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Timing of focused cardiac ultrasound during advanced life support – A prospective clinical study
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Timing of focused cardiac ultrasound during advanced life support – A prospective clinical study夽 Rasmus Aagaard a,b , Bo Løfgren a,c,∗ , Thorbjørn Grøfte b , Erik Sloth d , Roni R. Nielsen e , Christian A. Frederiksen e , Asger Granfeldt d , Morten T. Bøtker d,f a
Research Center for Emergency Medicine, Aarhus University Hospital, Noerrebrogade 44, Building 1B, 1st Floor, 8000 Aarhus C, Denmark Department of Anaesthesiology, Randers Regional Hospital, Skovlyvej 15, 8930 Randers NOE, Denmark c Department of Internal Medicine, Randers Regional Hospital, Skovlyvej 15, 8930 Randers NOE, Denmark d Department of Anaesthesiology and Intensive Care Medicine, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark e Department of Cardiology, Aarhus University Hospital,Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark f Research & Development, Prehospital Emergency Medical Services, Central Denmark Region, Olof Palmes Allé 34, 1st Floor, 8200 Aarhus N, Denmark b
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Article history: Received 5 September 2017 Received in revised form 24 November 2017 Accepted 10 December 2017 Keyword: Focused cardiac ultrasound In-hospital cardiac arrest Image quality
a b s t r a c t Introduction: Focused cardiac ultrasound can potentially identify reversible causes of cardiac arrest during advanced life support (ALS), but data on the timing of image acquisition are lacking. This study aimed to compare the quality of images obtained during rhythm analysis, bag-mask ventilations, and chest compressions. Methods: Adult patients in cardiac arrest were prospectively included during 23 months at a Danish community hospital. Physicians who had completed basic ultrasound training performed subcostal focused cardiac ultrasound during rhythm analysis, bag-mask ventilations, and chest compressions. Image quality was categorised as either useful for interpretation or not. Two echocardiography experts rated images useful for interpretation if all the following characteristics could be determined: 1) right ventricle larger than left ventricle, 2) pericardial fluid, and 3) collapsing ventricles. Results: Images were obtained from 60 of 114 patients undergoing ALS. A higher proportion of the images obtained during rhythm analysis and bag-mask ventilations were useful for interpretation when compared with chest compressions (rhythm analysis vs chest compressions: OR 2.2 (95%CI 1.3–3.8), P = 0.005; bag mask ventilations vs chest compressions: OR 2.0 (95%CI 1.1–3.7), P = 0.03). There was no difference between images obtained during rhythm analysis and bag-mask ventilations (OR 1.1 (95%CI 0.6–2.0), P = 0.74). Conclusion: The quality of focused cardiac ultrasound images obtained during rhythm analysis and bagmask ventilations was superior to that of images obtained during chest compressions. There was no difference in the quality of images obtained during rhythm analysis and bag-mask ventilations. Bag-mask ventilations may constitute an overlooked opportunity for image acquisition during ALS. © 2017 Published by Elsevier Ireland Ltd.
Introduction International resuscitation guidelines stipulate that focused cardiac ultrasound has potential to identify reversible causes of cardiac arrest during advanced life support (ALS) [1,2]. The International Liaison Committee on Resuscitation ALS Task Force state that there
夽 A Spanish translated version of the abstract of this article appears as Appendix in the final online version at https://doi.org/10.1016/j.resuscitation.2017.12.012. ∗ Corresponding author at: Department of Internal Medicine, Regional Hospital Randers, Skovlyvej 15, 8930 Randers NE, Denmark. E-mail address: [email protected] (B. Løfgren).
is inadequate evidence to evaluate whether cardiac ultrasound is of benefit during ALS and recommends that ultrasound should not interfere with the ALS algorithm [3]. This poses a challenge to ultrasound image acquisition. Previous studies have demonstrated that focused cardiac ultrasound can be obtained during either a rhythm analysis or a separate interruption in chest compressions, if both are extended for up to 10 s [4,5]. The quality of images obtained during other phases of the ALS algorithm, i.e. during bag-mask ventilations or chest compressions, has not been investigated. In patients with spontaneous circulation, a deep inspiration enhances image quality when the ultrasound transducer is in a subcostal position [6]. The same could apply during bag-mask ventilations in patients undergoing
https://doi.org/10.1016/j.resuscitation.2017.12.012 0300-9572/© 2017 Published by Elsevier Ireland Ltd.
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resuscitation, but there may not be sufficient time for transducer adjustment and positive pressure ventilation may compromise image quality by causing lung-shadowing. During chest compressions, there is ample time to adjust the ultrasound transducer, but movement of the thorax may compromise image quality. The aim of this study was to compare the quality of focused cardiac ultrasound images obtained during rhythm analysis, bagmask ventilations, and chest compressions. We hypothesised that the quality of images obtained during rhythm analysis is superior to that of images obtained during bagmask ventilations and chest compressions. Methods Study design and setting In this prospective, observational study, patients were included from February 16, 2015 to December 31, 2016 in a Danish community hospital (Regional Hospital Randers, Denmark, catchment area: ∼230,000 inhabitants, annual admissions: ∼36,500 patients). Acute and elective medical and surgical patients are treated at the hospital. Ethics The hospital resuscitation committee approved the study. The ethics committee of the Central Denmark Region regarded the study as a quality assurance project and waived approval and informed consent. The resuscitation team was informed that no intended action was to be interrupted, delayed, or omitted because of ultrasound image acquisition, especially not defibrillation and chest compressions. The physicians performing ultrasonography were instructed to convey any ultrasonography information that they believed should influence treatment of the patient to the resuscitation team. Participants Focused cardiac ultrasound was performed on consecutive patients (≥18 years) undergoing ALS, by physicians who were either anaesthesiology registrars in their final year of training or consultant anaesthesiologists, 24 h a day during the study period.
depth of 18 cm and recording of 5-s ultrasound loops. A commercial cart designed for the ultrasound apparatus was used (SafeLock Cart, GE Healthcare, Little Chalfont, UK). Subcostal ultrasound imaging was performed during rhythm analysis, bag-mask ventilations, and chest compressions, during the ALS algorithm [1]. The anaesthesiologists were instructed to save at least one loop during each of the three phases but could save up to 10 per patient. During focused cardiac ultrasound, a form was completed to mark the ALS phase in which each image was obtained. Focused cardiac ultrasound was not performed, if 1) resuscitation was terminated or return of spontaneous circulation (ROSC) was achieved before the arrival of the ultrasound apparatus, 2) the anaesthesiologist was involved in other tasks related to the resuscitation of the patient, or 3) the anaesthesiologist was occupied with other medical emergencies at the hospital. Study endpoints The primary study endpoint was the proportion of images useful for interpretation as assessed by twoechocardiography experts (CAF, RRN) certified by the Danish Society of Cardiology. An image was rated useful for interpretation if the experts assessed that the quality of the image was sufficient to determine the presence of all the following predefined ultrasound characteristics: 1) right ventricle larger than the left ventricle (yes/no), 2) pericardial fluid present (yes/no), and 3) collapsing ventricles present (yes/no). If one or more of these characteristics could not be determined, the image was rated not useful for interpretation. The echocardiography experts were blinded to both the patient and phase of acquisition and reviewed images in a randomised order using a computer equipped with EchoPACTM (GE Healthcare, Little Chalfont, UK). As a secondary endpoint, the senior anaesthesiologists evaluated images using the same method as the echocardiography experts. They used the screen of the ultrasound apparatus and were not blinded to the phase in which images were obtained. Other secondary endpoints were 1) the presence of ultrasound characteristics (right ventricle larger than left, pericardial fluid, collapsing ventricles) assessed by the experts, given sufficient image quality, 2) whether pericardial fluid was assessed by the experts to measure more than 1 cm from the epicardium to the parietal pericardium, 3) primary causes of cardiac arrest among the included patients.
