Search PubMed⌕ Search

Biomedical subjects

J W Warren

Publications and source records attributed to J W Warren.

At least 73 records · Page 4Linked to original sources
PubMed1991

Prediction of left ventricular mass from the electrocardiogram.

Multiple stepwise regression methods were used to derive electrocardiographic (ECG) models for prediction of the echocardiographic left ventricular (LV) mass index from standard 12-lead ECG measurements using data files of 203 men and 252 women. The correlation between echocardiographic and ECG estimates of LV mass index was R2 = 0.58 for men and R2 = 0.42 for women. A separate logistic regression model was derived for classification of LV hypertrophy as a dichotomized dependent variable. This classifier chose R (aVL), T (V6), and S (V1) for men and R (aVL), T (V6), and S (I) for women and produced a moderate sensitivity (53.7% for men and 63.4% for women) and specificity (94.9% for men and 92.9% for women). We conclude that the initial performance of these and other recently developed multivariate estimators of LV mass and LV hypertrophy classifiers is promising enough to subject them to further studies to evaluate their utility as risk predictors.

Adolescent↗
PubMed1991

The catheter and urinary tract infection.

Catheter-associated bacteriuria is the most common infection acquired in hospitals and nursing homes. This infection would be even more common but for the use of the closed catheter system. Most modifications have not improved upon the closed catheter itself. However, even with meticulous care, this system will not prevent bacteriuria forever. After bacteriuria develops, our ability to limit its complications is minimal. Additionally, the catheterized urinary tract becomes a reservoir of bacteria that can be transferred to other patients. Once a catheter is put in place, one must keep two important concepts in mind: (1) keep the catheter system closed in order to postpone the onset of bacteriuria; and (2) remove the catheter as soon as possible. If the catheter can be removed before bacteriuria develops, postponement becomes prevention. However, the best prevention is not to use a urethral catheter at all. Non-device alternatives to urethral catheterization should be used whenever possible. If these are not useful or successful, then other devices might be considered. For incontinent men, a condom catheter is a useful alternative. For patients with urinary retention, intermittent or suprapubic catheterization may be options for both short-term and long-term needs. The roles of these alternatives to urethral catheters must be defined by controlled trials.

Bacterial Infections↗
PubMed1991

Prevalence and characteristics of nursing home-acquired infections in the aged.

OBJECTIVES: This study provides estimates of the prevalence of infections in all patients from a representative sample of 53 Maryland nursing homes; identifies risk factors for these infections; and describes diagnostic procedures carried out. METHODS: The records of 4,259 patients in a stratified random sample of 53 Maryland nursing homes were reviewed for diagnostic procedures, medical, functional, and behavioral status. Infections were identified by signs, symptoms, and laboratory findings. RESULTS: Study patients were characteristic of aged patients in US nursing homes. The prevalence of infections actually acquired in the nursing home (80% of all infections) was 4.4%. Multivariate analysis revealed that skin infections (35% of nursing home-acquired infections) were associated with skin ulcers and inversely with urine incontinence. Fevers of uncertain source (13%) were associated with bladder catheters. Symptomatic urinary infections (12%) and lower respiratory infections (12%) were associated with bedfast status, and the latter with tracheostomy and lung disease. Skin ulcers, urethral catheters, and bedfast status were markers for nursing home-acquired infection. The prevalence of infection in patients with all three markers was 32%; in patients with none, 2%. Fewer than a quarter of the four most common nursing home-acquired infections received an evaluation which met minimal diagnostic criteria established by a panel of infectious disease specialists and geriatricians. Patients with dementia, those in large homes (greater than 150 beds), and those in urban homes were less likely to be evaluated in a manner meeting these criteria. CONCLUSIONS: Use of three characteristics (ie skin ulcers, urethral catheters, bedfast status) to identify patients at risk for nursing home-acquired infections may allow targeted infection surveillance and prevention programs. In addition, nursing home-acquired infections are not evaluated uniformly across patients and facilities, suggesting the need to establish, through further study, guidelines for such evaluations.

Aged↗
PubMed1991

Incidence and characteristics of antibiotic use in aged nursing home patients.

