Biomedical subjects

B P Lundell

Publications and source records attributed to B P Lundell.

18 recordsLinked to original sources

PubMed1994

Effect of inhaled nitric oxide on raised pulmonary vascular resistance in children with congenital heart disease.

OBJECTIVE: To study the short-term effects of inhaled nitric oxide in infants and young children with congenital heart disease. SETTING: A supraregional referral centre for children with congenital heart disease. PATIENTS AND METHODS: 22 infants and children aged 3-32 months (median age 5 months) with congenital heart disease undergoing preoperative cardiac catheterisation. All but one infant had intracardiac shunt lesions and 13 had increased pulmonary vascular resistance. During catheterisation the patients inhaled nitric oxide in a concentration of 40 parts per million in room air. Pulmonary and systemic haemodynamic variables were evaluated by means of measured oxygen consumption and the Fick principle before and after 10 minutes' exposure to nitric oxide. RESULTS: Inhaled nitric oxide did not affect the systemic circulation. There was a significant reduction in the pulmonary vascular resistance, but only in the 13 infants with pulmonary hypertension, in whom pulmonary vascular resistance was reduced by 34% from 8.6 (4.6) mm Hg.min.m2.l-1 (mean (SD)) to 5.7 (3.5) mm Hg.min.m2.l-1. The pulmonary circulation in infants with normal pulmonary vascular resistance was not affected. No statistically significant increase in methaemoglobin was seen, though there were large individual differences. No other side effects were seen. CONCLUSION: The present study shows that in infants with congenital heart disease inhaled nitric oxide reduced pathologically increased pulmonary vascular resistance without affecting systemic circulation and without important side effects with brief exposure.

Administration, Inhalation↗

PubMed1990

Left ventricular stroke volume and output in healthy term infants.

Left ventricular output, left ventricular stroke volume, and systemic vascular resistance were measured noninvasively in 16 healthy term infants at 6 predefined time intervals from less than 15 minutes to 72 hours after birth. The blood flow velocity in the ascending aorta was measured by range-gated Doppler technique and multiplied by the cross-sectional area, measured by 2-dimensional and M-mode echocardiography to yield left ventricular output. Stroke volume was calculated by dividing left ventricular output by heart rate. Mean arterial blood pressure was measured by oscillometric technique and used for calculation of systemic vascular resistance. A poor association between heart rate and left ventricular output was found, whereas there was a very close relationship between stroke volume and left ventricular output. There was also a reciprocal relationship between systemic vascular resistance and stroke volume. This suggests that stroke volume and not heart rate is the main determinant of neonatal left ventricular output and that the low postnatal afterload might strengthen this relationship.

Cardiac Output↗

PubMed1990

Postnatal changes in intracranial blood flow velocity in preterm infants.

Postnatal changes in intracranial arterial blood flow velocity, were studied in preterm infants of less than 34 weeks of gestation. The blood flow velocity was measured in an artery on the base of the skull, using a range-gated Doppler ultrasound velocimeter. Ten healthy infants (mean gestational age 32.5 weeks), and ten infants with transitional respiratory disease (mean gestational age 31.3 weeks) were studied at 1, 2, 5, 24 h, and 2, 3, 5 and 10 days after birth. The healthy infants showed a consistent pattern of changes on the first day, with an average reduction in mean flow velocity of 29% between 1 and 5 h. At 24 h after birth, mean flow velocity had almost returned to the level of the 1 h recording. After 24 h there was a gradual increase in systolic and mean flow velocity until 10 days, while diastolic flow velocity remained unchanged. In the infants with respiratory disease there were no systematic changes in mean flow velocity on the first day, although large individual changes were seen. After 24 h no differences were seen between the healthy infants and the infants with respiratory disease. These findings indicate a transient decrease in cerebral perfusion during early circulatory transition in healthy preterm infants, and that mild to moderate respiratory disease causes larger individual variations in intracranial blood flow velocity.

Blood Flow Velocity↗

PubMed1989

Left ventricular output during postnatal circulatory adaptation in healthy infants born at full term.

Left ventricular output was measured non-invasively at predefined time intervals from less than 15 minutes to 72 hours after birth in 16 infants who had been born at full term. The blood flow velocity in the ascending aorta was measured by a range gated Doppler technique and multiplied by the cross sectional diameter measured by cross sectional and M mode echocardiography. Left ventricular output remained high in the first two hours, 235-243 ml/min/kg, despite a 10% decrease in heart rate. The fall in heart rate was compensated for by a 15% increase in stroke volume. Between 2 and 24 hours there was a significant fall in mean (SD) left ventricular output to 187 (35) ml/min/kg caused mainly by a reduction in stroke volume. The fall in left ventricle output after two hours may reflect an adaptation to the decreased demand on the left ventricle as the ductus constricts.

