Biomedical subjects

L E Davis

Publications and source records attributed to L E Davis.

At least 55 records · Page 3Linked to original sources

PubMed1994

Danger of corticosteroid administration in meningitis due to misdiagnosed agent.

A 3 1/2-year-old child with acute tuberculous meningitis was misdiagnosed as having "partially treated" meningitis and was treated with ampicillin, chloramphenicol, and dexamethasone. She developed obstructive hydrocephalus and miliary spread of tuberculosis which led to death. It is likely that failure to consider alternative diagnoses promptly and the use of corticosteroids along with ineffective antibiotics contributed to the outcome. Although they may lessen some complications of bacterial meningitis, the indiscriminate use of corticosteroids in misdiagnosed bacterial meningitis may be detrimental.

Ampicillin↗

PubMed1994

In vitro synergism of concentrated Allium sativum extract and amphotericin B against Cryptococcus neoformans.

Allium sativum (garlic) derived preparations are used alone or with amphotericin B in Asia to treat human systemic fungal infections and cryptococcal meningitis. To evaluate the scientific merit of using allicin-derived compounds as an anti-fungal drug, we prepared a concentrated A. sativum extract that contained 34% allicin, 44% total thiosulfinates, and 20% vinyldithiins. We found that the concentrated extract possessed potent in vitro fungistatic and fungicidal activity against 3 different isolates of Cryptococcus neoformans. The minimum inhibitory concentration of the concentrated garlic extract against 1 x 10(5) organisms of C. neoformans ranged from 6 to 12 micrograms/ml. In addition, in vitro synergistic fungistatic activity with amphotericin B was demonstrated against all isolates of C. neoformans. This study lends laboratory support for the treatment of cryptococcal infections with concentrated garlic extracts.

Amphotericin B↗

PubMed1994

Dizziness in elderly men.

OBJECTIVE: To evaluate the causes of dizziness in elderly men. DESIGN: A descriptive study involving the clinical and laboratory features of elderly men with dizziness. SETTING: A university-affiliated Veterans Affairs medical center. PATIENTS: One hundred seventeen consecutive men more than 50 years of age attending a general neurology clinic with the chief complaint of dizziness. RESULTS: The median duration of dizziness at first office visit was 45 weeks. Forty-nine percent of patients had more than one diagnosis that contributed to their dizziness. Dysfunctions of the peripheral vestibular system were found in 71% and were the principal causes in 56%. Benign positional vertigo was present in 34%. Disorders of the visual system were found in 26% but were the major cause in only 1%. Diagnoses involving the proprioceptive system were present in 17% and were the principal cause in 7%. Structural lesions of the brainstem or cerebellum or metabolic disorders that affected normal brainstem function were identified in 59% and were the major diagnoses in 22%. A psychophysiologic diagnosis was made in 6% but was the major diagnosis in only 3%. At the 6-months follow-up, 55% of patients improved, 34% were unchanged, 4% worsened, and 7% were lost to follow-up. CONCLUSIONS: Contrary to reports in the literature, dizziness in the elderly is more persistent, has more causes, is less often due to a psychophysiologic cause, and seems to be more incapacitating than dizziness in younger patients.

Age Factors↗

PubMed1994

Cortical organization in adulthood is modified by neonatal infarct: a case study.

PURPOSE: To assess anomalous cortical organization of somatosensory function in a 23-year-old man who had had a neonatal infarct involving the left middle cerebral artery. MATERIALS AND METHODS: The infarct destroyed the primary and secondary somatosensory areas of the subject's left hemisphere but caused only mild perturbation of somatosensation on the right side of his body. With magnetic source imaging, the authors integrated magnetoencephalographic data with magnetic resonance imaging data to create magnetic source localization images that showed the mapping between brain function and structure. RESULTS: Electrical stimulation of the right median nerve evoked activity in two nontraditional areas: (a) an intact region of the left inferior temporal gyrus and (b) the ipsilateral right medial parietal cortex. CONCLUSION: These data suggest that bilateral neural reorganization can be induced by unilateral neonatal damage.

Adult↗

PubMed1994

Renal function during chronic anemia in the ovine fetus.