Focused cardiac ultrasound education Other data collection The use of focused cardiac ultrasound in the Department of Anaesthesiology, Regional Hospital Randers was implemented by a previously described educational program in fall 2012 [7]. Briefly, the training consisted of a commercial available e-learning (usabcd. org, Aarhus, Denmark), a one-day hands-on course, and 10 supervised focused cardiac ultrasound examinations of patients with spontaneous circulation. After the fall of 2012, new members of the staff were trained according to the systematic educational program, if they had not previously completed training in focused cardiac ultrasound on a similar level. For this study, additional education in the form of a lecture and simulation based training in obtaining focused cardiac ultrasound images during ALS was conducted in 3-h sessions with groups of two to five physicians. Image acquisition When the resuscitation team was activated, the anaesthesiologist brought the ultrasound apparatus to the location of cardiac arrest. All examinations were performed using a portable ultrasound apparatus (Vivid i, GE Healthcare, Little Chalfont, UK) with an MS3 phased array transducer. The apparatus was pre-set to a
Based on reviews of electronic hospital patient records, a board-certified specialist in intensive care medicine determined presumed causes of cardiac arrest per the Hs and Ts mnemonic [3]. Other data extracted from the patient record included: age, weight, height, comorbidity, whether the patient achieved ROSC, and survival to discharge. Time to first ultrasound image was calculated as the difference between time of hospital resuscitation team activation and first saved ultrasound image. The duration of the resuscitation attempt was obtained from a national Danish in-hospital cardiac arrest database (DANARREST) [8]. Statistical methods Logistic regression was used to examine the association between the proportion of images useful for interpretation and the ALS phase in which images were obtained (rhythm analysis, bag-mask ventilations, or chest compressions) taking clustering by patient into account. The sequence in which images were obtained in each patient was included in the logistic regression model in the following categories: image 1–3, 4–6, or 7–10. Also included in the
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Table 1 Demography of patients from whom ultrasound images were obtained. Patients, N Female, N (%) Age, median (Q25%;Q75%) Body mass index, median (Q25%;Q75%) Comorbidities Hypertension, N (%) Diabetes mellitus, N (%) Chronic obstructive pulmonary disease, N (%) Atrial fibrillation/flutter, N (%) Ischemic heart disease, N (%) Chronic heart failure, N (%) Cancer, N (%) Presence of a pacemaker, N (%)
60 27 (45) 75 (65;80) 23.7 (20.3;27.7) 22 (37) 14 (23) 13 (22) 12 (20) 9 (15) 8 (13) 8 (13) 4 (7)
model was patient sex and body mass index (BMI) categorised as BMI < 30 and BMI ≥ 30. Cohen’s Kappa was used to calculate interobserver variability between the two echocardiography experts for each ultrasound characteristic and the overall inter-observer variability is reported as an average [9]. Continuous data are presented as medians with associated quartiles (Q25%;Q75%) or range. Categorical data are presented as number and percentages. Study data were managed using REDCap electronic data capture tools hosted at the Department of Clinical Medicine, Aarhus University, Denmark [10]. The analyses were performed using Stata/IC 13 (StataCorp LP, Collage Station, TX, USA). P < 0.05 was considered significant.
Fig. 1. Flow diagram. ALS – advanced life support; ROSC – return of spontaneous circulation.
2 min 46 s–50 min 12 s). Overall, 363 images were obtained, 102 during rhythm analysis, 103 during bag mask ventilations, and 160 during chest compressions.
Results
Images useful for interpretation in different ALS phases – echocardiography expert assessment
The cardiac arrest code was activated 193 times during the study period. At the time of the first rhythm analysis performed by the resuscitation team, 114 patients were in cardiac arrest. Images were obtained in 60 patients (Fig. 1). Patient demographics are shown in Table 1. Resuscitation attempts lasted for a median of 13 min (range: 1 min–60 min). Time from activation of the cardiac arrest code to the first images was obtained was median 10 min 3 s (range:
Table 2 shows the percentage of images useful for interpretation. Based on adjusted odds ratios, a higher proportion of the images obtained during rhythm analyses and bag-mask ventilations were useful for interpretation when compared with images obtained during chest compressions. There was no statistical difference in the proportion of useful images between rhythm analysis and bag-mask ventilations. (Table 3).
Table 2 Percentage of images in which the quality allowed determination of whether the right ventricle was larger than the left, pericardial fluid was present, and collapsing ventricles were present. Ultrasound characteristic
Resuscitation phase Rhythm analysis (N = 102)
Bag-mask ventilation (N = 103)
Chest compression (N = 160)
Assessed by echocardiography experts All three characteristics (N) Right ventricle larger than left (N) Pericardial fluid (N) Collapsed ventricles (N)
67% (68) 67% (68) 80% (82) 79% (81)
64% (66) 65% (67) 72% (74) 70% (72)
47% (75) 51% (81) 56% (89) 58% (92)
Assessed by anaesthesiologists All three characteristics (N) Right ventricle larger than left (N) Pericardial fluid (N) Collapsed ventricles (N)
50% (51) 53% (54) 64% (65) 55% (56)
43% (44) 47% (48) 50% (52) 45% (46)
28% (45) 30% (48) 38% (61) 31% (50)
Table 3 Images useful for interpretation. Comparison of each ALS phase based on assessment by echocardiography experts and anaesthesiologists. Crude OR (95%CI)
Crude P-value
Adjusted OR (95%CI)a
Adjusted P-valuea
Assessed by echocardiography experts Rhythm analysis vs chest compressions Ventilations vs chest compressions Rhythm analysis vs ventilations
2.3 (1.3–3.9) 2.0 (1.1–3.6) 1.1 (0.6–2.0)
0.003 0.02 0.69
2.2 (1.3–3.8) 2.0 (1.1–3.7) 1.1 (0.6–2.0)
0.005 0.03 0.74
Assessed by senior anaesthesiologists Rhythm analysis vs chest compressions Ventilations vs chest compressions Rhythm analysis vs ventilations
2.6 (1.5–4.3) 1.9 (1.1–3.4) 1.3 (0.8–2.3)
<0.001 0.03 0.27
2.6 (1.6–4.5) 1.8 (1.0–3.3) 1.5 (0.9–2.5)
<0.001 0.06 0.15
OR – odds ratio a Logistic regression model including the sequence of image acquisition, patient BMI and sex.
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4 Table 4 Focused cardiac ultrasound findings in 60 patients.
