Early nasal continuous positive airway pressure for preterm neonates: the need for randomized trials

The use of early nasal continuous positive airway pressure (nCPAP) as prophylaxis and treatment for respiratory distress syndrome in preterm neonates, with or without prophylactic surfactant, is becoming increasingly popular. However, the justification for this is limited to comparisons between centres and comparisons of historical controls.

CONCLUSION

Randomized trials and appropriate evaluation of the nCPAP technique are needed.

[Oxygen during delivery and cerebral vasoconstriction in preterm infants]

To determine if the use of oxygen in the delivery room influences subsequent global cerebral blood flow (CBF), 70 infants of gestational age of less than 33 completed weeks were randomly assigned to receive room air (group I) or 80% oxygen (group II) during the initial stabilisation at birth. In group I supplemental oxygen was administered on clinical indications, when required. After being admitted to the neonatal intensive care unit all infants were treated according to our normal practice. At a postnatal age of two hours CBF was measured by xenon clearance. Seventy four per cent of the infants in group I were successfully established without the need for supplemental oxygen. CBF was significantly higher in group I than in group II (CBF median (interquartile range): 15.9 (13.6-21.9) vs 12.2 (10.7-13.8) ml/100 g/minute). Differences in oxygen exposure seemed to be the only explanation for the differences in CBF. No differences in short term outcome were found between the groups.

Initial treatment of preterm infants--continuous positive airway pressure or ventilation?

The question of which strategy is the best in the initial treatment of preterm infants has been on debate for years. Especially in Scandinavia, but also in other parts of the world, there is a strong tradition of early treatment with nasal continuous positive airway pressure (CPAP), while other European and North American centres prefer early intubation and mechanical ventilation. This article gives a brief overview of the history of CPAP, and the current treatment strategies as well as outcomes from a tertiary care Danish neonatal centre are presented. These data suggest that early nasal CPAP may be as good as initial mechanical ventilation with regard to mortality rates and adverse cerebral outcome and perhaps better in preventing chronic lung disease. The results must, however, be interpreted with caution, as the populations in different centres may be incomparable, even when adjustment for severity of illness is performed. A clinical randomized trial comparing initial intubation and mechanical ventilation with initial nasal CPAP using current techniques is therefore not only warranted but is indeed an absolute necessity to answer the question of which treatment is the best.

Changes in EEG, systemic circulation and blood gas parameters following two or six aliquots of porcine surfactant

Surfactant instillation often causes transient EEG suppression, the cause remaining unknown. To compare the timing of the EEG changes with the timing of the changes in blood gases and systemic circulation we compared two administration modes: 20 preterm infants were randomly assigned to receive the initial dose of surfactant divided into two or six aliquots. Heart rate, blood pressure and transcutaneous blood gases were measured continuously, while left ventricular output was estimated intermittently. No difference in blood gas response was found between the groups, whereas the circulatory changes occurred more gradually with six aliquots. EEG suppression was similar in the two groups and not related to the circulatory or the respiratory changes. Left ventricular output increased in all patients following surfactant instillation. We conclude that the EEG suppression is not directly related to alterations in blood gases or systemic circulation.

Oxygen at birth and prolonged cerebral vasoconstriction in preterm infants

To determine if the use of oxygen in the delivery room influences subsequent global cerebral blood flow (CBF), 70 infants of gestational age of less than 33 completed weeks were randomly assigned to receive room air (group I) or 80% oxygen (group II) during the initial stabilisation at birth. In group I supplemental oxygen was administered on clinical indications, when required. After being admitted to the neonatal intensive care unit all infants were treated according to our normal practice. At a postnatal age of 2 hours CBF was measured by xenon clearance. Seventy four per cent of the infants in group I were successfully stabilised without the need for supplemental oxygen. CBF was significantly higher in group I than in group II (CBF median (interquartile range): 15.9 (13.6-21.9) v 12.2 (10.7-13.8) ml/100 g/minute). Differences in oxygen exposure seemed to be the only explanation for the differences in CBF. No differences in short term outcome were found between the groups.

