Methodology-dependent Variation in Documentation of Outcome Predictors in Out-of-hospital Cardiac Arrest

Objective: To identify variation in outcome predictor documentation in out-of-hospital cardiac arrest associated with two different methods of data collection: concurrent questioning of personnel following a resuscitation attempt and archival report review.
Methods: All patients ≤ 18 years old who had had out-of-hospital cardiac arrests, verified using the New York City 911 telephone system, between October 1, 1990, and April 1, 1991, were eligible for inclusion. The authors reviewed the first 200 cases of presumed primary cardiac arrest involving a resuscitation attempt from among 3,243 consecutive ambulance call reports for cardiac arrest occurring during the study period. This archival data set was compared with data for the same 200 cases gathered through direct interview of field personnel by trained paramedics. The two data sets had been compiled independently by different individuals, using the same data collection instrument, which conformed to the Utstein template.
Results: Comparison of the data obtained from ambulance records with the data obtained from interviews of prehospital personnel revealed several areas of variance. Of note was a significantly lower proportion of bystander-witnessed ventricular fibrillation (VF) in the data set gathered from written reports (7% vs 18%; 95% CI for the difference 4–18%; p = 0.001).
Conclusion: Differences in methods of collection of out-of-hospital cardiac arrest data are associated with a more than twofold variation in the reported incidences of witnessed cardiac arrests manifesting as VF. Methodology-dependent variation in this important "denominator" may produce substantially different estimates of survival within the same cohort of patients.     

Determining the best approach to reduce the impact of exercise-induced atrial fibrillation: prevention,screening, or symptom-based treatment?

Introduction: Regular endurance exercise over the course of many years appears to increase the risk of atrial fibrillation (AF). These data challenge the notion that the benefits of physical activity have no appreciable limits. The incidence of exercise-induced AF is expected to increase as a consequence of the popularity of extreme endurance sports. Actions to reduce its impact are warranted.

Areas covered: This review focuses on exercise-induced AF and reviews the existing data regarding the prevention, screening, and treatment of this disease, with the aim of elucidating the best options for this group of patients.

Expert commentary: To date, strategies to deal with exercise-induced AF are unsatisfactory. Improved knowledge of AF pathology and better classification schemes are needed to address current pitfalls.     

Response Time Effectiveness:Comparison of Response Time and Survival in an Urban Emergency Medical Services System

Emergency medical services (EMS) administrators seek methods to enhance system performance. One component scrutinized is the response time (RT) interval between call receipt and arrival on scene. While reducing RTs may improve survival, this remains speculative and unreported. OBJECTIVE: To determine the effect of current RTs on survival in an urban EMS system. METHODS: The study was conducted in a metropolitan county (population 620,000). The EMS system is a single-tier, paramedic service and provides all service requests. The 90% fractile RT specifications required for county compliance include 10:59 minutes for emergency life-threatening calls (priority I) and 12:59 minutes for emergency non-life-threatening calls (priority II). All emergency responses resulting in a priority I or priority II transport to a Level 1 trauma center emergency department over a six-month period were evaluated to determine the relation between specified and arbitrarily assigned RTs and survival. RESULTS: Five thousand, four hundred twenty-four transports were reviewed. Of these, 71 patients did not survive (1.31%; 95% CI = 1.04% to 1.67%). No significant difference in median RTs between survivors (6.4 min) and nonsurvivors (6.8 min) was noted (p = 0.10). Further, there was no significant difference between observed and expected deaths (p = 0.14). However, mortality risk was 1.58% for patients whose RT exceeded 5 minutes, and 0.51% for those whose RT was under 5 minutes (p = 0.002). The mortality risk curve was generally flat over RT intervals exceeding 5 minutes. CONCLUSIONS: In this observational study, emergency calls where RTs were less than 5 minutes were associated with improved survival when compared with calls where RTs exceeded 5 minutes. While variables other than time may be associated with this improved survival, there is little evidence in these data to suggest that changing this system's response time specifications to times less than current, but greater than 5 minutes, would have any beneficial effect on survival.     

Risks and methods for peripheral blood progenitor cell collection in small children.

Peripheral blood progenitor cells (PBPC) are increasingly used as a source of stem cells for either autologous or allogeneic hematopoietic transplantation in children. Although technically similar to adult procedures, apheresis in small children worries some operators and physicians that have little experience in managing pediatric patients or donors. However several published series have showed that these procedures, when performed by experienced teams are safe and can obtain enough amount of PBPC for either autologous or allogeneic hematopoietic transplantation. Some technical aspects must be considered in pediatric apheresis due to the size of the patient/donor. Factors that must be evaluated are extracorporeal circuit volume, blood flow rates, type of anticoagulant and vascular access. Other important issue to be considered is the emotional stress for them and their relatives. Leukaphereses in children may be performed with any of the reported continuous blood cell separator without sedation. Adverse events are mainly related either to vascular access or to metabolic or hemodynamic changes. Anyway, taking all these complications together, they are not higher than those adverse events or toxicities reported after general anesthesia and bone marrow harvesting.     

