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Biomedical subjects

A Knudsen

Publications and source records attributed to A Knudsen.

At least 37 records · Page 2Linked to original sources
PubMed1995

Predicting the need for phototherapy in healthy mature neonates using transcutaneous bilirubinometry on the first postnatal day.

Since newborn infants are frequently sent home within 24-48 h after birth, the prediction of severe hyperbilirubinaemia, requiring treatment, is important. We tested the prediction of the need for phototherapy by measuring the yellow skin colour and the progression in yellow skin colour over 6 h using transcutaneous bilirubinometry (TcB), during the first 33 h of age. The first TcB reading at median 21 h (11-33 h, 5th and 95th percentiles) of age and the difference in readings over a 6-hour interval were reliable predictors of later phototherapy. An even better prediction was possible using the first TcB reading and the 6-hour difference in TcB readings.

Bilirubin↗
PubMed1994

The role of the L-arginine-nitric oxide pathway for peristalsis in the opossum oesophageal body.

BACKGROUND: The aim of the study was to determine the effect of NG-nitro-L-arginine (L-NNA), an inhibitor of nitric oxide (NO) synthesis, on primary peristalsis in the oesophageal body. METHODS: Peristalsis was induced by pharyngeal stroking in 14 lightly anaesthetized opossums. Oesophageal pressures were monitored with a four-channel, perfused catheter assembly and registered with external transducers 1, 4, 7, and 10 cm proximal to the oesophagogastric junction. Propagation time was the time taken for a contraction to travel between two recording sites and was determined in the proximal, middle, and distal parts of the oesophagus (propagation time between 10 and 7 cm, 7 and 4 cm, and 4 and 1 cm recording sites, respectively). RESULTS: L-NNA (10(-7)-10(-5) mol/kg) dose-dependently reduced propagation time of the contraction in the distal oesophagus from 1.13 +/- 0.24 sec to 0.27 +/- 0.19 sec, whereas propagation in the proximal and middle parts of the oesophagus was unaffected. NG-nitro-D-arginine (D-NNA; 10(-5) mol/kg) had no influence on propagation time. In animals treated with L-NNA (10(-5) mol/kg) atropine (50 micrograms/kg) had no influence on propagation time in any part of the oesophagus. L-Arginine (10(-4) mol/kg) had no influence on the propagation time in animals treated with L-NNA (10(-5) mol/kg) and atropine (50 micrograms/kg). Neither D-NNA (10(-5) mol/kg) nor L-NNA (10(-7)-10(-5) mol/kg) influenced the amplitude of the contractions at any of the recording sites. In animals given L-NNA (10(-5) mol/kg) atropine (50 micrograms/kg) reduced the amplitude of the contraction significantly only at the distal recording site (1-cm recording site) from 62.0 +/- 4.9 mmHg to 34.5 +/- 5.3 mmHg. L-Arginine (10(-4) mol/kg) had no effect on the amplitude of contractions. CONCLUSION: The L-arginine-NO pathway plays a role in the control of primary peristalsic contractions of the oesophagus.

Amino Acid Oxidoreductases↗
PubMed1993

The increase of yellow skin colour beyond that of serum bilirubin: a proposed indicator of risk for bilirubin encephalopathy in the newborn.

Forty-seven newborn infants with 1 min Apgar score < 7 were studied. On the third postnatal day the following measurements were made: yellow skin colour, serum bilirubin concentration, reserve albumin concentration and plasma pH. Given the bilirubin concentration and the regression curve between the yellow skin colour and the bilirubin concentration, delta-TcB was calculated as the difference between measured yellow skin colour and the expected yellow skin colour. There was a negative correlation between delta-TcB and Apgar score (P = 0.003), pH (P = 0.026) and reserve albumin concentration (P = 0.045). Fourteen of the included newborns had central nervous system symptoms in the days just following birth. A tendency towards higher delta-TcB was noted in this group (P = 0.08). The results suggest that further study of delta-TcB determination as a tool in the assessment of the icteric newborn infant is justified.

Apgar Score↗
PubMed1993

The risk of bilirubin encephalopathy, as estimated by plasma parameters, in neonates strongly suspected of having sepsis.

The study comprises 18 mature newborns, strongly suspected of having sepsis, and a control group of 18 mature, healthy newborns with the same postnatal age. The object of the investigation was to compare the risk of development of bilirubin encephalopathy between the two groups, as estimated by plasma parameters. The sepsis group had significantly lower reserve albumin concentration for binding of MADDS (p < 0.01) and significantly lower total albumin concentration (p < 0.01). No significant differences were observed in unconjugated bilirubin concentration and plasma pH. It is suggested that mature newborns with sepsis have a slightly increased risk of developing bilirubin encephalopathy.

