J.P.Ornato M.J.A.Parr G.D.Perkins J.Soar

 

Article Outline

The International Liaison Committee on Resuscitation (ILCOR) celebrated its 25th anniversary last year and this came at a time when the science underpinning cardiopulmonary resuscitation (CPR) continued to grow [1]. The number of submissions to Resuscitation continues to rise and the editors have highlighted some of the key papers published in the Journal in 2017.

Epidemiology and outcome

The relationship between neighbourhood socio-economic status and rates of bystander CPR was studied in Paris, France [2]. Of 4009 out-of-hospital cardiac arrest (OHCA) patients, 19.4% received bystander CPR and there were lower rates of bystander CPR in neighbourhoods with low versus higher socio-economic status (OR 0.85; 95% CI 0.72–0.99). Although similar findings have been reported from the United States (US), this was the first European study to document this association.

An analysis of the Korean nationwide OHCA registry focused on 511 OHCAs that occurred in schools [3]. The highest incidence was at a university with a large proportion of cases occurring outdoors (29.7%) or in a sports facility (30.7%). Overall survival with good neurological outcome was 19.6%.

Although an increasing number of OHCA victims survive to hospital discharge, there are few data on factors associated with longer-term survival. In an analysis of 1591(5.6%) patients who survived to hospital discharge in Canada, by one year, 12.6% of patients had died and 37.3% had been readmitted [4]. By 3 years, the mortality rate was 20% and all-cause readmission rate was 54.1%. Older age and a history of cancer were associated with higher risk of 3-year mortality. Shockable rhythm at presentation (hazard ratio [HR] 0.62, 95% CI 0.45–0.85), coronary revascularisation (HR 0.37, 95% CI 0.28–0.51) or insertion of an implantable cardioverter defibrillator (ICD) (HR 0.28, 95% CI 0.20–0.41) were associated with lower 3-year mortality. Prior cardiac conditions and other arrest characteristics were not associated with long-term mortality.

In an analysis of 13,860 patients with non-EMS witnessed OHCA in the Danish cardiac arrest registry, 25% of patients who were defibrillated by prehospital personnel were initially in a non-shockable rhythm [5]. Conversion from a non-shockable to a shockable rhythm during resuscitation was common and associated with three-fold higher odds of 30-day survival compared with sustained non-shockable rhythms. Compared with sustained non-shockable rhythms, converted shockable rhythms and initial shockable rhythms were associated with increased 30-day survival (adjusted OR 2.6, 95% CI 1.8–3.8; and OR 16.4, 95% CI 12.7–21.2, respectively).

Rapid response systems

A systematic review of outcome among adult patients attended by rapid response teams (RRT) included 29 studies and 157,383 RRT activations [6]. Limitations of medical treatment resulted from 8.1% of RRT reviews and 23% resulted in a transfer to an intensive care unit (ICU). Of patients transferred to an ICU, 29% died during that admission. The median hospital mortality was 26%, and the median 30-day mortality rate was 29%.

The frequency of medical emergency team (MET) activation before paediatric CPR was evaluated using the Get-With-The-Guidelines-Resuscitation (GWTG-R) registry (2007–2013) [7]. Of 215 children from 23 hospitals requiring CPR for bradycardia or cardiac arrest, 48 (22.3%) had a preceding MET evaluation. Children with a MET evaluation before CPR were older and were more likely to have metabolic/electrolyte abnormalities, sepsis, or malignancy. Among patients who did not have a MET called and with information on vital signs, 55/141 (39.0%) had at least one abnormal vital sign that could have triggered a MET call, demonstrating opportunity for more use of MET teams.

An interrupted time series study analysed the trajectories of monthly complication rates for 4.69 million patients in 218 hospitals in Victoria, Australia following the introduction of a national standard for recognising deteriorating patients [8]. This initiative was associated with a reduction in the rates of in-hospital cardiac arrests (IHCAs) and acute coronary syndromes (ACS) in acute hospitals. Greatest benefit was seen in the elderly, female and surgical patients. This is the second large jurisdictional study from Australia to demonstrate benefit of system-wide introduction of a rapid response system [9].

Basic life support

2017 Saw the first output from the ILCOR transition to continuous evidence evaluation [10]. Working with knowledge synthesis experts from Li Ka Shing Knowledge Institute, St. Michael’s Hospital, content experts from ILCOR reviewed the science relating to the effectiveness of different compression to ventilation methods for cardiac arrest [11]. The review synthesised evidence relating to dispatcher-assisted CPR and compression to ventilation ratios for bystanders. The summaries of these findings were then considered by the ILCOR BLS/AED and Paediatric Task Forces. These led to the publication of 6 consensus on science and treatment recommendations on the ILCOR website (www.ilcor.org) which were published in the annual summary presented in Resuscitation [12] and Circulation [13]. The recommendations from ILCOR have been incorporated in to the 2017 update of the European Resuscitation Council Guidelines for CPR [14].

