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Biomedical subjects

W Barrington

Publications and source records attributed to W Barrington.

11 recordsLinked to original sources
PubMed2005

Trigeminal uptake and clearance of inhaled manganese chloride in rats and mice.

Inhaled manganese (Mn) can enter the olfactory bulbs via the olfactory epithelium, and can then be further transported trans-synaptically to deeper brain structures. In addition to olfactory neurons, the nasal cavity is innervated by the maxillary division of the trigeminal nerve that projects to the spinal trigeminal nucleus. Direct uptake and transport of inhaled metal particles in the trigeminal system has not been investigated previously. We studied the uptake, deposition, and clearance of soluble Mn in the trigeminal system following nose-only inhalation of environmentally relevant concentrations. Rats and mice were exposed for 10-days (6 h/day, 5 days/week) to air or MnCl2 aerosols containing 2.3 +/- 1.3 mg/m3 Mn with mass median aerodynamic diameter (MMAD) of 3.1 +/- 1.4 microm for rats and 2.0 +/- 0.09 mg/m3 Mn MnCl2 with MMAD of 1.98 +/- 0.12 microm for mice. Mn concentrations in the trigeminal ganglia and spinal trigeminal nucleus were measured 2 h (0-day), 7-, 14-, or 30-days post-exposure using proton induced X-ray emission (PIXE). Manganese-exposed rats and mice showed statistically elevated levels of Mn in trigeminal ganglia 0-, 7- and 14-days after the 10-days exposure period when compared to control animals. The Mn concentration gradually decreased over time with a clearance rate (t1/2) of 7-8-days. Rats and mice were similar in both average accumulated Mn levels in trigeminal ganglia and in rates of clearance. We also found a small but significant elevation of Mn in the spinal trigeminal nucleus of mice 7-days post-exposure and in rats 0- and 7-days post-exposure. Our data demonstrate that the trigeminal nerve can serve as a pathway for entry of inhaled Mn to the brain in rodents following nose-only exposure and raise the question of whether entry of toxicants via this pathway may contribute to development of neurodegenerative diseases.

Administration, Inhalation↗
PubMed2000

Potential risk of vasovagal syncope for motor vehicle driving.

Vasovagal syncope is the most common cause of syncope, but its risk for driving remains uncertain. We analyzed the clinical characteristics of patients who had syncope during driving and subsequently underwent the head-up tilt test (HUTT). Of the 245 consecutive patients undergoing HUTT, 23 (9%) had > or =1 episode of syncope during driving. HUTT was positive in 19 (group A) and negative in 4 (group B) patients. No patient had structural heart disease. In group A, the driving incident occurred on the first syncope in 3 patients, and the other 16 patients had 1 to 4 episodes of prior syncope not associated with driving. In group B, the driving incident occurred on the first syncope in 1 patient, and the other 3 patients had prior syncope (3 episodes in each) not associated with driving. Seven group A and 1 group B patients had 2 syncope-related driving incidents, and the remaining patients had only 1 syncope-related driving incident. The syncope-related driving incidents caused personal injury in 7 group A and 2 group B patients. One incident in 1 group A patient caused the death of another driver. After HUTT, all but 1 patient in group A received medical treatment and only 1 patient in group B received empirical beta-blocker therapy. During the follow-up of 51+/-26 months, 1 patient died and another was lost to follow-up. Of the remaining patients, 4 patients had recurrence of syncope and 2 patients had presyncope in group A. One of these patients had another syncope-related driving incident. No group B patient had syncope recurrence. A second etiology of syncope was never found in any patient. We conclude that vasovagal syncope during driving is not uncommon in patients referred for syncope evaluation. Early medical attention to patients with vasovagal syncope may help reduce syncope-related driving incidents.

Adolescent↗
PubMed1998

Evaluation and management of atrial fibrillation in the emergency department.

AF is the most common sustained cardiac arrhythmia. Recognition and appropriate management of AF is important to optimize care of concurrent medical problems and prevent long-term consequences. DC cardioversion under sedation should be performed in patients with pulmonary edema, angina, or hypotension. Ventricular rate control is the first choice in stable patients with rapid ventricular rate. Anticoagulation should be considered in all patients with AF duration < 48 hours, except for those under 65 years old and having no other risk factors of stroke. Recent data imply that early attempts at cardioversion may increase success rates and decrease AF recurrence rates. Thus, transesophageal echocardiogram-guided early cardioversion may become more widely used.

