Echocardiographic assessment of blood flow volume in the superior vena cava and descending aorta in the newborn infant

BACKGROUND

Clinical methods of assessing adequacy of the circulation are poor predictors of volume of blood flow in the newborn preterm. Doppler echocardiography can be used to assess perfusion at various sites in the circulation.

OBJECTIVE

To assess repeatability of measurement of volume of superior vena caval (SVC) and descending aortic (DAo) flow.

DESIGN

SVC and DAo flow volume were assessed four times in the first 48 h of postnatal life in a cohort of preterm (<31 weeks) infants. Within-observer and between-observer repeatability was assessed in a subgroup of preterm infants. Normative values were derived from 14 preterm infants who required <48 h respiratory support and 13 healthy term infants.

RESULTS

Within-observer repeatability coefficient was 30 ml/kg/min for quantification of SVC flow, and 2.2 cm for DAo stroke distance. Measurement of DAo diameter had poor repeatability. Between-observer repeatability appeared poorer than within-observer repeatability. The fifth centile for volume of SVC flow in healthy preterm infants was 55 ml/kg/min and 4.5 cm for DAo stroke distance.

CONCLUSIONS

Echocardiographic assessments of volume of SVC flow and velocity of DAo flow have similar within-observer repeatability to other neonatal haemodynamic measurements. Between-observer repeatability for both measurements was poor, reflecting the difficulty of standardising these novel techniques. In this small cohort of preterm infants, SVC flow volume <55 ml/kg/min and DAo stroke distance <4.5 cm represented low or borderline systemic perfusion in the first 48 h of postnatal life.

Relationship between blood pressure and blood flow in newborn preterm infants

BACKGROUND

Arterial blood pressure remains the most frequently monitored indicator of neonatal circulatory status. However, studies of systemic perfusion in neonates have often shown only weakly positive associations with blood pressure.

OBJECTIVES

To examine the relationship between invasively monitored arterial blood pressure and four measurements of systemic perfusion: left and right ventricular outputs, superior vena caval (SVC) flow and descending aortic (DAo) flow.

DESIGN

Echocardiographic assessments of perfusion were performed four times in the first 48 h of postnatal life in a cohort of 34 preterm (<30 weeks) infants. Arterial blood pressure was monitored invasively over the exact duration of the echocardiogram.

RESULTS

In the first 48 h of postnatal life there was no evidence of a positive association between blood pressure and volume of blood flow in any of the four vessels studied. At 5 h postnatal age there was a weak but significant inverse correlation between volume of SVC flow and arterial blood pressure (p = 0.04). A similar but non-significant trend was seen at 12 h postnatal age.

CONCLUSIONS

Infants with reduced systemic perfusion tend to have normal or high blood pressure in the first hours of life, suggesting that a high systemic vascular resistance may lead to reduced blood flow. Low blood pressure does not correlate with poor perfusion in the first 48 h of postnatal life in sick preterm infants.

Cardiorespiratory stability during echocardiography in preterm infants

Blood pressure, heart rate, and oxygen saturation were monitored prospectively during 40 echocardiography recordings on 17 preterm infants (25-29 weeks; 510-1430 g), to examine whether echocardiography can be performed without disturbing cardiorespiratory status in preterm infants. There was no impact on absolute blood pressure. Heart rate increased by a mean of 4 beats per minute, and oxygen saturation decreased by a mean of 1% during echocardiography. While these changes reached statistical significance they are not of clinical significance as they remained well within ranges seen during control rest periods. All readings had greater minute-to-minute variability during echocardiography but differences were small and again remained within physiological ranges.

Primary pulmonary hypoplasia: a case report and review of the literature

A case of primary pulmonary hypoplasia in a term female neonate presenting with severe respiratory distress at birth is reported. Respiratory failure persisted and she died at 12 days of age. Primary pulmonary hypoplasia is a rare condition not associated with other maternal or fetal disorders.

Follow up of a randomised trial of two different courses of dexamethasone for preterm babies at risk of chronic lung disease

OBJECTIVES

To report 18 month outcome of a randomised trial of two courses of dexamethasone to prevent chronic lung disease of prematurity.

STUDY DESIGN

Babies of birth weight 1250 g or less ventilated at 7 days of age were randomised to a 42 day reducing course (long) or a 3 day pulsed (pulse) course of dexamethasone. Growth, cardiovascular status, and respiratory and neurodevelopmental outcomes were assessed at 18 months.

