Biomedical subjects

R Sixt

Publications and source records attributed to R Sixt.

At least 37 records · Page 2Linked to original sources

PubMed1998

Administered activity of 99Tcm-DMSA for kidney scintigraphy in children.

Kidney scintigraphy using 99Tcm-dimercaptosuccinic acid (DMSA) is a common gamma camera investigation in paediatric patients. The present study deals with methods of calculating the activity to be administered to children. Our aim is to find a method of calculation which gives the same count density in the gamma camera images for all ages. Four different methods, based on body weight, height, body surface area and a theoretical model, are compared. The count density in the images of the kidneys was studied retrospectively in 85 patients aged between 3 weeks and 19.5 years. Fourteen young adults aged 22.0-31.9 years were also studied. Two of the calculation methods, based on body surface area and the theoretical model, showed no apparent age dependency (i.e. a constant count density was observed for all ages). The variation between individuals was similar with both methods, but only the body surface area method gave a count density comparable to that for the young adults. As the method based on body surface area is also easy to implement, this method is recommended.

Adolescent↗

PubMed1998

Assessment of infective urinary tract disorders.

Urinary tract infection (UTI) is common in children, particularly in the youngest age groups. There is a risk for progressive deterioration of renal function in these children if aggravating factors such as gross reflux and/or outflow obstruction of the urinary tract are present. In this review the pros and cons of available scintigraphic and radiological imaging techniques for the work-up of these children are presented. Ultrasound can be used in the acute phase to exclude obstruction but can not reliably show transient or permanent parenchymal lesions. The presence of reflux can be established with X-ray or direct nuclide cystography. The X-ray technique gives good morphological information and has a grading system with prognostic relevance. Both techniques are invasive and great care must be taken to keep the radiation burden down with the X-ray technique. Indirect nuclide cystography following a renographic study is non-invasive but has a lower sensitivity than direct techniques. More experience is needed with the indirect technique to evaluate the consequences of its apparently low sensitivity. Urography has a limited place in the acute work-up of urinary tract infection but can be used to look for renal scarring 1-2 years after an acute pyelonephritis. The 99mTc dimercaptosuccinic acid (DMSA) scan can be used during the acute UTI to show pyelonephritic lesions with good accuracy and/or during the follow-up after six months to show permanent lesions. The acute DMSA scan can be omitted. An early treatment is more important than an early scan!

Child↗

PubMed1996

Renal damage one year after first urinary tract infection: role of dimercaptosuccinic acid scintigraphy.

OBJECTIVE: The aim of this study was to determine whether age, C-reactive protein (CRP), body temperature, or results of voiding cystourethrography at diagnosis of first-time symptomatic urinary tract infection could predict the risk of renal damage as evaluated by dimercaptosuccinic acid (DMSA) scintigraphy performed 1 year after the infection. DESIGN: The study included 157 children (median age, 0.4 year, range, 5 days to 5.8 years) with first-time symptomatic urinary tract infection. In children 1 year of age or older, a body temperature of 38.5 degrees C or higher was necessary for inclusion. CRP and body temperature were measured at the time of infection, and voiding cystourethrography was performed shortly thereafter. DMSA scintigraphy was performed 1 year later in all children. RESULTS: After 1 year, 59 (38%) of the 157 children had renal damage as evaluated by DMSA scintigraphy, and of these, 28 (47%) had reflux. There was a positive correlation between renal damage and CRP, body temperature, and reflux. Children with high levels of CRP, high fever, and dilating reflux had a risk of renal damage up to 10 times higher than children with normal or slightly elevated CRP levels, no or mild fever, and no reflux. CONCLUSION: CRP concentration and body temperature at the index infection, in combination with the results of voiding cystourethrography, are useful in classifying children at high and low risk of scintigraphic renal damage 1 year after urinary tract infection.

Age Factors↗

PubMed1996

Radiopharmaceutical dosage of 99Tcm-HMPAO for cerebral blood flow SPET studies in children.

Four methods of calculating the activity of 99Tcm-hexamethylpropyleneamine oxime to be administered in cerebral blood flow investigations of children were evaluated in patient studies. Three of the methods were based on the size of the child. We also constructed a theoretical dosage model based on physiological data and attenuation effects. The aim of the study was to find a dosage calculation method that gave the same image quality for children of all ages as well as for adults. The results showed that the dosage method based on body weight is the only one of the four methods that does not exhibit an age-dependent variation in image quality and therefore this method is recommended.

