Which factors influence spontaneous state transitions during resuscitation?

BackgroundThe clinical state (i.e. ventricular fibrillation/tachycardia: VF/VT, asystole: ASY, pulseless electrical activity: PEA, or return of spontaneous circulation, ROSC) during cardiopulmonary resuscitation determines patient management. We investigate how spontaneous transitions (i.e. not forced by DC shock) between these states are influenced by factors like age, gender, bystander CPR, CPR quality, proportion of time spent in a state, or the number of state transitions.MethodsDetailed recordings from CPR attempts in 304 out-of-hospital cardiac arrests in Akershus (Norway), Stockholm (Sweden), and London (UK) were obtained from modified Heartstart 4000 defibrillators. Spontaneous state transitions were studied using a non-parametric intensity regression method that can handle dynamic factors like the state history properly.ResultsThe initial state tended to preserve itself, as did cumulative time in any state. Recent DC shock, bystander CPR, location, response time, gender, compression depth, and ventilation rate were important for some transitions. More ventilation during PEA might possibly avert development to ASY and favour ROSC; otherwise observed variations in CPR quality had little impact.ConclusionUsing a novel intensity regression approach we studied the influence of various factors on spontaneous (i.e. non-shock) state transitions during CPR. State development was largely determined by the initial state, the proportion of time spent in a state, and the transition frequency; all probably reflecting the underlying aetiology.     

Clinical state transitions during advanced life support (ALS) in in-hospital cardiac arrest

Background

When providing advanced life support (ALS) in cardiac arrest, the patient may alternate between four clinical states: ventricular fibrillation/tachycardia (VF/VT), pulseless electrical activity (PEA), asystole, and return of spontaneous circulation (ROSC). At the end of the resuscitation efforts, either death has been declared or sustained ROSC has been obtained. The aim of this study was to describe and analyze the clinical state transitions during ALS among patients experiencing in-hospital cardiac arrest.

Methods and results

The defibrillator files from 311 in-hospital cardiac arrests at the University of Chicago Hospital (IL, USA) and St. Olav University Hospital (Trondheim, Norway) were analyzed (clinicaltrials.gov: NCT00920244). The transitions between clinical states were annotated along the time axis and visualized as plots of the state prevalence according to time. The cumulative intensity of the state transitions was estimated by the Nelson–Aalen estimator for each type of state transition, and for the intensities of overall state transitions. Between 70% and 90% of patients who eventually obtained sustained ROSC had progressed to ROSC by approximately 15–20 min of ALS, depending on the initial rhythm. Patients behaving unstably after this time period, i.e., alternating between ROSC, VF/VT and PEA, had a high risk of ultimately being declared dead.

Conclusions

We provide an overall picture of the intensities and patterns of clinical state transitions during in-hospital ALS. The majority of patients who obtained sustained ROSC obtained this state and stabilized within the first 15–20 min of ALS. Those who continued to behave unstably after this time point had a high risk of ultimately being declared dead.     

Shock outcome is related to prior rhythm and duration of ventricular fibrillation

BACKGROUND: Several different ventricular fibrillation (VF) analysis features based on ECG have been reported for shock outcome prediction. In this study we investigated the influence of the time from VF onset to shock delivery (VF duration) and the rhythm before onset of VF, on the probability of return of spontaneous circulation (ROSC). We also analysed how these factors relate to the VF analysis feature median slope. METHODS: ECG recordings from 221 cardiac arrest patients from previously published prospective studies on the quality of CPR were used. VF duration and prior rhythm were determined when VF occurred during the episode. Median slope before each shock was calculated. RESULTS: The median VF duration was shorter in shocks producing ROSC, 24 seconds (s) versus 70s (P<0.001). VF duration shorter than 30s resulted in 27% ROSC versus 10% for those longer than 30s (OR=3.5 [95% CI: 2.2-5.4]). The prior rhythm influenced the probability of ROSC, with perfusing rhythm being superior, followed by PEA, asystole, and "poor" PEA (broad complexes and/or irregular/very slow rate), respectively. The probability of ROSC corresponded well with the average median slope value for each group, but the correlation between median slope and VF duration was very poor (r2=0.05). CONCLUSIONS: Based on our findings, detection of VF during ongoing chest compressions might be valuable because VF of short duration was associated with ROSC. Further, the rhythm before VF affects shock outcome with a perfusing rhythm giving the best prospect. The median slope can be used for shock outcome prediction, but not for determining VF duration. A combination could be beneficial and warrants further studies.     

