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Biomedical subjects

K Davis

Publications and source records attributed to K Davis.

At least 37 records · Page 2Linked to original sources
PubMed2000

Cellular signaling with nitric oxide and cyclic guanosine monophosphate.

The understanding of the formation and biological actions of nitric oxide (NO) has grown extensively during the past two decades. With the discoveries of the biological effects of NO and nitrovasodilators on cyclic guanosine monophosphate, with the elucidation of the biochemical mechanisms of NO synthesis, and with the growing knowledge of regulation of NO synthases, the complexities of this signal transduction cascade and its participation in numerous cell signaling processes continues. NO can be recognized as an intracellular second messenger, a local substance for regulation of neighboring cells, a neurotransmitter, and probably a hormone acting at distant sites.

Animals↗
PubMed2000

Health insurance markets and income inequality: findings from an international health policy survey.

OBJECTIVE: To assess disparities in access to health care, financial burden of medical bills and perceived quality of care between those with above average incomes and those with below average incomes in five nations and to examine the relationship inequities in care experiences to health insurance coverage. DESIGN: Cross-sectional analysis of a random survey of adults in 1998. SUBJECTS: 5059 adults ages 18 and over in five English-speaking countries: Australia, Britain, Canada, New Zealand and the United States (approximately 1000 per country). MAIN OUTCOME MEASURES: Failure to receive needed care, difficulty getting care, waiting for elective surgery, problems paying medical bills, failure to fill prescriptions due to cost, perceived quality of medical care received and of most recent doctor visit. RESULTS: There were two to three-fold differences between those with above and below average incomes on measures of access to care in the US, Australia and New Zealand. In Britain and Canada indicators of access of to care were similar for the two income groups. Problems paying medical bills were most prevalent in the US, yet significant differences by income also existed in Australia, Canada and New Zealand. Those with below average incomes were more likely to have not filled a prescription due to cost in Australia, Canada, New Zealand and the US, with gaps by income most severe in the US. Ratings of quality of doctor visit were significantly different for the two income groups in the US, but not other countries. CONCLUSIONS: The analysis finds striking differences among countries in the relative equity of health care experiences. In general, care experiences are more unequal in three countries such as the US, Australia and New Zealand where systems have relatively greater reliance on private health insurance and markets. Greater inequality in care experiences is also associated with more divided public opinion regarding the need for system reform and the direction of recent policy changes. In Canada and Britain where care experiences are more equal of the health system are similar across income groups. Reliance on private insurance and patient user fees appears to lead to more divided views of the overall health system as well as inequity in access to care.

Adolescent↗
PubMed2000

A temperature-sensitive Krp1 allows in vivo characterization of kexin activation.

Members of the kexin family of processing enzymes are responsible for the cleavage of many proproteins during their transport through the secretory pathway. The enzymes are themselves made as inactive precursors and we have investigated the activation of Krp1, a kexin from the fission yeast Schizosaccharomyces pombe. As Krp1 is essential for cell growth, we have used a krp1ts strain to investigate the role of the prosequence in the activation process. Mutations that reduce either the efficiency with which the prosequence is released or the rate at which the released prosegment is subsequently cleaved at an internal site are less active when assayed in vivo. We also show that prosegments lacking an internal dibasic motif can act as autoinhibitors and prevent activation of the catalytic fragment. Krp1 constructs containing prosequences based on these inhibitors do not become active in vitro. Surprisingly, the same constructs do become active in the intact cell and appear to suggest that alternative activation processes can be used by these enzymes.

Amino Acid Sequence↗
PubMed2000

Positive end-expiratory pressure and response to inhaled nitric oxide: changing nonresponders to responders.

