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Biomedical subjects

K Davis

Publications and source records attributed to K Davis.

At least 253 records · Page 14Linked to original sources

Temporary closure of the abdominal wall by use of silicone rubber sheets after operative repair of ruptured abdominal aortic aneurysms.

Management of patients after operative repair of abdominal aortic aneurysms can be further complicated if primary closure of the abdominal wall cannot be technically accomplished or is associated with profound increases in intraabdominal and peak inspiratory pressures. We recently treated five patients with ruptured abdominal aortic aneurysms and one patient with a ruptured thoracoabdominal aneurysm whose abdominal incisions had to be closed with a Dacron reinforced, silicone sheet. All patients were hemodynamically unstable either at admission to the hospital or became so during operation. Four patients required the insertion of a silicone rubber sheet at the primary operation because of massive retroperitoneal hematoma or edema of the bowel wall or both. Incisions in two patients were closed primarily, but the patients required reexploration and secondary closure with silicone rubber sheets because of the development of marked increases in peak inspiratory pressures, intraabdominal pressures, and decreased urinary output. Four of the six patients subsequently underwent successful removal of the silicone rubber sheets with delayed primary closure of the abdominal wall, and two others died before removal. The patient with the ruptured thoracoabdominal aneurysm died on postoperative day 20 because of pulmonary sepsis but had a healed abdominal incision. The three surviving patients have been discharged. A silicone rubber sheet may be necessary for closure of the abdominal wall after repair of ruptured abdominal aortic aneurysm in patients where primary abdominal wall closure is impossible or where it results in compromise in respiratory or renal function.

Abdomen↗

Techniques of emergency ventilation: a model to evaluate tidal volume, airway pressure, and gastric insufflation.

We designed a model to evaluate the effectiveness of various noninvasive methods of ventilation. The upper airway was simulated with the head of a Resusci-Annie which was attached to a test lung. The esophagus and stomach were simulated with a Penrose drain connected to a rolling seal spirometer via a PEEP valve. Fifteen paramedic volunteers ventilated the model utilizing mouth-to-mouth, mouth-to-mask, bag-valve-mask, or portable field ventilator (Impact or HARV). Recording of tidal volume, gastric volume, and proximal and distal airway pressure was completed at three different levels of compliance. At normal compliance, all methods except the HARV met or exceeded American Heart Association standards. As compliance decreased, tidal volume fell and gastric insufflation increased. At a compliance of 0.02 L/cm H2O all methods failed to meet AHA standards and gastric insufflation volume equalled delivered tidal volumes for mouth-to-mouth and mouth-to-mask techniques. Mouth-to-mouth and mouth-to-mask techniques generated the largest tidal volumes but also created the largest volume of gastric insufflation. The Impact ventilator provided an acceptable tidal volume with minimal gastric insufflation. Our results suggest that mouth-to-mask ventilation with supplemental oxygen enrichment is the most efficient technique for non-invasive airway management.

Airway Resistance↗

Comparison of conventional mechanical ventilation and high-frequency ventilation. A prospective, randomized trial in patients with respiratory failure.

Acute respiratory failure (ARF) following trauma or sepsis has a mortality rate of 50% to 85%. The mainstays of treatment are mechanical ventilation and positive end-expiratory pressure (PEEP). In the past decade, many reports have claimed superiority of high frequency ventilation (HFV) in the treatment of ARF. We structured a prospective randomized trial of HFV versus conventional mechanical ventilation (CMV) in the treatment of acute respiratory failure. All patients admitted to the Surgical Intensive Care Unit (SICU) were eligible for the study. On admission patients identified for being at risk of developing acute respiratory failure were randomized to receive either HFV or CMV. Patients were treated to the same therapeutic endpoint (pH greater than 7.35, PaCO2 35 to 45 torr, PaO2/FIO2 greater than 225). Daily ventilatory support, fluid and drug requirements, and cardiopulmonary variables were recorded. One hundred thirteen patients were entered into the study. Of these, 100 completed the study (HFV n = 52, CMV n = 48) and 60 developed acute respiratory failure (HFV n = 32, CMV n = 28). Patients on HFV reached the therapeutic endpoint at a lower level of continuous positive airway pressure and mean airway pressure; however there were no differences in mortality, SICU days, hospital days, incidence of barotrauma, number of blood gases, or cardiovascular interventions. This report suggests that HFV offers no concrete advantages over CMV when applied in a prospective fashion for the treatment of acute respiratory failure.

