Christian F. Poets

Arterial oxygen saturation in healthy term neonates

Our objective was to determine arterial oxygen saturation as measured by pulse oximetry (SpO2) in healthy term neonates during their first 4 weeks of life. Overnight recordings of SpO2 (Nellcor N200), photoplethysmographic (pulse) wave-forms from the oximeter and breathing movements were performed in 60 term infants. They were studied initially during their 1st week of life (median age 4 days, range 1–7) and then again during their 2nd–4th week (median age 17 days, range 8–27). Median baseline SpO2, measured during regular breathing, was 97.6% (range 92–100) during week 1 versus 98.0% (86.6–100) during week 2–4 (P>0.05). Episodes of desaturation, defined as a fall in SpO2 to ≤80% for ≥4 s, were found in 35% of recordings obtained in week 1 compared to 60% of those obtained in week 2–4 (P<0.01). Their frequency increased from a median of 0 (0–41) per 12 h of recording at the initial recording to 1 (0–165) at follow up (P<0.01). Analysis of the data by week of life showed a peak in desaturation frequency in the 2nd week of life. The infants with extreme values at follow-up (e.g. a baseline SpO2 of 86.6%, 5th percentile 91.9%, or a desaturation frequency of 165 per 12 h of recording, 95th percentile 32) had had values well within the normal range during their initial recording (a baseline SpO2 of 94.4%, or a desaturation frequency of 4). Most of the desaturations in the infants with extreme values were associated with periodic apnoea. These results demonstrate only relatively minor developmental changes in oxygenation in term neonates during the first 4 weeks of life. The clinical significance of outlying values, i.e. a low baseline SpO2 or a high number of episodic desaturations, remains to be determined.ConclusionThese healthy term neonates had values for baseline oxygen saturation and desaturation frequency that were not substantially different from those observed in older infants.

Early feeding after necrotizing enterocolitis in preterm infants

OBJECTIVE To report our experience with an early initiation of enteral feedings after necrotizing enterocolitis (NEC). STUDY DESIGN Over a 4-year period, all inborn infants with NEC Bell stage II or greater received enteral feedings, increased by 20 mL/kg/d, once no portal vein gas had been detected on ultrasound for 3 consecutive days (group 1). Infants were compared with a historic comparison group (group 2). RESULTS Necrotizing enterocolitis rates were 5% (26/523) in the early feeding group and 4% (18/436) in the comparison group. One early feeding infant and two comparison group infants died of NEC, whereas two and one, respectively, had recurrent NEC. Enteral feedings were restarted at a median of 4 days (range, 3-14) versus 10 days (range, 8-22) after onset of NEC. Early feeding was associated with shorter time to reach full enteral feedings (10 days [range, 7-31] vs 19 days [range, 9-76], P<.001), a reduced duration of central venous access (13.5 days [range, 8-24] vs 26.0 days [range, 8-39], P<.01), less catheter-related septicemia (18% vs 29%, P<.01), and a shorter duration of hospital stay (63 days [range, 28-133] vs 69 days [range, 36-150], P<.05). CONCLUSION Early enteral feeding after NEC was associated with significant benefits and no apparent adverse effects. This study was underpowered, however, to exclude a higher NEC recurrence risk potentially associated with this change in practice.

Effects of bottle feeding and two different methods of gavage feeding on oxygenation and breathing patterns in preterm infants