Significant factors in predicting sustained ROSC in paediatric patients with traumatic out-of-hospital cardiac arrest admitted to the emergency department

BACKGROUND: Paediatric patients with out-of-hospital cardiac arrest (OHCA) due to trauma pose difficult challenges in resuscitation. Trauma is a major cause of OHCA in children. The aim of this study was to determine which factors were related to predicting a sustained return of spontaneous circulation (ROSC) in paediatric OHCA patients with trauma. METHOD: This retrospective study comprised 115 paediatric patients (56 traumatic and 59 non-traumatic OHCA patients) aged younger than 18 years who had been admitted to the emergency department (ED) from January 2000 to December 2004. We analysed the demographic data and the factors that may have influenced sustained ROSC in the group of OHCA paediatric patients with trauma. The non-trauma group was established as a control group. Survival analysis was used to compare differences in survival rate between trauma and non-trauma OHCA patients. Receiver operating characteristic (ROC) analysis was used to determine the significant in-hospital CPR duration related to sustained ROSC. RESULTS: Initial cardiac rhythm on arrival (P=0.005) and the duration of in-hospital CPR (P<0.001) were significant factors. Patients with PEA or VF had higher rate of sustained ROSC than those with asystole (PEA: P=0.003, VF: P=0.03). In the survival analysis, OHCA children with trauma had a lower chance of survival than non-trauma children as the interval from the scene to the ER increased (P=0.008). Based on the ROC analysis, the cut-off values of in-hospital CPR duration were 25min in OHCA paediatric patients with trauma. CONCLUSION: Several significant factors relating to sustained ROSC were determined in the OHCA paediatric patients with trauma; most importantly, we found that in-hospital CPR may have to be performed for at least 25min to enable a spontaneous circulation to return.     

Optimal loop duration during the provision of in-hospital advanced life support (ALS) to patients with an initial non-shockable rhythm

Background

In advanced life support (ALS), time-cycled “loops” of chest compressions form the basis of action. However, the provider must compromise between interrupting compressions and detecting a change in cardiac rhythm. An “optimal” loop duration would best balance these choices. The current international CPR guidelines recommend 2-min loop durations. The aim of this study was to investigate the “optimal” loop duration in patients with initial asystole or pulseless electrical activity (PEA).

Materials and methods

Detailed defibrillator recordings from 249 in-hospital cardiac arrests at the University of Chicago Medicine (Chicago, IL) and St. Olav University Hospital (Trondheim, Norway) were analysed. The clinical states of asystole, PEA, ventricular fibrillation/-tachycardia (VF/VT) and return of spontaneous circulation (ROSC) were annotated along the time axis. PEA and asystole were combined as a single state for the analysis of state development. The probability of staying in PEA/asystole over time was estimated non-parametrically. In addition, to distinguish between initial and secondary PEA/asystole, the latter was defined by the transition from VF/VT or ROSC.

Results

Among patients with initial PEA (n = 179), 25% and 50% of patients had left PEA/asystole after 4 and 9 min of ALS efforts, respectively. The corresponding time points for patients with initial asystole (n = 70) were 7.3 and 13.3 min, respectively. The probability of transition from secondary PEA/asystole to ROSC or VF/VT varied between 10% and 20% in each 2–4 min interval.

Conclusion

The “optimal” first loop duration may be 4 min in initial PEA and 6–8 min in initial asystole. If secondary PEA/asystole is encountered, 2-min loop duration seems appropriate.     

Beyond ventricular fibrillation analysis: Comprehensive waveform analysis for all cardiac rhythms occurring during resuscitation

Aim

To propose a method which analyses the electrocardiogram (ECG) waveform of any cardiac rhythm occurring during resuscitation and computes the probability of that rhythm converting into another with better prognosis (P_des).

