ASRA Pain Medicine Update

Cite as: Bughrara N, Panzer O, Pustavoitau A. POCUS spotlight: point-of-care ultrasound in cardiopulmonary rescusitation. ASRA Pain Medicine News 2022;47. https://doi.org/10.52211/asra0250122.016  

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Introduction

In-hospital cardiac arrest (IHCA) occurs in more than 290,000 adults annually in the United States.¹ Non-shockable rhythms such as asystole and pulseless electrical activity (PEA) account for 81% of IHCA, with the most common causes being hypotension (50%-60%) and acute respiratory insufficiency (15%-40%).¹ The American Heart Association Advanced Cardiac Life Support (ACLS) algorithm is the standard of care in managing IHCA. This algorithm emphasizes the performance of high-quality cardiopulmonary resuscitation (CPR) with minimizing pulse/ rhythm checks to fewer than 10 seconds. The ACLS guidelines also suggest that point-of-care ultrasound (POCUS) can be used to identify cardiac motion and potential reversible causes of PEA arrest, when an experienced sonographer is present and POCUS would not interfere with CPR.^2,3

Detection of Cardiac Motion

Patients in PEA arrest who have coordinated electrical and myocardial activity visualized on POCUS (pseudo-PEA) have better prognosis compared to patients with no myocardial activity on POCUS (true PEA, or cardiac standstill) (Video 1). Recent meta-analysis demonstrated that spontaneous cardiac motion on ultrasound has a pooled sensitivity of 95% and specificity of 80% in predicting return of spontaneous circulation (ROSC).⁴ While ROSC is rare in patients with true PEA, ACLS guidelines recommend against using POCUS findings to terminate resuscitative efforts.⁵

Video 1. Subcostal 4-chamber view demonstrating cardiac standstill. RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle (click to view)

Potential Reversible Causes in Pseudo-PEA

Pericardial Tamponade

Pericardial tamponade is identified in 5%-22% of patient with PEA arrest.^6,7 POCUS findings of pericardial tamponade include the presence of either small (acutely developing) or large (chronically developing) pericardial effusion, right atrial (RA) systolic collapse, right ventricular (RV) diastolic collapse, and plethoric inferior vena cava (IVC) (Videos 2 and 3). The diagnosis of tamponade using POCUS may be difficult in post-cardiac surgery patients who frequently present with a localized collection; transesophageal echocardiography (TEE) should then be used to make the diagnosis. A concomitant pleural effusion might potentially worsen the tamponade physiology. Therefore, imaging of the pleural space can be performed during chest compressions, with thoracentesis possibly reversing the tamponade physiology⁸ (Video 4).

Video 2. Subcostal 4-chaber view demonstrating pericardial effusion. RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle (click to view)

Supplemental Video 3. Subcostal IVC view demonstrating plethoric inferior vena cava (IVC) during chest compressions. RA, right atrium.  (click to view)

Supplemental Video 4. Sonogram of the lateral inferior thorax demonstrating pleural effusion (click to view)

Pulmonary Embolism

Acute RV failure caused by pulmonary embolism (PE) is a common cause of cardiac arrest in up to 30% of patients with PEA arrest.⁹ Typical ultrasound findings include RV and RA dilatation on the four-chamber and septal flattening (so called D-sign) on the short-axis views. Also, RV systolic function is reduced in about half of the patients, as evidenced by a decreased tricuspid annular plane systolic excursion on the apical four-chamber view¹⁰ (Video 5). If color doppler is applied over the tricuspid valve, significant regurgitation is commonly found. While finding a thrombus in transit in the right heart chambers or within the pulmonary arteries is diagnostic of acute PE, it is rarely visualized and advanced imaging skills are required to locate thrombus.