BACKGROUND: Inhaled nitric oxide (INO) has been shown to improve oxygenation in two thirds of patients with acute respiratory distress syndrome (ARDS). Failure to respond to INO is multifactorial. We hypothesized that the addition of positive end expiratory pressure (PEEP) might modify the response to INO in patients who had previously failed to respond to INO. METHODS: Patients with ARDS who failed to respond to INO at 1 ppm (PaO2 increase of < 20%) were selected. Each patient underwent a PEEP trial using an improvement in static lung compliance as the end point. One hour after the new PEEP level was reached, hemodynamic and blood gas values were obtained. INO was then reinstituted at 1 ppm, and hemodynamic and blood gas variables were obtained 1 hour later. RESULTS: Six of nine patients demonstrated an increase in PaO2/FIO2 (161 +/- 27 to 186 +/- 29) with a mean increase in PEEP of 3.7 cm H2O. Each patient responding to PEEP further improved PaO2/FIO2 (186 +/- 29 to 223 +/- 36) with INO at 1 ppm. The three patients who failed to improve after the PEEP increase also failed to respond to a second trial of INO. There were no changes in cardiac output or systemic vascular resistance. Pulmonary artery pressures decreased slightly (39 +/- 5 vs 38 +/- 7 vs 35 +/- 9 mm Hg). Pulmonary vascular resistance decreased significantly after reintroduction of INO (298 +/- 131 vs 310 +/- 122 vs 249 +/- 105 dynes/sec/cm-5) in patients who responded positively. CONCLUSIONS: The response of ARDS patients to INO can be improved if optimum alveolar recruitment is achieved by the addition of PEEP. PEEP and INO have a synergistic effect on PaO2/FIO2. Patients who fail to respond to INO may benefit from an optimum PEEP trial.

Administration, Inhalation↗
PubMed2000

Dynamic helical computed tomography scan accurately detects hemorrhage in patients with pelvic fracture.

BACKGROUND: The purpose of this study was to evaluate the use of dynamic helical computed tomography (CT) scan for screening patients with pelvic fractures and hemorrhage requiring angiographic embolization for control of bleeding. METHODS: Patients admitted to the trauma service with pelvic fractures were identified from the trauma registry. Data retrieval included demographics, hemodynamic instability, Injury Severity Score, blood transfusion requirement, length of stay, and mortality. CT scans obtained during the initial evaluation were reviewed for the presence of contrast extravasation and correlated with angiographic findings. Data are reported as mean +/- SEM, with P<.05 considered significant. RESULTS: Seven thousand seven hundred eighty-one patients were admitted from June 1994 to May 1999. A pelvic fracture was diagnosed in 660 (8.5%). Two hundred ninety (44.0%) dynamic helical CT scans were performed, of which 13 (4.5%) identified contrast extravasation. Nine (69%) were hemodynamically unstable and had pelvic arteriography performed. Arterial bleeding was confirmed in all and controlled by embolization. Patients with contrast extravasation had significantly greater Injury Severity Score, blood transfusion requirement and length of stay. Sensitivity, specificity, and accuracy of CT scan for identifying patients requiring embolization were 90.0%, 98.6%, and 98.3%, respectively. CONCLUSIONS: Early use of dynamic helical CT scanning in the multiply injured patient with a pelvic fracture accurately identifies the need for emergent angiographic embolization.

Abdominal Injuries↗
PubMed2000

The risk assessment profile score identifies trauma patients at risk for deep vein thrombosis.

BACKGROUND: The identification of trauma patients at risk for the development of deep venous thrombosis (DVT) at the time of admission remains difficult. The purpose of this study is to validate the risk assessment profile (RAP) score to stratify patients for DVT prophylaxis. METHODS: All patients admitted from November 1998 thru May 1999 were evaluated for enrollment. We prospectively assigned patients as low risk or high risk for DVT using the RAP score. High-risk patients received both pharmacologic and mechanical prophylaxis. Low-risk patients received none. Surveillance duplex Doppler scans were performed each week of hospitalization or if symptoms developed. Hospital charges for prophylaxis were used to determine the savings in the low-risk group. Statistical differences between the risk groups for each factor of the RAP and development of DVT were determined by the chi-squared test, with significance at a probability value of less than .05. RESULTS: There were 102 high-risk (64%) and 58 low-risk (36%) individuals studied. Eleven of the high-risk group (10.8%) experienced the development of DVT (asymptomatic, 64%). None of the low-risk group was diagnosed with DVT. Five of the 16 RAP factors were statistically significant for DVT. Eliminating prophylaxis and Doppler scans in low-risk patients resulted in a total savings of $18,908 in hospital charges. CONCLUSIONS: The RAP score correctly identified trauma patients at increased risk for the development of DVT. Despite prophylaxis, the high-risk group warrants surveillance scans. Withholding prophylaxis in low-risk patients can reduce hospital charges without risk.

