The call came into the Pittsburgh 9-1-1 communications center at 7:42 a.m. for a young female unconscious and not breathing, found lying outside on a stairwell. Pittsburgh EMS Medic 5 was advised en route that bystanders thought the patient was deceased, but when law enforcement arrived a few minutes later, they detected a weak pulse and rapidly moved the woman inside to get her to a warmer environment.
Medic 5 arrived shortly after, confirmed the patient had a pulse and placed her on their cardiac monitor, which showed she was bradycardic.
Because she felt extremely cold to the touch (hypothermic), the EMS crew began transport immediately. En route, she went into v tach without pulses and was defibrillated once. With no conversion, the crew continued CPR until they reached the University of Pittsburgh Medical Center (UPMC) Presbyterian ED, a Level 1 trauma center.
Author Vincent Mosesso, MD, was working the early morning shift in the ED and, along with the rest of the ED staff, was presented with a hypothermic patient with snow on her clothing and a bare left foot.
He noted an occasional gasping breath and some jerking movements of her trunk and extremities, but there was no regular breathing and the team couldn’t feel any definite pulse.
The cardiac monitor showed no organized complexes and there was significant baseline artifact. Thus, chest compressions and ventilation were continued, with care being taken to deliver just 6—8 breaths per minute.
The resuscitation team was determined to perform high-quality chest compressions: good depth, rate and recoil with limited interruptions. They positioned a compressor on both sides of the patient’s chest and alternated compressors at least every two minutes.
Nurses placed an intraosseous (IO) catheter in the patient’s right proximal tibia along with two peripheral IVs. One mg of epinephrine was given initially, but the team intentionally restricted drug administration due to suspected severe hypothermia and the knowledge that high doses of epinephrine are associated with worse neurological outcomes.1,2
After several minutes of chest compressions, an emergency medicine resident intubated the patient using a video laryngoscope. The team continued to ensure ventilations didn’t exceed eight per minute.
The patient’s temperature was 78.8 degrees F, prompting the team to begin specialized rewarming efforts. Warm IV fluids had been hung as soon as access was obtained. A nasogastric tube and Foley catheter were also placed and the patient was lavaged.
A warming blanket was placed over the patient without interruption of chest compressions. An esophageal thermometer probe was placed and the initial reading was 75.2—77 degrees F. Since initial rewarming efforts weren’t effective, a trauma surgeon was consulted to place a peritoneal catheter for warm water lavage.
The cardiothoracic (CT) surgery team was consulted for consideration of emergency peripheral cardiopulmonary bypass (eCPB), also known as extracorporeal life support (ECLS) and often referred to as extracorporeal membrane oxygenation (ECMO).
The CT surgery attending, fellow and a perfusionist were in house, so eCPB was begun rapidly. This proved to be a key factor in the resuscitation of this young patient.
Large sterile catheters were immediately placed in her femoral artery and vein. The catheters and pump were primed to purge them of any air and then attached to the indwelling catheters.
All the while, high-quality continuous chest compressions were maintained with multiple persons rotated frequently. One additional mg of epinephrine was administered along with 20 units of vasopressin and 50 mEq of bicarbonate.
The patient had received about 3 L of warm saline at this point. Because of the blood loss during catheter placement and to assure adequate circulatory volume (effective vascular space increased by the extracorporeal volume), the team also transfused several units of type O negative blood.
Once catheters and tubing connections were secured, and after over an hour of continuous manual chest compressions, eCPB was initiated to start the mechanical pumping of the patient’s blood. The flow rate was gradually increased to 4 L/min, at which time compressions were discontinued and the ventilator rate was lowered. The eCPB device was oxygenating the blood, and decreasing ventilations allowed increased venous return to the thoracic cavity.
Within minutes of starting the procedure, the patient’s temperature began to rise. V fib then developed. When her temperature rose to 86 degrees F after five minutes, she was defibrillated at 200 J. She immediately converted to a sinus rhythm with narrow complexes at a rate of 90—100 bpm.
She now had palpable central and peripheral pulses and soon began to have some spontaneous respiratory effort and some non-purposeful movements. Her response required that she be sedated and restrained.