Right ventricle larger than left, N (%) Pericardial fluid, N (%) Wider than 1 cm, N (%) Collapsed ventricles, N (%)
Discussion
At least one useful image
Ultrasound characteristic present
46 (77)
9 (15)
51 (85)
15 (25) 8 (13) 0 (0)
50 (83)
Table 5 Primary cause of cardiac arrest. N = 60 patients. Hypoxia, N (%) Hypovolemia, N (%) Hyperkalaemia, N (%) Hypothermia, N (%) Thrombosis – coronary, N (%) Thrombosis – pulmonary, N (%) Tensions pneumothorax, N (%) Toxins, N (%) Tamponade, N (%) Unknown/not possible to determine, N (%)
28 (47) 10 (17) 2 (3) 0 (0) 7 (12) 7 (12) 0 (0) 1 (2) 3 (5) 2 (3)
For each patient, the proportion of images useful for interpretation was higher for images obtained as number 7–10 than for images obtained as number 4–6 (OR 2.2 (95%CI 1.2–4.1), P = 0.03) and 1–3 (OR 4.1 (95%CI 2.0–8.5), P < 0.001). On a patient level, at least one ultrasound image useful for interpretation was obtained during rhythm analysis in 42 (70%) patients, during bag-mask ventilations in 31 (52%) patients, and during chest compressions in 29 (48%) patients. Overall, at least one image useful for interpretation in any phase was obtained in 43 (72%) patients. Cohen’s kappa for inter-observer variability between the two echocardiography experts was 0.75 on average, 0.71 for images obtained during rhythm analysis, 0.77 for images obtained during bag-mask ventilations, and 0.68 for images obtained during chest compressions, indicating substantial agreement [9]. Images useful for interpretation in different ALS phases – anaesthesiologist assessment Based on adjusted odds ratios of the anaesthesiologist’s assessment, a higher proportion of the images obtained during rhythm analyses and bag-mask ventilations were useful for interpretation when compared with images obtained during chest compressions. There was no statistical difference in the proportion of useful images between rhythm analysis and bag-mask ventilations. (Table 3). On a patient level, at least one ultrasound image useful for interpretation was obtained during rhythm analysis in 33 (55%) patients, during bag-mask ventilations in 25 (42%) patients, and during chest compressions in 21 (35%) patients. Overall, at least one image useful for interpretation in any phase was obtained in 36 (60%) patients. Cardiac ultrasound findings by echocardiography experts Table 4 summarises the focused cardiac ultrasound findings as determined by the echocardiography experts on an individual patient level. Causes of cardiac arrest and resuscitation outcomes A presumed cause of cardiac arrest could post hoc be determined in 58 of 60 patients (Table 5). ROSC was achieved in 19 of 60 (32%) of patients, and five of 60 (8%) patients survived to hospital discharge.
In this study, we demonstrated that the quality of subcostal focused cardiac ultrasound obtained during ALS was higher when images were obtained during rhythm analysis and bag-mask ventilations, than during chest compressions. The quality of images useful for interpretation obtained during rhythm analysis was not statistically different from that of images obtained during bag-mask ventilations. The image quality increased as more images were obtained from the same patient. On a patient level, one or more images useful for interpretation was only obtained in 60% when assessed by the anaesthesiologists who obtained the images. Interestingly, no significant difference in the quality of images was found between images obtained during rhythm analysis and bag-mask ventilation. During standard ALS of a patient without an advanced airway, two ventilations are administered approximately four times for every rhythm analysis. Thus, image acquisition during ventilation provides multiple opportunities for image acquisition. The finding that the proportion of images useful for interpretation improves as more images are obtained from the same patient may further support attempts at image acquisition without waiting for rhythm analyses. Previous studies have reported that images of a quality sufficient for interpretation can be obtained in over 90% of patients during a rhythm analysis or a separate interruption in chest compressions that is extended for up to 10 s [4,5,11]. In the present study, an image useful for interpretation was only obtained in 72% of the patients when reviewed by echocardiography experts, and only in 60% when reviewed by the anaesthesiologists. There are several possible explanations for this discrepancy. First, in the present study, image quality was determined by expert off-line analysis. In the previously cited studies reporting a higher rate of images useful for interpretation, images were rated real time by the physician obtaining them with no off-line re-assessment [4,5,11]. A recent prehospital study, in which images were reviewed off-line, initial images were rated as satisfactory or better in only 68% of patients [12]. Second, the present study utilized a precise definition of image quality, i.e. an image was useful for interpretation if, it could be determined whether the right ventricle was larger than the left, there was pericardial fluid, and the ventricles were collapsing. Previous studies have not provided a specific definition of useful or adequate images [4,5,11]. Third, in the present study, focused cardiac ultrasound was only performed through the subcostal window. In previous studies, both the left parasternal and apical window was attempted if images of adequate quality could not be obtained through the subcostal window [4,5]. However, imaging through the parasternal or apical window during bag-mask ventilations may not be feasible because of the short pause in chest compressions. Transoesophageal imaging may provide better image quality than transthoracic during ALS. Use of this modality has been described [13,14]. However, data on image quality and safety are lacking. The overall percentage of images useful for interpretation was similar for images obtained during rhythm analysis (67%) and bag mask ventilations (64%), while it was lower for images obtained during chest compressions (47%). This distribution appeared to be different on a patient level. During rhythm analysis, at least one useful image was obtained in 70% of patients, while it was only 52% during bag mask ventilations and 48% during chest compressions. A possible explanation for this discrepancy is difficulties in timing image acquisition during bag mask ventilations. Also, even though images were obtained early, some patients may have been intubated thus preventing further image acquisition during bag mask ventilations. Our data support this explanation because no images were obtained during bag-mask ventilations in 13 patients, while this number was only four for both rhythm analysis and chest compressions. The percentage of patients in which an image useful for
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interpretation is of clinical importance because it suggests how often a clinician can expect to obtain a useful image in each phase, but importantly these numbers do not reveal how many attempts and thereby time would be needed in each phase. Based on assessment by both echocardiography experts and the anaesthesiologists, images obtained during rhythm analysis and bag-mask ventilations were of better quality than images obtained during chest compressions and there was no significant difference in the quality of images obtained during rhythm analysis and bag-mask ventilations. However, image quality was generally rated lower by the anaesthesiologists. This could reflect that the anaesthesiologists, who only had basic focused cardiac ultrasound training, were aware of their own limitation in interpreting images. However, it also questions the feasibility of focused cardiac ultrasound during cardiac arrest because images must be interpreted on-site if the information is to influence treatment. In 40% of patients no image useful for interpretation was obtained. Importantly, the anaesthesiologist in this study were informed that images would be subject to a later review by experts, which may have given them an incentive to be more critical. There is currently no data to support that the use of ultrasound during ALS improves outcomes [3]. Conversely, there is evidence that pauses in chest compressions affect outcomes negatively [15–17]. In line with this, guidelines state that ultrasound may only be considered as an additional diagnostic tool to identify potentially reversible causes of cardiac arrest if cardiac ultrasound can be performed without interfering with the ALS algorithm [3]. In the European Resuscitation Council guidelines it is stated that rhythm analysis and defibrillation can be reduced to less than 5 s once ALS has commenced [1]. Hence, extending rhythm analysis for up to 10 s or introducing interruptions in chest compressions for ultrasound is not in accordance with current resuscitation guidelines. It has recently been reported that the use of focused cardiac ultrasound during ALS almost doubles the pause in chest compressions during pulse checks [18,19]. To our knowledge, no studies involving transthoracic cardiac ultrasound have compared ultrasound findings with verified causes of arrest by autopsy. Consequently, the clinical applicability of different focused cardiac ultrasound findings is still unknown. It has been proposed that collapsing or flattened ventricles is a sign of hypovolemia during ALS [20]. In the present study, collapsing ventricles were not identified in any patients despite of hypovolaemia being the presumed cause of arrest in ten patients. Hyperdynamic or collapsing ventricles may be seen in severe hypovolaemia during spontaneous circulation, however decreased myocardial contractility with the onset of cardiac arrest may results in ventricular dilatation. Porcine data support this as the sonographic presentation of hypovolemic cardiac arrest is a dilated right ventricle and decreased left ventricular filling [21]. Pericardial fluid measuring over 1 cm was present in eight patients (13%). This surprising finding is of potential clinical importance because tamponade, a potentially treatable condition, may be the cause of arrest in this substantial number of patients.
