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Biomedical subjects

K R Anderson

Publications and source records attributed to K R Anderson.

89 records · Page 5Linked to original sources
PubMed1978

Pathologic anatomy of Ebstein's anomaly of the heart revisited.

The typical textbook description of Ebstein's anomaly of the heart usually singles out and emphasizes the downward displacement of septal and posterior leaflets of the tricuspid valve. An anatomic reappraisal of this uncommon anomaly suggests that other structural abnormalities of import should be equally stressed. Among the 15 well preserved autopsy specimens in this series, enlargement of the right atrioventricular (A-V) junction and malalignment of the giant and sometimes muscularized anterior leaflet of the tricuspid valve were consistently found. In addition, massive aneurysmal dilation of the right ventricle was present in almost two thirds (9 of 15) of the hearts. Our observations raise the possibility that abnormal embryonic development of the right A-V junction may be the primary event that leads to malformation of the tricuspid valve apparatus.

Adolescent↗
PubMed1978

Ebstein's anomaly of the left-sided tricuspid valve: pathological anatomy of the valvular malformation.

The tricuspid valve is left-sided in congenitally corrected transposition of the great arteries and other cardiac malformations in which the ventricles are inverted. In an anatomical study of 20 hearts with ventricular inversion, nine were found to have Ebstein's anomaly of the left-sided tricuspid valve. These included eight with congenitally corrected transposition of the great arteries and one with a double outlet inverted right ventricle. Pathoanatomically left-sided Ebstein's anomaly differed from the classic right-sided variety in several respects: 1) the atrioventricular sulcus circumference was not increased; 2) the anterior leaflet of the valve was frequently cleft; 3) the anterior leaflet may interfere with the ventricular outflow; 4) the ventricular cavity receiving the malformed tricuspid valve was small, rather than dilated--and in congenitally corrected transposition of the great arteries, this is the systemic ventricle connected to the aorta. Significant hemodynamic dysfunction of the left-sided tricuspid valve has been reported in a high proportion of cases of congenitally corrected transposition of the great arteries, and surgical repair of the valve may be necessary. Our study suggests that surgical procedures used in classic right-sided Ebstein's anomaly, such as valve plication and annuloplasty or valve replacement with a high profile prosthesis, are not suited to the pathoanatomy of left-sided Ebstein's anomaly.

Adolescent↗
PubMed1978

Vulnerability of coronary arteries in surgery for transposition of the great arteries.

A detailed anatomic study of 82 hearts from patients operated upon for complete or congenitally corrected transposition of the great arteries revealed 12 instances of intraoperative injury to a major coronary artery. Because the coronary arterial anatomy is so variable in transposition of the great arteries, there is a significant risk of injury to them during operation. This is especially so if epicardial adhesions and scarring from previous operations obscure the surface anatomy of the heart. The most common site of injury was adjacent to incisions in the anterior surface of the right-sided ventricle, particularly in congenitally corrected transposition. Without a meticulous examination, these complications of cardiac surgery may be easily overlooked even when the hearts are examined at autopsy.

Blood Vessel Prosthesis↗
PubMed1977

A criss-cross heart. Detailed anatomic description and discussion of morphogenesis.

Hearts with criss-cross atrioventricular connections are rare. Reports in the literature describe great anatomic variations with regard to the atrioventricular connections, spatial relationships of the ventricles, and connections and spatial relationships of the great arteries. In the example described in this report, the basic anatomic picture was that of transposition of the great arteries, but the criss-cross atrioventricular valves had resulted in atrioventricular discordance; hemodynamically, therefore, the situation resembled congenitally corrected transposition. One hypothesis for this anatomic configuration is that pronounced counterclockwise rotation (as viewed from below) brought the ventricular septum into a frontal plane and altered the respective positions of the pulmonary and aortic valves from those usually seen in congenitally corrected transposition and thereby resulted in crossed atrioventricular connections. An alternative hypothesis is that in this case one of the atrioventricular valves (the anteriorly positioned valve) may represent an anomalous communication that developed early in embryogenesis and connected the left atrial appendage to the right ventricular infundibulum.

Child↗
PubMed1977

Congenital papillary tumor of the tricuspid valve. An unusual cause of right ventricular outflow obstruction in a neonate with trisomy E.

