PubMed Health⌕ Search

Biomedical subjects

H U Bucher

Publications and source records attributed to H U Bucher.

At least 19 recordsLinked to original sources
PubMed2000

Continuous monitoring of liver oxygenation with near infrared spectroscopy during naso-gastric tube feeding in neonates.

Near infrared spectroscopy (NIRS) is a non-invasive method of estimating the haemoglobin concentration changes in certain tissues. It is frequently used to monitor oxygenation of the brain in neonates. At present it is not clear whether near infrared spectroscopy of other organs (e.g. the liver as a corresponding site in the splanchnic region, which reacts very sensitively to haemodynamic instability) provides reliable values on their tissue oxygenation. The aim of the study was to test near infrared spectroscopy by measuring known physiologic changes in tissue oxygenation of the liver in newborn infants during and after feeding via a naso-gastric tube. The test-retest variability of such measurements was also determined. On 28 occasions in 25 infants we measured the tissue oxygenation index (TOI) of the liver and the brain continuously before, during and 30 minutes after feeding via a gastric tube. Simultaneously we measured arterial oxygen saturation (SaO2), heart rate (HR) and mean arterial blood pressure (MAP). In 10 other newborn infants we performed a test-retest analysis of the liver tissue oxygenation index to estimate the variability in repeated intra-individual measurements. The tissue oxygenation index of the liver increased significantly from 56.7 +/- 7.5% before to 60.3 +/- 5.6% after feeding (p < 0.005), and remained unchanged for the next 30 minutes. The tissue oxygenation index of the brain (62.1 +/- 9.7%), SaO2 (94.4 +/- 7.1%), heart rate (145 +/- 17.3 min-1) and mean arterial blood pressure (52.8 +/- 10.2 mm Hg) did not change significantly. The test-retest variability for intra-individual measurements was 2.7 +/- 2.1%. After bolus feeding the tissue oxygenation index of the liver increased as expected. This indicates that near infrared spectroscopy is suitable for monitoring changes in tissue oxygenation of the liver in newborn infants.

Blood Pressure↗
PubMed2000

Can near infrared spectroscopy of the liver monitor tissue oxygenation?

Measurement of the hepatic oxygenation index by near infrared spectroscopy is a suitable method to estimate the oxygenation and can be a non-invasive means to continuously monitor tissue perfusion and to detect early haemodynamic disturbances in critically ill children.

Child, Preschool↗
PubMed2000

Artificial sweetener reduces nociceptive reaction in term newborn infants.

BACKGROUND: Sucrose has been shown to have an analgesic effect in preterm and term neonates. Sucrose, however, has a high osmolarity and may have deleterious effects in infants with fructose intolerance. Furthermore, it may favour caries. We therefore investigated the effects of a commercially available artificial sweetener (10 parts cyclamate and 1 part saccharin), glycine (sweet amino acid) or breast milk in reducing reaction to pain as compared with a placebo. SUBJECTS: Eighty healthy term infants, four days old, with normal birth weight. INTERVENTIONS: The infants were randomly assigned to one of four groups: 2 ml sweetener, glycine, expressed breast milk or water were given 2 min before a heel prick for the Guthrie test. The procedure was filmed with a video camera and analysed by two observers who did not know which medication the infant had received. RESULTS: Using a multivariate regression analysis, the following variables had significant correlation with relative crying time and recovery time: behavioural state before the intervention, the pricking nurse, and the type of medication. Relative crying time and recovery time were significantly less in the sweetener group but not in the glycine and the breast milk group. CONCLUSIONS: The artificial sweetener used in our study reduces pain reaction to a heel prick in term neonates, and thus provides an alternative to sucrose. In contrast, glycine tends to increase pain reaction whereas breast milk has no effect.

Analgesics↗
PubMed2000

Tissue oxygen saturation measured by near infrared spectrophotometry correlates with arterial oxygen saturation during induced oxygenation changes in neonates.