Energy-dependent accumulation of norfloxacin and porin expression in clinical isolates of Klebsiella pneumoniae and relationship to extended-spectrum beta-lactamase production

The relationships between porin deficiency, active efflux of fluoroquinolones, and extended-spectrum beta-lactamase (ESBL) production were determined for 53 clinical isolates of Klebsiella pneumoniae. Thirty-two ESBL-positive strains (including 22 strains expressing porins and 10 strains lacking porins) and 21 ESBL-negative strains were evaluated. Active efflux of norfloxacin was defined as a >/=50% increase in the accumulation of norfloxacin in the presence of carbonyl cyanide m-chlorophenylhydrazone (CCCP) in comparison with the corresponding basal value in the absence of CCCP. The quinolone resistance-determining regions of both gyrA and parC from 13 strains, representing all isolates with different porin profiles and with or without active efflux, were determined. Porin loss was significantly more common among ESBL-positive strains (10 of 32 [31.2%]) than among ESBL-negative strains (0 of 2 [0%]) (P < 0.01). Active efflux was observed in 7 of 10 (70%) strains lacking porins and in 4 of 43 (9.3%) strains producing porins (P < 0.001). The 11 strains showing active efflux corresponded to 3 of 21 (14.3%) ESBL-negative strains and 8 of 32 (25.5%) ESBL-positive strains (P > 0.05). Basal values of norfloxacin accumulation were higher in strains lacking active efflux than in those that had this mechanism (P < 0.05). In the absence of topoisomerase changes, the contribution of either porin loss or active efflux to fluoroquinolone resistance in K. pneumoniae was negligible. It is concluded that among K. pneumoniae strains of clinical origin, porin loss was observed only in those producing ESBL, and that a significant number of porin-deficient strains also expressed active efflux of norfloxacin. In terms of fluoroquinolone resistance, both mechanisms are significant only in the presence of topoisomerase modifications.     

Sublingual Nitroglycerin Delays Arterial Wave Reflections Despite Increased Aortic “Stiffness” in Patients with Hypertension: A Doppler Echocardiography Study

Venodilatation with consequent reduction in left ventricular filling and end-diastolic wall stress is an important mechanism for the beneficial effects of nitroglycerin in ischemic heart disease and in left ventricular failure. The effects of sublingual nitroglycerin on arterial pulsatile hemodynamics are less well defined. Doppler echocardiography and the calibrated subclavian artery pulse tracing were used to assess hemodynamics in subjects with sustained arterial hypertension (n = 25) before and 5 to 10 minutes after sublingual deposition of 0.5 mg glyceryl trinitrate. Aortic characteristic impedance was calculated by averaging the modulus of the input impedance (ratio of pressure to flow) at high frequencies and by calculating the ratio of pressure and flow increments during upstroke. The pressure wave was split into forward and backward components, and the reflection coefficient (the ratio of backward to forward pressures) was calculated. Parameters of the arterial bed were estimated by using 2- and 3-element Windkessel models. Nitroglycerin delayed the return of arterial wave reflections by 17% (P =.02) and increased aortic characteristic impedance by 20% (P =. 01), but it did not influence total arterial compliance. Mean arterial pressure decreased 7% (P =.0001), but pulse pressure did not change. Stroke volume and the acceleration time of aortic root flow decreased by 13% (P =.0001) and 8% (P =.01), respectively. Cardiac output decreased 7% (P =.01), despite an increase in heart rate of 10% (P =.0001). Peripheral resistance tended to decrease (4%, P =.06). Thus, in subjects with sustained hypertension, sublingual nitroglycerin dilates peripheral, predominantly muscular arteries with a subsequent delayed return of reflected pressure waves. Reflex activation of the sympathetic nervous system with consequent increased acceleration of left ventricular ejection seems to counteract the effect of reduced mean arterial pressure (distending pressure) with respect to the "stiffness" of the aorta.     

Interferon-gamma and tumor necrosis factor-alpha specifically induce formation of cytomegalovirus-permissive monocyte-derived macrophages that are refractory to the antiviral activity of these cytokines.

Monocytes/macrophages are key cells in the pathogenesis of human cytomegalovirus (HCMV). Although HCMV infection in monocytes is restricted to early events of gene expression, productive infection has been demonstrated in differentiated macrophages in vitro. We examined the cellular and cytokine components that are essential for HCMV replication in Concanavalin A-stimulated monocyte-derived macrophages (MDM). By negative selection, depletion of CD8+ T lymphocytes, but not CD4+ T lymphocytes, CD19+ B cells, or CD56+ NK cells, resulted in a 60-70% reduction in the number of HCMV-infected MDM, and a 4 log decrease in virus production. Neutralization of IFN-gamma and TNF-alpha, but not IL-1, IL-2, or TGF-beta, decreased production of virus by 4 logs and 2 logs, respectively. Subsequently, addition of recombinant IFN-gamma or TNF-alpha to purified monocyte cultures was sufficient to produce HCMV-permissive MDM. While IFN-gamma and TNF-alpha possess antiviral properties, addition of these cytokines to permissive MDM cultures did not affect production of HCMV. Thus, rather than inhibiting replication of HCMV, IFN-gamma and TNF-alpha specifically induce differentiation of monocytes into HCMV-permissive MDM, which are resistant to the antiviral effects of these cytokines.