Adult↗
PubMed2000

Prone positioning for acute respiratory distress syndrome in the surgical intensive care unit: who, when, and how long?

BACKGROUND: We evaluated the effects of prone positioning (PP) on surgery and trauma patients with acute respiratory distress syndrome (ARDS). METHODS: Patients with ARDS were studied. Exclusion criteria were contraindications to PP. Patients were evaluated in the supine position and after being turned to the PP. After 6 hours, patients were returned to the supine position for 3 hours. One hour after each position change, arterial and mixed venous blood was drawn and analyzed for blood gases and pH, and hemodynamics were measured. RESULTS: Over 20 months, 27 patients met the criteria, and 20 of the patients were entered into the study. On day 1, 18 of 20 patients (90%) responded with an increase in PaO(2) during PP. On day 2, 16 of 17 patients (94%) responded; on day 3, 15 of 16 patients responded (94%); on day 4, 11 of 13 patients responded (85%); on day 5, 8 of 8 patients responded (100%); and on day 6, 4 of 5 patients responded (80%). Pao(2)/Fio(2) and Qs/Qt were significantly improved (P<.05) during PP. There were 91 periods of PP, lasting 10.3+/-1.2 hours. Of 91 changes to PP, 78 changes (86%) resulted in an improvement in Pao(2)/Fio(2) of more than 20%. CONCLUSIONS: PP improves oxygenation in ARDS for 6 days with few complications.

Adult↗
PubMed2000

Institutional and individual learning curves for focused abdominal ultrasound for trauma: cumulative sum analysis.

OBJECTIVE: To evaluate both institutional and individual learning curves with focused abdominal ultrasound for trauma (FAST) by analyzing the incidence of diagnostic inaccuracies as a function of examiner experience for a group of trauma surgeons performing the study in the setting of an urban level I trauma center. SUMMARY BACKGROUND DATA: Trauma surgeons are routinely using FAST to evaluate patients with blunt trauma for hemoperitoneum. The volume of experience required for practicing trauma surgeons to be able to perform this examination with a reproducible level of accuracy has not been fully defined. METHODS: The authors reviewed prospectively gathered data for all patients undergoing FAST for blunt trauma during a 30-month period. All FAST interpretations were validated by at least one of four methods: computed tomography, diagnostic peritoneal lavage, celiotomy, or serial clinical evaluations. Cumulative sum (CUSUM) analysis was used to describe the learning curves for each individual surgeon at target accuracy rates of 85%, 90%, and 95% and for the institution as a whole at target examination accuracy rates of 85%, 90%, 95%, and 98%. RESULTS: Five trauma surgeons performed 546 FAST examinations during the study period. CUSUM analysis of the aggregate experience revealed that the examiners as a group exceeded 90% accuracy at the outset of clinical examination. The level of accuracy did not improve with either increased frequency of performance or total examination experience. The accuracy rates observed for each trauma surgeon ranged from 87% to 98%. The surgeon with the highest accuracy rate performed the fewest examinations. No practitioner demonstrated improved accuracy with increased experience. CONCLUSIONS: Trauma surgeons who are newly trained in the use of FAST can achieve an overall accuracy rate of at least 90% from the outset of clinical experience with this modality. Interexaminer variations in accuracy rates, which are observed above this level of performance, are probably related more to issues surrounding patient selection and inherent limitations of the examination in certain populations than to practitioner errors in the performance or interpretation of the study.

Abdominal Injuries↗
PubMed2000

Mechanical comparison of fixation techniques for the tibial tubercle osteotomy.