Adult↗

Enzymatic profiles of 11 barophilic bacteria under in situ conditions: evidence for pressure modulation of phenotype.

Barophilic bacteria are microorganisms that grow preferentially (facultative barophiles) or exclusively (obligate barophiles) under elevated hydrostatic pressure. Barophilic bacteria have been isolated from a variety of deep-sea environments. Attempts to characterize these organisms have been hampered by a lack of appropriate methodologies. A colorimetric method for the detection of 19 constitutively expressed enzymes under in situ conditions of pressure and temperature has been devised, using a simple modification of the commercially available API ZYME enzyme assay kit. By using this method, enzyme profiles of 11 barophilic isolates, including an obligate barophile, were determined. Nine of the 10 facultatively barophilic isolates examined exhibited a change of phenotype in at least one enzyme reaction when tested at 1 atm (1 atm = 101.29 kPa), compared with results obtained under in situ pressure. The assay is simple and rapid and allows for direct determination of enzyme activity under conditions of high pressure and low temperature.

Atmospheric Pressure↗

Production of Escherichia coli-specific hybridomas by using gnotobiotic mice.

Monoclonal antibodies provide a rapid and specific means of direct detection of microorganisms in water and food samples. However, monoclonal antibodies specific for some bacteria are difficult to obtain; a good example of such a bacterium is Escherichia coli. Gnotobiotic BALB/c mice immunized with whole-cell preparations of heat-treated strains of E. coli and subjected to high-frequency antigen injection showed a significant increase in the number of specific hybridomas produced. Fusions obtained by using regular BALB/c mice immunized by using standard immunization protocols produced nonspecific hybridomas. Twenty-one stable hybridomas that did not cross-react with Klebsiella pneumoniae ATCC 13883 or Citrobacter freundii 1604770 were obtained from gnotobiotic mice. The bacterial strains were selected for the specificity tests because of their high cross-reactivity, which has been detected in previous fusion experiments. The method of immunization described here offers the potential of improving the production of highly specific hybridomas for bacteria which have been difficult to obtain.

Animals↗

Trauma to the lower abdomen.

Various aspects of trauma to the lower abdomen are discussed. The initial assessment, including appropriate diagnostic tests, are outlined. Principles of management of specific injuries and indications for operation are discussed.

Abdominal Injuries↗

Stability of morphine sulfate in infusion devices and containers for intravenous administration.

The stability of morphine sulfate in one brand of polyvinyl chloride (PVC) container, one brand of glass syringe, and two brands of disposable infusion devices was determined. Solutions of morphine sulfate 2 and 15 mg/mL were used to fill the PVC containers and drug administration devices. Stability was determined for both concentrations of morphine sulfate at room temperature (23-25 degrees C) and 4 degrees C in the PVC containers, glass syringes, and disposable infusion devices; stability was also determined at 31 degrees C in the disposable infusion devices. At 0, 1, 2, 4, 7, 12, and 15 days, portions of the solutions were removed and assayed in triplicate by a stability-indicating high-performance liquid chromatographic method. At each time point the drug-infusion fluid combinations were inspected visually for color changes and the presence of particulate matter, and pH was measured. Morphine sulfate 2 and 15 mg/mL remained stable for at least 12 days in all the containers and devices at each temperature tested. No substantial changes in the pH or physical appearance of the solutions were observed. Morphine sulfate can be repackaged in the disposable glass syringe, PVC container, and both disposable infusion devices for routine clinical use.