Our purpose was to determine how prolonged anemia alters fetal renal function and acid-base balance. In seven ovine fetuses made progressively anemic over 1 wk by serial isovolemic hemorrhage, hematocrit was reduced from 33.3 +/- 4.5 to 14.0 +/- 1.0%. Femoral arterial oxygen content was less and renal plasma flow was greater in anemic fetuses (1.5 +/- 0.1 ml/dl and 339 +/- 58 ml.min-1.100 g kidney-1) than in 6 control fetuses (7.0 +/- 1.3 ml/dl and 160 +/- 34 ml.min-1.100 g kidney-1). Urine flow and sodium excretion were also greater in anemic fetuses (1.2 +/- 0.6 ml/min and 79 +/- 49.5 mumol/min) than in controls (0.5 +/- 0.2 ml/min and 16 +/- 9.8 mumol/min). This higher sodium excretion was apparently due to a lower fractional sodium reabsorption in anemic fetuses compared with controls (84.1 +/- 5.8 vs. 96.5 +/- 1.7%), rather than to differences in either glomerular filtration rate or amount of filtered sodium. In addition, the higher sodium excretion in anemic fetuses was associated with greater urinary lactate and inorganic phosphate excretions and larger amniotic fluid volumes than in controls. From these data we conclude that when fetal renal oxygen delivery is limited by a prolonged reduction in hematocrit, excretions of sodium and water, as well as other osmotically active solutes, increase, and this results in an increase in amniotic fluid volume.

Amniotic Fluid↗

PubMed1994

The pharmacokinetics of injectable allopurinol in newborns with the hypoplastic left heart syndrome.

OBJECTIVE: The purpose of this investigation was to determine the pharmacokinetic disposition of intravenous allopurinol and its metabolite oxypurinol in neonates with the hypoplastic left heart syndrome (HLHS) and to evaluate the subsequent degree of xanthine oxidase inhibition using serum uric acid as a marker. METHODS: Pharmacokinetic data were evaluated in 12 stable preoperative neonates with HLHS after a single intravenous allopurinol administration of 5 mg/kg or 10 mg/kg. Pharmacokinetic parameters were determined for elimination half-life, clearance, volume of distribution, and mean residence time. Xanthine oxidase inhibition, measured by serum uric acid reduction, was also measured. RESULTS: Pharmacokinetic parameters revealed no statistically significant differences between a 5-mg/kg and 10-mg/kg dose of intravenous allopurinol on elimination half-life, clearance, volume of distribution, and mean residence time. Mean serum uric acid levels were significantly reduced from baseline by 39.99 and 42.94%, respectively, in the 5- and 10-mg/kg treatment groups. DISCUSSION: The enzyme xanthine oxidase plays a key biochemical role in the generation of toxic oxygen-derived free radicals during ischemia-reperfusion conditions. Allopurinol and its active metabolite oxypurinol inhibit xanthine oxidase, and significantly reduce the conversion of hypoxanthine to xanthine and xanthine to uric acid. Cell injury may be caused by toxic oxygen free radicals produced by ischemia-reperfusion injury such as could occur during the repair of HLHS under hypothermic total circulatory arrest. We hypothesize that allopurinol may provide protection from cellular injury in this clinical context.

Allopurinol↗

PubMed1994

Cisplatin: a clinical review. Part I--Current uses of cisplatin and administration guidelines.

Cisplatin is one of the most active cancer treatment agents available. Unfortunately, however, cisplatin causes many untoward side effects. Nurses play a major role in administering cisplatin and in preventing and managing the adverse effects associated with this drug. In order to maximize the quality of life of patients undergoing cisplatin treatment, nurses need a thorough knowledge of its uses, administration, and side effects. This article is the first of a two-part series about cisplatin. Part I will provide a review of the mechanism of action, current uses, and administration guidelines. Part II will discuss the most common side effects of cisplatin and the appropriate nursing assessment and management of patients undergoing treatment with this agent. In addition, future directions for the use of cisplatin and the use of alternative agents will be discussed.

Cisplatin↗

PubMed1994

Effect of atrial natriuretic peptide on vascular permeation in the ovine fetus.

