Is all ventricular fibrillation the same? A comparison of ischemically induced with electrically induced ventricular fibrillation in a porcine cardiac arrest and resuscitation model

OBJECTIVES: The standard porcine cardiac arrest model uses electrical induction of ventricular fibrillation. Reported restoration of spontaneous circulation and survival rates in this model are as high as 90% for ventricular fibrillation durations of 7-10 mins, values substantially greater than rates in the clinical population (i.e., 20% to 30%). A high first shock success rate, infrequent refibrillation, and short times for restoration of spontaneous circulation are typical of the model. The purpose of this study was to determine whether ischemic induction of ventricular fibrillation in swine followed by standard advanced cardiac life support would result in short-term outcomes approximating those observed in human victims of out-of-hospital ventricular fibrillation. DESIGN: Randomized comparative trial. SETTING: Translational research laboratory. SUBJECTS: Domestic swine (n = 40, mean weight 40 +/- 4 kg, range 34-47 kg) of both genders. INTERVENTIONS: Swine were instrumented and randomized to either electrical ventricular fibrillation induction or ischemic ventricular fibrillation, produced by balloon occlusion of the mid-left anterior descending coronary artery (n = 20 per group). Transthoracic impedance was measured and 30 Omega added in series for all animals. The balloon remained inflated during resuscitation efforts in ischemic ventricular fibrillation animals. After 7 mins of ventricular fibrillation, cardiopulmonary resuscitation was initiated and defibrillation was attempted 1 min later. Epinephrine and antiarrhythmics were administered as per guidelines. Resuscitation was terminated if restoration of spontaneous circulation had not occurred after 15 mins of advanced cardiac life support. MEASUREMENTS AND MAIN RESULTS: Although the number of countershocks required to initially terminate ventricular fibrillation was not different (electrical ventricular fibrillation 1.9 +/- 1.6, ischemic ventricular fibrillation 2.4 +/- 2.0), the refibrillation rate was higher in the ischemic ventricular fibrillation group (4.9 +/- 4 vs. 0.8 +/- 1 episodes/animal, p < .001), resulting in a greater number of shocks before restoration of spontaneous circulation (total shocks for ischemic ventricular fibrillation 9.4 +/- 5.6 vs. electrical ventricular fibrillation 2.7 +/- 2.2, p < .001). Time to restoration of spontaneous circulation was longer in the ischemic ventricular fibrillation group (430 +/- 234 secs vs. 149 +/- 120 secs, p < .001). Restoration of spontaneous circulation rates were not different (electrical ventricular fibrillation 90% vs. ischemic ventricular fibrillation 65%). However, survival to 6 hrs was greater in the electrical ventricular fibrillation group (18 of 20, 90%) than in the ischemic ventricular fibrillation group (8 of 20, 40%, p = .002). CONCLUSIONS: Resuscitation from ischemic ventricular fibrillation is more difficult than electrical ventricular fibrillation and is characterized by greater time to restoration of spontaneous circulation, frequent refibrillation, greater number of countershocks, higher epinephrine dose during resuscitation efforts, profound cardiac dysfunction, and a short-term survival rate approaching clinical experience. Ischemically induced ventricular fibrillation is a more clinically relevant model for the evaluation of resuscitation interventions.     

Comparison of myocardial metabolism by using PET after resuscitation between ventricular fibrillation cardiac arrest and asphyxia cardiac arrest北大核心CSCD

Objective To characterize myocardial metabolism using positron emission tomography (PET) in porcine models of ventricular fibrillation cardiac arrest (VFCA) and asphyxiation cardiac arrest (ACA) after resuscitation. Methods Thirty-Two healthy miniature pigs were randomized into two groups. The pigs of VFCA group (a = 16) were subject to programmed electric stimulation to create a ventricular fibrillation cardiac arrest, and the pigs of ACA group (n = 16) were subjected to endotracheal tube clamping to establish a cardiac arrest (CA). Once modeling was established, pigs with CA were left untreated for a period of 8 mm. Two minutes following initiation of cardiopulmonary resuscitation (CPR), defibrillation was attempted until the restoration of spontaneous circulation (ROSC) was achieved or animals died. To assess myocardial metabolism, PET was performed before modeling, 4 hrs and 24hrs after ROSC. To analyze 18F-FDG myocardial uptake in PET, the maximum standardized uptake value (SUV1) was measured. Results ROSC was obtained in 100% of pigs in VFCA group and only 50% in ACA group. The average survival time in VFCA pigs was significantly longer than that in ACA pigs (22. 63 ± 0. 95) hvs. (8. 75 ± 2. 54) h, P <0.01. VFCA pigs had better mean arterial pressure and cardiac output after ROSC than ACA pigs. Myocardial metabolism imaging using PET demonstrated that myocardial metabolism injuries after ACA were more severe and widespread than those after VFCA at 4 hrs and 24hrs after ROSC and SUV> was much higher in VFCA group than that in ACA group [4 h after ROSC: (1.9 ± 0. 3) vs. (1.0 ±0.4), P <0. 01; 24 h after ROSC: (2.4 ±0.6) vs. (1.2±0.5), P <0.01]. Conclusions Compared with VFCA, ACA causes more severe cardiac metabolism dysfunction associated with less successful resuscitation and shorter survival time; therefore they should he treated as different pathological entities.     