Methods

Rhythm transitions occurring spontaneously or due to defibrillation were analyzed. For each possible rhythm, ventricular fibrillation/ventricular tachycardia (VF/VT), pulseless electrical activity (PEA), pulse-generating rhythm (PR) and asystole (AS), the desired and undesired transitions were defined. ECG segments corresponding to the last 3 s of rhythms prior to transition were used to extract waveform features. For each rhythm type, waveform features were combined into a logistic regression model to develop a rhythm specific classifier of desired transitions. This model was the monitoring function for the P_des. The capacity of each rhythm specific classifier to discriminate between desired and undesired transitions was evaluated in terms of area under the curve (AUC). P_des was integrated into a state sequence representation, which structures the information of cardiac arrest episodes, to analyze the effect of therapy on patient. As a case study, the effect of optimal/suboptimal cardiopulmonary resuscitation (CPR) on P_des was analyzed. The mean P_des was computed for the pre- and post-CPR intervals which presented the same underlying rhythm. The relationship between the optimal/suboptimal CPR and increase/decrease of P_des was analyzed.

Results

The AUC was 0.80, 0.79, 0.73 and 0.61 for VF/VT, PEA, PR and AS respectively. The P_des quantified the probability of every rhythm of the episode developing to a better state, and the evolution of P_des was coherent with the provided therapy. The case study indicated, for most rhythms, that positive trends in the dynamic behaviour could be associated with optimal CPR, whereas the opposite seemed true for negative trends.

Conclusion

A method for continuous ECG waveform analysis covering all cardiac rhythms during resuscitation has been proposed. This methodology can be further developed to be used in retrospective studies of CPR techniques, and, in the future, for potentially monitoring in real time the probability of survival of patients being resuscitated.     

Evaluation of Biphasic Transthoracic Defibrillation in an Animal Model of Prolonged Ventricular Fibrillation

OBJECTIVES: To determine whether a biphasic defibrillation waveform (BDW) would produce a superior rate of converting prolonged ventricular fibrillation (VF) into a perfusing rhythm and delay the occurrence of asystole and/or pulseless electrical activity (PEA) during the resuscitation attempt, when compared with a monophasic defibrillation waveform (MDW). METHODS: The authors performed a prospective, randomized, blinded experiment using an established swine model of prolonged VF. Thirty-four mixed-breed domestic swine (mean mass 22.9 kg) were sedated (ketamine/xylazine), anesthetized (isoflurane), and intubated. Aortic and femoral venous catheters were placed. ECG was monitored continuously. The animals were shocked into VF (3-s, 100-mA, 60-Hz shock), and were untreated for 8 minutes. Advanced Cardiac Life Support (ACLS) began with 1 minute of standardized (Thumper) chest compressions and ventilation. The animals were randomized to treatment with either BDW or MDW. Standard ACLS protocols were followed. The energy sequence was 2.5 J/kg first, 3.5 J/kg second, and 4.5 J/kg for all subsequent shocks. Outcome variables were time to event of asystole/PEA, return of spontaneous circulation (ROSC), and one-hour survival. Data were analyzed with two-tailed Fisher's exact test and Kaplan-Meier survival plots (alpha = 0.05). RESULTS: ROSC occurred more frequently in the BDW group (7/17) compared with the MDW group (1/17); p = 0.04. Survival analysis showed that the BDW significantly delayed the occurrence of asystole/PEA during the resuscitation attempt when compared with the MDW; log-ranked p = 0.02. One-hour survival rates (5/17 BDW and 1/17 MDW, p = 0.17) did not differ. CONCLUSIONS: BDW resulted in a superior rate of ROSC and delay in the occurrence of asystole/ PEA during the resuscitation attempt when compared with MDW.     

Does the presence or absence of sonographically identified cardiac activity predict resuscitation outcomes of cardiac arrest patients?

