Resuscitation highlights in 2015

RESUSCITATION JOURNAL COVER

Resuscitation highlights in 2015

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

 

The 2015 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations (CoSTR) and the 2015 European Resuscitation Council (ERC) Guidelines were just some of the landmark publications in Resuscitation last year.,  The editors have highlighted some of the other key papers that helped to further resuscitation science in 2015.

1. Epidemiology and outcome

The Utstein-style template for reporting outcomes from out-of-hospital cardiac arrest (OHCA) has been revised and updated. This template facilitates reporting of the bystander-witnessed, shockable rhythm as a measure of emergency medical services (EMS) system efficacy and all EMS system-treated arrests as a measure of system effectiveness. Several additional important subgroups are identified that enable an estimate of the specific contribution of rhythm and bystander actions that are key determinants of outcome.

Several recent studies have indicated that survival rates for OHCA are slowly increasing. An analysis of the Resuscitation Outcomes Consortium study sites showed that unadjusted survival rates for 47,148 EMS-treated OHCA cases increased from 8.2% in 2006 to 10.4% in 2010. In a sub-analysis of 111 U.S. and Canadian hospitals participating in the ROC-PRIMED study during 2007–2009, greater survival and favourable neurological status at discharge were associated with greater adherence to recommended hospital based post-resuscitative care guidelines.

Four studies published in 2015 focussed on outcomes after cardiac arrest in the elderly., , ,  Two studies documented an association between age and neurological outcome,  but two others found no such association., 

In a study of seven North American cities, Pittsburgh had the highest crude rate of cardiac arrest deaths in patients 18–64 years of age, particularly in neighbourhoods with lower socioeconomic status (SES). The authors retrospectively identified 415 patients aged 18–64 years treated for OHCA and in-hospital cardiac arrest (IHCA) at two Pittsburgh hospitals between January 2010 and July 2012. Socioeconomic factors strongly influenced the type, severity, and outcome of patients with OHCA but not those with IHCA.

The prognostic value of pregnancy in women receiving CPR in the emergency department was evaluated in a population-based, matched cohort study using the Nationwide Emergency Department Sample (NEDS) from 2006 to 2010. The authors identified 157 pregnant women among 8162 women requiring CPR in the emergency department. Pregnancy was associated with better overall survival of 36.9% compared to 25.9% in non-pregnant women (OR 1.89 [1.32–2.70], p?<?0.01). Traumatic injury was identified as a significant predictor of outcome in pregnancy. In non-trauma patients, pregnant women had significantly better odds of surviving CPR than non-pregnant women (OR 2.10 [1.41–3.13], p?<?0.01). In cases of trauma, no significant difference was observed between groups.

Nehme and co-authors used data from the Victorian Ambulance Cardiac Arrest Registry to compare epidemiology, survival to hospital discharge and 12-month functional recovery in 8648 adult OHCAs occurring before and after paramedic arrival. When compared to OHCA cases occurring before EMS arrival, EMS-witnessed arrests were associated with significantly higher survival to hospital discharge rates and favourable neurological recovery at 12-month post-arrest.

In a summary of nine studies included in a systematic review of OHCA in schools, it was confirmed that OHCA in children and adolescents is rare, with a minority of cases occurring at school. However, when cardiac arrests occur on school property, it is more likely to affect an adult than a student. Outcomes are better than for arrests occurring at other out-of-hospital locations, probably due to the high proportion of witnessed arrests and high rates of bystander CPR.

Does the number of EMS personnel on scene affect cardiac arrest outcome? In a retrospective review of 16,122 EMS-treated OHCAs from Canada and the United States, the presence of 5 or 6, 7 or 8 EMS personnel on-scene was associated with a higher rate of survival to hospital discharge compared with fewer personnel on-scene (adjusted odds ratio 1.35 [95% CI: 1.05, 1.73]). The authors concluded that more EMS personnel on-scene within 15?min of a 911 call is associated with improved survival from OHCA.

2. Rapid response systems

The publication of advanced life support (ALS) treatment recommendations in the 2015 CoSTR and 2015 guidelines by the ERC included continuing emphasis on the need for rapid response systems (RRS) of care to identify the deteriorating patient and prevent IHCA.,  Resuscitation continues to publish important studies that aim to improve our understanding of RRS.

