Intravascular Clotting (POCUS) - Marker of the Timing and Severity of Cardiac Arrest; Indicator of Futile Resuscitation

Introduction:

More than one million sudden cardiac arrests requiring cardiopulmonary resuscitation (CPR) occur each year in the United States and Europe. A point-of-care test to assess prognosis during resuscitation is a desirable clinical tool. Post-mortem intravascular clotting is considered an early sign of death. The detection of signs of clotting (spontaneous echo contrast or thrombus) in the cardiac cavities in an ultrasound examination during resuscitation may be an indicator of the severity of cardiac arrest and a marker of futile resuscitation. Performing transthoracic echocardiography during resuscitation is only possible during short breaks to assess the heart rhythm and pulse. Research shows that the use of transthoracic examination might cause additional interruptions in chest compressions. The use of a transesophageal examination, which can be performed during compressions, is only possible in specialized centers.

An examination that allows for the detection of intravascular clotting and at the same time does not require interruption of chest compressions is ultrasound assessment of deep veins. There is no data in the literature on the time that must pass from cardiac arrest to the occurrence of intravascular clotting, the frequency of clotting in deep veins during resuscitation and its importance for the resuscitation outcome.

Confirmation of the usefulness of the ultrasound-detected clotting in deep veins during resuscitation in assessing the severity of cardiac arrest and the prognosis of resuscitation, which is the aim of the project, will have an impact on international guidelines for determining the prognosis and potential futility of resuscitation.

Objectives of the study:

1. ultrasound assessment of the incidence of clotting in deep veins in patients after cardiac arrest during resuscitation and after the declaration of death; comparison to the incidence of clotting in the heart cavities
2. comparison of resuscitation results in patients with and without clotting detected in deep veins during resuscitation
3. determining the time from cardiac arrest to the occurrence of clotting in deep veins; comparison to the time until clotting occurs in the heart cavities

Methodology:

The study is planned to be prospective and double-blind. The study concerns emergency department patients after cardiac arrest who will undergo ultrasound examination during resuscitation and after declaration of death in the event of unsuccessful resuscitation. The first phase of the study will involve obtaining ultrasound images by clinicians not directly involved in patient care and resuscitation. Treating clinicians will be blinded to sonographic results except those concerning the cause of cardiac arrest. The images will then be externally evaluated for the presence of clotting by 2-3 assessors. These ultrasound assessors will be blinded to clinical outcomes of resuscitation and the timing of ultrasound examinations. The results of ultrasound examinations will be compared with data from the course and result of resuscitation. The time it takes for clotting to occur in the deep veins and heart cavities after cardiac arrest will also be determined.

The project concerns patients who suffered cardiac arrest and underwent cardiopulmonary resuscitation in the emergency department. The planned research group is 40 patients.

Timing of the ultrasound assessment Assessment of clotting in the deep veins and cardiac cavities during resuscitation will be performed once in every subsequent ten minutes of resuscitation (first examination: 1-10 minute of CPR; second examination: 11-20 minute of CPR, etc.). Bilateral ultrasound assessment of the common femoral veins and internal jugular veins will be performed during chest compressions, and transthoracic ultrasound assessment of the heart during breaks between chest compressions.

Assessment of clotting in the deep veins and heart cavities will be performed in three consecutive ten-minute periods after declaration of death (first examination: 1-10 minute; second examination: 11-20 minute; third examination 21-30 minute). The assessment will consist of bilateral ultrasound examination of the common femoral veins, internal jugular veins and transthoracic examination of the heart.

Study definitions Clotting will be considered present if the ultrasound image shows spontaneous echo contrast or thrombus.

Ultrasound protocols Ultrasound images will be obtained by the experts in point-of-care ultrasound who will not be directly involved in patient care and resuscitation. Each expert will be trained in the required examination protocol, including the time, type and quality of ultrasound examinations to be performed. Treating clinicians will be blinded to sonographic results to eliminate the risk of confounding from self-fulfilling prophecy. However, they will be informed of ultarsound findings that could influence clinical treatment such as mechanical ventricular activity and evidences of pulseless electrical activity reversible causes (pericardial effusion, right ventricular dilation, deep venous thrombosis in common femoral veins).

Ultrasonography imaging protocols followed during cardiac arrest and after declaration of death to assess clotting in the common femoral veins will rely on bilateral B-mode inspection for clotting and the compression ultrasound technique of the common femoral vein from the inguinal ligament until it becomes the femoral vein. Veins will be evaluated both in the transverse and longitudinal plane.

The protocols to assess clotting in the internal jugular veins will rely on bilateral B-mode inspection for clotting and the compression ultrasound technique of the internal jugular vein at three levels: (1) proximal portion of the jugular vein and the subclavian/innominate vein, (2) level of thyroid gland, (3) level of carotid bifurcation. Veins will be evaluated both in the transverse and longitudinal plane.

Echocardiography imaging protocols followed during cardiac arrest and after declaration of death will rely on three equivalent transthoracic B-mode views: (1) subcostal long-axis; (2) parasternal long-axis, (3) parasternal short-axis, and at minimum, (4) apical 4-chamber to assess all chambers for clotting.

The linear type of transducer will be used for the inspection of veins and the phased array type of transducer will be used for echocardiography.

Image adjudication All study images will be reviewed by at least 2 of 3 experts in point-of-care ultrasound to calculate inter-rater reliability for thrombus and spontaneous echo contrast identification. If there will be disagreement between diagnoses, a third reviewer would make the tiebreaker decision. These ultrasound assessors will be blinded to clinical outcomes of resuscitation and the timing of ultrasound examinations during the quality assurance oversight process.

Resuscitation data collection Other relevant resuscitation data concerning patient, pre-event data, cardiac arrest process and outcomes will be collected using the Utstein resuscitation registry template.

Potential Outcomes:

Confirmation of the usefulness of the ultrasound-detected clotting in deep veins during resuscitation in assessing the severity of cardiac arrest and the prognosis of resuscitation will have an impact on international guidelines for determining the prognosis and potential futility of resuscitation. Given the global number of cardiac arrests and resuscitations, shortening resuscitation efforts in selected cases will mean enormous savings in manpower and resources.

Confirmation of the effectiveness of the use of ultrasound in the assessment of early post-mortem changes in the vascular system may influence the development of forensic medicine through wider use of ultrasound.