The CT surgeon placed an 8.5 French catheter introducer into her left femoral vein and a right femoral arterial line. The arterial line tracing revealed a mean arterial pressure (MAP) in the 70s, so a vasopressor infusion wasn’t needed. Catheters, tubes and lines were all secured and she was transferred to the CT ICU for further care.
The patient, Emily, a 19-year-old college student, would go on to have a wonderful recovery. The eCPB was discontinued and she was taken off the ventilator within just one day. She did well neurologically too, scoring one of the highest scores ever on the cognitive impairment test, and was discharged less than a week after her cardiac arrest.
This successful resuscitation of a 19-year-old female, found unresponsive outside with severe hypothermia and in cardiac arrest, involved the teamwork of the Pittsburgh paramedics, early-arriving police officers and fire first responders, and innumerable hospital staff in the ED and in other UPMC departments.
This case serves to highlight the potential eCPB therapy may have for the resuscitation of other patients in the ED with refractory cardiac arrest or other extreme critical illnesses that require assisted circulation or oxygenation, such as severe septic shock, acute severe heart failure or a large pulmonary embolism causing obstructive shock.3
The ECMO equipment and circuit are used to boost oxygen level in the blood. There’s an oxygenator in the circuit that enables blood to be pumped at a fraction of normal cardiac output (typically 1—2 L/min in an adult).
ECMO Overview
As mentioned above, several terms are used to describe the use of external blood circulation to resuscitate or support the patient. All of these techniques involve pumping blood through an external circuit. During this process, the patient’s blood is pulled through large catheters out of a central vein, pumped with a mechanical pump, passed through an oxygenator, and then returned back to a central vein or artery.
The ECMO equipment and circuit are used to both boost the oxygen level in the blood and to mechanically pump blood. The term ECMO typically refers to when this technology is used for oxygenation when lungs fail but circulation is adequate.
ECLS and eCPB refer to the complete replacement of cardiac output, with blood pumped at near normal cardiac output (3—5 L/min in an adult) and returned to an artery (veno-arterial bypass). Some authors also use the term eCPR for extracorporeal CPR.
In summary, ECMO may be used when lungs are severely injured, such as with severe influenza pneumonitis and adult respiratory distress syndrome (ARDS). eCPB/ECLS/eCPR is used in failing hearts and for cardiac arrest.
How ECMO Is Provided
ECMO can be provided by two approaches, both of which use a large catheter in a large vein to extract blood from the patient. But after oxygenation, blood can be returned either into a vein (termed venovenous [VV]) or an artery (venoarterial [VA]).
VV ECMO can be used for oxygenation and rewarming, but not for circulatory support. Therefore, this modality can only be used in patients with adequate spontaneous circulation. One catheter is typically placed in the right common femoral vein for drainage while the other is typically placed in right internal jugular vein for infusion.
VA ECMO permits circulatory support in addition to oxygenation and rewarming. Most resuscitation teams prefer to use the term emergency cardiopulmonary bypass (eCPB) or extracorporeal life support (ECLS) to differentiate it from VV ECMO.
The term peripheral CPB has been used to differentiate this usage from open heart surgery and placement of catheters directly into the aorta and vena cava. Still, there’s the potential for confusion as the peripheral form involves placement of catheters into “central” vessels. The venous catheter is typically placed in the right common femoral vein for drainage while the arterial cannula is typically placed in the right femoral artery for infusion.
The desired amount of blood flow through this circuit ranges from 3—6 L/min. Flows are set high enough to provide adequate perfusion pressures and left ventricular output, and can maintain adequate circulation even if the native heart isn’t pumping.
Interestingly, while there is now a growing interest for emergent uses, CPB dates back to the heart-lung machine invented in 1953. CPB as we now know it was first used in neonates in 1976. The University of Pittsburgh started a research study on peripheral cardiopulmonary bypass for cardiac arrest in 1991. Although the first person enrolled was successfully resuscitated, the study was halted for logistical reasons.
A recent meta-analysis found there have been many case reports and case series published on eCPB use in resuscitation with an overall survival of 44%, which is quite good for survival from cardiac arrest or cardiogenic shock.4
Emily and members of her resuscitation team reunite on the one-year anniversary of her ECMO save.
