Blood gases and acid-base status of the human second-trimester fetus.

Maternal arterial, umbilical venous, and umbilical arterial blood were obtained at fetoscopy in the second trimester and analyzed for blood gases and acid-base indexes. In comparing umbilical venous (N = 31) with maternal arterial (N = 39) samples, the mean (+/- SD) PO2 was lower (55 +/- 7 versus 100 +/- 15 mmHg, P less than .001) and PCO2 (37 +/- 4 versus 34 +/- 4 mmHg), bicarbonate (20 +/- 2.0 versus 18.5 +/- 1.5 mmol/L), lactate (1.10 +/- 0.25 versus 0.80 +/- 0.30 mmol/L), and base excess (-4.2 +/- 2.3 versus -6.0 +/- 1.5 mmol/L) were higher (P less than .001). The mean umbilical venous pH did not differ significantly from the maternal arterial (7.358 +/- 0.040 versus 7.373 +/- 0.035). Comparing umbilical arterial (N = 21) with umbilical venous (N = 31) samples, the PO2 level was lower (34 +/- 4 versus 55 +/- 7 mmHg, P less than .001) and PCO2 higher (42 +/- 4 verus 37 +/- 4 mmHg, (P less than .001); the pH was marginally lower (7.339 +/- 0.03 versus 7.358 +/- 0.040; P less than .05) and bicarbonate higher (22 +/- 1.5 versus 20 +/- 2.0 mmol/L, P less than .001). Umbilical arterial and umbilical venous values were similar in the case of lactate and base excess.

Congenital bacterial sepsis in very preterm infants.

The results of body fluid and surface cultures from 148 preterm infants less than 33 weeks gestational age obtained routinely on admission to a neonatal intensive care unit were reviewed. The aim was to determine the occurrence of congenital bacterial sepsis in this population and to examine whether surface cultures yielded information helpful in management. Gastric aspirate and umbilical, nasal and ear swabs were cultured and the results were compared to those of blood cultures. Nine infants (5.4%) had congenital bacterial sepsis diagnosed by positive blood cultures. Only the results of microscopy of gastric aspirate were available within hours of birth and before the results of blood culture. Microscopy of gastric aspirate, demonstrating pus cells, alone had a sensitivity of 0.86 in predicting congenital sepsis but a specificity of 0.49; the specificity, however, rose to 0.80 if both organisms and pus cells were observed on microscopy. Thus, only this combination was a useful pre-indicator of congenital sepsis. In infants who did not develop septicaemia, treatment was modified only if Streptococcus agalactiae was cultured from surface sites; in all such cases, the organism was grown from the ear swab. Our results demonstrate that congenital bacterial sepsis is common amongst very preterm infants admitted for neonatal intensive care but routine screening of surface cultures should be restricted to an ear swab only.

Birth weight and special educational needs: effects of an increase in the survival of very low birthweight infants in London.

OBJECTIVES: To assess the contribution of children with different birth weights to special educational needs within a single health district, and to determine whether this pattern changed over the time when the survival of very low birthweight (VLBW) infants was increasing. SETTING: An inner London health district. STUDY DESIGN: A cohort of children born to local parents between January 1974 and December 1980 was selected from birth notifications, including only those infants who survived for more than one month. Community child health records were then inspected to identify children from the cohort who had been formally assessed for special educational needs before their 8th birthday. The risk of special educational needs was compared for the years 1974-77 and 1977-80 (the first and second halves of the period studied). SUBJECTS: The infant cohort consisted of 31,846 children. Altogether 260 (0.8%) of these were later assessed formally. RESULTS: VLBW infants were 4.4 times more likely to be assessed than normal birthweight infants. Formal assessment within the district occurred in three of 68 VLBW infants from the first half of the period studied, and three of 120 from the second half. CONCLUSION: Although VLBW infants are at higher risk, an increase in their survival was not associated with any increase in their contribution to the group with special educational needs within our district. Their contribution, as a group, to the total number of children with special educational needs is very small.

Birthweight-specific risk factors for necrotising enterocolitis.