Jarvis and colleagues assessed the Royal College of Physicians of London (RCPL) National Early Warning Score (NEWS) system and compared workloads generated by the RCPL’s escalation protocol with those for aggregate NEWS values alone. The recommended NEWS escalation protocol produced additional work for the bedside nurse and responding doctor, disproportionate to the benefit in increased detection of adverse outcomes. Efficient staff resource allocation and avoiding alarm fatigue will be increasingly important to optimise RRS in evolution.

The performance of the NEWS in identifying 48?h and 30 day mortality, intensive care unit (ICU) admission, and a combined endpoint of 48?h mortality or ICU admission was evaluated in unselected prehospital patients. All the endpoints were associated with higher NEWS scores and they concluded that calculation of prehospital NEWS may facilitate earlier recognition of deteriorating patients, and the early involvement of senior emergency department staff.

Abbott and colleagues conducted a prospective observational cohort study of all adult general medical patients admitted to a single hospital over a 20-day period. They aimed to compare the newly introduced NEWS to the early warning score currently used – the Patient at Risk Score (PARS). Physiological data and early warning scores recorded in bedside charts were collected on admission and a NEWS score was retrospectively calculated. The primary outcome was a composite of critical care admission or death within 2 days of admission. The secondary outcome was hospital length of stay. NEWS was more strongly associated with the primary outcome than PARS, and a NEWS of 3 or more was associated with the primary outcome (odds ratio 7.03, p?=?0.003). Neither score was correlated with hospital length of stay. They suggested that current guidelines advocating a threshold of 5 for triggering a clinical review should be reviewed since a score of 3 or more was associated with a poor outcome. Both scores were poor predictors of hospital length of stay.

To add weight to this suggestion a further study evaluated the weightings and calculations used for early warning scores (EWS) where calculation errors may potentially impact on hospital efficiency and patient care.They truncated 36 published ‘standard’ EWSs so that, for each component, only two scores were possible: 0 when the standard EWS scored 0 and 1 when the standard EWS scored greater than 0. They found that binary EWSs had lower Area under the Receiver Operating Characteristics (AUROCs) than the standard EWSs in most cases, although for some the difference was not significant. The binary form of the NEWS, had significantly better discrimination than all standard EWSs, except for NEWS. Overall, Binary NEWS at a trigger value of 3 would detect as many adverse outcomes as are detected by NEWS using a trigger of 5, but would require a 15% higher triggering rate. The balance between fewer errors and a potentially greater workload needs further investigation.

Capan and colleagues studied optimal patient-centred rapid response team (RRT) activation rules using electronic medical records (EMR)-derived Markovian models. NEWS was used and statistical tests identified 12 statistically significant subpopulations which differed clinically, as measured by length of stay and time to re-admission. They suggest the full potential of EWS for personalising acute care delivery is yet to be realised.

3. Basic life support

Delivering high-quality CPR to all victims of cardiac arrest remains a key priority identified by the ILCOR review of science and treatment recommendations and ERC Guidelines Despite clear evidence of benefit from bystander CPR, the rates of bystander CPR remain sub-optimal in many communities.

In 2015 the World Health Organization endorsed the “Kids save lives” campaign which promotes CPR in schools. This strategy is logical as school children are a captive audience, training is more efficient, eager to learn and the future generation of adults. The timing of what to teach and when in the school curriculum is assisted by the findings from a systematic review by De Buck et al. Evidence from 30 studies showed that children as young as 5 can learn some skills and those over 11 are likely to help in an emergency. An evidence-based educational pathway for CPR and first aid for different age groups is presented.

4. Defibrillation

The issue of whether it is safe to defibrillate when properly-gloved rescuer hands are touching the patient sparked considerable interest and discussion in 2015., , ,  The ability of electrical insulating gloves to protect the rescuer during hands-on defibrillation was tested using a ‘worst case’ electrical scenario. Data from 61 shocks applied to 43 different patients were recorded. Rescuer leakage current was significantly below the 1?mA safe threshold, enabling the authors to conclude that hands-on defibrillation is safe if the rescuer makes only one other point of contact with the patient and uses Class 1 electrical insulating gloves.

