Marc Blancher

Prognostic factors for extracorporeal cardiopulmonary resuscitation recipients following out-of-hospital refractory cardiac arrest. A systematic review and meta-analysis

PURPOSE Association estimates between baseline characteristics and outcomes are imprecise and inconsistent among extracorporeal cardiopulmonary resuscitation (ECPR) recipients following refractory out-of-hospital cardiac arrest (OHCA). This systematic review and meta-analysis aimed to investigate the prognostic significance of pre-specified characteristics for OHCA treated with ECPR. METHODS The Medline electronic database was searched via PubMed for articles published from January 2000 to September 2016. The electronic search was supplemented by scanning the reference lists of retrieved articles and contacting field experts. Eligible studies were historical and prospective cohort studies of adult patients undergoing ECPR following OHCA. RESULTS Fifteen primary studies were included, totaling 841 participants. The median prevalence of the primary outcome (i.e., short- or long-term survival for five studies and cerebral performance for ten studies) was 15% (range, 0-50%). The primary outcome was associated with an increased odds ratio of initial shockable cardiac rhythm (2.20; 95% confidence interval [CI], 1.30-3.72; P=0.003), shorter low-flow duration (geometric mean ratio, 0.90; 95% CI, 0.81-0.99; P=0.04), higher arterial pH value (difference, 0.12; 95% CI, 0.03-0.22; P=0.01) and lower serum lactate concentration (difference, -3.52mmol/L; 95% CI, -5.05 to -1.99; P<0.001). No significant association was found between the primary outcome and patient age (the odds of female gender and bystander CPR attempt. CONCLUSION Observational evidence from published primary studies indicates that shorter low-flow duration, shockable cardiac rhythm, higher arterial pH value and lower serum lactate concentration on hospital admission are associated with better outcomes for ECPR recipients after OHCA.

Outcome after severe accidental hypothermia in the French Alps: A 10-year review

OBJECTIVE To describe the factors associated with outcome after accidental deep hypothermia. METHODS We conducted a retrospective cohort study on patients with accidental hypothermia (core temperature <28 °C) admitted to a Level I emergency room over a 10-year period. RESULTS Forty-eight patients were included with a median temperature of 26 °C (range, 16.3-28 °C) on admission. The etiology of hypothermia was exposure to a cold environment (n = 27), avalanche (n = 13) or immersion in cold water (n = 8). Mean age was 47 ± 22 years, and 58% were males. Thirty-two patients had a cardiac arrest (CA): 15 patients presented unwitnessed cardiac arrest (UCA) and 17 patients presented rescue collapse (RC). Extracorporeal life support (ECLS) was implemented in 21 patients with refractory cardiac arrest and in two patients with hemodynamic instability. Overall mortality was 50%. For cardiac arrest patients, only three out of 15 patients with UCA survived at day 28, whereas eight out of 17 patients with RC survived. The cerebral performance category score was 4 for all the survivors of UCA and 1 [range, 1-2] for survivors of RC. Patients with poor outcome presented more UCA, a lower pH, a higher serum potassium, creatinine, serum sodium or lactate level as well as more severe coagulation disorders. CONCLUSION Cardiac arrest related to rescue collapse was associated with favorable 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 unfavorable outcome and will likely not benefit from ECLS.