This study evaluated the ability of cardiac sonography performed by emergency physicians to predict resuscitation outcomes of cardiac arrest patients. A convenience sample of cardiac arrest patients prospectively underwent bedside cardiac sonography at 4 emergency medicine residency-affiliated EDs as part of the Sonography Outcomes Assessment Program. Cardiac arrest patients in pulseless electrical activity (PEA) and asystole underwent transthoracic cardiac ultrasound B-mode examinations during their resuscitations to assess for the presence or absence of cardiac kinetic activity. Several end points were analyzed as potential predictors of resuscitations: presenting cardiac rhythms, the presence of sonographically detected cardiac activity, prehospital resuscitation time intervals, and ED resuscitation time intervals. Of 70 enrolled subjects, 36 were in asystole and 34 in PEA. Patients presenting without evidence of cardiac kinetic activity did not have return of spontaneous circulation (ROSC) regardless of their cardiac rhythm, asystole, or PEA. Of the 34 subjects presenting with PEA, 11 had sonographic evidence of cardiac kinetic activity, 8 had ROSC with subsequent admission to the hospital, and 1 had survived to hospital discharge with scores of 1 on the Glasgow-Pittsburgh Cerebral Performance scale and 1 in the Overall Performance category. The presence of sonographically identified cardiac kinetic motion was associated with ROSC. Time interval durations of cardiac resuscitative efforts in the prehospital environment and in the ED were not accurate predictors of ROSC for this cohort. Cardiac kinetic activity, or lack thereof, identified by transthoracic B-mode ultrasound may aid physicians' decision making regarding the care of cardiac arrest patients with PEA or asystole.     

Outcome of out-of-hospital postcountershock asystole and pulseless electrical activity versus primary asystole and pulseless electrical activity.

OBJECTIVE: In the prehospital setting, countershock terminates ventricular fibrillation (VF) in about 80% of cases. However, countershock is most commonly followed by asystole or pulseless electrical activity (PEA). The consequences of such a countershock outcome have not been well studied. The purpose of this investigation was to compare the outcome of prehospital VF victims shocked into asystole or PEA with that of patients whose first documented rhythm was asystole or PEA (primary asystole or PEA). DESIGN: Observational, retrospective study conducted over 5 yrs (1995-1999). SETTING: A municipal hospital with a catchment area of >200,000. PATIENTS: Consecutive adult patients with out-of-hospital nontraumatic cardiopulmonary arrest of cardiac origin. Patients found in VF who developed asystole or PEA after countershocks (group 1) and patients found in asystole or PEA (primary asystole or PEA) (group 2) were included if the reported downtime was <10 min. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Study end points included restoration of circulation (defined as a pulse for any duration), survival to hospital admission, and survival to hospital discharge. Ratios were determined, 95% confidence intervals were calculated, and observed differences were compared. For group 1 patients (n = 101), 61% of patients had a bystander-witnessed collapse and 34% received bystander cardiopulmonary resuscitation. For group 2 patients (n = 140), collapse was bystander witnessed in 71% and 45% received bystander cardiopulmonary resuscitation. These differences were not statistically significant. Restoration of circulation was significantly more frequent in group 2 than group 1 (42% vs. 16%, p <.001) as was survival to hospital admission (36% vs. 11%, p =.001). Survival to hospital discharge was greater in group 2 patients, but the difference failed to achieve statistical significance (10% vs. 3%, p =.062). CONCLUSIONS: Countershock of prolonged VF followed by a nonperfusing rhythm has a worse prognosis than primary asystole or PEA and may be related to myocardial electrical injury.     

A pilot study examining the role of regional cerebral oxygen saturation monitoring as a marker of return of spontaneous circulation in shockable (VF/VT) and non-shockable (PEA/Asystole) causes of cardiac arrest

Background

Non-invasive monitoring of cerebral perfusion and oxygen delivery during cardiac arrest is not routinely utilized during cardiac arrest resuscitation. The objective of this study was to investigate the feasibility of using cerebral oximetry during cardiac arrest and to determine the relationship between regional cerebral oxygen saturation (rSO2) with return of spontaneous circulation (ROSC) in shockable (VF/VT) and non-shockable (PEA/asystole) types of cardiac arrest.

Methods

Cerebral oximetry was applied to 50 in-hospital and out-of-hospital cardiac arrest patients.