Public access defibrillation (PAD) deployment rates remain low: 1% in Asia, 3.8% in Copenhagen, and 16% in Stockholm. An analysis of the cost effectiveness of PAD programmes and other studies suggests cost effectiveness would be improved by identifying locations with the highest incidence of OHCA and investing in interventions to increase AED utilisation., , 

For example, there is a volunteer-based automated external defibrillator (AED) network in Copenhagen which provided a unique opportunity to assess AED use. Investigators found that an AED was applied before ambulance arrival in only 3.8% of all OHCA cases even though 15.1% of all events occurred within 100?m of an accessible AED.

In contrast, in a retrospective analysis of OHCAs from 2006-12 in Stockholm, one-month survival was 31% (n?=?101) for cases defibrillated by the EMS, 42% (n?=?22) when defibrillated by first responders, and 70% (n?=?52) when defibrillated by a public AED. AEDs within the PAD programme constituted 2.6% of all public AEDs and were used in 28% (n?=?21) of cases when a public AED was used.

A critical determinant of whether PAD programmes are successful hinges on matching deployed AED location with where cardiac arrests are likely to occur in the community. The location of 654 OHCAs were compared with 1704 non-medically placed AEDs in metropolitan Phoenix, Arizona during 2010–12. Events occurred most frequently at locations categorised as ‘In Cars/Roads/Parking lots’ (190/654, 29.1%) and there were no identified AEDs for these areas. AEDs were placed most frequently in ‘Public business/office/workplace’ locations and cardiac arrests occurred with the second highest frequency in this location type. The authors found only a weak correlation between events and deployed AEDs even though it was possible to identify areas where OHCAs occurred frequently.

Public use of AEDs also depends on their knowledge of the devices and willingness to use them. A survey of 514 bystanders in two high-volume train stations in Philadelphia, Pennsylvania found that 66% were able to correctly identify an AED and its purpose, and 58% reported willingness to use an AED in an emergency.However, less than 10% of respondents presented with a hypothetical cardiac arrest scenario spontaneously mentioned using an AED when asked what actions they would take.

Mobile phone technology can link incident location, nearest PAD and a nearby first responder. One system, Pulsepoint, has been deployed to over 600 communities in the US. A user survey found 63% (n?=?813) had received a notification of a nearby suspected cardiac arrest, of whom 189 (23%) had responded. Of those who did respond, one third did not make it to the scene of the incident. 44 (32%) found a victim who was unconscious and not breathing normally and CPR was provided in 11 cases.

Many rescuers have wondered why resuscitation guidelines recommend resuming chest compressions for 2?min after defibrillation before checking for a pulse or analysing the rhythm. An analysis of 372 defibrillation attempts in 176 patients in the Resuscitation Outcomes Consortium (ROC) database documented 182 episodes of post-shock asystole. The mean interval of asystole after defibrillation was 69?±?136?s (median 20?s; IQR 36) and the mean interval for return of an organised rhythm was 64?±?157?s (median 7?s; IQR 26). The mean time to return of spontaneous circulation (ROSC) was 280?±?320?s (median 136?s; IQR 445). The authors concluded that the majority of patients remain pulseless for over 2?min after defibrillation and the duration of asystole before return of pulses is longer than 120?s beyond the shock gap in as many as 25%. Their data support the recommendation to resume chest compressions for 2?min immediately following attempted defibrillation.

