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Biomedical subjects

Roger J Lewis

Publications and source records attributed to Roger J Lewis.

18 recordsLinked to original sources
PubMed2003

Pharmacodynamics of linezolid in a clinical isolate of Streptococcus pneumoniae genetically modified to express lux genes.

A bioluminescent clinical isolate of Streptococcus pneumoniae was used to test the real-time effects of the oxazolidinone antibiotic, linezolid, on metabolism compared with effects on cell replication. Viable counts and bioluminescence measurements showed that linezolid has little bactericidal effect, which was similar at minimum (6 mg/L), intermediate (13 mg/L) and maximum (20 mg/L) serum concentrations. The post-antibiotic effect, however, was shorter when measured by light output than by viable counts. The results demonstrate that bioluminescence provides a rapid and sensitive means of measuring the effect of antimicrobials on bacterial metabolism, and that the latter recovers earlier than commencement of cell replication after linezolid exposure.

Acetamides↗
PubMed2003

Implications of hospital evacuation after the Northridge, California, earthquake.

BACKGROUND: On January 17, 1994, an earthquake with a moment magnitude (total energy release) of 6.7 occurred in Northridge, California, leading to the evacuation of patients from several hospitals. We examined the reasons for and methods of evacuation and the emergency-management strategies used. The experience in California may have implications for hospital strategies for responding to any major disaster, including an act of terrorism. METHODS: From September 1995 to September 1996, we surveyed all acute care hospitals in Los Angeles County that reported having evacuated patients after the Northridge earthquake. Physicians, nurses, hospital administrators, and staff on duty at the hospitals during the evacuation responded to a 58-item structured questionnaire. RESULTS: Eight of 91 acute care hospitals (9 percent) were evacuated. Six hospitals evacuated patients within 24 hours (the immediate-evacuation group), four completely and two partially. All six cited nonstructural damage such as water damage and loss of electrical power as a major reason for evacuation. Five hospitals evacuated the most seriously ill patients first, and one hospital evacuated the healthiest patients first. All hospitals used available equipment to transport patients (blankets, backboards, and gurneys) rather than specialized devices. No deaths resulted from evacuation. One hospital evacuated patients after 3 days and another after 14 days because of structural damage, even though initial inspections had shown no damage (the delayed-evacuation group). Both hospitals required demolition. Some hospitals identified destinations for their evacuated patients independently, whereas others sought the assistance of the Los Angeles County Emergency Operations Center; the two strategies were equally effective. CONCLUSIONS: After even a moderate earthquake, hospitals are at risk for both immediate nonstructural damage that may force them to evacuate patients and the delayed discovery of structural damage resulting in permanent closure. Evacuation of large numbers of inpatients from multiple hospitals can be accomplished quickly and safely with the use of available resources and personnel.

California↗
PubMed2003

Improving the quality of care for patients with pneumonia in very small hospitals.

BACKGROUND: Despite the publication of guidelines for the management of pneumonia, significant variation in care continues to exist. While there have been several published reports of quality improvement projects for pneumonia, there are few data on the effectiveness of these efforts in small hospitals. The purpose of this study was to demonstrate that a project implemented by a quality improvement organization in small hospitals would lead to an improvement in care that could not be accounted for by secular trends in the management of pneumonia. METHODS: Medicare-insured hospital admissions for pneumonia were reviewed from 20 small hospitals in Oklahoma (intervention group) at baseline and after feedback. Project intervention included onsite feedback presentations to the medical staff, samples of performance improvement materials, and comparative measures of performance of predefined quality indicators. A second group of 16 demographically similar hospitals (control group) was selected for review during the same 2 periods. These hospitals subsequently underwent an identical intervention with a follow-up assessment. RESULTS: Statistically significant improvements in process measures were demonstrated in the intervention hospitals, including performance of a sputum (P<.01) and blood (P<.001) cultures, antibiotic administration within 4 hours of hospital admission (P<.001), and administration of the first dose of antibiotic in the emergency department (P<.001). These measures in the control hospitals did not change significantly (P =.93, .08, .79, and .52, respectively) during the 2 periods. CONCLUSIONS: Improvements in processes of care achieved by the intervention hospitals resulted from activities initiated because of participation in a quality improvement organization-directed project. This study demonstrated the effectiveness of quality improvement activities in very small hospitals.