Limitations The method used to rate image quality has not been validated, however we used well-defined criteria for determining usefulness for interpretation. The method is based on whether the presence of pathology can be determined. Thus, image assessment may be influenced by actual presence of pathology. However, this effect is likely to be evenly distributed among the different phases. The anaesthesiologists were instructed to save any image that was attempted. However, they may have been more prone to saving images of better quality. This possible selection bias could under-
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estimate differences between phases. The anaesthesiologists were not blinded to the different ALS phases. Also, the echocardiography experts could not be completely blinded as the performance of chest compressions was evident in the images. Conclusion The quality of focused cardiac ultrasound images obtained during rhythm analysis and bag-mask ventilations was superior to that of images obtained during chest compressions. However, there was no difference in the quality of images obtained during rhythm analysis and bag-mask ventilations. Thus, focused cardiac ultrasound during bag-mask ventilation may constitute an overlooked opportunity for image acquisition during ALS. Conflicts of interest Morten Thingemann Bøtker receives royalties for e-learning produced for USabcd A/S. Erik Sloth is co-owner of USabcd A/S. Acknowledgments We are in depth to the anaesthesiologists and intensive care nurses at Regional Hospital Randers. The study received generous funding from Falck Foundation, Laerdal Foundation, Randers Regional Hospital, and Central Denmark Region. The study sponsors had no role in designing the study; in collection, analysis, or interpretation of data; in the writing of the manuscript, or in the decision to submit the manuscript for publication. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at https://doi.org/10.1016/j.resuscitation.2017. 12.012. References [1]. Soar J, Nolan JP, Bottiger BW, et al. European resuscitation council guidelines for resuscitation 2015: section 3: adult advanced life support. Resuscitation 2015;95:100–47. [2]. Via G, Hussain A, Wells M, et al. International evidence-based recommendations for focused cardiac ultrasound. J Am Soc Echocardiogr 2014;27:683, e1–e33. [3]. Soar J, Callaway CW, Aibiki M, et al. Part 4: advanced life support: 2015 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations. Resuscitation 2015;95:e71–120. [4]. Hayhurst C, Lebus C, Atkinson PR, et al. An evaluation of echo in life support (ELS): is it feasible? What does it add. Emerg Med J 2011;28:119–21. [5]. Breitkreutz R, Price S, Steiger HV, et al. Focused echocardiographic evaluation in life support and peri-resuscitation of emergency patients: a prospective trial. Resuscitation 2010;81:1527–33. [6]. Ginghina C, Beladan CC, Iancu M, Calin A, Popescu BA. Respiratory maneuvers in echocardiography: a review of clinical applications. Cardiovasc Ultrasound 2009;7:42. [7]. Botker MT, Vang ML, Grofte T, Kirkegaard H, Frederiksen CA, Sloth E. Implementing point-of-care ultrasonography of the heart and lungs in an anesthesia department. Acta Anaesthesiol Scand 2017;61:156–65. [8]. Danish In-hospital Cardiac Arrest Database (DANARREST). [9]. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159–74. [10]. Harris PA, Taylor R, Thielke R, Payne J, Gonzalez N, Conde JG. Research electronic data capture (REDCap)–a metadata-driven methodology and workflow process for providing translational research informatics support. J Biomed Inform 2009;42:377–81. [11]. Flato UAP, Paiva EF, Carballo MT, Buehler AM, Marco R, Timerman A. Echocardiography for prognostication during the resuscitation of intensive care unit patients with non-shockable rhythm cardiac arrest. Resuscitation 2015;92:1–6. [12]. Reed MJ, Gibson L, Dewar A, Short S, Black P, Clegg GR. Introduction of paramedic led Echo in Life Support into the pre-hospital environment: the PUCA study. Resuscitation 2017;112:65–9. [13]. Blaivas M. Transesophageal echocardiography during cardiopulmonary arrest in the emergency department. Resuscitation 2008;78:135–40.
Please cite this article in press as: Aagaard R, et al. Timing of focused cardiac ultrasound during advanced life support – A prospective clinical study. Resuscitation (2017), https://doi.org/10.1016/j.resuscitation.2017.12.012
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ARTICLE IN PRESS R. Aagaard et al. / Resuscitation xxx (2017) xxx–xxx
[14]. van der Wouw PA, Koster RW, Delemarre BJ, de Vos R, Lampe-Schoenmaeckers AJ, Lie KI. Diagnostic accuracy of transesophageal echocardiography during cardiopulmonary resuscitation. J Am Coll Cardiol 1997;30:780–3. [15]. Cheskes S, Schmicker RH, Christenson J, et al. Perishock pause: an independent predictor of survival from out-of-hospital shockable cardiac arrest. Circulation 2011;124:58–66. [16]. Vaillancourt C, Everson-Stewart S, Christenson J, et al. The impact of increased chest compression fraction on return of spontaneous circulation for out-ofhospital cardiac arrest patients not in ventricular fibrillation. Resuscitation 2011;82:1501–7. [17]. Christenson J, Andrusiek D, Everson-Stewart S, et al. Chest compression fraction determines survival in patients with out-of-hospital ventricular fibrillation. Circulation 2009;120:1241–7.
[18]. Huis In‘t Veld MA, Allison MG, Bostick DS, et al. Ultrasound use during cardiopulmonary resuscitation is associated with delays in chest compressions. Resuscitation 2017;119:95–8. [19]. Clattenburg EJ, Wroe P, Brown S, et al. Point-of-care ultrasound use in patients with cardiac arrest is associated prolonged cardiopulmonary resuscitation pauses: a prospective cohort study. Resuscitation 2017;122:65–8, http://dx.doi. org/10.1016/j.resuscitation.2017.11.056. [20]. Hernandez C, Shuler K, Hannan H, Sonyika C, Likourezos A, Marshall JCAUSE. Cardiac arrest ultra-sound exam—a better approach to managing patients in primary non-arrhythmogenic cardiac arrest. Resuscitation 2008;76:198–206. [21]. Aagaard R, Granfeldt A, Botker MT, Mygind-Klausen T, Kirkegaard H, Lofgren B. The right ventricle is dilated during resuscitation from cardiac arrest caused by hypovolemia: a porcine ultrasound study. Crit Care Med 2017;45:e963–70.