Adaptation, Physiological↗

PubMed1989

Cerebral blood flow following indomethacin administration.

Cerebral hemodynamics were studied in 7 term newborn lambs and 10 preterm infants with patent ductus arteriosus. Intracranial blood flow velocities were measured using a pulsed-wave Doppler velocimeter applied through the fontanel. Intravenous injection of indomethacin (0.2 mg.kg-1) reduced intracranial blood flow velocities in both lambs and infants. The CO2 reactivity, however, did not change in the lambs. Indomethacin administration is associated with reduced cerebral blood flow velocities but the pharmacological mechanism is unclear.

Animals↗

PubMed1987

Early postnatal changes in intracranial arterial blood flow velocities in term infants.

A range-gated Doppler technique was used to assess intracranial arterial blood flow velocity changes in 20 healthy term infants during the first 3 days after birth. Systolic, diastolic, and mean flow velocity decreased during the first 30 min after birth whereas arterial pressure and heart rate did not change. Mean flow velocity did not change from 30 min to 72 h of life, although systolic and diastolic flow velocity changed in opposite directions. Systolic flow velocity increased to 2 h of age and thereafter decreased. Diastolic flow velocity decreased to a minimum value at 2 h and thereafter increased to 24 h of age. These flow velocity changes suggest an initial decrease in cerebral perfusion, followed by a constant cerebral blood flow during normal circulatory transition after birth.

Blood Flow Velocity↗

PubMed1986

Changes in intracranial arterial blood flow velocities during surgical ligation of the patent ductus arteriosus.

A combined continuous and range-gated Doppler instrument was used to assess intracranial arterial blood flow velocity changes in infants and neonates undergoing surgical ligation of the Ductus Arteriosus (DA). Continuous recordings during DA closure in six infants (3.5-10 months old), showed an abrupt increase in diastolic blood flow velocity simultaneous with an increase in systolic and diastolic arterial blood pressure. In five infants, these changes were followed by a rapid fall in systolic and diastolic blood pressure without a concomitant change in blood flow velocity, which may be secondary to a rapid fall in intracranial vascular resistance. The mean blood flow velocity increase following DA closure was 27% (8-43%) and the changes in diastolic and mean blood flow velocity were significant (p less than 0.01). In seven preterm neonates (24-28 weeks) studied before and after surgery, a mean blood flow velocity increase of 50% (14-115%) (p less than 0.01), mainly due to an increase in diastolic blood flow velocity (p less than 0.01), was recorded. These rapid intracranial hemodynamic changes during surgical DA closure should be taken into consideration when selecting techniques for DA closure.

Blood Flow Velocity↗

PubMed1986

Intracranial Doppler flow velocimetry compared with extracranial carotid blood flow measurements.

The effects of changes in carotid blood flow on intracranial blood flow velocities were examined in six newborn lambs under general anesthesia. Carotid blood flow was measured using electromagnetic flow cuffs. A combined continuous and pulsed Doppler instrument was used to measure intracranial blood flow velocities on the base of the skull through artificially created fontanels. Baseline carotid blood flow was 96 +/- 18 ml X min-1 (mean +/- SD) and increased by 58 +/- 13% following contralateral occlusion. A close correlation between changes in carotid blood flow and intracranial blood flow velocity was found (y = -6.28 + 3.72x, Sy = 182.3, Sy/x = 0.30, r = 0.89, p less than 0.001). The closest estimate of changes in blood flow to the brain was the temporal mean of the cross-sectional average velocity.

Animals↗

PubMed1986

Ductus closure in preterm infants. Effects on cerebral hemodynamics.

Intracranial arterial blood flow velocities were studied before and after ductus closure by surgery (n = 8) and indomethacin (n = 10) in very low birth weight infants. Blood flow velocities were measured non-invasively through the fontanel with a pulsed Doppler velocimeter. Ligation of the ductus was associated with a 62% increase in mean flow velocity 24 hours after surgery, mainly secondary to increased diastolic flow velocity. Indomethacin (0.2 mg/kg i.v.) induction of ductus constriction was associated with a 36% decrease of mean flow velocity one hour after administration. At 24 hours, the intracranial blood flow velocity had returned to the pretreatment level but was still significantly lower than after ligation. Ductus closure is associated with marked changes in cerebral hemodynamics. Ligation causes increased arterial blood flow velocities and indomethacin administration seems to reduce blood flow velocities to the brain.