Chromatography, High Pressure Liquid↗

Stability of heroin hydrochloride in infusion devices and containers for intravenous administration.

The stability of heroin hydrochloride in various drug-administration devices was studied. Heroin hydrochloride was supplied as the bulk powder by the National Institute on Drug Abuse and in the formulated dosage form by Evans Medical, Ltd. Stability was determined at concentrations of 1 and 20 mg/mL at room temperature (23-25 degrees C) and at 4 degrees C in a polyvinyl chloride (PVC) bag, a disposable glass syringe, and two disposable infusion devices. Studies at both concentrations also were conducted at 31 degrees C in the disposable infusion devices. All experiments were conducted in triplicate. A validated, stability-indicating, high-performance liquid chromatography assay was used. Heroin hydrochloride remained stable for a minimum of 15 days in the PVC bag and the Infusor infusion device at the tested temperatures and concentrations. In the glass syringe, heroin hydrochloride was shown to be stable for a minimum of 15 days at both 1 mg/mL and 20 mg/mL if refrigerated at 4 degrees C, whereas at room temperature it was stable for a minimum of 7 days at 1 mg/mL and for 12 days at 20 mg/mL. In the Intermate 200 infusion device, heroin hydrochloride was stable for a minimum of 15 days at both concentrations and all temperatures except for the 1 mg/mL concentration at 31 degrees C. In the latter case, stability was for a minimum of two days. No substantial changes in physical appearance or pH were observed in any of the containers under the conditions studied. Heroin hydrochloride can be repackaged in the disposable glass syringe, PVC bag, and each of the disposable infusion devices for routine clinical use.

Chromatography, High Pressure Liquid↗

Risk factor profiles of patients with sudden cardiac death and death from other cardiac causes: a report from the Coronary Artery Surgery Study (CASS).

Identification of patients at risk of sudden death is essential if optimal preventive treatment strategies are to be developed. In the Coronary Artery Surgery Study (CASS) Registry, 19,946 patients were analyzed to characterize baseline clinical, hemodynamic and angiographic features of patients dying from sudden cardiac death and to compare them with features of patients dying from other cardiac causes, of those dying from noncardiac causes and of survivors. Of the 11,843 medically treated patients, 1,621 died during a mean follow-up period of 5.0 years: death was sudden in 557 (34%), nonsudden but cardiac in 813 (50%) and noncardiac in 251 (16%). In 8,103 surgically treated patients, 824 deaths occurred during a mean follow-up period of 5.1 years: death was sudden in 204 (25%), nonsudden but cardiac in 390 (47%) and noncardiac in 230 (28%). In general, the patients (both medically and surgically treated) who died of cardiac causes, either suddenly or nonsuddenly, were similar to each other but significantly different from patients who either survived or died of noncardiac causes. Although patients with an increased risk of any type of cardiac death could be identified, there were no measures of angiographic or hemodynamic characteristics that were significantly different between patients with sudden cardiac death and those with nonsudden cardiac death. Identification of patients at high risk for sudden cardiac death will require approaches in addition to clinical, angiographic and hemodynamic assessment, such as electrophysiologic assessment or monitoring techniques to identify triggering mechanisms.

Coronary Disease↗

Effect of alkaline pH on photosynthetic water oxidation and the association of extrinsic proteins with Photosystem Two.

Incubation of a membrane preparation enriched in Photosystem Two (PSII) at alkaline pH inhibited the water-splitting reactions in two distinct steps. Up to pH 8.5 the inhibition was reversible, whereas at higher alkalinities it was irreversible. It was shown that the reversible phase correlated with loss and rebinding of the 23 kDa extrinsic polypeptide. However, after mild alkaline treatments a partial recovery was possible without the binding of the 23 kDa polypeptide when the assay was at the optimal pH of 6.5 and in a medium containing excess Cl-. The irreversible phase was found to be closely linked with the removal of the 33 kDa extrinsic protein of PSII. Treatments with pH values above 8.5 not only caused the 33 kDa protein to be displaced from the PSII-enriched membranes, but also resulted in an irreversible modification of the binding sites such that the extrinsic 33 kDa protein could not reassociate with PSII when the pH was lowered to 6.5. The results obtained with these more extreme alkaline pH treatments support the notion that the 23 kDa protein cannot bind to PSII unless the 33 kDa protein is already bound. The differential effect of pH on the removal of the 23 kDa and 33 kDa proteins contrasted with the data of Kuwabara & Murata [(1983) Plant Cell Physiol. 24, 741-747], but this discrepancy was accounted for by the use of glycerol in the incubation media.