Can successful treatment of cardiac arrest be a performance indicator for hospitals?

BACKGROUND: Although resuscitation from cardiac arrest prevents more deaths from acute myocardial infarction (MI) than any other treatment, results have not been audited widely nor performance standards proposed. METHODS: The Myocardial Infarction National Audit Project (MINAP) uses electronic transmission of a 53-item dataset to a central cardiac audit database (CCAD). From October 2000 to August 2002, transmission by 218 hospitals of data from 55,906 cases of MI with 4934 attempted resuscitations from a first arrest, allowed for examination of factors determining survival, and for possible future measurement of success in resuscitation as a performance indicator. We investigated two possible indicators: (i) numbers of survivors from arrest in ventricular fibrillation or pulseless ventricular tachycardia (VF/VT) per 1000 cases of MI; and (ii) observed/expected (O/E) ratios for survival taking all VF/VT arrests rather than MI as the denominator, and adjusting for differing age structures and admission delays among individual hospitals. FINDINGS: Of the 4934 reported patients suffering a first arrest, 1778 (36%) survived to be discharged from hospital. The presenting rhythm was VF/VT in 2321 (47%) patients of whom 1461 (63%) survived. Survival for all 218 hospitals together had the relatively small 95% confidence limits of 26 (25-27) survivors from VF/VT per 1000 MI. However, the small numbers from individual hospitals made it impossible in most cases, whichever of the two indicators was used, to separate quality of performance and completeness of reporting from the factor of chance. INTERPRETATION: Audit of success in resuscitation is essential if performance in the treatment of MI is to be assessed. However, the relatively small numbers of arrests occurring in individual hospitals means that if year on year improvements are to be documented, audit must be carried out among groups of hospitals or on a national scale.     

What is the appropriate outcome for studies of treatments for out-of-hospital cardiac arrest?

BACKGROUND: A good outcome following out-of-hospital medical care for cardiac arrest is survival to hospital discharge. Because a large number of patients are required to detect a minimum clinically important difference in survival, an intermediate outcome such as hospital admittance is commonly used. For an intermediate outcome to be a useful surrogate, the survival rate conditional on achieving the intermediate outcome should not depend upon the field treatment. If so, an advantage of the intermediate outcome may be a smaller sample size. However, recent trials demonstrate that survival conditional on admittance may depend upon the field treatment. Even if the resources are available to power a study for survival, is survival the right outcome? For example, no increase in survival and a large increase in admittance could be considered a bad result, as it represents a substantial waste of resources. Similarly no increase in mortality and a decrease in admittance should be considered a good result, as it represents a substantial cost savings without any sacrifice of life. Both admittance and survival are important outcomes and need to be considered jointly, that is, as a bivariate outcome. METHODS: Cost-effectiveness concepts are used to distinguish between a good and bad (bivariate) outcome. Simulations are conducted to compare the impact of the univariate and the bivariate outcomes in a variety of trial scenarios. A table of sample sizes is computed for the bivariate outcome across a range of trial scenarios. RESULTS: The bivariate outcome outperforms both univariate outcomes for most alternatives. The required sample size for the joint outcome of admittance and survival may be substantially, over 50%, less than that for the survival outcome alone. CONCLUSION: Use of the bivariate outcome could provide more informed decision making about resuscitation strategies and at less cost then the current gold standard of hospital survival.     

Exploring which patients without return of spontaneous circulation following ventricular fibrillation out-of-hospital cardiac arrest should be transported to hospital?

Background

Currently many emergency medical services (EMS) that provide advanced cardiac life support (ACLS) at scene do not routinely transport out-of-hospital cardiac arrest (OHCA) patients without sustained return of spontaneous circulation (ROSC). This is due to logistical difficulties and historical poor outcomes. However, new technology for mechanical chest compression has made transport to hospital safer and extracorporeal membrane oxygenation during cardiopulmonary resuscitation (ECPR) enabling further intervention, may result in ROSC. We aimed to explore the characteristics and outcomes of patients with OHCA who were transported to hospital with ongoing CPR in the absence of ROSC, who might benefit from this new technology.

