Monophasic versus biphasic transthoracic countershock after prolonged ventricular fibrillation in a swine model

OBJECTIVE: We sought to compare the defibrillation efficacy of a low-energy biphasic truncated exponential (BTE) waveform and a conventional higher-energy monophasic truncated exponential (MTE) waveform after prolonged ventricular fibrillation (VF). BACKGROUND: Low energy biphasic countershocks have been shown to be effective after brief episodes of VF (15 to 30 s) and to produce few postshock electrocardiogram abnormalities. METHODS: Swine were randomized to MTE (n = 18) or BTE (n = 20) after 5 min of VF. The first MTE shock dose was 200 J, and first BTE dose 150 J. If required, up to two additional shocks were administered (300, 360 J MTE; 150, 150 J BTE). If VF persisted manual cardiopulmonary resuscitation (CPR) was begun, and shocks were administered until VF was terminated. Successful defibrillation was defined as termination of VF regardless of postshock rhythm. If countershock terminated VF but was followed by a nonperfusing rhythm, CPR was performed until a perfusing rhythm developed. Arterial pressure, left ventricular (LV) pressure, first derivative of LV pressure and cardiac output were measured at intervals for 60 min postresuscitation. RESULTS: The odds ratio of first-shock success with BTE versus MTE was 0.67 (p = 0.55). The rate of termination of VF with the second or third shocks was similar between groups, as was the incidence of postshock pulseless electrical activity (15/18 MTE, 18/20 BTE) and CPR time for those animals that were resuscitated. Hemodynamic variables were not significantly different between groups at 15, 30 and 60 min after resuscitation. CONCLUSIONS: Monophasic and biphasic waveforms were equally effective in terminating prolonged VF with the first shock, and there was no apparent clinical disadvantage of subsequent low-energy biphasic shocks compared with progressive energy monophasic shocks. Lower-energy shocks were not associated with less postresuscitation myocardial dysfunction.     

Treatment of prolonged ventricular fibrillation. Immediate countershock versus high-dose epinephrine and CPR preceding countershock.

BACKGROUND. Early countershock of ventricular fibrillation has been shown to improve immediate and long-term outcome of cardiac arrest. However, a number of investigations in the laboratory and in the clinical population indicate that immediate countershock of prolonged ventricular fibrillation most commonly is followed by asystole or a nonperfusing spontaneous cardiac rhythm, neither of which rarely respond to current therapy. The use of epinephrine in doses greater than those currently recommended has recently been shown to improve both cerebral and myocardial perfusion during cardiopulmonary resuscitation (CPR). The purpose of this study was to compare cardiac resuscitation outcome between immediate countershock of prolonged ventricular fibrillation with high-dose epinephrine therapy and conventional CPR before countershock of prolonged ventricular fibrillation in a canine model. METHODS AND RESULTS. After sedation, intubation, induction of anesthesia, and instrumentation, ventricular fibrillation was electrically induced in 28 dogs. After 7.5 minutes of ventricular fibrillation, animals were randomly allocated to two treatment groups: group 1, immediate countershock followed by recommended advanced cardiac life support (ACLS) interventions, or group 2, 0.08 mg/kg epinephrine and manual closed-chest CPR before countershock and ACLS. In both groups, ACLS was continued until a spontaneous perfusing rhythm was restored or for 20 minutes (total arrest time, 27.5 minutes). A spontaneous perfusing rhythm was restored in three of 14 group 1 animals and in nine of 14 group 2 animals (p = 0.014 by sequential analysis method of Whitehead). Coronary perfusion pressure (aortic minus right atrial pressure during CPR diastole) before countershock was significantly greater in group 2 (21 +/- 7 mm Hg) when compared with mean circulatory pressure in group 1 (9 +/- 8, p less than 0.01). CONCLUSIONS. The findings of this study suggest that a brief period of myocardial perfusion before countershock improves cardiac resuscitation outcome from prolonged ventricular fibrillation.     

Bystander-initiated cardiopulmonary resuscitation in the management of ventricular fibrillation.

We assessed the influence of bystander-initiated cardiopulmonary resuscitation upon outcome in 316 consecutive patients treated for out-of-hospital ventricular fibrillation. Of 109 patients who received bystander-initiated cardiopulmonary resuscitation, 47 (43%) were ultimately discharged home. Of 207 patients for whom resuscitation was delayed until arrival of fire department personnel, 43 (21%) survived (P less than 0.001). Improved survival was largely due to a reduction in subsequent hospital mortality rather than to a higher rate of initially effective resuscitation. In a separate analysis of 118 patients treated at a single institution after resuscitation, the reduced hospital mortality reflected a decrease in deaths due to shock and to anoxic encephalopathy. In addition, neurologic dysfunction was significantly less common if bystanders had initiated cardiopulmonary resuscitation. Bystander participation in cardiopulmonary resuscitation represents an important adjunct to a rapid-response emergency care system.     