High quality cardiopulmonary resuscitation

High-quality CPR remains a central tenet of effective resuscitation. An observational study from Denmark which captured CPR quality data from an AED which provided audio-feedback found that bystanders delivered moderate to good quality CPR. This provides real world data about the potential benefits of CPR feedback and prompt devices [15]. There was nevertheless scope for improving chest compression depth and minimising pauses in chest compressions.

Amongst 6475 bystander witnessed victims of OHCA in Korea, a higher proportion survived if they received bystander CPR from dedicated trained responders rather than lay person bystanders (adjusted OR 1.59(1.20–2.11)). In Sweden, bystander-witnessed OHCA victims who received initial CPR from off-duty medically-educated personnel, had better outcomes than those receiving bystander CPR from laypersons.[Nord 2017,88] Whilst receiving bystander CPR in itself remains critically important to outcome from OHCA [16,17], these data highlight the importance of CPR training for delivering the best outcomes.

Defibrillation

An analysis of 19519 ventricular fibrillation/pulseless ventricular tachycardia (VF/pVT) patients in the Swedish OHCA registry (1990–2015) found that 30-day survival decreased with more shocks regardless of witnessed status and the time period [18]. Factors associated with an increased 30-day survival included CPR before arrival of EMS, female sex, cardiac cause and year of OHCA (increasing survival over years).

The interaction between the defibrillation waveform (mono– vs bi–phasic) and time to defibrillation was investigated among 71566 patients in the all-Japan OHCA registry [19]. For both biphasic and monophasic defibrillation, the delivery of more shocks was associated with a decreased rate of return of spontaneous circulation (ROSC) in the field. However, an increased number of biphasic-only defibrillation shocks improved the one-month CPC (1, 2) survival rate. The authors concluded that a biphasic waveform has a more favourable effect on long-term survival than a monophasic waveform when ?2 defibrillations are delivered.

Recent non-randomised case series in patients with refractory VF suggest benefit from delivering two shocks in rapid succession (termed double sequential defibrillation, or ‘DSD’). A retrospective, observational analysis of London Ambulance Service patients with VF refractory to ?6 standard shocks compared the outcome of those who subsequently received DSD versus continued single shocks [20]. During the 18-month study period, 45 patients were treated with DSD: a third obtained pre-hospital ROSC and 7% survived to hospital discharge. Similar ROSC and survival rates were observed in those who received exclusively standard defibrillation, leading the authors to conclude there was no clear benefit from DSD use by EMS in the treatment of refractory VF.

Major regional discrepancies in both AED density and survival were documented in an analysis of data from 51 French districts (29.3 million inhabitants) [21]. Mean survival rate was two-fold higher with AED density above the median (7.9% versus 17.8%, P?<?0.001) and four-fold higher with BLS-education above the median (5.0% versus 20.9%, P?<?0.001). However, only the rate of population BLS education remained independently associated with survival (OR 1.64, 95% CI 1.17–2.31; P?=?0.0045). The authors concluded that population BLS education provides an important benefit regardless of the density of AEDs in a community.

Can drones carrying AEDs improve survival from OHCA? They are easily deployed and fast, and have a relatively low operational cost but barriers to their widespread deployment remain [22].

Advanced life support

Airways, ventilation and waveform capnography

There was little new about how we should manage the airway in 2017 and the optimal strategy for airway management during CPR remains a stepwise approach that is based on patient factors, and the skills of the rescuer [23,24]. There is increasing interest in the use of videolaryngoscopy for tracheal intubation during cardiac arrest. An analysis of two Japanese multicentre prospective observational studies between 2010 and 2016 that included 10, 927 emergency department intubations (4426 for cardiac arrest) observed that videolaryngoscopy was used for 2% of intubation attempts in 2010 and 40% in 2016 [25]. The first attempt success rate increased from 68% in 2010 to 74% in 2016 (P_trend?=?0.02). A small (82 intubations) pilot RCT of video (King videolaryngoscope) versus direct laryngoscopy for intubation by paramedics in OHCA reported similar first attempt and overall success rates with both techniques [26]. Once a tracheal tube is placed, the recommended ventilation rate is 10?min^?1 without interrupting chest compressions. A systematic review identified very low-quality evidence to support this recommendation [27]. Low ventilation rates are likely to be sufficient to maintain an adequate ventilation to perfusion ratio during CPR as the cardiac output generated during CPR is also markedly reduced. Finally, if all else fails, reassuringly, eight out of 10 inexperienced rescuers were able to insert an emergency cricothyroidotomy on a fresh cadaver using a pocket knife and a ballpoint pen [28].