OBJECTIVE: To measure the prevalence, incidence, types, and certain characteristics of antibiotics prescribed in nursing homes. DESIGN AND SETTING: Periodic survey over 1 year of patient charts in 53 stratified, randomly selected nursing homes in the state of Maryland. PATIENTS: All patients 65 years of age or more residing in these nursing homes on the first day of study. RESULTS: Of 4,165 patients in 53 nursing homes, records over the year were satisfactory in 3,899 patients in 52 nursing homes. The prevalence of antibiotic use on the first day of the study was 8%. Over the next 12 months, observations of more than one million patient-days revealed an incidence of 0.46 antibiotic courses/100 patient-days; 54% of the 3,899 patients received at least one antibiotic course. For presumed active infections, beta lactam antibiotics were the most commonly used, 54% of antibiotic orders. For all antibiotics, urinary tract infection was the most common indication, eliciting 36% of orders including 9% for asymptomatic bacteriuria. Skin, lower respiratory, and upper respiratory infections comprised 14%-17% each. Physicians prescribed 94% of courses but documented examinations of only 44% of patients at the outset of these courses. Consensus criteria for minimal diagnostic evaluation of four selected infections were met in only 11% of episodes of infection. Although the most serious infections tended to be better evaluated than others, 31% of the former were not noted to have been examined by a physician. Three percent of orders were for prophylaxis and two-thirds of these antibiotics were administered for more than 2 days. CONCLUSIONS: Antibiotics are frequently prescribed for aged nursing home patients, often in the absence of a physician's examination and other features commonly performed in evaluation of specific infectious diseases. More than one-fifth of antibiotics prescribed by presumed active infections were for two infections usually thought not to require antibiotic therapy, "viral" upper respiratory infection (13%) and asymptomatic bacteriuria (9%). To optimize antibiotic use in nursing homes, greater attention should be directed to appropriate durations of prophylaxis for urologic, dental, and minor surgical procedures; to standards for diagnostic evaluations of common infections; and to the roles of antibiotics in upper respiratory infections and in asymptomatic bacteriuria.

Aged↗
PubMed1991

Mouse models of short- and long-term foreign body in the urinary bladder: analogies to the bladder segment of urinary catheters.

Catheter-associated bacteriuria is the most common infection occurring in hospitals, where urethral catheters are generally in place for a few days, and in nursing homes, where catheters may be in place for months or years. We developed murine models with intrabladder urinary catheters for studying complications of bacteriuria in short- and long-term catheterization. In the short-term model, a catheter segment was inserted transurethrally and lay free within the bladder lumen. Half of the animals expelled segments during a 2-to-7-day period, durations similar to catheterizations in hospitalized patients. For studies of long-term catheter use, the catheter segment was secured within the bladder by a single suture for up to 12 months. Antibiotics administered for 7 days after catheter placement and housing mice in cages with wire screen floors reduced spontaneous bacteriuria to an acceptably low incidence rate of only 7%. Proteus mirabilis bacteriuria of high concentration provoked the same complications that are common in patients with long-term catheters: acute pyelonephritis, chronic renal inflammation, and struvite stone formation. These models allow inoculation of the bacteria of interest and are suitable for studies of short- and long-term foreign body-associated bacteriuria and its complications.

Animals↗
PubMed1990

Estimation of QT prolongation. A persistent, avoidable error in computer electrocardiography.

A pooled community-based population sample of 17,139 North American children, adolescents, and adults aged from birth to 75 years was used to evaluate a variety of one-, two-, and three-parameter formulas for correction of the QT interval for heart rate throughout a wide range of heart rates in sinus rhythm. QT measurements were made by a computer program from simultaneously sampled standard 12-lead or orthogonal XYZ leads, and all QT measurements were visually verified using a high-resolution display terminal. A random subsample of 1,920 was drawn 3 times by allocating 20 subjects to each heart rate subinterval of 1 beat/min, and the performance of a set of 13 QT prediction formulas was compared by ranking them according to the Akaike Information Criterion. The traditional Bazett's square root formula failed at low heart rates and the cube root formula of Fridericia at high rates. None of the linear two-parameter functions of R-R interval or heart rate performed with adequate accuracy. The best one-parameter formula for predicted QT(QTp) was obtained by regressing the inverse of QT on heart rate, with the expression QTp(ms) = 656/(1 + 0.01 H R), and by adding the term 0.4 x Age - 25 for age-related trend correction in males 15-50 years old. Percentile population distributions for the QT index (QTI = (QT/QTp) x 100) produced a convenient and stable 98 percentile normal QT range spanning 10% above and below the population median QTI = 100 in all major subgroups by age, sex, and race.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Reasons for replacement of long-term urethral catheters: implications for randomized trials.

On any given day more than 100,000 nursing home patients have indwelling urethral catheters in place. We prospectively followed 47 such patients for almost 18 patient-years and observed 249 catheter replacements. The mean number of replacements per 100 days of catheterization was 3.1 (71% of the catheters were replaced within 30 days of insertion). Nonprescribed removal by the patient or nursing staff was the most frequent cause of replacement (43%), followed by leakage (33%) and obstruction (24%). Catheter replacements followed patient-specific patterns, with each reason for replacement being associated significantly with the reason for the prior replacement (p less than 0.001). To minimize the effect of patient-specific replacement patterns, studies of complications of catheterization that may be affected by catheter obstruction or replacement should use cross-over designs.

