AUTHOR: Dr Michael Blaivas, MD, MBA
Department of Emergency Medicine, St. Francis Hospital, Columbus, Georgia, USA
ABSTRACT
Objectives: Define the frequency of agreement between focused bedside
echocardiography (Echo) and pulse checks during cardiopulmonary resuscitation (CPR).
Methods: This was a retrospective review of multi-year quality assurance logs on cardiac
arrest patients evaluated with point-of-care Echo during CPR, over a seven year period.
All patients in cardiopulmonary arrest that presented when physicians trained in Echo
were availabile and had quality assurance documentation completed, were eligible for
enrollment. Patients for whom incomplete data was present in the logs were excluded
from the study. This study took place at a busy emergency medicine department with a
large cardiac population and an approximate annual census of 80,000 visits per year.
Emergency physicians (EPs), with hospital credentialing in point-of-care Echo, routinely
used ultrasound as part of their standard management of CPR patients. During all pulse
checks, nurses and physicians attempted to locate pulses while one EP performed a brief
Echo of the heart with a compact ultrasound machine. Echo checks were limited to the
time available during pulse checks and ended when the treating EP ordered resumption of
chest compressions. Myocardial function was graded into normal ejection fraction (EF),
mildly, moderately, severely depressed, negligible function and asystole as previously
defined in the literature. If Echo suggested sufficient EF to generate blood flow but pulse
check was negative, the carotid arteries were evaluated with Doppler when interference
with resuscitative efforts could be avoided. Statistical analysis included descriptive
statistics and Cohen Kappa coefficient for agreement analysis.
Results: A total of 693 pulse checks occurred concomitantly with Echo checks in 226
patients. Of the 226 patients, 59 (26.1%) had resumption of spontaneous circulation at some point in their resuscitation based on pulse palpation and electrocardiographic
monitor tracing. A total of 178 (25.7%) Echo checks revealed an EF felt to likely
generate a detectable blood pressure. In 47% (84) of those Echo checks, no pulses were
palpable. Conversely, in 31 (6%) pulse checks (when electrical cardiac activity was noted
on the monitor) and a healthcare provider felt palpable pulses, the echo showed either
myocardial standstill or negligible EF. Echo results and pulse palpation during pulse
checks showed poor correlation with a Kappa of 0.52.
Conclusions: In this study, Echo findings and pulse palpation results periodically
disagreed when myocardial activity was present. When Doppler analysis of carotid flow
was possible in patients with adequate EF but no pulses, flow was always noted. Very
concerning, in 6% of patients apparent palpable pulses occurred when Echo showed no
myocardial contraction or negligible EF
INTRODUCTION Evaluation and treatment of patients in cardiopulmonary arrest has progressed significantly in the last four decades with the advent of cardiac resuscitation protocols, endotracheal intubation, central line placement and electric cardioversion. 1-4 However, clinicians managing cardiopulmonary resuscitations are typically doing so blindly. While electrocardiographic monitoring provides a glimpse of the electrical activity of the heart, it tells the clinician little about actual myocardial function. 5 Thus, pulse checks are critical and help determine if spontaneous circulation has resumed. In addition pulse checks will typically decide whether chest compressions continue or not and if resuscitation is terminated. Typically, invasive arterial blood pressure monitoring is not available in patients arriving to an emergency department or resuscitation area. Similarly, hospitalized patients that are not in an intensive care unit are unlikely to have any invasive monitoring in place. Since pneumatic blood measuring devices are inaccurate, slow to result and have difficulty picking up low blood pressures, physicians typically have to rely on manual pulse palpation during resuscitation. 6 However, there is growing evidence that our ability of accurately palpate a pulse is quite poor in these critically ill patients. 7,8 Some studies indicate that physicians may accurately palpate a pulse in as low as 50% of patients. 9 This likely results from the innate inaccuracy of pulse palpation, the tense environment of a cardiac arrest and also the trend toward obesity and morbid obesity in westernized countries. In addition, low blood pressure and low flow states which require vasopressor support, but not continued chest compressions, may be too difficult to detect by human hands in many cases. Many intensivists, emergency physicians, surgeons and other clinicians have found great utility in utilizing bedside echocardiography during cardiopulmonary arrest management. 