Todd M. Larabee

A randomized controlled trial comparing the Arctic Sun to standard cooling for induction of hypothermia after cardiac arrest

CONTEXT Hypothermia improves neurological outcome for comatose survivors of out-of-hospital cardiac arrest. Use of computer controlled high surface area devices for cooling may lead to faster cooling rates and potentially improve patient outcome. OBJECTIVE To compare the effectiveness of surface cooling with the standard blankets and ice packs to the Arctic Sun, a mechanical device used for temperature management. DESIGN, SETTING, AND PATIENTS Multi-center randomized trial of hemodynamically stable comatose survivors of out-of-hospital cardiac arrest. INTERVENTION Standard post-resuscitative care inducing hypothermia using cooling blankets and ice (n=30) or the Arctic Sun (n=34). MAIN OUTCOME MEASURES The primary end point was the proportion of subjects who reached a target temperature within 4h of beginning cooling. The secondary end points were time interval to achieve target temperature (34 degrees C) and survival to 3 months. RESULTS The proportion of subjects cooled below the 34 degrees C target at 4h was 71% for the Arctic Sun group and 50% for the standard cooling group (p=0.12). The median time to target was 54 min faster for cooled patients in the Arctic Sun group than the standard cooling group (p<0.01). Survival rates with good neurological outcome were similar; 46% of Arctic Sun patients and 38% of standard patients had a cerebral performance category of 1 or 2 at 30 days (p=0.6). CONCLUSIONS While the proportion of subjects reaching target temperature within 4h was not significantly different, the Arctic Sun cooled patients to a temperature of 34 degrees C more rapidly than standard cooling blankets.

Females of childbearing age have a survival benefit after out-of-hospital cardiac arrest

BACKGROUND There is controversy regarding the association between age and being female and survival to hospital discharge after out-of-hospital cardiac arrest (OHCA). We hypothesized that younger females (aged 12-49 years) would be independently associated with increased survival after OHCA when compared to other age and sex groups. METHODS We conducted a secondary analysis of prospectively collected data from 29 United States cities that participate in the Cardiac Arrest Registry to Enhance Survival (CARES). Patients were included if they were ≥12 years of age and had a documented resuscitation attempt from October 1, 2005 through December 31, 2009. Hierarchical multivariable logistic regression analyses were used to estimate the associations between age and sex groups and survival to hospital discharge. RESULTS Females were less likely to have a cardiac arrest in public, was witnessed, or was treatable with defibrillation. Females in the 12-49 year old age group had a similar proportion of survival to hospital discharge when compared to age-matched males (females 11.6% vs. males 11.2%), while males ≥50 years old were more likely to survive when compared to age matched females (females 6.9% vs. males 9.6%). Age stratified regression models demonstrated that 12-49 year old females had the largest association with survival to hospital discharge (OR 1.55, 95% CI 1.20-2.00), while females in the ≥50 year old age group had a smaller increased odds of survival to hospital discharge (OR 1.18, 95% CI 1.03-1.35), which only lasted until the age of 55 years (OR 1.12, 95% CI 0.97-1.29). CONCLUSIONS Younger aged females were associated with increased odds of survival despite being found with poorer prognostic arrest characteristics.

A swine model of pseudo-pulseless electrical activity induced by partial asphyxiation