Supplemental Video 5. Subcostal 4-chaber view demonstrating dilated and depressed right ventricular function. RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle (click to view)

The above findings (other than thrombus-in-transit) are not pathognomonic to PE as they are also seen during a pulmonary hypertensive crisis (PHTC). Chronic changes presenting as RV free-wall hypertrophy (thickness greater than 5 millimeters in diastole) and RA dilatation make a PHTC more likely, whereas a thin-walled RV free wall and a normal size RA point toward an acute process. Finally, chamber sizes should only be assessed in patients with preserved cardiac activity, as the RV can appear dilated in asystole independent of the etiology of cardiac arrest.¹¹ If PE is suspected, the lower extremity venous ultrasound can be performed to evaluate for deep venous thrombosis. Evidence of a thrombus warrants a careful risk/benefit analysis to initiate empiric anticoagulation or thrombolytic therapy.

Myocardial Infarction

Myocardial ischemia is the most common cause of cardiac arrest with shockable rhythm. Presence of acute left ventricular (LV) dysfunction should raise the suspicion for acute coronary thrombosis as the cause of non-shockable PEA arrest and asystole (Video 6). Echocardiographic assessment of regional wall motion should be performed immediately after ROSC to minimize time to coronary revascularization.

Supplemental Video 6. Subcostal 4-chaber view demonstrating dilated and depressed left ventricular function. RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle (click to view)

Severe Hypovolemia

Small hyperdynamic LV that obliterates during systole is seen in cardiac arrest due to hypovolemia (Video 7).¹² However, small collapsing LV size does not always correlate with intravascular volume status.¹¹ In patients with trauma, a small (less than 1 cm), collapsible IVC predicts hemorrhagic shock responsive to volume loading (Video 8).¹²

Supplemental Video 7. Demonstrating underfilled heart. RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle (click to view)

Supplemental Video 8. Demonstrating small and collapsible inferior vena cava. RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle (click to view)

Tension Pneumothorax

Ultrasound diagnosis of pneumothorax is made by the absence of lung sliding (not pathognomonic) and B-lines in the appropriate clinical setting. Use of lung ultrasound can reduce time to needle decompression.¹³ During CPR, ultrasound can be used to assess for iatrogenic tension pneumothorax.

POCUS Protocols during CPR

During CPR, the use of POCUS remains a subject of investigation due to safety concerns. Its use was associated with prolonged pauses during pulse checks, which may reduce chances to achieve ROSC. However, prolonged pauses depend on sonographer experience. For example, when an attending or fellowship-trained practitioner acquires images, CPR is interrupted for shorter periods.¹⁴

To shorten the duration of interruptions in CPR, protocolized approaches to use ultrasound were developed.^15-22 After the introduction of the protocols, the length of CPR interruptions uniformly decreases, although often not to below 10 seconds. With no evidence to support one approach over others, we would like to highlight the EASy-ALS protocol (outlined in Table 1, Figures 1 and 2, and Video 9). The EASy-ALS protocol is the protocol utilized by anesthesiology residents during IHCA.²² This protocol calls for prerequisite training including simulation, which focuses on teamwork, communication, high-quality CPR, and limiting pulse/rhythm checks to fewer than 10 seconds. In our experience, simulation-based training results in consistent shortening of interruptions in CPR during simulated cardiac arrest.²³

Table 1. EASy-ALS protocol

Figure 1. Algorithm for the use of EASy-ALS. This algorithm incorporates FOCUS into the ≤10-s pulse/rhythm check of CPR. A systematic approach allows identification of a shockable rhythm if present and completion of EASy-ALS to search for a cardiac cause of the event without holding chest compressions for >10 s. (Used with permission from N. Bughrara, MD, Albany, NY.) CPR indicates cardiopulmonary resuscitation; EASy-ALS, echocardiographic assessment using subcostal-only view in advanced cardiac life support; FOCUS, focused cardiac ultrasound; PEA, pulseless electrical activity; ROSC, return of spontaneous circulation; RWMA, regional wall motion abnormality; VF, ventricular fibrillation; VT, ventricular tachycardia.