To study the effect of atrial natriuretic peptide (ANP) on vascular permeation of albumin in the fetus, ANP (167-600 ng/min) was infused into eight ovine fetuses and saline vehicle was infused into eight twin controls (gestational age 127 +/- 3 d) over a 50-min period. Using two different radiolabeled albumin markers, we determined the tissue to blood isotope ratio (TBIR), an index of albumin permeation, and the albumin clearance. Although ANP had no hemodynamic effect, a marked increase in the hematocrit was observed in ANP-infused fetuses compared with initial values (0.37 +/- 0.04 vs 0.42 +/- 0.04, p < 0.005) but was unchanged in the twin fetuses receiving saline vehicle (0.35 +/- 0.03 versus 0.35 +/- 0.02). TBIR and albumin permeation were increased in combined tissues of ANP-infused fetuses compared with saline controls (TBIR: 1.49 +/- 0.58 versus 1.29 +/- 0.3, p < 0.001; albumin clearance: 1091 +/- 1279 versus 827 +/- 1464 nL/g/min, p < 0.01). In individual tissues, TBIR was significantly increased in skin (2.88 +/- 0.67 versus 1.55 +/- 0.35, p < 0.02), muscle (1.6 +/- 0.27 versus 1.24 +/- 0.26, p < 0.02), adrenal (1.33 +/- 0.10 versus 1.13 +/- 0.15, p < 0.02), bone (1.67 +/- 0.45 versus 1.20 +/- 0.40, p < 0.02), kidney (1.52 +/- 0.25 versus 1.24 +/- 0.26, p < 0.03), and gut (1.69 +/- 0.20 versus 1.39 +/- 0.34, p < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗

PubMed1994

The challenge of racial difference: skills for clinical practice.

Just as racial injustice negatively affects the plight of minorities in society, racial tensions impede professional helping. Often, the racially dissimilar social worker and client approach each other with little understanding of each other's social realities and with unfounded assumptions. Unfortunately, professionals find it difficult to acknowledge such differences or their effect on their relationships. Yet the fruitfulness of the helping encounter often depends on the ability to develop and invest in a trusting relationship. This article identifies the societal roots of the stresses associated with cross-racial relationships. Three concerns commonly experienced by clients whose workers are racially different are identified: (1) Is the helper a person of goodwill? (2) Is the helper trained and skilled? (3) Is the help offered valid and meaningful for me and my social reality? Case vignettes are used to illustrate how each concern is typically mishandled. The importance of successfully managing each concern is stressed, and skills for successful management are illustrated.

Adaptation, Psychological↗

PubMed1994

An assessment of practitioner cross-racial treatment experiences.

This study sought to determine differences in the cross-racial practice experiences of white and minority social services practitioners. Fifty-three counselors in a Veterans Administration outreach center evaluated various aspects of their cross-racial practice experiences. Both white and minority counselors perceived themselves to work equally well with white clients, but white counselors perceived themselves to be less effective when working with minority clients. The majority of white and minority counselors reported identifying the source of white clients' problems as being internal and that of minority clients' problems as being external. This finding was interpreted as being a possible bias against white clients on the part of both white and minority practitioners. White counselors reported experiencing less client credibility, and minority counselors reported more incidents of racism. Implications for social work are discussed.

Adult↗

PubMed1993

The effect of dietary protein depletion on hepatic 5-fluorouracil metabolism.

BACKGROUND: Protein calorie malnutrition, which is highly prevalent in tumor-bearing hosts, increases toxicity to 5-fluorouracil (5-FU), but the mechanisms are unclear. This study investigated the effects of protein depletion on 5-FU in vivo hepatic metabolism using F19-nuclear magnetic resonance spectroscopy (19F-NMRS). METHODS: Rats received normal (21.5%) or low (2.5%) protein diet for 25 days. 5-FU was injected intraperitoneally, and hepatic fluorine spectra were obtained. Parallel experiments were conducted to determine serum 5-FU pharmacokinetics using high-performance liquid chromatography (HPLC) and to measure hepatic dihydropyrimidine dehydrogenase (DPD) activity. RESULTS: The mean time of initial detection of fluoro-beta-alanine and the mean duration of the 5-FU signal in the liver were significantly prolonged in the low-protein group. 5-FU clearance and hepatic DPD activity were significantly lower in the low-protein group. Low-protein animals demonstrated increased toxicity, with diarrhea, weight loss, leukopenia (P < 0.001), and an 85% mortality, compared with regular diet animals, who had mild diarrhea and weight loss but no leukopenia and a 12% mortality. CONCLUSION: Protein depletion results in increased toxicity to 5-FU, which is associated with a significantly decreased rate of hepatic metabolism and clearance of 5-FU and a significant decrease in hepatic DPD activity. 19F-NMRS can noninvasively identify these alterations of 5-FU metabolism in vivo and may serve as a useful guide to determining chemotherapy dosage adjustments to reduce toxicity.

Animals↗

PubMed1993

Transverse myelitis. Retrospective analysis of 33 cases, with differentiation of cases associated with multiple sclerosis and parainfectious events.