A trisomy E neonate had congenital cardiac anomalies that included a ventricular septal defect, a bicuspid aortic valve, and a congenital papillary tumor of the tricuspid valve. The large papillary tumor was responsible for severe intermittent pulmonary outflow obstruction. The cause and pathogenesis of these rare papillary tumors are unknown, but they are probably related to the more sessile varieties of congenital valvular dysplasia. The life-threatening obstruction to blood flow caused by the congenital valvular tumor probably can be alleviated by simple surgical resection. This type of tumor should be considered in the differential diagnosis of atypical forms of outflow tract obstruction.

Abnormalities, Multiple↗
PubMedDate not supplied

Laparoscopic urology: past, present, and future.

Laparoscopy has begun to have a significant impact on the management of urologic problems. Although initially limited to diagnostic pediatric problems, it has more recently been used to resolve myriad adult urologic conditions. Indeed, during the past year laparoscopic urology has moved well beyond the diagnosis of the undescended testicle and has been successfully used for pelvic lymphadenectomy, varicocelectomy, ureterolysis, drainage of a pelvic lymphocele, bladder suspension, and nephrectomy. Future applications of laparoscopy in urology may well include nephroureterectomy, cystectomy, and creation of an ileal conduit.

Humans↗
PubMedDate not supplied

Asthmatics' responses to 6-hr sulfur dioxide exposures on two successive days.

Asthmatic volunteers (N = 14) aged 18 to 33 yr with documented sensitivity to sulfur dioxide (SO2) were exposed in a chamber to 0.6 ppm SO2 for 6-hr periods on 2 successive days. Similar exposures to purified air, 1 wk later or earlier, served as controls. Subjects exercised heavily (target ventilation rate 50 L/min) for 5 min near the beginning of exposure (early exercise) and for an additional 5 min beginning after 5-hr of exposure (late exercise). At all other times, they rested. Body plethysmographic measurements and symptom questionnaires were administered pre-exposure, after each exercise period, and hourly during rest. Bronchoconstriction and lower respiratory symptoms were observed during or immediately following exercise--to a slight extent with clean air, and to a more marked extent with SO2. Bronchoconstriction and symptoms were modestly less severe on the second day of SO2 exposure than on the first day, but there were no meaningful differences in response between early and late exercise periods on either day.

Adolescent↗
PubMedDate not supplied

Controlled exposure to a mixture of SO2, NO2, and particulate air pollutants: effects on human pulmonary function and respiratory symptoms.

Exposure of 20 volunteers to sodium chloride (NaCl) aerosol or to a mixture containing NaCl plus irritant particles (zinc ammonium sulfate) and irritant gases (nitrogen dioxide and sulfur dioxide) produced no significant decrements in pulmonary function. There was a slight tendency for respiratory symptoms to be greater during the exposure to the mixture than during exposure to the NaCl aerosol alone; the differences were not statistically significant. The pollutant concentrations studied approximated worst-case ambient levels observed in the Los Angeles basin.

Adolescent↗
PubMedDate not supplied

Dose-response study of asthmatic volunteers exposed to nitrogen dioxide during intermittent exercise.

Twenty-one mildly asthmatic volunteers were exposed to 0, 0.3, 1.0, and 3.0 ppm nitrogen dioxide (NO2) in purified background air in an environmental control chamber. Exposures were separated by 1-wk periods and occurred in random order. Each lasted 1 hr and included three 10-min bouts of moderately heavy exercise (mean ventilation rate 41 L/min). Exposure temperature was near 22 degrees C and relative humidity near 50%. Specific airway resistance and maximal forced expiratory performance were measured preexposure, after the initial exercise, and near the end of exposure. Bronchial reactivity was assessed immediately following exposure, by normocapnic hyperventilation with subfreezing air. Symptoms were recorded on questionnaires before, during, and for 1-wk after each exposure. Exercise induced significant bronchoconstriction regardless of NO2 level. No statistically significant untoward response to NO2 was observed at any exposure concentration. This negative finding agrees with our previous results, but contrasts with findings elsewhere of respiratory dysfunction after exposure to 0.3 ppm. The discrepancy is presently unexplained, but it may relate to different severity of asthma in different subject groups.

Adult↗
PubMedDate not supplied

Exposures of health-care workers to ribavirin aerosol: a pharmacokinetic study.