Bacterial Infections↗
PubMed1992

Reduced albumin binding of MADDS--a measure of bilirubin binding--during pregnancy and delivery.

It was the purpose of the present study to investigate whether the decrease in the ability of plasma albumin to bind bilirubin, noted in pregnancy and during delivery, takes place in one step, during pregnancy alone, or in two steps, during both pregnancy and delivery. Furthermore, it was investigated whether a possible decrease during labor was related to the method of delivery itself. The material comprised (a) 17 pregnant women who delivered vaginally; (b) 25 women who were delivered by Cesarean Section; and (c) a group of 25 non-pregnant women. The reserve albumin concentration for binding of MADDS (a measure of the binding of unconjugated bilirubin), the total albumin concentration and the ratio between them were constant in the 6-week period up to birth and were significantly lower than the corresponding values in the non-pregnant group. During labor a significant decrease in reserve albumin and ratio of reserve albumin to total albumin was observed, while no change in the total albumin concentration was noted. No significant difference in reserve albumin concentration, total albumin concentration and ratio between them was found when the group of mothers who delivered vaginally was compared to the Cesarean Section group. It is concluded that the decrease in the ability of plasma albumin to bind unconjugated bilirubin takes place stepwise. The first step is a significant reduction during pregnancy followed by a further decrease during labor. The method of delivery is of no significance.

Bilirubin↗
PubMed1992

The possible risk of bilirubin encephalopathy as predicted by plasma parameters in neonates with previous severe asphyxia.

The study group consisted of nine mature newborn infants with a previous history of severe asphyxia and a control group of 18 mature, healthy newborns with the same postnatal age and sex. The object of the investigation was to compare the possible risk of development of bilirubin encephalopathy between the two groups as estimated by plasma parameters. The asphyxia group had a significantly lower reserve albumin concentrations for binding of monoacetyldiaminodiphenyl sulphone (P = 0.008), a measure of binding of unconjugated bilirubin, and significantly lower total albumin concentrations (P = 0.02). No significant difference was observed in unconjugated bilirubin concentration. It is suggested that mature newborns with previous severe asphyxia are at a slightly increased risk of developing bilirubin encephalopathy over and above the well-known risk associated with increased permeability of the blood brain barrier.

Asphyxia Neonatorum↗
PubMed1992

Sensory irritation effects of methyl ethyl ketone and its receptor activation mechanism.

The burning and painful effect in nose and eyes, termed sensory irritation, of methyl ethyl ketone vapours was investigated in a mouse bioassay. Sensory irritation is mediated via the trigeminal nerves and results in a reflexively induced decrease in respiratory rate in mice. Methyl ethyl ketone was used as a model substance for ketones. At the lower exposure concentrations a partial fading (desensitization) of the response was seen. Little desensitization was seen at higher concentrations. n-Propanol, a model substance for alcohols, desensitized the receptor at all exposure levels. Preexposure to propanol did not influence the response at high methylethyl ketone concentrations. This suggests that the two substances bind to different receptive sites with different properties, if the ketone response is due to a high exposure concentration. A decrease in tidal volume was also mediated from the upper respiratory tract. The tidal volume effect is mediated by nerves different from those mediating the frequency response, as the time-response relationship, the desensitization pattern, the maximum response and the apparent dissociation constants were different for the two types of effect. Neither the location nor the perceived response related to the volume response is known.

1-Propanol↗
PubMed1992

Prediction of later hyperbilirubinaemia by measurement of skin colour on the first postnatal day and from cord blood bilirubin.

The study comprised 138 mature and healthy newborns admitted to the newborn nursery. The performance of cord bilirubin, yellow skin colour on the first postnatal day, and the increase in skin colour during the first postnatal day was evaluated as a test for later hyperbilirubinaemia, defined as a serum bilirubin concentration above 200 mumol/l on the third postnatal day. All three tests performed well as tests for later hyperbilirubinaemia and had closely similar receiver operating characteristic curves. Combination of the three tests by the technique of logistic regression showed an even better test performance, and it was found that each single parameter contributed significantly to the prediction.

Bilirubin↗
PubMed1991

Maternal smoking and the bilirubin concentration in the first three days of life.

