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Biomedical subjects

R D White

Publications and source records attributed to R D White.

At least 91 records · Page 5Linked to original sources
PubMed1995

Health effects of inhaled tertiary amyl methyl ether and ethyl tertiary butyl ether.

Government specifications on the oxygen content of motor gasoline sold in certain areas of the USA have resulted in commercialization of the oxygenate fuel additives tertiary amyl methyl ether (TAME) and ethyl tertiary butyl ether (ETBE). TAME and ETBE were evaluated in 4-week rat inhalation studies sponsored by Amoco Corporation. Target vapor concentrations were 0, 500, 2000, or 4000 ppm for 6 h per day, 5 days per week, for 4 weeks. TAME exposure at 4000 ppm resulted in 25% mortality, apparently as a consequence of severe CNS depression. Body weight gain was decreased in the TAME high dose male rats. In contrast, no ETBE exposed animals died during the study and no changes in body weight gain were observed. Significant effects on functional observational battery (FOB) parameters were only found in the TAME high and mid-dose groups immediately after exposure. All affected FOB parameters were normal by the next day. Both TAME and ETBE exposures significantly increased relative liver weights in the high and mid-dose groups. However, no treatment-related histopathologic findings were noted for either compound. Clinical chemistry and hematology findings were absent with ETBE exposure and minimal with TAME exposure. The results indicate that 500 ppm was a NOAEL for both compounds in these studies.

Administration, Inhalation↗
PubMed1995

Ventricular fibrillation, automatic external defibrillators, and the United States Food and Drug Administration: confrontation without comprehension.

More people die in the United States each day of potentially reversible VF than of any other cause of death, reversible or not. Early defibrillation is the definitive treatment. Automated external defibrillation is a proven technology now confirmed to have saved thousands of lives. As with all medical devices and technology, perfection is not possible. Some problems, such as those represented by the two cases discussed in this article, are inevitable and acceptable and give little cause for alarm. One would not stop penicillin from being manufactured and distributed because of a sudden, unexpected allergic reaction in one patient (error of commission) or an unexpected resistant organism in another (error of omission). The FDA must understand that AEDs, even if they are imperfect, are not anywhere near as dangerous as no defibrillator at all. AEDs have finally allowed many EMS systems to achieve early defibrillation. Discontinuing use of AEDs or closing AED manufacturers could mean a significant number of lives lost unnecessarily. Therefore EMS agencies planning to implement early-defibrillation programs should continue with such plans. Why the agents of an important federal regulatory agency have singled out this technology for an intense review puzzles many observers in the medical-device field. Two meetings have been hosted by officials of the FDA to discuss the continuing concern the FDA officials have expressed over automated defibrillation technology. These meetings included representatives from the AHA, the American College of Cardiology, ACEP, defibrillator manufacturers, and other interested organizations. The FDA leadership has repeatedly focused on data acquired through the FDA Medical Device Reporting systems. Congress requires the FDA to investigate reports of problems with "critical medical devices." Because the indication for the use of a defibrillator is cardiac arrest, there will inevitably be a high association between defibrillator use and patient deaths. FDA personnel may view such reports of device problems in association with patient deaths as evidence that an intrinsically flawed technology has reached the marketplace without rigorous testing and evaluation. From the clinician's perspective, however, these reports represent a small numerator over a huge denominator of daily, lifesaving clinical use. The non-FDA participants at the two meetings have stated that the FDA complaints appear to be random and reveal a lack of understanding of AED technology.(ABSTRACT TRUNCATED AT 400 WORDS)

Algorithms↗
PubMed1995

Prognostic value of end-tidal carbon dioxide pressures during out-of-hospital cardiac arrest.

