Changing incidence and outcome of infants with respiratory distress syndrome in the 1990s: a population-based survey.

AIM: To evaluate the trends in the incidence, clinical course and outcome of respiratory distress syndrome (RDS) in the newborn in the Oulu University Hospital region in northern Finland. METHODS: In the population of 58 990 infants, the incidence rates of RDS specific to gestational age and birthweight in two consecutive periods, 1990-95 and 1996-99, were calculated. Clinical course and other neonatal morbidities were reported. All surviving infants were followed up until 1 y of corrected age. RESULTS: The overall incidence of RDS did not change significantly (8.7/1000 livebirths in 1990-95 vs 7.6 in 1996-99; p = 0.15), but the gestational age-adjusted incidence decreased between the two consecutive periods (p = 0.005). The frequency of infants with gestational age below 28 wk tended to increase towards the late 1990s, while their RDS incidence remained unchanged. RDS-related neonatal mortality decreased in parallel with neonatal mortality, accounting for 15% of all neonatal deaths. The duration of oxygen therapy shortened (8.0 vs 5.5 d) and the incidence of pneumothorax decreased (9.7 vs 4.1%), whereas the rate of chronic lung disease at 36 wk of postconceptional age (16.4 vs 16.7%) and at 1 y of corrected age (9.2 vs 8.2%) remained unchanged, as did also associated neurosensory morbidity (8.8 vs 9.5%). CONCLUSION: During the 1990s, the incidence of RDS shifted towards more immature infants and the gestational-age specific incidence decreased. The course of the disease shortened and acute complications decreased. The frequency of chronic pulmonary sequelae (and associated neurosensory morbidity) at the age of 1 y did not change significantly.

Nitric oxide treatment and acute pulmonary inflammatory response in very premature infants with intractable respiratory failure shortly after birth.

AIM: Premature infants with respiratory failure and early-onset pneumonia have low inducible nitric oxide synthase (NOS2) and no evidence of nitric oxide (NO) toxicity. However, inhalation of NO may not be indicated in sepsis because excessive NO generation has been reported. This prospective study was designed to test the hypothesis that inhaled NO is effective in a select group of small premature infants and that the responsiveness to NO is associated with low NOS2 enzyme. METHODS: 246 very low birthweight infants (birthweight <1500 g, VLBW) were screened for severe, intractable respiratory failure (oxygenation index >40, arterial-alveolar ratio for oxygen tension <0.10) that does not respond to two doses of surfactant within 5 h from birth. Infants with severe cardiac failure or a bleeding disorder were excluded. Five of the nine eligible cases received inhaled NO. They all had prolonged rupture of foetal membranes, early-onset pneumonia and persistent pulmonary hypertension. RESULTS: All five responded strikingly, survived and appeared normal in follow-up. Airway specimens during the first day of life revealed very low NOS2, interleukin-1beta and surfactant protein A, compared with VLBW infants who had no acute infection despite histological chorioamnionitis. In early-onset pneumonia, NOS2 and other inflammatory mediators increased first during the recovery 1-2 d after birth. CONCLUSION: VLBW infants with progressive respiratory failure and infection at birth have deficient pulmonary NOS2 and cytokine response. After surfactant therapy, these infants responded strikingly to inhaled NO. An acute pulmonary inflammatory response may contribute to respiratory adaptation in early-onset pneumonia.

A national two year follow up study of extremely low birthweight infants born in 1996-1997.

OBJECTIVE: To study neurodevelopmental outcome in a two year cohort of extremely low birthweight (ELBW) infants at 18 months corrected age, to compare the development of the ELBW infant subcohort with that of control children, and to find risk factors associated with unfavourable outcome. STUDY DESIGN: All 211 surviving ELBW infants (birth weight < 1000 g) born in Finland in 1996-1997 were included in a national survey. The ELBW infants (n = 78) who were born and followed in Helsinki University Hospital belonged to a regional subcohort and were compared with a control group of 75 full term infants. A national follow up programme included neurological, speech, vision, and hearing assessments at 18 months of corrected age. Bayley infant scale assessment was performed on the subcohort and their controls at 24 months of age. Risk factors for unfavourable outcome were estimated using logistic and linear regression models. RESULTS: The prevalence of cerebral palsy was 11%, of all motor impairments 24%, of ophthalmic abnormalities 23%, and of speech delay 42%. No impairment was found in 42% of children, and 18% were classified as severely impaired. The prevalence of ophthalmic abnormalities decreased with increasing birth weight and gestational age, but the prevalence of other impairments did not. In the subcohort, a positive correlation was found between the date of birth and Bayley scores. CONCLUSION: Ophthalmic abnormalities decreased with increasing birth weight and gestational age, but no other outcome differences were found between birthweight groups or in surviving ELBW infants born at 22-26 weeks gestation. The prognosis in the regional subcohort seemed to improve during the short study period, but this needs to be confirmed.

