Cardiac & Resuscitation, International, Patient Care

Derivation of a Termination of Resuscitation Clinical Decision Rule in the UK

Issue 8 and Volume 42.

In the United Kingdom, sudden cardiac arrest accounts for close to 100,000 deaths annually.1 Despite improvements in resuscitation practices,2 outcomes from OHCA remain poor, regardless of interventions utilized.3

In a one-year period during 2014-2015, approximately 30,406 out-of-hospital cardiac arrests (OHCAs) in England were transported to hospitals by ambulance, with a survival rate of 8.6%.4

Transporting patients with nearly certain poor outcomes represents an ineffective use of ambulance resources.5,6Termination of resuscitation (TOR) clinical decision rules (CDRs) for OHCA exist and have been validated.5,7,8

These TOR CDRs reduce the burden on both the ambulance and wider healthcare system, and improve public safety by reducing blue light transports, which present an inherent risk.

The guideline proposed after reviewing the study data compared
favorably with pre-existing termination of resuscitation guidelines.

Several studies have identified predictors of unsuccessful prehospital resuscitation, allowing for the development of evidence-based and validated TOR CDRs.9,10

The BLS guideline predicts that the patient will not survive to hospital discharge if the arrest isn’t witnessed by the ambulance clinician, there’s no return of spontaneous circulation (ROSC) before transport and no shocks have been administered.

The ALS guideline adds that the cardiac arrest must not have been witnessed by a bystander and there must have been no bystander CPR. Although these rules have been independently validated, it’s been shown that they’re not universal for all patient groups.11

Moreover, these studies involved systems with no pre-existing TOR guidelines. In systems where clinicians already terminate efforts on scene, the ALS guidelines have been shown potentially to increase the numbers of futile transportations.12

U.K. ambulance services are able to terminate attempts that have resulted in asystole following ALS.13 Therefore, the majority of patients transported to a hospital in the U.K. will be those who persist with pulseless electrical activity (PEA) on scene. (See Figure 1.)

The Resuscitation Council (U.K.) suggests evidence is less clear about when to stop a resuscitation where PEA persists.14 Although anecdotally senior clinicians do make decisions on whether to continue to resuscitate PEA, evidence suggests that the rationale for these decisions are many and varied and include internal factors, such as the clinician’s experience, as well as external factors, such as the expectations of family members and perceived patient characteristics.15

The European Resuscitation Council’s (ERC) 2015 CPR guidelines suggested that institutional TOR guidelines were needed for prehospital providers to reduce such variability in decision-making.16

Our North West Ambulance Service NHS Trust study sought to determine whether there were characteristics of adult OHCA of presumed cardiac cause that could predict outcomes, and propose an out-of-hospital TOR CDR.

Study Design

We used a retrospective cohort study to review all cases of adult OHCA of presumed cardiac etiology during a 26-month period. The aim was to determine characteristics of adult OHCA, which could be used to develop a CDR for TOR. Two existing TOR guidelines were also applied to the dataset for comparison.

The study received approval from our institutional research ethics board, NHS Health Research Authority and University research ethics board. Data for the study were taken from the North West Ambulance Service NHS Trust (the Trust), which covers large urban centers and remote rural areas, with a population of 7 million people across a geographical area of approximately 5,400 square miles.

The Trust has a combined technician (BLS) and paramedic (ALS) staff and has a TOR guideline which allows for termination only if, following 20 minutes of ALS, the patient is in an asystolic rhythm.

We retrospectively reviewed all adult OHCAs of presumed cardiac cause that occurred between April 1, 2011, and June 29, 2013, and were transported to a hospital. These data were collected by trained auditors of the Trust Governance Department from patient report forms (PRFs) completed by ambulance clinicians following every patient contact, and hospital records of patient outcomes.

Patients were excluded from the study if:

>> No resuscitation was attempted (e.g., death was diagnosed due to presence of rigor mortis, decomposition, etc);

>> The patient was under 18 years of age;

>> The arrest wasn’t presumed to have been of cardiac origin (e.g., the arrest was due to trauma, drowning or drug overdose);

>> The resuscitation attempt was terminated under current TOR guidelines; or

>> The patient’s outcome was unknown (some hospitals didn’t provide follow-up data).

Study Results

A total of 4,870 patients met the inclusion criteria for the study. (See Figure 2, p. 54.) During the study period, 8,316 cardiac arrests were managed by the Trust. Of these, 173 were under 18 years of age; 808 weren’t presumed to have been of cardiac origin (180 were trauma-related, 26 were submersions/drownings, 483 respiratory, 104 other and 14 unknown); 1,268 resuscitations were terminated under the existing Trust policy; 704 were taken to hospitals who didn’t share survival data and 493 had no data available on survival.

The mean age for the patient group was 71.5 years; 3,033 (62.3%) were male; and the median response interval for the first response (e.g., public access defibrillator, community first responder, etc.) was 6.67 minutes.

The median response interval from ambulance activation to arriving on scene was 10.24 minutes. The median interval on scene was 28.72 minutes and the median transport to hospital interval was 9.05 minutes.

Of 4,870 patients with complete follow-up 4,354 (89.4%) died and 516 (10.6%) survived to hospital discharge. In 4,859 cases (99.8%), it was recorded whether or not the arrest was witnessed; 2,383 of the patents (48.9%) had an arrest witnessed by a bystander and 646 (13.3%) were witnessed by an ambulance clinician. (See Table 1.)

In 100 (5.5%) of 1,830 unwitnessed arrests, the patients survived to discharge. Of the 2,383 witnessed by a bystander, 276 (11.6%) survived. This compares to 140 (21.7%) of the 646 patients whose arrest was witnessed by ambulance clinicians and survived.