Results

Overall, 52% (n = 26) achieved ROSC and 48% (n = 24) did not achieve ROSC. There was a significant difference in mean ± SD rSO2% in patients who achieved ROSC compared to those who did not (47.2 ± 10.7% vs. 31.7 ± 12.8%, p < 0.0001). This difference was observed during asystole (median rSO2 (IQR) ROSC versus no ROSC: 45.0% (35.1–48.8) vs. 24.9% (20.5–32.9), p < 0.002) and PEA (50.6% (46.7–57.5) vs. 31.6% (18.8–43.3), p = 0.02), but not in the VF/VT subgroup (43.7% (41.1–54.7) vs. 42.8% (34.9–45.0), p = 0.63). Furthermore, it was noted that no subjects with a mean rSO2 < 30% achieved ROSC.

Conclusions

Cerebral oximetry may have a role as a real-time, non-invasive predictor of ROSC during cardiac arrest. The main utility of rSO2 in determining ROSC appears to apply to asystole and PEA subgroups of cardiac arrest, rather than VF/VT. This observation may reflect the different physiological factors involved in recovery from PEA/asytole compared to VF/VT. Whereas in VF/VT, successful defibrillation is of prime importance, however in PEA and asytole achieving ROSC is more likely to be related to the quality of oxygen delivery. Furthermore, a persistently low rSO2 <30% in spite of optimal resuscitation methods may indicate futility of resuscitation efforts.     

Dynamic effects of adrenaline (epinephrine) in out-of-hospital cardiac arrest with initial pulseless electrical activity (PEA)

BackgroundIn cardiac arrest, pulseless electrical activity (PEA) is a challenging clinical syndrome. In a randomized study comparing intravenous (i.v.) access and drugs versus no i.v. access or drugs during advanced life support (ALS), adrenaline (epinephrine) improved return of spontaneous circulation (ROSC) in patients with PEA. Originating from this study, we investigated the time-dependent effects of adrenaline on clinical state transitions in patients with initial PEA, using a non-parametric multi-state statistical model.Methods and resultsPatients with available defibrillator recordings were included, of whom 101 received adrenaline and 73 did not. There were significantly more state transitions in the adrenaline group than in the no-adrenaline group (rate ratio = 1.6, p < 0.001). Adrenaline markedly increased the rate of transition from PEA to ROSC during ALS and slowed the rate of being declared dead; e.g. by 20 min 20% of patients in the adrenaline group had been declared dead and 25% had obtained ROSC, whereas 50% in the no-adrenaline group have been declared dead and 15% had obtained ROSC. The differential effect of adrenaline could be seen after approx. 10 min of ALS for most transitions. For both groups the probability of deteriorating from PEA to asystole was highest during the first 15 min. Adrenaline increased the rate of transition from PEA to ventricular fibrillation or -tachycardia (VF/VT), and from ROSC to VF/VT.ConclusionsAdrenaline has notable clinical effects during ALS in patients with initial PEA. The drug extends the time window for ROSC to develop, but also renders the patient more unstable. Further research should investigate the optimal dose, timing and mode of adrenaline administration during ALS.     

Traumatic out-of-hospital cardiac arrests in Melbourne, Australia

Introduction

Many consider attempted resuscitation for traumatic out-of-hospital cardiac arrest (OHCA) futile. This study aims to describe the characteristics and profile of adult traumatic OHCA.

Methods

The Victorian Ambulance Cardiac Arrest Registry (VACAR) was used to identify all trauma related cases of OHCA in patients aged ≥16 years.