Exhaled and nasal nitric oxide in mechanically ventilated preterm and term newborns.

AIM: Nitric oxide (NO) is an important mediator required for neonatal pulmonary circulatory adaptation and for pulmonary defence. Both deficient and excessive NO production have been proposed to play a role in neonatal lung disease. This study aimed to establish a method that allows direct measurement of exhaled and nasal NO concentrations in newborn infants who require intubation and ventilation. METHODS: A rapid-response chemiluminescence NO analyser was used. Gas was sampled from the endotracheal intubation tube, and tidal volumes and flow rates were measured. The nasal NO was sampled from the non-intubated nostril. The accuracy of the method was validated using a lung model. NO levels from six preterm and six term/near-term newborns were studied. Measurements were performed on a daily basis during the first week. RESULTS: An expiration >0.2 s in duration with a flow rate >1.7 ml s(-1) could be accurately analysed for the presence of >1 parts per billion of NO. The very preterm infants with neonatal lung disease had a different postnatal NO output pattern from the lower and upper airways compared with the ventilated term/near-term infants. CONCLUSION: A novel method for measurement of exhaled NO of an intubated newborn is presented. The possible association of exhaled NO concentration with the development of chronic lung disease remains to be studied.

A national short-term follow-Up study of extremely low birth weight infants born in Finland in 1996-1997.

OBJECTIVES: The aims of this prospective nationwide investigation were to establish the birth rate, mortality, and morbidity of extremely low birth weight (ELBW) infants in Finland in 1996-1997, and to analyze risk factors associated with poor outcome. PARTICIPANTS AND METHODS: The study population included all stillborn and live-born ELBW infants (birth weight: <1000 g; gestational age: at least 22 gestational weeks [GWs]), born in Finland between January 1, 1996 and December 31, 1997. Surviving infants were followed until discharge or to the age corresponding with 40 GWs. National ELBW infant register data with 101 prenatal and postnatal variables were used to calculate the mortality and morbidity rates. A total of 32 variables were included in risk factor analysis. The risk factors for death and intraventricular hemorrhage (IVH) of the live-born infants as well as for retinopathy of prematurity (ROP) and oxygen dependency of the surviving infants were analyzed using logistic regression models. RESULTS: A total of 529 ELBW infants (.4% of all newborn infants) were born during the 2-year study. The perinatal mortality of ELBW infants was 55% and accounted for 39% of all perinatal deaths. Of all ELBW infants, 34% were stillborn, 21% died on days 0 through 6, and 3% on days 7 though 28. Neonatal mortality was 38% and postneonatal mortality was 2%. Of the infants who were alive at the age of 4 days, 88% survived. In infants surviving >12 hours, the overall incidence of respiratory distress syndrome (RDS) was 76%; of blood culture-positive septicemia, 22%; of IVH grades II through IV, 20%; and of necrotizing enterocolitis (NEC) with bowel perforation, 9%. The rate of IVH grades II through IV and NEC with bowel perforation decreased with increasing gestational age, but the incidence of RDS did not differ significantly between GWs 24 to 29. A total of 5 infants (2%) needed a shunt operation because of posthemorrhagic ventricular dilatation. Two hundred eleven ELBW infants (40% of all and 60% of live-born infants) survived until discharge or to the age corresponding with 40 GWs. The oxygen dependency rate at the age corresponding to 36 GWs was 39%, and 9% had ROP stage III-V. Neurological status was considered completely normal in 74% of the surviving infants. The proportions of infants born at 22 to 23, 24 to 25, 26 to 27, and 28 to 29 GWs with at least one disability (ROP, oxygen dependency, or abnormal neurological status) at the age corresponding to 36 GWs were 100%, 62%, 51%, and 45%, respectively. Birth weight <600 g and gestational age <25 GWs were the independent risks for death and short-term disability. The primary risk factor for IVH grades II through IV was RDS. Low 5-minute Apgar scores predicted poor prognosis, ie, death or IVH, and antenatal steroid treatment to mothers with threatening premature labor seemed to protect infants against these. Some differences were found in the mortality rates between the 5 university hospital districts: neonatal mortality was significantly lower (25% vs 44%) in one university hospital area and notably higher (53% vs 34%) in another area. Furthermore, significant differences were also found in morbidity, ie, oxygen dependency and ROP rates. Differences in perinatal (79% vs 45%) and neonatal (59% vs 32%) mortality rates were found between secondary and tertiary level hospitals. CONCLUSION: Our study shows that even with modern perinatal technology and care, intrauterine and early deaths of ELBW infants are common. The outcome of infants born at 22 to 23 GWs was unfavorable, but the prognosis improved rapidly with increasing maturity. The clear regional and hospital level differences detected in survival rates and in short-term outcome of ELBW infants emphasizes that the mortality and morbidity rates should be continuously followed and that differences should be evaluated in perinatal audit procedures. (ABSTRACT TRUNCATED)