In a multicentre case-control study of necrotising enterocolitis risk factors were found to vary with birthweight of cases. In very low birthweight cases the risk factors identified were those associated with prolonged or recurrent hypoxia (recurrent apnoea, respiratory distress, assisted ventilation, and umbilical artery catheterisation). In heavier birthweight infants the risk factors were, in contrast, related to hypoxia at birth (low 1 minute Apgar score and endotracheal intubation at birth) and umbilical vessel catheterisation used in exchange transfusions. Contradictory findings in published case-control studies carried out in the USA may be due to differences in patient populations and management policies. Hypoxia and umbilical vessel catheterisation should still be considered as risk factors for necrotising enterocolitis.

Neonatal meconium aspiration syndrome and respiratory morbidity during infancy.

Respiratory morbidity in the first 6 months of life of 35 infants who had had neonatal meconium aspiration syndrome (MAS) was compared to that of 70 controls, also born at term, matched for gender and ethnic origin. The number of infants in the two groups who were symptomatic was compared. Infants were described as symptomatic if, following discharge from hospital, they had at least one episode of wheezing and/or coughing which lasted for 3 days or more. There was no significant difference between the two groups regarding parental smoking or the proportion of infants who had a family history of atopy. A significantly greater proportion of the MAS group (49%) than of the control group (20%) was symptomatic at follow-up. Eight (23%) infants with MAS and 2 (3%) controls had symptoms which necessitated regular bronchodilator therapy. The 8 infants with MAS who were on maintenance bronchodilator therapy had required significantly longer neonatal respiratory support and had larger lung volumes at follow-up than the other 27 infants. We conclude that neonatal meconium aspiration syndrome is associated with increased respiratory morbidity in the first 6 months of life.

Respiratory function at follow-up after neonatal surfactant replacement therapy.

Respiratory function was assessed at a median of 7 months (range 6-12) in 17 preterm infants who, in the neonatal period, had been entered into a multi-centre randomized placebo-controlled trial of prophylactic surfactant replacement therapy. Seven infants (median gestational age 28 weeks) received surfactant and the remaining ten infants (median gestational age 27 weeks) placebo. Respiratory function was assessed by measuring functional residual capacity (FRC), thoracic gas volume (TGV) and airways resistance (RAW). Specific conductance (SGAW) was calculated from RAW and TGV. There was no significant difference in FRC or TGV between the two groups. RAW, however, was significantly lower in the surfactant (median 41, range 21-48 cmH2O l-1 s-1) compared to the placebo group (median 57, range 40-68 cmH2O l-1 s-1), P < 0.05 and SGAW significantly higher in the surfactant (median 0.136, range 0.063-0.289 l cmH2O-1 s-1) compared to the placebo group (median 0.081, range 0.062-0.134 l cmH2O-1 s-1), P < 0.05. These results suggest that surfactant replacement therapy improves lung function at follow-up.

High frequency oscillation for preterm infants with severe respiratory failure.

High frequency oscillation (HFO) as rescue treatment for preterm infants with severe respiratory failure has been assessed and prognostic factors identified. Thirty six infants with a median gestational age of 27 weeks were studied. Immediately before transfer to HFO, the infants were receiving an inspired oxygen concentration of > or = 85% and/or a mean airway pressure of > or = 12 cm H2O and had a median alveolar-arterial oxygen gradient (A-aDO2) of 73.28 kPa (range 49.34-89.91). Seventeen infants subsequently died. Comparison of those 17 with the remaining 19 infants demonstrated that respiratory distress syndrome and persistent fetal circulation were associated with a significantly better outcome than pulmonary airleak. The A-aDO2 after two and six hours on HFO was significantly higher in those infants who survived compared with those who died. We conclude that a diagnosis of pulmonary airleak and failure to show early improvement in respiratory status indicate a poor prognosis when HFO is used as rescue treatment.

Prediction of early tolerance to enteral feeding in preterm infants by measurement of superior mesenteric artery blood flow velocity.