Results

Between 2000 and 2009, EMS attended 33,178 OHCAs of which 2187 (6.6%) had a traumatic aetiology. The median age (IQR) of traumatic OHCA cases was 36 (25–55) years and 1612 were male (77.5%). Bystander CPR was performed in 201 cases (10.2%) with median (IQR) EMS response time 8 (6–11) min. The first recorded rhythm by EMS was asystole seen in 1650 (75.4%), PEA in 294 (13.4%) cases and VF in 35 cases (1.6%). Cardiac output was present in 208 (9.5%) cases who subsequently had an EMS witnessed OHCA. EMS attempted resuscitation in 545 (24.9%) patients of whom 84 (15.4%) achieved ROSC and were transported, and 27 (5.1%) survived to hospital discharge; 107 were transported with CPR of whom 8 (7.4%) survived to hospital discharge. Where EMS attempted resuscitation in traumatic OHCAs, survival for VF was 11.8% (n = 4), PEA 5.1% (n = 10) and asystole 2.4% (n = 3). In EMS witnessed traumatic OHCA, resuscitation was attempted in 175 cases (84.1%), 35 (16.8%) patients achieved sustained ROSC before transport of whom 5 (14%) survived to leave hospital and 60 (28.8%) were transported with CPR of whom 6 (10%) survived to leave hospital. Compared to OHCA cases with ‘presumed cardiac’ aetiology traumatic OHCAs were younger [median years (IQR): 36 (25–55) vs 74 (61–82)], had resuscitation attempted less (25% vs 48%), were less likely to have a shockable rhythm (1.6% vs 17.1%), were more likely to be witnessed (62.8% vs 38.1%) and were less likely to receive bystander CPR (10.2% vs 25.5%) (p < 0.001, respectively). Multivariate logistic regression identified factors associated with EMS decision to attempt resuscitation. The odds ratio [OR (95% CI)] for ‘presence of bystander CPR’ was 5.94 (4.11–8.58) and for ‘witnessed arrest’ was 2.60 (1.86–3.63).

Conclusion

In this paramedic delivered EMS attempted resuscitation was not always futile in traumatic OHCA with a survival of 5.1%. The quality of survival needs further study.     

Resuscitation in the hospital: relationship of year and rhythm to outcome

OBJECTIVE: determine the frequency of initial rhythms in in-hospital resuscitation and examine its relationship to survival. Assess changes in outcome over time. METHODS: retrospective cohort (registry) including all admissions to the Medical Center of Central Georgia in which a resuscitation was attempted between 1 January, 1987 and 31 December, 1996. RESULTS: the registry includes 3327 admissions in which 3926 resuscitations were attempted. Only the first event is reported. There were 961 hospital survivors. Survival increased from 24.2% in 1987 to 33.4% in 1996 (chi(2)=39.0, df=1, P<0.0001). Survival was affected strongly by initial rhythm (chi(2)=420.0, df=1, P<0.0001) and decreased from 63.2% for supraventricular tachycardia (SVT) to 55.3% for ventricular tachycardia (VT), 51.0% for perfusing rhythms (PER), 34.8% for ventricular fibrillation (VF), 14.3% for pulseless electrical activity (PEA) and 10.0% for asystole (ASYS). PEA was the most frequent rhythm (1180 cases) followed by perfusing (963), asystole (580), VF (459), VT (94) and SVT (38). DISCUSSION: the powerful effect of initial rhythm on survival has been reported in pre-hospital and in-hospital resuscitation. VF is considered the dominant rhythm and generally accounts for the most survivors. We report good outcome for each; however, VF represents only 13.8% of events and 16.7% of survivors. PEA accounts for more survivors (169) than does VF (160). Our improved outcome is partially explained by changes in rhythms, but other institutional variables need to be identified to fully explain the results. Further studies are needed to see if our findings can be sustained or replicated.     

Outcome of out-of-hospital cardiac arrest--why do physicians withhold resuscitation attempts?

OBJECTIVE: To describe the outcome of out-of-hospital cardiac arrest (OHCA) with a focus on why physicians withhold resuscitation attempts. METHODS: Prospective collection of data during 12 months by the anaesthesiologists from the Advanced Life Support unit (ALS) of the Emergency Medical Service (EMS) according to the Utstein template. RESULTS: In total, 499 OHCA were analysed and 266 patients received cardiopulmonary resuscitation (CPR) by the ALS unit. Initial rhythm was ventricular fibrillation (VF)/pulseless ventricular tachycardia (VT) in 35%, asystole in 38%, and other rhythm in 27%. Of the 266 treated patients, 83 (31%) patients had a spontaneous circulation on admission to hospital. Survival to discharge from hospital was 6.2% for all cases of OHCA, 11.7% for all 266 treated patients, and 20.5% for patients with witnessed cardiac arrest and presumed cardiac aetiology in VF. On arrival, the physician decided in 233 cases to withhold or discontinue CPR. The explanation for this was prolonged anoxia (74%), terminal cancer (8%), and severe trauma (7%). The most common incident locations were the patient's home and nursing homes. These locations were more common in the group where resuscitation was not attempted and these patients were older and the proportions of females and asystole were significantly higher. Bystander CPR was provided in 82 (16%) overall, but only in 8 (3%) in the group where resuscitation was not attempted. CONCLUSION: Survival to discharge from hospital in all cases of OHCA was 6.2% but 20.5% in witnessed, presumed cardiac aetiology in VF. The decision to withhold resuscitation was based upon presumed prolonged anoxia in the majority of cases.     