Precountershock cardiopulmonary resuscitation improves ventricular fibrillation median frequency and myocardial readiness for successful defibrillation from prolonged ventricular fibrillation: a randomized,controlled swine study

STUDY OBJECTIVE: After prolonged ventricular fibrillation (VF), precountershock cardiopulmonary resuscitation (CPR) will improve myocardial "readiness" for defibrillation compared with immediate defibrillation. METHODS: After 10 minutes of untreated VF, 32 swine (27+/-1 kg) were randomly assigned to receive immediate countershocks (DEFIB), CPR for 3 minutes followed by countershocks (CPR), or CPR for 3 minutes plus intravenous epinephrine followed by countershocks (CPR+EPI). VF waveform was evaluated by fast Fourier transformation. RESULTS: VF amplitude and median frequency by fast Fourier transformation decreased during the untreated VF interval in all groups, and the median frequency subsequently increased during each minute of precountershock CPR. Although the VF median frequency in the 3 groups did not differ after 10 minutes of untreated VF (8.9+/-0.8 Hz versus 8.4+/-0.5 Hz versus 7.3+/-0.5 Hz, respectively), immediately before the first shock the VF median frequency was much lower in the DEFIB group than in either the CPR or CPR+EPI groups (8.9+/-0.8 Hz versus 13.1+/-0.8 Hz versus 13.8+/-0.9 Hz, respectively; P <.01). None of the 10 animals in the DEFIB group attained return of spontaneous circulation after the first set of shocks versus 5 of 10 animals in the CPR group and 6 of 12 animals in the CPR+EPI group (DEFIB versus each CPR group; P <.05). Cardiac output 1 hour after resuscitation was substantially worse in the DEFIB group than in the CPR or CPR+EPI groups (74+/-7 mL/kg per minute versus 119+/-7 mL/kg per minute versus 104+/-15 mL/kg per minute; P <.05). CONCLUSION: Precountershock CPR can result in substantial physiologic benefits compared with immediate defibrillation in the setting of prolonged VF. Moreover, these benefits can be attained with or without the addition of intravenous epinephrine.     

Effect of bystander initiated cardiopulmonary resuscitation on ventricular fibrillation and survival after witnessed cardiac arrest outside hospital.

OBJECTIVE--To describe the proportion of patients who were discharged from hospital after witnessed cardiac arrest outside hospital in relation to whether a bystander initiated cardiopulmonary resuscitation. PATIENTS--All patients with witnessed cardiac arrest outside hospital before arrival of the ambulance and in whom cardiopulmonary resuscitation was attempted by the emergency medical service in Gothenburg during 1980-92. RESULTS--Cardiopulmonary resuscitation was initiated by a bystander in 18% (303) of 1,660 cases. In this group 69% had ventricular fibrillation at first recording compared with 51% in the remaining patients (P < 0.001). Among patients in whom cardiopulmonary resuscitation had been initiated by a bystander 25% were discharged alive versus 8% of the remaining patients (P < 0.001). Independent predictors of survival were in order of significance: initial arrhythmia (P < 0.001), interval between collapse and arrival of first ambulance (P < 0.001), cardiopulmonary resuscitation initiated by a bystander (P < 0.001), and age (P < 0.01). Among patients who were admitted to hospital alive 30% of patients in whom cardiopulmonary resuscitation had been initiated by a bystander compared with 58% of remaining patients (P < 0.001) had brain damage and died in hospital. Corresponding figures for death in association with myocardial damage were 18% and 29% respectively (P < 0.01). CONCLUSIONS--Cardiopulmonary resuscitation initiated by a bystander maintains ventricular fibrillation and triples the chance of surviving a cardiac arrest outside hospital. Furthermore, it seems to protect against death in association with brain damage as well as with myocardial damage.     

Sustained consciousness during ventricular fibrillation: Case report of cough cardiopulmonary resuscitation

A 54-year-old male developed ventricular fibrillation during right coronary angiography. Cough cardiopulmonary resuscitation was performed for 30 sec allowing the patient to remain alert and hemodynamically stable. Cough cardiopulmonary resuscitation is a simple, often overlooked technique that can be utilized during resuscitation in the cardiac catheterization laboratory. © 1996 Wiley-Liss, Inc.     