5. Advanced life support

5.1. Airways

A stepwise approach to airway management during CPR and after ROSC that is based on patient factors, the stage in the resuscitation process (during CPR or after ROSC) and the skills of the rescuer was recommended by the European Resuscitation Council in 2015 based on the ILCOR CoSTR.,  The ILCOR ALS CoSTR systematic review comparing tracheal intubation and supraglottic airways (SGAs) did not include a meta-analysis based on the identified studies. The ERC 2015 guidelines recommend that in the absence of personnel skilled in tracheal intubation, a SGA (e.g. laryngeal mask airway, laryngeal tube or i-gel) is an acceptable alternative. However, a systematic review that included a meta-analysis of studies comparing tracheal intubation and SGAs identified 10 observational studies with 34,533 intubated patients and 41,116 SGA patients. Tracheal intubation was associated with higher odds of ROSC (odds ratio [OR] 1.28, 95% confidence interval [CI] 1.05–1.55), survival to hospital admission (OR 1.34, CI 1.03–1.75), and neurologically intact survival (OR 1.33, CI 1.09–1.61). Although the numbers are impressive, as the authors state, meta-analyses cannot overcome the inherent limitations of observational studies. A conceptual model identifies potential mechanisms linking advanced airway management with OHCA outcomes. Hopefully the results from two large RCTs [AIRWAY 2 [ISRCTN 08256118] and PART [NCT02419573]) will help answer the question of which advanced airway technique is best during CPR.

Videolaryngoscopy can help improve the view of the larynx at intubation. An observational study of IHCAs compared videolaryngoscopy in 121 patients (52.8%) with direct laryngoscopy in 108 patients (47.2%). First attempt success was higher with videolaryngoscopy (71.9%; 87/121) than with direct laryngoscopy (52.8%; 57/108; p?=?0.003). Another study of tracheal intubation by novice emergency physicians of OHCA patients arriving in the emergency department described first attempt success rate after a phase when direct laryngoscopy was used and compared this with a phase when video laryngoscopy was used. First attempt success (n?=?49) was higher with video laryngoscopy compared with direct laryngoscopy (n?=?34, 91.8% vs. 55.9%; p?<?0.001), time for insertion was shorter (37 [29–55] vs. 62 [56–110]?s; p?<?0.001), oesophageal intubation occurred only with direct laryngoscopy (n?=?6, 17.6%), and the median duration of chest compression interruption was shorter (0 [0–0] vs. 7 [3–6]?s). The use of videolaryngoscopes is increasing despite the lack of RCTs.

Waveform capnography should be used to confirm tracheal tube position in all patients who are intubated, including during CPR. It is disappointing therefore that a recent UK survey showed that most hospitals (67%) did not have the capability to measure end-tidal carbon dioxide on general wards when required during a resuscitation attempt. Finally, a systematic review showed that the use of ultrasound by trained rescuers could also be used to reliably detect the position of the tracheal tube in the trachea, and also assess for bilateral lung movement during subsequent ventilation. Despite this, waveform capnography remains the recommended technique during CPR, as in addition to confirming tracheal tube placement, waveform capnography has a role in detecting ventilation rate, assessing CPR quality, identify ROSC, and may have a role in prognostication when ROSC has not been achieved.

5.2. Vasopressors

The role of vasopressors during CPR is uncertain. Although adrenaline can improve the rate of ROSC, its effect on longer-term outcomes is uncertain.,  The timing of adrenaline during CPR may also effect its efficacy. Observational US statewide data analysed from 3469 patients with witnessed OHCA showed survival to hospital discharge was greatest when adrenaline was injected very early but decreased rapidly with increasing time to adrenaline administration; odds ratio 0.94 (95% CI 0.92–0.97) but timing of adrenaline had no significant effect on good neurological outcome (OR?=?0.96, 95% CI?=?0.90–1.02). When interpreting this observational data, it is important to remember that in a large randomised controlled trial (RCT) of amiodarone, early placebo was associated with a better outcome than later placebo. The results of a large ongoing UK RCT of adrenaline and placebo for OHCA may shed further light on the role of adrenaline in cardiac arrest (PARAMEDIC 2 [ISRCTN73485024]).

5.3. Mechanical CPR

A systematic review of randomised trials of mechanical chest compression devices found no advantage to the routine use of mechanical chest compression devices for OHCA (survival to discharge/30 days (average odds ratio (OR) 0.89, 95% CI 0.77, 1.02) and survival with good neurological outcome (average OR 0.76, 95% CI 0.53, 1.11). Per-protocol analysis of the LINC trial observed similar four-hour survival rates between mechanical and manual CPR (23.8% vs. 23.5%, risk difference ?0.35%, 95% CI ?3.1 to 3.8, p?=?0.85). By contrast a prospective evaluation of mechanical CPR in Vienna noted worse neurological outcomes in those receiving mechanical CPR. These findings reinforce the ILCOR and ERC recommendations against their routine use., 

Mechanical CPR should still be considered where manual CPR is not possible or difficult. Using defibrillator downloads and pre-hospital video footage one study concluded that a carry sheet and mechanical CPR device could maintain high-quality CPR during transfer from the scene to the back of an ambulance.