RESULTS

Seventy six babies were enrolled. Nine died and three were lost to follow up. Babies receiving the long course were weaned off oxygen more quickly than those receiving the pulse course (47% v 69% on oxygen at 28 days; p = 0.01), but there were no differences in 18 month outcomes. However, children averaged -1 SD for growth parameters, half had moderate or severe disability, and 35% and 19% respectively required oxygen at 36 weeks and discharge.

CONCLUSIONS

The dexamethasone course used did not influence long term outcome. However, entry criteria for this study selected a group of babies at high risk of poor long term outcome.

Chest physiotherapy and porencephalic brain lesions in very preterm infants

OBJECTIVE

National Women's Hospital is one of two hospitals to report a destructive brain lesion, namely encephaloclastic porencephaly (ECPE), in extremely preterm infants. It has been associated with non-cephalic presentation, early hypotension and the number of chest physiotherapy treatments in the first month. The aim of the present study was to determine the temporal relationship between ECPE and chest physiotherapy use in very low-birth weight (VLBW) infants in our unit.

METHODOLOGY

Cerebral ultrasound scan reports, post-mortem reports, clinical and physiotherapy records and, if indicated, original ultrasound films were reviewed for all VLBW babies admitted between 1985 and 1998.

RESULTS

Over the 14 year period in question, 2219 babies with a birth weight < or = 1500 g were admitted. Encephaloclastic porencephaly was found in only the 13 previously reported babies born between 1992 and 1994. Encephaloclastic porencephaly was excluded in 1564 (70%) babies. In 621 (28%) babies who did not have late ultrasound scans, ECPE was thought to be unlikely either because the babies never had any chest physiotherapy (n=479) or because they had chest physiotherapy but were known to be neurodevelopmentally normal on follow up (n=142). Data were incomplete for 21 babies (0.9%). The number of chest physiotherapy treatments per baby decreased from a median of 95 prior to 1989 to 38 and the age of starting treatment increased from 5 to 8 days after 1990. The use of chest physiotherapy ceased in 1995.

CONCLUSIONS

Encephaloclastic porencephaly emerged as a problem at a time when the use of chest physiotherapy had decreased. The cluster of cases seen between 1992 and 1994, although associated with the number of chest physiotherapy treatments given, began to appear because of some other factor.

The treatment of patent ductus arteriosus in preterm infants. A review and overview of randomized trials

Patent ductus arteriosus (PDA) is a common problem in very preterm infants. It results in a significant left-to-right shunt and an increase in left ventricular output. Pulmonary compliance can be reduced. Systemic effects result from the diastolic steal and retrograde diastolic blood flow. Randomized controlled trials of PDA closure fall into three groups: (i) prophylactic treatment in the first 24 h, (ii) pre-symptomatic treatment on ultrasound evidence of a PDA or the first clinical signs and (iii) treatment when it becomes haemodynamically significant. Prophylactic treatment with indomethacin reduces the incidence of intraventricular haemorrhage. All the trials have a decreased need to treat a subsequent PDA in the treatment group. There are no other improvements in outcome, without any change in mortality, bronchopulmonary dysplasia, necrotizing enterocolitis or retinopathy of prematurity. Clinical decisions on the treatment of the ductus should be individualized and based on the gestation of the baby, the respiratory condition and the size of the ductal shunt.

Growth restriction in dexamethasone-treated preterm infants may be mediated by reduced IGF-I and IGFBP-3 plasma concentrations

OBJECTIVE

Preterm infants receiving dexamethasone for respiratory morbidity frequently suffer restricted growth. The aim of this study was to investigate the interactions between dexamethasone treatment regimen and circulating IGFBP-3 and IGF-I levels, and the associations between these variables and linear growth rate in preterm babies receiving dexamethasone for chronic lung disease of prematurity.

DESIGN

A randomised, unblinded, clinical trial of two different courses of dexamethasone: a 42-day tapering course (the long course) and a repeatable 3 day pulse course.

PATIENTS

Forty preterm infants (19 in the pulse group, 21 in the long group) with a birthweight < or = 1250 g who were ventilated at 7 days of age.

MEASUREMENTS

Lower leg length was measured thrice weekly by knemometry, and IGFBP-3 and IGF-I levels were measured prior to commencing treatment, at 14 and 42 days of treatment and at 36 weeks postmenstrual age (PMA). Interactions between variables were analysed by stepwise regression analysis and analysis of covariance (ANCOVA). Associations between variables were assessed by correlation coefficients.