Aged↗
PubMed1990

The use of urethral, condom, and suprapubic catheters in aged nursing home patients.

In this study of 4,259 aged patients in 53 randomly selected nursing homes in Maryland, we found that 10% of women and 15% of men used a urine collection device. Among bedfast patients, 47% of women and 58% of men and, among patients with decubitus ulcers, 37% of women and 33% of men were using a urine collection device. The indwelling urethral catheter was the most commonly used device. Indeed, for women, few other options were available: 93% of women used this device. In women, multiple logistic regression analysis indicated that presence of a decubitus ulcer and occupation of a long-term care bed were the attributes most strongly associated with the use of the urethral catheter. Of men with urine collection devices, 43% were using the urethral catheter; poor mobility status was the characteristic most strongly associated with its use. Long-term urethral catheterization has been well studied and is associated with universal bacteriuria and with a number of complications. Options need to be further explored, particularly external urine collection devices for women. Furthermore, because urethral catheterization may be used as a management technique for decubitus ulcers, prevention of the latter may diminish the use of urethral catheters and their subsequent complications.

Activities of Daily Living↗
PubMed1990

An external urine collection device for incontinent women. Evaluation of long-term use.

Urinary incontinence is common in aged women, may precipitate nursing home admission, and may prompt use of a urine collection device, usually an indwelling urethral catheter. The safety and efficacy of a new external urine collection device for women that is affixed to the perineum by an adhesive developed for ostomy bags was evaluated. Applied to 26 aged women, 78% of 2,264 devices were leak-free for 24 hours and 49% for 48 hours. The incidence of new bacteriuria was less than half that found in our earlier studies of long-term urethral catheters in the same institution. Perineal erythema was infrequent and preexisting decubitus ulcers improved or did not change. Four patients were withdrawn, one each because of periurethral itching, diminished urine output, recurrent wetness, and fracture of the proximal femur associated with severe osteoporosis. This device may offer an alternative to urethral catheters for management of urinary incontinence but should not be used on women with urine retention and should be used with care on women with severe osteoporosis. Controlled trials must determine effects upon bacteriologic complications and health-care costs.

Aged↗
PubMed1990

Construction of a urease-negative mutant of Proteus mirabilis: analysis of virulence in a mouse model of ascending urinary tract infection.

Proteus mirabilis, a urease-producing uropathogen, causes serious urinary tract infections in humans. To specifically evaluate the contribution of urease to virulence, a mutation was introduced into P. mirabilis HI4320 by homologous recombination. Virulence was assessed in the CBA mouse model of ascending urinary tract infection. Twenty mice each were challenged transurethrally with P. mirabilis HI4320 and its urease-negative derivative (1 x 10(9) to 2 x 10(9) CFU). At 48 h animals were sacrificed and the mean log10 CFU per milliliter of urine (parent, 6.23; mutant, 4.19; P = 0.0014) or per gram of bladder (parent, 6.29; mutant, 4.28; P = 0.0002), left kidney (parent, 4.11; mutant, 1.02; P = 0.00009), and right kidney (parent, 4.11; mutant, 2.43; P = 0.036) were all shown to be significantly different. These data demonstrate a role for urease as a critical virulence determinant for uropathogenic P. mirabilis.

Animals↗
PubMed1990

Pyelonephritogenic Escherichia coli and killing of cultured human renal proximal tubular epithelial cells: role of hemolysin in some strains.

Acute pyelonephritis, a complication of Escherichia coli bacteriuria, must represent a bacterial invasion through the kidney epithelium. To study this process, we overlaid bacterial suspensions onto monolayers of cultured human kidney proximal tubular epithelial cells and measured cytotoxicity by release of lactate dehydrogenase (LDH). Thirty-four isolates cultured from patients with acute pyelonephritis were screened for the ability to cause pyelonephritis in CBA mice by transurethral challenge. The eight most virulent strains (greater than or equal to 70% of mice challenged developed greater than or equal to 10(3) CFU/g of kidney after 48 h) were selected for study. Each strain displayed mannose-resistant hemagglutination of human O erythrocytes; three strains were phenotypically and genotypically hemolytic. Pyelonephritogenic strains were significantly more cytotoxic (30.1 +/- 9.5% LDH release after 18 h) than eight fecal control strains (13.5 +/- 11.5% LDH release; P = 0.0068). We selected the most cytotoxic strain, CFT073, for further study. Sterile filtrate from this hemolytic strain was significantly more cytotoxic than was the filtrate of the fecal control strain, FN414. Transposon mutagenesis of CFT073 with TnphoA abolished hemolytic activity and cytotoxicity by both whole cells and sterile filtrate. Southern blot analysis revealed that the Tnphoa insertion mapped to the E. coli chromosomal hly determinant within a 12-kilobase SalI restriction fragment. Transformation of a nonhemolytic strain, CPZ005 with plasmid pSF4000, which carries a cloned hemolysin determinant, resulted in highly elevated cytotoxicity. Light micrographs of proximal tubular epithelial cell cultures demonstrated cell damage by pyelonephritogenic strains that was not induced by a fecal strain or the hemolysin-deficient mutant. Results indicate that pyelonephritogenic E. coli strains are more frequently cytotoxic for a putative target, that is, human renal tubular epithelium, than are fecal isolates. Hemolysin, in some strains, is apparently responsible for this cytotoxicity.

