H. R. Gamsu

Effects of intrauterine growth retardation on postnatal visceral and cerebral blood flow velocity.

Blood flow velocity and pulsatility index were measured with Doppler ultrasound in the superior mesenteric artery, coeliac axis, and anterior cerebral artery in 18 very low birth weight, small for gestational age infants, and compared with findings from 18 weight matched, and 18 gestation matched, appropriate for gestational age controls. Mean velocity in the superior mesenteric artery was lower in the small for gestational age infants (15 cm/s) than in the gestation matched control group (20.4 cm/s). In those small for gestational age infants who had evidence of fetal hypoxia the mean velocity in the superior mesenteric artery was even lower (11.5 cm/s). There were no differences in velocity in the cerebral artery among the groups. Infants who were small for gestational age still had significantly lower superior mesenteric artery velocity than gestation matched controls at 1 week of age. The results suggest a specific reduction in visceral perfusion in infants who are small for gestational age and who have experienced fetal hypoxia, and this could predispose these infants to necrotising enterocolitis.

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.

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.

Randomised controlled trial of colloid infusions in hypotensive preterm infants.

Colloid infusions are often given to treat hypotension in preterm infants. The aim of this work was to assess whether it was the amount of protein or the volume of the colloid infused which accounted for the observed increase in blood pressure. Sixty preterm infants were randomised (20 in each group) to receive 5 ml/kg 20% albumin, 15 ml/kg fresh frozen plasma, or 15 ml/kg 4.5% albumin. All infusions were given at a rate of 5 ml/kg/hour in addition to maintenance fluids. The infants were randomised when hypotensive (systolic blood pressure less than 40 mm Hg for two hours). There was no significant difference in the blood pressure of the three groups before or one hour after beginning the infusion. The mean increase in blood pressure one hour after completing the infusion, however, was significantly lower in infants receiving 20% albumin: 9% compared with 17% in the group receiving 4.5% albumin, and 19% in the group receiving fresh frozen plasma. It is concluded that the volume infused rather than albumin load is important in producing a sustained increase in blood pressure.

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.

Randomised controlled trial of albumin infusion in ill preterm infants

We assessed the effect of albumin infusion on weight loss and ventilation requirement in sick premature infants. Thirty infants, median gestational age 29 weeks, were entered into a randomised controlled trial, at a median of 2 days of age. The infants, all with an albumin level <-30 g/l, received either 5 ml/kg of 20% albumin or 5 ml/kg of their maintenance fluids (placebo), both given as part of the total daily fluid requirement. The response to the infusion was assessed by comparing two periods; 12 h immediately prior to the infusion and 12–24hh after the infusion. Albumin infusion was associated with a significant increase in albumin level and a significant reduction in weight, but in the placebo group there was a significant increase in weight. There were, however, no significant changes in the peak inspiratory pressure in response to either infusion. There was only a modest reduction (<15%) in the inspired oxygen concentration, which occurred in both groups, but reached statistical significance only following the albumin infusion. We conclude that our results suggest that albumin infusion in “hypoalbuminaemic” sick preterm infants is unlikely to alter their respiratory status.

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.

Nosocomial bacterial infections in very low birth weight infants.

The occurrence of congenital and nosocomial bacterial septicaemia has been documented by identifying the number of positive blood cultures by reviewing the laboratory and clinical records of 394 very low birth weight infants who were consecutively admitted to a neonatal intensive care unit over a 40-month period. The incidence of congenital septicaemia was 6% and of nosocomial septicaemia 17%. The commonest causes of congenital infection wereStreptococcus agalactiae Staphylococcus epidermidis andEnterococcus faecalis (each in 18% of cases). The commonest cause of nosocomial infection wasS. epidermidis (51% of cases), except in infants of birth weight less than 750 g. Risk factors for nosocomial infection were extremely low birth weight, very preterm birth and prolonged ventilation. Nosocomial infection was associated with significantly lengthened hospital admission.

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.

Ventilatory requirements for respiratory distress syndrome in small for gestational age infants

Neonatal ventilatory requirements and outcome were examined in 135 very preterm, small-for-gestational age (SGA) infants to determine whether fetal growth retardation protects against severe respiratory distress syndrome (RDS) in very immature infants. Their results were compared to those from gestational age-and gender-matched controls. Although there was no significant difference in the median duration of mechanical ventilation between the two groups, more SGA infants required ventilation and were ventilated because of RDS. In a subgroup also matched for mode of delivery, there was no significant difference between the proportion of SGA infants requiring mechanical ventilation for RDS compared to their matched controls. The mortality was greater in the SGA group. We conclude that fetal growth retardation does not protect against severe RDS.