Tibial tubercle osteotomies currently are used as an exposure technique for revision total knee arthroplasty and for distal patellofemoral realignment. A review of the literature reveals no biomechanical studies that evaluate methods of osteotomy fixation in terms of static strength. This study evaluates the fixation strength of common techniques used to repair tibial tubercle osteotomies. Bevel and stepcut tibial tubercle osteotomies were created in 36 anatomic specimen knees and were repaired with either two 4.5-mm cortical screws or 18-gauge stainless steel cerclage wire. The failure load for the bevelcut osteotomies repaired with two-screws was 1,654 +/- 359 N; for the bevelcut osteotomies repaired with three cerclage wires, 622 +/- 283 N; for the stepcut osteotomies repaired with three cerclage wires, was 984 +/- 441 N; and for the stepcut osteotomy repaired with four cerclage wires, 1,099 +/- 632 N. This study shows that two bicortical screws provide the greatest static fixation strength for repairing tibial tubercle osteotomies. When repairing tibial tubercle osteotomies for distal patellofemoral realignment, screw fixation would provide the most reliable fixation. However, the placement of screws around the stem of a revision arthroplasty tibial component is difficult. Cerclage wires are easier to place and provide solid static fixation, especially with the addition of a proximal stepcut osteotomy.

Aged↗
PubMed2000

Prolonged use of heat and moisture exchangers does not affect device efficiency or frequency rate of nosocomial pneumonia.

OBJECTIVE: To determine whether use of a single heat and moisture exchanger (HME) for < or =120 hrs affects efficiency, resistance, level of bacterial colonization, frequency rate of nosocomial pneumonia, and cost compared with changing the HME every 24 hrs. DESIGN: Prospective, controlled, randomized, unblinded study. SETTING: Surgical intensive care unit at a university teaching hospital. PATIENTS: A total of 220 consecutive patients requiring mechanical ventilation for >48 hrs. INTERVENTIONS: Patients were randomized to one of three groups: a) hygroscopic HME (Aqua+) changed every 24 hrs (HHME-24); b) hydrophobic HME (Duration HME) changed every 120 hrs (HME-120); and c) hygroscopic HME (Aqua+) changed every 120 hrs (HHME-120). Devices in all groups could be changed at the discretion of the staff when signs of occlusion or increased resistance were identified. MEASUREMENTS AND MAIN RESULTS: Daily measurements of inspired gas temperature, inspired relative humidity, and device resistance were made. Additionally, daily cultures of the patient side of the device were accomplished. The frequency rate of nosocomial pneumonia was made by using clinical criteria. Ventilatory support variables, airway care, device costs, and clinical indicators of humidification efficiency (sputum volume, sputum efficiency) were also recorded. Prolonged use of both hygroscopic and hydrophobic devices did not diminish efficiency or increase resistance. There was no difference in the number of colony-forming units from device cultures over the 5-day period and no difference between colony-forming units in devices changed every 24 hrs compared with devices changed after 120 hrs. The average duration of use was 23+/-4 hrs in the HHME-24 group, 73+/-13 hrs in the HME-120 group, and 74+/-9 hrs in the HHME-120 group. Mean absolute humidity was greater for the hygroscopic devices (30.4+/-1.1 mg of H2O/L) compared with the hydrophobic devices (27.8+/-1.3 mg of H2O/L). The frequency rate of nosocomial pneumonia was 8% (8:100) in the HHME-24 group, 8.3% (5:60) in the HME-120 group, and 6.6% (4:60) in the HHME-120 group. Pneumonia rates per 1000 ventilatory support days were 20:1000 in the HHME-24 group, 20.8:1000 in the HME-120 group, and 16.6:1000 in the HHME-120 group. Costs per day were $3.24 for the HHME-24 group, $2.98 for the HME-120 group, and $1.65 for the HHME-120 group. CONCLUSIONS: Changing the hydrophobic or hygroscopic HME after 3 days does not diminish efficiency, increase resistance, or alter bacterial colonization. The frequency rate of nosocomial pneumonia was also unchanged. Use of HMEs for >24 hrs, up to 72 hrs, is safe and cost effective.

Adult↗
PubMed2000

Male systemic sclerosis and occupational silica exposure-a population-based study.