OBJECTIVE: A study was undertaken to determine whether cases of parainfectious-associated transverse myelitis (TM) and multiple sclerosis-associated TM could be distinguished on the basis of clinical criteria, radiologic features, or cerebrospinal fluid examination. A secondary objective was to determine the incidence of TM in a US population. DESIGN: A retrospective analysis of 33 cases was conducted. Cases were classified as being related to parainfectious multiple sclerosis, or spinal cord ischemia, or idiopathic. SETTING: All cases occurring in the Albuquerque, NM, area from 1960 through 1990 were reviewed. The population base was 500,000. OUTCOME MEASURES: Clinical presentation, radiologic features, cerebrospinal fluid, recovery of ambulation and bladder function, and recurrence rates were compared. RESULTS: Thirty-three patients satisfied study criteria, corresponding to an incidence of 4.6 per million per year. Forty-five percent of these cases were categorized as parainfectious, 21% as associated with multiple sclerosis, 12% as associated with spinal cord ischemia, and 21% as idiopathic. Patients with parainfectious TM suffered from spinal shock more frequently than did those with multiple sclerosis-associated TM. Patients with parainfectious TM showed evidence of spinal cord swelling, whereas patients with multiple sclerosis-associated TM had spinal cord plaques on magnetic resonance images but none showed swelling. Oligoclonal bands were absent in patients with parainfectious TM and present in three of five patients with multiple sclerosis-associated TM. CONCLUSIONS: Parainfectious TM may be distinguishable from that associated with multiple sclerosis on the basis of presentation, findings on imaging, and the presence of cerebrospinal fluid oligoclonal bands.

Adolescent↗

PubMed1993

Devic's neuromyelitis optica: a clinicopathological study of 8 patients.

We report the clinical, imaging, and laboratory features of 8 patients with Devic's neuromyelitis optica. All patients had severe myelopathy and optic neuritis. In no patient was the brain, the brainstem, or the cerebellum affected, even after several years of disease. Various immunosuppressive treatments failed to benefit the patients, 5 of whom died. Autopsies of these 5 patients demonstrated a severe necrotizing myelopathy with thickening of blood vessel walls and no lymphocyte infiltrates. In the appropriate clinical setting, the lack of white matter abnormalities demonstrated by magnetic resonance imaging of the head facilitates the recognition of Devic's syndrome during life. Inasmuch as Devic's myelopathy is necrotizing, rather than demyelinating, the prognosis of this syndrome is poor.

Adult↗

PubMed1993

Positive end-expiratory pressure lowers the risk of laser-induced polyvinylchloride tracheal-tube fires.

BACKGROUND: The possibility of ignition of polyvinylchloride (PVC) tracheal tubes by a CO2 laser is of concern in patients undergoing CO2 laser surgery of the airway. The authors analyzed the ignition of PVC tracheal tubes by a CO2 laser beam to determine what variables were involved, and then designed a study to determine how they affect the incidence of such fires. METHODS: For the analysis, PVC tracheal tubes were enclosed in a clear plexiglass enclosure and a laser beam was focused on the tubes. The enclosure contained one of three different gas combinations. A high-speed camera photographed the tubes during the analysis and showed that tracheal tube perforation always preceded ignition in all three gas combinations. These results led to the hypothesis that intraluminal gauge pressure (IGP) may be an important variable, because it would affect the flow of O2 across the perforation. This hypothesis was tested by aiming a CO2 laser beam at PVC tracheal tubes and varying IGP in 0.25-cm H2O increments, from 0.25 to 28 cm H2O, while nitrogen or helium containing O2 at 40, 50, or 60% flowed through the tubes. To simulate the clinical effect of IGP on PVC tracheal tube ignition, we used a mechanical lung model connected to an anesthesia breathing circuit with a standing bellows ventilator in which 60% He and 40% O2 flowed through a PVC tracheal tube. Laser beam exposure was started at three different times during the respiratory cycle: at the start of inspiration, at the end of inspiration, or at the end of expiration. Also, for each condition, trials were made at baseline circuit pressure (2.5 cm H2O) and at 5.0 cm H2O by the addition of 2.5 cm H2O positive end-expiratory pressure (PEEP) applied to the circuit. RESULTS: The incidence of tracheal tube ignition decreased as IGP increased. The IGP at which ignition did not occur (which increased as O2 concentration increased) did not differ between N2 and He at 40% O2, but was twice as high with N2 as with He at O2 of 50% and 60%. Fires never occurred when PEEP was added to the system and, when PEEP was not added, always started during the last 2 s of end expiration (when airway pressure is lowest), regardless of when the laser beam was activated. CONCLUSIONS: It is recommended that, in addition to other safety practices, PEEP be added to the breathing circuit during CO2 laser operations on the airway in which PVC tracheal tubes or laser-resistant tracheal tubes with PVC components are used.

