indwelling time in some of the patients may have reflected early death following probe insertion in this study population. Whereas mTEE could perform distance and area measurement (and, hence, fractional area change of the left ventricle could be calculated intermittently), there was no spectral Doppler quantification and the information obtained was mostly qualitative. Assessment of changes in function was made by direct on-screen visual comparison with the previously stored 2D image loops. This lacks precision but is a
commonly used method of assessment in echocardiography practice. The disposable probe is more expensive compared with other available monitor disposables, but the authors did not set out to assess cost-effectiveness in this study. This highrisk group of patients consumed vast amounts of resources in the course of their ICU stay, but in view of the lack of evidence of the influence of mTEE on outcome, cost was not evaluated. TEE, as opposed to TTE, frequently offers superior image quality in ventilated patients and a sustained image plane. Those clinicians who provide intensive care for cardiac surgical and acute cardiology patients often are very familiar with the use of TEE. The last few years have seen an increased awareness of the benefits of echocardiography in critically ill patients and there is a developing body of technical expertise among intensivists.33 Increasing deployment of echocardiography as a complementary modality to invasive monitoring rather than a replacement is now firmly on the agenda.34 However, clinicians must bear in mind the life-cycle of other monitoring devices that have not justified their early promised effect on outcome. The monitor can only detect clinical information; it is clearly the intervention that makes the difference. CONCLUSIONS
Insertion and operation of a novel, miniaturized transesophageal echocardiography probe can be performed without major complications for up to 72 hours. Repeated assessment using this device provides complementary information to invasive monitoring in the majority of patients and has an impact on hemodynamic management.
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