Blood Flow Velocity↗

PubMed1984

Neonatal left ventricular performance after vaginal delivery and cesarean section under general or epidural anesthesia.

Left ventricular systolic time intervals, plasma norepinephrine concentration, hematocrit, and blood pressure were recorded in infants delivered vaginally and by cesarean section from mothers under epidural or general anesthesia. Each group comprised 12 infants. Left ventricular ejection time and the preejection period were longer in infants delivered vaginally, although the concentrations of norepinephrine found were greater than those found in the cesarean section groups. Hematocrit and blood pressure were unrelated to the mode of delivery or the anesthetic technique. The isovolumic contraction time, however, was significantly shorter after epidural anesthesia 15.6 +/- 7.6 msec (mean +/- 1 SD) than after general anesthesia 20.5 +/- 8.0 msec at 30 minutes (p less than 0.05), 14.8 +/- 6.2 msec, and 20.9 +/- 5.7 msec at 2 hours respectively (p less than 0.001). These differences in left ventricular dynamics are probably related to the effects of anesthetics that have traversed the placenta rather than to mode of delivery.

Anesthesia, Epidural↗

PubMed1984

Neonatal cerebral blood flow velocity I. An in vitro validation of the pulsed Doppler technique.

A combined pulsed and continuous Doppler instrument was used to assess flow velocities in an in vitro model designed to simulate small deeply lying arterial vessels. Diameters of the model vessels, depth under the transducers and the pulsatile flow patterns were chosen to simulate the corresponding conditions that can be expected when cerebral blood flow velocities are measured with this technique through the anterior fontanel in newborn infants. Computer analysis of the space average velocity signal from the pulsed Doppler mode, showed that the area under this curve, which corresponds to distance, was closely correlated to true flow over a wide range of flows in vessels of different diameters. This variable is suggested to be the closest estimate of true flow, when the diameter of the vessel under study cannot be accurately measured.

Blood Flow Velocity↗

PubMed1983

Left ventricular systolic time intervals in preterm infants with patent ductus arteriosus.

Left ventricular systolic time intervals were recorded by a non-invasive technique, from the axillary artery, in 13 preterm infants with patent ductus arteriosus. At the onset of clinical symptoms, consistent with a large left-to right ductal shunt, the preejection intervals were shorter than in a control group of nine preterm infants without a patent ductus. The most pronounced difference was found in the shortening of the isovolumic contraction time, 10.7 msec in the ductus group compared with 22.4 msec in the control group. Ductal closure normalized the isovolumic contraction time to 22.1 msec. The very short preejection intervals, associated with a large ductal shunt, are suggested to reflect a combination of reduced aortic diastolic pressure and increased left ventricular filling pressure. In spite of increased volume load to the left ventricle there were no detectable changes in the systolic time intervals indicating impaired left ventricular function. The left ventricle seems to be competent to handle increased volume load in the presence of reduced afterload in preterm infants with symptomatic left-to right ductal shunts.

Blood Pressure↗

PubMed1983

Digoxin therapy and left ventricular performance in premature infants with patent ductus arteriosus.

Left ventricular systolic time intervals were assessed in 16 preterm infants with symptomatic left-to-right ductal shunts, before, during and after digoxin therapy. An intravenous loading dose of digoxin, 20 micrograms/kg, resulted in a serum digoxin concentration of 1.94 +/- 0.44 nmol/l (mean +/- 1 SD) but in no significant change in heart rate or systolic time intervals. Digoxin maintenance, 2.5 micrograms/kg/12 h, led 3-7 days later to serum concentrations of 2.57 +/- 1.06 nmol/l with an associated shortening of left ventricular ejection time (p less than 0.05) which probably reflected a reduced ductal shunt. Digoxin therapy was withdrawn after ductal closure. The terminal serum half-life was 87 +/- 17 h. Decreasing digoxin concentrations were associated with prolongation of left ventricular ejection time (p less than 0.01). Digoxin therapy did not seem to influence left ventricular systolic time intervals while ductal patency persisted. This may be attributed to limitations of the method or the left ventricle already working at its maximum.

Digoxin↗

PubMed1983

Pulse wave patterns in patent ductus arteriosus.