心肺复苏电除颤前抢救措施的对比研究

目的 探讨住院心脏骤停患者心肺复苏电除颤前的更有效措施。方法 选择住院心脏骤停患者113例,根据心肺复苏电除颇前采取的不同措施分为两组,一组为电除颤前给予人工通气,包括口对口人工呼吸和气管插管加胸外心脏按压,称常规组,共44例,男36例,女8例,年龄35-67岁,平均54±11岁;另一组为电除颤前给予单纯胸外心脏按压,称观察组,共69例,男性56例,女性13例,年龄34-77岁,平均56±12岁。结果 常规组复苏成功21例,成功率为47.7%,出院存活15例,出院存活率为34.1%;观察组复苏成功48例,成功率为69.6%,出院存活33例,出院存活率为55.1%;两组复苏成功率和出院率分别进行相比,P值均相似文献   

Three-phase model of cardiac arrest: time-dependent benefit of bystander cardiopulmonary resuscitation

Evidence has suggested that the pathophysiology of ventricular fibrillation cardiac arrest may consist of 3 time-sensitive phases: electrical, circulatory, and metabolic. We performed a retrospective cohort study of adults in a metropolitan county who had had witnessed ventricular fibrillation arrest before emergency medical services were undertaken to investigate this 3-phase model with regard to bystander cardiopulmonary resuscitation (CPR). We hypothesized that the survival benefit from bystander CPR depends on the collapse-to-shock interval, with the highest benefit occurring during the circulatory phase. The collapse-to-shock interval was a priori grouped into 4 categories: 1 to 5, 6 to 7, 8 to 10, and > or = 11 minutes. We used logistic regression analysis to assess whether the association between CPR and survival to hospital discharge depended on the collapse-to-shock interval category. Of the 2,193 events meeting the inclusion criteria, 67.0% had received bystander CPR. The average collapse-to-shock interval was 8.2 +/- 2.8 minutes. The survival rate was 33.4%. A higher likelihood of survival was associated with bystander CPR (odds ratio [OR] 1.41, 95% confidence interval [CI] 1.15 to 1.73) and a shorter collapse-to-shock interval (OR -1.84, 95% CI 1.62 to 2.10, for each additional SD of 2.8 minutes less) after adjustment. The beneficial association of CPR increased as the collapse-to-shock interval increased (p = 0.05 for interaction). The bystander CPR was associated with an OR of survival of 0.96 (95% CI 0.64 to 1.46) for a 1- to 5-minute collapse-to shock interval, OR of 1.25 (95% CI 1.00 to 1.58) for a 6- to 7-minute interval, OR of 1.62 (95% CI 1.25 to 2.11) for an 8- to 10-minute interval, and OR of 2.11 (95% CI 1.32 to 3.37) for an > or = 11-minute interval. The results of this investigation support a phased model of ventricular fibrillation arrest. The findings suggest that the transition from the electrical to circulatory phase may occur at about 5 minutes, and the circulatory phase may extend to 15 minutes.     

Coronary blood flow during cardiopulmonary resuscitation in swine

Recent papers have raised doubt as to the magnitude of coronary blood flow during closed-chest cardiopulmonary resuscitation. We will describe experiments that concern the methods of coronary flow measurement during cardiopulmonary resuscitation. Nine anesthetized swine were instrumented to allow simultaneous measurements of coronary blood flow by both electromagnetic cuff flow probes and by the radiomicrosphere technique. Cardiac arrest was caused by electrical fibrillation and closed-chest massage was performed by a Thumper (Dixie Medical Inc., Houston). The chest was compressed transversely at a rate of 66 strokes/min. Compression occupied one-half of the massage cycle. Three different Thumper piston strokes were studied: 1.5, 2, and 2.5 inches. Mean aortic pressure and total systemic blood flow measured by the radiomicrosphere technique increased as Thumper piston stroke was lengthened (mean +/- SD): 1.5 inch stroke, 23 +/- 4 mm Hg, 525 +/- 195 ml/min; 2 inch stroke, 33 +/- 5 mm Hg, 692 +/- 202 ml/min; 2.5 inch stroke, 40 +/- 6 mm Hg, 817 +/- 321 ml/min. Both methods of coronary flow measurement (electromagnetic [EMF] and radiomicrosphere [RMS]) gave similar results in technically successful preparations (data expressed as percent prearrest flow mean +/- 1 SD): 1.5 inch stroke, EMF 12 +/- 5%, RMS 16 +/- 5%; 2 inch stroke, EMF 30 +/- 6%, RMS 26 +/- 11%; 2.5 inch stroke, EMF 50 +/- 12%, RMS 40 +/- 20%. The phasic coronary flow signal during closed-chest compression indicated that all perfusion occurred during the relaxation phase of the massage cycle. We concluded that coronary blood flow is demonstrable during closed-chest massage, but that the magnitude is unlikely to be more than a fraction of normal.