Electron Transport↗

Prognostic indicators in head and neck cancer patients receiving combined therapy.

In 1983 we initiated a prospective nonrandomized study of the value of preoperative chemotherapy in previously untreated patients with stages III and IV squamous cell carcinoma of the head and neck. In 1983 and 1984, 50 patients were entered in the study. Prior to therapy all patients were evaluated by a representative from the Medical Oncology, Radiation Therapy, and Head and Neck Surgery Divisions, University of Utah School of Medicine, Salt Lake City. In addition to the standard preoperative evaluation, pretreatment computed tomographic scans were performed on all patients. Follow-up computed tomographic scans were performed after the second cycle of chemotherapy and at the completion of treatment. Initial therapy in all patients consisted of induction chemotherapy with cisplatin (day 1, 100 mg/m2) and fluorouracil (days 1 through 5, 1000 mg/m2). Several factors were examined for their utility in predicting response to therapy and survival. Factors evaluated included: (1) extent and timing of chemotherapeutic response; (2) computed tomographic quantitated primary tumor size; (3) size of computed tomographic quantitated regional (neck) metastases; (4) performance status; (5) cancer stage; (6) total lymphocyte count; and (7) serum liver function tests. The factor found to be most useful in predicting improved survival was the extent of response to chemotherapy. The remaining factors, performance status, regional lymph node status, serum gamma-glutamyltransferase levels, and cancer stage, were also found to correlate with length of survival but were much less important than the response to chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗

Cardiopulmonary effects of pressure support ventilation.

Pressure support ventilation (PSV) is a newer mode of ventilatory support that augments the patient's spontaneous inspirations to a preselected peak inspiratory pressure. We studied the effects of adding low levels of PSV (5 to 10 cm H2O) in conjunction with intermittent mandatory ventilation (IMV) on 15 patients who required mechanical ventilation for flail chest and pulmonary contusion. Patients were selected for the study if, during weaning from IMV, the following criteria were met: (1) a PaCO2 level greater than 45 mm Hg, (2) a spontaneous respiratory rate (RR) greater than 30 breaths per minute, (3) a minute ventilation (VE) greater than 9.0 L/min, and (4) spontaneous tidal volumes (VT) of less than 2 mL/kg. The PSV was added to the IMV at a level that augmented spontaneous VT to greater than 4 mL/kg. An average of 9 +/- 3 cm H2O of pressure support resulted in a fall in the level of PaCO2 (50 +/- 4 to 43 +/- 5 mm Hg), spontaneous RR (36 +/- 5 to 16 +/- 3 breaths per minute), VE (12 +/- 2 to 8.4 +/- 1.5 L/min), and dead space-tidal volume ratio from (0.68 +/- 0.1 to 0.47 +/- 0.05). Mean airway pressure and PaO2 both increased, but these changes were not statistically significant. Oxygen consumption was also unchanged. These results suggest that in patients who are difficult to wean due to respiratory muscle fatigue (characterized by increasing RR and decreasing VT), PSV normalizes lung volumes, improves ventilation, and may expedite the weaning process.

Adult↗

A flow cytometric approach to assessing the environmental and physiological status of phytoplankton.

