The Value Of Echocardiography During Cardiopulmonary Resuscitation

Anthony S. McLean, FRACP, MRACMA

Nepean Hospital, Pen&h, New South Wales, Australia

Objective: To assess the contribution of echocardiography performed during cardiopulmonary resuscitation in the critically ill subject. Method: A retrospective review of all patients undergoing CPR and having an echocardiogram (transthoracic or transoesophageal) during resuscitation in a general intensive care unit at a medium-sized tertiary referral hospital was undertaken. Results: Eleven such patients were identified over a 48-month study period. In 4 patients, major changes were initiated as a result of the echocardiographic findings with 2 long-term survivors (14%). In another 5 patients the decision not to continue resuscitation was assisted by the findings. Conclusion: Echocardiography performed during CPR assists greatly in decision-making and can contribute significantly to survival. (Asia Pacific Heart J 1999;8(2):106-109)

Introduction

Imaging of the heart during CPR may be helpful but the application of suitable techniques is logistically difficult in the acute situation. Although echocardiography lends itself to rapid application, the modality is usually only available in select areas such as a post-cardiac surgical ward. Described is the use of echocardiography during CPR in a general intensive care unit (KU), in an institution where cardiac surgery is not performed, but where echocardiography is readily available and widely utilised.

Method

The total patient admissions to the ICU, and total number of echocardiographic studies performed in the ICU during the study period between May 1993 and May 1997, were reviewed. A retrospective study of echocardiographic findings and subsequent management changes during CPR on patients in the ICU of a medium- sized tertiary referral hospital was undertaken. These included both transthoracic and transoesophageal studies. The management changes taken as a result of the echocardiographic findings were examined and related to patient outcome.

Results

During the 48-month study period there were a total of 3,158 admissions to the ICU, and 17% of patients in the unit had an echocardiogram performed at some time during their stay. Seven males and 4 females, ages ranging from 23 to 81 years, were identified as having had an echocardiogram performed during CPR. These 11 patients represented a small fraction of those undergoing CPR in the ICU. Eight transthoracic (TTE) and 3 transoesophageal (TEE) studies were performed. A TTE was chosen when it was considered that adequate views

of the underlying pathology could be obtained. TEE was directed towards those in whom adequate images could not be obtained by TTE.

In 4 patients the finding of severely impaired left ventricular contraction in the presence of an electrical rhythm was identified, this finding confirming a hopeless outcome. The left ventricle was hypercontractile in another subject, a 42-year-old woman who suddenly developed an impalpable pulse and unrecordable blood pressure. She had recently deliberately ingested a large number of medications, which included a variety of antihypertensive vasodilators. The echocardiographic finding supported the emphasis on management being directed towards increasing systemic vascular resistance. In 3 subjects the diagnosis of a massive pulmonary embolus was entertained as a result of echocardiographic findings, and thrombolytic and/or heparin therapy urgently administered.

In 1 of the 3 patients, a definite embolus was visualised in the right pulmonary artery (Fig.l), and a highly probable diagnosis of pulmonary embolus on the basis of right heart abnormalities was made in the other 2 patients. The patient in whom a definite embolus was identified had a history of chronic pulmonary hypertension and marked elevation of pulmonary artery pressures as measured by pulmonary artery catheter. The definite diagnosis of a massive pulmonary embolus in the acute situation was only possible with echocardiography. The finding of markedly impaired left ventricular contraction in a subject with moderately severe mixed mitral valve disease precluded urgent cardiac surgery.

Another subject, a 65-year-old woman, transferred from another hospital, suffered a cardiac arrest at the time of admission to the ICU. CPR was instituted and a TEE was performed which revealed the presence of a

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Fig. 1. Large embolus located in the right pulmonary artery.

type I (De Bakey) thoracic aorta dissection. The prognosis was concluded as hopeless. The last subject, a 23-year-old primigravida, was admitted with upper airways obstruction secondary to an oropharyngeal infection. Having developed signs of Lemierre’s syndrome, she delivered prematurely on day 3, and was gradually improving on therapy when she suddenly deteriorated on day 16. She went into asystole and was unable to be resuscitated with CPR. Urgent echocardiography revealed an unexpected pericardial tamponade (Fig. 2), which was treated with paracentesis during the CPR.1 She survived, albeit with a short-term memory deficit.

Of the 11 patients, there were 3 long-term survivors, 2 as a result of major management changes initiated by echocardiographic findings. These included the urgent drainage of the pericardial tamponade in the 23-year-old with Lemierre’s syndrome, and the administration of streptokinase to a woman in whom a massive pulmonary embolus was identified. The management of the third long-term survivor, suffering an overdose of vasoactive drugs, was assisted by the knowledge that myocardial contractility was normal.

In another 2 patients the echocardiographic finding initiated major management changes resulting in a short- term benefit for 3 and 2 days respectively. The first of these patients had a sudden cardiorespiratory arrest in the postoperative period following laparotomy for a subphrenic abscess. Because of the echocardiographic

findings consistent with a massive pulmonary embolus, high dose heparin therapy was initiated. The patient survived an asystolic arrest only to succumb 24 hours later. The second patient, following excision of a fungating rectal tumour, also had the diagnosis of a pulmonary embolus made during CPR, resulting in the administration of 750,000 units of streptokinase with subsequent rapid improvement of her condition. A further 3 days resuscitation followed before therapy was withdrawn. In 5 of the 8 non-survivors the decision not to continue resuscitation efforts was assisted by echocardiographic findings. These 5 patients had a variety of diagnoses, usually multiple, in which the primary cardiac pathology was uncertain.