STUDY OBJECTIVE: To assess the prognostic value of initial end-tidal CO2 pressures (PETCO2) during CPR in patients with out-of-hospital cardiac arrest (OHCA). DESIGN: A prospective observational study using a convenience sample. SETTING: Primary service area of an advanced life support (ALS) ambulance service, including a city with a population of 70,745 and the surrounding area, with a population of 30,000. PARTICIPANTS: Adults with nontraumatic OHCA. INTERVENTIONS: Quantitative monitoring of PETCO2 during CPR after endotracheal intubation using an infrared capnograph. RESULTS: PETCO2 after 1 and 2 minutes and the maximum PETCO2 during CPR were compared between the group in which restoration of spontaneous circulation (ROSC) was achieved and the group in which it was not. PETCO2 was measured during CPR in 27 patients. After 1 minute, PETCO2 was higher in patients who had on-scene ROSC than in patients without ROSC (23.0 +/- 7.4 versus 13.2 +/- 14.7 mm Hg, P = .0002). After 2 minutes, PETCO2 was higher in patients with ROSC (26.8 +/- 10.8 versus 15.4 +/- 5.7 mm Hg, P = .0019). The maximum PETCO2 during CPR was also higher in the ROSC group (30.8 +/- 9.5 versus 22.7 +/- 8.8 mm Hg, P = .0154). Thirteen of 27 patients presented in ventricular fibrillation (VF). The 1-minute (24.3 +/- 6.8 versus 12.0 +/- 4.2 mm Hg, P = .0022), 2-minute (28.2 +/- 11.4 versus 12.4 +/- 4.3 mm Hg, P = .0088), and maximum (33.0 +/- 10.2 versus 20.6 +/- 11.1 mm Hg, P = .0316) PETCO2 values during CPR were all significantly higher in patients in VF with ROSC. CONCLUSION: In this observation study of 27 patients, initial PETCO2 during CPR with automated ventilation was prognostic for ROSC in patients with OHCA. Patients with ROSC have higher PETCO2 values after 1 and 2 minutes than do patients without ROSC.

Carbon Dioxide↗
PubMed1995

Temporomandibular joint considerations in orthognathic surgery.

The relationship between the temporomandibular joint and developmental jaw deformities is both undeniable as well as controversial as to its magnitude or importance. This article addresses the importance of a complete temporomandibular joint and orthognathic diagnostic work-up prior to the choice of either temporomandibular joint or orthognathic surgery. The surgical procedure is determined by the internal derangement that is present as well as its response to non-surgical care. The intraoperative techniques for handling the bony fragments, seating the condyle and rigid fixation techniques are also of utmost importance and are discussed for each of the orthognathic procedures. The postoperative physiotherapy is also discussed both for the temporomandibular joint patient as well as the orthognathic patient.

Humans↗
PubMed1994

Catalytic and immunochemical characterization of hepatic microsomal cytochromes P450 in beluga whale (Delphinapterus leucas).

Understanding the effects of environmental contaminants on cetaceans and other marine mammals will require information on the biochemistry of xenobiotic metabolism in these species. We characterized the hepatic microsomal cytochrome P450 system in beluga whales (Delphinapterus leucas) from the Canadian Arctic. The content of native P450 averaged 0.203 and 0.319 nmol/mg microsomal protein, cytochrome b5 content averaged 0.199 and 0.236 nmol/mg, and rates of NADPH-cytochrome c reductase were 79 and 76 nmol/min/mg, for females and males respectively. Ethoxyresorufin O-deethylase (EROD), pentoxyresorufin O-depentylase (PROD), and benzo[a]pyrene (BP) hydroxylase (AHH) activities were significantly greater in males than in females, and were highly correlated with one another (r2 between 0.853 and 0.912). HPLC analysis of in vitro BP metabolites revealed benzo-ring (7,8- and 9,10-) dihydrodiols, consistent with activation of this compound, as well as 4,5-dihydrodiol,3-OH-, 7-OH-, and 9-OH-BP and 1,6- and 3,6-quinones. Estradiol 2-hydroxylase activity did not differ between sexes, and rates did not correlate with those of the other activities. Antibodies against scup P450B (an apparent teleost CYP2B) and rat CYP2B1 did not recognize proteins in beluga liver microsomes, but there was a protein detected by antibodies to PB-inducible rabbit CYP2B4. Antibodies to ethanol and ketone-inducible rat CYP2E1 reacted with two proteins in beluga liver microsomes. Antibodies specific to hydrocarbon-inducible CYP1A1 and/or CYP1A2 forms showed a single protein band, apparently more closely related to CYP1A1. The content of CYP1A was fivefold greater in male than in female beluga. CYP1A content was highly correlated with EROD, PROD, and AHH activities, suggesting that this P450 form is a primary catalyst for these reactions in beluga. CYP1A content and activity were highly correlated with the concentrations in blubber of non-ortho and mono-ortho PCB congeners, compounds that induce CYP1A in other mammals. These results indicate that a CYP1A is a catalyst for the metabolism of aromatic hydrocarbon pollutants in the beluga whale, and strongly suggest that this protein is induced in these organisms by environmental contaminants, including PCBs. The results support the measurement of CYP1A expression as a biomarker of exposure to inducers in marine mammals. The full functional and evolutionary relationships of beluga CYP1A and of beluga proteins immunologically related to other P450 forms are uncertain.

