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Biomedical subjects

E Austin

Publications and source records attributed to E Austin.

8 recordsLinked to original sources
PubMed1991

Is defibrillation testing safe?

Determination of defibrillation thresholds (DFTs) and implantable cardioverter defibrillator (ICD) testing requires repeated inductions of ventricular fibrillation (VF) and defibrillation attempts using known energy outputs. Little is known about the individual and cumulative effects of repetitive brief episodes of VF and hypoperfusion on cerebral function. The potential clinical utility of quantitative electroencephalographic (QEEG) monitoring during intraoperative ICD testing, by using processed 19-channel EEG (0.5-35 Hz bandwidth), was examined in ten anesthetized patients, five males and five females (mean age 62 +/- 10 years), who underwent ICD implantation and testing. Ischemic QEEG patterns were defined as those with a 3 standard deviation increase (P less than 0.01) in absolute delta (1.5-3.5 Hz) power persisting for greater than or equal to 2.5 minutes. The majority (80%) of the VF episodes (70) were accompanied by QEEG "slowing" (doubling of the pre-VF low frequency delta waves amplitude). All the patients (5/5) experiencing greater than 6 VF episodes showed a statistically significant increase in the low frequency amplitude. In contrast, this EEG abnormality was apparent in only one of five patients experiencing less than 6 VF episodes. These results suggest a cumulative QEEG depression associated with ICD testing. QEEG may provide an objective means for establishing an individualized upper safe limit of DFT testing and the total number of induced VF episodes.

Electric Countershock↗
PubMed1991

The initial clinical experience with an implantable cardioverter defibrillator/antitachycardia pacemaker.

Guardian antitachycardia pacing (ATP) 4210 is a third generation, multi-programmable cardioverter defibrillator undergoing Phase I clinical trials. The tiered response includes ATP, low energy cardioversion or defibrillation, and bradycardia support. Extensive telemetry is available, including an episode log and details of all episode events. Five patients underwent the implantation of Guardian ATP 4210 as part of a Phase I trial at the University of Louisville. Two of the five patients had multiple VT episodes that were reverted successfully using ATP pacing (slow VT) and defibrillation (fast VT) and VF episodes, which resulted in defibrillation therapy over a follow-up period of 6 to 8 months. Four of the five patients required bradycardia support for bradyarrhythmias unassociated with ATP therapy or defibrillation and one patient required bradycardia support postdefibrillation therapy. The device design is microprocessor based and requires continuous interrogation of the microprocessor memory and checks of the validity of programmed parameters to continue its operation. When the safety check fails, the device is designed to shut down its antitachycardia and defibrillator functions. This design feature has a potential for leaving the patient unprotected if the device shuts down. Modification of this feature is required to ensure the device's long-term safety.

Aged↗
PubMed1988

The use of lasers in pediatric surgery.

This report is a condensation of the Fred McLoed Lecture given at the Annual Meeting of the Canadian Association of Paediatric Surgeons. It briefly cites the basic fundamentals of lasers, the characteristics of those used in surgery, and their delivery systems. The advantages of laser surgery include the sealing of blood vessels, lymphatics, and nerve ends when used for cutting. This results in a relatively dry field of surgery and less postoperative pain. There is reduced opportunity for contaminants in a clean wound, and no spreading of infection in a contaminated one. Surgery can be carried out in confined areas in a drier field of view, and can be brought to small areas by fiberoptic cables. Highly precise and localized microsurgery is possible. The use of lasers is indicated in operations where significant blood loss is expected and in patients with bleeding tendencies. It is useful in surgery for malignant disease and through highly infected tissue. Other general indications are discussed. Specific surgical procedures where lasers have been useful include treatment of hemangiomas, surgery of the tongue, repair of pectus excavatum, partial splenectomy and splenic repair, hepatic lobectomy and hepatic repair, and resection of adrenal tumors. Lasers have also been useful in partial nephrectomy, excision biopsy, revision or closure of ileostomy or colostomy, endorectal mucosectomy, posterior sagittal anorectoplasty, treatment of condyloma acuminata, burn wound debridement, and infected tissue debridement. Anticipated uses include vascular, biliary tract, and intestinal repair and anastomoses, and photodynamic therapy (PDT) of neoplasms.

Child↗
PubMed1979

A model for deposition of stable and unstable aerosols in the human respiratory tract.

A model has been developed for deposition of stable and unstable aerosols in the human respiratory tract. This model has the advantages of employing a realistic asymmetric lung model and utilizing actual breath curves. Results from the model are presented for normal and abnormal breath patterns for both stable and unstable particles. Insofar as comparison is possible, agreement between model calculations and experiment appears to be reasonable.

Aerosols↗
PubMed1978

Periplasmic localization of nicotinate phosphoribosyltransferase in Escherichia coli.

Nicotinate phosphoribosyltransferase (NAPRTase) in Escherichia coli mediates the formation of nicotinate mononucleotide, a direct precursor of nicotinamide adenine dinucleotide (NAD), from nicotinate and 5-phosphoribosyl-1-pyrophosphate. Specifically, NAPRTase contributes to NAD synthesis by utilizing intracellular nicotinate formed from NAD degradation products, which are recycled by NAD cycle enzymes and exogenous nicotinate when it is available. In previous studies, it has been tacitly assumed that almost all NAD cycle enzymes are localized in the cytoplasm of E. coli. The results of this investigation provide evidence that NAPRTase is a periplasmic (extracytoplasmic) enzyme. The osmotic shock of exponential-phase cells of E. coli K-12 and ML 308-225 resulted in the release of 63 to 72% and 42 to 48%, respectively, of the NAPRTase into the shock medium. In addition, when exponential cells of strains K-12 and ML 308-225 were converted into spheroplasts, 75 to 84% and 54 to 68%, respectively, of the enzyme was released into the spheroplast medium. Since previous estimates of the effective levels of NAPRTase present in putative repressed and derepressed E. coli cells appeared to be very low, a more convenient and accurate alternative method for the evaluation of NAPRTase in whole cells was developed. The results show that NAPRTase is subject only to a modest degree of enzyme repression. In addition, no evidence was found for the presence of a protein or low-molecular-weight inhibitor of the enzyme in repressed cells.

Cytoplasm↗
PubMed1977

Control of hepatic bleeding with microfibrillar collagen.

Microfibrillar (Avitene) is a new absorbable topical hemostatic agent whose mechanism of action is platelet entrapment and activation of platelet clotting factors. It adheres to moist tissue surfaces to form a firm, flexible hemostatic coagulum. It has been used clinically in 36 patients with hepatic bleeding of diverse etiology, including bleeding from the gallbladder fossa, lacerations, resectional surfaces, biopsy sites, capsular denudations, and hepatic tumors. Although not intended to control major hemorrhage were major vessel ligation or resection is properly indicated, its topical use for diffuse small vessel bleeding may be life-saving. It is exceptionally useful in such conditions as cirrhosis and in thrombocytopenic or thrombasthenic coagulopathies. One treatment failure out of 36 occurred.

Aged↗