5.4. Extracorporeal CPR (ECPR)

Extracorporeal CPR (ECPR) can provide an artificial circulation and vital organ perfusion, and increase the time window for achieving ROSC and identifying and treating a reversible underlying cause. The 2015 ERC Guidelines include considering the use of ECPR in specific circumstances. Resuscitation continues to publish observational data showing that ECPR is feasible for both IHCA and OHCA in selected populations. This had led to a call that ethical challenges are addressed as ECPR use increases, and that there is a need for outcomes registries and randomised trials, and the development of fair and transparent appropriate use criteria informed by economic analyses. The CHEER study (mechanical CPR, Hypothermia, ECMO and Early Reperfusion) enrolled 26 patients with refractory cardiac arrest (15 IHCA, 11 OHCA). It showed that mechanical CPR, rapid intravenous administration of 30?mL/kg of ice-cold saline to induce intra-arrest therapeutic hypothermia, percutaneous cannulation of the femoral artery and vein by critical care physicians and veno-arterial extra-corporeal membrane oxygenation (ECMO) was feasible with 14/26 (54%) survival do hospital discharge with good neurological outcome. These good outcomes in select patients mainly with an acute coronary syndrome, should be tempered by reports of relatively poor outcomes with ECPR in adult patients after drowning (see below).

5.5. Monitoring during CPR

The 2015 ERC ALS Guidelines include a specific section on monitoring during CPR. This is based on the premise that clinical and physiological measures during CPR will help tailor resuscitation interventions and improve outcomes. The ILCOR CoSTR found little in the way of studies in this area.

The presence and significance of clinical signs during CPR is poorly understood. Early high-quality CPR after the heart stops can lead to a return of signs of life even though there is no spontaneous circulation. A systematic review showed that consciousness can return during CPR, in particular when mechanical devices are used and there is a high mean arterial pressure. A study of continuous invasive arterial blood pressure monitoring during CPR in 104 patients found deeper compression depth was weakly associated with higher blood pressure values but there was substantial variation between individuals, and not all patients had an increased blood pressure with an increased compression depth. The authors suggest continuous arterial monitoring when it is available could be used to target specific diastolic and systolic blood pressure targets during CPR and the optimal chest compression rate and depth to achieve these pressures could vary between individuals. Another study showed that it was feasible to measure common carotid artery blood flow during CPR using carotid Doppler scans. The usefulness of the carotid blood flow values measured to guide interventions during CPR and improve outcomes is not known.

The use of ultrasound during CPR by trained rescuers can help detect and thus allowing treatment of reversible causes of cardiac arrest. A study of transthoracic echocardiography during CPR in 49 intensive care unit patients showed that 17 (34.7%) were in asystole and in the 32 (65.3%) with PEA, 27 (55.1%) had mechanical activity. This group with mechanical activity (‘pseudo PEA’) had a much higher rate of ROSC and survival to discharge than the other groups.

Waveform capnography is recommended during CPR when the trachea is intubated. An end-tidal CO2waveform may also be generated when using a SGA during CPR. A large multicentre observational study of 583 in- and out-of hospital cardiac arrest attempted to quantify the relationship between the end-tidal CO2values and CPR interventions. Every 10?mm increase in chest compression depth increased the end-tidal CO2 by 1.4?mmHg [0.18?kPa] (p?<?.001). For every 10?min?1 increase in ventilation rate, end-tidal CO2decreased by 3.0?mmHg [0.4?kPa] (p?<?.001). Compression rate did not predict end-tidal CO2. Case-averaged end-tidal CO2 values were higher in patients with ROSC (34.5?±?4.5 vs. 23.1?±?12.9?mmHg, p?<?.001). A study of IHCA in 50 patients with PEA showed an initial end-tidal CO2 value greater than 20?mm Hg [2.7?kPa] was associated with increased ROSC. These studies show that waveform capnography does have a role in guiding therapy during CPR. The ILCOR CoSTR cautioned against using end-tidal CO2 values alone in making decisions during CPR as there remain substantial gaps in our knowledge.

