By Kristen Bascombe, MD; Elena Cappello, MD and Eric Silverman, MD, MPH
Abstract
The use of point-of-care ultrasound (POCUS) in acute care medicine has become standard practice in the emergency department. Specifically, POCUS is frequently used during the management of cardiac arrest to identify reversible causes and assess cardiac activity.
POCUS may be a useful prehospital tool for improving the management of out-of-hospital cardiac arrest (OHCA) by emergency medical services (EMS) clinicians. We describe a case of OHCA in which an EMS physician uses POCUS to guide management.
Introduction
Point-of-care ultrasound (POCUS) is commonly used during in-hospital management of cardiac arrests to evaluate for organized cardiac activity. POCUS is also used to identify reversible causes of cardiac arrest, such as cardiac tamponade, pneumothorax, or massive pulmonary embolism.
With an estimated 350,000 out-of-hospital cardiac arrests (OHCA) annually in the United States1 and an increasing focus on field resuscitation by emergency medical services (EMS) clinicians, POCUS may also be a useful tool to guide prehospital care.
Narrative
A first responder fire engine and ALS ambulance were simultaneously dispatched code 3 for a 41-year-old female “sick person.” The engine arrived first and found a female who was ill-appearing with waxing and waning mental status.
Moments later, the patient became unresponsive and was found to be in cardiac arrest. Advanced Cardiac Life Support (ACLS) was initiated, and a mechanical compression device was applied to the patient.
Due to concerns regarding scene safety, the patient was moved to the ambulance where resuscitative efforts were continued. The patient was noted to have spontaneous movement of her right arm and leg during CPR.
Her eyes were open, but she did not track or blink to threat. The patient’s clenched jaw prevented intubation. The EMS clinicians reasoned that the patient had either obtained ROSC or showed signs of good cerebral perfusion due to high quality CPR. They questioned the best next step and whether they should continue ACLS.
By the next pulse check, an EMS fellow arrived on scene with a portable ultrasound. The fellow performed a POCUS to assess cardiac activity and noted an absence of organized activity, reassuring the EMS clinicians to continue providing high-quality ACLS care in route to the Emergency Department.
Discussion
We describe a case in which prehospital POCUS provided key information during resuscitation of a patient with OHCA. EMS clinicians questioned whether the patient had ROSC based on her eye opening and spontaneous movement of extremities.
While these signs indicate adequate cerebral perfusion, they may occur during high quality CPR, known as CPR-induced consciousness (CPRIC), or as a result of ROSC. Instead of stopping CPR prematurely, the EMS clinicians continued ACLS, and an EMS fellow performed a POCUS evaluation during the next pulse check.
Using prehospital ultrasound, the EMS fellow was able to definitively determine the absence of organized cardiac activity and need for ongoing ACLS. The additional information obtained through prehospital POCUS ensured ongoing optimal management of OHCA while in route to the Emergency Department.
Over the past few years, there has been an increase in CPR-induced consciousness, a scenario where the patient demonstrates signs of awareness such as eye opening, purposeful movements, or verbal response during CPR in the absence of return of spontaneous circulation2.
CPRIC can introduce additional challenges to cardiac arrest management, including but not limited to, untimely defibrillation, interruptions to high quality CPR, difficulty securing an airway, and difficulty maintaining a controlled environment.2
There are currently no prehospital guidelines endorsed by the AHA or other professional organizations. The call for more singular and streamlined criteria in CPRIC management has markedly increased, especially in the prehospital setting.
A recent scoping review of CPRIC guidelines globally discovered over 20 different approaches to management, including sedation with benzodiazepines, sedation with ketamine and/or pain control with opiates.2
In the prehospital setting, POCUS can be utilized to make the important distinction between CPRIC and ROSC with hypotension, leading clinicians down the path of accurate and optimal management, as with this case.
POCUS is currently utilized during the management of cardiac arrest to identify reversible underlying etiologies and to evaluate for ROSC. Cardiac tamponade, pneumothorax, and massive pulmonary embolism are potential causes of cardiac arrest that can be directly identified using POCUS.3
We sought to further explore the literature on benefits and feasibility of using ultrasound in the prehospital setting. Cardiac activity on POCUS has been shown to be a strong predictor of survival from cardiac arrest.4
Additionally, when compared to POCUS, traditional prognostic factors such as initial asystole, patient downtime, and bystander CPR do not significantly predict OHCA survival.5
Cardiac activity on prehospital POCUS has been shown to correlate with a ROSC rate of greater than 50%.6 Furthermore, studies have demonstrated increased survival when prehospital ultrasound is used to guide interventions (15.4% versus 1.3%).4
POCUS may be particularly helpful in the prehospital setting due to the ability to rapidly identify and intervene on the underlying etiology of cardiac arrest. These interventions can be performed at the scene without interfering with resuscitation efforts.7
In a 2013 study, early diagnostic use of POCUS led to changes in management in 89% of patients undergoing CPR.8 Another study in 2006 demonstrated that ultrasound was 90% sensitive and 98% specific for diagnostic findings during undifferentiated cardiac arrest, hypotension, and massive hemoperitoneum.9
Prehospital POCUS is well suited to diagnose cardiac standstill (97.5% PPV), pneumothorax (90% PPV), pleural effusion as a marker for congestive heart failure (~100% sensitivity), and a need for laparotomy due to intra-abdominal free fluid (96% NPV).10
Additionally, prehospital POCUS has high sensitivity for hemoperitoneum as a cause of hypotension, decreasing the rate of unnecessary needle thoracostomies by up to 26%.8
One significant limitation to prehospital POCUS is variation in the ultrasonography skill of the clinician.8,10 Specific training in obtaining and interpreting ultrasound images that guide management is essential.10
Potential challenges for implementing prehospital POCUS include the cost of purchasing ultrasound equipment, time to appropriately train EMS clinicians, and the need for ongoing quality assurance of both image acquisition and interpretation. Despite these barriers, the benefits of prehospital POCUS are significant.
Conclusion
In this case, an EMS physician used POCUS in the prehospital setting to guide ACLS management and recognize CPR-induced consciousness.
POCUS can be a useful tool for EMS clinicians who have appropriate training and medical oversight. The use of prehospital POCUS has many benefits, including the identification of treatable causes of cardiac arrest, identification of ROSC, evaluation of compression quality, guidance of procedures and decreased time to intervention and diagnosis.
Further guidance is needed to determine best practices and feasibility for implementing prehospital POCUS performed by EMS clinicians and management of CPRIC in the prehospital setting.
About the Authors
Dr. Kristen Bascombe, MD, is an EMS physician and assistant clinical professor of Emergency Medicine at Highland General Hospital. She completed an EMS fellowship at the University of California San Francisco and currently serves as the EMS Base Hospital medical director at Highland General Hospital.
Elena Cappello, MD, is a PGY-3 EM resident physician in San Francisco, California, with interest in EMS, Ultrasound and diversifying the field of medicine.
Eric Silverman, MD, MPH, is an EMS physician and associate professor of emergency Medicine at the University of California, San Francisco. He works clinically in the Emergency Department at San Francisco General Hospital and Trauma Center where he also serves as the EMS Base Hospital medical director and director of the EMS & Disaster Medicine Fellowship. Dr. Silverman also serves as the medical director for King-American Ambulance Company in San Francisco.
References
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