Survival after avalanche-induced cardiac arrest

AIM Criteria to prolong resuscitation after cardiac arrest (CA) induced by complete avalanche burial are critical since profound hypothermia could be involved. We sought parameters associated with survival in a cohort of victims of complete avalanche burial. METHODS Retrospective observational study of patients suffering CA on-scene after avalanche burial in the Northern French Alps between 1994 and 2013. Criteria associated with survival at discharge from the intensive care unit (ICU) were collected on scene and upon admission to Level-1 trauma center. Neurological outcome was assessed at 3 months using cerebral performance category score. RESULTS Forty-eight patients were studied. They were buried for a median time of 43 min (25-76 min; 25-75th percentiles) and had a pre-hospital body core temperature of 28.0°C (26.0-30.7). Eighteen patients (37.5%) had pre-hospital return of spontaneous circulation and 30 had refractory CA. Rewarming of 21 patients (43.7%) was performed using extracorporeal life support. Eight patients (16.7%) survived and were discharged from the ICU, three (6.3%) had favorable neurological outcome at 3 months. Pre-hospital parameters associated with survival were the presence of an air pocket and rescue collapse. On admission, survivors had lower serum potassium concentrations than non-survivors: 3.2 mmol/L (2.7-4.0) versus 5.6 mmol/L (4.2-8.0), respectively (P<0.01). They also had normal values for prothrombin and activated partial thromboplastin compared to non-survivors. CONCLUSIONS Our findings indicate that survival after avalanche burial and on-scene CA is rarely associated with favorable neurological outcome. Among criteria associated with survival, normal blood coagulation on admission warrants further investigation.

Full Neurologic Recovery after Prolonged Avalanche Burial and Cardiac Arrest

Survival with full neurologic recovery after prolonged complete avalanche burial and cardiac arrest (CA) is extremely rare. It mainly depends on the presence of severe hypothermia and onset of cardiac arrest after extrication from avalanche burial (Paal et al., 2012). We describe here two case reports with full neurologic recovery following CA and prolonged complete avalanche burial. A 17-year-old male backcountry skier was completely buried by an avalanche in the French Alps (Valmeinier, Savoie, France) and was only extricated by the rescue team after 6 hours due to bad weather conditions. After extrication, an air pocket was noted and the patient had no obvious sign of trauma. He had a Glasgow Coma Scale (GCS) of 4 (verbal score of 2), a heart rate of 27 beats/min, a systolic blood pressure of 55 mmHg, and an epitympanic temperature of 22 C immediately after extrication. The rate of cooling during avalanche burial was estimated around 2.3 C/hour. After tracheal intubation and mechanical ventilation, the patient was transported to the regional level I trauma centre. Ventricular fibrillation occurred at hospital admission in the emergency room. The occurrence of CA, described as rescue collapse, was triggered by further cooling and transfer of the patient. Rectal temperature was 21.1 C on hospital admission. Cardiopulmonary resuscitation (CPR) was continued for 20 min until extracorporeal membrane oxygenation (ECMO) with veno-arterial femoral access was performed. On admission, before extracorporeal life support was initiated, arterial serum potassium was 4 mmol/L, arterial oxygen partial pressure (Pao2) 360 mmHg, arterial carbon dioxide partial pressure (Paco2) 36 mmHg, pH 7.26, and arterial serum lactate was measured at 4.6 mmol/L. After 4 days spent in the intensive care unit (ICU), the patient made a full neurologic recovery

The impact of hypothermia on serum potassium concentration: A systematic review

BACKGROUND Blood potassium is the main prognostic biomarker used for triage in hypothermic cardiac arrest. The aim of this review was to assess the impact of hypothermia on blood potassium levels and compare the underlying pathophysiological theories. METHODS The Medline electronic database was searched via PubMed for articles published from January 1970 to December 2016. The search strategy included studies related to hypothermia and potassium levels. The relevant literature on clinical studies and experimental studies was reviewed by the authors. RESULTS Among the 50 studies included in the review, 39 (78%) reported a decrease in blood potassium levels upon hypothermia onset. Hypothermic hypokalaemia is linked to an intracellular shift rather than an actual net loss. The intracellular shift is caused by a variety of factors such as enhanced functioning of Na+K+ATPase, beta-adrenergic stimulation, pH and membrane stabilisation in deep hypothermia. In contrast, hypothermia can act as an aggravating factor in severe trauma with hyperkalaemia being an indicator of an irreversible state of cell death. An increase in the blood potassium level during hypothermia may result from a lack of enzyme functioning at cold temperatures and blocked active transport. CONCLUSION Hypothermia causes an initial decrease of potassium levels; however, the final stage of hypothermic cardiac arrest can induce hyperkalaemia due to cell lysis and final depolarisation. Better understanding the physiopathology of potassium levels during accidental hypothermia could be critically important to better select patients who could benefit from aggressive resuscitation therapy such as extracorporeal cardiopulmonary resuscitation.