BACKGROUND The incidence of pulseless electrical activity (PEA) as a presenting rhythm during cardiac arrest is increasing. The current animal models of PEA arrest, post-countershock or total asphyxiation, unreliably generate PEA for a specific time period. Neither of these models predictably generate pseudo-PEA. The purpose of this study was to create an animal model of pseudo-PEA that will allow for a prolonged time period in this arrest state for future research. METHODS In a laboratory setting, five ventilated swine on inhaled anesthesia and 100% oxygen with continuous EKG recordings were instrumented with central aortic and venous pressure-transducing catheters. Animals were then switched to intravenous anesthesia while being ventilated with a 16% oxygen/84% nitrogen mix. Continuous EKG, aortic and venous pressures were recorded to a computerized data collection program. Arterial blood gas samples were taken every 10min. Time until onset of pseudo-PEA, duration of pseudo-PEA, and cardiac rhythm during pseudo-PEA were recorded. RESULTS Mean time to onset of pseudo-PEA was 80.6+/-47.3min. Mean duration of pseudo-PEA was 18.6+/-6.2min. Mean arterial pH at pseudo-PEA onset was 7.20+/-0.05 with a mean associated base excess of -11.4+/--5.94. No significant differences were noted in other recorded variables. CONCLUSIONS Partial asphyxiation using a 16% oxygen/84% nitrogen mix is a reliable laboratory method to create a prolonged state of pseudo-PEA in a swine model. The mechanism generating pseudo-PEA is hypoxemia-induced systemic acidosis. This model will allow sufficient time in this low-flow cardiac state for future research to be conducted.

A novel hands-free carotid ultrasound detects low-flow cardiac output in a swine model of pulseless electrical activity arrest

OBJECTIVE To determine if a hands-free, noninvasive Doppler ultrasound device can reliably detect low-flow cardiac output by measuring carotid artery blood flow velocities. We compared the ability of observers to detect carotid artery flow velocity differences between pseudo-pulseless electrical activity (PEA) and true-PEA cardiac arrest. METHODS Five swine were instrumented with aortic (Ao) and right atrial pressure-transducing catheters. The Doppler ultrasound device was adhered to the neck over the carotid artery. Continuous electrocardiogram, pressure readings, and Doppler signal were recorded. Each swine underwent multiple episodes of fibrillation and resuscitation. Episodes of true-PEA and pseudo-PEA were retrospectively identified from all resuscitation attempts by examination of electrocardiogram and Ao waveforms. The sensitivity and specificity of the device to detect pseudo-PEA was obtained using observers blinded to Ao waveform recordings. RESULTS There was good interobserver reliability related to identification of pseudo- and true-PEA (κ = 0.873). The observers blinded to Ao waveform recordings agreed on 8 of the 9 episodes of pseudo-PEA, whereas 4 false positives of 26 true-PEA events were reported (sensitivity, 0.89; specificity, 0.85). The Doppler device was able to detect carotid flow velocity over a wide range of Ao blood pressures. CONCLUSIONS This hands-free, noninvasive Doppler ultrasound device can reliably differentiate pseudo-PEA from true-PEA during resuscitation from cardiac arrest, detecting pressure gradient changes of less than 5 mm Hg through to normotension. This device distinguishes conditions of no cardiac output from low cardiac output and may have applications for use during resuscitation from various etiologies of arrest and shock.

Self‐reported Financial Conflicts of Interest During Scientific Presentations in Emergency Medicine

OBJECTIVES This study was a review of the scientific abstracts presented at a national conference for the required conflict of interest (COI) disclosure both before the meeting and during presentation. METHODS All presenters were given specific instructions regarding COI reporting at the time of abstract acceptance. All poster presentations were required to have a COI statement. Three physicians using standardized data abstraction forms reviewed abstracts accepted for poster presentation at the 2010 annual meeting of the Society for Academic Emergency Medicine (SAEM). Posters were reviewed for the presence of a required COI disclosure statement, and these results were compared to the mandatory continuing medical education (CME) disclosure form that was sent by the presenters to the SAEM central office before the meeting. RESULTS There were 412 posters accepted for presentation at the 2010 SAEM annual meeting. The reviewers observed 382 (93%) of the total posters for the conference. Sixty-nine abstracts (18%) reported a COI. Only 26 (38%) of these were actually reported to the SAEM office on the CME disclosure form before the meeting; the remaining 62% were found on the poster alone. COI that were reported on the CME disclosure form were found on the poster 46% of the time. The remaining posters without a COI actually displayed the mandatory disclosure statement only 14% of the time. CONCLUSIONS This review of presentations at a national meeting found a lack of compliance with printed guidelines for COI disclosure during scientific presentation. Efforts to increase uniformity and clarity may result in increased compliance.