BACKGROUND: The continuing uncertainty about the silica-systemic sclerosis relationship led to the investigation of its role as a disease determinant in a large population-based study of systemic sclerosis. AIMS: To compare the frequency, socioeconomic and educational status, age-specific prevalence and duration of occupational silica exposure in males with and without systemic sclerosis. To assess the temporal relationship between exposure and disease onset. To estimate disease latency. To compare disease characteristics between silica-exposed and non-silica-exposed male cases. METHODS: The study was case-control in design. The exposure variable was occupational silica exposure as assessed by an occupational health officer blinded to case/control status and the outcome variable was systemic sclerosis. The employed instrument comprised either a standardised telephone questionnaire (interviewed cases and controls) or medical records (deceased or living-status-unknown cases). RESULTS: Sixty of 160 cases (37.5%) and 11 of 83 (13.3%) controls had occupational silica exposure (OR=3.93; 1.84-8.54). Comparison of data between 64 interviewed cases and all controls demonstrated initial occupational silica exposure occurring before age 40, comparable educational status but significantly different cumulative socioeconomic status with cases being over-represented in semi-skilled and unskilled occupations. Cross-sectional 'current' occupational data underestimated cumulative silica exposure by more than 50%. Silica exposure uniformly preceded onset of second disease symptoms and disease diagnosis. In most, it also preceded onset of first disease symptoms. Disease latency approximated two decades. No disease features distinguished silica-associated systemic sclerosis from idiopathic systemic sclerosis. The duration of silica exposure in the interviewed silica-exposed cases did not significantly exceed that of silica-exposed controls. CONCLUSIONS: Male systemic sclerosis displays socioeconomic dependence. Silica is a disease determinant in male systemic sclerosis, with disease features including a long latency and clinical characteristics indistinguishable from idiopathic disease. Cross-sectional 'current' occupational data underestimate cumulative occupational silica exposure.

Adolescent↗
PubMed2000

Alpha1 connexin 43 gap junctions are decreased in human adrenocortical tumors.

Gap junctional communication disorders have been implicated in the etiology of benign and malignant tumors. Understanding the type, distribution, and frequency of gap junctions in adrenal disorders should provide insight into the role of gap junctions in adrenal carcinogenesis as well as information that may be useful in developing improved diagnosis and treatment of adrenal diseases. Using immunocytochemical techniques, we have characterized and compared alpha1 connexins 43 gap junction protein levels in normal adrenal glands to those in benign and malignant adrenocortical human tumors. In addition, gap junction protein levels were studied in a human adrenal cancer cell line (H295). In both normal and neoplastic adrenal tissues, only alpha1 connexin 43 could be detected, whereas beta1 connexin 32 and beta2 connexin 26 were not found. In the normal adrenal gland, the zona fasciculata was demonstrated to have the highest number of gap junctions per cell (mean +/- SEM, 13.78 +/- 1.93). In contrast, in benign adrenocortical adenomas, the number of gap junctions per cell compared to that detected in normal adrenal glands was significantly reduced (mean +/- SEM, 4.6 +/- 1.17; P < or = 0.05), and the lowest number was found in malignant adrenocortical tumors (1.42 +/- 0.58; P < or = 0.05). Similarly, there were few or no alpha1 connexin 43 gap junctions in the H295 population. There was a progressive decrease in gap junction plaques in adrenocortical cancer cell populations compared to those in normal cell populations. Therefore, analysis of gap junction protein may be helpful for the differential diagnosis of benign and malignant adrenal tumors. The induction of gap junctions in malignant cells may provide a novel therapeutic strategy for adrenal cancer.

Adenoma↗
PubMed2000

Attribution of injury to alcohol involvement in young adults seriously injured in alcohol-related motor vehicle crashes.