Medical Pathologies and Hut Guardians’ Ability to Provide First Aid in Mountain Huts: A Prospective Observational Study

OBJECTIVE To describe the resources for medical condition management in mountain huts and the epidemiology of such events. METHODS We conducted a 3-step study from April 2013 to August 2014 in French mountain huts. The first step consisted of collecting data regarding the first aid equipment available in mountain huts. The second step consisted of a qualitative evaluation of the mountain hut guardians role in medical situations through semistructured interviews. Finally, a prospective observational study was conducted in the summer season to collect all medical events (MEs) that occurred during that period. RESULTS Out of 164 hut guardians, 141 (86%) had a basic life support diploma. An automatic external defibrillator was available in 41 (26%) huts, and 148 huts (98%) were equipped with a first aid kit. According to semistructured interviews, hut guardians played a valuable role in first aid assistance. Regarding the observational study, 306 people requested the hut guardians help for medical reasons in 87 of the 126 huts included. A total of 501 MEs for approximately 56,000 hikers (0.85%) were reported, with 280 MEs (56%) involving medical pathologies and 221 (44%) MEs involving trauma-related injuries. CONCLUSIONS MEs had low prevalence, but the hut guardian played a valuable role as a first aid responder.

Cut-off values for serum potassium and core temperature at hospital admission for extracorporeal rewarming of avalanche victims in cardiac arrest

The data and estimation methods presented in this article are associated with the research article, “Cut-off values of serum potassium and core temperature at hospital admission for extracorporeal rewarming of avalanche victims in cardiac arrest: a retrospective multi-centre study” [1]. In this article we estimate recommended cut-off values for in-hospital triage with respect to extracorporeal rewarming. With only 6 survivors of 103 patients collected over a period of 20 years the ability to estimate reliable threshold values is limited. In addition, because the number of avalanche victims is also limited, a significantly larger dataset is unlikely to be obtained. We have therefore adapted two nonparametric estimation methods (bootstrapping and exact binomial distribution) to our specific needs and performed a simulations to confirm validity and reliability.

Hypothermia outcome prediction after extracorporeal life support for hypothermic cardiac arrest patients: The HOPE score

AIMS Currently, the decision to initiate extracorporeal life support for patients who suffer cardiac arrest due to accidental hypothermia is essentially based on serum potassium level. Our goal was to build a prediction score in order to determine the probability of survival following rewarming of hypothermic arrested patients based on several covariates available at admission. METHODS We included consecutive hypothermic arrested patients who underwent rewarming with extracorporeal life support. The sample comprised 237 patients identified through the literature from 18 studies, and 49 additional patients obtained from hospital data collection. We considered nine potential predictors of survival: age; sex; core temperature; serum potassium level; mechanism of hypothermia; cardiac rhythm at admission; witnessed cardiac arrest, rewarming method and cardiopulmonary resuscitation duration prior to the initiation of extracorporeal life support. The primary outcome parameter was survival to hospital discharge. RESULTS Overall, 106 of the 286 included patients survived (37%; 95% CI: 32-43%), most (84%) with a good neurological outcome. The final score included the following variables: age, sex, core temperature at admission, serum potassium level, mechanism of cooling, and cardiopulmonary resuscitation duration. The corresponding area under the receiver operating characteristic curve was 0.895 (95% CI: 0.859-0.931) compared to 0.774 (95% CI: 0.720-0.828) when based on serum potassium level alone. CONCLUSIONS In this large retrospective study we found that our score was superior to dichotomous triage based on serum potassium level in assessing which hypothermic patients in cardiac arrest would benefit from extracorporeal life support. External validation of our findings is required.

