Biomedical subjects

Bruce Cameron

Publications and source records attributed to Bruce Cameron.

3 recordsLinked to original sources

PubMed2005

Out-of-hospital cardiac arrest rectilinear biphasic to monophasic damped sine defibrillation waveforms with advanced life support intervention trial (ORBIT).

BACKGROUND: Although biphasic defibrillation waveforms appear to be superior to monophasic waveforms in terminating VF, their relative benefits in out-of-hospital resuscitation are incompletely understood. Prior comparisons of defibrillation waveform efficacy in out-of-hospital cardiac arrest (OHCA) are confined to patients presenting in a shockable rhythm and resuscitated by first responder (basic life support). This effectiveness study compared monophasic and biphasic defibrillation waveform for conversion of ventricular arrhythmias in all OHCA treated with advance life support (ALS). METHODS AND RESULTS: This prospective randomized controlled trial compared the rectilinear biphasic (RLB) waveform with the monophasic damped sine (MDS) waveform, using step-up energy levels. The study enrolled OHCA patients requiring at least one shock delivered by ALS providers, regardless of initial presenting rhythm. Shock success was defined as conversion at 5s to organized rhythm after one to three escalating shocks. We report efficacy results for the cohort of patients treated by ALS paramedics who presented with an initially shockable rhythm who had not received a shock from a first responder (MDS: n=83; RLB: n=86). Shock success within the first three ascending energy shocks for RLB (120, 150, 200J) was superior to MDS (200, 300, 360J) for patients initially presenting in a shockable rhythm (52% versus 34%, p=0.01). First shock conversion was 23% and12%, for RLB and MDS, respectively (p=0.07). There were no significant differences in return of spontaneous circulation (47% versus 47%), survival to 24h (31% versus 27%), and survival to discharge (9% versus 7%). Mean 24h survival rates of bystander witnessed events showed differences between waveforms in the early circulatory phase at 4-10 min post event (mean (S.D.) RLB 0.45 (0.07) versus MDS 0.31 (0.06), p=0.0002) and demonstrated decline as time to first shock increased to 20 min. CONCLUSION: Shock success to an organized rhythm comparing step-up protocol for energy settings demonstrated the RLB waveform was superior to MDS in ALS treatment of OHCA. Survival rates for both waveforms are consistent with current theories on the circulatory and metabolic phases of out-of-hospital cardiac arrest.

Adult↗

PubMed2004

Neuronal nitric oxide synthase and N-methyl-D-aspartate neurons in experimental carbon monoxide poisoning.

We measured changes in nitric oxide (NO) concentration in the cerebral cortex during experimental carbon monoxide (CO) poisoning and assessed the role for N-methyl-d-aspartate receptors (NMDARs), a glutamate receptor subtype, with progression of CO-mediated oxidative stress. Using microelectrodes, NO concentration was found to nearly double to 280 nM due to CO exposure, and elevations in cerebral blood flow, monitored as laser Doppler flow (LDF), were found to loosely correlate with NO concentration. Neuronal nitric oxide synthase (nNOS) activity was the cause of the NO elevation based on the effects of specific NOS inhibitors and observations in nNOS knockout mice. Activation of nNOS was inhibited by the NMDARs inhibitor, MK 801, and by the calcium channel blocker, nimodipine, thus demonstrating a link to excitatory amino acids. Cortical cyclic GMP concentration was increased due to CO poisoning and shown to be related to NO, versus CO, mediated guanylate cyclase activation. Elevations of NO were inhibited when rats were infused with superoxide dismutase and in rats depleted of platelets or neutrophils. When injected with MK 801 or 7-nitroindazole, a selective nNOS inhibitor, rats did not exhibit CO-mediated nitrotyrosine formation, myeloperoxidase (MPO) elevation (indicative of neutrophil sequestration), or impaired learning. Similarly, whereas CO-poisoned wild-type mice exhibited elevations in nitrotyrosine and myeloperoxidase, these changes did not occur in nNOS knockout mice. We conclude that CO exposure initiates perivascular processes including oxidative stress that triggers activation of NMDA neuronal nNOS, and these events are necessary for the progression of CO-mediated neuropathology.

Animals↗

PubMed2002

An immersive simulation system for provoking and analyzing cataplexy.

Cataplexy, a sudden loss of voluntary muscle control, is one of the hallmark symptoms of narcolepsy, a sleep disorder characterized by excessive daytime sleepiness. Cataplexy is usually triggered by strong, spontaneous emotions, such as laughter, surprise, fear or anger, and is more common in times of stress. The Sleep Disorders Unit and the Biomedical Imaging Resource at Mayo Clinic are developing interactive display technology for reliably inducing cataplexy during clinical monitoring. The use of immersive displays may help bypass patient defenses, and game-like "unreality" allows introduction of surprising, threatening, or humorous elements, with little risk of offending patients. The project is referred to as the "Cataplexy/Narcolepsy Activation Program", or CatNAP. We have developed an automobile driving simulation to allow the introduction of humorous, surprising, or stress-inducing events and objects as the patient attempts to navigate a simulated vehicle through a virtual town. The patient wears a stereoscopic head-mounted display, by which he views the virtual town through the windows of his simulated vehicle. The vehicle is controlled via a driving simulator steering wheel and pedal cluster. The patient is instructed to drive his vehicle to another location in town, given initial directions and street signs. As he attempts to accomplish the task, various objects, sounds or conditions occur which may distract, startle, frustrate or cause laughter; responses which may trigger a cataplectic episode. The patient can be monitored by reflex tests and EMG recordings during the driving experience. An evaluation phase with volunteer patients previously diagnosed with cataplexy has been completed. The goal of these trials was to gain insight from the volunteers as to improvements that could be made to the simulation. All patients that participated in the evaluation phase have been under a physician's care for a number of years and control their cataplexy with medication. We believe this is a novel and innovative approach to a difficult problem. CatNAP is a compelling example of the potentially effective application of virtual reality technology to an important clinical problem that has resisted previous approaches. Preliminary results suggest that an immersive simulation system like CatNAP will be able to reliably induce cataplexy in a controlled environment. The project is continuing through a final stage of refinement prior to conducting a full clinical study.

Automobile Driving↗