Waveform capnography to confirm tracheal tube position in all patients who are intubated during CPR is now widely accepted and part of current guidelines [23]. Two studies looked at whether ventilation rate could be accurately measured with waveform capnography in the presence of chest compression artefact: one study reported that its algorithm performed well with an error of below 1.8?min^?1 [29], whereas the other reported that 42% of waveforms were distorted and errors in the ventilation rate were as high as 50% [30]. An observational study of 207 defibrillation attempts in 62 patients documented that all defibrillation attempts were successful when the mean end-tidal carbon dioxide (ETCO₂) value was greater than 45?mmHg in the minute preceding the shock, and no shock was successful when this value was less than 7?mmHg [31]. Defibrillation was defined as effective if VF/pVT was terminated with a subsequent organised rhythm within 60?s. If, as is thought likely, that high-quality CPR increases end-tidal carbon dioxide values, this study supports the previous observations that high-quality CPR preceding a shock improves defibrillation shock success [32].

Drugs during CPR

The evidence for any drug therapy during CPR remains uncertain. A systematic review and network meta-analysis comparing the effectiveness of antiarrhythmic drugs for OHCA identified 8 RCTs involving 4464 patients [33]. The analysis found that amiodarone and lidocaine were associated with improved survival to hospital admission but for important patient outcomes such as survival to hospital discharge and neurologically intact survival, no antiarrhythmic was better than any other or than placebo.

A retrospective cohort study of 1525 individuals treated with intravenous (IV) drugs and 275 with tibial intra-osseous (IO) drugs during CPR for OHCA reported that, after risk adjustment, IO treatment was associated with lower ROSC (OR?=?0.67, 95% CI 0.50–0.88) and lower survival to hospital admission (OR?=?0.67, 95% CI 0.51–0.91) [34]. Whether other IO sites (humeral or sternal) would have similar outcomes is unknown.

Sodium bicarbonate is still used by many during CPR. Observational OHCA data from Canada between 2005 and 2016 identified that 5165 (37.3%) out of 13865 patients had been given sodium bicarbonate [35]. In a 1:1 propensity matching cohort of 5638 patients, sodium bicarbonate was associated with worse survival to discharge (adjusted OR 0.64, 95% CI 0.45–0.91) and worse neurological outcome at discharge (adjusted OR 0.59, 95% CI 0.39–0.88).

Mechanical devices

An analysis of the Swedish cardiac arrest registry noted marked variation in the use of mechanical chest compression devices, ranging from 0.8% to 79% (average 32%) amongst 24,316 patients treated for OHCA [36]. Unadjusted 30-day survival was 6.3%. Adjusted odds ratio for 30-day survival in the group receiving mechanical CPR was 0.72 (95% CI 0.62–0.84).

The PARAMEDIC cluster randomised trial of the LUCAS mechanical device reported similar survival but worse neurological outcomes in patients allocated to receive mechanical CPR (6% versus 7%, adjusted odds ratio 0·86, 95% CI 0·64–1·15) [37]. In a follow-up study, twelve months after cardiac arrest there was no difference in generic health-related quality of life measures (SF-12 and EQ-5D), emotional wellbeing (HADS and PTSD-CL) [38]. Cognitive function, measured by MMSE, was statistically lower in the LUCAS arm (26.9 versus 28.0 (adjusted mean difference ?1.5 (95% CI ?2.6 to ?0.4)), but the difference was smaller than the amount considered to be a clinically important difference. A within trial cost effectiveness analysis, based on quality adjusted life years (derived from EQ-5D-3L), assessed at 12 months and extrapolated to the lifetime horizon reported that mechanical CPR represented poor value for money compared to standard chest compressions [39].

The LUCAS IN Cardiac arrest (LINC) investigators presented a post hoc analysis of outcomes in patients in initially shockable rhythms [40]. The rationale for this analysis was the finding in the PARAMEDIC trial that outcomes were worse in the group receiving mechanical chest compressions. The two trial protocols differed – in LINC, patients received an initial shock before rhythm analysis and received chest compressions for 3?min cycles. In PARAMEDIC, the first shock was delayed until after initiation of mechanical CPR and chest compression cycles were of 2?min duration. The LINC analysis found no difference in the rate of ROSC, survival or neurological outcomes, despite a slight (1?min on average) delay in the initiation of first shock in the mechanical CPR group…

ARTÍCULO COMPLETO