Adolescent↗

PubMed1996

Influence of breathing pattern on transcutaneous oxygen and carbon dioxide tension during histamine provocation in children with bronchial asthma.

The influence of the breathing pattern on transcutaneous blood gases was evaluated in 18 boys and 8 girls 7-18 years of age, with bronchial asthma, during bronchial provocation with histamine-HCl. Transcutaneous oxygen tension (tcPO2), carbon dioxide tension (tcPCO2) and the breathing pattern assessed by the transthoracic impedance technique were continuously monitored during the provocation. At reaction, when the fall in the forced expiratory volume in 1 s (FEV1) was 20% or more, the tcPO2 fell by 15% or more below the baseline in 22/26 and by 20% or more in 14/26 children. In some children, a marked fall in the tcPO2 was already noted after the saline inhalation and the first histamine dose steps without simultaneous changes in the FEV1. This early fall in the tcPO2 correlated to changes in the breathing pattern and was interpreted as a sign of compensatory hypoventilation secondary to the hyperventilation observed during the inhalations. We conclude that transcutaneous oxygen tension can be used as an indicator of a bronchial reaction during bronchial provocation tests in children only if one takes account of the fact that the breathing pattern during the inhalation of the challenge compound per se has an effect on the oxygen tension.

Administration, Inhalation↗

PubMed1996

Early 99mTc dimercaptosuccinic acid (DMSA) scintigraphy in symptomatic first-time urinary tract infection.

During a 2 year period, 175 children below 6 years of age (median 0.4 year) with non-obstructive symptomatic urinary tract infection were studied by 99mTc dimercaptosuccinic acid (DMSA) scintigraphy. DMSA scintigraphy was performed at a median of 10 days after the start of treatment and was abnormal in 73 children (42%), equivocal in 29 (16%) and normal in 73 (42%). Reflux was seen in 27% of all children and in 38% of the renal units that were abnormal at DMSA scintigraphy. A decreasing frequency of abnormalities at DMSA scintigraphy was seen within the first 14 days after the start of treatment. C-reactive protein and grade of reflux correlated significantly with abnormal DMSA studies. To demonstrate renal involvement in acute urinary tract infection, DMSA scintigraphy should be performed within days after the start of treatment. It is noteworthy that reflux was seen in less than half of renal units with abnormal DMSA scintigraphy.

Acute Disease↗

PubMed1995

Lung function in relation to haemodynamic status after atrial redirection for transposition of the great arteries.

To assess the interplay between haemodynamic sequelae and lung function after atrial redirection for transposition of the great arteries, we investigated 15 Mustard (age 12.0-22.0 years), and 15 Senning patients (age 7.2-12.1 years). As diagnosed at cardiac catheterization and ultracardiography, 16 (11 Mustard) had major haemodynamic sequelae, including systemic ventricle dysfunction, pulmonary hypertension, pulmonary venous obstruction, systemic venous obstruction and atrial septal defects. Static and dynamic lung volumes, ventilation distribution and diffusion capacity were assessed by body plethysmography, spirometry, the single-breath nitrogen test (N2slope) and the single-breath method for diffusion capacity (DLCO) respectively. Apart from DLCO, our own reference values were used for comparison. We found small lung volumes, a high functional residual capacity, a high N2slope and a low DLCO. Tests of > 2SD in the abnormal direction were more prevalent in the Mustard group (P = 0.06) and significantly more prevalent in patients with pulmonary hypertension. Six had normal lung function tests, 15 had unclassified abnormalities, three had small lungs and three had central airway obstruction. Peripheral airway obstruction was only present in three of four subjects with moderate or severe pulmonary hypertension. The study confirms some previous reports indicating a high frequency of lung function abnormalities in these patient groups and discusses a possible relationship to haemodynamic status.

Adolescent↗

PubMed1994

Improving the accuracy of 99Tcm-mercaptoacetyltriglycine clearance by using two blood samples instead of one? Paediatric Task Group of the EANM.