Animals↗
PubMed1994

Right ventricular outflow tract ventricular tachycardia: detection of previously unrecognized anatomic abnormalities using cine magnetic resonance imaging.

OBJECTIVES: This study attempted to determine whether cine magnetic resonance imaging (MRI), because of its unique ability to image the right ventricle, detects abnormalities in patients with right ventricular outflow tract ventricular tachycardia. BACKGROUND: Right ventricular outflow tract ventricular tachycardia occurs in the absence of apparent structural heart disease. METHODS: We compared cine MRI scans in 22 patients with right ventricular outflow tract ventricular tachycardia, 16 subjects without structural heart disease and 44 patients with other cardiovascular diseases. Echocardiography was performed in 21 patients with ventricular tachycardia. RESULTS: All 22 patients with ventricular tachycardia had normal left ventricular function and no evidence of coronary artery disease. Cine MRI revealed right ventricular structural and wall motion abnormalities more often in patients with ventricular tachycardia (21 [95%] of 22) than in normal subjects (2 [12.5%] of 16, p < 0.0001) or patients without arrhythmia (17 [39%] of 44, p < 0.0001). The abnormalities in patients with ventricular tachycardia (fixed focal wall thinning, excavation, decreased systolic thickening) were located in the right ventricular outflow tract, whereas those in patients without arrhythmia were confined to the free wall. Cine MRI demonstrated abnormalities in patients with ventricular tachycardia more often than did echocardiography (21 [95%] of 22 vs. 2 [9%] of 21, respectively, p < 0.0001). CONCLUSIONS: Right ventricular outflow tract ventricular tachycardia was associated with focal structural and wall motion abnormalities of the right ventricular outflow tract that were detected more often by cine MRI than by other imaging modalities and were not present in patients without arrhythmia or in normal subjects.

Adult↗
PubMed1994

Subarachnoid hemorrhage: atypical presentation associated with rapidly changing cardiac arrhythmias.

Subarachnoid hemorrhage (SAH) typically presents with sudden onset of severe headache and is often associated with cardiac arrhythmias. The case of a patient with SAH in whom typical presenting signs and symptoms were absent is presented. This case was characterized by rapidly changing arrhythmias observed in the prehospital setting. The diversity and rapid evolution of arrhythmias can be attributed to the autonomic and electrolyte imbalances that often accompany SAH.

Arrhythmias, Cardiac↗
PubMed1994

Out-of-hospital quantitative monitoring of end-tidal carbon dioxide pressure during CPR.

STUDY OBJECTIVE: To assess the feasibility and potential usefulness of quantitative measurement of end-tidal carbon dioxide pressure (PETCO2) during out-of-hospital cardiac arrest. DESIGN: Emergency medical technician-paramedics (EMT-Ps) were instructed in the operation of a portable battery-powered capnograph, the sensor for which was attached to the endotracheal tube following intubation. This was a preliminary pilot study limited to defining feasibility and potential utility in a small group of patients. SETTING: City with population of 70,745 served by an advanced life support emergency medical services system. PARTICIPANTS: Initial group of four patients who experienced out-of-hospital cardiac arrest and who were treated by EMT-Ps trained in operation of the capnograph. INTERVENTIONS: As soon as possible following endotracheal intubation a mainstream sensor was connected to the endotracheal tube and digital and capnographic waveform data obtained for the remainder of the resuscitation. Data were stored in memory and subsequently retrieved for the entire event, with digital readings at eight-second intervals. RESULTS: Capnographic measurements were obtained immediately after endotracheal intubation in all four patients. The capnograph was operated without difficulty throughout the resuscitations. Changes in performance of chest compression or changes in cardiac rhythm were reflected immediately in changes in (PETCO2). Persistent excretion of carbon dioxide during pulselessness was observed in two patients, consistent with "pseudo-electromechanical dissociation." CONCLUSION: These preliminary pilot observations confirm the feasibility of quantitative capnography during out-of-hospital cardiac arrest and indicate that early institution of this noninvasive procedure may provide insight into pathophysiologic mechanisms such as pseudo-electromechanical dissociation and may also track changes in pulmonary blood flow during chest compressions or during spontaneous circulation.

Aged↗
PubMed1994

Early defibrillation by police: initial experience with measurement of critical time intervals and patient outcome.