We assessed health risks to nurses and therapists exposed occupationally to ribavirin aerosol, a known rodent teratogen, by measuring uptake as a function of exposure concentration. During a 4-d period, healthy, nonsmoking, young adult volunteers (N = 14) were exposed 4 h/d respirable ribavirin aerosol at concentrations that exceeded occupational levels. Intermittent exercise occurred during exposure, and all activities occurred in a simulated hospital room. Ribavirin was assayed in plasma, red cells, and urine; lung function and symptoms were also measured. In 7 volunteers who were exposed to 30 mg/m3 (i.e., received approximately 10% of therapeutic dose), postexposure ribavirin concentrations in plasma and urine were similar on all 4 d, averaging (0.89 mumol/l and 131 mumol/l, respectively. These concentrations decreased after exposure, with half-times of 37-39 h. Red-cell concentrations averaged 31 mumol/l on d 4, accounting for < 5% of inhaled ribavirin mass, and they remained stable for 4 d afterward. In 7 volunteers exposed to 3 mg/m3 (i.e., approximately 1% of therapeutic dose), plasma averaged 0.075 mumol/l and red cells averaged 3 mumol/l on d 4 (i.e., near detection limits). Small variations occurred in lung function, reported symptoms, and hematologic values for exposures to both 3 and 30 microgram/m3; therefore, these effects were most likely not caused by ribavirin. Typical occupational exposures to ribavirin, without recommended protective measures, should result in undetectable or barely detectable body burdens, i.e., approximately 0.1%-1% of levels reported to be toxic to laboratory animals.

Adolescent↗
PubMedDate not supplied

Chamber exposures of children to mixed ozone, sulfur dioxide, and sulfuric acid.

To help assess acute health effects of summer air pollution in the eastern United States, we simulated ambient "acid summer haze" as closely as was practical in a laboratory chamber. We exposed young volunteers who were thought to be sensitive to this pollutant mixture on the basis of previous epidemiologic evidence. Specifically, we exposed 41 subjects aged 9-12 y to mixed ozone (0.10 ppm), sulfur dioxide (0.10 ppm), and 0.6-microm sulfuric acid aerosol (100 +/- 40 microg/m3, mean +/- standard deviation) for 4 h, during which there was intermittent exercise. Fifteen subjects were healthy, and 26 had allergy or mild asthma. The entire group responded nonsignificantly (p > .05) to pollution exposure (relative to clean air), as determined by spirometry, symptoms, and overall discomfort level during exercise. Subjects with allergy/asthma showed a positive association (p = .01) between symptoms and acid dose; in healthy subjects, that association was negative (p = .08). In these chamber-exposure studies, we noted less of an effect than was reported in previous epidemiologic studies of children exposed to ambient "acid summer haze."

Air Pollutants↗
PubMedDate not supplied

Responses of older men with and without chronic obstructive pulmonary disease to prolonged ozone exposure.

We tested responses to ozone (O3) under simulated "worst-case" ambient exposure conditions. Subjects included 9 men who had severe chronic obstructive pulmonary disease (COPD) with subnormal carbon monoxide diffusing capacity (i.e., an emphysemic component) and 10 age-matched healthy men. Each subject was exposed to 0.24 ppm O3 and to clean air (control) in an environmentally controlled chamber at 24 degrees C and 40% relative humidity. Exposures were randomized, they occurred 1 wk apart, and they lasted 4 h. During each half-hour interval, light exercise occurred (i.e., average ventilation 20 l/min) for 15 min. During both control and O3 exposures, group mean symptom intensity and specific airway resistance (SRaw) increased, whereas forced expiratory performance decreased. The healthy subgroup's mean arterial oxygen saturation (SaO2) rose slightly, and the COPD subgroup's mean SaO2 declined slightly, during exercise. Group mean forced expiratory volume in 1 s (FEV1.0) declined significantly in O3 exposures, compared with controls (p approximately .01). Mean excess FEV1.0 loss after 4 h in O3 (relative to control) was 8% of the preexposure value in the COPD subgroup, compared with 3% in the healthy subgroup (p > .05 [nonsignificant]). Overall FEV1.0 loss during O3 exposures, including exercise effects, averaged 19% in the COPD subgroup, compared with 2% in the healthy subgroup (p < .001). Symptoms, SRaw, and SaO2 responses, as well as healthy subjects' postexposure bronchial reactivity, differed little between O3-exposed and control subjects. We therefore concluded that in older men with or without severe COPD, O3 causes lung dysfunction under "worst-case" ambient exposure conditions, despite older subjects' comparative unresponsiveness to O3. The combined effect of O3 and exercise on lung dysfunction is markedly greater with COPD. It is still unclear whether COPD causes an increased response to O3 per se.

Aged↗
PubMedDate not supplied

Effects of 0.2 ppm nitrogen dioxide on pulmonary function and response to bronchoprovocation in asthmatics.