Emergent & Critical Care Uses & Potential
As presented in this case review, eCPB can be used to actively rewarm a hypothermic patient. Hypothermia is defined as a core body temperature less than 95 degrees F.
Hypothermic patients are at risk for experiencing v fib, hypoxia from breakdown of the alveolar membrane and extravasation of fluid into the alveolar airspaces, and hypovolemia due to shifts in body fluid from the intravascular to the extracellular space.5
Further decrease in core body temperature occurs when peripheral blood is circulated into the core (afterdrop). eCPB is the most effective method for rewarming in severe cases of hypothermia and provides circulatory support as well, but VV ECMO may be used when spontaneous circulation is present.6 This modality can also be used for cooling patients; while it’s not generally needed for treatment of primary hyperthermia, patients who are post-arrest or severe nonhemorrhagic shock may benefit from therapeutic hypothermia.
eCPB is now emerging as a potential lifesaving therapy for refractory cardiac arrest and severe shock, particularly when there may be a reversible condition as the etiology and for patients who would be a candidate for heart transplant or ventricular assist device.7
As pointed out in our case study, implementation of ECMO/eCPB therapy requires extensive preplanning and collaboration between the ED, emergency physicians, CT surgeons (or acute care surgeons), critical care physicians and support staff, including perfusionists and nurses. Protocols must include coordination with EMS and air medical crews for patient selection, hospital notification, timing and mode of transport and the content and extent of on scene care.
As an example of how ECMO/eCPB can and is being used today, consider a middle-aged person who suddenly arrests in v fib from an acute myocardial infarction. First responders arrive, start CPR and shock the patient without success. EMS arrives, continues high-performance CPR and administers epinephrine and then amiodarone, but the patient remains in v fib despite several more shocks. EMS places a mechanical CPR device on the patient and transports immediately to the closest cardiac arrest center. eCPB is initiated, the patient is taken to the cardiac cath lab, the totally occluded left anterior descending artery is opened and stented, and the patient is then shocked into a perfusing rhythm.
Finally, patients may require eCPB only for oxygenation support. This past influenza season was notable for high-severity patients who were difficult to treat and resuscitate, particularly younger adults, the population often least affected. Influenza A (H1N1) was the primary strand for the 2013—2014 season. These patients typically present with a 1—2 day history of upper respiratory symptoms in mild to moderate respiratory distress. As the flu progresses, it brings the potential for fulminant acute respiratory distress syndrome (ARDS).
The lungs experience capillary leaks, surfactant depletion, collapse/consolidation, ventilation perfusion mismatch, and a reduction in lung compliance. ARDS patients typically end up requiring endotracheal intubation for ventilatory support.
When traditional ventilator management fails, alternative strategies such as nitric oxide, high frequency oscillatory ventilation, or prone positioning are considered. If these alternative measures fail, these patients face severe hypoxemia, hypercapnia, and a lack of recruitment despite increasing positive end-expiratory pressure and mean airway pressures. VV ECMO provides respiratory support as a bridge to recovery for these patients.
Implications for EMS
Prehospital providers should be aware of these specialized modalities and know which hospitals in their area are prepared to implement them. Typically this will be available at tertiary care centers and Level 1 trauma centers.
It’s possible to transfer patients on eCPB or ECMO between hospitals. This requires the expertise of a critical care transport team that’s been trained in caring for these types of patients.8 (See Unique Inter-Facility ECMO Transfer sidebar, below.)
The transferring team must monitor the ECMO patient closely with two considerations in mind: the patient’s volume status and the patient’s vascular status. Patients with a volume problem will require resuscitation with blood products or albumin. Patients with vascular problems will require pressor support. The first-line choice is typically epinephrine; however, it’s not uncommon to see norepinephrine.
A key concept in performing eCPB transports is remembering that you don’t perform CPR on these patients–the pump is doing the work of the heart (even with otherwise nonviable rhythms) along with medications and fluids. The oxygenator takes the place of the lungs.
Typically, patients are maintained on low volume ventilator settings to prevent atelectasis. Providers shouldn’t expect a normal end-tidal carbon dioxide (EtCO2) waveform because there’s no significant gas exchange occurring in the lungs.
