Identifying the most accurate and relevant post–cardiac arrest outcomes to measure is a major challenge that requires further research. The most used measurements are survival to hospital discharge, or neurologically intact survival to discharge. Caution is advised, for example, when considering limiting care or withdrawing life-sustaining therapy because the predictors of neurological recovery currently in use have not been validated for patients who are treated with therapeutic hypothermia.
Hollenberg et al19 conducted a study during a 14 year time period (1992-2005) in Sweden describing changes in 1-month survival in patients given CPR after OHCA. He found improved survival rates over that time period; factors that potentially contributed to the improved survival rate were an increase in emergency medical crew-witnessed cases (from 9% in 1992 to 15% in 2005 [P < 0.01]) and, to a lesser degree, an increase in bystander CPR (from 31% in 1992 to 50% in 2005 [P < 0.01]).
Hinchey et al5 did an observational multiphase before-after cohort study to assess survival from OHCA in adult patients with cardiac arrest managed by emergency responders. They concluded that in the context of a community-wide focus on resuscitation, the sequential implementation of 2005 AHA guidelines for compressions, ventilations, and induced hypothermia significantly improved survival after cardiac arrest.
Minimizing the interval between stopping chest compressions and delivering a shock (ie, minimizing the preshock pause) improves the chances of shock success and patient survival.31
Edelson et al32 did a study on internal medicine residents at a university hospital who attended weekly debriefing sessions of the prior week's resuscitations, reviewing CPR performance transcripts obtained from a CPR-sensing and feedback-enabled defibrillator. Compared with the control period, the mean (SD) ventilation rate decreased (13 /min vs 18 /min; P < 0.01) and compression depth increased (50  vs 44  mm; P < 0.01), among other CPR improvements. These changes correlated with an increase in the rate of ROSC in the RAPID (Resuscitation with Actual Performance Integrated Debriefing) group (59.4% vs 44.6%; P < 0.05). They concluded that the combination of RAPID and real-time audiovisual feedback improved CPR quality compared with the use of feedback alone and was associated with an increased rate of ROSC. Survival from cardiac arrest depends on early recognition of the event and immediate activation of emergency response system, but equally critical is the quality of CPR delivered.
Five main components of high performance CPR have been identified: chest compression fraction (proportion of time chest compressions are administered in each minute of CPR), chest compression rate, chest compression depth, chest recoil, and ventilation.33
Several devices to provide effective CPR have been the focus of recent clinical trials. To date, no adjunct has consistently been shown to be superior to standard conventional (manual) CPR for out-of-hospital BLS, and no device other than a defibrillator has consistently improved long-term survival from OHCA.
Integration of AEDs into a system of care is critical in the Chain of Survival in public places outside of hospitals. To give the victim the best chance of survival, 3 actions must occur within the first moments of a cardiac arrest: activation of the EMS system, provision of CPR, and operation of a defibrillator.7 An area of continued interest is whether delivering a longer period of CPR before defibrillation improves outcomes in cardiac arrest. Early studies showed improved survival when 1.5 to 3 minutes of CPR preceded defibrillation for patients with cardiac arrest for more than 5 minutes duration prior to EMS arrival, but more recent trials did not improved outcomes.7
Transcutaneous pacing has also been the focus of several recent trials. In the current 2010 AHA recommendations, pacing is not generally recommended for patients in asystolic cardiac arrest since randomized controlled trials indicate no improvement in rate of admission to hospital or survival to hospital discharge when pacing was attempted in patients with cardiac arrest in the prehospital or in-hospital (ED) setting.7
Medications Used During CPR
A meta-analysis of 5 randomized trials34 showed no statistically significant differences between vasopressin and epinephrine for ROSC, 24-hour survival, or survival to hospital discharge.