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Timing of focused cardiac ultrasound during advanced life support – A prospective clinical study夽 Rasmus Aagaard a,b , Bo Løfgren a,c,∗ , Thorbjørn Grøfte b , Erik Sloth d , Roni R. Nielsen e , Christian A. Frederiksen e , Asger Granfeldt d , Morten T. Bøtker d,f a
Research Center for Emergency Medicine, Aarhus University Hospital, Noerrebrogade 44, Building 1B, 1st Floor, 8000 Aarhus C, Denmark Department of Anaesthesiology, Randers Regional Hospital, Skovlyvej 15, 8930 Randers NOE, Denmark c Department of Internal Medicine, Randers Regional Hospital, Skovlyvej 15, 8930 Randers NOE, Denmark d Department of Anaesthesiology and Intensive Care Medicine, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark e Department of Cardiology, Aarhus University Hospital,Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark f Research & Development, Prehospital Emergency Medical Services, Central Denmark Region, Olof Palmes Allé 34, 1st Floor, 8200 Aarhus N, Denmark b
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Article history: Received 5 September 2017 Received in revised form 24 November 2017 Accepted 10 December 2017 Keyword: Focused cardiac ultrasound In-hospital cardiac arrest Image quality
a b s t r a c t Introduction: Focused cardiac ultrasound can potentially identify reversible causes of cardiac arrest during advanced life support (ALS), but data on the timing of image acquisition are lacking. This study aimed to compare the quality of images obtained during rhythm analysis, bag-mask ventilations, and chest compressions. Methods: Adult patients in cardiac arrest were prospectively included during 23 months at a Danish community hospital. Physicians who had completed basic ultrasound training performed subcostal focused cardiac ultrasound during rhythm analysis, bag-mask ventilations, and chest compressions. Image quality was categorised as either useful for interpretation or not. Two echocardiography experts rated images useful for interpretation if all the following characteristics could be determined: 1) right ventricle larger than left ventricle, 2) pericardial fluid, and 3) collapsing ventricles. Results: Images were obtained from 60 of 114 patients undergoing ALS. A higher proportion of the images obtained during rhythm analysis and bag-mask ventilations were useful for interpretation when compared with chest compressions (rhythm analysis vs chest compressions: OR 2.2 (95%CI 1.3–3.8), P = 0.005; bag mask ventilations vs chest compressions: OR 2.0 (95%CI 1.1–3.7), P = 0.03). There was no difference between images obtained during rhythm analysis and bag-mask ventilations (OR 1.1 (95%CI 0.6–2.0), P = 0.74). Conclusion: The quality of focused cardiac ultrasound images obtained during rhythm analysis and bagmask ventilations was superior to that of images obtained during chest compressions. There was no difference in the quality of images obtained during rhythm analysis and bag-mask ventilations. Bag-mask ventilations may constitute an overlooked opportunity for image acquisition during ALS. © 2017 Published by Elsevier Ireland Ltd.
Introduction International resuscitation guidelines stipulate that focused cardiac ultrasound has potential to identify reversible causes of cardiac arrest during advanced life support (ALS) [1,2]. The International Liaison Committee on Resuscitation ALS Task Force state that there
夽 A Spanish translated version of the abstract of this article appears as Appendix in the final online version at https://doi.org/10.1016/j.resuscitation.2017.12.012. ∗ Corresponding author at: Department of Internal Medicine, Regional Hospital Randers, Skovlyvej 15, 8930 Randers NE, Denmark. E-mail address: [email protected] (B. Løfgren).
is inadequate evidence to evaluate whether cardiac ultrasound is of benefit during ALS and recommends that ultrasound should not interfere with the ALS algorithm [3]. This poses a challenge to ultrasound image acquisition. Previous studies have demonstrated that focused cardiac ultrasound can be obtained during either a rhythm analysis or a separate interruption in chest compressions, if both are extended for up to 10 s [4,5]. The quality of images obtained during other phases of the ALS algorithm, i.e. during bag-mask ventilations or chest compressions, has not been investigated. In patients with spontaneous circulation, a deep inspiration enhances image quality when the ultrasound transducer is in a subcostal position [6]. The same could apply during bag-mask ventilations in patients undergoing
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resuscitation, but there may not be sufficient time for transducer adjustment and positive pressure ventilation may compromise image quality by causing lung-shadowing. During chest compressions, there is ample time to adjust the ultrasound transducer, but movement of the thorax may compromise image quality. The aim of this study was to compare the quality of focused cardiac ultrasound images obtained during rhythm analysis, bagmask ventilations, and chest compressions. We hypothesised that the quality of images obtained during rhythm analysis is superior to that of images obtained during bagmask ventilations and chest compressions. Methods Study design and setting In this prospective, observational study, patients were included from February 16, 2015 to December 31, 2016 in a Danish community hospital (Regional Hospital Randers, Denmark, catchment area: ∼230,000 inhabitants, annual admissions: ∼36,500 patients). Acute and elective medical and surgical patients are treated at the hospital. Ethics The hospital resuscitation committee approved the study. The ethics committee of the Central Denmark Region regarded the study as a quality assurance project and waived approval and informed consent. The resuscitation team was informed that no intended action was to be interrupted, delayed, or omitted because of ultrasound image acquisition, especially not defibrillation and chest compressions. The physicians performing ultrasonography were instructed to convey any ultrasonography information that they believed should influence treatment of the patient to the resuscitation team. Participants Focused cardiac ultrasound was performed on consecutive patients (≥18 years) undergoing ALS, by physicians who were either anaesthesiology registrars in their final year of training or consultant anaesthesiologists, 24 h a day during the study period.
depth of 18 cm and recording of 5-s ultrasound loops. A commercial cart designed for the ultrasound apparatus was used (SafeLock Cart, GE Healthcare, Little Chalfont, UK). Subcostal ultrasound imaging was performed during rhythm analysis, bag-mask ventilations, and chest compressions, during the ALS algorithm [1]. The anaesthesiologists were instructed to save at least one loop during each of the three phases but could save up to 10 per patient. During focused cardiac ultrasound, a form was completed to mark the ALS phase in which each image was obtained. Focused cardiac ultrasound was not performed, if 1) resuscitation was terminated or return of spontaneous circulation (ROSC) was achieved before the arrival of the ultrasound apparatus, 2) the anaesthesiologist was involved in other tasks related to the resuscitation of the patient, or 3) the anaesthesiologist was occupied with other medical emergencies at the hospital. Study endpoints The primary study endpoint was the proportion of images useful for interpretation as assessed by twoechocardiography experts (CAF, RRN) certified by the Danish Society of Cardiology. An image was rated useful for interpretation if the experts assessed that the quality of the image was sufficient to determine the presence of all the following predefined ultrasound characteristics: 1) right ventricle larger than the left ventricle (yes/no), 2) pericardial fluid present (yes/no), and 3) collapsing ventricles present (yes/no). If one or more of these characteristics could not be determined, the image was rated not useful for interpretation. The echocardiography experts were blinded to both the patient and phase of acquisition and reviewed images in a randomised order using a computer equipped with EchoPACTM (GE Healthcare, Little Chalfont, UK). As a secondary endpoint, the senior anaesthesiologists evaluated images using the same method as the echocardiography experts. They used the screen of the ultrasound apparatus and were not blinded to the phase in which images were obtained. Other secondary endpoints were 1) the presence of ultrasound characteristics (right ventricle larger than left, pericardial fluid, collapsing ventricles) assessed by the experts, given sufficient image quality, 2) whether pericardial fluid was assessed by the experts to measure more than 1 cm from the epicardium to the parietal pericardium, 3) primary causes of cardiac arrest among the included patients.