The aim of this study was to compare quantitatively the changes in tissue oxygen saturation (TOS), determined by two algorithms (TOSc and TOSa) based on near-infrared spectrophotometry, to the changes in arterial oxygen saturation (SaO2) measured by pulse oximetry. TOSc is an algorithm derived by the manufacturer (Critikon) based on a modified Beer-Lambert law; TOSa, our own algorithm, uses the diffusion approximation of light transport for the semi-infinite boundary condition. Slow changes of more than 3% in SaO2 were carried out in 20 mechanically ventilated neonates by altering the inspired oxygen fraction. For each change the regression lines of TOSc versus SaO2, TOSa versus SaO2 and TOSc versus TOSa were calculatcd. For each infant the mcan slope, intercept and r2 of these lines were determined. In 18 preterm infants we obtained median 9.5 (range one to 13) measurements corresponding to a total of 166 measurements. The mean SaO2 was 91.6 (SD 2.3)%, TOSc was 64.7 (SD 7.2)% and TOSa was 71.4 (SD 11.0)%. Changes in TOSc and TOSa were strongly correlated to changes in SaO2 (r2 = 0.86 and r2 = 0.87). TOSc considerably but systematically underestimated the size of the change: delta TOSc = 0.49 delta SaO2. TOSa quantified changes reasonably correctly: delta TOSa = 0.90 delta SaO2. Changes in TOSc and TOSa were highly correlated (r2 = 0.98). These results are promising, but the large inter-individual variation requires further work.

Algorithms↗
PubMed1999

Comparison of cerebral blood volume measured by near infrared spectroscopy and contrast enhanced magnetic resonance imaging.

Cerebral blood volume (CBV) can be quantified by both near infrared spectroscopy (NIRS) and magnetic resonance imaging (MRI). The aim is to compare CBV results obtained by NIRS and MRI in adult patients. 10 adult patients, 6 females and 4 males, age median 24 (range 21 to 76) years, were included in this study. All needed a MRI investigation with contrast medium for clinical reasons. The NIRS instrument, the Cerebral RedOx Monitor 2020 from Critikon, quantifies cerebral haemoglobin concentration using a sensor with two receiving channels at different distances. Geometrical detector arrangements of this type enable a ratio measurement to be achieved, which reduces the contribution of the skull and skin, thus allowing quantification. Cerebral haemoglobin concentration can be converted in CBV, as the haemoglobin concentration in the blood is known. CBV can be quantified by MRI using an indicator dilution method. The method requires an injection of a paramagnetic contrast agent. The input function can be measured at the throat and thus perfusion images can be quantified. CBV was measured by NIRS just before the patient entered the magnet and after he had left it. The sensor for the NIRS measurement was applied to the patients front three times for 1 minute to each side, avoiding the sinuses. CBV was determined by contrast enhanced MRI between the NIRS measurements. The mean CBV (NIRS) was 8.6 (SD 1.3) ml/100 g and CBV (MRI) was 7.1 (SD 2.5). The correlation between CBV (NIRS) and CBV (MRI) was Pearson's correlation coefficient -0.297 (p = 0.204) respectively Spearman's rho (nonparametric) -0.266 (p = 0.257). The CBV values obtained by NIRS and MRI, even though they are in the same range, do not correlate.

Adult↗
PubMed1999

Cerebral blood flow and neurological outcome in the preterm infant.

UNLABELLED: Cerebral blood flow (CBF) studies have provided some insight into pathophysiological mechanisms of cerebral damage in newborn children; their value in predicting brain damage, however, remains elusive. The purpose of our study was to evaluate the role of CBF measurements in predicting developmental outcome in preterm neonates at 18 months. Preterm babies with a gestational age of less than 34 weeks and a birth weight of less than 1500 g (n = 71) were enrolled in the study. CBF was measured by the noninvasive intravenous 133Xe method on three different occasions. We classified our measurements into three groups: depending on the time when performed group 1: between 2 and 36 h (n = 52); group 2: between 36 and 108 h (n = 44); group 3: between 108 and 240 h (n = 41). At the age of 18 months neurodevelopment testing was performed according to the Bayley mental and motor scales. Surviving infants had a higher mean CBF over the three groups than non surviving children (15.2 +/- 3.5 ml/100 g brain tissue/min vs 13.0 +/- 2.1 ml/100 g brain tissue/min, P < 0.05). There was no correlation of CBF with mental or motor development in our study population in either of the three groups. CONCLUSION: In preterm infants basal CBF is higher in surviving than in non surviving infants, but there is no correlation of resting CBF and later neurological outcome.