Adult↗
PubMed2003

Transthoracic impedance does not decrease with rapidly repeated countershocks in a swine cardiac arrest model.

STUDY PURPOSE: Successful defibrillation is dependent upon the delivery of adequate electrical current to the myocardium. One of the major determinant of current flow is transthoracic impedance. Prior work has suggested that impedance falls with repeated shocks during sinus rhythm. The purpose of this study was to evaluate changes in transthoracic impedance with repeated defibrillation shocks in an animal model of cardiac arrest due to ventricular fibrillation (VF). METHODS: VF was electrically induced in anesthetized swine. After 5 min of untreated VF, monophasic or biphasic waveform defibrillation was attempted using a standard sequence of 'stacked shocks' (200, 300, then 360 J, if necessary) administered via adhesive electrodes. If one of the first three shocks failed to convert VF, conventional CPR was initiated and defibrillation (360 J) attempted 1 min later. Strength-duration curves for delivered voltage and current were measured during each shock and transthoracic impedance calculated. Animals requiring a minimum of four shocks were selected for study inclusion. Impedance data from sequential shocks were analyzed using mixed linear models to account for the repeated-measures design and the variability of the initial impedance of individual animals. RESULTS: Thirteen animals (monophasic waveform, n=7, biphasic waveform, n=6) required at least four shocks to terminate VF (range 4-6). Transthoracic impedance did not change from the first shock in the 13 animals (46+/-8 Omega) to the fourth shock (46+/-9 Omega). In animals receiving more than four shocks, transthoracic impedance likewise did not change significantly from the first to the last shock, which terminated VF. The lack of a significant change in impedance was also observed when animals were analyzed according to defibrillation waveform. CONCLUSION: Transthoracic impedance does not change significantly with repeated shocks in a VF cardiac arrest model. This is likely due to the lack of reactive skin and soft tissue hyperemia and edema observed in non-arrest models.

Animals↗
PubMed2003

Rapid electrochemical detection and identification of catalase positive micro-organisms.

The rapid detection and identification of bacteria has application in a number of fields, e.g. the food industry, environmental monitoring and biomedicine. While in biomedicine the number of organisms present during infection is multiples of millions in the other fields it is the detection of low numbers of organisms that is important, e.g. an infective dose of Escherichia coli O157:H7 from contaminated food is less than 100 organisms. A rapid and sensitive technique has been developed to detect low numbers of the model organism E. coli O55, combining Lateral Flow Immunoassay (LFI) for capture and amperometry for sensitive detection. Nitrocellulose membranes were used as the solid phase for selective capture of the bacteria using antibodies to E. coli O55. Different concentrations of E. coli O55 in Ringers solution were applied to LFI strips and allowed to flow through the membrane to an absorbent pad. The capture region of the LFI strip was placed in close contact with the electrodes of a Clarke cell poised at +0.7 V for the detection of hydrogen peroxide. Earlier research identified that the consumption of hydrogen peroxide by bacterial catalase provided a sensitive indicator of aerobic and facultative anaerobic microorganisms numbers. Modification and application of this technique to the LFI strips demonstrated that the consumption of 8 mM hydrogen peroxide was correlated with the number of microorganisms presented to the LFI strips in the range of 2 x 10(1)-2 x 10(7) colony forming units (cfu). Capture efficiency was dependent on the number of organisms applied and varied from 71% at 2 x 10(2) cfu to 25% at 2 x 10(7) cfu. The procedure was completed in less than 10 min and could detect less than 10 cfu captured from a 200 microl sample applied to the LFI strip. The approached adopted provides proof of principle for the basis of a new technological approach to the rapid, quantitative and sensitive detection of bacteria that express catalase activity.

Biosensing Techniques↗
PubMed2003

Is the ACLS score a valid prediction rule for survival after cardiac arrest?