Anesthesiology↗

PubMed1993

Hepatitis A post-viral encephalitis.

We report a seven-year-old girl who developed a hepatitis A viral infection and encephalitis. The patient developed fever, abdominal pains and jaundice. Five days later she became delirious, combative, and did not respond to verbal commands. Laboratory studies showed elevated liver enzymes and elevated serum immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies to hepatitis A virus. Cerebrospinal fluid contained IgG antibodies to hepatitis A virus but not IgM antibodies. Polymerase chain reaction, which amplifies a portion of the hepatitis A virus genome, did not demonstrate viral nucleic acid in cerebrospinal fluid. These studies suggest that the patient may have suffered from a post-viral hepatitis A encephalitis from which she fully recovered.

Antibodies, Viral↗

PubMed1993

Neuromagnetic mapping of brain function.

Magnetic source imaging, a technique that combines magnetoencephalography (MEG) and magnetic resonance (MR) imaging, was used to localize the somatosensory and auditory cortex in seven healthy subjects. Functional neuromagnetic data were obtained with a 37-channel biomagnetometer. Structural MR imaging data were obtained with a 1.5-T superconducting imager. Coordinates used in defining MEG and MR imaging space were reconciled to produce magnetic source images that displayed the putative locations of somatosensory and auditory activity in relation to brain anatomy. Sources of somatosensory activity were typically localized to the postcentral gyrus; sources of auditory activity were localized to the superior temporal plane. Extension of these results to patients with tumors (or other disorders) that distort normal brain anatomy has the potential to make noninvasive magnetic source imaging examinations clinically useful in guiding neurosurgical interventional procedures.

Adult↗

PubMed1993

Estrogen-induced left ventricular chamber enlargement in ewes.

We studied the chronic effect of administration of a single large intramuscular dose of 17 beta-estradiol on left ventricular chamber size and output in the ewe. Fourteen oophorectomized ewes were successfully instrumented and studied, with measurements made of left ventricular, aortic, right and left atrial pressures, left ventricular stroke volume, and left ventricular minor axis dimension. Unanesthetized ewes were studied before and 1, 2, and 3 wk after intramuscular administration of 0.6 mg/kg 17 beta-estradiol (7 ewes) or 1.5 ml sesame oil placebo (7 ewes). Left ventricular end-diastolic pressure-end-diastolic dimension (LVEDP-EDD) and left ventricular end-diastolic pressure-stroke volume (LVEDP-SV) relationships were quantified during graded inferior vena caval occlusion and volume infusion. Left ventricular end-diastolic diameter was larger after estrogen but not after placebo administration. The LVEDP-EDD relationship shifted progressively rightward, indicating left ventricular chamber enlargement in the estrogen group but was unchanged in the placebo group. The plateau limb of the LVEDP-SV relationship in the estrogen group shifted up from a mean stroke volume of 77.1-89.5 ml/beat and did not change in the placebo group. We conclude that administration of a single large intramuscular dose of 17 beta-estradiol resulted in left ventricular chamber enlargement and increased stroke volume in the ewe.

Animals↗

PubMed1993

Tuberculous meningitis in the southwest United States: a community-based study.

This community-based study analyzed 54 patients with definite or probable tuberculous meningitis (TBM) in New Mexico from 1970 through 1990. Patients ranged in age from 4 months to 86 years. The highest age-specific incidence occurred in the elderly, but 22% of patients were less than 10 years old. Native American patients were overrepresented. Patients were as likely to live in small towns as in large urban cities. Symptoms were present for a median of 13 days before admission. The majority of patients had fevers, headache, stiff neck, and mental changes, such as confusion or lethargy. No patient was admitted comatose. Focal neurologic signs were present in 33%. Laboratory testing found hyponatremia in 79%, pulmonary infiltrates on chest x-ray in 40%, ventricular dilatation on CT or MRI in 52%, and tuberculomas in 16%. PPD skin tests were positive in 64%. CSF cultures grew Mycobacterium tuberculosis in 50%, but colony counts were always lower than 10(2)/ml. As a consequence, acid-fast stains of CSF sediment were reported as positive in only 4%. Six patients were not diagnosed during the hospitalization and died of complications. Twenty-three percent of patients who were appropriately treated also died of complications during the initial hospitalization. Tuberculous meningitis continues to be an important disease in small communities, and affects all ages and ethnic and socioeconomic backgrounds.

Adolescent↗