Focused cardiac ultrasound education Other data collection The use of focused cardiac ultrasound in the Department of Anaesthesiology, Regional Hospital Randers was implemented by a previously described educational program in fall 2012 [7]. Briefly, the training consisted of a commercial available e-learning (usabcd. org, Aarhus, Denmark), a one-day hands-on course, and 10 supervised focused cardiac ultrasound examinations of patients with spontaneous circulation. After the fall of 2012, new members of the staff were trained according to the systematic educational program, if they had not previously completed training in focused cardiac ultrasound on a similar level. For this study, additional education in the form of a lecture and simulation based training in obtaining focused cardiac ultrasound images during ALS was conducted in 3-h sessions with groups of two to five physicians. Image acquisition When the resuscitation team was activated, the anaesthesiologist brought the ultrasound apparatus to the location of cardiac arrest. All examinations were performed using a portable ultrasound apparatus (Vivid i, GE Healthcare, Little Chalfont, UK) with an MS3 phased array transducer. The apparatus was pre-set to a
Based on reviews of electronic hospital patient records, a board-certified specialist in intensive care medicine determined presumed causes of cardiac arrest per the Hs and Ts mnemonic [3]. Other data extracted from the patient record included: age, weight, height, comorbidity, whether the patient achieved ROSC, and survival to discharge. Time to first ultrasound image was calculated as the difference between time of hospital resuscitation team activation and first saved ultrasound image. The duration of the resuscitation attempt was obtained from a national Danish in-hospital cardiac arrest database (DANARREST) [8]. Statistical methods Logistic regression was used to examine the association between the proportion of images useful for interpretation and the ALS phase in which images were obtained (rhythm analysis, bag-mask ventilations, or chest compressions) taking clustering by patient into account. The sequence in which images were obtained in each patient was included in the logistic regression model in the following categories: image 1–3, 4–6, or 7–10. Also included in the
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Table 1 Demography of patients from whom ultrasound images were obtained. Patients, N Female, N (%) Age, median (Q25%;Q75%) Body mass index, median (Q25%;Q75%) Comorbidities Hypertension, N (%) Diabetes mellitus, N (%) Chronic obstructive pulmonary disease, N (%) Atrial fibrillation/flutter, N (%) Ischemic heart disease, N (%) Chronic heart failure, N (%) Cancer, N (%) Presence of a pacemaker, N (%)
60 27 (45) 75 (65;80) 23.7 (20.3;27.7) 22 (37) 14 (23) 13 (22) 12 (20) 9 (15) 8 (13) 8 (13) 4 (7)
model was patient sex and body mass index (BMI) categorised as BMI < 30 and BMI ≥ 30. Cohen’s Kappa was used to calculate interobserver variability between the two echocardiography experts for each ultrasound characteristic and the overall inter-observer variability is reported as an average [9]. Continuous data are presented as medians with associated quartiles (Q25%;Q75%) or range. Categorical data are presented as number and percentages. Study data were managed using REDCap electronic data capture tools hosted at the Department of Clinical Medicine, Aarhus University, Denmark [10]. The analyses were performed using Stata/IC 13 (StataCorp LP, Collage Station, TX, USA). P < 0.05 was considered significant.
Fig. 1. Flow diagram. ALS – advanced life support; ROSC – return of spontaneous circulation.
2 min 46 s–50 min 12 s). Overall, 363 images were obtained, 102 during rhythm analysis, 103 during bag mask ventilations, and 160 during chest compressions.
Results
Images useful for interpretation in different ALS phases – echocardiography expert assessment
The cardiac arrest code was activated 193 times during the study period. At the time of the first rhythm analysis performed by the resuscitation team, 114 patients were in cardiac arrest. Images were obtained in 60 patients (Fig. 1). Patient demographics are shown in Table 1. Resuscitation attempts lasted for a median of 13 min (range: 1 min–60 min). Time from activation of the cardiac arrest code to the first images was obtained was median 10 min 3 s (range:
Table 2 shows the percentage of images useful for interpretation. Based on adjusted odds ratios, a higher proportion of the images obtained during rhythm analyses and bag-mask ventilations were useful for interpretation when compared with images obtained during chest compressions. There was no statistical difference in the proportion of useful images between rhythm analysis and bag-mask ventilations. (Table 3).
Table 2 Percentage of images in which the quality allowed determination of whether the right ventricle was larger than the left, pericardial fluid was present, and collapsing ventricles were present. Ultrasound characteristic
Resuscitation phase Rhythm analysis (N = 102)
Bag-mask ventilation (N = 103)
Chest compression (N = 160)
Assessed by echocardiography experts All three characteristics (N) Right ventricle larger than left (N) Pericardial fluid (N) Collapsed ventricles (N)
67% (68) 67% (68) 80% (82) 79% (81)
64% (66) 65% (67) 72% (74) 70% (72)
47% (75) 51% (81) 56% (89) 58% (92)
Assessed by anaesthesiologists All three characteristics (N) Right ventricle larger than left (N) Pericardial fluid (N) Collapsed ventricles (N)
50% (51) 53% (54) 64% (65) 55% (56)
43% (44) 47% (48) 50% (52) 45% (46)
28% (45) 30% (48) 38% (61) 31% (50)
Table 3 Images useful for interpretation. Comparison of each ALS phase based on assessment by echocardiography experts and anaesthesiologists. Crude OR (95%CI)
Crude P-value
Adjusted OR (95%CI)a
Adjusted P-valuea
Assessed by echocardiography experts Rhythm analysis vs chest compressions Ventilations vs chest compressions Rhythm analysis vs ventilations
2.3 (1.3–3.9) 2.0 (1.1–3.6) 1.1 (0.6–2.0)
0.003 0.02 0.69
2.2 (1.3–3.8) 2.0 (1.1–3.7) 1.1 (0.6–2.0)
0.005 0.03 0.74
Assessed by senior anaesthesiologists Rhythm analysis vs chest compressions Ventilations vs chest compressions Rhythm analysis vs ventilations
2.6 (1.5–4.3) 1.9 (1.1–3.4) 1.3 (0.8–2.3)
<0.001 0.03 0.27
2.6 (1.6–4.5) 1.8 (1.0–3.3) 1.5 (0.9–2.5)
<0.001 0.06 0.15
OR – odds ratio a Logistic regression model including the sequence of image acquisition, patient BMI and sex.
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4 Table 4 Focused cardiac ultrasound findings in 60 patients.