UNLABELLED: The ACLS (advanced cardiac life support) Score was previously developed to predict survival from out-of-hospital cardiac arrest. Whether the arrest was witnessed, initial cardiac rhythm, performance of bystander cardiopulmonary resuscitation (CPR), and the response time of the paramedic unit were determined to be predictive of survival. However, the ACLS Score has not been validated in other emergency medical services systems. OBJECTIVES: The purpose of this study was to externally validate the ACLS Score in one patient population. METHODS: This was a retrospective cohort study performed at an urban county teaching hospital. The study population consisted of consecutive adult patients treated for out-of-hospital, nontraumatic cardiac arrest, and transported to the authors' institution between November 1, 1994, and September 30, 2001. Patient records for all cardiac arrests during the study period were reviewed. Study variables included witnessed arrest, initial arrest rhythm, bystander CPR, paramedic response time, and survival to hospital discharge. Predicted probability of survival to hospital discharge was calculated for each patient using the ACLS Score. The overall predicted and observed survival rates were compared using Flora's Z score. The Hosmer-Lemeshow test was used to evaluate the model's goodness-of-fit over a range of survival probabilities. RESULTS: Of 754 cardiac arrest patients enrolled in the study period, 575 (76%) patients had documentation that allowed scoring using the ACLS Score. Twenty-five (4%) patients survived to hospital discharge. The predicted number of survivors based on the ACLS Score was 104 (18%), yielding a Flora's Z statistic of -4.46 (p < 0.0001). After categorizing predicted survival probabilities into four categories, the resulting Hosmer-Lemeshow statistic was 210 (p << 10(-6)). Both goodness-of-fit statistics demonstrated extremely poor fit of the model. A receiver operating characteristic (ROC) curve was created, yielding an area under the ROC curve of 0.33 (95% CI = 0.19 to 0.47), signifying extremely poor discrimination. CONCLUSIONS: The previously published ACLS Score was not valid when applied to an external cohort of out-of-hospital cardiac arrest patients. An externally valid model is needed to predict survival to hospital discharge following out-of-hospital cardiac arrest.

Advanced Cardiac Life Support↗
PubMed2003

Tools for the measurement of outcome after minor head injury in children: summary from the Ambulatory Pediatric Association/EMSC Outcomes Research Conference.

This article summarizes discussions held during a conference on outcomes research in emergency medical services for children. It provides detailed information on existing outcome measures for pediatric minor head injury. Benefits and/or limitations in their applicability for use in pediatric emergency medicine and pediatric minor head injury research are highlighted.

Child↗
PubMed2003

Left ventricular function after monophasic and biphasic waveform defibrillation: the impact of cardiopulmonary resuscitation time on contractile indices.

UNLABELLED: Previous work has suggested that low-energy biphasic waveform defibrillation (BWD) is followed by less post-resuscitation left ventricular (LV) dysfunction when compared with higher-energy monophasic waveform defibrillation (MWD). To the best of the authors' knowledge, the effect of cardiopulmonary resuscitation (CPR) duration and total ischemia time on LV function after countershock, controlling for waveform type, has not been evaluated. OBJECTIVE: To determine the effect of CPR duration on LV function after MWD and BWD. METHODS: VF was electrically induced in anesthetized and instrumented swine. After 5 minutes of VF, the animals were randomized to MWD (n = 22) or one of two BWDs (n = 46). If countershock terminated VF but was followed by a nonperfusing rhythm, conventional manual CPR without drug therapy was performed until restoration of spontaneous circulation (ROSC), defined as a systolic arterial pressure >60 mm Hg for 10 minutes without vasopressor support. Systolic LV pressure (LVP), LV dP/dt (first derivative of pressure measured over time), and cardiac output (CO) were measured at intervals for 60 minutes postresuscitation. CPR times (times to ROSC) and hemodynamic variables for the three groups were compared. Multivariable linear regression was performed to assess the contribution of defibrillation waveform, total joules, and CPR time on LVP, LV dP/dt, and CO at 15, 30, and 60 minutes postresuscitation. RESULTS: When analyzed as groups, significant differences in median number of shocks to terminate VF, total joules, or CPR time were not observed between waveform groups. Regression analysis demonstrated that increasing CPR time was associated with a significant effect on indices of LV function at 15 and 30 minutes postresuscitation. Global LV function was not influenced by waveform type or total joules. CONCLUSIONS: Adjustment for CPR time, a determinant of total myocardial ischemia time, is necessary when defibrillation waveforms are compared for their effect on postresuscitation cardiac function and short-term outcome.