AIMS: To evaluate whether serial Doppler measurements of superior mesenteric artery (SMA) blood flow velocity after the first enteral feed could predict early tolerance to enteral feeding in preterm infants. METHODS: When clinicians decided to start enteral feeds, Doppler ultrasound blood flow velocity in the SMA was determined before and after a test feed of 0.5 ml milk. The number of days taken for infants to tolerate full enteral feeding (150 ml/kg/day) was recorded. RESULTS: Fourteen infants (group 1) achieved full enteral feeding within seven days. Thirty infants (group 2) took 8-30 days. There was no difference in the preprandial time averaged mean velocity (TAMV) between the groups at a median age of 3 (2-30) days. In group 1, there was a significant increase in TAMV (p<0.01) above the preprandial level at 45 and 60 minutes, but this did not occur in group 2. An increase in TAMV by more than 17% at 60 minutes has a sensitivity of 100% and a specificity of 70% for the prediction of early tolerance to enteral feeds. CONCLUSIONS: There is a significant correlation between an increase in mean SMA blood flow velocity and early tolerance of enteral feeding. Doppler measurements of SMA blood flow velocity may be useful for deciding when to feed high risk preterm infants.

Growth effects of systemic versus inhaled steroids in chronic lung disease.

AIM: To compare the effects of inhaled and systemic steroids on growth in very low birthweight (VLBW) infants with chronic lung disease (CLD). METHODS: Sixteen babies with CLD randomly received inhaled budesonide (100 microg four times daily for 10 days via Aerochamber) or systemic steroids (dexamethasone 0.5 mg/kg/day, reducing over nine days). Linear growth (lower leg length, LLL) was measured by knemometry twice weekly. RESULTS: The gestational age, birth weight, postnatal age, and LLL velocity (LLLvel) were similar between the two groups at the start of treatment. At the end of the treatment period, LLLvel was reduced in the dexamethasone group (mean -0.01 mm/day) but had increased in the budesonide group (mean 0.48 mm/day). Mean weight gain was non-significantly lower in the dexamethasone group (5.8 g/kg/day) compared to the budesonide group (mean 12.7 g/kg/day). CONCLUSION: Inhaled budesonide has less short term effects on growth than systemically administered dexamethasone.

Preterm prelabour amniorrhexis: intrauterine infection and interval between membrane rupture and delivery.

This study aimed to determine if fetal bacteraemia and amniotic fluid infection at the time of membrane rupture reduces the interval between membrane rupture and the onset of labour in pregnancies complicated by preterm prelabour amniorrhexis. Sixty nine pregnancies with preterm prelabour amniorrhexis at 12-36 weeks' gestation that were managed expectantly had spontaneous onset of labour. In all cases cordocentesis and amniocentesis were performed and fetal blood and amniotic fluid were cultured for aerobic and anaerobic bacteria. In the group with negative fetal blood and amniotic fluid cultures (group 1) the median interval from amniorrhexis to delivery was 41 days (range 1-161) and there was an inverse correlation between gestational age at amniorrhexis and delivery interval. In the group with negative fetal blood but positive amniotic fluid cultures (group 2) the median amniorrhexis to delivery interval was nine days (range 1-37), and in the group with positive fetal blood cultures (group 3) the interval was two days (range 1-5). These findings suggest that pregnancies complicated by preterm prelabour amniorrhexis and fetal bacteraemia undergo spontaneous labour within five days of membrane rupture, and if labour does not occur then infection is unlikely.

Effect of fresh frozen plasma and gammaglobulin on humoral immunity in neonatal sepsis.