From a database of 133 patients (98 children and 35 adults) who underwent multiple blood sampling for 99Tcm-mercaptoacetyltriglycine (MAG3) clearance, we determined simplified algorithms allowing the estimation of clearance. A one-compartment model with two blood samples was applied. The best choices for the adult population were the 12 and 90 min blood samples, giving a standard error of the estimate (S.E.E.) of less than 10 ml min-1 1.73 m-2; for the children, the 10 and 80 min blood samples gave a S.E.E. of 20 ml min-1 1.73 m-2; for both the adults and the children, the 10 and 70 min blood samples gave the best results with, however, a S.E.E. of 19 ml min-1 1.73 m-2. The use of such a combined algorithm will therefore result in a degradation of the results in adults, suggesting that a separate algorithm for each group is preferable. We compared the accuracy of the two blood sample method to the one blood sample method based on previously published algorithms for children and adults, respectively. The S.E.E. was significantly lower, in adults as well as in children, using the empirical two blood sample method. This two blood sample method seems potentially useful for routine practice in adult patients. The advantages of using such a method in children is balanced by the practical problems inherent in the need to take a second blood sample during the first 10 min, at a time when the plasma activity is rapidly decreasing.

Adult↗

PubMed1994

Effects of salbutamol inhalations on transcutaneous blood gases in children during the acute asthmatic attack: from acute deterioration to recovery.

Nine children, 7-16 years of age, were studied repeatedly during an acute asthmatic attack, from acute deterioration to recovery. The transcutaneous blood gases, forced expiratory volume in 1 s (FEV1) and maximum expiratory flow when 25% of vital capacity remained to be expelled (MEF25) were monitored before and after salbutamol inhalation. The flow-volume variables were markedly impaired in the acute phase but improved gradually by the time of recovery. The transcutaneous PO2 (tcPO2) decreased in the acute and early recovery phase but improved by the late recovery phase. In the acute phase, the salbutamol inhalations increased the FEV1, indicating an improvement in central airway function, but also reduced the MEF25 and tcPO2 in some of the children. The changes in tcPO2 after the inhalations correlated with the changes in MEF25 (p < 0.001), thereby indicating a common denominator, probably the condition of the peripheral airways. In the recovery phase, the FEV1, MEF25 and tcPO2 improved after the inhalations (p < 0.05). In conclusion, transcutaneous PO2 can be used to evaluate the effects of treatment in children with acute asthmatic symptoms and may add information about peripheral airway function which may prove particularly valuable in small children where few methods are available for such measurements.

Acute Disease↗

PubMed1994

Normalization of glomerular filtration rate in children: body surface area, body weight or extracellular fluid volume?

UNLABELLED: Glomerular filtration rate (GFR) is usually expressed in relation to body surface area (BSA) for standardization and comparison between individuals of different sizes, although relating it to extracellular fluid volume (ECV) is technically much simpler because the ratio GFR/ECV is almost equal to the rate constant of the second exponential of the 51Cr-EDTA plasma clearance curve. The aim of this study was to investigate the physiological validity of expressing GFR in relation to ECV by comparing it with GFR normalized for BSA and body weight. METHODS: GFR was measured from a five-sample 51Cr-EDTA plasma clearance curve. After appropriate scaling, the rate constant of the terminal exponential is equal to GFR/ECV. RESULTS: GFR normalized by any of the three variables increased between 0-6 mo, but was less in the case of GFR/weight compared with the other two. From 6 to 24 mo, GFR/BSA continued to increase, whereas GFR/ECV and, in particular, GFR/weight remained relatively constant. It appears that as the child grows to age 6 mo, weight outstrips BSA and ECV but is followed by GFR. From 6 to 24 mo, weight, ECV and GFR increase at a faster rate than BSA. By applying regression analysis to the curves of GFR and its normalization variables versus age, expected (e) and relative (r, i.e., observed/expected) values were obtained for each patient. In the age group 6-24 mo, but not 0-6 mo, r[GFR/ECV] was significantly closer to e[GFR/ECV] than the corresponding comparisons with r and e[GFR/BSA] (p < 0.001) and r and e[GFR/weight] (p < 0.002), supporting the hypothesis that as ECV deviates from the expected value for the patient's age, it tends to be followed by GFR. CONCLUSION: Our data show that ECV is the optimal normalization variable in children, particularly those over the age of 6 mo.

Aging↗

PubMed1993

Respiratory resistance and transcutaneous PO2 during histamine provocation in children with bronchial asthma.