RESULTS

In an ANCOVA, mean daily dose of dexamethasone/kg (MDDD) and treatment group both significantly influenced IGFBP-3 levels (P = 0.0009 and P = 0.017, respectively), and tended to influence IGF-I levels similarly (P = 0.098 and P = 0.07). MDDD also significantly influenced mean daily increase in lower leg length (MDILL; P < 0.01). IGFBP-3 and IGF-I levels were significantly related to MDILL (ANCOVA: P < 0.01). The correlation coefficients for IGFBP-3 and IGF-I levels and MDILL were 0.2 and 0.3 (both P < 0.0001), respectively. IGFBP-3 and IGF-I levels were highly correlated (r(2) = 0.52, P < 0.0001) and both increased significantly with increasing PMA (P < 0.0001). IGF-I levels were higher in females (P = 0.036).

CONCLUSION

This study provides evidence that the growth-restricting effects of dexamethasone may be mediated, at least in part, via suppression of the IGF axis. Both dexamethasone dose and treatment regimen influence circulating IGF-I and IGFBP-3 levels, and both are important in inducing growth restriction.

Do antenatal corticosteroids help in the setting of preterm rupture of membranes?

OBJECTIVE

It is now accepted that corticosteroid administration before preterm delivery reduces neonatal mortality and morbidity. However, corticosteroid use in the setting of rupture of membranes remains controversial.

STUDY DESIGN

We reviewed data from the first and largest randomized trial in this area and included them in a new meta-analysis.

RESULTS

Data from 318 women with rupture of membranes in the Auckland Trial showed that there was a trend toward reduction of the risk of respiratory distress syndrome with corticosteroids but that this trend did not reach statistical significance. There was little effect on the risks of neonatal death, intraventricular hemorrhage, and fetal, neonatal, or maternal infection. Combined data from 15 controlled trials involving >1400 women with rupture of membranes confirmed that corticosteroids reduce the risks of respiratory distress syndrome (relative risk, 0.56; 95% confidence interval, 0.46-0.70), intraventricular hemorrhage (relative risk, 0.47; 95% confidence interval, 0.31-0.70), and necrotizing enterocolitis (relative risk, 0.21; 95% confidence interval, 0.05-0.82). They also may reduce the risk of neonatal death (relative risk, 0.68; 95% confidence interval, 0.43-1.07). They do not appear to increase the risk of infection in either mother (relative risk, 0.86; 95% confidence interval, 0.61-1.20) or baby (relative risk, 1.05; 95% confidence interval, 0.66-1.68). The duration of rupture of membranes does not alter these outcomes.

CONCLUSION

The available data indicate that corticosteroid administration is beneficial in the setting of rupture of membranes. In our opinion further trials to address this question cannot be justified.

Inter- and intra-observer variability in the assessment of atelectasis and consolidation in neonatal chest radiographs

BACKGROUND

Radiology is an essential part of neonatal intensive care. Interpretation of chest radiographs frequently contributes to respiratory management of neonates, but there has been little assessment of the consistency of this interpretation.

OBJECTIVE

To assess the inter- and intra-observer variability for the reporting of atelectasis and/or consolidation in neonatal chest radiographs.

MATERIALS AND METHODS

A total of 585 chest radiographs from the 220 babies ventilated in our nursery over a 2-year period were coded by two radiologists for generalised, lobar and segmental atelectasis and/or consolidation. Two months later one of the radiologists re-coded a random sample of these films (n = 117, 20 %). Agreement was assessed by the kappa statistic and by proportions of agreement for normality and abnormality.

RESULTS

The reported incidence of focal atelectasis was low (5-6 %). Focal changes of any nature were found in 21-26 % of films. Inter-observer agreement was fair to moderate (kappa = 0.25-0.44). Intra-observer agreement was mostly moderate to good (kappa = 0.38-0.66).

CONCLUSION

The poor inter-observer agreement for the diagnosis of pulmonary parenchymal abnormalities on chest radiographs of neonates receiving intensive care suggests that abnormalities should be described rather than diagnoses given or that a list of differential diagnoses be offered. When research involves radiographic interpretation, the potential lack of consistency in reporting abnormalities must be borne in mind.

Side effects of 2 different dexamethasone courses for preterm infants at risk of chronic lung disease: a randomized trial

OBJECTIVE

We hypothesized that a pulsed course of dexamethasone would result in better linear growth than a 42-day reducing course in preterm infants at risk for chronic lung disease of prematurity.

STUDY DESIGN

Forty infants with a birth weight of < or =1,250 g who required mechanical ventilation at 7 days of age were randomly assigned to a repeatable 3-day pulse course of dexamethasone commencing immediately or a 42-day (long) course commencing at 14 days of age if they still required mechanical ventilation and supplemental oxygen. The primary outcome measure was linear growth at 36 weeks' postmenstrual age measured by knemometry.

