Out-of-hospital cardiac arrest is a common and lethal problem, with an estimated 330,000 deaths each year in North America alone. Even in those cases where help arrives in a timely fashion, outcomes remain dismal with estimates of survival to hospital discharge ranging from 3.0% to 16.3%.\u00a0 Compounding the situation is the difficulty associated with conducting high quality research in the setting of cardiac arrest, therefore many therapies and guidelines are based on evidence of variable quality and expert consensus only.\u00a0 Two recently published trials using overlapping patient cohorts attempt to ameliorate this situation by conducting large population based trials to guide best practice.<\/p>\n
In the first of these the authors examined whether the recent change in guidelines to recommend a 2 minute period of cardiopulmonary resuscitation (CPR) before rhythm analysis provides a benefit over brief CPR and early analysis. A total of 9933 patients were studied of whom 5290 were assigned to early analysis and 4643 to later analysis.\u00a0 The primary outcome was survival to hospital discharge with satisfactory functional status (a modified Rankin scale score of \u22643).\u00a0 In total 273 patients (5.9%) in the later-analysis group and 310 patients (5.9%) in the early-analysis group met the primary outcome, with a cluster-adjusted difference of -0.2 percentage points (95% CI, -1.1 to 0.7; P=0.59) demonstrating equipoise between the two strategies. Analyses of the data with adjustment for confounding factors, as well as subgroup analyses, also showed no survival benefit for either study group.<\/p>\n
In the second study, the authors examined an impedance threshold device (ITD) which is designed to enhance venous return and cardiac output during CPR by increasing the degree of negative intrathoracic pressure and has been shown to be efficacious in animal studies.\u00a0 In this case recruiting 8718 patients, 4345 were randomly assigned to treatment with a sham ITD and 4373 to an active device with the primary end-point being identical to that in the first study. This time 260 patients (6.0%) in the sham-ITD group and 254 patients (5.8%) in the active-ITD group met the primary outcome (risk difference adjusted for sequential monitoring, -0.1 % points; 95% CI, -1.1 to 0.8; P=0.71).\u00a0 There were also no significant differences in the secondary outcomes, including rates of return of spontaneous circulation on arrival at the emergency department, survival to hospital admission, and survival to hospital discharge.<\/p>\n
Conclusions<\/strong><\/p>\n Among patients with out-of-hospital cardiac arrest neither a delayed versus early rhythm analysis strategy, nor the use of an impedance threshold device, improved survival to hospital discharge with satisfactory functional status.\u00a0 Despite these disappointing outcomes, these studies provide high quality evidence to shape future resuscitation guidelines.<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" Out-of-hospital cardiac arrest is a common and lethal problem, with an estimated 330,000 deaths each year in North America alone. Even in those cases where help arrives in a timely fashion, outcomes remain dismal with estimates of survival to hospital discharge ranging from 3.0% to 16.3%.\u00a0 Compounding the situation is the difficulty associated with conducting […]<\/p>\n\n