Fresh frozen plasma and intravenous immunoglobulin are used as prophylaxis against, and for the treatment of, neonatal infection. It is assumed that any beneficial effect is mediated through the humoral immune factors contained in each preparation. The effect of fresh frozen plasma and intravenous immunoglobulin on humoral immune markers (immunoglobulins and IgG subclasses, complement components and activation products, and C reactive protein) was investigated over a 24 hour period after their randomised administration to 67 infants with suspected infection. Thirty infants without suspicion of infection were studied as controls. Compared with control infants, infants with suspected infection had increased concentrations of C reactive protein, reduced concentrations of fibronectin, and increased concentrations of the complement activation marker C3d, but similar concentrations of IgG, IgG subclasses, IgA, and IgM. After intravenous immunoglobulin treatment (500 mg/kg) concentrations of total IgG and all IgG subclasses increased, as did IgA and complement component C4. Concentrations of C reactive protein decreased after intravenous immunoglobulin treatment and were significantly lower than baseline after 24 hours. In contrast, no change in IgG or IgG subclass concentrations occurred after fresh frozen plasma administration. At 24 hours after fresh frozen plasma administration, concentrations of IgA, IgM, and C4 were significantly higher than baseline and serum IgA was significantly higher than in infants tested 24 hours after intravenous immunoglobulin treatment. These results confirm the rational basis for intravenous immunoglobulin treatment but question the value of fresh frozen plasma, particularly in the light of its attendant problems as an untreated blood product.

Use of the CRIB (clinical risk index for babies) score in prediction of neonatal mortality and morbidity.

A prospective study of the outcome of care of a regional cohort of very low birthweight (< 1500 g) and very preterm (< 32 weeks) infants was carried out. Its aims were to assess the ability of the CRIB (clinical risk index for babies) score, rather than gestational age or birthweight, to predict mortality before hospital discharge, neurological morbidity, and length of stay, and to access CRIB score as an indicator of neonatal intensive care performance. 676 live births fulfilled the criteria and complete data were available for 643 (95%). Compared with gestation and birthweight, CRIB was better for the prediction of mortality, was as good for the prediction of morbidity, and was not as good for the prediction of length of stay. CRIB adjusted mortality did not demonstrate better performance in units providing the highest level of care. Either the CRIB score was not sensitive to performance or the level 3 hospitals in this study were performing badly. On the basis of this analysis purchasers and providers of neonatal intensive care cannot yet rely on the CRIB score as a performance indicator.

Gas trapping during high frequency positive pressure ventilation using conventional ventilators.

Inspiratory and expiratory volumes were measured in 51 preterm infants with respiratory distress syndrome (RDS), when comparing two ventilator rates, 60 and 120 breaths/min. Gas trapping was not demonstrated at rates of 60, but in 11 infants at 120 breaths/min and this was more common in the paralysed infants and those more mature than 31 weeks gestational age (P less than 0.05). The median change in functional residual capacity resulting from gas trapping was 3.8 ml/kg. We conclude rates of 120 breaths/min can be used in the majority of non-paralysed infants without gas trapping but should be avoided in paralysed infants more mature than 31 weeks.

Arterial blood pressure and blood flow velocity in major cerebral and visceral arteries. II. Effects of colloid infusion.

To compare the effects of acute changes in blood pressure on arterial blood flow velocity in various regional circulations, Doppler ultrasound measurements of blood flow velocity were recorded from the anterior cerebral artery (ACA), superior mesenteric artery, coeliac axis and left renal artery. Measurements were obtained from 10 ventilated very low birth weight infants before and after plasma infusions given to treat systemic hypotension on the first day of postnatal life. Blood pressure increased in 8/10 infants, and in this group there was a significant increase in ACA and coeliac axis blood flow velocity. For the ACA only, there was a significant association between the change in blood flow velocity and the magnitude of the change in blood pressure (r = 0.73, P < 0.02). Mesenteric and renal artery velocity did not increase after the infusion. For ventilated VLBW infants on the first day of life, arterial blood flow velocity was affected by acute changes in blood pressure in the cerebral circulation only.

Arterial blood pressure and blood flow velocity in major cerebral and visceral arteries. I. Interindividual differences.

In order to determine the relationship between blood pressure and arterial blood flow velocity in various regional circulations, Doppler ultrasound measurements of blood flow velocity were recorded on the first day of postnatal life from the anterior cerebral (ACA), superior mesenteric, coeliac axis and left renal artery. In 34 ventilated very low birth weight (VLBW) infants, results were correlated with arterial blood pressure and blood gases in a multiple regression model. ACA velocity was correlated with blood pressure (r = 0.70) and PaCO2 (r = 0.64), but there was no relationship between blood pressure and velocity in the other arteries. Repeated measurements were performed at one week of age in 15 infants. Blood flow velocity in the cerebral and renal arteries was related to blood pressure; velocity in the cerebral arteries was inversely correlated with PaO2 and velocity in the coeliac and mesenteric arteries was positively correlated with PaO2. In VLBW infants on the first day of life, blood flow velocity is related to blood pressure in the cerebral circulation only.