RESULTS

There was no difference in lower leg length at 36 weeks' postmenstrual age. Infants receiving the pulse course had lower rises in blood pressure, less myocardial hypertrophy, and less adrenal suppression. However, more infants required supplemental oxygen at 28 days' postnatal age (14/18 vs 8/21, P < .05) and 36 weeks' PMA (8/16 vs 5/20, P = .12).

CONCLUSION

In preterm infants at risk for chronic lung disease, a pulsed course of dexamethasone has fewer side effects than a long course but may be less effective at preventing chronic lung disease.

The role of neonatal chest physiotherapy in preventing postextubation atelectasis

We retrospectively assessed atelectasis in 297 postextubation radiographs from 220 babies who underwent ventilation over a 2-year period. All 95 babies in the first year received peri-extubation chest physiotherapy; none of the 125 babies in the second year received chest physiotherapy. There was no difference in the incidence of postextubation atelectasis between the two groups.

Chest physiotherapy may be associated with brain damage in extremely premature infants

OBJECTIVES

To determine whether a characteristic form of brain damage (encephaloclastic porencephaly) was associated with chest physiotherapy treatment in preterm babies.

METHODS

A retrospective case-control study was undertaken among 454 infants of birth weight less than 1500 gm cared for during the 3-year period of 1992 to 1994. Thirteen babies of 24 to 27 weeks of gestation who weighed 680 to 1090 gm at birth had encephaloclastic porencephaly. Twenty-six control subjects were matched for birth weight and gestation.

RESULTS

The patients received two to three times as many treatments with chest physiotherapy in the second, third, and fourth weeks of life as did control infants (median 79 vs 19 treatments in the first 4 weeks, p < 0.001). Patients also had more prolonged and severe hypotension in the first week than did control subjects (median duration of hypotension 4 vs 0.5 days, p < 0.01), and were less likely to have a cephalic presentation (31% vs 81%, p < 0.01). Since December 1994 no very low birth weight baby has received chest physiotherapy treatment in the first month of life in our nursery, and no further cases have occurred.

CONCLUSIONS

Encephaloclastic porencephaly may be a previously unrecognized complication of chest physiotherapy in vulnerable extremely preterm infants.

One year audit of a referral fetal echocardiography service

AIM

To perform a one year audit of a referral fetal echocardiography service.

METHODS

In 1992, 132 fetuses were referred for two dimensional fetal echocardiography, 40% being less than 24 weeks gestation. Validation of the accuracy of the fetal diagnosis by postnatal clinical or appropriate cardiac investigation was undertaken.

RESULTS

Indications for referral were a family history of congenital heart disease (n = 36), maternal indications, (40) suspected congenital heart disease on obstetric scan, (21) noncardiac fetal abnormality (19) and fetal arrhythmia. (16) The fetal echocardiogram was normal in 112, abnormal in 18 and not technically possible in two. The negative prediction of congenital heart disease was 96% accurate with four cases of congenital heart disease not diagnosed in utero. The positive prediction of congenital heart disease was 93% accurate with one false positive of a ventricular septal defect. The overall incidence of congenital heart disease was 17%. Four of 14 fetuses with major congenital heart disease had a chromosomal abnormality and five a coexistent noncardiac abnormality. The outcome of these 14 fetuses was poor, with three stillbirths, one termination of pregnancy, seven neonatal deaths and three only surviving beyond the neonatal period. Eleven of 21 cases referred with suspected congenital heart disease on obstetric scan were abnormal.

CONCLUSION

Detailed fetal echocardiography can predict significant congenital heart disease with a high degree of accuracy. Suspected cardiac abnormality on obstetric scans warrants referral for detailed fetal echocardiography, as do those considered at increased risk of congenital heart disease.

A randomized, controlled trial of antepartum thyrotropin-releasing hormone and betamethasone in the prevention of respiratory disease in preterm infants

OBJECTIVE

The objective was to investigate whether the addition of thyrotropin-releasing hormone to antepartum betamethasone further reduces the incidence of respiratory disease in preterm infants.

STUDY DESIGN

A randomized, placebo-controlled, double-blind trial of antepartum thyrotropin-releasing hormone (400 micrograms given intravenously four times) and betamethasone (5 mg given intramuscularly four times) was conducted in 378 mothers likely to be delivered between 24 and 32.6 weeks' gestation. Statistical analysis was by relative risk, chi 2, t tests, and multiple logistic regression analysis.