STUDY OBJECTIVE: To assess the feasibility of consistent acquisition of precise and clinically important time intervals in a city police department defibrillation study. DESIGN: On a daily basis, clocks at 911 dispatch were synchronized with those at ambulance dispatch, and all clocks on all defibrillators were synchronized to this time. Times were obtained from recordings at dispatch centers and from defibrillator memory modules. SETTING: City with a population of 70,745 and an area of 30 square miles. PARTICIPANTS: All patients in ventricular fibrillation (VF) treated by police officers using semiautomated defibrillators. INTERVENTIONS: On receipt of a call at 911 dispatch, the nearest squad car was dispatched. If police arrived before the ambulance and a cardiac arrest was confirmed, the closest squad car with a defibrillator was dispatched. Police delivered up to three shocks before ambulance arrival. RESULTS: Of 44 patients in VF, 14 were initially treated by police. Seven of 14 regained a spontaneous circulation with police shocks and seven required additional advanced life support care for restoration of pulses. Ten of the 14 were discharged home. The 911 call-to-shock time interval was 4.9 +/- 1.3 minutes for the seven who regained a spontaneous circulation with police shocks and 6.1 +/- 0.7 minutes for the seven without restoration of pulses by police (P = .035, one-sided, two-sample t-test). CONCLUSION: Acquisition of precise times for determination of time intervals is feasible with a concerted effort to synchronize all clocks from which times are derived. Even small differences in call-to-shock time intervals appear to be critical determinants of restoration of a spontaneous circulation.

Aged↗
PubMed1994

Congenital abnormalities of the thoracic aorta presenting in the adult.

Congenital variations in the development of the thoracic aorta are common. Although there is a spectrum of disease in all age groups, arch anomalies that present in childhood and those that present in the adult tend to be of differing types. Imaging of the arch and its branches, the descending aorta, and the ductus arteriosus or ligamentum arteriosum define the morphology of the arch and permit a reasonable prediction of accompanying congenital heart disease and/or vascular ring.

Adult↗
PubMed1994

Right-to-left interatrial shunt causing platypnea after pneumonectomy. A recent experience and diagnostic value of dynamic magnetic resonance imaging.

Shortness of breath after pneumonectomy is a common finding that has multiple causes. We report the cases of two patients with shortness of breath on assuming an upright posture (platypnea) that followed pneumonectomy; these individuals developed right-to-left shunt across a patent foramen ovale (PFO) with normal right-sided intracardiac pressures. Both contrast echocardiography and magnetic resonance imaging (MRI), including a recently introduced dynamic ultrafast imaging technique, proved helpful in diagnosing this condition noninvasively.

Aged↗
PubMed1994

AED (automatic external defibrillators) algorithms. The "shocking" truth.

Automatic external defibrillators (AEDs) have proven to be successful tools against sudden cardiac death since the 1970s. They operate on a simple premise--using a device with a built-in algorithm in a computer chip to "read" a persons's electrocardiogram (ECG) and, if necessary, advise or deliver a shock to bring the person back to a normal rhythm. When first introduced, these devices used various methods of collecting ECG's and detecting ventricular fibrillation (v fib) and ventricular tachycardia (v tach), two treatable dysrhythmias.

Algorithms↗
PubMed1994

Performing the exercise test.

With proper training, exercise testing is a useful diagnostic procedure for the primary care physician in the outpatient as well as the inpatient setting. By careful pretest evaluation, one is able to study patients safely and to obtain both diagnostic and prognostic information concerning the risk for cardiovascular disease.

Exercise Test↗
PubMed1993

Fixation method useful for cytologic examination and DNA flow cytometry of exfoliated bladder cells.

Single-institution studies have shown that DNA flow cytometry is superior to routine cytologic evaluation of following patients for bladder cancer recurrence. For 15 urine and 15 bladder washing specimens, we evaluated a fixative employing methanol plus acetic acid (MA), freshly mixed 20:1 (vol/vol). Routine cytologic evaluation following Papanicolaou staining, and DNA flow cytometry were performed. Paired aliquots from the same washings and urines were processed as fresh spray-fixed samples and MA-fixed samples. The majority of the MA-fixed specimens showed good nuclear preservation when assessed for chromatin texture, presence of distinct nuclear envelope, and clarity of nucleolus, while only a minority of the fresh urine and washing samples showed these features. Cytoplasmic degeneration was seen only in fresh specimens. The presence of aneuploidy and the percentage of hyperdiploid cells could be reliably determined in the MA-fixed samples. This fixation protocol is recommended for the transport of urine and bladder washing specimens to centralized laboratories for both cytologic and flow cytometric evaluation.

Acetates↗