Adrenergic beta-Antagonists↗
PubMed1998

The mean ventricular fibrillation cycle length: a potentially useful parameter for programming implantable cardioverter defibrillators.

In programming the implantable cardioverter defibrillator (ICD), the ventricular tachycardia (VT) detection cycle length (CL) is based on the CL of the documented tachycardia but the ventricular fibrillation (VF) detection CL is set arbitrarily. Appropriate programming of VF detection may not only reduce the incidence of inappropriate ICD shocks for non-VF rhythms but can also avoid the fatal underdetection of VF. The mean VFCL may provide a useful parameter for optimal ICD programming for VF detection if it is reproducible. This study examined the intrapatient reproducibility and interpatient variation of the mean VFCL in 30 ICD patients (25 men and 5 women, mean age 63 +/- 13 years). A total of 210 VF episodes (7 +/- 4 per patient, range 3-17) induced by T-wave shocks (166) or AC (44) at the ICD implant (30 patients) and the predischarge test (12 of 30 patients) were analyzed. The mean VFCL was calculated from the stored V-V intervals in the ICDs. Although the mean VFCL varied significantly from 171 +/- 6 to 263 +/- 11 ms (P < 0.01) among different patients, it was reproducible among different VF episodes in an individual patient (maximal variation 4-50 ms, P > 0.05). The mean VFCL was not significantly different between patients with and without antiarrhythmic drugs (210 +/- 32 vs 210 +/- 23 ms, P > 0.05) and was correlated with the ventricular effective refractory period (r = 0.5, P < 0.05). The mean VFCL varies greatly among different patients but remains reproducible in an individual patient, suggesting that the mean VFCL may serve as a reference for ICD programming of VF detection.

Adult↗
PubMed1996

Long distance transmission of diagnostic cardiovascular information.

Availability of advanced cardiac diagnostic procedures has proven to decrease the morbidity and mortality associated with common cardiovascular diseases. It was requested that the University of Nebraska Medical Center (UNMC) provide a rural hospital with advanced cardiology services. The services included monitoring of inpatients and rapid interpretation of cardiac diagnostic tests. UNMC proposed to solve this problem by building a computer-based system to transmit diagnostic cardiac information from a rural hospital to UNMC for interpretation by a cardiologist. The information transmitted to UNMC was grouped into two categories: 1) cardiovascular ultrasound, 2) ambulatory and 12-lead electrocardiograms. The information consisted of digital and analog waveform information, static images, and 30 fps video. The system provided rapid data transmission to UNMC over a T-1 line. The system utilized a compression technology which did not degrade the interpretation quality of the data. This system has increased the availability of advanced cardiac diagnostic services to general medical practitioners in a rural hospital. In addition, the system has significantly reduced the time and cost to transmit vital cardiac diagnostic information, thus improving the quality of care received by rural patients.

Cardiovascular Diseases↗
PubMed1985

Effect of acute standing and prolonged upright activity on left ventricular hemodynamics, systolic and diastolic intervals, and QT-QS2 relationship.

It is generally accepted that upright posture decreases preload and afterload, which could alter left ventricular (LV) performance. It is not known if changes occurring with acute standing persist after prolonged ambulatory activity (amb-act). In seven normal subjects echocardiographic end-diastolic and end-systolic diameters, percent shortening of the internal diameter (% delta D) and end-systolic wall stress (ES-WS), radionuclide diastolic volume and ejection fraction, preejection period over left ventricular ejection time (PEP/LVET), and diastolic time and QT-QS2 were measured supine, within 1 to 2 minutes after standing and after prolonged (60 minutes) amb-act. In addition, serial measurements were performed in PEP/LVET for 105 minutes at 15-minute intervals. With acute standing, end-diastolic diameter, diastolic volume, and ES-WS decreased (p less than 0.01); heart rate and PEP/LVET increased (p less than 0.01); while % delta D and ejection fraction remained unchanged. There was an inverse correlation between change in PEP/LVET and diastolic diameter (r = -0.59), but no correlation between PEP/LVET and ES-WS. The diastolic time per beat and per minute decreased (375 +/- 115 msec from 519 +/- 176 msec [p less than 0.01] and 31.3 +/- 4.2 sec/min from 33.7 +/- 4.5 sec/min [p less than 0.01]). The QT-QS2 increased when compared to supine (-7 +/- 7.6 msec from -22 +/- 7.7 msec [p less than 0.005]), but the QT-QS2 relationship remained normal (QT less than or equal to QS2). All the dynamic changes that occurred with acute standing tended to persist during prolonged amb-act.

Adult↗