BACKGROUND: Approximately 40% of all traffic fatalities are associated with the use of alcohol. Hospitalization for serious injury after a motor vehicle crash related to use of alcohol may be an opportunity to change drinking behaviors in non-alcohol-dependent drinkers, thereby reducing the risk for future disability and death. OBJECTIVES: To determine the degree to which non-alcohol-dependent adults aged 18 to 45 years with alcohol-related vehicular trauma attributed their injury to use of alcohol. METHODS: During hospitalization, 132 subjects involved in alcohol-related motor vehicle crashes were interviewed. The interviews included the question, "To what extent do you believe your alcohol consumption was responsible for this injury?" Responses were measured on a 7-point scale ranging from 1 (not at all) to 7 (totally). RESULTS: In response to the question about attribution of injury to alcohol, 37.8% of subjects responded "not at all," 24.3 responded "somewhat," and 37.9% responded "mostly" or "totally." Spearman rank correlation between attribution of injury to alcohol involvement and blood alcohol content at admission was r = 0.440 (P < .001). CONCLUSIONS: More than 60% of patients injured in alcohol-related motor vehicle crashes attributed their injury partly or totally to use of alcohol. When alcohol-free, hospitalized patients with higher blood levels of alcohol on admission were more likely than those with lower levels to attribute their injury to alcohol. Hospitalization for a motor vehicle crash related to use of alcohol provides an opportunity for interventions to decrease drinking.

Accidents, Traffic↗
PubMed2000

The effects of passive humidifier dead space on respiratory variables in paralyzed and spontaneously breathing patients.

BACKGROUND: Passive humidifiers have gained acceptance in the intensive care unit because of their low cost, simple operation, and elimination of condensate from the breathing circuit. However, the additional dead space of these devices may adversely affect respiratory function in certain patients. This study evaluates the effects of passive humidifier dead space on respiratory function. METHODS: Two groups of patients were studied. The first group consisted of patients recovering from acute lung injury and breathing spontaneously on pressure support ventilation. The second group consisted of patients who were receiving controlled mechanical ventilation and were chemically paralyzed following operative procedures. All patients used 3 humidification devices in random order for one hour each. The devices were a heated humidifier (HH), a hygroscopic heat and moisture exchanger (HHME) with a dead space of 28 mL, and a heat and moisture exchanger (HME) with a dead space of 90 mL. During each measurement period the following were recorded: tidal volume, minute volume, respiratory frequency, oxygen consumption, carbon dioxide production, ratio of dead space volume to tidal volume (VD/VT), and blood gases. In the second group, intrinsic positive end-expiratory pressure was also measured. RESULTS: Addition of either of the passive humidifiers was associated with increased VD/VT. In spontaneously breathing patients, VD/VT increased from 59 +/- 13 (HH) to 62 +/- 13 (HHME) to 68 +/- 11% (HME) (p < 0.05). In these patients, constant alveolar ventilation was maintained as a result of increased respiratory frequency, from 22.1 +/- 6.6 breaths/min (HH) to 24.5 +/- 6.9 breaths/min (HHME) to 27.7 +/- 7.4 breaths/min (HME) (p < 0.05), and increased minute volume, from 9.1 +/- 3.5 L/min (HH) to 9.9 +/- 3.6 L/min (HHME) to 11.7 +/- 4.2 L/min (HME) (p < 0.05). There were no changes in blood gases or carbon dioxide production. In the paralyzed patient group, VD/VT increased from 54 +/- 12% (HH) to 56 +/- 10% (HHME) to 59 +/- 11% (HME) (p < 0.05) and arterial partial pressure of carbon dioxide (PaCO2) increased from 43.2 +/- 8.5 mm Hg (HH) to 43.9 +/- 8.7 mm Hg (HHME) to 46.8 +/- 11 mm Hg (HME) (p < 0.05). There were no changes in respiratory frequency, tidal volume, minute volume, carbon dioxide production, or intrinsic positive end-expiratory pressure. DISCUSSION: These findings suggest that use of passive humidifiers with increased dead space is associated with increased VD/VT. In spontaneously breathing patients this is associated with an increase in respiratory rate and minute volume to maintain constant alveolar ventilation. In paralyzed patients this is associated with a small but statistically significant increase in PaCO2. CONCLUSION: Clinicians should be aware that each type of passive humidifier has inherent dead space characteristics. Passive humidifiers with high dead space may negatively impact the respiratory function of spontaneously breathing patients or carbon dioxide retention in paralyzed patients. When choosing a passive humidifier, the device with the smallest dead space, but which meets the desired moisture output requirements, should be selected.

Analysis of Variance↗