10-12 This reflects the ability of ultrasound to identify treatable causes of arrest as well as aid in managing patient resuscitation. 13 Anecdotal experience, as well as previous published studies suggest that there may be a discordance between echocardiographic findings and electrocardiographic findings as well as detection of pulses. 14 This study sought to evaluate the frequency of apparent discordance between pulse detection by manual palpation and finding on echocardiography. METHODS Study Design This was a retrospective quality assurance log review using de-identified patient data of ultrasound findings during cardiac arrest pulse palpation breaks. The study was conducted at busy emergency department with a large high acuity cardiac population and annual census of approximately 80,000 patients. This study was IRB exempted due to its retrospective quality assurance nature and use of de-identified data. All patients arriving in, or experiencing cardiopulmonary arrest while in the emergency department, without an indwelling arterial pressure monitor, were eligible for enrollment if they had complete data in the quality assurance logs. As part of standard practice all cardiopulmonary resuscitations were managed with bedside emergency echocardiography, when hospital credentialed physicians were available. Patients with incomplete quality assurance log data were excluded from the study. Quality assurance logs were reviewed for cardiac arrest entries with completed EF estimate and corresponding pulse check results by an experienced point of care ultrasound program director. Arrest Echo Protocol Each patient in cardiopulmonary arrest was scanned by a study physician during pulse breaks. The treating physician was advised of echo finding as part of standard practice, but the study physician did not make treatment recommendations. Bedside ultrasound examinations were performed only during pulse checks, which were conducted by a nurse and treating physician or second nurse. In all cases, at least two healthcare providers assessed for pulses at the same time. All pulse checks were made either at carotid artery or femoral artery locations. All efforts at performing an echo were ceased when the pulse check was stopped by the treating physician. Echo checks continued during pulse checks for the duration of the resuscitation as long as they did not interfere with resuscitation efforts. Left ventricular function on echocardiography was graded into distinct categories: normal ejection fraction (EF), mildly (approximately 40 to 50%), moderately (approximately 20 to 40%), severely depressed (approximately 10 to 20%) and negligible function (EF below 10%) as previously defined in the literature. 15 If Echo suggested sufficient EF to generate blood flow but pulse check revealed no palpable pulses, the carotid arteries were evaluated with Doppler, color and pulse wave, when interference with resuscitative efforts could be avoided. All ultrasound examinations of the heart during pulse checks were videotaped using either SVHS video tape or DVD and stored for quality assurance review. In addition, ultrasound quality assurance logs were filled out with ultrasound findings and clinical outcome as part of standard practice. Emergency sonologists utilized phased array transducers with a range of 2.5 to 4 MHz using either as SonoSite 180 Plus, Titan, Micromaxx or M-Turbo compact ultrasound machines. Standard echocardiography windows were utilized to image the heart. The subxiphoid window was utilized preferentially in order to avoid interference with resuscitation, the parasternal long and apical four chamber views were used if no useful subxiphoid image was obtainable. Transesophageal echocardiography was used when available, either on a Sonosite Micromaxx or M-Turbo. Main Outcome Measures Physicians filled out standardized quality assurance logs. They recorded the results of the pulse checks by team members and the corresponding emergency echo findings. For secondary measures, if left ventricular ejection fraction was felt to be above 10% in the setting of absent pulses on palpation and the study physician was able to Doppler a carotid artery, presence of absence of flow was recorded. In addition, when pulse wave Doppler was used the peak systolic velocity was recorded. Sonologists also recorded when manual pulse palpation revealed a palpable pulse, but emergency echo showed either negligible that could not generate flow or complete absence of myocardial contraction. Statistical Methods Data were kept in an Access database (Microsoft Corporation, Seattle Washington). Prior to analysis, data were exported to an Excel spreadsheet and commercially available statistical software was used to perform analyses. Statistical analysis included descriptive statistics and agreement analysis using Cohen Kappa coefficient. RESULTS A total of 693 pulse checks occurred