Point-of-care testing of neonatal coagulation.

The aim of this validation study was to compare prothrombin time (PT) and activated partial thromboplastin time (APTT) results from a point-of-care testing (POCT) device (Rapidpoint Coag) with those from standard laboratory tests. The subjects were newborn infants needing coagulation screen for any clinical indications within a regional neonatal intensive care unit. The level of agreement between POCT and laboratory measurements of PT and APTT was determined. For PT: the bias was from -7.6 to 12.4 s and precision was 5.0 s. For the detection of prolonged PT at a level of 16 s, the sensitivity was 0.70, specificity was 0.57 and the positive predictive value (PPV) was 0.62. For APTT: the bias was from -39.1 to 23.7 s, and precision was 15.7 s. For the detection of prolonged APTT at a level of 55 s, the sensitivity was 0.80, specificity was 0.95 and the PPV was 0.80. The POCT device tested has limited utility as a cot-side device for screening for a prolongation of the APTT in the newborn but is not sensitive for screening for prolongation of the PT.

Effects of transfusion in anemia of prematurity.

The authors aimed to test the hypothesis that blood transfusions depress hematopoiesis in healthy infants with anemia of prematurity (AOP). They also set out to find markers that predict recovery from AOP. Thirty-nine premature babies underwent weekly and post-transfusion measurements of hemoglobin concentrations, reticulocyte counts (RCC), and erythropoietin levels (EPO). RCC and EPO dropped significantly 7 days after a blood transfusion but had normalized after 14 days. Elevated RCC or EPO levels were not predictive of an increase in hemoglobin. Postnatal HbFg/dL was higher in babies who had received transfusions. The authors conclude that blood transfusions depress erythropoiesis in infants with AOP and stimulate HbF synthesis but this effect is not sustained. Reticulocyte counts and erythropoietin levels are unhelpful in predicting recovery from AOP.

Clinical decision support systems for neonatal care.

BACKGROUND: Clinical decision support systems (CDSS) are computer-based information systems used to integrate clinical and patient information to provide support for decision-making in patient care. They may be useful in aiding the diagnostic process, the generation of alerts and reminders, therapy critiquing/planning, information retrieval, and image recognition and interpretation. CDSS for use in adult patients have been evaluated using randomised control trials and their results analysed in systematic reviews. There is as yet no systematic review on CDSS use in neonatal medicine. OBJECTIVES: To examine whether the use of clinical decision support systems has an effect on 1. the mortality and morbidity of newborn infants and 2. the performance of physicians treating them SEARCH STRATEGY: The standard search method of the Cochrane Neonatal Review Group was used. Searches were made of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1, 2004), MEDLINE (from 1966 to August 2004), EMBASE (1980-2004), CINAHL (1982 to August 2004) and AMED (1985 to August 2004). SELECTION CRITERIA: Randomised or quasi-randomised controlled trials which compared the effects of CDSS versus no CDSS in the care of newborn infants. Trials which compared CDSS against other CDSS were also considered. The eligible interventions were CDSS for computerised physician order entry, computerised physiological monitoring, diagnostic systems and prognostic systems. DATA COLLECTION AND ANALYSIS: Studies were assessed for eligibility using a standard pro forma. Methodological quality was assessed independently by the different investigators. MAIN RESULTS: Two studies fitting the selection criteria were found for computer aided prescribing and one study for computer aided physiological monitoring.Computer-aided prescribing: one study (Cade 1997) examined the effects of computerised prescribing of parenteral nutrition ordering. No significant effects on short-term outcomes were found and longer term outcomes were not studied. The second study (Balaguer 2001) investigated the effects of a database program in aiding the calculation of neonatal drug dosages. It was found that the time taken for calculation was significantly reduced and there was a significant reduction in the number of calculation errors.Computer-aided physiological monitoring: one eligible study (Cunningham 1998) was found which examined the effects of computerised cot side physiological trend monitoring and display. There were no significant effects on mortality, volume of colloid infused, frequency of blood gases sampling (samples per day) or severe (Papile Grade 4) intraventricular haemorrhage. Published data did not permit us to analyse effects on long-term neurodevelopmental outcome. AUTHORS' CONCLUSIONS: There are very limited data from randomised trials on which to assess the effects of clinical decision support systems in neonatal care. Further evaluation of CDSS using randomised controlled trials is warranted.

A mathematical model of CO2 variation in the ventilated neonate.

A mathematical model of the variation of partial pressure of carbon dioxide in the arterial blood of a ventilated neonate is developed. The model comprises alveolar, arterial, pulmonary, venous and tissue compartments, with gas exchange in the lung determined by inspiration and expiration terms. Gas exchange is modelled through diffusion and convective transfer. Carbon dioxide is produced in the tissue by a metabolic term. Shunting is modelled by allowing blood flow to bypass the pulmonary compartment in which diffusion takes place. The model predicts changes in the carbon dioxide partial pressures that occur following abrupt changes in the ventilation settings, and show broad agreement with actual data obtained from novel sensing technology.