Objective To determine the effect of bottle feeding, as compared to two methods of gavage feeding, on apnoea, bradycardia and oxygen desaturation frequency. Patients: Thirty preterm infants breathing room air; gestational age 28.6 ± 2.1 weeks at birth and 34 ± 1.4 weeks at study (mean ± SD). Methods: Nine‐hour recordings of pulse oximeter saturation (SpO2), pulse waveforms, electrocardiogram, breathing movements and nasal airflow. Administration of 21 ± 1.5 ml/kg of milk/feed in 3‐h intervals using three different feeding techniques in random order: bottle feeding, bolus gavage feeding, and slow gavage feeding (1 h). Analysis of recordings for apnoeas (≥4 s, bradycardias (heart rate < 2/3 of baseline), and episodic desaturation (SpO2≤ 80%). Results: There were three times more desaturations with bottle feeding than with bolus gavage feeding (p < 0.001), but no further reduction with slow gavage feeding. With all three feeding techniques, there were significantly more desaturations in the hour when the feeds were given than during the following 2 h. The deleterious effects of bottle feeding were most evident during the hour of feeding, but desaturation frequency remained significantly higher than with gavage feeding during the following 2h. There was no significant effect of feeding technique on the frequency of apnoea or bradycardia. Conclusions: Preterm infants who are normally oxygenated in room air may have significant desaturation during bottle feeding. Such desaturation can be effectively reduced by gavage feeding. Slow gavage feeding offers no advantage over bolus gavage feeding with respect to the avoidance of hypoxaemia.

Effects of salbutamol delivery from a metered dose inhaler versus jet nebulizer on dynamic lung mechanics in very preterm infants with chronic lung disease

Treatment of chronic lung disease of prematurity requires effective aerosol delivery of different therapeutic agents. Aerosols can be generated by a metered dose inhaler (MDI) or a jet nebulizer. An MDI combined with a spacer device is easier to use and avoids undesirable effects noted in conjunction with jet nebulization. We compared the clinical effectiveness of 200 μg (2 puffs) salbutamol delivered from an MDI in conjunction with a valved spacer device (Aerochamber®), and 600 μg given via jet nebulizer (PariBaby®) on 2 consecutive days, the order being randomized. Thirteen spontaneously breathing very preterm infants [mean (SD) gestational age 27.2 (1.8) weeks; birth weight 0.90 (0.34) kg] were studied at a corrected age of 37 (2.3) weeks. Mean (SD) study weight was 1.83 (0.38) kg. Dynamic lung compliance and resistance were determined from measurements of flows, volumes, and transpulmonary pressures, using a pneumotachometer and a small esophageal microtransducer catheter before and 20 min after salbutamol application.

Effect of Doxapram on Episodes of Apnoea, Bradycardia and Hypoxaemia in Preterm Infants

Aim: To study the effect of doxapram on the frequency of apnoea, bradycardia and hypoxaemia. Methods: Fifteen infants, median gestational age at birth 27 weeks (range 24–30), age at study 27 days (12–60), with ≥6 episodes of bradycardia or hypoxaemia/6 h despite serum caffeine levels in the therapeutic range, received doxapram either intravenously (0.5–2 mg/kg/h) or orally (2–8 mg/kg every 2 h). Six-hour recordings of pulse oximeter saturation (SPO2), pulse waveforms, ECG, breathing movements and nasal airflow were performed immediately before as well as 1, 3 and 6 days after onset of treatment. Recordings were analysed for apnoea (≥4 s), bradycardia (heart rate < 2/3 of baseline) and hypoxaemia (SPO2 ≤80%). Results: There was no difference between enteral and intravenous administration; results are therefore presented for the total group. Doxapram resulted in a significant decrease in the frequency of apnoea [22 (11–27) vs. 14 (7–23)/h, p < 0.01], bradycardia [3 (0–7) vs. 1 (0–3)/h, p < 0.01] and hypoxaemia [8 (0–18) vs. 2 (0– 17)/h, p < 0.01] already after 1 day of treatment, which was sustained throughout the 6-day study period. Side effects included an increase in the proportion of time spent awake [5 (0–24) vs. 12% (3–28), p < 0.01] and in gastric residuals [0% of feeding volume (0–5) vs. 4% (0–19), p < 0.05]. Enteral was switched to intravenous doxapram in 3 of 9 infants because of gastrointestinal side effects. Conclusion: Doxapram substantially reduced the frequency of apnoea, bradycardia and hypoxaemia in these patients with caffeine-resistant apnoea of prematurity. Enteral administration, however, was not tolerated in a significant proportion (33%) of infants.