Pulse wave patterns were analysed in 10 term and 10 preterm infants with patent ductus arteriosus (PDA) and in 2 matched control groups. A non-invasive technique was used to record the pulse waves from the axillary artery. The pulsatile ratio was calculated as the quotient between the amplitude of the incisural notch and the peak of the pulse wave above the end diastolic baseline. The pulsatile ratio was considerably lower in preterm and term infants with PDA compared with the ratio after closure of the ductus and the ratio in control infants. A pulsatile ratio less than 0.50 indicates the presence of a large PDA whereas a ratio over 0.55 is normal. The technique may be used to document and evaluate arterial pulse wave patterns and may be a useful diagnostic tool.

Axillary Artery↗

PubMed1983

Left ventricular systolic time intervals and plasma noradrenaline concentrations during acute hypovolaemia in newborn infants.

Left ventricular systolic time intervals and plasma noradrenaline concentrations were determined in twelve newborn infants during acute moderate hypovolaemia. Rapid withdrawal of 8.5 ml of blood per kg body weight shortened the left ventricular ejection time from 204 to 176 msec (P less than 0.001) and increased the plasma noradrenaline concentration from 3.4 to 4.0 nmol/l (P less than 0.05). Systemic blood pressure was unchanged. It is concluded that even a moderate reduction in blood volume is associated with marked changes in left ventricular dynamics. The shortening of left ventricular ejection time during hypovolaemia probably reflects left ventricular adaptation to decreased volumes and response to increased noradrenaline release.

Blood Transfusion↗

PubMed1982

Tonsillar hyperplasia in children. A cause of obstructive sleep apneas, CO2 retention, and retarded growth.

Tonsillar hyperplasia causing obstructive sleep apneas in children is a well-defined clinical entity with nocturnal CO2 retention, retarded growth, and impaired physical and psychological status. Pulmonary hypertension, cor pulmonale, and ultimately, death may develop in a small number of these children. This syndrome may also develop in children with only moderately enlarged tonsils in association with neuromuscular hypothonia or anatomical defects. Anamnesis will readily detect the children at risk. The syndrome is cured completely by tonsillectomy. The CO2 retention disappears and length and weight growths are accelerated after surgery.

Carbon Dioxide↗

PubMed1982

Assessment of left ventricular adaptation to extrauterine circulation.

Left ventricular systolic time intervals (STI) were recorded by non-invasive technique from the axillary artery in fifteen normal newborns from 10-15 min to 70-74 hours after birth. The observed changes in the different STI could almost entirely be related to changes in the isovolumic contraction time (ICT). At the early postnatal recording ICT was only 21.0 msec suggesting an enhanced left ventricular performance compared to prenatal observations. During the following hours ICT increased to 31.6 msec which in some infants may imply a reduced left ventricular performance. This is suggested to coincide with ductal closure.

Adaptation, Physiological↗

PubMedDate not supplied

Oxygen consumption in infants and children during heart catheterization.

Oxygen consumption was measured in infants, children, and adolescents during diagnostic heart catheterizations. A total of 825 measurements of oxygen consumption (VO2) was performed in 504 subjects using a semiopen hood system and a paramagnetic oxygen analyzer. In 256 subjects under 3 years of age, body dimensions and heart rate were found to be significant factors for oxygen consumption. The regression equation for both sexes was: VO2/BSA (ml/min.m2) = 3.42.height (cm) - 7.83.weight (kg) + 0.38.HR - 54.1 (r2 = 0.39, SD = 38.7), where BSA is body surface area and HR is heart rate. VO2/BSA was significantly lower in infants less than 3 months of age (133 +/- 33 ml/min.m2) compared with infants of 3-12 months (171 +/- 37 ml/ min.m2; p < 0.01). In 272 children aged 3 years and older and adolescents, gender was a significant factor in oxygen consumption together with BSA and HR. The regression line equation for males was VO2/BSA (ml/ min.m2) = 0.79.HR - 7.4.BSA(m2) + 108.1 (r2 = 0.45, SD = 34.2). The regression line equation for females is VO2/BSA (ml/min.m2) = 0.77.HR - 5.2.BSA(m2) + 106.8 (r2 = 0.43, SD = 34.4). Hematocrit, systemic oxygen saturation, and blood pressure were not significant factors. The predictive value of nomograms for oxygen consumption is limited because of the large interindividual variations not explained by differences in gender, body size, or simple hemodynamic variables. Preferably, oxygen consumption is measured; but if nomograms for oxygen consumption are used for hemodynamic assessment, the wide confidence intervals should be considered.

Adolescent↗