Central venous catheter tip in the right atrium: a risk factor for neonatal cardiac tamponade.

Fatal cardiac tamponade is a well recognised complication of the use of central venous catheters in neonatal patients. There is controversy over optimum catheter tip position to balance catheter performance against risk of adverse events. We report a series of five cases of tamponade occurring in one neonatal unit over a 4-year period, related to catheter tip placement in the right atrium. Right atrial catheter angulation, curvature or looping (CA) was present in all five cases on plain radiograph. It was frequently seen in other patients over the same period. Review of the literature indicates that CA was present in 6 of the 11 previous cases where the presence or absence of CA can be determined. Where right atrial catheter tip placement is accepted, clinicians should be aware of this characteristic catheter configuration, which is a major risk factor for cardiac tamponade. We recommend that catheter tips should not be placed in the right atrium to avoid risk of tamponade.

Effect of changes in oscillatory amplitude on PaCO(2) and PaO(2) during high frequency oscillatory ventilation.

AIMS: To describe the relation between oscillatory amplitude changes and arterial blood gas (ABG) changes in preterm infants receiving high frequency oscillatory ventilation, using a multiparameter intra-arterial sensor (MPIAS). METHODS: Continuous MPIAS ABG data were collected after amplitude changes and stratified according to FIO(2): high (> 0.4) or low (< 0.3). For each amplitude change, the maximum change (from baseline) in PaCO(2) and PaO(2) over the following 30 minutes was determined. In total, 64 oscillatory amplitude changes were measured in 21 infants (median birth weight 1040 g; gestation 27 weeks). RESULTS: All amplitude increases produced PaCO(2) falls (median -0.98 and -1.13 kPa for high and low FIO(2) groups respectively). All amplitude decreases produced PaCO(2) rises (median +0.94 and +1.24 kPa for high and low FIO(2) groups respectively). About 95% of the change in PaCO(2) was completed in 30 minutes. Amplitude changes did not affect PaO(2) when FIO(2) > 0.4. When FIO(2) < 0.3, amplitude increases produced a PaO(2) rise (median = +1.1 kPa; P < 0.001) and amplitude decreases a fall (median = -1.2 kPa; P < 0.001). CONCLUSIONS: After oscillatory amplitude changes, the speed but not the magnitude of the PaCO(2) change is predictable, and a rapid PaO(2) change accompanies the PaCO(2) change in infants with mild lung disease and a low FIO(2).

An expert system to assist neonatal intensive care.

An expert system for neonatal intensive care (ESNIC) for the management of mechanically ventilated neonates on intermittent positive pressure ventilation (IPPV) has been developed. The system uses the rule based expert system shell XiPlus (Inference Inc.) and runs on an IBM-compatible PC. The rules have been derived from the knowledge of two consultant paediatricians. The inputs to the system are the current ventilator settings, blood gas tensions and pH. The output of the system is a set of suggested new ventilator settings. The aim of the system is to provide ventilator settings which will maintain the arterial blood gas tensions within an acceptable range, reducing pressures whenever feasible and increasing pressures only as a last resort. In addition, ESNIC provides data archiving, graphical displays of all parameters, ventilation and discharge summaries. With the 63 patients in the study ESNIC was consulted for 76% of all ventilator adjustments and the advice given was accepted on 83% of these occasions.

To PEEP or not to PEEP?

It is well recognised that reducing positive end expiratory pressure (PEEP) leads to an increase in the tidal volume and minute volume in ventilated neonates. The magnitude of this effect is perhaps not commonly appreciated, however. Effectively, PEEP is four times as potent as peak inflation pressure (PIP) in bringing about changes in tidal volume. The influence of changes in PEEP and PIP on tidal volume and the relative magnitude of each are considered. Twenty one preterm infants were studied on 38 separate occasions. All were sedated, paralysed, and ventilated, 19 for hyaline membrane disease. A 1 cm H2O reduction in PEEP was twice as potent as a 2 cm H2O increase in PIP in achieving an increase in tidal volume (14 v 7%). Similarly, increasing PEEP by 1 cm H2O was twice as effective as a 2 cm H2O decrease in PIP in reducing tidal volume (13 v 6%). Small (0.5-1 cm H2O) changes in PEEP can often be used to improve ventilation and carbon dioxide elimination. Levels of PEEP of 4-5 cm H2O may, at times, impair gas exchange and contribute to overdistension.

Gastric acid secretion in preterm infants.