concomitantly with Echo checks in 226 patients. Of the 226 patients, 59 (26.1%) had resumption of spontaneous circulation at some point in their resuscitation based on pulse check and electrocardiographic monitor tracing. A total of 178 (25.7%) Echo checks revealed EF of severely depressed or better and were felt to likely generate a detectable blood pressure. In 47% (83.66) of these Echo checks, no pulses were palpable. Conversely, in 31 (6%) pulse checks on when electrical cardiac activity was noted on the monitor and a healthcare provider felt palpable pulses, the echo showed either myocardial standstill or negligible EF. Carotid Doppler was obtained in 37% of cases when Echo showed severely depressed or better EF but no pulses were palpable. In these cases, all patients showed flow in the carotid on both color and pulse wave Doppler. Echo results and pulse palpation during pulse checks showed poor correlation. Echo results and pulse checks showed poor agreement with a correlation coefficient of 0.52. Comparing only the 178 patients noted to have echo based findings of adequate cardiac output the Cohen Kappa decreased to 0.47. DISCUSSION Cardiopulmonary arrest has many etiologies, some of which are correctable through interventions such as pericardiocentesis and many that are not. However, identification of these correctable processes may be difficult simply based on physical examination and electrocardiographic evidence. The focus of many resuscitation efforts are patients with apparent electrical activity on a monitor, as they may hold out the highest hope for successful resuscitation. 16 Over the past two decades, the use of Point of Care Ultrasound to manage resuscitation has greatly improved the ability of clinicians to accurately identify correctable causes of cardiac arrest in a variety of settings. 17 Recent studies suggesting that focused ultrasound checks of the heart during CPR interfere with quality chest compression are likely to push more providers to relying on pulse palpation only. 18,19 However, prior data has repeatedly suggested pulse checks are unreliable for resuscitation management, leaving providers who chose not to use ultrasound blinded to cardiac function in many cases. Pulseless electrical activity (PEA) occurs when a patient appears to have electrical activity on a monitor, but no pulse can be palpated. Once thought to strictly indicate mechanical asystole in the presence of electrical activity, it is now clear that a portion of these patients have mechanical cardiac activity with blood pressures too low to result in a palpable pulse, in that specific individual. One study demonstrated that up to 41% of patients presenting with electrical activity but no pulse actually had mechanical contractions of the heart. 20 While survival rates for patients in PEA are poor, with one large study reporting 11% survival rate with only 62% of survivors having a good neurological outcome, this group of patients are typically thought to have a higher likelihood of survival than asystolic patients. 21 As the team managing the patient in cardiopulmonary arrest strives to resuscitate the patient they are also seeking reversible causes of cardiac arrest. In PEA patients these include tension pneumothorax, hypovolemia, toxins, hypoglycemia, hypoxemia, acidosis, hypokalemia, hyperkalemia, hypothermia, cardiac tamponade, cardiac ischemia, pulmonary embolism, and trauma. 22 Ultrasound can aid the resuscitation team by allowing visual assessment of cardiac function as well are a more accurate evaluation for some the treatable causes of PEA that are listed by both the AHA and European Council on Resuscitation. 23 Cardiac tamponade from pericardial effusion can be readily identified by focused emergency echo. 24 At the same time the provider can image the inferior vena cava to estimate intravascular fluid volume and even monitor change in volume during ongoing resuscitation. Cardiac contractility can be evaluated by emergency echo and may greatly aid in goal directed resuscitation. Pneumothorax has been proven to be very accurately ruled out and identified in multiple studies by point of care ultrasound. In cases of large pulmonary emboli, point of care ultrasound may detect intra-cardiac thrombosis, venous thrombosis or particular echo findings such as right heart strain on TAPSE and McConell sign, which may strongly point toward presence of PE. 25 In such cases, the resuscitation director may be more included to thrombolyse the patient given the evidence provided by ultrasound. When complete mechanical cardiac stand still is noted on echo despite several rounds of chest compressions and medications there is strong support that successful resuscitation is extremely unlikely. Terminating the resuscitative efforts earlier in such patients may save resources without compromising care. In most situations of cardiopulmonary resuscitation, the code