Out of hospital cardiac arrest: when to resuscitate

Introduction This study explores why resuscitation is withheld when mobile emergency medical team arrive at the scene of a cardiac arrest. Methods We conducted a prospective, observational study in pre hospital emergency services. We included adults' patients, with a suspicion of non-traumatic cardiac arrest (CA) in an out of hospital environment, who received or not cardiopulmonary resuscitation (CPR) by our mobile emergency medical service teams. An analytic study was conducted in order to identify independent factors that could influence the decision to resuscitate OHCA. Results During study, 228 patients were enrolled, the mean age was 64 +/- 14 years and 59% were men. Eighteen patients (8%) received bystander CPR by witnesses. The median time elapsed to arrive at the scene was 13 [8-25] min. The median “noflow” was 22 [10-34] min. The resuscitation decision was taken by the mobile EMS staff for 106 patients (46.5%). For other patients, the decision not to resuscitate was motivated solely by the finding of a confirmed state of death in an elderly patient (p = 0.045). The predictive decision factor for resuscitation was the no flow time less than 18.5 min, Odds Ratio adjusted with 95% confidence interval to: 1.38 (1.24 - 3.55) (p <0.001). Overall out of hospital survival rate was 17% of resuscitated patients. Conclusion The decision to resuscitate a cardiac arrest outside of the hospital depends more on the “no flow” time than on the presumed etiologies.


Introduction
When cardiac arrest (CA) occurs there is sudden cessation of circulation to the brain and other vital organs. Irreversible death will occur within minutes unless circulation is restored. The technique of cardiopulmonary resuscitation (CPR) can be used to buy time whilst reversible causes of cardiac arrest are identified and treated [1]. Data indicate that CPR is only initiated or continued by mobile emergency medical service (EMS) in approximately 28,000 cases. This suggests that in more than 50%of cardiac arrests, resuscitation is withheld by mobile EMS [2]. Most out of hospital cardiac arrest (OHCA) occur in the absence of healthcare staff. Here, bystander CPR can improve survival chances by two to four folds [3,4]. Despite its lifesaving potential, circumstances exist where attempting resuscitation is inappropriate. This includes un-survivable injuries or clear evidence of death (e.g. rigor mortis, post mortem staining). Resuscitation is also withheld by mobile EMS teams when there is no prospect of success. Little is known about the characteristics of patients in whom resuscitation is withheld by mobile EMS. This study aimed to determine the reasons for resuscitating or not an OHCA by the mobile EMS teams when they arrived at the scene.

Methods
Study population: we conducted a prospective observational study over a period of two years (January 2015 to December 2016) in the pre hospital emergency department, north east of Tunisia. We included all adults patients aged more than 18 years old, with a suspicion of non-traumatic CA in an out of hospital environment, who received or not CPR by our mobile EMS teams. We excluded secondarily patients with other than CA diagnosis.

Discussion
In this study, over on in two patients (3.5%) who sustained an out of hospital cardiac arrest, resuscitation is not attempted by mobile EMS teams as the chances of survival are judged as negligible by the time of assessment. These patients are characterized by a no flow duration over 18 min when no bystander CPR is attempted such that the cardiac rhythm has degenerated to asystole. It is well known that longer mobile EMS response intervals are associated with worse outcomes after cardiac arrest. Providers who experience a longer response interval because of initial distance from the scene, poor traffic conditions may have been less inclined to attempt resuscitation on arrival because of a pessimistic outlook or a higher likelihood of the patient meeting local criteria for obvious death [5]. The decision to begin resuscitation in a patient without vital signs is a complex one faced by mobile EMS care providers in a challenging setting that may include an uncontrolled setting, emotional family members and other bystanders. It is possible that some could be saved with bystander CPR provision. For that it is extremely important to train people to be able to act when faced with a CA, as undertaking CPR, until the emergency medical service arrives, can increase the victim's chances of survival [6]. Bystander CPR is a critical step in the chain of survival, increasing the chances that a victim will survive by two to four folds, which translates to one additional life for every 30 patients who receive bystander CPR [3,4]. As the majority of OHCAs occur in the home, bystander characteristics are more important than victim factors training communities to perform CPR can increase bystander CPR rates and overall survival [7,8]. Ventricular fibrillation (VF) and ventricular tachycardia without a pulse (VT), frequently, are the rhythms found in persons with witnessed CA, as a result of which it is extremely important that both CPR and defibrillation should be undertaken at an early stage [9,10].
The chance of survival reduces by 7.0%-10.0% with each minute of delay in defibrillation, and pulseless VF/VT can deteriorate to asystole as time passes, but undertaking CPR can prolong pulseless VF/VT, thus increasing the chances of successful defibrillation [11]. A systemic review of 67 studies found the proportion of patients in whom resuscitation is attempted varies between countries from 33% to 100% [4]. In all studies, the duration of no flow period was the major determinant of prognosis [12]. To obtain maximum survival chances a delay of less than 4 min for basic CPR, less than 8 min for defibrillation and less than 12 min for advanced CPR are recommended [12,13]. Improving the prognosis of OHCA according to the chain of survival criteria involves the education of the public to shorten the duration of the no flow. The best treatment is therefore based on rapid recognition, the quality of CPR and especially prevention [14]. In our study, 17% of the resuscitated population were recovered a sinus rhythm with pulse and transferred to the emergency department but no patient came out alive from the hospital. This rate of immediate survival was lower than that identified in other studies: 22% to 33% [13,15]. To improve the prognosis of OHCA many challenges must be faced by the citizen and What is known about this topic  When cardiac arrest occurs, irreversible death will be within minutes unless circulation is restored;  The mission of emergency medical service team is to save life.
However, resuscitation attempts are not always appropriate.
Characteristics of patients in whom resuscitation is withheld by ambulance staff are not well established.

What this study adds
 This is the first Tunisian study that identifies potentially modifiable factors associated with the decision to resuscitate or not an out of hospital cardiac arrest.
Yosra Riahi contributed to data collection, Saida Zelfani analyzed the data; Saida Zelfani and Hela Manai developed the first draft of the paper which was revised by all co-authors for important intellectual content prior to final approval by all authors.