Home oxygen therapy following neonatal intensive care.

In a 12-month period 28 of 164 consecutive very low birthweight (VLBW) infants receiving intensive care within 48 h of birth at King's College Hospital developed chronic lung disease, (oxygen dependence beyond 28 days of age). Fifteen of the 28 infants were eligible for home oxygen therapy, but this was only practical, because of home circumstances, in 8 infants (4.9%). These 8 infants received home oxygen therapy. One further infant, born at term and suffering from pulmonary hypoplasia was also discharged home on oxygen therapy. Two infants subsequently required readmission due to a deterioration in their respiratory status and died. Three others required re-admissions (total duration 32 days) for respiratory problems. The median duration of home oxygen therapy was 17 weeks (range 4-486 days). We conclude that home oxygen therapy is needed by only a very small number of preterm infants and is appropriate for only a proportion of them. Parents need to be counselled carefully regarding the possibility that the need for oxygen might be protracted.

Inflating pressures for effective resuscitation of preterm infants.

The magnitude of inflating pressure necessary for effective resuscitation was examined in 70 preterm infants. The median pressure to cause adequate chest wall expansion was 22.8 cmH2O; no infant required a peak inflating pressure greater than 30 cmH2O. No further increase in inflation pressure was used during resuscitation and the median 5- and 10-min Apgar scores were 8 and 9, respectively.

Pleuro-amniotic shunting for fetal chylothorax.

The immediate neonatal course of two babies with gross hydrops fetalis, associated with chylothorax, is compared. One fetus managed by antenatal insertion of a pleuro-amniotic shunt had no evidence of pleural effusion at birth and required less resuscitation.

Respiratory status and diuresis following treatment with dexamethasone.

The effect of dexamethasone therapy on fluid balance, lung function and requirement for respiratory support has been assessed. Ten premature infants were studied, they had a median gestational age of 28 weeks. None of the infants had any improvement in the respiratory status for 48 h prior to commencing dexamethasone. Fluid balance, pulmonary function and requirement for respiratory support were measured 12 h prior to and for 36 h after receiving dexamethasone. There were no significant changes in fluid input over the study period, but urine output increased significantly after 12 h of dexamethasone therapy (P < 0.02). Compliance of the respiratory system only significantly improved after 36 h of dexamethasone therapy (P < 0.03), this was associated with a significant change in the inspired oxygen concentration (P < 0.05). We conclude that the improvement in respiratory status resulting from dexamethasone therapy is preceded by a diuresis.

Cerebral and renal artery blood flow velocity before and after birth.

OBJECTIVE: To document perinatal changes in cerebral and renal artery haemodynamics in premature growth-retarded and normal term infants. DESIGN: Longitudinal study of individual infants. Doppler ultrasound measurements of blood flow velocity (BFV) in the middle cerebral and renal arteries were obtained before delivery, soon after delivery and during the first week of postnatal life. SETTING: Teaching hospital obstetric and neonatal units. SUBJECTS: 13 severely growth retarded infants born at 28-36 weeks gestation, and eight normally grown infants born at term. RESULTS: In both groups, BFV in the cerebral artery was significantly lower in the first few hours after birth than in fetal life, but subsequently increased to reach pre-delivery values by the end of the first week. In contrast, BFV in the renal artery during the first postnatal day was not significantly different from fetal values, but it also increased during the subsequent week. In six of the preterm growth-retarded infants, fetal blood gases were measured in samples obtained by cordocentesis, and in these cases an increase in blood oxygen content at birth was documented. CONCLUSIONS: Cerebral artery BFV falls at birth and is relatively low during the time that premature infants are at the greatest risk of developing periventricular haemorrhage.