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Biomedical subjects

F R Lewis

Publications and source records attributed to F R Lewis.

At least 19 recordsLinked to original sources
PubMed1995

Are universal precautions realistic?

In concluding whether universal precautions are necessary, it certainly appears that we need something to reduce the significant problem of HIV transmission to health-care providers. As occupational risk goes, it exceeds the occupational risk of a number of other high-risk professions. Unfortunately, we do not know if universal precautions are effective. We also do not know the true compliance rate in use of universal precautions, nor whether they have an impact on transmission even if effectively used. What are the alternatives? They are not great, but some have not been adequately explored or implemented. Re-engineering around needle use in the hospital is clearly the most likely area to produce concrete results, because needlesticks are overwhelmingly the greatest source of infection, but this has not been encouraged to the degree it could be, even with systems already developed. Universal testing does not appear to be a viable alternative, for numerous reasons already discussed. Finally, are universal precautions more important for other pathogens than HIV? I would say yes. Hepatitis B, hepatitis C, and nosocomial infections are more important both as public health issues and as health-care provider prevention issues. If universal precautions are effective in reducing any of these, they are worthwhile.

HIV Infections↗
PubMed1995

Epidemiology of injuries by needles and other sharp instruments. Minimizing sharp injuries in gynecologic and obstetric operations.

Surgical and obstetric HCWs and epidemiologists will benefit from working together to describe the frequency and circumstances of percutaneous injuries in operating and delivery rooms. Rates of percutaneous injury vary among institutions, and attending and resident surgeons are among those at greatest risk for injury. Gynecologic surgery appears to have one of the highest rates of injury of the surgical specialties, and rates of injury vary by procedure within a given specialty. Suture needles cause the majority of injuries. Certain actions such as holding tissue while suturing or cutting are associated with a higher risk of injury. Many percutaneous injuries appear to be preventable. Epidemiologic data can be used to develop strategies based on the industrial hygiene model to reduce the incidence of percutaneous injury and to collect and disseminate data on the efficacy of new preventive measures. Potentially safer instruments and suture needles, technique modification strategies, and personal protective equipment such as cut-resistant gloves and finger protective strips are now available. Scientific assessment is needed of these and other new measures to determine whether they will decrease the risk of percutaneous injury, be acceptable to users, be cost effective, and avoid adverse consequences to patients or HCWs.

Accidents, Occupational↗
PubMed1994

Effect of interferon gamma on infection-related death in patients with severe injuries. A randomized, double-blind, placebo-controlled trial.

OBJECTIVE: To assess the efficacy of interferon gamma in reducing infection and death in patients sustaining severe injury. DESIGN: Multicenter, randomized, double-blind, placebo-controlled trial with observation for 60 days and until discharge for patients with major infection on day 60. SETTING: Nine university-affiliated level 1 trauma centers. PATIENTS: Four hundred sixteen patients with severe injuries, assessed by Injury Severity Score and degree of contamination. INTERVENTION: Recombinant human interferon gamma, 100 micrograms, was administered subcutaneously once daily for 21 days (or until patient discharge if prior to 21 days) as an adjunct to standard antibiotic and supportive therapy. MAIN OUTCOME MEASURES: Incidence of major infection, death related to infection, and death. RESULTS: Infection rates were similar in both treatment groups; however, patients treated with interferon gamma experienced fewer deaths related to infection (seven [3%] vs 18 [9%]; P = .008) and fewer overall deaths (21 [10%] vs 30 [14%]; P = .17). While 12 early deaths (days 1 through 7) occurred in each treatment group, late death occurred in 18 placebo-treated patients and nine in interferon gamma-treated patients. The results were dominated by findings at one center, which had the highest enrollment and higher infection and death rates. Statistical analysis did not eliminate the possibility of an unidentified imbalance between arms as an explanation for the results. CONCLUSION: Further evaluation is required to determine the validity of the observed reduction in infection-related deaths in patients treated with interferon gamma.

Adolescent↗
PubMed1994

Changes in oxygen consumption relative to oxygen delivery in endotoxemic dogs given adrenergic agents.