Aging↗
PubMed1999

Cyclical fluctuations in blood pressure, heart rate and cerebral blood volume in preterm infants.

Many recently published papers describe cyclical changes of cerebral circulatory variables, mainly in cerebral blood flow velocity (CBFV) performed with Doppler sonography. In this paper we focus on another important variable of cerebral circulation: on cerebral blood volume (CBV) measured by near infrared spectrophotometry (NIRS). In a retrospective analysis of NIRS measurements in 20 preterm infants (median 27 3/7 weeks of gestation), the dominating frequencies and prevalence of cyclical changes of CBV and its possible correlation with peripheral circulatory variables (mean arterial pressure and heart rate) was examined. In 19 out of the 20 infants cyclical changes of CBV were found within a frequency range of 2-4.7 cycles/min which is comparable to the results of the Doppler studies describing fluctuations in CBFV. A dominating frequency of heart rate (HR), was found only in 12 out of 20 infants, and it was with 2.1-3.8 cycles/min in a similar range compared to CBV. In mean arterial blood pressure (MABP), however we detected cycles with longer periods every 1-2.5 min in 14 out of 20 infants. There was a significant coherence between MABP/CBV and HR/CBV. The area under the coherence curve, however, was significantly larger between MABP and CBV as compared to HR and CBV (P = 0.0007, Wilcoxon signed-rank test).

Blood Pressure↗
PubMed1999

The influence of a clear layer on near-infrared spectrophotometry measurements using a liquid neonatal head phantom.

It is difficult to test near-infrared spectrophotometry instruments in vivo. Therefore we constructed a liquid phantom which mimics the neonatal head. It consists of a spherical 3.5 mm thick layer of silicone rubber simulating skin and bone and a 0.5 mm thick clear layer of polypropylene imitating cerebrospinal fluid. It acts as container for a liquid solution with Intralipid, 60 micromol l(-1) haemoglobin and yeast. The solution was oxygenated using oxygen and then deoxygenated by the yeast. From the instrumental (Critikon 2020) algorithm, we found that with increasing scattering (0.5%, 1%, 1.5% and 2% Intralipid concentration) the reading was increasingly offset from the expected value of 0 micromol l(-1) by 55.7, 68.6, 76.5 and 80.4 micromol l(-1) (oxyhaemoglobin) and 16.0, 24.4, 29.6 and 31.7 micromol l(-1) (deoxyhaemoglobin). This reduced the range of the oxygen saturation reading from the expected 100% to 31.5, 21.1, 14.3 and 11.5%. Haemoglobin concentration changes were increasingly underestimated by a factor of two to four. For a second algorithm based on the diffusion approximation the offsets were smaller: oxyhaemoglobin 11.4, 17.8, 22.5 and 25.1 micromol l(-1) and deoxyhaemoglobin 1.3, 3.4, 5.2 and 6.0 micromol l(-1). The range of the oxygen saturation reading was higher: 41.3, 29.2, 23.4 and 16.6%. Concentration changes were underestimated by a factor of six to ten. This study demonstrates the need to develop algorithms which take into consideration anatomical structures.

Algorithms↗
PubMed1999

Regional differences of cerebral hemoglobin concentration in preterm infants measured by near infrared spectrophotometry.

Near infrared spectrophotometry has been used to measure total cerebral hemoglobin concentration (micromol/l) as a major indicator of the oxygen transport capacity in neonates. The aim of this study was to find out how the position of the probe influences the quality of the measurement and the actual cerebral hemoglobin concentration-values. We studied 10 healthy preterm infants with a mean gestational age of 31.5 weeks and a birthweight of 1513 g. The data were collected by a two channel near infrared spectrophotometry system using a geometrical principle to measure absolute cerebral hemoglobin concentration. The incoming signal of the light emitting diode as a value allows a prediction of the quality of the measurement: a high value refers to a high signal/noise ratio. Starting from the centre of the forehead (0%) for each measurement the probe was moved by 2.5% of the headcircumference to the left respectively right side of the head up to 20%. The cerebral hemoglobin concentration-values increased from 87 respectively 93 micromol/l up to 164 respectively 173 micromol/l on the right respectively left side, while the light emitting diode signal-values decreased from 21 respectively 21 down to 10 respectively 11, the more laterally the probe was moved. There were two plateaus of these variables in the frontal (0-5%) respectively lateral (15-20%) region. A further investigation on a solid phantom for premature heads showed that hair has either no or a contrary effect on the cerebral hemoglobin concentration-values than expected. The extracerebral tissue (soft tissue, skull, cerebrospinal fluid layer) is discussed to have a significant influence on the light attenuation in adult heads. Still there is no evidence for a significant effect on prematures, because this overlying tissue is much thinner and more translucent than the one in adults. Absolute cerebral hemoglobin concentration measured by near infrared spectrophotometry is substantially influenced by the position of the probe at the infant's head. Considering our results we recommend placing the probe at 2.5% of the headcircumference away from the centre of the forehead for the measurement of cerebral hemoglobin concentration in premature infants.