Little is known about the ontogeny of gastric acid secretion in the very preterm infant. In order to study this we recorded intragastric pH continuously for 24 h on 71 occasions in 22 enterally starved preterm infants. Infants ranged from 24 to 29 weeks' gestation and were studied in the first 5 days, and in the third week, of life. As the infants became more mature, both in terms of gestation and postnatal age, there was a decrease in intragastric pH from median (range) 3.7, 2.5 (0.6-3.9) and 1.8 (1.3-2.6) for infants of 24-25, 26-27 and 28-29 weeks' gestation, respectively on the first day of life to 1.8 (1.7-1.9), 2.0 (1.8-2.3) and 1.7 (1.5-2.0) on day 16. All the infants were able to maintain a gastric pH of below 4 from the first day of life. Our data lay to rest the suggestion that the preterm infant is incapable of hydrogen ion secretion. Gastric acid secretion in the newborn preterm infant should allow normal proteolytic activity and the well recognised clinical problems of intragastric bleeding, gastritis or oesophagitis may be attributable to intragastric acid.

An advisory system for artificial ventilation of the newborn utilizing a neural network.

A neural network has been developed to manage ventilated neonates. The network inputs are the current ventilator settings (inspiratory and expiratory times, peak inspiratory and positive end-expiratory pressures and inspired oxygen concentration), partial pressures of arterial blood gases and pH. Two hidden layers comprising 50 nodes each are employed in the network, which utilizes a standard back-propagation algorithm. The network provides the new ventilator settings as five outputs that represent the most appropriate ventilator settings projected to maintain blood gases within an acceptable range. The network has been trained using a data set derived from a rule-based expert system developed for the same purpose. Performances of both systems have been compared. The neural network is capable of learning and adapting to the individual patient's response, which in principle offers significant advantages over the rule-based system.

Early or late parenteral nutrition for the sick preterm infant?

No one doubts that good nutrition is an important component of neonatal intensive care, nor that this can only be accomplished by the use of intravenous fat. With regard to the effects of nutrition on bronchopulmonary dysplasia, however, we are facing a dilemma. On the one hand there is the suggestion that inadequate nutrition increases the severity of bronchopulmonary dysplasia and on the other that the use of intravenous fat predisposes to it. In an attempt to narrow the area of uncertainty we randomly allocated 129 infants of less than 1750 g birth weight to receive either early or late lipid containing parenteral nutrition. The median duration of ventilation support in the 'early' group was 8.5 days and in the 'late' group eight days; this was not significantly different.

The effect of intravenous ranitidine on the intragastric pH of preterm infants receiving dexamethasone.

Gastric perforation is a catastrophic, albeit uncommon, side effect of steroid treatment for premature infants with bronchopulmonary dysplasia (BPD). A reduction of intragastric acidity may protect against peptic ulceration. The effect of different doses of ranitidine, given as intravenous infusions, on intragastric acidity in premature neonates was therefore examined. Ten consecutive, enterally starved, infants receiving dexamethasone (0.6 mg/kg) for BPD were enrolled. Intragastric pH was continuously monitored on the day before steroid treatment and on the four following days, initially without H2 blockade and then using a continuous intravenous infusion of ranitidine at 0.031, 0.0625, and 0.125 mg/kg/hour. An infusion of 0.0625 mg/kg/hour of ranitidine was sufficient to increase and maintain gastric pH above 4; the authors therefore use this infusion during dexamethasone administration as possible prevention of gastric perforation.

Five-year-follow-up of very low birthweight infants: neurological and psychological outcome.

All surviving infants with birthweight < or = 1500 g born in 1982 and 1983 at St. James's University Hospital, Leeds, were followed up for 5 years. There were 88 survivors (including 5 in utero transfers) from the original cohort of 126 infants. In their fifth year the following assessments were made: neurological, audiological, intellectual, behavioural, growth and general health. A comparison group of full-term male infants was also studied with respect to intellectual status, social and emotional behaviour and general health. Principal neurological impairments found were: cerebral palsy 9 (10.2%), hydrocephalus 1 (1.1%), epilepsy 2 (2.3%) and sensorineural deafness 2 (2.3%). One third of the VLBW children required the services of the child development centre. Seventy-nine of the 88 VLBW children were tested with the WPPSI. Seven (8.8%) scored below 70. The VLBW boys had mean IQ scores of 90.6 while the mean for the girls was 100.2. The very low birthweight boys were significantly intellectually impaired compared with their peers. Socially and emotionally they were largely comparable with their full-term peers. The findings suggest that there has been no increase in severe disability following a policy of active neonatal intensive care. However, the quality of survival of VLBW children born in the 1980s, despite improvements in perinatal care, remains a major concern.

Changes in the plasma aminogram of parenterally fed infants treated with dexamethasone for bronchopulmonary dysplasia.

A substantial increase in the plasma concentration of most amino acids was observed in 59 preterm infants with chronic lung disease soon after the initiation of dexamethasone therapy. The size of increase appeared to be dose related. This phenomenon is likely to be the result of steroid induced protein catabolism. Interestingly, neither phenylalanine nor tyrosine concentrations were significantly increased.