Randomized trial comparing natural and synthetic surfactant: increased infection rate after natural surfactant?

The efficacy of a natural porcine surfactant and a synthetic surfactant were compared in a randomized trial. In three neonatal intensive care units, 228 neonates with respiratory distress and a ratio of arterial to alveolar partial pressure of oxygen <0.22 were randomly assigned to receive either Curosurf 100 mgkg-1 or Exosurf Neonatal 5 ml.kg-1. After Curosurf, the fraction of inspired oxygen was lower from 15 min (0.45 +/- 0.22 vs 0.70 +/- 0.22, p = 0.0001) to 6 h (0.48 +/- 0.26 vs 0.64 +/- 0.23, p = 0.0001) and the mean airway pressure was lower at 1 h (8.3 +/- 3.2 mm H20 vs 9.4 +/- 3.1 mm H20, p = 0.01). Thereafter the respiratory parameters were similar. The duration of mechanical ventilation (median 6 vs 5 d) and the duration of oxygen supplementation (median 5 vs 4 d) were similar for Curosurf and Exosurf. After Curosurf, C-reactive protein value over 40 mg l-1 occurred in 45% (vs 12%; RR 3.62, 95%CI 2.12-6.17, p = 0.001), leukopenia in 52% (vs 28%; RR 1.85, 95% CI 1.31-2.61, p = 0.001) and bacteraemia in 11% (vs 4%; RR 3.17, 95% CI 1.05-9.52, p < 0.05). We conclude that when given as rescue therapy Curosurf had no advantage compared with Exosurf in addition to the more effective initial response. Curosurf may increase the risk of infection.

Diminished inducible nitric oxide synthase expression in fulminant early-onset neonatal pneumonia.

OBJECTIVE: Fulminant early-onset neonatal pneumonia is associated with ascending intrauterine infection (IUI), prematurity, persistent pulmonary hypertension (PPHN), and septicemia. Nitric oxide (NO) as an inflammatory mediator is included in antimicrobial defense and has a role in pathogenesis of septic shock. The aim was to study the role of inflammatory NO in neonatal pneumonia. METHODS: Lungs from 36 autopsies were studied: 12 had fulminant early-onset neonatal pneumonia, 5 pneumonia of later onset, and 19 controls had similar gestational and postnatal age. In addition, airway specimens from 21 intubated newborns were analyzed: 7 with fulminant early-onset pneumonia, 7 apparently noninfected infants born prematurely attributable to IUI, and 7 premature infants of similar gestation. Specimens were analyzed for inducible NO synthase (NOS2) and nitrotyrosine, an indicator of NO toxicity. The degree of staining was analyzed. RESULTS: In fulminant pneumonia, alveolar macrophages (AM) showed significantly less NOS2 immunoactivity than the controls. In the airway specimens, the infants with fulminant pneumonia 0 to 2 days after birth had significantly lower intracellular NOS2 and nitrotyrosine and significantly lower interleukin-1beta and surfactant protein-A than apparently noninfected IUI infants. NOS2 and the other indices increased significantly during the recovery. CONCLUSIONS: For the first time, we report NOS2 expression by macrophages from human neonates. In fulminant early-onset neonatal pneumonia, delayed production rather than excess of pulmonary inflammatory NO is associated with severe symptoms.

Short versus prolonged indomethacin therapy for patent ductus arteriosus in preterm infants.

