No matter which way you look at it, the research on pre-hospital TOR is clear: OHCA patients who fulfill BLS or ALS TOR criteria most often do not survive to hospital discharge. Studies consistently show a survival of less than 0.5% if BLS TOR criteria are followed and 0% if ALS criteria are followed. Studies also show transportation rates of 40-60% if BLS criteria are followed and around 80% if ALS criteria are followed. In spite of this, research suggests that there are barriers to the implementation of TOR criteria by EMS providers. The Termination of Resuscitation Implementation Trial (TORIT) was a multi-center prospective trial that evaluated the implementation of TOR rules in patients with OHCA. The investigators showed that in 953 patients who were BLS TOR eligible, EMS providers correctly applied the rule in 755 patients (79%) and did not apply the rule in 198 patients (21%). All of the 198 patients in whom the rule was not applied (i.e. they were transported to the hospital despite meeting BLS TOR criteria) did not survive. For these patients, providers were surveyed regarding their decision to transport. Family distress was the most commonly cited reason for continuing resuscitation and transporting patients [10].

Is there a magic number?

Studies have shown that pre-hospital ROSC is the most important predictor of survival for patients with OHCA. An important question often arises: how long should EMS providers work these patients in the field? The prospective 1993 study by Bonnin, et al. showed that in 1471 patients with OHCA, only 370 patients achieved ROSC on scene. Of these 370 patients, all patients achieved ROSC within 25 minutes of paramedic arrival. Newer research coming out of Wake County EMS has shown that working patients longer may be of benefit. In 2905 adult OHCA patients that were examined retrospectively, 363 survived (12.5%). Of the survivors, 300 patients (83%) were neurologically intact. The investigators found that duration of prehospital resuscitation was less than 40 minutes in 90% of neurologically intact survivors [11]. Other studies have shown neurologically intact survival with duration of resuscitation times ranging between 35 to 60 minutes. This broad range may likely be attributed to variation in EMS practice and available resources (i.e. therapeutic hypothermia) as it pertains to agency specific protocols for OHCA.

And what about traumatic cardiopulmonary arrest?

Prehospital TOR may also play a significant role in patients suffering from traumatic arrest as well. While there are sets of robust decision rules validated for TOR and nontraumatic cardiopulmonary arrest, the research on TOR in traumatic arrest patients is scarce.

In 2012, the NAEMSP in conjunction with the American College of Surgeons Committee on Trauma (ACSCOT) released a joint position statement addressing this issue. Based on a review of the literature, the NAEMSP-ACSCOT paper estimated that survival rates for traumatic cardiopulmonary arrest is approximately 2%. This position paper differentiates between withholding resuscitation in cardiopulmonary arrest and TOR.

The guidelines recommend withholding resuscitation in the following patients with traumatic arrest [12]:

· Whom death is the predictable outcome

· Injuries incompatible with life (i.e. decapitation, hemicorporectomy)

· Blunt or penetrating trauma with evidence of prolonged cardiac arrest (i.e. rigor mortis)

· Blunt trauma patients who are apneic, pulseless, without organized EKG activity

· Penetrating trauma patients who are apneic without signs of life (i.e. no spontaneous movement, EKG activity, pupillary response)

The paper makes the following comments regarding TOR in traumatic arrest:

· The primary focus should be evacuation to an appropriate facility for definitive care

· EMS systems should implement protocols that allow for TOR in cases of traumatic arrest

· TOR should be considered in patients without signs of life or without ROSC

· Protocols should be in place that require for a specific interval of CPR (for example, up to 15 minutes prior to termination)

· TOR protocols should be accompanied by procedures to ensure appropriate management of the deceased patient and support services for family members

· Physician oversight is a mandatory component of TOR protocols

· TOR protocols should include locally specific clinical, environmental or population based situations for which the protocol may not be applicable

· Further research is required to determine optimal duration of CPR before TOR

A criticism of the NAEMSP-ACSCOT guidelines is their degree of detail and likely inability to be implemented in the field. A recent paper published in 2016 from Taiwan looked at a simplified decision rule for TOR in patients with traumatic cardiopulmonary arrest modified from the NAEMSP-ACSCOT guidelines. The simplified decision rule included two criteria: 1) blunt trauma injury AND 2) presence of asystole. The study found that this TOR rule could accurately predict 100% of non-survivors and had the potential to decrease ambulance transports for traumatic cardiopulmonary arrest between 16.4-29.0% [13].

Take home points

· The majority of patients with nontraumatic OHCA who do not achieve ROSC in the field have a very poor prognosis

· Identifying patients with OHCA who will most likely have an unfavorable outcome and not benefit from transport with lights and sirens is important with regards to EMS safety and utilization.

· The BLS and ALS TOR criteria derived from the OPALS cardiac arrest registry have been validated and are good predictors for which patients can be pronounced dead in the field

· TOR may have an important role in patients suffering from traumatic arrest, however further research is still needed

· There is still no widely accepted guidelines in terms of duration of prehospital resuscitation for OHCA, however several studies have shown successful outcomes ranging from 25 to 60 minutes

· There are still barriers to implementation of TOR criteria which may explain underutilization by EMS agencies. As family distress is the most commonly cited region for falling out of protocol, additional training of EMS personnel in communication skills, as well as public education will be important to successful implementation.