Treatment of asystole and PEA

Recent reports consistently point to a substantial decline in the incidence of ventricular fibrillation (VF) as the initial rhythm observed by Emergency Medical Service (EMS) responders and a complementary increase in pulseless electrical activity (PEA) and asystole. Historically, efforts at improving survival have focused primarily on patients found in VF. Consequently, the approach for other patients has included frequent pauses in cardiopulmonary resuscitation (CPR) to check for VF followed by shock when VF is observed. However, the “yield” of survivors comes largely from the non-shocked patients. Therefore, it is critical that we start evaluating treatments specifically for the PEA and asystole groups.     

Difference in end-tidal CO2 between asphyxia cardiac arrest and ventricular fibrillation/pulseless ventricular tachycardia cardiac arrest in the prehospital setting

IntroductionThere has been increased interest in the use of capnometry in recent years. During cardiopulmonary resuscitation (CPR), the partial pressure of end-tidal carbon dioxide (PetCO₂) correlates with cardiac output and, consequently, it has a prognostic value in CPR. This study was undertaken to compare the initial PetCO₂ and the PetCO₂ after 1 min during CPR in asphyxial cardiac arrest versus primary cardiac arrest.MethodsThe prospective observational study included two groups of patients: cardiac arrest due to asphyxia with initial rhythm asystole or pulseless electrical activity, and cardiac arrest due to acute myocardial infarction or malignant arrhythmias with initial rhythm ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT). The PetCO₂ was measured for both groups immediately after intubation and then repeatedly every minute, both for patients with and without return of spontaneous circulation (ROSC).ResultsWe analyzed 44 patients with asphyxial cardiac arrest and 141 patients with primary cardiac arrest. The first group showed no significant difference in the initial value of the PetCO₂, even when we compared those with and without ROSC. There was a significant difference in the PetCO₂ after 1 min of CPR between those patients with ROSC and those without ROSC. The mean value for all patients was significantly higher in the group with asphyxial arrest. In the group with VF/VT arrest there was a significant difference in the initial PetCO₂ between patients without and with ROSC. In all patients with ROSC the initial PetCO₂ was higher than 10 mmHg.ConclusionsThe initial PetCO₂ is significantly higher in asphyxial arrest than in VT/VF cardiac arrest. Regarding asphyxial arrest there is also no difference in values of initial PetCO₂ between patients with and without ROSC. On the contrary, there is a significant difference in values of the initial PetCO₂ in the VF/VT cardiac arrest between patients with and without ROSC. This difference could prove to be useful as one of the methods in prehospital diagnostic procedures and attendance of cardiac arrest. For this reason we should always include other clinical and laboratory tests.     

The characteristics of postcountershock pulseless electrical activity may indicate the outcome of CPR