These diagnoses included non-Hodgkin’s lymphoma (diagnosed at post mortem), moderate mitral stenosis and severe left ventricular dysfunction, postoperative aortic aneurysm repair with a renal vein haemorrhage, resuscitated out-of-hospital cardiac arrest with a suspected pericardial tamponade, and a patient with good left ventricular function and a large type 1 thoracic aorta dissection.

Discussion

The application of ultrasound in the ICU is well established.2 In particular, the use of echocardiography, both TTE and TEE, has been evaluated and recognised as a valuable tool in the assessment of cardiac function in the critically i11.“X4,5 However the use of echocardiography

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Fig. 2. Cardiac tamponade identified during CPR RV, right ventricle; RA, right atrium.

during CPR is not well documented as randomised control trials are not possible in the setting of a cardio- respiratory arrest and the unexpected occurrence make the logistics of applying the technique difficult. Van der Wouw and colleagues recently described the diagnostic accuracy of TEE in 48 patients undergoing CPR. In 27 of 31 patients undergoing postmortem, the TEE diagnosis was proved correct and in 31% of patients major therapeutic decisions were based on TEE findings.6 In the 11 subjects documented in the present study, the decision to perform a TTE or a TEE was made by the attending intensivist. TTE is rapidly obtained, within minutes, and is therefore the modality of choice unless adequate images are not possible. The application of TEE, at best, takes a minimum of 5 to 15 minutes even with an on-site laboratory. Images sufficiently adequate to make a diagnosis were obtained in all 11 subjects.

The identification of 11 patients in whom it was considered by the attending intensivist that an echocardiogram might be useful in the setting described, appears at first to be a small number. Two factors have to be considered in regard to this. The first is that the majority of the haemodynamically unstable patients would have been likely to have already undergone echocardiography to assess cardiac function, in addition to having pulmonary artery catheters in situ. Therefore the relevant information was available in many cases, and treatment adjusted accordingly, or the situation

Abbreviations: LV, left ventricle; LA, left atrium;

preempted as being hopeless should the patient suffer a cardiorespiratory arrest. The second factor is the availability of echocardiography which requires setup time and an experienced operator to assess the cardiac status under difficult conditions. Even if a machine is housed in the ICU complex, there is a time lag between calling for it, attaching to an electrical supply and rapidly warming it up. This challenge is more evident during certain times, such as the early hours of the morning, when staff less experienced with the modality are the only personnel immediately available. Obtaining adequate images on a supine ventilated patient who is undergoing chest compression requires an experienced operator. These limitations suggest that there are likely to be more patients in whom urgent echocardiography during CPR may have been useful.

Although other tools are usually available to assess cardiac function, namely ECG, chest X-ray examination, and pulmonary artery catheter, often pertinent information can only be obtained by echocardiography, as demonstrated by a patient with a totally unexpected pericardial tamponade, and the patient with known pulmonary hypertension, and a large pulmonary embolus. The latter patient was considered to have a very poor prognosis as a result of the relentless pulmonary hypertension. However, following successful resuscitation with thrombolytic therapy, a decision that would not have been taken without evidence of

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pulmonary embolus, she subsequently went on long-term oral anticoagulation therapy and is alive and in much better health many years later.

Whether a diagnostic technique is useful or not is usually judged on the identification of definite pathology. In the critical care setting the absence of correctable pathology on echocardiography can be very useful, such as determining that further resuscitation is hopeless, or that transfer to another location for urgent surgery is not warranted.

Access to echocardiography, either as a readily available routine tool, or as described in the urgent situation, is becoming increasingly important in the critical care setting. Although the modality has usually been available in select settings such as the cardiac surgical operating theatre, post operative cardiac surgical ward or the coronary care unit, these are situations when the underlying pathology is often well defined and complications predictable.

It is in the critical care setting where the variety of pathology is much broader, the precise nature of the patient’s acute deterioration is less predictable, and multiple organ dysfunction is often present, that urgent need for appraisal of the cardiac status exemplifies the value of echocardiography. The 11 patients presented in

this series are likely to under-represent those who may have benefitted from urgent echocardiographic assessment because of the logistical challenges, but at least 2 lives (14%) that would otherwise have been lost were saved, proving the value of the technique in selected patients undergoing CPR.

Conclusion

Echocardiography performed during CPR often assists in patient management and can contribute directly to improved survival.

References 1.

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McLean ASTyler K. Cardiac Tamponade in a Postpartum Woman with Lemierre’s Syndrome. Anaesth Intens Care 1998;26:582-3. Lichtenstein D, Axler 0. Intensive use of general ultrasound in the intensive care unit. Intens Care Med. 1993;19:353-5. Stoddard MF, Prince CR, Ammash N, et al. Pulsed Doppler tran- socsophageal echocardiographic determination of cardiac output in human beings: Comparison with thermodilution technique. Am Heart J. 1993;126:956-61. McLean AS. Echocardiographic assessment of left ventricular function in the critically ill. Anaesth Intens Care 1996;24:60-5. Chenzbraun A, Pinto FJ, Schnitter I. Transoesophageal echocardio- graphy in the intensive care unit: impact on diagnosis and decision making. Clin Cardiol. 1994;17(8):438-44. Van der WouwPA, Koster RW et al. Diagnostic accuracy of trar- soesophageal echocardiography during cardiopulmonary resuscitation. JACC 1997;30(3):780-3.

Baker Medical Research Institute Annual Symposium Cardiovascular Genetics

11-12 Februarv 2000 I For further information and registration, please contact: a

Novotel Bayside Melbourne MS Susan Smith, Baker Medical Research Institute Telephone: 61 3 9522 4314 Facsimile: 61 3 9510 4368

The Esplanade, St Kilda, Victoria, Australia e-mail: sue.smith@baker.edu.au

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