Bronchial reactivity was assessed in 66 children with bronchial asthma (aged 8-15 years) by provocation with histamine-HCl during a symptom-free period. A significant bronchial reaction to histamine was defined as a 50% increase in the resistance of the respiratory system (Rrs) determined by the forced oscillation technique. The provocative dose causing a 50% increase in the Rrs (PD50Rrs) was interpolated from the log dose-response curve. The mean PD50Rrs was significantly lower in children with asthma (0.22 mg/mL) compared with a group of healthy children in the same age range (1.55 mg/mL) (P < 0.001). In children with clinically severe asthma, the mean PD50Rrs was lower (0.13 mg/mL) than in children with mild asthma (0.34 mg/mL) (P < 0.001). Transcutaneous PO2 (PtcO2) was monitored in 25 of the children with asthma. In this group the proportion of mild and severe asthma, the baseline lung function variables, and the PD50Rrs were not significantly different from those of the whole group of children. During the reaction, the PtcO2 fell on average by 29% of the baseline value (P < 0.001); in 88% of the children, the fall in PtcO2 was 20% or more of the baseline value. We conclude that histamine provocation tests using the forced oscillation technique and transcutaneous PO2 to assess a bronchial reaction have a good discriminatory capacity for different degrees of clinical severity of asthma in children.

Adolescent↗

PubMed1993

Determination of the technetium-99m mercaptoacetyltriglycine plasma clearance in children by means of a single blood sample: a multicentre study. The Paediatric Task Group of the EANM.

A multicentre European study was undertaken in order to determine a reasonable algorithm allowing the determination of overall technetium-99m mercaptoacetyltriglycine clearance using a single blood sample. Employing multiple blood sample clearance as a reference method, it was shown that an acceptable estimation of the MAG3 renal clearance could be obtained using a blood sample taken at any time between 30 and 40 min after tracer injection. After correction for body surface area, comparison of clearance determined using (a) the single blood sample and (b) the multiple blood samples provided a coefficient of correlation of 0.949 and an SEE of 27 ml/min. This algorithm is valid for clearance values higher than 100 ml/min/1.73 m2 and for children older than 1 year of age.

Algorithms↗

PubMed1992

Transcutaneous blood gas monitoring during salbutamol inhalations in young children with acute asthmatic symptoms.

The effect of salbutamol inhalations on transcutaneous blood gases was investigated in 23 children (aged 11 months-2.5 years) with asthmatic symptoms. After one salbutamol inhalation there was a mean increase in transcutaneous PO2 (tcPO2) of 0.5 kPa (P less than 0.01); after a second dose given 30 minutes later, the mean increase was 1.2 kPa (P less than 0.001). The increase in tcPO2 after only one dose of salbutamol was significantly correlated to age (P less than 0.01). No such correlation was observed after a second dose. The overall increase in tcPO2 after two salbutamol inhalations showed a negative correlation to the duration of the current symptomatic period (P less than 0.05). We conclude that salbutamol inhalations have beneficial effects in young children with acute asthmatic symptoms, even below the age of 18 months, provided that an adequate dose reaches the lung and preferably at an early stage of obstruction.

Acute Disease↗

PubMed1992

Transcutaneous and arterial blood gas monitoring during acute asthmatic symptoms in older children.

The relationship between transcutaneous and arterial blood gases was investigated in 14 children with asthmatic symptoms, aged 7-15 years, before and after the inhalation of salbutamol. The degree of bronchial obstruction was assessed by forced expiratory volume in one second (FEV1) and maximum expiratory flow when 25% of FVC remained to be expelled (MEF25). On average the transcutaneous PO2 (tcPO2) was 1.3 kPa (range, 2.6-0 kPa) lower and the transcutaneous PCO2 was 0.6 kPa (range, 0-1.5 kPa) higher than the corresponding arterial values (P less than 0.01). The difference between arterial and transcutaneous PO2 was the same over the whole range of values studied (7.5-14 kPa). After the inhalation of salbutamol, the relationship between transcutaneous and arterial blood gases was not significantly changed. Changes in transcutaneous PO2 correlated to changes in MEF25 (P less than 0.05), indicating a common denominator, probably the conditions in the peripheral airways. We conclude that the close relationship between transcutaneous and arterial blood gases, even after the inhalation of a beta-2 agonist, indicates that the transcutaneous technique can be used for monitoring acute bronchial obstruction and for evaluating the effects of treatment in children of different ages.