RESULTS

Four hundred five live-born infants were delivered. In infants without lethal abnormalities delivered between 24 hours and 10 days from entry (n = 175) the incidence of respiratory distress syndrome was reduced from 52% to 31% (relative risk 0.61, 95% confidence interval 0.41 to 0.89) and that of severe respiratory distress syndrome from 42% to 20% (relative risk 0.48, 95% confidence interval 0.29 to 0.78) in the placebo and thyrotropin-releasing hormone groups, respectively. The number of deaths fell from 14 to one (relative risk 0.08, 95% confidence interval 0.01 to 0.63). The incidence of chronic lung disease was not significantly different, but that of an adverse outcome (chronic lung disease or death by 36 weeks' gestation) fell from 29% in the placebo group to 16% with thyrotropin-releasing hormone (relative risk 0.55, 95% confidence interval 0.31 to 0.99).

CONCLUSION

The addition of thyrotropin-releasing hormone to antepartum glucocorticoid treatment reduces the incidence of respiratory distress syndrome and improves survival in preterm infants.

Patent ductus arteriosus: how important to which babies?

An overview is presented of 21 randomised controlled trials of either surgical closure of the ductus arteriosus or indomethacin therapy in preterm infants. All trials included backup treatment if the ductus arteriosus persisted. Overall, there is no significant effect on mortality or chronic lung disease. In trials treating at a presymptomatic stage, there is a trend to reduce the incidence of chronic lung disease. Early treatment with indomethacin reduces the incidence of periventricular haemorrhage. An ultrasound study of 110 very low birth weight infants showed ductus arteriosus size at 3 days to be related to factors reflecting the infants' condition (ventilation indices, blood product administration), but not to birth weight or gestational age. Infants with a moderate to large ductus arteriosus at 3 days had a significantly lower blood pressure from 12 h of age onwards than those with a closed or small ductuses.

Transportation of very low birthweight infants in 1986

Details on transportation of all infants with a birthweight less than 1500 g born in 1986 have been recorded. Of 413 liveborn infants, 182 (42.3%) were involved in 256 transportations. Sixty-eight infants (16.5%) were transported from home or from a lesser to a more sophisticated neonatal unit within 48 hours of birth for neonatal intensive care. Twenty-five infants (6.1%), comprising 12 in utero (9 mothers) and 13 liveborn infants were transported out of their region because of a lack of intensive care spaces locally: 17 of these infants, including five born in National Women's Hospital, were Auckland and Northland infants (this representing 15% of regional very low birthweight infants). Hamilton received 12 infants from outside their region (14% of very low birthweight infants cared for). One hundred and fifty-three infants (45.1% of 339 surviving infants) were transported from one of the five regional neonatal intensive care centres to a smaller centre nearer home following recovery from intensive care. Most neonatal transportation is highly appropriate transfer within regions enabling scarce skills and resources to be concentrated in the regional centre and allowing infants to return nearer home when they are no longer sick. The number of very low birthweight infants coming to neonatal intensive care units increased dramatically in the decade prior to 1986 despite a fall in total New Zealand births. Now that the total births are increasing again the pressure on neonatal intensive care spaces is likely to increase further.

Contrast echocardiographic assessment of the neonatal ductus arteriosus

Contrast echocardiography is a safe and accurate method of diagnosing patent ductus arteriosus (PDA) in newborn infants. In this study the presence of PDA in very low birthweight infants receiving mechanical ventilation was investigated by contrast echocardiography. This was used as a basis for determining the accuracy of clinical signs and M mode echocardiography in the diagnosis of PDA. At the first contrast echocardiographic examination at a mean age of 49 hours PDA was found in 75% of infants. Clinical signs were inconsistent; 42% of the infants with PDA at the first examination had a murmur, no relation being found between PDA and heart rate or cardiothoracic ratio. Left atrial and left ventricular dimensions were significantly raised and left systolic time intervals significantly lower in the group with PDA. There was, however, considerable overlap, with the sensitivity of each measurement varying between 52% and 71%. Left systolic time interval combined with left ventricular:aortic root ratio gives the best differentiation between infants with or without PDA.

Diels-Alder adducts of fulvenes and halogenated dienes. Synthesis and insecticidal activity

A series of eight adducts (1--8) of substituted fulvenes and polychlorinated cyclodienes was synthesized by Diels-Alder cyclization. The products isolated were the endo bicyclo adducts as determined by detailed 1H and 13C NMR spectral analysis. Steric hindrance of end-product bridge substituents coupled with bulky substituents at C6 of the fulvenes led to one isomeric product in most cases. Compounds 1--8 demonstrated weak insecticidal action in Musca domestica as determined by topical LD50 and oral LC50 assays.