is continued until further efforts are deemed futile and the resuscitation stopped or, in the minority, when resumption of spontaneous circulation is noted. Unless the patient has already been in the hospital or emergency department for some time and received an indwelling arterial blood pressure monitor, the only commonly accepted method of determining resumption of spontaneous circulation is palpating a pulse. While patients with no cardiac output receive chest compressions and epinephrine a hypotensive patient may be taken along a different pathway of resuscitation. Not only is the treatment of a hypotensive patient different from that of a patient in PEA, but CPR itself is not a benign intervention and may cause injury to the patient. Unnecessary trauma to a critically ill patient could further complicate recovery if the patient survives the resuscitation. Frequent findings in patients having undergone CPR include lesions of tracheal structures and bony chest fractures. Less frequently encountered are lesions of the pleura, pericardium, myocardium and other internal organs and vessels. 26 As this data indicates, disagreements between the ultrasound machine monitor screen and manual pulse palpation are surprisingly common. The concept of actually checking the carotid artery for blood flow on color and pulse wave Doppler came out of multiple situations when disagreement occurred between staff that insisted on resuming chest compressions and physicians who ordered them stopped because of adequate estimated ejection fraction on focused echo. Such patients are most likely to be treated with vasopressors and fluids in order to elevate their blood pressure, but may be difficult to manage if providers are blind to their cardiac function. Our data further supports that pulse palpation is inaccurate, in arrest situations, suggesting that providers may want to add focused echo for additional information. In 37% of patients physicians were able to access the carotid artery after the echo, which reflected an ejection fraction felt to be consistent with perfusion of the brain. In each case color Doppler confirmed the presence of spontaneous blood flow with measurement on pulse wave Doppler ranging from 60 to 105 cm/sec. Vascular ultrasound and neurology literature indicates that normal common carotid artery peak systolic flow velocities vary considerably, but tend to range from 55 to 100 cm/sec. 27 Mean values in normal patients from the internal carotid are typically 54 to 88 cm/sec, but some normal individuals can have peak systolic velocities up to 120 cm/sec. 28 Values increase considerably for carotid stenosis. Regardless, the typical flow velocity recorded in this study was quite near normal as previously defined. Multiple other factors affect carotid peak systolic velocities, such as potential stenosis in the vertebral arteries or the contralateral carotid. However, such fine details probably have little bearing in gauging if adequate circulation is produced by a beating heart, while no pulses are palpable. It is at this point that chest compressions may be terminated and pressors instituted or adjusted as in any critically ill, hypotensive patient. Exceedingly shocking was the fact that in 6% of cases a team member called out “I have a pulse” leading to cessation of chest compressions, when the heart was in mechanical standstill or had no viable contractile activity. We have noted anecdotally and repeatedly that such confusion causes delays measured in minutes that may even last until a pneumatic blood pressure cuff finally fails to obtain a blood pressure and another provider realizes no pulses are palpable. While additional evidence will need to be produced, it is more and more compelling that ultrasound should be present at the bedside of every patient undergoing cardiopulmonary resuscitation whenever possible. This can be achieved in the most unlikely settings. The introduction of highly compact devices has enabled clinicians outside of the intensive care units and emergency departments to use ultrasound for evaluation of cardiopulmonary arrest patients. Focused ultrasound utilization has been documented in the settings of pre-hospital ground and air ambulances as well as disaster scenes and even sporting events. Limitations of the study include no invasive monitoring to compare pulse palpation to actual arterial blood pressure. The study population was typical of diverse western body habitus distributions and may not reflect findings in other populations around the world where pulse palpation may be more or less accurate. The retrospective nature of the study is also an inherent limitation, although data was collected prospectively for quality assurance tracking. In summary, data from this study suggests that disagreement between focused echo and pulse palpation is a common occurrence. 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