Sudden infant death and maternal cigarette smoking : results from the Lower Saxony Perinatal Working Group

Maternal smoking has long been identified as a risk factor for sudden infant death (SID). However, only few studies analysed the biological plausibility of the relationship between maternal smoking and SID. In Lower Saxony (North Germany), detailed information concerning the perinatal period is routinely obtained for almost all infants born in this region. The perinatal data sets from 190 SID cases who had died between 1986 and 1990 and in whom a full autopsy had been performed were identified and compared to data sets from 5920 random controls, frequency matched to cases on year of birth. After adjusting for potential confounders (socio-economic status, birth weight, maternal age and nationality), smoking during pregnancy was still associated with a significantly increased risk of SID (odds ratio (OR) 2.7, 95% confidence interval (CI) 1.7–4.5). There was a clear dose-effect relationship between the number of cigarettes smoked and the risk of SID: adjusted ORs were 2.6 (1.5–4.4) for 1–10 cigarettes/day, 2.8 (1.8–6.0) for 11–20 cigarettes/day, and 6.9 (1.9–25.5) for >20 cigarettes/day. There also appeared to be an interaction between smoking during pregnancy and maternal anaemia: the risk of SID almost doubled if mothers not only smoked, but were also anaemic (haemoglobin <100 g/l). These results support the concept that smoking during pregnancy has direct biological effects on the fetus which are associated with an increased risk of SID later in life. The exact mechanism(s) whereby smoking increases the risk of SID, however, remains to be determined. The detrimental effects of smoking on SID should be strongly addressed in any national or local campaign aiming to reduce the incidence of SID in a community.ConclusionMaternal smoking during pregnancy is an important modifiable risk factor for SID.

Arterial oxygen saturation in infants at risk of sudden death: influence of sleeping position

To study the possible influence of sleeping position on arterial oxygen saturation, measured by pulse oximetry (Sp62), 7–h overnight recordings of breathing movements and ECG were performed in 43 infants (median age 2.4 months, range 0.2–11 months) at increased risk of sudden infant death syndrome (SIDS). Infants were randomly allocated to start sleeping either in their usual sleeping position or in the opposite position. After 3.5 h, all infants were gently turned over. Thus, each infant served as their own control. Recordings were analysed for sleep time, baseline Sp02 (only during regular breathing), and the number and duration of desaturations (a decrease in Sp02 to ≤80%). In the prone position, a significantly higher proportion of time was spent asleep (median 79% versus 70%;p < 0.05). Median baseline Sp02 was 98.8% (91.7–100%) in the prone and 99.0% (92.0–100%) in the supine position (ns). A total of 191 desaturations were found in 29 recordings; 96 in the prone and 95 in the supine position (ns). One infant subsequently died of SIDS while sleeping in the prone position. He had a relatively high number of desaturations (n = 12) which all occurred in the prone position. These results confirm earlier studies which could not find a significant influence of sleeping position on baseline oxygenation. The occurrence of desaturations in the prone position only in the infant who subsequently died requires further investigation.

False alarms in very low birthweight infants: comparison between three intensive care monitoring systems

Monitor alarms are a major burden on both patients and staff in intensive care units. We compared alarm rates from three different monitor systems (Hewlett Packard (HP), Kontron Instruments (KI), Marquette‐Hellige (MH)) in a tertiary neonatal intensive care unit. Monitors were used in random order on three consecutive days over 8h each in 16 preterm infants (median gestational age at birth 29 wk (range 24‐34), age at study 18 d (8‐53), weight at study 1160g (595‐1430)). Alarms were classified as true or false using flow sheets based on continuous observation of both the patient and related parameters. There was one alarm every 9 min of monitoring. The median number of true alarms did not differ significantly between systems, being 28 per 8 h (range 9‐87) for HP, 26 (3‐81) for KI, and 30 (5‐135) for MH. The median number of false alarms differed widely, with the HP system generating 32 (7‐77) such alarms per 8 h, compared to 8 (0‐19) for KI and 15 (2‐32) for MH (p < 0.01 HP vs KI and MH, p lt; 0.05 KI vs MH). These differences between systems were mainly due to differences in pulse oximeter and transcutaneous PO2 monitor alarm rates.