Bacterial Toxins↗
PubMed1990

Methodology of ECG interpretation in the Dalhousie program; NOVACODE ECG classification procedures for clinical trials and population health surveys.

The Dalhousie ECG Program was designed specifically for the needs of epidemiologic studies, health surveys, and clinical trials. The program logic is dynamic in that it can accommodate any combination of ECG leads, record length and sampling rate. The NOVACODE module of the program classifies ECGs according to the Minnesota Code, supplemented with new sets of logic criteria for conduction defects, acute myocardial infarction, and serial ECG changes. Improved statistical models are incorporated for enhanced detection of myocardial infarction using the Cardiac Infarction Injury Score, and for quantification of left ventricular mass estimation. It is anticipated that these program improvements will enhance its utility particularly in monitoring progression and regression of cardiac involvement in hypertensive and ischemic heart disease, and in the assessment of the effectiveness of intervention on cardiovascular disease risk factors.

Adolescent↗
PubMed1989

Clinical evaluation of an external urine collection device for nonambulatory incontinent women.

Chronic urinary incontinence is a frequent complication of a variety of neurological diseases and is a major clinical problem among the aged. Urinary incontinence may be the pivotal factor that determines whether a patient requires long-term institutional care. For management of urinary incontinence in aged, nonambulatory women use of absorbent products may not prevent decubitus ulcers, while chronic use of indwelling urethral catheters results in bacteriuria and its complications. An effective external urine collection device for women, analogous in function to the condom catheter for men, may improve care by reducing complications, averting admissions to chronic care facilities and lowering medical costs. During 125 patient-days we evaluated 63 applications of an external urine collection device on 7 incontinent women in a nursing home. Each device was allowed to remain in situ for a maximum of 48 hours. Only 14 per cent of the devices required premature replacement due to unacceptable urine leakage. The median device wear time was 48 hours. The only adverse reactions observed were minimal erythema at 2 of 63 device removals and transient periurethral edema in 1 patient, which disappeared with continued use of the device. Thus, this device, exploiting an adhesive developed for ostomy appliances, was effective in maintaining patient dryness and was not associated with severe local reactions. These results appear to warrant clinical trials for extended periods in incontinent women.

Aged↗
PubMed1989

The prevalence of urethral catheterization in Maryland nursing homes.

Urinary incontinence is common in the increasing numbers of aged people and is often the precipitating factor for nursing home admission. Recalcitrant incontinence may be managed by urethral catheters. In this study of a random stratified sample of Maryland nursing homes (4259 patients), we found that the daily prevalence of urethral catheter use in Maryland nursing homes was 7.5%. More than 80% of urethral catheter users were women. Among men, we found equal prevalences of urethral and condom catheter use. Previous studies have demonstrated long-term use of urethral catheters to be associated with almost universal bacteriuria of a polymicrobial and dynamic nature. Combining these data suggests that long-term catheter-associated bacteriuria is the most common infection in American health care facilities.

Aged↗
PubMed1989

Once-daily irrigation of long-term urethral catheters with normal saline. Lack of benefit.

Urinary incontinence is often managed with a long-term urethral catheter after other methods have failed. Such urethral catheterization is associated with polymicrobial bacteriuria, catheter obstruction, fever, bacteremia, urinary tract stones, and death. Periodic catheter irrigation is a common but untested management procedure intended to prevent catheter obstruction, fevers, and/or bacteremia. To evaluate this technique, we performed a randomized crossover trial comparing ten weeks of once-daily normal saline irrigation with ten weeks of no irrigation in 32 long-term catheterized women. The incidence of catheter obstructions and febrile episodes and the prevalence and species of bacteriuria were similar whether examined as completed crossover patients (N = 23) or as partially completed trials (N = 9). Once-daily irrigation with normal saline of long-term urethral catheters is a time-consuming and costly procedure that is unlikely to have an impact on the morbidity associated with such catheters.

Adult↗