Right ventricle larger than left, N (%) Pericardial fluid, N (%) Wider than 1 cm, N (%) Collapsed ventricles, N (%)
Discussion
At least one useful image
Ultrasound characteristic present
46 (77)
9 (15)
51 (85)
15 (25) 8 (13) 0 (0)
50 (83)
Table 5 Primary cause of cardiac arrest. N = 60 patients. Hypoxia, N (%) Hypovolemia, N (%) Hyperkalaemia, N (%) Hypothermia, N (%) Thrombosis – coronary, N (%) Thrombosis – pulmonary, N (%) Tensions pneumothorax, N (%) Toxins, N (%) Tamponade, N (%) Unknown/not possible to determine, N (%)
28 (47) 10 (17) 2 (3) 0 (0) 7 (12) 7 (12) 0 (0) 1 (2) 3 (5) 2 (3)
For each patient, the proportion of images useful for interpretation was higher for images obtained as number 7–10 than for images obtained as number 4–6 (OR 2.2 (95%CI 1.2–4.1), P = 0.03) and 1–3 (OR 4.1 (95%CI 2.0–8.5), P < 0.001). On a patient level, at least one ultrasound image useful for interpretation was obtained during rhythm analysis in 42 (70%) patients, during bag-mask ventilations in 31 (52%) patients, and during chest compressions in 29 (48%) patients. Overall, at least one image useful for interpretation in any phase was obtained in 43 (72%) patients. Cohen’s kappa for inter-observer variability between the two echocardiography experts was 0.75 on average, 0.71 for images obtained during rhythm analysis, 0.77 for images obtained during bag-mask ventilations, and 0.68 for images obtained during chest compressions, indicating substantial agreement [9]. Images useful for interpretation in different ALS phases – anaesthesiologist assessment Based on adjusted odds ratios of the anaesthesiologist’s assessment, a higher proportion of the images obtained during rhythm analyses and bag-mask ventilations were useful for interpretation when compared with images obtained during chest compressions. There was no statistical difference in the proportion of useful images between rhythm analysis and bag-mask ventilations. (Table 3). On a patient level, at least one ultrasound image useful for interpretation was obtained during rhythm analysis in 33 (55%) patients, during bag-mask ventilations in 25 (42%) patients, and during chest compressions in 21 (35%) patients. Overall, at least one image useful for interpretation in any phase was obtained in 36 (60%) patients. Cardiac ultrasound findings by echocardiography experts Table 4 summarises the focused cardiac ultrasound findings as determined by the echocardiography experts on an individual patient level. Causes of cardiac arrest and resuscitation outcomes A presumed cause of cardiac arrest could post hoc be determined in 58 of 60 patients (Table 5). ROSC was achieved in 19 of 60 (32%) of patients, and five of 60 (8%) patients survived to hospital discharge.
In this study, we demonstrated that the quality of subcostal focused cardiac ultrasound obtained during ALS was higher when images were obtained during rhythm analysis and bag-mask ventilations, than during chest compressions. The quality of images useful for interpretation obtained during rhythm analysis was not statistically different from that of images obtained during bag-mask ventilations. The image quality increased as more images were obtained from the same patient. On a patient level, one or more images useful for interpretation was only obtained in 60% when assessed by the anaesthesiologists who obtained the images. Interestingly, no significant difference in the quality of images was found between images obtained during rhythm analysis and bag-mask ventilation. During standard ALS of a patient without an advanced airway, two ventilations are administered approximately four times for every rhythm analysis. Thus, image acquisition during ventilation provides multiple opportunities for image acquisition. The finding that the proportion of images useful for interpretation improves as more images are obtained from the same patient may further support attempts at image acquisition without waiting for rhythm analyses. Previous studies have reported that images of a quality sufficient for interpretation can be obtained in over 90% of patients during a rhythm analysis or a separate interruption in chest compressions that is extended for up to 10 s [4,5,11]. In the present study, an image useful for interpretation was only obtained in 72% of the patients when reviewed by echocardiography experts, and only in 60% when reviewed by the anaesthesiologists. There are several possible explanations for this discrepancy. First, in the present study, image quality was determined by expert off-line analysis. In the previously cited studies reporting a higher rate of images useful for interpretation, images were rated real time by the physician obtaining them with no off-line re-assessment [4,5,11]. A recent prehospital study, in which images were reviewed off-line, initial images were rated as satisfactory or better in only 68% of patients [12]. Second, the present study utilized a precise definition of image quality, i.e. an image was useful for interpretation if, it could be determined whether the right ventricle was larger than the left, there was pericardial fluid, and the ventricles were collapsing. Previous studies have not provided a specific definition of useful or adequate images [4,5,11]. Third, in the present study, focused cardiac ultrasound was only performed through the subcostal window. In previous studies, both the left parasternal and apical window was attempted if images of adequate quality could not be obtained through the subcostal window [4,5]. However, imaging through the parasternal or apical window during bag-mask ventilations may not be feasible because of the short pause in chest compressions. Transoesophageal imaging may provide better image quality than transthoracic during ALS. Use of this modality has been described [13,14]. However, data on image quality and safety are lacking. The overall percentage of images useful for interpretation was similar for images obtained during rhythm analysis (67%) and bag mask ventilations (64%), while it was lower for images obtained during chest compressions (47%). This distribution appeared to be different on a patient level. During rhythm analysis, at least one useful image was obtained in 70% of patients, while it was only 52% during bag mask ventilations and 48% during chest compressions. A possible explanation for this discrepancy is difficulties in timing image acquisition during bag mask ventilations. Also, even though images were obtained early, some patients may have been intubated thus preventing further image acquisition during bag mask ventilations. Our data support this explanation because no images were obtained during bag-mask ventilations in 13 patients, while this number was only four for both rhythm analysis and chest compressions. The percentage of patients in which an image useful for
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interpretation is of clinical importance because it suggests how often a clinician can expect to obtain a useful image in each phase, but importantly these numbers do not reveal how many attempts and thereby time would be needed in each phase. Based on assessment by both echocardiography experts and the anaesthesiologists, images obtained during rhythm analysis and bag-mask ventilations were of better quality than images obtained during chest compressions and there was no significant difference in the quality of images obtained during rhythm analysis and bag-mask ventilations. However, image quality was generally rated lower by the anaesthesiologists. This could reflect that the anaesthesiologists, who only had basic focused cardiac ultrasound training, were aware of their own limitation in interpreting images. However, it also questions the feasibility of focused cardiac ultrasound during cardiac arrest because images must be interpreted on-site if the information is to influence treatment. In 40% of patients no image useful for interpretation was obtained. Importantly, the anaesthesiologist in this study were informed that images would be subject to a later review by experts, which may have given them an incentive to be more critical. There is currently no data to support that the use of ultrasound during ALS improves outcomes [3]. Conversely, there is evidence that pauses in chest compressions affect outcomes negatively [15–17]. In line with this, guidelines state that ultrasound may only be considered as an additional diagnostic tool to identify potentially reversible causes of cardiac arrest if cardiac ultrasound can be performed without interfering with the ALS algorithm [3]. In the European Resuscitation Council guidelines it is stated that rhythm analysis and defibrillation can be reduced to less than 5 s once ALS has commenced [1]. Hence, extending rhythm analysis for up to 10 s or introducing interruptions in chest compressions for ultrasound is not in accordance with current resuscitation guidelines. It has recently been reported that the use of focused cardiac ultrasound during ALS almost doubles the pause in chest compressions during pulse checks [18,19]. To our knowledge, no studies involving transthoracic cardiac ultrasound have compared ultrasound findings with verified causes of arrest by autopsy. Consequently, the clinical applicability of different focused cardiac ultrasound findings is still unknown. It has been proposed that collapsing or flattened ventricles is a sign of hypovolemia during ALS [20]. In the present study, collapsing ventricles were not identified in any patients despite of hypovolaemia being the presumed cause of arrest in ten patients. Hyperdynamic or collapsing ventricles may be seen in severe hypovolaemia during spontaneous circulation, however decreased myocardial contractility with the onset of cardiac arrest may results in ventricular dilatation. Porcine data support this as the sonographic presentation of hypovolemic cardiac arrest is a dilated right ventricle and decreased left ventricular filling [21]. Pericardial fluid measuring over 1 cm was present in eight patients (13%). This surprising finding is of potential clinical importance because tamponade, a potentially treatable condition, may be the cause of arrest in this substantial number of patients.