OBJECTIVE: To evaluate whether a prolonged low-dose course of indomethacin would produce an improved closure rate and have fewer side effects compared with a short standard dosage schedule in the management of patent ductus arteriosus (PDA) in preterm infants. STUDY DESIGN: Sixty-one infants of gestational ages 24 to 32 weeks with a PDA confirmed with echocardiography were randomized to receive 0.2 to 0.1 to 0.1 mg/kg indomethacin in 24 hours (short course, n = 31) or 0.1 mg/kg every 24 hours 7 times (long course, n = 30). Echocardiography was done 3, 9, and 14 days after the treatment was started, and side effects were monitored. RESULTS: Primary PDA closure occurred more often in the short course group (94% vs 67%, P =.011), but the sustained closure rates were not different (74% vs 60%). Surgical PDA ligations were less frequent in the short course group than in the long course group. The short course group had a shorter duration of oxygen supplementation, less frequent symptoms of necrotizing enterocolitis, and a lower rate of urea retention. Mortality and other neonatal morbidity rates were similar. CONCLUSION: A prolonged low-dosage indomethacin regimen offers no advantage compared with a standard-dosage short course in the management of a hemodynamically significant PDA in preterm infants.

Overdoses of pethidine given to two preterm neonates.

This paper reports two mechanically ventilated preterm babies who received overdoses of pethidine in the neonatal period. One of the neonates (gestational age 26 weeks, birthweight 1040 g) received repeated appropriate doses, which resulted in central nervous system irritability and convulsion due to accumulation of the drug and its metabolite, norpethidine. The other neonate (gestational age 27 weeks, birthweight 980 g) received a major (10-fold) overdose with little clinical effect. These two cases indicate notable individual variability in the responses of babies to pethidine. This is typical of other opioids, too. Therefore, the dosing of opioids to neonates should be titrated individually, and the patients should be observed carefully.

Pain relief can reduce hypoxemia in distressed neonates during routine treatment procedures.

OBJECTIVE: To determine whether the use of opioids could reduce the hypoxemia and hemodynamic instability associated with routine intensive care procedures in neonates with respiratory distress. DESIGN: Randomized and placebo-controlled study. METHODS: Physiological, plasma beta-endorphin, cortisol, and glucose responses to routine treatment procedures were studied in 84 mechanically ventilated distressed neonates randomized into groups receiving 1 mg/kg meperidine or 0.9% saline 15 minutes before tracheal suction or routine nursing care. RESULTS: The duration of hypoxemia (transcutaneous partial pressure of O2 < 6.6 kPa (< 50 mm Hg) and/or arterial blood oxygen saturation < 80%) during treatment procedures was significantly longer in the saline group (mean 82 vs 36 seconds, P = .001) and distress quantified by a novel behavioral scoring method was much higher. Changes in arterial blood pressure, heart rate, or plasma beta-endorphin, cortisol, and glucose concentration did not show any statistically significant differences between the groups. CONCLUSION: Newborns with respiratory difficulties often suffer from hypoxemia during essential treatment procedures. The use of opioid analgesia may reduce the duration of hypoxemia and the associated distress and, therefore, may improve the long-term results of neonatal intensive care.

Physiological changes, plasma beta-endorphin and cortisol responses to tracheal intubation in neonates.

Physiological, plasma beta-endorphin and cortisol responses to nasotracheal intubation were studied in 20 distressed infants of median age 0.3 days (range 0.1-23 days) randomized into groups given pethidine 1 mg/kg (n = 10) or alfentanil 20 micrograms/kg plus suxamethonium 1.5 mg/kg (n = 10) before intubation. All of the infants were given glycopyrrolate 3-5 micrograms/kg. Hypoxaemia during intubation was found in all 10 infants in the pethidine group and in 7 of 10 infants in the alfentanil-suxamethonium group, its duration being significantly longer in the pethidine group and being associated with the duration of the intubation procedure. Blood pressure increased, but not statistically significantly, in all except 2 patients in the alfentanil-suxamethonium group and bradycardia appeared in 1 patient in each group. Plasma beta-endorphin and cortisol values did not show any statistically significant intra-group or inter-group differences. Newborn infants suffer from hypoxaemia during intubation when awake more and therefore need adequate premedication before elective intubation. One alternative is the combination of glycopyrrolate, alfentanil and suxamethonium described here, although the ideal medication and dosage still remain to be defined.

Effect of opioid-induced analgesia on beta-endorphin, cortisol and glucose responses in neonates with cardiorespiratory problems.