Cerebral oximetry is an emerging and feasible monitoring technology for use during CPR and after ROSC. Cerebral oximetry uses near-infrared spectrometry technology to non-invasively monitor regional cerebral oxygen saturation (rSO2) in superficial brain cortex regions. A systematic review and meta-analysis of observational data identified nine studies with 315 patients (119 achieving ROSC, 37.7%). The meta-analysis showed that higher initial and average rSO2 values were associated with ROSC. In two Japanese studies, regional cerebral oxygen saturation (rSO2) was measured in patients admitted to hospital following OHCA; some of these had achieved ROSC prehospital.,  A receiver operating characteristic curve analysis indicated an optimal rSO2 cut-off of ?40% for good neurological outcome (area under the curve 0.92, sensitivity 0.81, specificity 0.96). There remain considerable gaps in our knowledge concerning rSO2 values and further research is needed.

6. Trauma and hypothermia

A study documented outcome among 43 patients with refractory hypothermic cardiac arrest caused by drowning in the River Seine who were considered for treatment with extracorporeal life support (ECLS). Only 4 of the 20 patients treated with ECLS survived more than 24?h and only 2 survived to ICU discharge and 6-months. Another study from France explored factors associated with outcome after accidental deep hypothermia (core temperature <28?°C). Forty-eight patients were included and the cause of hypothermia was exposure to a cold environment (n?=?27), avalanche (n?=?13) or immersion in cold water (n?=?8). Thirty-two patients had a cardiac arrest (CA) and ECLS was implemented in 21 patients with refractory cardiac arrest and in two patients with haemodynamic instability. Overall mortality was 50%. Only three out of 15 patients with unwitnessed cardiac arrest survived at day 28, whereas eight out of 17 patients with witnessed collapse survived. They concluded that cardiac arrest related to rescue collapse was associated with favourable outcome. On-scene rescue collapse should prompt prolonged resuscitation and ECLS rewarming in all CA patients with deep hypothermia. Conversely, unwitnessed cardiac arrest was associated with unfavourable outcome and will likely not benefit from ECLS.

One study documented the echocardiographic findings in patients with hanging injury and showed varying degrees of left ventricular systolic dysfunction. Helm and colleagues reported their first 3-year experience in the use of intraosseous (IO) access in the German Helicopter Emergency Medical Service (HEMS). Their IO usage rate was low with a high success rate, and was more commonly used as a first line strategy in children <7 years, in trauma cases and in cardiac arrest. Qasim and colleagues reviewed the evolving role of resuscitative endovascular balloon occlusion of the aorta (REBOA) in the management of non-compressible torso haemorrhage. REBOA can be deployed at the bedside in the emergency department. Its use in the context of available evidence needs robust systems including training, accreditation, multidisciplinary involvement and quality assurance.

7. Post-resuscitation care

7.1. Post-cardiac arrest syndrome

In a small sub-analysis of the Targeted Temperature Management (TTM) trial, sublingual microvascular flow index (MFI) was assessed using side stream darkfield imaging and vascular reactivity measured at the thenar region of the hand by near infrared spectroscopy in 22 OHCA patients. The authors documented significant abnormalities in microvascular flow but there were no significant differences between the 33?°C and 36?°C groups.

Early-onset pneumonia occurs in approximately two-thirds of OHCA survivors and yet current guidelines do not include a recommendation to give antibiotics prophylactically. In a retrospective study of the Northern Hypothermia Network registry, 416 (34%) of 1240 patients received prophylactic antibiotics and this intervention was associated with a reduced incidence of pneumonia but a similar rate of good functional outcome.

7.2. Targeted temperature management

The relationship between time to target temperature and outcome is complex. In a retrospective, single centre study, 56 patients who were surface cooled prehospital achieved target temperature (<34?°C) faster than a group of 54 patients who were not cooled until arrival at hospital.