Adrenergic agents (AAs) have been used in critically ill patients to increase oxygen delivery (DO2). Associated parallel increases in oxygen consumption (VO2) have been noted and are thought to represent improved tissue oxygen utilization at supraphysiologic levels of DO2. We hypothesize that the increase in VO2 associated with the use of AAs in septic animals is secondary to direct, obligate, metabolic effects of the agents themselves. In this study, mongrel dogs were anesthetised, paralyzed, and had minimum temperature maintained on a warming blanket. Pulmonary and systemic hemodynamics were monitored. DO2 was calculated, while VO2 was measured directly with a metabolic cart. All dogs were given an Escherichia coli challenge and a colloid fluid resuscitation. Two hours after the onset of endotoxemia, baseline values were obtained, followed by four progressively larger doses of saline, dobutamine, or dopamine. At each dose there was a 40-min stabilization period and a 20-min measurement of hemodynamics and VO2. Data were analyzed using analysis of variance with a Scheffe's S test. P values of < 0.05 were considered significant. The control group slowly decreased VO2 during the 6-hr experiment to 73% of baseline. Dobutamine increased VO2 to 119% of baseline (31% above control) and dopamine to 111% of baseline (28% over control). We conclude that adrenergic agents cause a significant increase in whole body VO2 at moderate doses in septic dogs. It is likely, therefore, that the "pathologic" relationship between VO2 and DO2 described in critically ill patients is partially due to the direct metabolic effects of AAs.

Acid-Base Equilibrium↗
PubMed1994

The effects of adrenergic agents on oxygen delivery and oxygen consumption in normal dogs.

This study measured changes in whole body Do2 and Vo2 caused by the administration of exogenous adrenergic agents given at physiologically relevant doses. Using 25-kg nonseptic dogs, we calculated Do2 and directly measured Vo2 in six groups (saline control, colloid fluid challenge, dopamine, dobutamine, norepinephrine, and epinephrine). The dogs were anesthetized with isoflurane, paralyzed, and maintained at a minimum baseline temperature of 37 degrees C. Measurements were taken at six time points: baseline, after each of four successively larger doses of drug, and after a recovery period. Our results demonstrated no significant changes in Vo2 in either the saline control or colloid challenge groups over the 6-hour experiment despite marked increases in cardiac output and oxygen delivery during colloid challenge. At the maximum dose used, adrenergic agents increased Vo2 by the following: dopamine, 56%; dobutamine, 51%; norepinephrine, 43%; epinephrine, 61%. We conclude that adrenergic agents cause a significant increase in whole body Vo2 at moderate doses in normal dogs.

Animals↗
PubMed1994

Prevention of venous thromboembolism in trauma patients.

Trauma patients are at risk for thromboembolic complications, but effective methods of prophylaxis have not been established for this heterogenous population. In this prospective trial, 400 trauma patients were assigned to one of three groups, depending upon their injuries, and randomized within each group to a treatment mode: Group I: sequential gradient pneumatic leg compression (SCD), low-dose subcutaneous heparin (H), or control (C); Group II: H or C; Group III: SCD or C. Venous duplex ultrasound examinations were performed on admission and weekly thereafter. Of the 251 patients who completed the study, 15 (6%) developed lower extremity venous thrombosis and two additional patients developed pulmonary embolism (one fatal). Significant risk factors associated with the development of thromboembolism included immobilization > 3 days, age 30 years or older, and the presence of pelvic or lower extremity fractures. In patients with neurotrauma who cannot receive heparin (Group III), the SCD was more effective than control in preventing DVT (p = 0.057). Neither H nor SCD appeared to offer protection for the other groups of trauma patients, but surveillance with ultrasound examinations allowed for prompt recognition and treatment of occult deep vein thrombosis.

Adolescent↗
PubMed1992

The Surgical Infection Society's policy on human immunodeficiency virus and hepatitis B and C infection. The Ad Hoc Committee on Acquired Immunodeficiency Syndrome and Hepatitis.

The Ad Hoc Committee on Acquired Immunodeficiency Syndrome and Hepatitis of The Surgical Infection Society has outlined its policy regarding three deadly blood-borne viral infections. The risk of transmission of these microbes, the role of preoperative testing, the problem of the human immunodeficiency virus-infected surgeon, and conduct in the operating room are discussed.

General Surgery↗
PubMed1992

Can adult trauma surgeons care for injured children?