Survival of cardiac arrest patients on ski slopes: A 10-year analysis of the Northern French Alps Emergency Network☆

AIM Intense physical activity, cold and altitude make mountain sports a cause of increased risk of out-of-hospital cardiac arrest (OHCA). The difficulties of pre-hospital management related to this challenging environment could be mitigated by the presence of ski-patrollers in ski areas and use of helicopters for medical rescue. We assess whether this particular situation positively impacts the chain of survival compared to the general population. METHODS Analysis of prospectively collected data from the cardiac arrest registry of the Northern French Alps Emergency Network (RENAU) from 2004 to 2014. RESULTS 19,341 OHCAs were recorded during the period, including 136 on-slope events. Compared to other OHCAs, on-slope patients were younger (56 [40-65] vs. 66 [52-79] years, p<0.001) and more often in shockable initial rhythm (41.2% vs 20.1%, p<0.001). Resuscitation was more frequently started by a witness (43.4% vs 26.8%, p<0.001) and the time to the first electric shock was shorter (7.5min vs 14min, p<0.001), whereas time to the advanced life support (ALS) rescue arrival did not differ. The 30-day survival rate was higher for on-slope arrests (21.3% vs 5.9%, p<0.001, RR=3.61). In multivariate analysis, on-slope CA remained a positive 30-day survival factor with a 2.6 odds ratio (95% confidence interval, 1.42-4.81, p=0.002). CONCLUSION Despite difficult access and management conditions, patients undergoing OHCAs on ski slopes presented a higher survival rate, possibly explained by a healthier population, the efficiency of resuscitation by ski-patrols and similar time to ALS facilities compared to other cardiac arrests.

Accidental Hypothermia Cardiac Arrest. Keeping High Hyperkalemia Cut-Off?

Critical Care Medicine www.ccmjournal.org e593 after a profound accidental hypothermia. This Swedish young girl (7 yr old) reached simultaneously two near-records. Her temperature of 13.8°C is the second known case of survival after a temperature drop below 14°C; the coldest record being 13.7°C in a 29-year-old skier women who fell in a torrent in Norway (2). The hyperkalemia of the Swedish little girl (11.3 mmol/L) is also the second highest kalemia with good survival. The record is 11.8 mmol/L in a Canadian 31-monthold girl, lost outside her home in a freezing cold night (3). The Swedish young girl had no electrical cardiac activity on the first electrocardiogram (ECG) done by the rescue team in helicopter. It is also a very rare case of unwitnessed hypothermic cardiac arrest with a good neurologic recovery. In our 10-year review of accidental hypothermia in French Alps (4), only rescue collapses whose cardiac arrests occurred under the eyes of professional rescuers had a good chance of recovery (eight survivals over 17 rescue collapses). In our series, among the 15 unwitnessed cardiac arrests still reanimated by extracorporeal membrane oxygenation, only three patients survived but with a cerebral performance category score of 4 (i.e. vegetative coma). The ECG of the Canadian child (3) performed at hospital, 1 hour 30 minutes after first rescues, revealed in fact an electrical pulseless activity and some gasps were still noticed. The Norwegian skier trapped in a torrent (2) had her first ECG, showing asystole, only at hospital, 1 hour 30 minutes after rescue team arrival. As she was still struggling in the waterfall few minutes before rescue team arrival, it is conceivable that she might still have a cardiac activity during extraction, just before the first rescue maneuvers. Finally, this very impressive case report of Romlin et al (1) reinterrogates the decision-making criteria to attempt or not to attempt a resuscitation in hypothermic cardiac arrests. In particular, kalemia cut-off, which has been recently lowered to 8 mmol/L by international recommendations (5), should perhaps be reconsidered. The authors have disclosed that they do not have any potential conflicts of interest.