It is appropriate to administer a 1-mg dose of epinephrine IV/IO every 3 to 5 minutes during adult cardiac arrest or one dose of vasopressin 40 U IV/IO may replace either the first or second dose of epinephrine in the treatment of pulseless arrest.7
Therapeutic hypothermia is one intervention that has been shown to improve outcome for comatose adult victims of witnessed OHCA when the presenting rhythm was VF.28 Since 2005, nonrandomized studies with concurrent controls or historic controls have indicated the possible benefit of hypothermia following in- and out-of-hospital cardiac arrest from all other initial rhythms in adults. Holzer's study found 53% survival with favorable neurological outcome in the endovascular cooling group, compared to 34% in the control group (OR 2.15, 95% CI, 1.38 to 3.35; P < 0.05).35 Therapeutic hypothermia is a “game changer,” changing the specificity of neurological prognostication decision rules that were previously established from studies of post–cardiac arrest patients not treated with hypothermia.
Extracorporeal Membrane Oxygenation
Extracorporeal membrane oxygenation (ECMO) is a form of external cardiopulmonary life support (ECLS). Its goal is supporting the body's circulation in the absence of an adequately functioning cardiac pump. The initiation of ECLS and the management of a patient on ECLS require highly trained personnel and specialized equipment. ECLS has been associated with improved survival rates when compared with conventional CPR in patients less than 75 years old with potentially correctable conditions in case series and observational studies for in-hospital and OHCA sufferers. Although there are no randomized studies that compare ECLS with conventional CPR for patients in cardiac arrest, there are data from several case series that demonstrate the feasibility and safety of ECLS in highly specialized centers,36 but, as of this writing, there is not enough evidence to recommend the routine use of ECLS in this population.
Study by Thiagarajan37 showed that ECMO used to support CPR rescued one third of patients in whom death was otherwise certain; improved survival was found in association with patient diagnosis, absence of severe metabolic acidosis before ECMO support, and uncomplicated ECMO course.
In a study by Lamhaut L et al38 published in 2013, prehospital ECMO (PH-ECLS) was implemented by a PH-ECLS team for refractory cardiac arrest in 7 patients with a witnessed cardiac arrest, with CPR initiated within the first 5 minutes, and absence of severe comorbidities. This pilot study suggests that PH-ECLS performed by nonsurgeons is potentially safe and feasible. Further studies are needed to confirm the time saved by this strategy and its potential effect on survival.
Should resuscitative efforts be started? Ethical issues associated with CPR start with the question as to whether or not to initiate resuscitation as some patients might prefer palliative care without heroic measures to prolong life; advance directives play a very important role in these matters, and if an advance directive in the form of a living will is not available then a health care proxy or surrogate decision maker is helpful. Acknowledgment of a verbal or written do-not-attempt-resuscitation order may decrease the number of futile resuscitation attempts; however, there is insufficient evidence to support this without further validation.
When should resuscitative efforts stop? The final decision to stop resuscitative efforts often is not simple; clinical judgment and respect for patients' and their families' wishes must enter into decision making. Research addressing issues related to the appropriate termination of resuscitative efforts is limited. Goto et al39 performed a study with Japanese database on patients with OHCA. The main outcome measures were specificity, positive predictive value (PPV), and area under the receiver operating characteristic curve for the new developed termination of resuscitation (TOR) rule for emergency department physicians. They validated that the TOR rule consisting of 3 prehospital variables (no prehospital ROSC, unshockable initial rhythm, and unwitnessed by bystanders) had a more than 99% PPV of very poor outcome. However, the implementation of this new rule in other countries or EMS systems requires further validation studies.
Should family be present during CPR? Jabre P et al40 enrolled 570 relatives of patients who were in cardiac arrest and were given CPR by 15 pre-hospital EMS units that were randomly assigned either to systematically offer the family member the opportunity to observe CPR (intervention group) or to follow standard practice regarding family presence (control group). The primary end point was the proportion of relatives with post-traumatic stress disorder-related symptoms on day 90; secondary end points included the presence of anxiety and depression symptoms, the effect of family presence on medical efforts at resuscitation, the well-being of the health care team, and the occurrence of medico-legal claims. They concluded that family presence during CPR was associated with positive results on psychological variables and did not interfere with medical efforts, increase stress in the health care team, or result in medico-legal conflicts. Some other studies indicate that no clear conclusion is derived from studies done so far and more studies have to be done in this area.
Organ donation. Because of the growing need for transplant tissue and organs, all provider teams who treat postarrest patients should also plan and implement a system of tissue and organ donation that is timely, effective, and supportive of family members for that subset of patients in whom brain death is confirmed or for organ donation after cardiac arrest.