Large urban trauma centers care for injured children as well as adults in many areas of the country, but the quality of care in these hospitals has not been evaluated versus that available at pediatric trauma centers. The recent validation of TRISS methodology in pediatric populations allowed us to evaluate the quality of pediatric trauma care being provided in a level I trauma center treating injured patients of all ages. We reviewed the records of 353 injured children (aged 0-17 years) who were admitted to our trauma center over a 30-month period for the following data: demographics, mechanism of injury, initial physiologic status (RTS), surgical procedures required, need for intensive care, nature and severity of the injuries (ISS), and outcome. TRISS analysis allowed us to compare our population with the Major Trauma Outcome Study. Only two of the 21 total deaths (overall mortality, 6%) were unexpected, and there were seven unexpected survivors. One hundred twenty-one patients underwent emergency surgical procedures and 63 required admission to the intensive care unit. The Z scores ranged from +0.32 for the children aged less than 2 years to +3.98 for the older age group (14-17 years). We conclude that the quality of care for pediatric trauma patients admitted to trauma centers that care for patients of all ages compares favorably with national standards. In most areas of the country, improvements in pediatric trauma care will likely come from addressing the special needs of injured children in general trauma centers rather than from developing separate pediatric facilities.

Adolescent↗
PubMed1991

Relationship between skin fluorescence and blood flow in normal and in chronically ischemic subjects dosed with fluorescein.

To elucidate parameters diagnostic of chronic ischemia, the fluorescence of skin on the foot, leg, arm, and forehead of six chronically ischemic patients and six normal subjects injected with fluorescein was measured serially using a surface-measurement fluorometer (dermofluorometer). Simultaneously collected plasma samples were assayed spectrofluorometrically for unmetabolized fluorescein. The time courses of plasma fluorescein content and dermofluorometer readings were jointly analyzed by combining a standard pharmacokinetic model, a model predicting skin site from plasma concentrations of fluorescein, and a model predicting the dermofluorometer response to those skin concentrations. Fluorescein plasma clearance (0.22 +/- 0.06 versus 0.46 +/- 0.20 L/h/kg) in ischemic patients was only half, and half-life was double (2.4 +/- 1.0 versus 1.3 +/- 0.3 h) those in normal subjects, with volume of distribution (Vdss = 0.46 L/kg) being similar. Despite the ischemia diagnosis for all patients involving claudication of the lower extremities, patients could be distinguished statistically from normal subjects on the basis of fluorescence readings taken on the arm, but not those using the foot or leg. The rate constant describing flux of fluorescein from the arm skin site in patients was only half that in normal subjects, and the peak reading on the arm occurred at 42 +/- 14 min after fluorescein injection in patients, but at only 15 +/- 6 min in normal subjects. Lack of discrimination between subject groups via leg and foot readings may be due to several physiologic and/or experimental factors, including the need to take skin surface readings much earlier than previously recognized.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Iodinated contrast media effects on extravascular lung water, central blood volume, and cardiac output in humans.

Intravascular contrast media produce pulmonary edema in one rat model, but not in dogs or pigs. In humans, pulmonary edema after contrast media is rarely diagnosed, but subclinical edema could be more frequent than believed previously. Therefore, the authors prospectively studied the effects of diatrizoate (n = 5) and ioxaglate (n = 5) on extravascular lung water, central blood volume, and cardiac output in ten patients undergoing routine radiographic procedures. Variables were measured by thermal-dye dilution before and every 5 minutes after completion of the procedure for four repetitions. Extravascular lung water and central blood volume did not change significantly, indicating that pulmonary edema or pulmonary congestion did not occur. Cardiac output was elevated by 10.6% immediately after the procedure, but returned to baseline during the 10 following minutes. The authors conclude from this preliminary study in a small number of patients that intraarterial contrast media (less than 1.5 g/kg body weight of iodine) did not produce pulmonary edema or pulmonary congestion, even at a subclinical level.

Blood Volume↗
PubMed1990

Independence of intrapericardial right and left ventricular performance in septic pulmonary hypertension.

To study the effect of septic pulmonary hypertension on right/left ventricular intrapericardial interactions thirteen trauma patients, seven septic and six non-septic controls, were compared. Ventricular volumes were derived from first-pass or gated equilibrium radionuclide angiocardiography, and related to body surface area. Systemic and pulmonary pressures were measured invasively. Pulmonary arterial pressure was significantly increased in the sepsis group. Although right ventricular end-diastolic volumes were higher in sepsis, left ventricular end-diastolic volumes were not decreased. In terms of intrapericardial right/left ventricular interactions these results indicate that the right and left ventricles operate independently in septic pulmonary hypertension.

Adult↗
PubMed1989

Post-traumatic changes in, and effect of colloid osmotic pressure on the distribution of body water.

