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Biomedical subjects

N McIntosh

Publications and source records attributed to N McIntosh.

At least 73 records · Page 4Linked to original sources
PubMed1995

Transcutaneous oxygen levels in retinopathy of prematurity.

Retinopathy of prematurity (ROP) is a potentially blinding disease of preterm infants. 21 days of computer-recorded transcutaneous oxygen (TcPO2) data were compared in 31 infants with stage 3 or greater ROP and 38 infants with no ROP or stage 1 or 2. In a multiple logistic regression adjusted for significant perinatal factors (birthweight, gestation, and intraventricular haemorrhage), babies with stage 3 or higher ROP showed an increased variability of TcPO2 in week 1 (p < 0.01) and 2 (p = 0.012) but not week 3. Variability of TcPO2 in the first 2 weeks of life is a significant predictor of severe ROP.

Blood Gas Monitoring, Transcutaneous↗
PubMed1995

Outcome at three years of sick neonates involved in a double-blind trial of two parenteral amino acid preparations.

The authors investigated the hypothesis that neonates who received a parenteral amino acid preparation causing high plasma amino acid levels in the first week of life would perform less well at follow-up than those who received a preparation in which the plasma aminogram fell persistently within the normal range. 27 surviving children who had received either preparation as neonates underwent psychometric assessment at three years. Parents completed three questionnaires about temperament, behaviour screening and socio-economic status. Four of 10 patients who had received one preparation and two of 17 infants who had received the other were of below-average intelligence. This may be related to the different amino acids in the mixtures and the hyperamino-acidaemia caused by this.

Amino Acids↗
PubMed1994

The practical management of artifact in computerised physiological data.

Computerised physiological data contains artifact that needs to be identified and possibly removed. Whilst computers may eventually satisfactorily perform this function, at present only manual removal is possible for the majority of intensive care computer groups. We assessed the effects of artifact and its removal on the physiological data of 3 patients. Artifact was manually removed from 7 days of data in 4 parameters (heart rate, respiratory rate, systolic blood pressure [sbp] and transcutaneous oxygen [tcpO2]) by 3 independent observers. Six hour time periods were analysed. Median and mean values before and after the manual removal of artifact were compared. Overall 6.5% of data was removed as artifact. This was greatest for tcpO2 (9.9%) and sbp (10.6%), with smaller amounts for respiratory rate (2.8%) and heart rate (2.4%). Sbp showed a marked difference in the amount of data removed between patients, whereas tcpO2 data contained quite large volumes of artifact, but this was fairly consistent between patients. Removal of artifact affected mean values more than median values. One observer considered that both physiological and non-physiological artifact should be removed, whereas the other two observers removed only non-physiological artifact. Agreement in results between the latter was good. Our results suggest that inter-observer variability should have a minimal effect on values, once rules identifying the type of artifact to be removed are agreed. Removal of artifact did not have a clinically significant effect on results, but may be an important consideration in the statistical analysis of computerised physiological data.

Artifacts↗
PubMed1994

Prolonged premature rupture of membranes in the preterm infant: a 7 year study.

AIM: To review the outcome of infants born following prolonged and preterm rupture of the membranes. DESIGN: retrospective and partially prospective observational study. SETTING: babies born in and referred to a tertiary neonatal centre. PATIENTS: 117 preterm infants, median gestation (range) = 29.5 (25-36) weeks, seen over a 7 year period with membranes ruptured for more than 4 days; median (range) = 9 (4-119) days. OUTCOME MEASURES: survival and cause of death, compression deformities, pulmonary hypoplasia and infection. RESULTS: 23 infants died, 11 from pulmonary hypoplasia and 11 as a direct consequence of prematurity (3 from hyaline membrane disease, 7 from bronchopulmonary dysplasia and one from necrotising enterocolitis developed on day 17). One infant had a lethal congenital abnormality and died untreated of overwhelming infection. No other infants died of infection. 94% of infants were treated with broad-spectrum antibiotics after birth. Compression deformities were seen in 25 infants: median duration of membrane rupture 28 days, range 4-119. In those without deformity, median duration was 7 days, range 4-105. Sixteen infants had pulmonary hypoplasia (median 31, range 14-119), 11 died (median 37, range 21-112) and five survived (median 23, range 14-119). Although the median duration of membrane rupture in infants dying of pulmonary hypoplasia was longer than in those who did not have hypoplasia (31 compared to 7 days), 13 of 27 (48%) of infants whose membranes were ruptured for 4 weeks and 4 of 7 (57%) whose membranes were ruptured more than 70 days survived. CONCLUSION: death from pulmonary hypoplasia is a much more serious problem following preterm prolonged membrane rupture than is infection. Pulmonary hypoplasia is not inevitable even after prolonged periods of membrane rupture.

Bacterial Infections↗
PubMed1994

Changes in mean blood pressure caused by damping of the arterial pressure waveform.

'Damping' of an intra-arterial pressure waveform theoretically affects systolic and diastolic blood pressure whilst mean blood pressure (mbp) continues to be reliable. We assessed changes in mbp associated with 79 episodes of damping in 30 infants. The average mbp in the hour just before damping occurred was compared with that in the first hour of damping. The mean change in mbp was -0.845 mmHg. In 50% of cases this change was < 2 mmHg and in 24% of episodes > or = 4.1 mmHg. Damping may produce clinically significant changes in mbp which computer trend data may help to differentiate.

Blood Pressure↗
PubMed1994

Hydrops foetalis and chylothorax associated with superior caval vein obstruction and resolution following balloon dilatation.