Cerebral blood flow and left ventricular output in spontaneously breathing, newborn preterm infants treated with caffeine or aminophylline

Aminophylline and caffeine are commonly used for prophylaxis of apnea in premature infants. Previous studies have indicated different effects of the drugs on cerebral circulation. Therefore, we have compared the acute effects of bolus administration of caffeine citrate or aminophylline on left ventricular output, heart rate, blood pressure and global cerebral blood flow. The study group consisted of 33 newborn, spontaneously breathing, preterm infants randomly assigned to receive either aminophylline 5 mg/kg (n = 19) or caffeine citrate 20 mg/kg (n = 14). Two hours after iv drug administration, global cerebral blood flow measured by the Xe-clearance technique was significantly lower after aminophylline than after caffeine (mean (SD)): 13.2 (+2.9/-2.3) versus 17.2 (+7.1/-5.1) ml/100 g/min) (p = 0.01). There were no other statistically significant differences in circulatory or ventilatory parameters between the groups. Further studies are needed to clarify the clinical relevance of these results.

Morphine pharmacokinetics in premature and mature newborn infants

The pharmacokinetics of a single dose of morphine was investigated in five term infants (gestational age 37-40 weeks) and eight preterm infants (gestational age 25-32 weeks). In the five term infants, median (range) volume of distribution at steady state (Vd beta) was 1758 (634-2700) ml/kg, plasma clearance (Cl) was 4.73 (1.75-6.61) ml/kg/min and terminal half-life (T1/2) was 224 (107-394) min. In the eight preterm infants, Vd beta was 2366 (1662-2876) ml/kg, Cl was 2.82 (1.88-6.60) ml/kg/min and T1/2 was 556 (248-834) min. No correlation was found between clearance and gestational age, but we found a significant negative correlation between T1/2 and gestational age. We conclude that there is considerable variation in the pharmacokinetic properties of morphine in both term and preterm newborn infants. Because of this variation, careful individual assessment of the clinical effect of therapy with morphine in newborn infants should be exercised.

Cerebral blood flow and plasma hypoxanthine in relation to surfactant treatment

We have previously reported reduction in EEG activity in preterm babies after tracheal instillation of Curosurf. To elucidate the cause of EEG depression, we have examined cerebral blood flow (CFB), amplitude-integrated EEG (aEEG), mean arterial blood pressure (MABP) and plasma hypoxanthine (Hx) concentration in a group of preterm babies before and immediately after administration of surfactant. No change occurred in CBF immediately after surfactant treatment despite a significant decrease in MABP. At 60 min after surfactant administration, a significant reduction in CBF occurred (p < 0.05). However, when CBF values were corrected for changes in PaCO2, no reduction in CBF was observed. Mean plasma Hx concentration was 11.6 (SD 7.3) mumol/l before surfactant therapy, which decreased significantly to 8.1 (5.8) mumol/l (p < 0.05) 15-30 min after treatment. No correlations were found between plasma Hx concentration and FiO2, a/A pO2, PaCO2, SaO2, arterial blood pressure, CBF or the degree of EEG depression. This study indicates that EEG depression observed after surfactant instillation is not caused by cerebral ischemia.

[Transportation of sick newborn infants]

In a six month period, 96 newborn infants were transferred from local hospitals to the Department of Neonatology, State University Hospital (Rigshospitalet), Copenhagen. Complications related to transport and potential risk factors were registered prospectively. Considering the condition of the infants, 31% of the transports were not carried out under optimal conditions. Serious complications occurred in 13% of the transports of infants at risk for cardio-pulmonary insufficiency. In 25% of the intubated infants, complications related to displacement of the tracheal tube were observed on arrival, but in only one of these cases the complication was recognized and treated during transport. Hypothermia occurred frequently in low birth weight infants. Failing monitoring equipment and difficulties with stethoscopy and other observations during transport may have contributed to the fatal outcome in one case. Careful planning of neonatal transports according to listed recommendations and considering the specific problems in each case may prevent complications.