The aim of this study was to define the post-traumatic changes in body fluid compartments and to evaluate the effect of plasma colloid osmotic pressure (COP) on the partitioning of body fluid between these compartments. Forty-two measurements of plasma volume (green dye), extracellular volume (bromine), and total body water (deuterium) were done in ten traumatized patients (mean Injury Severity Score, ISS, = 34) and 23 similar control studies were done in eight healthy volunteers who were in stable fluid balance. Interstitial volume, intracellular volume, and blood volume were calculated from measured fluid spaces and hematocrit; COP was directly measured. Studies in volunteers on consecutive days indicated good reproducibility, with coefficients of variation equal to 3.5% for COP, 6.3% for plasma volume, 4.5% for extracellular volume, and 4.9% for total body water. COP values extended over the entire range seen clinically, from 10 to 30 mmHg. Interstitial volume was increased by 55% in patients, but intracellular volume was decreased by 10%. We conclude (1) that posttraumatic peripheral edema resulting from hemodilution is located in the interstitial compartment, with no intracellular space expansion; and (2) that interstitial volume, but not intracellular volume, is closely related to plasma COP.

Blood Proteins↗
PubMed1989

Appendicitis: continuing diagnostic challenge.

Recognition of appendicitis depends on an understanding of the underlying pathophysiology and anatomy that shape the clinical presentation. Knowledge of the clinical symptoms and signs that distinguish between appendicitis and competing diagnoses enables the clinician to differentiate appendicitis from other pathologies. Variations in anatomy, pathophysiology, symptoms, and signs are described for adult men, ovulating women, pregnant women, children, the elderly, and immunocompromised patients.

Adolescent↗
PubMed1987

Regional trauma system design: critical concepts.

Regional trauma system implementation is proceeding in a number of areas of the United States in response to a demonstrated need for improved trauma care to prevent unnecessary death. The critical questions underlying the design of such systems and the current state of knowledge and opinion regarding each of them have been defined and these provide a framework for system planning. Additional data are badly needed in several areas to provide a more rational basis for system configuration. It is hoped that systems currently being implemented will include appropriate data elements in their trauma registries to answer the remaining questions in succeeding years.

Health Facility Planning↗
PubMed1987

The role of pulmonary lymphatics in the clearance of hydrostatic pulmonary edema.

Pulmonary lymphatics are believed to play a major role in preventing the formation of pulmonary edema, but their role in clearance of established edema has not been defined. To measure the lymphatic contribution to the clearance of acute hydrostatic pulmonary edema, a lung lymph fistula was established in 16 anesthetized sheep. Pulmonary edema was induced by a rapid volume infusion of Ringer's lactate (six animals) or homologous plasma (six animals). Four control animals received no fluid. Simultaneous measurements of lymph flow and extravascular lung water (EVLW) were made. Data were analyzed for the resolution phase of pulmonary edema. The contribution of the pulmonary lymphatics to resolution was expressed as a percentage of total lung water resolved. Resolution rates for crystalloid and plasma infusion groups were 3.8 +/- 2.4 cc/kg/hr and 2.7 +/- 1.0 cc/kg/hr, respectively. There was no statistically significant difference between the groups in terms of EVLW increases or resolution rates. Net measured pulmonary lymph flow during the resolution phase of pulmonary edema was 0.33 +/- 0.18 cc/kg/hr and 0.39 +/- 0.20 and accounted for only 8.8 and 14.6% of resolved pulmonary edema in these respective groups. These data suggest the pulmonary lymphatic drainage plays a very minor role in the clearance of acute hydrostatic edema. The lungs appear to be capable of resolving as much as 40% per hour of increased extravascular lung water produced under these circumstances.

Animals↗
PubMed1987

Acute appendicitis: high-resolution real-time US findings.

High-resolution, real-time ultrasonography (US) with graded compression was used to evaluate 90 patients with clinically suspected acute appendicitis. US visualization of a noncompressible appendix was the primary criterion for a diagnosis of acute appendicitis. The overall sensitivity was 89%, the specificity was 95%, and the accuracy was 93%. When the results in women were analyzed separately (n = 49), the overall accuracy was 96%. Several important limitations of US scanning were encountered. There were three false-positive examinations in patients with a sonographically visible appendix whose symptoms spontaneously resolved. Another patient had a normal compressible appendix with a thin (2-mm), symmetric wall surrounded by ascites. There were three nondiagnostic studies (3%) due to inability to compress the cecum and right lower quadrant adequately because of exquisite tenderness (two patients) or massive ascites (one patient). When interpreted in light of the clinical examination, sonography should significantly reduce the rate of false-negative appendectomies, particularly in women.

Acute Disease↗