Figure 2. Pseudo-PEA phenotypes identified with EASy-ALS. The primary phenotypes to be identified with EASy-ALS are pericardial effusion, which may result in pericardial tamponade, dilated right heart, which pay occur with massive PE, dilated left heart, which may be seen with massive MI, and underfilled heart, which is associated with hypovolemia. Extracardiac views may be obtained as well; these include IVC ultrasound to assess volume status and RV filling pressure and lung ultrasound to assess for pleural effusion or tension pneumothorax. (Courtesy of N. Bughrara, MD, Albany, NY). EASy-ALS indicates echocardiographic assessment using subcostal-only view in advanced cardiac life support; IVC, inferior vena cava; MI, myocardial infarction; PE, pulmonary embolism; PEA, pulseless electrical activity; RA, right atrium; RV, right ventricular.

Supplemental Video 9. Demonstrating EASy-ALS in a simulated setting (click to view)

The responding resident is alerted to an acutely decompensating patient in the SICU or medical or surgical ward by direct call from the primary service or by overhead Code Blue page. On arrival, the resident prepares to serve as a sonographer and complete an EASy-ALS exam. The ultrasound probe is placed in the subcostal window before the pulse/rhythm check without obstructing chest compressions. The code leader, a senior primary care team provider, is responsible for holding and resuming chest compressions. The code leader assigns a nurse to count down 10 seconds during the pulse/rhythm check; this is standard at our institution. After resumption of chest compressions, the resident interprets recorded images and communicates findings to the code leader. The primary phenotypes (Figure 2) to be identified are cardiac standstill (see Video 1), pericardial effusion (Video 2), dilated right ventricle (RV) (Video 5), dilated left ventricle (LV) (Video 6), and underfilled heart (Video 7). The resident can obtain extracardiac views (such as the subcostal IVC View, Video 3), between pulse/rhythm checks.

Local Anesthetic Systemic Toxicity

Local anesthetic systemic toxicity (LAST) can occur during any type of regional anesthesia and can lead to cardiac arrest, particularly when high volumes of long-acting local anesthetics (e.g., bupivacaine) are injected. Early signs of LAST include perioral numbness, metallic taste in the mouth, and tinnitus. Seizures and hemodynamic instability may ensue. Tachycardia and hypertension are followed by bradycardia and hypotension, and eventually by ventricular arrhythmias and asystole. LAST symptoms typically develop within one minute, although a delayed onset after more than one hour of injection has been described.²⁴

The role of POCUS during LAST is not well defined, but it could benefit the patient if cardiovascular collapse occurs late after LA injection. Expected findings include ventricular fibrillation or asystole, while other causes for hemodynamic instability can be detected as well.

During the resuscitation, POCUS may confirm either success (ie, reestablished synchronized cardiac activity) or failure (standstill) of therapy with lipid emulsion and trigger the initiation of cardiopulmonary bypass.

TEE in Cardiac Arrest Management

Obtaining surface ultrasound images can be limited by certain barriers like subcutaneous air or dressings in the areas of interest. In such cases, TEE can be used, although it is limited by its availability and the need for endotracheal intubation.^25-26  TEE has the ability to not only assist with the diagnosis of reversible causes of cardiac arrest but also to guide optimal chest compressions, since in about 80% of patients the intrathoracic structures immediately under the point of compressions are the ascending aorta, the aortic root, or the LV outflow tract. Thus, the compression point may need to be shifted toward the xiphoid process for more effective ventricular compressions.²⁷

Nibras Bughrara, MD, FCCM, FASA, is an associate professor of anesthesiology and surgery, the director of the Anesthesia Critical Care Division, and the director of Critical Care Echocardiography in the department of Anesthesiology and Critical Medicine at Albany Medical College in Albany, NY.

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Oliver Panzer, MD, is an associate professor of anesthesiology, the director of Perioperative Ultrasound, and the co-director of the post-anesthesia care unit in the department of Anesthesiology and Critical Care Medicine at Columbia University Medical Center in New York, NY. 

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Aliaksei Pustavoitau, MD, MHS, FCCM, is an associate professor of Anesthesiology and Critical Care Medicine, the director of the Perioperative Ultrasound Program, the medical director of Respiratory Care Services and the director of the Hopkins Triage and Integration Physician Program in the department of Anesthesiology and Critical Care Medicine at Johns Hopkins School of Medicine in Baltimore, MD.

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