The effect of maternal smoking on the plasma bilirubin concentration in the first three postnatal days was investigated in 137 mature newborns. Forty-three percent of the mothers reported on smoking during pregnancy. The median increase in plasma bilirubin concentration during the first 24 h of postnatal life was significantly higher in the group of neonates born to smokers compared to the group of neonates born to non-smokers (P less than 0.02). By contrast, the median increase in plasma bilirubin concentration from the 1st to the 3rd postnatal day was significantly lower among the neonates born to smokers compared to the group with non-smoking mothers (P less than 0.04). The overall frequency of clinical jaundice and the frequency of neonates with plasma bilirubin concentration above 175 microM on the 3rd postnatal day was almost identical in the two groups. It is suggested that maternal smoking may affect the postnatal plasma bilirubin concentration in the offspring by various mechanisms.

Bilirubin↗
PubMed1991

[Phototherapy of newborn infants].

The effect of light treatment on neonates with jaundice was discovered in 1958. Since then, many hundred thousand infants have been treated with light. The presumed mechanism of effect is photo-excitation of bilirubin extravascularly in the skin with the formation of bilirubin isomers which can be excreted in unconjugated form in the bile and photo-oxidation products which can be excreted in the urine. The quantitative relationships have only been partially elucidated. Blue light is the most effective. Green light causes lowering of bilirubin but, on the basis of present knowledge, there is no basis to recommend this as ye. Intermittent phototherapy has limited distribution. If intensive phototherapy is required, double light is effective. No long-term side effects of light treatment have been observed but, during treatment, side effects in the form of diarrhoea, drowsiness and transient exanthemata may occur.

Bilirubin↗
PubMed1990

[Treatment with low-dose vaginal estradiol in post-menopausal women. A double-blind controlled trial].

Twenty-three postmenopausal women with recurrent cystitis were allorted at random to treatment for five months with local oestrogen in the vagina or placebo treatment with the object of assessing the local effect on the vaginal epithelium and on the tendency to recurrent cystitis. The therapeutic group and the placebo group were entirely comparable prior to treatment. In the therapeutic group, the oestrogen index in vaginal scrapings was significantly higher after treatment than in the placebo group (p less than 0.01). The number of positive urine cultures and the patients/satisfaction with treatment wee not significantly different in the two groups.

Administration, Intravaginal↗
PubMed1990

The cephalocaudal progression of jaundice in newborns in relation to the transfer of bilirubin from plasma to skin.

The cephalocaudal progression of jaundice was studied in 136 mature, clinically well newborns. The yellow colour of the skin was measured with the transcutaneous bilirubinometer. Significant positive correlation was found between the yellow colour of the skin in four regions and the plasma bilirubin concentration (forehead: rho = 0.83, abdomen: rho = 0.89, knee: rho = 0.82, and foot: rho = 0.65, all P less than 0.00001). The values obtained from the forehead were significantly higher than the values obtained from the abdomen (P less than 0.0001), the knee (P less than 0.00001), and the foot (P less than 0.00001). The cephalocaudal progression of jaundice correlated positively with the plasma bilirubin concentration (rho = 0.58, P less than 0.00001) and inversely with the gestational age (rho = -0.28, P less than 0.01). The results support a proposed hypothesis explaining the cephalocaudal progression of jaundice in newborns. According to the hypothesis, the cephalocaudal colour difference may be caused by the presence of young bilirubin-albumin complexes in the blood undergoing conformational changes.

Bilirubin↗
PubMed1990

Measurement of the yellow colour of the skin as a test of hyperbilirubinemia in mature newborns.

The relation between the yellow colour of the skin as measured by the Minolta Air Shields jaundice meter and the serum bilirubin concentration was investigated in 207 mature icteric, but otherwise healthy, newborns and the relationship between the changes in the meter readings and the changes in serum bilirubin concentration was studied in 99 of the infants. Good correlation was found both between the meter readings and the serum bilirubin concentration (p = 0.81), and between the changes in meter readings and the changes in serum bilirubin concentration (p = 0.69). The jaundice meter proved to be effective in predicting hyperbilirubinemia defined as serum bilirubin values 175 or 225 mumol/l, and was also effective in predicting increasing or decreasing serum bilirubin concentrations by sequential meter readings. The gestational age correlated slightly but significantly with the meter readings (p = -0.15) and with the serum bilirubin concentration (p = -0.15). However, these findings did not affect the action levels for use of the jaundice meter as a screening device for hyperbilirubinemia. The postnatal age and the birthweight did not significantly influence the meter readings.

Age Factors↗