ventilation was associated with better odds of neurologically favorable survival compared with any advanced airway [94]. Inconsistent conclusions among research studies result in challenges when developing systematic approaches to new considerations, such as risks associated with COVID‐19.
Post‐Resuscitation Care
Post‐resuscitation care and in‐hospital post‐arrest therapies are an important factor affecting survival after OHCA and subsequent functional outcome [95]. Significant morbidity and mortality after OHCA are due to cerebral and cardiac dysfunction in what has been termed the ‘post‐cardiac arrest syndrome’ [96]. Despite initial coma after OHCA, subsequent neurologic recovery can be influenced by in‐hospital post‐arrest treatments [97–99].
In 2015, ILCOR recommended avoiding hypoxia and hyperoxia in adults with return of spontaneous circulation (ROSC) after cardiac arrest. Patients should receive 100% inspired oxygen until either the arterial oxygen saturation or the partial pressure of arterial oxygen can be measured reliably [86]. partial pressure of carbon dioxide should be maintained within a normal physiological range.
Post‐resuscitation care should be tailored to hemodynamic goals, including mean arterial pressure and systolic blood pressure. Targets are patient specific. The AHA recommends avoidance or correction of hypotension, previously defined as systolic blood pressure greater than 90 mmHg or mean arterial pressure less than 65 mmHg. Prophylactic administration of antiarrhythmic drugs after ROSC is not recommended.
ILCOR recommends targeted temperature management, maintaining a constant temperature between 32 and 36 degrees C, in adults after ROSC from both shockable and non‐shockable rhythms, and the avoidance or treatment of fever after this [86]. They recommend that targeted temperature management is maintained for at least 24 hours post‐ROSC, but routine prehospital initiation with large volumes of cold intravenous fluid should not take place. Finally, they recommend against both routine seizure prophylaxis, although seizures should be treated, and modification of standard glucose management protocols.
Role of the Medical Director
Stewart commented, “Without dedicated medical leadership, the EMS system of a community flirts with mediocrity” [100]. The medical director plays a pivotal role in community systems of cardiac arrest care. It is the medical director’s responsibility to ensure that all components of the system are in place. The importance of medical director involvement cannot be overemphasized. Indeed, Williams et al. showed significant variation in EMS scope of practice with varying involvement of a medical director, and Greer showed that EMS agencies with paid medical directors or agencies with medical director interaction with EMTs in the preceding 4 weeks were more likely to have prehospital cardiovascular procedures in place [101, 102].
Training and Equipment
Cardiac arrest resuscitation requires timely and accurate execution of interventions. Because of the multitude of simultaneous tasks, cardiac arrest resuscitation requires a carefully coordinated team effort, potentially between rescuers from different agencies. EMS personnel should regularly train for cardiac arrest situations to determine the most efficient ways to carry out protocols. When possible, such training should involve the first‐responders who may also attend these incidents. Recent studies of medical emergency team training in simulation settings demonstrate the importance of teamwork and assigned roles [103, 104].
One systematic review described a lack of well‐designed studies examining the retention of adult ALS knowledge and skills in health care personnel, but commented that the available evidence suggests that ALS knowledge and skills decay by 6 months to 1 year after training, with skills decaying faster than knowledge [105]. Simulation has been shown to be superior in the development and maintenance of skills in cardiac arrest management. Learner satisfaction and competency outcomes favor simulation over non‐simulation teaching. Simulation‐based training for resuscitation is highly effective, particularly if employing strategies such as team/group dynamics, distraction, and integrated feedback [106].
Team training, particularly using simulation, may be helpful in improving safety and reducing anxiety among team members. For example, although defibrillator charging during chest compressions poses little risk, rescuers often do not follow the practice because of safety concerns [107].
EMS personnel must possess the equipment necessary to carry out cardiac arrest resuscitation. Key resuscitation equipment includes monitor‐defibrillators, airway management tools, vascular access equipment, and appropriate medications. Cardiac monitors that record and provide real‐time chest compression feedback are preferable, as are monitors that are able to use dynamic filtering to remove compression artifact and reveal underlying rhythms. However, one must remember that accelerometer‐based compression feedback devices overestimate chest compression depth when performed on soft surfaces [108].
In addition to intubation equipment, airway management tools should include capnography and alternate airway devices such as the Combitube®, King LT® airway, or iGel®. In addition to standard intravenous catheters, EMS crews should also carry rapid‐access vascular tools such as intraosseous devices. Medical directors should provide regular training on the use of all equipment. Even in busy systems, many personnel may not perform important skills or use specific equipment for months at a time.
Optimizing System Design
EMS medical directors should play a key role in developing the system design for cardiac arrest care. One potential intervention is to optimize the positioning of EMS and other resources to match areas with the most cardiac arrests. Geographic mapping systems can play an important role, illustrating not only the distribution of cardiac arrest cases throughout a community, but also variables such as the preferred placement of AEDs [109, 110]. The OPALS study reduced cardiac arrest response and defibrillation times by moving first‐responders closer to areas with more cardiac arrests [70].
Some have touted the advantages of system status management, a formal system of continuously redeploying units based on current and anticipated use [111]. Others suggest that skill dilution occurs with too many ALS personnel. They recommend using fewer ALS personnel in a tiered response fashion [111,112].. A Scottish study reported on an initiative to better formalize the roles of senior EMS personnel, who are known to be able to contribute characteristics essential to high‐quality resuscitation, including non‐technical skills such as resuscitation team leadership, communication, and clinical decision making in a second tier, expert paramedic response to OHCA [113].
Hospital Liaison
There is growing awareness of the importance of post‐resuscitation care, which formally constitutes the final link in the chain of survival [114]. Care initiated in the field may prove fruitless if not continued in the hospital. The medical director should work closely with receiving hospitals to ensure continuity in cardiac arrest care, and targeted interventions and care algorithms initiated in the field should be continued in the hospital. For example, when determining the receiving hospital facility, EMS agencies that induce hypothermia after cardiac arrest in unconscious survivors should consider whether the receiving facility will continue this therapy [115–119].
Studies are currently being performed that use a system‐based approach in an attempt to integrate therapies that may have synergistic effects, and that are likely to show co‐dependence in outcome. These are typified by the CHEER study, designed to treat cardiac arrest patients with mechanical chest compressions and cool them to 33 degrees C in the prehospital setting, place them on an extracorporeal membrane oxygenator at the hospital, transport them to the interventional cardiac catheter laboratory for angioplasty, then maintain hypothermia for 24 hours [120].
Davis et al. demonstrated that diverting patients post‐arrest past the closest available hospital and to a tertiary care center did not worsen outcomes [121]. Future work should consider if regionalization of care and transfer of these patients to specialty facilities improves outcomes as it does for victims of major trauma