Animals↗
PubMed2002

Endotracheal drug administration during out-of-hospital resuscitation: where are the survivors?

BACKGROUND: Drugs administered endotracheally are effectively absorbed during normal spontaneous cardiac activity. However, animal cardiac arrest studies and limited clinical investigations do not support either the use of endotracheal (ET) drugs in doses currently recommended for adults or the method of direct endotracheal instillation. The purpose of this study was to compare the effect of intravenous (IV) and ET drug therapy on outcome from out-of-hospital cardiac arrest secondary to all cardiac arrest rhythms. DESIGN: Five and one-half year retrospective cohort study. SETTING: Municipal, university affiliated hospital. PATIENTS: Consecutive patients >18 years of age in nontraumatic out-of-hospital cardiac arrest who received advanced cardiac life support (ACLS) medications by only the ET or IV route were included. INTERVENTIONS: None. RESULTS: Five hundred and ninety-six patients met inclusion criteria (IV drugs=495, ET drugs=101). There was no difference between groups in the rate of witnessed arrest and the frequency of bystander cardiopulmonary resuscitation (CPR). In the ET drug group, a significantly greater number of patients had an initial documented arrest rhythm of asystole compared to the IV drug group (56 vs 37%, P=0.01). The rate of return of spontaneous circulation (27 vs 15%, P=0.01) and survival to hospital admission rate (20 vs 9%, P=0.01) were significantly greater in the IV drug group. No patient who received ET drugs survived to hospital discharge compared to 5% of those receiving IV drugs (P=0.01). CONCLUSION: For our out-of-hospital advanced rescuer system, ET drugs at recommended doses (twice the IV dose) injected into an ET tube during cardiac arrest and CPR were of no benefit.

Adrenergic Agonists↗
PubMed2002

Use of out-of-hospital variables to predict severity of injury in pediatric patients involved in motor vehicle crashes.

STUDY OBJECTIVE: We sought to create a clinical decision rule, on the basis of variables available to out-of-hospital personnel, that could be used to accurately predict severe injury in pediatric patients involved in motor vehicle crashes as occupants. METHODS: We analyzed the National Automotive Sampling System database, a national probability sample, using pediatric patients up to 15 years old (occupants only) involved in motor vehicle crashes from January 1993 to December 1999. The National Automotive Sampling System database includes patients from regions throughout the country, weighted to represent a nationwide sample. Twelve out-of-hospital variables were used in classification and regression tree analysis to create a decision rule separating children with severe injuries (Injury Severity Score [ISS] > or =16) from those with minor injuries (ISS < 16). Misclassification costs and complexity parameters were selected to yield a decision tree with appropriate sensitivity and specificity for the identification of severely injured patients, while also being simple and practical for out-of-hospital use. Probability weights were used throughout the analysis to account for the sampling design and sampling weights. RESULTS: Using a sample size of 8,392 children, we constructed a decision rule using 3 out-of-hospital variables (Glasgow Coma Scale score, passenger space intrusion > or =6 in [> or =15 cm], and restraint use) to predict those patients with an ISS of 16 or more. Internal cross-validation was used to determine the sensitivity and specificity, yielding values of 92% and 73%, respectively, for the prediction of patients with an ISS of 16 or more. CONCLUSION: Out-of-hospital variables available to field personnel could be used to effectively triage pediatric motor vehicle crash patients using the decision rule developed here. Prospective trials would be needed to test this decision rule in actual use.

Accidents, Traffic↗
PubMed2002

Endovascular abdominal aortic aneurysm repair with general versus local anesthesia: a comparison of cardiopulmonary morbidity and mortality rates.