Brain↗
PubMed1998

[Intrauterine and postnatal transfer of high risk newborn infants. Swiss Society of Neonatology].

UNLABELLED: The centralisation of high risk deliveries in perinatal centres has become standard practice in most developed countries over the last 20 years. The goal of this study was to assess to which extent this practice has been implemented in Switzerland as well. In addition, we compared standard morbidity outcome measurements between outborn and inborn infants, as well as the frequencies of postnatal interhospital transfers. METHODS: All infants born alive either below the 32nd week of gestation, weighing less than 1500 g, or who required assisted ventilation before the 44th week of corrected gestational age were entered in a prospective epidemiological survey (Swiss minimal neonatal data set) if they had been admitted to a neonatal intensive or intermediate care unit. We analysed the data derived from infants born between 1 January and 31 December 1996. RESULTS: 86% of the 720 infants of less than 32 weeks gestation and/or less than 1500 g (group 1) were born in a perinatal centre, whereas only 27% of the 508 infants > or = 32 weeks gestation and > or = 1500 g who required assisted ventilation (group 2) were inborn. In group 1 outborn infants had a higher risk for pulmonary hypertension (odds ratio 3.7, 95% confidence interval 1.4 to 10.0), for hyperechogenic leucomalacia (odds ratio 2.7, CI 1.3-5.4), for necrotising enterocolitis (odds ratio 2.5, CI 1.1-5.7). The frequencies of postnatal interhospital transfer were the following for group 1 and 2: once 35% vs. 52%, twice or more 10% vs. 31%. CONCLUSION: 720 infants below 32 weeks gestation and/or < 1500 g were admitted to neonatal units in 1996 which corresponds to 0.86% of all liveborn infants in Switzerland. Fourteen percent of these infants were outborn with a high morbidity. Of the 508 larger and older new-born infants who required assisted ventilation (0.62% of all liveborn infants in Switzerland), 73% were outborn. It is speculated that improved prenatal identification of risk factors and prenatal transfer could further reduce the morbidity of these two populations of new-born infants.

Female↗
PubMed1998

Sleep state changes associated with cerebral blood volume changes in healthy term newborn infants.

In order to assess the possible effects of sleep states on cerebral haemodynamics in healthy term infants, we measured cerebral oxyhaemoglobin, deoxyhaemoglobin and total haemoglobin concentration using near infrared spectroscopy. Thirty-seven sleep state changes in seventeen infants (gestational age: 37 to 41 4/7 weeks), aged between two and eight days were continuously registrated during 1-3 h. Transcutaneous PaO2, PaCO2, arterial O2 saturation and heart rate were simultaneously recorded and sleep states were clinically defined. There was a close relationship between sleep state changes and changes in total cerebral haemoglobin concentration, which increased from active to quiet sleep and decreased from quiet to active sleep. Changes in total cerebral haemoglobin were due, in the most part, to changes in the cerebral oxyhaemoglobin concentration. In conclusion, sleep states influence the cerebral haemoglobin concentration. Studies on cerebral haemodynamics should take sleep state into account in term newborn infants.

Blood Volume↗
PubMed1998

Comparison of absolute cerebral haemoglobin concentration in neonates measured directly and by the oxygen swing method both based on near infrared spectrophotometry.