The effects of analgesia on plasma beta-endorphin (beta-E), serum cortisol and blood glucose responses were investigated in 20 distressed, mechanically ventilated neonates during the first 3 days of life. Morphine 0.1 mg/kg, meperidine 1 mg/kg or alfentanil 10 micrograms/kg were used for analgesia as clinically indicated. Plasma beta-E, serum cortisol and blood glucose were recorded before analgesia and 1 and/or 2, 12 and 24 h afterwards in the distress group and once in 20 healthy neonates (control group). beta-E, cortisol, and blood glucose before analgesia were significantly higher in the distress group than in the control group. Cortisol values had decreased significantly 2 h after analgesia and blood glucose within 12 h. Plasma beta-E values had decreased to the same level as in the controls 24 h after the start of analgesia. The results indicate that the stress response in the distressed neonates with cardiorespiratory problems, as assessed by beta-E, cortisol, and blood glucose, is attenuated by opioid medication, and it is concluded that these patients should be given adequate analgesia.

Age-related morphine kinetics in infants.

The pharmacokinetics of morphine was studied in 27 infants receiving a single intravenous dose of 0.1 mg/kg morphine after surgery (n = 23) or during mechanical ventilation (n = 4). The pharmacokinetics of morphine varied greatly between the subjects, especially in the neonates. The clearance and half-life varied distinctly with postnatal age. The mean (+/- SD) half-life was 8.1 +/- 8.1 h in 10 neonates younger than 1 week, 5.4 +/- 3.4 h in 10 infants aged from 1 week to 2 months and 2.6 +/- 1.7 h in 7 infants aged from 2 to 6 months. Mean clearance increased significantly with age, being 8.7 +/- 5.8 ml/min/kg in the youngest age group, 11.9 +/- 5.1 ml/min/kg in those aged 1 week to 2 months and 28.0 +/- 8.9 ml/min/kg in those aged 2-6 months, and was also significantly lower in the critically ill infants. The clearance and half-life of morphine begin to approach adult values after the age of 1 month, but great individual variability exists even after that. In order to reduce the risk of overdosing or underdosing, the dose of morphine should be titrated individually.

Pharmacokinetics and pharmacodynamics of intravenous meperidine in neonates and infants.

The pharmacokinetics of meperidine (pethidine) was studied in 21 infants who received a single intravenous dose of 1 mg/kg after surgery (n = 18) or during mechanical ventilation because of respiratory distress (n = 3). Eleven patients were younger than 1 week old, 10 patients were aged from 3 weeks to 5 months, and five of the patients were premature. The pharmacokinetics of meperidine varied greatly between the subjects, with a median elimination half-life of 10.7 hours (range, 3.3 to 59.4 hours), median clearance of 8.0 ml/kg/min (range, 1.8 to 34.9 ml/kg/min), median volume of the central compartment of 2.4 L/kg (range, 0.5 to 4.8 L/kg), and median steady-state volume of distribution 7.2 L/kg (range, 3.3 to 11.0). The great interindividual variability in meperidine pharmacokinetics should be taken into consideration when meperidine is administered to neonates. Although no life-threatening or serious side effects were observed in this study, appropriate care should be exercised when prescribing meperidine for this age group.

Alfentanil-induced rigidity in newborn infants.

The authors evaluated whether alfentanil could be given before treatment procedures in critically ill mechanically ventilated neonates without adverse effects. Alfentanil (mean dose 11.7 micrograms/kg, range 9-15) was given intravenously to 20 mechanically ventilated critically ill newborn infants (mean birth weight 2510 g, range 1490-3990) during the first 3 days of life before treatment procedures. Heart rate, arterial blood pressure, transcutaneous partial pressure of O2, respiratory rate, and general activity were observed continuously from 10 min before the administration of alfentanil until 1 h after it. Plasma alfentanil concentrations were measured in 15 subjects. The pharmacokinetics of alfentanil varied greatly among the subjects. The hemodynamic changes were not clinically significant, and the most important side effect was muscle rigidity. Nine infants had mild or moderate rigidity, which had little or no effect on ventilation. Four infants had severe rigidity and jerking comparable to convulsive activity, transiently impairing ventilation and oxygenation for approximately 5-10 min. Increased inspired oxygen and increased pressure by manual ventilation were needed to prevent hypoxemia. Electroencephalographic recordings for three infants during alfentanil administration showed no evidence of increased seizure activity. We conclude that alfentanil should not be used for newborn infants without simultaneous muscle relaxation because of the danger of rigidity.