The highest risk complication in these patients is bleeding. Don’t be afraid to use a hemostatic dressing to control the bleeding, but be careful when applying direct pressure at the catheter entry site as this can cause the cannulas to be pinched off, severely decreasing the amount of blood flow through
the circuit.
There’s also a risk of thromboembolism despite heparinization. Lastly, watch out for hypoxia. It may be difficult to assess on physical exam given the patient’s perfusion status as pulse oximetry won’t be accurate in the absence of pulsatile flow. Ensure the oxygen tube is securely connected to the oxygenator after every move.
As noted previously, there should be collaboration between hospitals and EMS providers regarding patient selection, notification, and treatment and transport protocols. Patients in cardiac arrest, severe shock with a potentially reversible cause or severe hypothermia with unresponsiveness are potential candidates.
Conclusion
eCPB is an emerging modality for managing near-death patients with potentially reversible conditions, yet much has yet to be determined about how to most effectively and judiciously implement this technology in emergency situations.
EMS providers will be a critical link in the provision of this lifesaving care because they’ll be called upon to identify potential patients, provide key prehospital interventions and rapidly transport to centers capable of providing eCPB on an emergent basis. Prehospital providers should be aware of this therapy and be prepared to act–your next call could be for another Emily.
References
1. Hagihara A, Hasegawa M, Abe T, et al. Prehospital epinephrine use and survival among patients with out-of-hospital cardiac arrest. JAMA. 2012; 307:1161—1168.
2. Callaway CW. Epinephrine for cardiac arrest [Review]. Curr Opin Cardiol. 2013;28(1):36¬—42.
3. Bellezzo JM, Shinar Z, Davis DP, et al. Emergency physician-initiated extracorporeal cardiopulmonary resuscitation. Resuscitation 2012;83(1):966—970.
4. Nichol G, Karmy-Jones R, Salerno C, et al. Systematic review of percutaneous cardiopulmonary bypass for cardiac arrest or cardiogenic shock states. Resuscitation. 2006;70(3):381—394.
5. Holleran, RS. ASTNA Patient Transport Principles and Practice, 4th Edition. Mosby Elsevier: St. Louis, Mo, 527—544, 2010.
6. Lloyd EL. Accidental hypothermia. Resuscitation. 1996;32(2):111—124.
7. Shin TG, Choi J, Jo IJ, et al. Extracorporeal cardiopulmonary resuscitation in patients with inhospital cardiac arrest: A comparison with conventional cardiopulmonary resuscitation. Crit Care Med. 2011;39(1):1—7.
8. Holleran, RS. ASTNA Patient Transport Principles and Practice, 4th Edition. Mosby Elsevier: St. Louis, Mo., 435—470, 2010.
A mobile intensive care ambulance takes an ECMO patient inside a Norwegian Air Force C130 for transfer to Oslo University Hospital in Oslo, Norway. Photos courtesy Ronald Rolfsen
UNIQUE INTER-FACILITY ECMO TRANSFER
A mobile intensive care ambulance takes an ECMO patient inside a Norwegian Air Force C130 for transfer to Oslo University Hospital in Oslo, Norway. Photos courtesy Ronald Rolfsen
Oslo University in Norway has an exceptional ALS response system that deploys multiple resources based upon patient needs. One example of its sophisticated approach to the care of critical patients is its unique system for the transfer of patients on ECMO from suburban and rural hospitals to the specialized center in Oslo.
When an ECMO patient needs to be transferred, the Oslo University EMS system retrieves the patient from the sending facility, often a great distance from Oslo, then transports that patient to an airfield in an intensive car ambulance with a portable ECMO unit in operation.
The entire ambulance then drives into a Norwegian Air Force C130 plane and the patient, ALS andhospital crew and portable ECMO equipment is transported in its entirety to the specialized center. There’s no interruption in care and the patient isn’t saddled with an aeromedical bill because of the country’s national health insurance coverage of the transfer.
–Ronald Rolfsen
The Oslo University Hospital mobile intensive care ambulance crew, patient and ECMO equipment remain in operation throughout the flight to the specialty center.