The importance of static lung inflation during organ storage: The impact of varying ischemic intervals in a double lung rat transplantation model

To determine the importance of static lung inflation during storage, graft performance was evaluated at different levels of intratracheal pressure and varying ischemic intervals. Lewis rat lungs were perfused with low-potassium Euro-Collins and stored for 4 or 8 hr either in atelectasis (4 hr: group I; 8 hr: group IV, respectively) or 13 (group II; V) or 26 cmH2O of airway pressure (groups III, VI). Following implantation continuous measurement of alveolar-arterial oxygen difference (AaDO2*) and pulmonary vascular resistance (PVR) were performed. Separate ventilation allowed assessment of mechanical lung function of the graft. At the end of reperfusion (120 min) weight gain, histology, and phospholipid and protein content in the pulmonary lavage were compared between the groups. Despite significant differences in survival at 4 hr of ischemia graft function did not differ in groups I to III. In contrast, static inflation had a significant impact after 8 hr of ischemia. Lungs stored in atelectasis (group IV) could not be reperfused and failed immediately. Survival in group V was 83+/-11 versus 107+/-7 min in group VI (P<0.05). Compliance at 80 min was 27+/-3 in group V and 52+/-6 ml/cmH2O in group VI (P<0.02). Corresponding values for PVR were 232+/-92 and 112+/-16 mmHg/ml/min, respectively (P<0.05). Less inflation and longer ischemia resulted in a reduction of the large to small phospholipid aggregate ratio and deterioration of surfactant function in the bubble surfactometer. In conclusion, while the amount of static lung inflation may not be critical following short ischemia, the performance of the graft improves significantly with full inflation (26 cmH2O) following extended ischemia (8 hr).

Active surfactant in pharyngeal aspirates of term neonates: lipid biochemistry and surface tension function

Alveolar surfactant is well known for its ability to reduce minimal surface tension at the alveolar air–liquid interface to values below 5 mN m−1. In addition, it has been suggested that surfactant is also present in the airways, particularly in the perinatal period. We isolated surfactant from pharyngeal aspirates obtained from 33 neonates immediately after delivery and analysed it for both phospholipid (PL) composition and surface tension function. PL classes and phosphatidylcholine (PC) molecular species were determined by normal and reversed‐phase high‐performance liquid chromatography (HPLC), respectively. Static and dynamic surface properties of the surfactant were studied in a pulsating bubble surfactometer. Sample volume was 1.3 ± 0.5 mL (mean ± SD) with a total amount of 2.5 ± 1.3 μmol of PL and a concentration of 2.1 ± 1.0 μmol mL−1 PL. HPLC analyses of PL classes revealed a composition identical with surfactant prepared from alveolar washes, i.e. PC 83.6 ± 2.1%, sphingomyelin 1.4 ± 0.5%, phosphatidylglycerol 8.1 ± 1.6%, phosphatidylethanolamine 2.1 ± 0.5% and phosphatidylinositol 2.6 ± 1.1%. Thin‐layer chromatography showed almost identical results but was more time‐consuming and needed more material for analysis. Analysis of PC molecular species revealed a composition typical of human alveolar surfactant with 54.7 ± 3.9% dipalmitoyl PC, 10.3 ± 1.9% palmitoyloleoyl PC and 9.1 ± 1.5% palmitoylmyristoyl PC. Minimal surface tension fell to values below 5 mN m−1 within 5 min of cycling in all subjects. The methods used in this study allowed for complete PL and surface tension analyses of surfactant obtained during routine pharyngeal suctioning after delivery at term. Whether they are also applicable to preterm neonates with respiratory distress remains to be determined.