In a study of 321 post-cardiac arrest arrests who were cooled in hospital a shorter time to target temperature was associated with a poor neurological outcome. The authors hypothesise that more extensive neurological injury causes greater impairment of thermoregulatory control.

In an observational study of 11,158 patients admitted to hospital after OHCA in Korea, those treated with mild therapeutic hypothermia achieved a better neurological outcome than those who were not cooled. After analysis using multivariable logistic regression, mild hypothermia was associated with better outcome for those patients achieving ROSC in the emergency department but not for those who achieved ROSC prehospital.

Many clinicians continue temperature control systems to enable strict normotheria to be maintained after the first 24?h at target temperature and this is partly because some studies have shown an association between post rewarming hyperthermia and poor outcome. In a study that challenges this hypothesis, the occurrence of post-rewarming fever among 277 cardiac arrest survivors was associated with favourable neurological outcome.

Outcome following asphyxial cardiac arrest is generally very poor and it is unknown whether these patients benefit from TTM. In a study from Korea, 52 (47%) of 111 patients who received TTM (32–34?°C) after asphyxial cardiac arrest (excluding those caused by hanging or drowning) survived but only 6 (5%) had a good neurological outcome (Cerebral Performance Category (CPC) 1–2). Among 178 comatose survivors of OHCA who had initial non-shockable rhythms and who were enrolled in the TTM trial, rates of good neurological outcome were similarly low in the 33?°C (13%) and the 36?°C (15%) groups.

The impact of temperature variability on outcome after cardiac arrest is unknown. Among 229 comatose survivors treated with TTM after cardiac arrest, 25% of patients had high temperature variability (defined as a standard deviation >1?°C); however, this was not associated with a worse neurologic outcome.

Mild hypothermia is generally thought to impair blood clotting; however, in a sub-analysis of 171 patients enrolled into the TTM trial, there was no difference in standard clotting tests or thromboelastography (TEG) values between the 33?°C and the 36?°C groups. Mild hypothermia is know to cause bradycardia but some post-cardiac arrest studies have shown an association between bradycardia and a good outcome. Investigators from Copenhagen have now also documented this phenomenon. Among 234 OHCA survivors who underwent TTM, those developing sinus bradycardia (<50?beats?min?1) had lower odds of unfavourable outcome (ORunadjusted?=?0.42 (0.23–0.75, p?<?0.01).

7.3. Haemodynamic management

The optimal target blood pressure for comatose cardiac arrest survivors is unknown. In an observational study of 188 post-cardiac arrest patients treated with TTM a higher achieved mean arterial blood pressure was not associated with good neurological survival. In another observational study of 82 post-cardiac arrest patients monitored with near-infrared spectroscopy (NIRS), a mean arterial blood pressure (MAP) range of 76–86?mmHg was associated with maximal survival but optimal cerebral oxygen saturation was associated with a higher MAP of 87–101?mmHg.

It is known that some post-cardiac arrest patients exhibit evidence of disturbed cerebral autoregulation. Cerebral tissue oxygen saturation (SctO2) measured with NIRS can be used to evaluate autoregulation because small variations in MAP will not alter SctO2 autoregulation is intact. Using this technique 18 (35%) of 51 post-cardiac arrest patients were found to have disturbed cerebral autoregulation and the majority of these patients had pre-existing hypertension. The authors suggest that the optimal MAP in these patients is likely to be higher than the 65?mmHg proposed in some guidelines and that it should be individualised. Using similar methods (tissue oxygenation index) a group from Sydney, Australia have documented an association between impaired cerebral autoregulation and poor outcome among 23 post-cardiac arrest patients.

7.4. Oxygen

Observational studies of the association between post-ROSC hyperoxaemia and outcome among adult cardiac arrest survivors have produced conflicting results. An observational cohort study of 200 post-cardiac arrest children documented higher survival rates among those who were treated with TTM and who had higher cumulative PaO2 values.