Acute Disease↗

PubMed1992

Evaluation of cerebrospinal fluid shunt function in hydrocephalic children using 99mTc-DTPA.

The increasing numbers and survival of children with shunt-treated hydrocephalus make it mandatory to refine the methods for cerebrospinal fluid (CSF) shunt function evaluation. Radionuclide shuntography with 99mTc-DTPA, which has proved to be a safe and effective method, was performed in eight children with suspected CSF-shunt dysfunction. Characteristic shuntography patterns were found for proximal and distal CSF-shunt catheter obstruction as well as for overdrainage and normal CSF-shunt function. Shuntography contributed to the explanation of suspected CSF-shunt dysfunction in all children investigated.

Adolescent↗

PubMed1992

Cessation of vesicoureteral reflux for 5 years in infants and children allocated to medical treatment. The International Reflux Study in Children.

A total of 401 children with severe vesicoureteral reflux (97 with grade III and 304 with grade IV) was entered into the European branch of the International Reflux Study in Children. Of these patients 37 with grade III and 43 with grade IV reflux were allocated to medical treatment as a sideline group because the reflux grade III or IV had improved to grade II or I, or it had disappeared during the preceding 2 to 6 months (median 4). Of the remaining 321 patients with persistent grade III or IV reflux 158 were randomly allocated to medical treatment of whom 3 switched to surgery. We report on 235 children treated medically (155 random medical and 80 sideline), of whom 88% had a complete 5-year followup with x-ray and/or isotope voiding cystourethrography at 6, 18, 30 and 54 months. Seven children dropped out of the study after a followup of 6 months or less, including 6 with persistent vesicoureteral reflux. Cessation of vesicoureteral reflux was observed significantly more often in children with unilateral (40 of 74, 54%) than with bilateral (18 of 154, 12%) reflux (p < 0.001). No significant difference between grades III and IV was noted. Vesicoureteral reflux ceased in 25 of 153 children (16%) from the random medical group and in 32 of 75 children (43%) in the sideline group. Of 194 children with vesicoureteral reflux detected for the first time at entry reflux resolved in 55 (28%). In only 2 of 34 children (6%) in whom vesicoureteral reflux was detected more than 1 year before entry did reflux resolve after 5 years. Among the children in whom vesicoureteral reflux either disappeared, diminished or remained unchanged the proportion with urinary tract infection recurrences was almost the same.

Child↗

PubMed1990

Lower urinary tract dysfunction in girls with untreated asymptomatic or covert bacteriuria.

A total of 50 to 80% of all girls with asymptomatic or covert bacteriuria will have recurrences after antibacterial treatment. Deficient bladder emptying is an important factor predisposing to urinary infections. We investigated lower urinary tract function in 57 girls with untreated so-called asymptomatic bacteriuria. Detailed questioning revealed a high frequency of symptoms, such as urgency and incontinence. The symptoms were not acute and no patient had dysuria. The urinary flow curve pattern indicated bladder emptying problems in 42% of the girls and residual urine of greater than 5 ml. was seen in 71%. Cystometry revealed consistent detrusor instability in 75% of the patients. Lower urinary tract dysfunction may explain the marked tendency for recurrent infection after treatment of asymptomatic bacteriuria. With a detailed history, and noninvasive determination of urinary flow and residual urine, these abnormalities are easily detected. Bladder rehabilitation may offer a new method of treatment for these patients.

Bacteriuria↗

PubMed1990

Respiratory sequelae and lung function after whooping cough in infancy.

The lung function of 31 children, aged 6-13 years, who had whooping cough as infants and 32 control children matched for age, sex, and residence area were compared in a community based cohort study. Family history of obstructive airway disease, smoking habits in the family, atopy, and other background factors examined were similar in the two groups. The ratios of recalled repeated acute respiratory infections did not differ among the groups. Children in the control group were slightly more involved in physical activities. History of obstructive airway disease, findings on chest radiography, and distribution of immunoglobulin concentrations, including IgE, did not differ significantly. Lung function before and after exercise and after inhalation of salbutamol were not different. No impairment of small airways was detected. Our data do not support the hypothesis that whooping cough in itself is a causal factor for later obstructive respiratory disease.

Adolescent↗