PURPOSE: The purpose of this study was to compare the cardiopulmonary morbidity and mortality rates after endovascular abdominal aortic aneurysm (EAAA) repair with local anesthesia (LA) with intravenous sedation versus general anesthesia (GA). METHODS: Data from patients who underwent elective infrarenal EAAA repair between June 1996 and October 2000 were retrospectively reviewed. Patients with two or more Eagle clinical cardiac risk factors were considered to be at increased risk for a major postoperative cardiac event. Univariate and multivariate analyses for major cardiac and pulmonary morbidity and mortality rates were analyzed with respect to anesthetic type (GA versus LA), age, size of aneurysm, mean number of Eagle risk factors, and presence of two or more cardiac risk factors. RESULTS: Two hundred twenty-nine patients underwent EAAA repair. The GA (158 patients) and LA (71 patients) groups were significantly different with respect to mean age (73 versus 76 years; P =.01) and mean number of cardiac risk factors per patient (1.2 versus 1.6; P =.002). No difference was seen in the overall cardiopulmonary complication rate (13% for GA and 19% for LA; P =.3), pulmonary complication rate (3.8% for GA and 7% for LA; P =.3), or cardiopulmonary mortality rate (3.2% for GA and 2.8% for LA; P =.9). The major cardiac event rate was higher in patients with two or more Eagle risk factors (22%) versus those patients with one or less Eagle risk factors (3.4%; P <.001), irrespective of anesthetic type. In analysis of patients with one or less Eagle risk factors, no difference was seen in the major cardiac event rate by anesthetic type (3% for GA and 5% for LA; P =.6). Also, no difference was seen in major cardiac events in patients with two or more Eagle risk factors by anesthetic type (24% for GA and 22% for LA). On multivariate analysis, the mean number of Eagle risk factors per patient (P <.0001) and the presence of two or more Eagle risk factors were associated with major cardiac and cardiopulmonary complications, whereas age, size of AAA, and anesthetic type were not. CONCLUSION: No difference exists in overall cardiac and pulmonary morbidity and mortality rates after EAAA repair in comparison of GA and LA. The presence of two or more preoperative cardiac risk factors significantly increases the risk of a major postoperative cardiac event.

Aged↗
PubMed2002

Emergency department triage of patients infected with HIV.

OBJECTIVE: The emergency department (ED) and HIV specialty clinics are primary sources of care for persons infected with HIV. HIV disease may be complicated by vague and complex symptomatology, and determining the degree of illness at triage is often difficult. The goals of this project were to characterize the ED presentation of HIV-related conditions, to develop a clinical decision rule to triage HIV-infected patients, and to validate the rule in clinical practice. METHODS: The study population consisted of ambulatory patients with self-reported HIV infection who presented for care to the ED of a 553-bed public hospital that serves a medically indigent, minority population. An Illness Severity Instrument was developed by an expert panel to serve as the criterion standard for defining medical urgency for HIV-infected patients presenting to the ED for care. Two phases of the study were conducted. Data from the first phase, a noninterventional cohort study, were used to develop a clinical decision rule for the ED triage of HIV-infected patients. The second phase was a prospective validation of the clinical decision rule. RESULTS: During phase I, data from 542 patient visits were collected. Data from 441 (81%) patient visits were used in a classification and regression tree (CART) analysis to produce a decision rule, the Clinical Triage Instrument. During phase II, the prospective validation of the Clinical Triage Instrument, 156 patient visits occurred. Of these, 88 (56%) patient visits were triaged using the Clinical Triage Instrument and could be scored using the Illness Severity Instrument. The Clinical Triage Instrument accurately triaged 45 [51%; 95% confidence interval (95% CI) = 40% to 62%] patient visits, undertriaged 11 (13%; 95% CI = 6% to 21%) patient visits, and overtriaged 32 (36%; 95% CI = 26% to 47%) patient visits. Sensitivities and specificities for determining emergent, urgent, and nonurgent medical conditions by the Clinical Triage Instrument were 56% (95% CI = 31% to 75%) and 84% (95% CI = 74% to 92%), 71% (95% CI = 55% to 84%) and 39% (95% CI = 25% to 55%), and 18% (95% CI = 6% to 37%) and 93% (95% CI = 84% to 98%), respectively. The positive and negative predictive values for determining an emergent medical condition using the Clinical Triage Instrument were 48% (95% CI = 26% to 70%) and 88% (95% CI = 78% to 95%), respectively. The positive and negative predictive values for determining a nonurgent medical condition using the Clinical Triage Instrument were 56% (95% CI = 21% to 86%) and 71% (95% CI = 60% to 81%), respectively. CONCLUSIONS: The Clinical Triage Instrument was not sufficiently accurate for clinical use. Until accurate and reliable triage methods are developed, all patients infected with HIV who present to the ED for care should receive timely evaluation and care.

Adult↗