A female infant (33 weeks' gestation) was delivered by emergency caesarean section because of hydrops foetalis. No cause was identified initially; haemoglobin, liver and renal functions were normal and there was no evidence of sepsis or significant myocardial dysfunction or arrhythmia. There was initial improvement with conventional management but bilateral pleural effusions persisted, which became overtly chylous after institution of enteral formula feeds on day 4. At 5 weeks of age, an obstruction at the superior caval vein/right atrial junction was confirmed at angiography and dilated with resolution of all remaining oedema and fluid collections. Repeat venography at 9 months of age showed a normal superior caval vein and she remains well at 15 months.

Catheterization↗
PubMed1994

Alleviation of the pain of heel prick in preterm infants.

The hypothesis that the variability of physiological parameters may indicate pain or stress in the neonate was examined. Four parameters (heart rate, respiratory rate, transcutaneous oxygen tension, and carbon dioxide tension) were examined over a 2 minute epoch in response to a heel prick in an attempt to measure stress/pain in 35 preterm newborn infants (26-34 weeks' gestation) half of whom were receiving intensive care. The change in absolute values of these parameters did not discriminate a dummy procedure without prick from the actual procedure containing the prick (paired t test), but the variability of the parameters during an epoch showed significant discrimination. Three procedures were evaluated to reduce this distress using unpaired t test. The use of local anaesthetic cream was not successful. The components of the mixture cause vasoconstriction that would reduce blood flow to the heel and lead to more squeezing which is likely to be painful in the presence of tissue damage. A nurse comforting the infant with tactile and vocal stimulation was slightly helpful but the use of a spring loaded lance was most successful in reducing the distress. The use of spring loaded lances may be more humane for heel pricks.

Anesthetics, Local↗
PubMed1994

A portable dual energy x-ray absorptiometry technique for the measurement of bone mineral in preterm infants.

A dual energy x-ray absorptiometry technique has been developed for the measurement of bone mineral in preterm infants. Two films are taken of the infant's forearm using a standard mobile x-ray set on the ward at two x-ray energies. Included in the field of view is a double step wedge made of aluminum and Perspex. The images are digitized by viewing them on a light box with a TV camera. The bone mineral content in the forearm can then be mapped by the measurement of light intensity in matching pixels of the two films and comparison with the intensities in the step wedge. The bone mineral concentration in the radius, expressed as bone mineral per unit length (mg/mm), is calculated. The technique has been tested using phantoms of calcium hydroxylapatite set in a tissue equivalent material and in Perspex. It has been shown that the reproducibility of the technique is approximately 7% and that there is a systematic underestimate of bone mineral of about 17%. The technique has been shown to be linear up to a bone mineral concentration of 8 mg.mm-1. Longitudinal studies for 14 infants that show an initial 6-wk period of demineralization after birth with a subsequent mineralization phase are reported.

Absorptiometry, Photon↗
PubMed1993

Pitfalls in the use of ELISA to screen for monoclonal antibodies raised against small peptides.

Small peptides are often conjugated to large carrier proteins such as thyroglobulin to increase their immunogenicity. Antibodies are raised against peptide, thyroglobulin and contaminants, such as immunoglobulins or BSA in the thyroglobulin preparation, but anti-contaminant antibodies will not be revealed if immune serum is diluted in buffer containing immunoglobulin-contaminated BSA. This may lead to the development of an inappropriate hybridoma-screening assay which detects more anti-contaminant than anti-peptide antibodies if ELISA plates are coated with a capture antibody or blocked with BSA. Dilution of culture supernatants in buffer containing BSA and Tween 20 minimises the risk of false positive results and makes plate-blocking unnecessary. The high affinity peptide-specific antibodies in immune serum, which are more readily detected than lower affinity monoclonal antibodies, may result in an inadequately sensitive hybridoma-screening ELISA.

Animals↗
PubMed1993

Transcervical CVS sample size: correlation with placental location, cytogenetic findings, and pregnancy outcome.

Data from 2907 transcervical CVS cases performed on singleton pregnancies were reviewed retrospectively and villus sample size was correlated with cytogenetic results, placental location, maternal age at the expected date of confinement (EDC), gestational age at the time of sampling, birth weight, gestational age at the time of delivery, and pregnancy outcome. No correlation was noted between villus sample size and maternal age, gestational age at sampling, gestational age at delivery, birth weight, or pregnancy outcome. An inverse correlation between villus sample size and percentage of abnormal cytogenetic findings was statistically significant (chi 2 = 8.53, p < 0.01). The percentage of small samples was greater when the placenta was anterior, lateral, or fundal than when the placenta was posterior.

Adult↗
PubMed1993

Cyclical variation of blood pressure and heart rate in neonates.

Using a computerised physiological monitoring system a cyclical variation in blood pressure (waves), with associated changes in heart rate and transcutaneous oxygen, was observed. Twenty five episodes were seen in 10 neonates, with a median gestation of 33 weeks (range 28-42 weeks). Eight neonates had an asphyxial injury. Blood pressure waves had a mean (SD) amplitude of 11.6 (5.6) mm Hg with a mean wavelength of 9.0 (5.2) minutes. Both amplitude and frequency were independent of gestation. In neonates of less than 34 weeks an inverse phase relation existed between heart rate and blood pressure waves (blood pressure rose as heart rate fell); in infants with a gestation greater than 34 weeks a direct phase relationship occurred (blood pressure and heart rate rose together). It is postulated that hypertensive blood pressure waves may cause or exacerbate cerebral pathology in neonates with a pressure passive cerebral circulation.

Blood Gas Monitoring, Transcutaneous↗