The presence of bystander CPR was recorded for 4,836 (99.3%) patients. Of the 2,893 (59.8%) who received bystander CPR, 335 (11.6%) patients survived. In 1,943 patients, 40.2% of cases showed that bystander CPR wasn’t delivered.

Of these 180 patients, 9.3% survived. In 34 cases (0.7%), bystander CPR wasn’t recorded by ambulance personnel.

Of the 4,870 patients, 4,650 (95.5%) had a presenting cardiac rhythm recorded. Of these, 1,383 (28.4%) presented with a shockable rhythm (1,335 (27.4%) with v fib and 48 (1%) with v tach), 1,667 (34.2%) presented with asystole and 1,600 (32.9%) presented in PEA, with 183 (3.8%) recorded as “other” (for the purposes of analysis, this last group were listed as “unknown.”)

Of the patients presenting with shockable rhythms, 356 (25.7%) survived to discharge.

Only 80 (2.4%) of 3,267 patients presenting with a non-shockable rhythm survived to discharge (18.3% of total survivors).

A total of 1,833 (37.6%) patients were defibrillated at some point during the resuscitation. Of these, 399 (21.8%) survived, compared with 116 (3.8%) of the 3,035 (62.3%) who weren’t defibrillated.

Return of spontaneous circulation (ROSC) was achieved at some point in the field for 1,778 (36.5%). Of these, 1,286 (72.3%) died after hospital admission, and 492 (27.7%) survived to hospital discharge.

Of the 3,093 (63.5%) patients who failed to achieve ROSC, 3,068 (99.2%) died in hospital and 24 (0.8%) survived to discharge.

Binominal logistic regression was performed on six predictor variables (bystander CPR, bystander witnessed, clinician witnessed, initial shockable rhythm, defibrillation at any time and ROSC). Of these, three were found to be statistically significant: shockable rhythm, ROSC and clinician witnessed. (See Table 2, p 55.)

Further analysis showed that clinician-witnessed arrest wasn’t an independent predictor, but relied on an interaction with presenting rhythm. Therefore, this wasn’t included in the guideline.

The two remaining variables had a strong association with outcome; ROSC (OR = 40.3; 95% CI: 25.8% to 62.7%), and initial shockable rhythm (OR = 10.8; 95% CI: 6.7% to 17.4%).

Independently, ROSC had a positive predictive value of 99% and a specificity of 97.9%, and a presenting shockable rhythm had a positive predictive value of 97.4% and a specificity of 80.7%.

However, 4.7% (n = 24) of survivors didn’t attain ROSC before hospital arrival, and 18.3% (n = 80) of survivors didn’t present with a shockable rhythm.

Therefore, neither of these of these variables could be used independently as a prediction tool. As a result of this we included both initial shockable rhythm and ROSC in the TOR CDR.

The derived TOR CDR proposes TOR for adult OHCA of presumed cardiac cause where the presenting rhythm isn’t a shockable rhythm, and where no ROSC is achieved before transport. All other patients required transport for ongoing resuscitative efforts.

Retrospective application of this guideline to our sample indicated that all but five survivors were identified for transport. (See Figure 3.)
The five survivors equate to 0.2% of those terminated, which is below the threshold of 1% for futile interventions.17 The CDR would have resulted in transport rate of 52.5%.

Against this sample, the BLS and ALS CDRs discussed previously resulted in fewer unexpected survivors (3 BLS and 2 ALS survivors, respectively). However, this is at the cost of increased transport rates (63.1% BLS and 90.2% ALS, respectively). (See Table 3, p. 56.)


The issue of TOR in OHCA requires a balance between the need to achieve survival wherever possible, and the unnecessary use of limited resources for transporting and treating patients who have no chance of survival.

The transport of OHCA entails substantial costs and involves risk due to emergency blue-light transportation. Transport also removes the ambulance from other operational duties, which prevents its availability to other patients with potentially treatable conditions.

Once a patient in refractory cardiac arrest arrives at the receiving hospital, hospital clinicians are required to attend and are then unavailable to other patients.

There’s a need to balance the disadvantages of futile transportation with the need to recognize patients who have a chance of survival. U.K. guidelines allow for the termination of patients in asystole, but there are no guidelines for those who remain in PEA.

The 2015 Resuscitation Council (U.K.) guidelines state that in most circumstances where ROSC is not achieved before transport and where ALS has addressed any potentially reversible causes, there’s little to be gained from transporting the patient to a hospital.14 However, the guidelines also state, “There is limited evidence to support when one should terminate a PEA cardiac arrest… .”18

Although TOR guidelines for OHCA have been validated,5,7,8 these were produced for EMS systems different from the U.K., and they don’t necessarily reduce transportation12 or they recognize too few potential survivors19 when assessed in alternative systems.

The guideline proposed here reduced the transportation rate to 52.4%, and of the 2,264 patients for whom the CDR recommended TOR, five (0.2%) survived to hospital discharge. This compared favorably with both pre-existing guidelines. Although both of these pre-existing guidelines resulted in fewer unexpected survivors, this was at the cost of greater numbers of futile attempts being transported.


This study established clinical variables of a TOR clinical prediction rule for OHCA managed by our EMS system, to be used in conjunction with the existing rule that allows for termination following asystole after 20 minutes of ALS.

We determined, with a high rate of predictability, that adult patients suffering OHCA of presumed cardiac origin may be considered for prehospital TOR when the initial presenting rhythm was not shockable and where there is no ROSC before transport. Prospective validation of this rule would be required before its implementation.


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