Individual particle analysis using a flow cytometer (FCM) was made on natural phytoplankton communities in oligotrophic waters. Our objective was to develop an assay to yield information on the nutrient history of individual cells using FCM. Results from nutrient assays showed that both biovolume and total red fluorescence are affected by the nutrient conditions in the incubator. The light effect was measured by changes in the chlorophyll content of the cells, and after the 12 h incubation the cells seemed well adapted to the light conditions. The estimated kinetic constant for the chlorophyll synthesis averaged 1.5 x 1.0(-2) h-1, whereas the growth rate calculated from the changes in the cell numbers changed from 0.14 to greater than 2.5 doubling per day. The smallest size fraction presented the highest growth rate (greater than 2.5 doublings per day). The relationship between the total red fluorescence as estimated with the FCM and the biovolume revealed that the cells from the 2 m samples at the beginning of the experiment were probably nutrient limited. Important changes in the size of the cells under nutrient limitation were also observed. The FCM data suggest that the FCM is a valuable tool for estimating the relative growth response and nutritional state of natural phytoplankton populations.

Cell Division↗

Comparison of the long-term, postsurgical survival of women and men in the Coronary Artery Surgery Study (CASS).

This study compares the survival of men and women an average of 6 years after coronary artery bypass graft surgery (CABG) by means of the Coronary Artery Surgery Study (CASS) registry. Subjects included in these analyses were the 6100 men and 1097 women who survived surgery. Medical history and physical and laboratory information were collected from each patient at baseline. Men and women were compared for differences in baseline characteristics, long-term survival (by means of the Cox proportional hazards models), and predictors of long-term survival. In this study women, at baseline, were older and more likely to have hypertension and diabetes compared to men; whereas men were more likely to have had prior coronary heart disease. In this study of CASS participants there was no difference between men and women with regard to survival after CABG. There was also no difference between men and women in predictors of 6-year mortality. Two baseline variables were strongly related to subsequent mortality in both men and women: a high left ventricular wall motion score and taking both digitalis and diuretics (for women: relative risk = 2.31, confidence interval = 1.38 to 3.87; for men: relative risk = 1.90, confidence interval = 1.45 to 2.50).

Adult↗

Concurrent neuroborreliosis and Alzheimer's disease: analysis of the evidence.

Several recent reports have claimed a possible association between Borrelia burgdorferi infection and Alzheimer's disease (AD). Herein, we describe our search for additional evidence of neuroborreliosis in AD. Brain tissue from neuropathologically confirmed cases of AD was cultured for B burgdorferi using standard microbiologic methods. Material derived from culture was further examined using electron microscopy, direct immunofluorescence and acridine orange fluorescence. Previous studies have shown high titers of antiborrelia antibodies in CSF in all cases of confirmed neuroborreliosis; therefore, we tested CSF from neuropathologically confirmed cases of AD by indirect immunofluorescence and enzyme-linked immunoassay. In addition, imprint preparations from AD and control brain tissues were studied by direct immunofluorescence using a monoclonal antiborrelia antibody. Finally, a Western blot method was used to analyze protein extracts from cultures and AD brain tissue for the presence of borrelia antigen. Contrary to previous studies, our results do not support an association between infection with B burgdorferi and AD.

Alzheimer Disease↗

Comparison of blood gases during transport using two methods of ventilatory support.

Transportation of critically ill patients requiring ventilatory support represents a common, yet difficult, problem faced by clinicians. We examined 28 patients requiring transport in a prospective, randomized fashion, comparing manual ventilation with ventilation provided by a transport ventilator. Patients were ventilated to their destination with one method and returned with the alternate method. After manual ventilation, all patients showed a marked respiratory alkalosis (pH increased from 7.39 to 7.51 and PaCO2 decreased from 39 to 30 torr). After ventilation with the transport ventilator, no appreciable changes in pH or PaCO2 were seen. Oxygenation remained stable with both methods. No patient suffered hemodynamic instability, although two patients in the manual ventilation group developed cardiac arrhythmias. We conclude that when ventilatory support is required during transport, a transport ventilator produces reliable control of ventilation.

Adult↗