Limitations The method used to rate image quality has not been validated, however we used well-defined criteria for determining usefulness for interpretation. The method is based on whether the presence of pathology can be determined. Thus, image assessment may be influenced by actual presence of pathology. However, this effect is likely to be evenly distributed among the different phases. The anaesthesiologists were instructed to save any image that was attempted. However, they may have been more prone to saving images of better quality. This possible selection bias could under-
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estimate differences between phases. The anaesthesiologists were not blinded to the different ALS phases. Also, the echocardiography experts could not be completely blinded as the performance of chest compressions was evident in the images. Conclusion The quality of focused cardiac ultrasound images obtained during rhythm analysis and bag-mask ventilations was superior to that of images obtained during chest compressions. However, there was no difference in the quality of images obtained during rhythm analysis and bag-mask ventilations. Thus, focused cardiac ultrasound during bag-mask ventilation may constitute an overlooked opportunity for image acquisition during ALS. Conflicts of interest Morten Thingemann Bøtker receives royalties for e-learning produced for USabcd A/S. Erik Sloth is co-owner of USabcd A/S. Acknowledgments We are in depth to the anaesthesiologists and intensive care nurses at Regional Hospital Randers. The study received generous funding from Falck Foundation, Laerdal Foundation, Randers Regional Hospital, and Central Denmark Region. The study sponsors had no role in designing the study; in collection, analysis, or interpretation of data; in the writing of the manuscript, or in the decision to submit the manuscript for publication. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at https://doi.org/10.1016/j.resuscitation.2017. 12.012. References [1]. Soar J, Nolan JP, Bottiger BW, et al. European resuscitation council guidelines for resuscitation 2015: section 3: adult advanced life support. Resuscitation 2015;95:100–47. [2]. Via G, Hussain A, Wells M, et al. International evidence-based recommendations for focused cardiac ultrasound. J Am Soc Echocardiogr 2014;27:683, e1–e33. [3]. Soar J, Callaway CW, Aibiki M, et al. Part 4: advanced life support: 2015 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations. Resuscitation 2015;95:e71–120. [4]. Hayhurst C, Lebus C, Atkinson PR, et al. An evaluation of echo in life support (ELS): is it feasible? What does it add. Emerg Med J 2011;28:119–21. [5]. Breitkreutz R, Price S, Steiger HV, et al. Focused echocardiographic evaluation in life support and peri-resuscitation of emergency patients: a prospective trial. Resuscitation 2010;81:1527–33. [6]. Ginghina C, Beladan CC, Iancu M, Calin A, Popescu BA. Respiratory maneuvers in echocardiography: a review of clinical applications. Cardiovasc Ultrasound 2009;7:42. [7]. Botker MT, Vang ML, Grofte T, Kirkegaard H, Frederiksen CA, Sloth E. Implementing point-of-care ultrasonography of the heart and lungs in an anesthesia department. Acta Anaesthesiol Scand 2017;61:156–65. [8]. Danish In-hospital Cardiac Arrest Database (DANARREST). [9]. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159–74. [10]. Harris PA, Taylor R, Thielke R, Payne J, Gonzalez N, Conde JG. Research electronic data capture (REDCap)–a metadata-driven methodology and workflow process for providing translational research informatics support. J Biomed Inform 2009;42:377–81. [11]. Flato UAP, Paiva EF, Carballo MT, Buehler AM, Marco R, Timerman A. Echocardiography for prognostication during the resuscitation of intensive care unit patients with non-shockable rhythm cardiac arrest. Resuscitation 2015;92:1–6. [12]. Reed MJ, Gibson L, Dewar A, Short S, Black P, Clegg GR. Introduction of paramedic led Echo in Life Support into the pre-hospital environment: the PUCA study. Resuscitation 2017;112:65–9. [13]. Blaivas M. Transesophageal echocardiography during cardiopulmonary arrest in the emergency department. Resuscitation 2008;78:135–40.
Please cite this article in press as: Aagaard R, et al. Timing of focused cardiac ultrasound during advanced life support – A prospective clinical study. Resuscitation (2017), https://doi.org/10.1016/j.resuscitation.2017.12.012
G Model RESUS-7411; No. of Pages 6 6
ARTICLE IN PRESS R. Aagaard et al. / Resuscitation xxx (2017) xxx–xxx
[14]. van der Wouw PA, Koster RW, Delemarre BJ, de Vos R, Lampe-Schoenmaeckers AJ, Lie KI. Diagnostic accuracy of transesophageal echocardiography during cardiopulmonary resuscitation. J Am Coll Cardiol 1997;30:780–3. [15]. Cheskes S, Schmicker RH, Christenson J, et al. Perishock pause: an independent predictor of survival from out-of-hospital shockable cardiac arrest. Circulation 2011;124:58–66. [16]. Vaillancourt C, Everson-Stewart S, Christenson J, et al. The impact of increased chest compression fraction on return of spontaneous circulation for out-ofhospital cardiac arrest patients not in ventricular fibrillation. Resuscitation 2011;82:1501–7. [17]. Christenson J, Andrusiek D, Everson-Stewart S, et al. Chest compression fraction determines survival in patients with out-of-hospital ventricular fibrillation. Circulation 2009;120:1241–7.
[18]. Huis In‘t Veld MA, Allison MG, Bostick DS, et al. Ultrasound use during cardiopulmonary resuscitation is associated with delays in chest compressions. Resuscitation 2017;119:95–8. [19]. Clattenburg EJ, Wroe P, Brown S, et al. Point-of-care ultrasound use in patients with cardiac arrest is associated prolonged cardiopulmonary resuscitation pauses: a prospective cohort study. Resuscitation 2017;122:65–8, http://dx.doi. org/10.1016/j.resuscitation.2017.11.056. [20]. Hernandez C, Shuler K, Hannan H, Sonyika C, Likourezos A, Marshall JCAUSE. Cardiac arrest ultra-sound exam—a better approach to managing patients in primary non-arrhythmogenic cardiac arrest. Resuscitation 2008;76:198–206. [21]. Aagaard R, Granfeldt A, Botker MT, Mygind-Klausen T, Kirkegaard H, Lofgren B. The right ventricle is dilated during resuscitation from cardiac arrest caused by hypovolemia: a porcine ultrasound study. Crit Care Med 2017;45:e963–70.
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