The total cerebral haemoglobin concentration (tHb in mumol/l) as a major indicator of the oxygen transport capacity is investigated in neonates. Two methods to determine tHb by near infrared spectrophotometry (NIRS) have evolved so far: The first method requires a slow oxygenation change with reference to arterial oxygen saturation (tHbo-method). The second method is based on a geometrical principle and a two channel NIRS instrument (tHbg-method). The aim of this study was to compare both methods quantitatively. 15 clinically stable preterm infants needing supplemental oxygen were included in this study. For each method the measurements of three infants were excluded due to unsatisfactory measurement quality. The remaining 9 neonates had a mean gestational age of 29 (range 25.1 to 31.4) weeks, birthweight of 1272 (740 to 1690) g and a postnatal age of 2.6 (0.5 to 5) days. In each infant 6 tHbo measurements were carried out. During each tHbo measurement the mean of the continuously available tHbg (Cerebral Redox Monitor 2020, Johnson & Johnson Medical) was calculated. The mean of all successful tHbo and corresponding tHbg was determined for each infant. The mean tHbg was 151 mumol/l (range 62 to 223 mumol/l) and the mean tHbo was 59 mumol/l (27 to 113 mumol/l). The regression line between the two methods was tHbg = 1.34 x tHbo + 72 mumol/l. The r was 83.6%. The correlation suggests, that both methods can be applied to measure tHb. However, it has to be taken into account that the tHbg-method returns significantly higher values than the tHbo-method.

Birth Weight↗
PubMed1997

Continuous noninvasive measurement of cerebral arterial and venous oxygen saturation at the bedside in mechanically ventilated neonates.

OBJECTIVES: To test the practicablity of a new spectrophotometric method using pulse oximetric techniques in combination with special filters for the noninvasive determination of cerebral arterial and venous oxygen saturation and oxygen extraction in neonatal intensive care unit patients. The spectrophotometer used three different wavelengths at a sampling rate of 100 Hz. DESIGN: Clinical evaluation of a new method and comparison with previously published data. SETTING: Design and construction of the special spectrophotometer at the Biomedical Engineering Laboratory of the Swiss Federal Institute of Technology. Measurements in the neonatal intensive care unit of the University Hospital, Zurich, Switzerland. PATIENTS: Convenience sample of 15 clinically stable newborn infants, who were mechanically ventilated and receiving supplemental oxygen. Median gestational age was 29 5/7 wks (range 26 3/ 7 to 36 0/7), median birth weight was 1555 g (720 to 2500), median postnatal age was 4 days (1 to 10). INTERVENTIONS: The emitter and receiver were placed on the forehead near the sagittal sinus, between 2 and 2.8 cm apart, and the pulsating light attenuations (arterial and venous pulse waves) were recorded. MEASUREMENTS AND MAIN RESULTS: Arterial and venous pulse waves were satisfactory in 10 of 15 infants. Mean cerebral arterial oxygen saturation was 89.9 +/- 5.4% (SD), mean cerebral venous oxygen saturation was 73.0 +/- 8.9%, and mean cerebral oxygen extraction was 16.9 +/- 11.7%. A linear regression analysis demonstrated a significant correlation between mean PCO2 and venous oxygen saturation (slope 1.0%/torr, p < .05) and between mean PCO2 and cerebral oxygen extraction (slope -1.3%/torr, p < .05). CONCLUSION: This new method has the potential for monitoring continuously, noninvasively, and simultaneously cerebral arterial and venous oxygen saturation and oxygen extraction in mechanically ventilated preterm infants.

Blood Gas Analysis↗
PubMed1997

Body proportionality in growth-retarded VLBW infants.

The aim of this study was to investigate how intrauterine growth retardation affects body proportions in VLBW infants. The cohort consisted of 135 surviving and 80 deceased preterm infants weighing less than 1250 grams at birth. Gestational age varied between 24 and 36 weeks (mean age 29.7 and 27.5 weeks, respectively). Birth weight was more than 2 SD below the mean birth standard values in 32% of the surviving, and in 27% of the deceased infants. Reduction of weight, length and head circumference at birth was analysed using Z scores based on Swedish birth standards. Z scores of weight, length and head circumference were highly correlated in the surviving and the deceased infants (r = 0.78 to 0.94 and 0.65 to 0.97, respectively). Length was significantly more affected by growth retardation than weight. Weight and head circumference were proportionately reduced. Intrauterine growth retardation influences body proportions in VLBW infants differently than in larger preterm and term infants.

Body Constitution↗