To study the respiratory effects of nitrogen dioxide (NO2) at ambient concentrations, we exposed 31 asthmatic volunteers to purified air (control) and to 0.2 ppm NO2 for 2-h periods with light intermittent exercise. Bronchial reactivity (loss of forced expiratory performance in response to graded doses of methacholine chloride aerosol) was determined postexposure, using a newly developed apparatus that allowed accurate quantitation of methacholine dose. Forced expiratory performance, total respiratory resistance, and symptoms were also recorded immediately pre- and postexposure (prior to methacholine challenges). No significant direct effect of NO2 exposure on forced expiratory function or total respiratory resistance was observed. Symptoms showed a small significant (p less than 0.05) excess in purified air relative to NO2 exposures. Individual responses to methacholine varied greatly. About two-thirds of the subjects showed greater response after NO2 than after purified air, but the mean excess response was small. Mean changes attained significance in some but not all applicable statistical tests. Thus we cannot conclude unequivocally that NO2 exposure increased bronchial reactivity in this group, although there was some tendency in that direction.

Adolescent↗
PubMedDate not supplied

From paper to electron: how an STM journal can survive the disruptive technology of the Internet.

The Internet represents a different type of technology for publishers of scientific, technical, and medical journals. It is not a technology that sustains current markets and creates new efficiencies but is, rather, a disruptive technology that could radically alter market forces, profit expectations, and business models. This paper is a translation and amplification of the research done in this area, applied to a large-circulation new science journal, Pediatrics. The findings suggest that the journal of the future will be electronic, have a less volatile cost structure, be supported more by services than by content, be less able to rely on subscription revenues, and abandon certain elements of current value networks. It also provides a possible framework for other publishers to use to evaluate their own journals relative to this disruptive technology.

Advertising↗
PubMedDate not supplied

Bacterial contamination of tube-feeding formulas.

Bacterial cultures were made on tube-feeding formulas provided to 35 unselected adult patients on termination of the infusion. Bacteria were counted and identified using routine procedures. Formulas were classified as nonmanipulated, manipulated, or locally prepared. Medical records were reviewed to determine if diarrhea was present during the period that included 2 days on either side of the sampling day. A significant association was observed between the extent of bacterial contamination and the presence of diarrhea (p = 0.027). Locally prepared and manipulated formulas contained a significantly greater number of organisms when compared to nonmanipulated formulas (x2 = 17.81, p less than 0.001). Counts for two baseline and four termination cultures on locally prepared formulas exceeded the acceptable limit for coliform organisms in pasteurized milk according to public health standards. Eight additional cultures on commercial feeding formulas which were presumably sterile initially, exceeded these standards at the end of the administration period. Thus 12 of 35 formulas (34%) would not meet public health standards applicable to pasteurized milk. Use of sterile nonmanipulated formulas in a closed administration set is recommended, along with routine, periodic bacteriologic surveillance of enteral feeding programs.

Adult↗
PubMedDate not supplied

Short-term air pollution exposures and responses in Los Angeles area schoolchildren.

We studied 269 school children from three Southern California communities of contrasting air quality in two successive school years, to investigate short-term effects of ambient ozone (O3), nitrogen dioxide (NO2), or particulate matter (PM) on respiratory health. We measured lung function and symptoms twice daily for one week each in fall, winter and spring; and concurrently assessed time-activity patterns and personal exposures. Average daily personal exposures correlated with pollutant concentrations at central sites (r = 0.61 for O3, 0.63 for NO2, 0.48 for PM). Questionnaire-reported outdoor activity increased slightly in communities/seasons with higher pollution. Lung function differences between communities were explainable by age differences. Morning forced vital capacity (FVC) decreased significantly with increase in PM or NO2 measured over the preceding 24 hours. Morning-to-afternoon change of forced expired volume in one second (FEV1) became significantly more negative with increase in PM, NO2, or O3 on the same day. Predicted FVC or FEV1 loss on highest- vs lowest-pollution days was < 2%. Daily symptoms showed no association with current or prior 24-hour pollution, but increased with decreasing temperature. Parents' questionnaire responses suggested excess asthma and allergy in children from one polluted community while children in the other polluted community reported more symptoms, relative to the cleaner community. We conclude that Los Angeles area children may experience slight lung function changes in association with day-to-day air quality changes, reasonably similar to responses seen by others in less polluted areas. Although short-term pollution effects appear small, they should be assessed in longitudinal lung function studies when possible, to allow maximally accurate measurement of longer-term function changes.

Air Pollution↗