Methods and results

The Victorian Ambulance Cardiac Arrest Registry (VACAR) was searched for adult OHCA with an initial shockable rhythm between 2003 and 2012. There were 5593 OHCA meeting inclusion criteria. Analysis was performed on 3095 (55%) of patients who did not achieve sustained ROSC in the field. Of these only 589 (20%) had ongoing CPR to hospital. There was a significant decline in rates of transport over the study period. Predictors of transport with ongoing CPR included younger patients, decreased time to first shock and intermittent ROSC prior to transport. Survival to hospital discharge occurred in 52 (9%) of patients who had ongoing CPR to hospital.

Conclusion

In an EMS that provides ACLS at scene, patients without ROSC in the field who receive CPR to hospital have poor outcomes. Developing a system which provides safe transport with ongoing CPR to a hospital that provides ECPR, should be considered.     

In-hospital cardiac arrest: Is outcome related to the time of arrest?

BACKGROUND: Whether outcome from in-hospital cardiopulmonary resuscitation (CPR) is poorer when it occurs during the night remains controversial. This study examined the relationship between CPR during the various hospital shifts and survival to discharge. METHODS: CPR attempts occurring in a tertiary hospital with a dedicated, certified resuscitation team were recorded prospectively (Utstein template guidelines) over 24 months. Medical records and patient characteristics were retrieved from patient admission files. RESULTS: Included were 174 in-hospital cardiac arrests; 43%, 32% and 25% in morning evening and night shifts, respectively. Shift populations were comparable in demographic and treatment related variables. Asystole (p < 0.01) and unwitnessed arrests (p = 0.05) were more common during the night. Survival to discharge was poorer following night shift CPR than following morning and evening shift CPR (p = 0.04). When asystole (being synonymous with death) was excluded from the analysis, the odds of survival to discharge was not higher for witnessed compared to unwitnessed arrest but was 4.9 times higher if the cardiac arrest did not occur during the night shift (p = 0.05, logistic regression). The relative risk of eventual in-hospital death for patients with return of spontaneous circulation (ROSC) following night shift resuscitation was 1.9 that of those with ROSC following morning or evening resuscitation (Cox regression). CONCLUSIONS: Although unwitnessed arrest is more prevalent during night shift, resuscitation during this shift is associated with poorer outcomes independently of witnessed status. Further research is required into the causes for the increased mortality observed after night shift resuscitation.     

Regional TNFα mapping in the brain reveals the striatum as a neuroinflammatory target after ventricular fibrillation cardiac arrest in rats

Cardiac arrest (CA) triggers neuroinflammation that could play a role in a delayed neuronal death. In our previously established rat model of ventricular fibrillation (VF) CA characterized by extensive neuronal death, we tested the hypothesis that individual brain regions have specific neuroinflammatory responses, as reflected by regional brain tissue levels of tumor necrosis factor (TNF)α and other cytokines. In a prospective study, rats were randomized to 6 min (CA6), 8 min (CA8) or 10 min (CA10) of VF CA, or sham group. Cortex, striatum, hippocampus and cerebellum were evaluated for TNFα and interleukin (IL)-1α, IL-1β, IL-2, IL-4, IL-6, IL-10, IL-12 and interferon gamma at 3 h, 6 h or 14 d after CA by ELISA and Luminex. Immunohistochemistry was used to determine the cell source of TNFα. CA resulted in a selective TNFα response with significant regional and temporal differences. At 3 h after CA, TNFα-levels increased in all regions depending on the duration of the insult. The most pronounced increase was observed in striatum that showed 20-fold increase in CA10 vs. sham, and 3-fold increase vs. CA6 or CA8 group, respectively (p < 0.01). TNFα levels in striatum decreased between 3 h and 6 h, but increased in other regions between 3 h and 14 d. TNFα levels remained twofold higher in CA6 vs. shams across brain regions at 14 d (p < 0.01). In contrast to pronounced TNFα response, other cytokines showed only a minimal increase in CA6 and CA8 groups vs. sham in all brain regions with the exception that IL-1β increased twofold in cerebellum and striatum (p < 0.01). TNFα colocalized with neurons. In conclusion, CA produced a duration-dependent acute TNFα response, with dramatic increase in the striatum where TNFα colocalized with neurons. Increased TNFα levels persist for at least two weeks. This TNFα surge contrasts the lack of an acute increase in other cytokines in brain after CA. Given that striatum is a selectively vulnerable brain region, our data suggest possible role of neuronal TNFα in striatum after CA and identify therapeutic targets for future experiments.     