OBJECTIVES: When ventricular fibrillation is cardioverted to pulseless electrical activity (PEA), PEA has been regarded as a non-resuscitatable rhythm. Yet, recent reports and our earlier observations suggested otherwise. We therefore investigated outcomes after postcountershock PEA, and aimed to develop a scoring system for outcome classification at the onset of initial postcountershock PEA. METHODS: Data from 215 domestic pigs were retrospectively reviewed. VF was induced and untreated for 7 min. Defibrillation was attempted with up to three 150 J biphasic shocks. Failing to restore spontaneous circulation (ROSC), 1 min of CPR preceded subsequent sequences of shocks until animals were resuscitated or for a total of 15 min. Fifty-nine instances of PEA followed defibrillation, including 29 animals that attained ROSC. RESULTS: ROSC animals required a shorter interval between the first shock and the initial postcountershock PEA, fewer shocks prior to onset of initial postcountershock PEA, demonstrated a greater VF wavelet amplitude prior to onset of initial PEA, smaller QRS intervals, and higher heart rates. Using Fisher's linear discriminant analysis, 79.3% of the ROSC and 63.3% of non-ROSC cases were predicted correctly. A total of 71.2% of all cases were classified correctly. CONCLUSIONS: Animals in which postcountershock PEA was converted to ROSC required shorter intervals from first shock to initial postcountershock PEA, fewer shocks prior to onset of initial postcountershock PEA, had greater VF wavelet amplitude prior to initial postcountershock PEA, small QRS intervals, and higher heart rates. Fisher's discriminant analysis is helpful in predicting the likelihood of ROSC for an individual animal presenting with postcountershock PEA.     

Improving the rate of return of spontaneous circulation for out-of-hospital cardiac arrests with a formal, structured emergency resuscitation team

OBJECTIVE: To assess the impact of a formal, structured resuscitation team in the emergency department (ED) on the success rate of cardiopulmonary resuscitation (CPR) for out-of-hospital cardiac arrest (OHCA) patients. METHODS: This is a "three-phase" (organized, transitional, and re-organized), prospective study in which medical records of all OHCA patients who needed resuscitation in the ED during the three 6-month periods were reviewed and data were coded in out-of-hospital Utstein style formats. An organized resuscitation team existed in the organized and re-organized phases but not in the transitional phase. The study population consisted of adult patients with non-traumatic cardiac arrest (>18 years of age). RESULTS: The rates of return of spontaneous circulation (ROSC) were 51.3% for the organized phase, 31.0% for the transitional phase, and 53.1% for the re-organized phase ( P=0.013 ). The rates of ROSC from pulseless electrical activity (PEA)/asystole were significantly higher in periods with organized and re-organized teams ( P=0.007 ). The rates of ROSC for the ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT) sub-groups were not significantly different in all three periods ( P=0.406 ). The chance of survival-to-discharge was 9.2% in the organized period, 11.2% in the transitional period, and 15.6% in the re-organized period ( P=0.496 ). The existence of a formal, structured emergency resuscitation team in the ED (odds ratio: 2.56, 95% confidence interval: 1.35-4.80) and witness at the scene (odds ratio: 2.45, 95% confidence interval: 1.34-4.45) were the only independent predictors of successful ROSC of OHCA patients by multiple logistic regression analysis. CONCLUSION: The establishment of a formal and structured emergency resuscitation team in the ED is associated with an increased rate of ROSC for OHCA patients.     

山莨菪碱对心搏骤停大鼠复苏的影响

目的 观察山莨菪碱对心搏骤停大鼠自主循环恢复(ROSC)及复苏成功率的影响,旨在探寻心肺复苏的新方法.方法 采用盲法将45只成年SD大鼠随机分为对照组、肾上腺素组和肾上腺素+山莨菪碱组(联用组),每组15只.实验采用经食道心脏起搏诱发心室纤颤或心室静止,使用电动机械胸外按压机进行胸外按压.盲法给药,肾上腺素剂量200 μg/kg,山莨菪碱为10 mg/kg,对比各组ROSC率及复苏成功率.结果 联用组ROSC率(93.3%比46.7%)、复苏成功率(80.0%比33.3%)及3 h存活率(83.3%比20.O%)均高于肾上腺素组,差异有统计学意义(P均<0.05);对照组仅1只大鼠ROSC.ROSC即刻肾上腺素组平均动脉压(MAP)明显高于联用组(P<0.05);ROSC后两组MAP均呈逐渐下降趋势,且自5 min开始,肾上腺素组MAP明显低于联用组,至ROSC后30 min,两组比较差异仍有统计学意义(P均<0.05).结论 肾上腺素合用山莨菪碱可以提高心搏骤停ROSC率和复苏成功率.