7.5. Coronary revascularisation

The role of urgent coronary angiography in cardiac arrest survivors without ST-elevation on their 12-lead ECG remains controversial. In a study from Sweden an acute coronary occlusion was present in 37% of cardiac arrest survivors who underwent urgent coronary angiography but did not have ST-elevation on the post-resuscitation ECG. In an observational study from the Czech Republic, urgent coronary angiography in comatose cardiac arrest survivors without ST-segment elevation was not associated with better clinical and neurological outcome compared with an initially conservative approach.

8. Prognostication

A survey of members of the European Society of Intensive Care Medicine demonstrated considerable uncertainty about the optimal strategy for predicting outcome among comatose cardiac arrest survivors.

Both computed tomography (CT) and magnetic resonance imaging (MRI) of the brain form part of the mutimodal approach to prognostication in the comatose post-cardiac arrest patient but precisely how these are used to inform decision-making is unclear. In an observational study from Korea, the grey to white matter ratio (GWR) obtained from early (<24?h from cardiac arrest) CT brain scans was a poor predictor of poor outcome among 283 OHCA patients. In contrast, a Swedish group documented that reduced discrimination between white and grey matter on an early CT scan was strongly associated with a poor outcome; however only 7 (4%) of 188 patients scanned within 24?h of cardiac arrest showed reduced grey–white discrimination.

Using the data from 19 post-cardiac arrest patients who underwent brain MRI scanning, a group from Korea has developed a qualitative MRI scoring system to assess the severity of hypoxic-ischaemic brain injury.Another group have studied 22 post-cardiac arrest patients who underwent repeat MRI scanning – they hypothesise that the evolving changes seen on MRI may better predict outcome.

The TTM trial protocol included a formal prognostication procedure and these data have been reported by the TTM investigators. Among 313 patients a GCS M ?2 had a false positive rate of 19.1% to predict poor outcome because of nine false predictions. Bilaterally absent pupillary reflexes had a false positive rate of 2.1% and absent corneal reflexes had a false positive rate of 2.2% (one false prediction in each group). The false positive rate for bilaterally absent SSEP N20-peaks was 2.6% (one false positive of 204 patients tested).

9. Education and quality improvement

The learning conversation is replacing the traditional ‘sandwich’ approach to feedback. A randomised controlled cross over trial amongst a group of healthcare students undergoing BLS/AED training found better skill acquisition with the learning conversation approach and improved instructor experience.

Further evidence has emerged supporting an integrated approach to quality improvement which combines CPR feedback technology, post event debriefing and scenario based training. In complementary before and after studies, consistent improvement in CPR quality has been observed in the emergency department and hospital setting respectively.,  A novel quality improvement intervention which combined CPR training with a reorganisation of the team and post event debriefing regarding preventability, clinical arrest resuscitation performance, and CPR metrics was associated with a reduced cardiac arrest rate (2.7–1.2 per 1000 patient discharges) and improved survival.

Ethics

A systematic review identified some of the many challenges faced when considering, discussing, communicating and implementing a do-not-attempt CPR (DNACPR) decision. Failing to inform and involve the patient or those close the patient in the decision making process was a common cause for complaints.One author highlights the personal impact of the failure to communicate a DNACPR decision effectively from the patient’s and relatives’ perspective and reminds us that terminology and effective communication is key.Despite widespread coverage of high profile legal cases, clinicians are slow to change behavior and members of the public continue to have un-realistic expectations about the outcome from a resuscitation attempt.,  Recording information on electronic health records is feasible and may prevent CPR when it is not indicated or wanted.

Conflicts of interest statement

JPN is Editor-in-Chief of Resuscitation. JPO, MJAP, GDP and JS are Editors of Resuscitation. JO is on the Science Advisory Board for ZOLL Circulation and serves as Cardiac Co-Chair for the National Institutes of Health-sponsored Resuscitation Outcomes Consortium (ROC). He serves as the Virginia Commonwealth University Principal Investigator for the National Institutes of Health-sponsored Neurological Emergency Treatment Trials Network (NETT). GDP is Co-Chair of the Basic Life Support Task Force of the International Liaison Committee on Resuscitation. JS is Co-Chair of the Advanced Life Support Task Force of the International Liaison Committee on Resuscitation.

References

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