How does interruption of cardiopulmonary resuscitation affect survival from cardiac arrest?

PURPOSE OF REVIEW: Survival rates from cardiac arrest are unacceptably low. The present review aims to summarize recent contributions to cardiopulmonary resuscitation research in relation to hemodynamic consequences and especially survival resulting from interruption of chest compressions for defibrillation and rescue breathing. RECENT FINDINGS: Data from animal and human studies strongly support the negative consequences for overall survival when cardiopulmonary resuscitation is interrupted for rescue breathing and rhythm analysis. Furthermore, in settings of prolonged cardiac arrest, electrical defibrillation may not have the highest priority as initial intervention. SUMMARY: Interruption of cardiopulmonary resuscitation negatively affects survival from cardiac arrest. Fewer interruptions for interventions and interventions that take less time may improve survival.     

Does the prognosis of cardiac arrest differ in trauma patients?

OBJECTIVE: It is proposed to not resuscitate trauma patients who have a cardiac arrest outside the hospital because they are assumed to have a dismal prognosis. Our aim was to compare the outcome of patients with traumatic or nontraumatic ("medical") out-of-hospital cardiac arrest. DESIGN: Cohort analysis of patients with out-of-hospital cardiac arrest included in the European Epinephrine Study Group's trial comparing high vs. standard doses of epinephrine. SETTING: Nine French university hospitals. PATIENTS: A total of 2,910 patients. INTERVENTIONS: Patients were successively and randomly assigned to receive repeated high doses (5 mg each) or standard doses (1 mg each) of epinephrine at 3-min intervals. MEASUREMENTS AND MAIN RESULTS: Return of spontaneous circulation, survival to hospital admission and discharge, and secondary outcome measures of 1-yr survival and neurologic outcome were recorded. In the trauma group, patients were younger (42 +/- 17 vs. 62 +/- 17 yrs, p < .001), presented with fewer witnessed out-of-hospital cardiac arrests (62.3% vs. 79.7%), and had fewer instances of ventricular fibrillation as the first documented pulseless rhythm (3.4% [95% confidence interval, 1.2-5.5%] vs. 17.3% [15.8-18.7%]). A return of spontaneous circulation was observed in 91 of 268 trauma patients (34.0% [28.3-39.6%]) compared with 797 of 2,642 medical patients (30.2% [28.4-31.9%]), and more trauma patients survived to be admitted to the hospital (29.9% [24.4-35.3%] vs. 23.5% [22.0-25.2%]). However, there was no significant difference between trauma and medical groups at hospital discharge (2.2% [0.5-4.0%] vs. 2.8% [2.1-3.4%]) and 1-yr survival (1.9% [0.3-3.5%] vs. 2.5% [1.9-3.1%]). Among patients who were discharged, a good neurologic status was observed in two trauma patients (33.3% [4.3-77.7%]) and 37 medical patients (50% [38.1-61.9%]). CONCLUSIONS: The survival and neurologic outcome of out-of-hospital cardiac arrest were not different between trauma and medical patients. This result suggests that, under the supervision of senior physicians, active resuscitation after out-of-hospital cardiac arrest is as important in trauma as in medical patients.     

Does resuscitation training affect outcome from cardiac arrest?

It is established that basic life support (BLS) is performed inadequately by both nursing and medical staff and that the ability to retain these skills, once trained, is low. In addition, the initial success rate from cardiopulmonary arrest is poor. By implementing the advanced life support (ALS) course and providing frequent updates on resuscitation skills and management, it is expected that cardiac arrest outcome results should improve. This data is from a 4 year audit of in-hospital cardiac arrest within an adult patient group between January 1993 and December 1996. The average return response of all audit forms was 86.5%. The total sample consisted of 367 separate arrests where the initial rhythm was documented as either ventricular fibrillation (VF)/ventricular tachycardia (VT) (58.3%), asystole (21.7%), electromechanical dissociation (EMD) (7.0%) and other (13.0%). Initial success was defined as return of spontaneous circulation (ROSC). This was achieved in 75.0% of all resuscitation attempts. Within the VF/VT group, successful outcome remained consistent over the 4-year period with an ROSC of 85%. Successful outcome remained consistent in the EMD group, however, the number of arrests was small. Within the asystole group, initial survival increased from 47.5% in 1993-1994 to 67.5% in 1995-1996. These results suggest that BLS and ALS training may only have an impact on initial survival from cardiac arrest.